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Web site last updated 15 November 2018
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Hi, all of your rocketry and jet-engine fans! The below document was first “defensively published” on 24 June 2012. The purpose of this web site is to conduct “public domain rocket science”… I want to help develop new ideas in the domains of rocket and jet propulsion. AND I want to fend off the patent lawyers and patent trolls! Humans need to go out and start seriously exploring the solar system, for starters. Patent trolls are not going to help us… So… Dear Reader… Can you help develop these ideas? Email me your ideas (including critiques of the below), tell me if you want credit (or to remain anonymous), and I will “defensively publish” your ideas also! If they are related to the primary targets of this web site, GREAT! If you have totally un-related ideas that you would like to defensively publish… Then I will be happy to post a link to your web site. Or, if I find your ideas fascinating (but un-related to jet and rocket propulsion), and you have no web site, send me your ideas, and I can create sub-directories to this web site, for you. We who oppose “patent trolls” must all stick together! Email me!
Declaration of Legal Intent
I, Titus “Rocket Slinger” Stauffer, publish this with the express intent of making all ideas contained here, that haven’t yet been patented, available in the “public domain”, to prevent anyone else from patenting them. The below is “defensively published” in the name of the promoting the art and science of rocketry and the engineering of rocketry systems, in a lower-cost manner. Excessive fighting over patents and patent laws is not productive, and so here is my attempt to combat this waste of effort. I have not stolen any secrets or trade secrets from my employer (who is not at all in the rocketry business), or from anyone else. I wish that no one apply for patents on any new, unpublished, or unpatented ideas contained here.
A Proposed Method of Using Vertical-Rail-Mounted Jets for “Sling-Shot” Initial-Phase Launch Assistance for Rockets
Titus “Rocket-Slinger” Stauffer, 24 June 2012 (Now being updated from time to time)
This is an only-moderately-formal document written by an electrical engineer who is not formally schooled in rocket science. Accordingly, the mathematics are kept to the minimal essentials, and details are not provided in many categories. What is included here though, is a scheme of several elements for assisting a rocket through the first approximately 1,200 feet of vertical launch. Four 1,200-foot towers are arranged radially around the rocket and it’s (conventional) gantry tower. On the face of each tower (facing the rocket) is a large vertical rail. Inside the rail, there are solenoids that open up, sequentially (vertically time staggered) opening up so as to release pressurized JP4 (jet fuel), air, and water, in pulses that are received by an ascending jet-propelled Jet / Elevator / Train (“JET” for short) assembly. The JETs climb the 4 faces of the 4 towers, powered by 2 jet engines each. Since they are fed JP4 during their brief upward journey, they need NOT carry all their own fuel, and so they have a high thrust-to-weight ratio. From the JETs, downwards towards the rocket (at a 45 degree angle or so), strong tow cables are attached. Attached to the cables, are also 2 hoses (or sets of hoses), one carrying air and pressurized water, and one carrying JP4. These hoses and cables meet a “cradle” assembly that supports the entire rocket assembly (the rocket sits, cup in saucer style, in the cradle, with minimal attachments between the cradle and the rocket). The cables exert upward force upon the cradle (and hence also to the rocket) during the first, critical 1,200 feet of launch, where most rocket nozzles are “grossly over-expanded” at initial launch, which is a problem that the cradle assembly also solves. “Over-expanded” v/s “under-expanded” is briefly explained here, along with how the cradle assembly solves this problem, for the first phase of launch. The rocket’s nozzle (as is standard today, and as will continue the upward journey after de-mating with the cradle) will be only slightly modified (in one scenario but not another), and that will be, only to make injection points along the nozzle walls, to inject pressurized JP4, air, and water. For the first 1,200 feet of launch, then, the cradle assembly will turn what is normally the rocket’s nozzle, into a second combustion chamber. The rocket’s normal feed rate (rate of injecting fuel and oxidant) can now be throttled down to a fairly small percentage of what it would normally be, for the first 1,200 feet (saving fuel or allowing for increased launch payload mass, of course). The first (primary) combustion chamber, for the first 1,200 feet of ascent, needs only to burn enough fuel to heat the secondary combustion chamber to the point where the air and JP4 will burn, and these 2 sources of heat, together, will turn the water into steam, providing additional expansive energy and propellant mass. The second combustion chamber receives “free” JP4, compressed air, and water, that has been vertically pre-positioned in the launch-assist towers (the rocket does not need to “burn the fuel to lift the fuel” for this fraction of propellant mass). The lift cables can provide some additional vertical thrust to the rocket, yes. But their primary purpose will be to constantly provide enough lift, so that the cradle assembly will be kept mated to the rocket, without slowing the rocket down. At the end of the 1,200 feet, the cradle slows down as the rocket’s feed rate goes normal (is “un-throttled”), and the rocket simply lifts up out of the cradle. Only the hoses at the injection points need to be de-mated (in the same style, perhaps, as a gasoline hose de-couple when a car driver drives away, forgetting the gas hose in the gas tank). And that added de-mating complexity is only needed in one scenario.
Many drawings are provided here, to show how this could work (along with variations of the scheme). Calculations are reviewed that show that this scheme could reduce, by about 4%, the weight of the rocket plus fuel, as it sits, awaiting launch, assuming the scheme pulls 2 “Gees”. This does not include the mass of the cradle, cables, and hoses, which, of course, stay behind. Also note, this 4% reduction mostly ignores lift imparted to the rocket by the lifting cables. If the lifting cables carry a substantial percentage of the mass of the rocket itself, the 4% reduction in rocket mass (or payload mass increase) could be even greater.
At the end of this document there is also a discussion of variable-geometry jet engines that convert over to become rocket engines instead, through the use of turbine blades that partially melt away (using “pyrometric ceramics” that have long been used in the ceramics-firing industry).
A Brief Personal Note, and “Why”
“Why” this document? The intent is, first, to throw these ideas into the public domain (to prevent anyone from patenting them). I intend to “defensively publish” this document, that is. After that, the intent is for this document to be posted to the web, to start a discussion about just exactly HOW these ideas might most rapidly, economically, and safely be implemented (to hopefully flesh out some more details, via “public domain rocket science”, if you will). I, Titus “Rocket-Slinger” Stauffer, simply want to see humans reach for the stars, ASAP! Why the “Rocket-Slinger” braggery? Well, simply, ‘1) it will serve as a handy tag for a web site and an email address, and ‘2) it breaks up my name so that web searches by my name will not easily tie me to the whole rocket-science thing. I don’t want, in my personal and professional life, to be (too easily or too endlessly) dragged into discussing the whole rocket-science thing, or to be tagged as a whacko “rocket scientist wannabe”, by people who lack serious interest in the topic. Serious discussions with fellow amateur and professional rocket scientists and scientist wannabes, yes, that, I do seek. Find me by topic on the internet, not by my name, please!
Oh, yes, one last thing: In seeking a compromise between personal braggery and trying to stay to humble v/s bragging about my humility and actual quest for privacy, trying to promote these ideas here v/s trying to tame the wild speculative discussions and askance glances at the “space cadet rocket scientist wannabe”, and so forth, I did want to mention that I’m a 1982 graduate of the USAF Academy. Former cadet #826254, that’s me. ASAP, BMEWS, AWACS, BOR, T-Shop, C-Store! My military days are so far gone and removed from my current career that I suspect I can help to gain just a tad of credibility by mentioning USAFA, and perhaps attract a few web hits from fellow rocketry enthusiasts (maybe even experts) among the zoomies and ex-zoomies, while also avoiding some negatives.
What will follow is a description of a “primary path” for this design, with little discussion of the exact details of the problems that are being solved, or of trade-offs of costs v/s safety v/s efficiency v/s environmental costs, etc. … Nor of problems being created by this design, and of how to alleviate them. Discussion (in this first, pared-down section) of alternatives and options will be kept to a minimum. When, inevitably, minimal discussion of alternatives and options creeps into this “primary path” design description, these alternative ideas will be color-coded in BLUE so that the reader may choose to easily skip over them. Then following the “primary path” design description, there will be a “detailed” section with discussions in greater detail, of alternative implementations, and of design trade-offs.
Primary Path Design
A bird’s-eye view of the launch facility would look like the drawing below. The only thing omitted (because it eats up a lot of space) is just a plain, empty field, in which the 4 JETs (Jet-Elevator4-Train assemblies), with their trailing hoses, cables, and launch cradle, can land, after flying off of the tops of the launch-assist buildings. Alternative scenarios would involve having the JETs brake to a stop at the tops of the launch-assist buildings, and NOT fly off of the tops.
Figure 1 (above)
Working now from the outer periphery towards the middle, essential elements will be described in more details, as needed. First, what are the “harp” towers? A side view of the launch towers and “harp” towers may be warranted first. These towers (for providing staying cables for counter-acting the lateral forces exerted by the JET) are called “harp” towers because they look a bit like harps, and the JET forces “pick one string at a time” as they travel up the launch-assist towers. The launch towers should be “smart buildings” with integrated strain gauges, and they should be built to deliberately include a fair amount of flexibility. By allowing them to bend (flex), as the JET travels upwards, the “harp” assembly provides countervailing force, primarily focused a string (or a set of strings) at a time. Two drawings are provided below, one with the system at rest, before launch, and one with the JET ascending the rail.
Figure 2 (above)
Figure 3 (above)
Continuing our journey inwards, covering the essential elements, the launch tower and its vertical rail should be described next. It should be a “smart building” with strain gauges on its main structural elements. These strain gauges measure structural deformation (flexing, bending, twisting) caused by the JET and by wind-storms, earthquakes, or other stresses. Thus, the building can be cost-and-weight-reduced, if the “smart building” control system includes being able to swivel the jet engines and to have the jets use vectored thrust, to cancel any wild gyrations of stresses on the launch-assist tower. Optionally, in wind-storms, the JET may be sent partways up the tower (or even to the top of the building), to be started up, and to provide countervailing forces against the wind. Additionally, other smaller jets or propellers (JP4-powered, electrically driven, or a mixture) could be installed at various heights and angles, to be part of the “smart building” approach to survive windstorms, while also reducing total structural costs. Since the building almost definitely should be strain-gauge-equipped and “smart”, for handling the stresses cause by the JET, then why not go all the way (and cover environmental stresses as well)? Obviously, a local energy source (for the jets and/or electric motors) would need to be part of this scenario.
The vertical “rail” should be described next. A bigger-picture top-down view here, necessary for making any sense of this, must also show a bit of detail about the JET assemblies. For allowing the JET assemblies to fly off of the tops of the launch-assist towers, and then to make a controlled landing, the JETs may need some control surfaces. So the tower is shown to be narrow, so that the JET airflow-control surfaces can overshoot the sides of the building. Note that the rail is hollow, accommodating solenoids for injecting pressurized JP4, water, and air, into the ascending JET. Also note that the JETs will be equipped with automotive-style “brake linings” and the launch-assist towers will be equipped with hydraulically activated “brake pads”. Why? For launch-forces control. Throttling the thrust of the jet engines can be used as a part of the control system for balancing the forces of the 4 launch-assist assemblies onto the cradle and rocket (and ultimately for keeping the rocket itself balanced, not toppling over), yes. However, jets are slow to respond to their control forces (fuel and air input, etc.). Automotive-style hydraulically activated simple friction brakes, on the other hand, have near-instantaneous response. Thus, they need to be part of the control system here.
Here is the top-down, rail-centered view of our “vertical monorail”:
Figure 4 (above)
And then here is a further-away view just for more clarification:
Figure 5 (above)
One important detail has been omitted in the above rail-centric drawings, and that is as follows: Since the cables will exert high lateral forces on the “fuselage” of the JET, an unacceptably high level of friction may occur between the rail’s lip and the JET. The below drawing zeroes in on where, exactly, rollers (long small-diameter wheels) should be place in the JET assembly… Exactly opposite the brakes, that is. Just like a car, we need both wheels to eliminate un-desired friction, and controlled brakes to deliberately add friction.
Figure 6 (above)
One face of the vertical rail is dedicated to injecting a mix of pressurized air and water into the JET assembly, and the other face is dedicated to injecting pressurized JP4 (jet fuel). The injectors are tilted to 45 degrees or so, so that upwards-squirting masses will not unduly impede or burden the JET’s upward travel. If the masses were shot out in a purely horizontal direction, then their zero vertical inertia would impede the JET, especially as the JET travels rapidly at the very top of the tower. If the air, water, and JP4 is shot upwards at sufficient pressures (and hence velocity), then (at least towards the bottom of the launch assist tower, where JET velocity is still low) the squirted masses may actually help propel the JET upwards.
Here is a side view along one of the faces of the vertical rail. Arbitrarily, the JP4 injectors are shown, which are vertically interleaved with air & water injectors. The water and air injectors, then, are “squirting upwards into the face of the viewer” as shown here, and their bodies are “dotted lines” when they go behind the JP4 injectors.
Figure 7 (above)
Details about the launch-assist tower are as follows: Besides structural support of the rail, the tower’s primary purposes are to pre-store air, water, and JP4 at pre-positioned elevations. By storing and pre-pressurizing this fuel and “reaction mass” ahead of time (by expending electrical, chemical, and/or mechanical energy ahead of time, to pump up, or pre-store, the energy of height or “potential energy” in the reaction masses), the rocket is allowed to “cheat”, by using reaction mass that it does not have to carry. The air-breathing jet engines themselves, too, by their very air-breathing nature, briefly allow the rocket to (indirectly) benefit from thrust derived by using oxygen and reaction mass (air) for free, from the ambient atmosphere, which is not true of conventional rockets. The launch assist tower also supports the electronically controlled hydraulic brakes, which are needed by the launch-control system.
No engineer worth his or her pay would consider pre-positioning the water in one contiguous 1,200 foot water column, because the water at the bottom would be horribly-highly pressurized (whose handling would require excessively high-cost, high-strength, and heavy tanks and/or hoses). The same is true of the brake fluids for the hydraulic brakes, and for the JP4 (and to a lesser extent, even to pressurized air). Also, as the JET travels faster and faster, towards the top of the rail and tower, it would be good for the pressurized masses to be injected at higher and higher speeds (backed up by higher and higher pressures, which is the exact opposite of what one gets with a tall column of fluid in a gravity field). So for these reasons, all of the pressurized fluids (or incompressible fluids backed up by pressure-providing gasses or pistons) need to be vertically segmented (in, say, 50-foot increments).
Immediately preceding launch, the jet engines should already be revved up. They can already be straining their lift cables, “chomping at the bit”, with each assist-tower-assembly providing, say, 10% of the lift needed to hoist the entire rocket (total 40% for the 4 towers, adds up quickly!). They (jet engines) obviously can benefit from some fraction of the pre-stored JP4 available to them, through the injectors embedded in the rails, while some other fraction of this JP4 is dedicated to feeding the rocket itself (via the hoses suspended by the lifting cables). What is less obvious is that even the jet engines themselves could sip a bit at the vertically pre-stored water supplies. Throwing water into a jet engine is a lesser-known but very effective technique for gaining additional thrust.
In any case, the already-straining, preparing-for-launch, but still-stationary jet engines can be supplied with fluids/fuel/supplemental reaction mass, via slow-reacting, relatively inexpensive solenoids. Solenoids open up to permit the flow of fluids to the JET, and as soon as the JET moves up out of its initial position, the solenoids (and fluids) shut down. For the first few feet of ascent, the reaction speeds of slow, cheap, conventional (electrically or otherwise activated) solenoids will be fast enough to match the slow ascent rate of the rocket. That is, solenoids open up as the JET slides upwards to receive what the tower and its rail “inject” into it, and shut down afterwards, fast enough to be efficient (and not spill any significant amounts of the fluids).
Very rapidly, though, the rocket’s ascent rate increases, and the conventional, slow-reacting solenoids will not be able to keep up (the solenoids open up too slowly, and shut down too slowly, to match the ascension rate of the JET). Fuel or reaction mass is spilled. For pressurized air and water, at middle elevations of the tower, this is (perhaps) fairly tolerable. Note that one face of the rail is dedicated to injecting JP4 to the JET, and another is dedicated to injecting a mix of pressurized air and water. Air and water are cheap… And they shoot out at an angle that is NOT directed straight at the rocket (downwards-draining water spray hitting the rocket will not “parasitize” the ascension of the rocket, since the injection angle mismatches the direction to the inadvertent “target”; “target” being the rocket). So, slow-reacting, cheap solenoids may be tolerable for spilling a bit of pressurized air and water, at least at middle elevations. On the other hand, suspending the weight of pressurized air (and then far more so, water, which is much heavier) just to be wasted, at the upper reaches of the tower, may rapidly become cost-prohibitive (in terms of extra strength and mass, and of course costs, of the tower). So even though SOME spillage of pressurized air and water may be tolerable at middle elevations, it may be necessary to go to more high-cost (and quicker-reacting) solenoids at the highest elevations, even for (harmless, inflammable, non-explosive) air and water. JP4, on the other hand, DOES provide some hazards in terms of flammability, and even in terms of explosions. So, just about ZERO leakage is tolerable there, and slow-reacting, cheap solenoids will VERY rapidly need to migrate over to faster-reacting, more-expensive solenoids, on the upwards journey.
Let’s cover the case of the pressurized air and water, first. The case of the jet engines straining but still at rest, and of slow solenoids opening and closing as the JET ascends slowly, at first, hardly needs to be diagrammed at all. Which leads then to the middle elevations, where (depending on economic analysis of the costs of a stronger building to hold more mass of water, some of which will be wasted, v/s the costs of faster-reacting solenoids) it may make sense to build a scheme under which pressurized air and water is released as diagrammed below. In vertical segments (each, say, 50 feet tall), a water-fall column is fed by spray nozzles, with some water collected at the bottom of the waterfall, and pumped back up to the top of the tank. The entire assembly (tank and waterfall) is highly pressurized. As the JET ascends, solenoids in the rail open up, allowing a mix of pressurized air and water to flow into the JET.
The below drawing shows heavier blue line widths in the arrows in the middle of the JET assembly, for pressurized air and water injections, which is meant to show that this matches the maximum opening of the solenoids (max flow rate to coincide with JET position). Cheaper, slower-reacting solenoids being used here, though, may mean that there will be some spillage before and after the JET is in proper position. Air and water are cheap, though, so some spillage should be acceptable.
Figure 8 (above)
At higher and higher elevations, though, the JET will be travelling ever faster, spillage rates (assuming slow, cheap solenoids) will increase, and spillage costs will increase, since it is costly to build a tower to suspend, at high elevations, the mass of large amounts of water (especially just to be wasted). So the costs and engineering trade-offs will start to dictate that more expensive, but quicker-reacting, and less wasteful, solenoids should be used for the water. Water injectors could be vertically interleaved with air injectors that are injecting purely nothing but compressed air (which is not as dense and therefor expensive to house in the tower; we can afford to waste pressurized air, even at high elevations). For the high-elevation water injectors, the best choice might be to borrow from the automotive industry. A mixture of air and gasoline is injected into a combustion chamber well ahead of time, and a spark plug ignites it at the precisely correct time to power a piston, shooting the water up into the JET. Just like a car engine, this require precisely machined good-quality tool steel, but the costs may be justified at the higher elevations.
Figure 9 (above)
Note that in addition to being more expensive, per injector, this scheme also requires more preparation work… Every injector has to be loaded with water before each launch. Also note that it would probably be a good idea to spring-load the chamber, so that the plunger will return to the “down” position after the injection shot, to prepare it for re-loading. An alternative to gasoline explosions might be gunpowder or other explosives, but this is probably not a good idea, for many reasons; costs, environmental, & safety.
For the JP4 (jet fuel) side of the rail, spillage of JP4 will not be at all tolerable. Spilled JP4 is expensive, dangerous, and an environmental hazard. Accordingly, for all but the very lowest elevations, cheap, slow-reacting solenoids will not do. The gasoline-powered injector should be used, with a few changes: JP4, unlike water, is expensive, and vaporization (out-gassing) is hazardous. So the opening of the JP4 injector (the “muzzle” of the “JP4 cannon”) should be gated by a cheap solenoid… Slow-reacting is fine. It would be opened, say, several seconds before the gasoline detonation (a few seconds of out-gassing of the volatile compounds in JP4 should be tolerable). Otherwise, it would be highly similar to the “water cannon” shown above. Also, during the filling operation way before launch, a nitrogen-gas feed line should fill the air gap (for fire suppression). Then between the time that the slow-reacting “muzzle solenoid” opens, and the gasoline explodes, nitrogen should again be fed to the air gap, for keeping ambient-air oxygen away from the JP4 as much as possible.
All injectors should be as precisely timed as is reasonably possible. This timing is hardly a major challenge to modern electronics… Precise positioning could be determined by Hall effect sensors, laser interferometry, LEDs and photo sensors, or any other kind of proximity detection apparatus distributed in the rail and in the JET assembly.
Alternative variations to the scheme discussed here, would be to “spike” the water with oxidizers and oxidants. On 2 out of the 4 launch-assist towers, oxidizer could be added to the water… Hydrogen peroxide would be a very good choice, or perhaps ammonium nitrate. On the other 2 towers, ethanol, methanol, or emulsified petroleum products (oxidants) could be added. More exotically, even methane clathrates could be added to chilled water, although that’s very likely to be impractical. The two “flavors of water” finally meet each other and react, only in the rocket engine, so the extra safety hazards (especially if concentrations are kept low) might be tolerable. Costs and environmental hazards would tend to prohibit the idea of tolerating spillage (with cheaper solenoids), though.
This leads us, next, to the JET (Jet-Elevator-Train) assembly. It would (on each side of the rail, one face of the rail for pressurized air & water, one for JP4) need to have a funnel to receive the highly pressurized (high velocity) fluids. At the top of the funnel would be an assembly familiar to many farm boys… A strong, rigid “goose neck” designed, much like the assembly on top of a silo-feeding metal silage chute, to re-direct high-velocity silage down into a silo. Except the goose-necks here are re-directing JP4 in one case, and high-velocity aid-water mix in the other, to flow down into the hoses. The paths to the funnels would be un-obstructed with respect to the timed injections from the rail. Above and below the funnels, however, deflection louvers would be tilted to receive the forces of any spillage (leading and lagging the fairly but not perfectly timed injections) of injected fluids, which then drip down to be blown up the funnel, or collected at the bottom of the fluid-receiving dual funnel apparatuses in the JET. The spillage collected at the bottom of the JET is pumped into the hoses leading slant-wise down to the rocket. These 2 pressurized funnel apparatuses are sealed away from each other, so that the oxidizer (air on one side) does not meet the fuel (JP4 on the other side). The funnel apparatuses (just like the hoses) are pressurized with respect to the outside world, to hasten the journey of the fluids down to the rocket. They are not, however, as highly pressurized as the being-injected fluids, so that all fluids are sped, at high speeds, through all legs of their journey.
Figure 11 (above)
The body of the JET will need to be strong and highly resistant to bending (probably tool steel in major structural elements), so that it can meet the rail with minimal tolerances (mechanical mis-matches). If tolerances are too tight, friction (resistance to motion of the JET along the rail) builds up. If tolerances are too loose, leakage of pressurized fluids will go out of control. 1/8th or 1/10th of an inch or so (gap between rail & JET) might be the right target. The rail surface will need to be greased, pre-launch. Some leakage of pressurized water and air should be quite tolerable. Leakage of JP4 to the outside world, in small amounts, can be tolerated also. A fire-suppression system along the rail can be implemented, and spillage of JP4 (that amount that does not vaporize, at least) can be collected at the bottom of the tower. However, accidental leakage of outside air, into the body of the JET, especially into the interior of the JP4-receiving funnel and louvers apparatus, would be an un-acceptable fire or explosion hazard. Accordingly, the JP4 funnel / louvers area should, during its ascent, be pressurized by the timed release of a liquefied, super-chilled inert gas. Liquid helium would serve as a VERY inert gas, but liquid nitrogen would do the job almost as well, more affordably. The inert liquid nitrogen would be dispensed to both suppress heat, and to highly positively pressurize the funnel chamber on the JP4 side, to resist invasion by external, ambient air. Liquid nitrogen, of course, will expand into a gas as it heats up. Both effects would suppress the likelihood of accidental fire. The liquid nitrogen would be carried all the way through the ascent of the JET, inside the JET, providing minimal burden to its thrust-to-weight ratio. Alternately, JP4 could be injected intermixed with large amounts of pressurized nitrogen, through the rail, or JP4 injectors could be vertically interleaved with a few nitrogen injectors, but the extra expense and complexity is probably not worth it.
The JET, as previously mentioned, would have a swivel motor (air pressure powered from the jet’s compressors, or electrical powered) embedded in it, to allow the two jet engines to swivel their thrust alignment to be more vertical or less vertical, as is needed. Here are a few more drawings to clarify what the over-all JET assembly might look like. Note that in the prime scenario described here, the whole assembly of JETs, hoses, cables, and rocket-assist cradle would fly clear off of the tops of the towers, and need to make a controlled vertical landing afterwards. So, the JETs need a reserve tank of JP4, as well as telescoping (perhaps air-pressurized) landing legs. Alternately, the brakes would be used to slow down the JETs as they approach the tops of the towers, so that the JETs do NOT fly off the tops of the towers, but that means their ability to assist the rocket is truncated towards the end of their ascent, and leads to other problems as well. Note that the jet engines in the pair, on one JET assembly, need to counter-rotate with respect to each other, so as to cancel out torsion, or twisting effects onto the JET body, as the engines rev up and down.
The JET assembly drawing above shows the funnels further up and the swiveling jet engines further below, in other words. The above drawings have so far implied that the funnels might impede air-flow to the engines, though. All of these drawings are purely conceptual. In reality, the engines should be further separated, to allow them un-obstructed air-flow, and to more widely space their air-flow control surfaces… Also allowing the launch-assist towers to NOT be forced to be very skinny. Note that the tow cables should also be attached to the part of the JET body that has to be heavily-enough built to support all the thrust of the engines. Here is a further-away top view to clarify these items:
Figure 13 (above)
Not to belabor the things that should be obvious, but the rotating true axle should be encased with a non-rotating sheath, which should also have some reinforcing truss-work back to the JET “fuselage” for extra strength. The sheaths should only stop when it almost touches the jet-engine assemblies, to allow the engines to swivel, and the sheaths should also carry JP4 fuel lines, controlling electronic wires, and electrical power (generated by the jet engines) for use in the “fuselage”. The sheaths also support the tow cables; they are clearly the focal points for major forces and stresses, from the tow cables and the jet engines, and so they will need to be heavily built. Here are side drawings of the JET assembly, minus the air-flow controlling fins, for clarity. Complexities like side hoses for feeding JP4 to the engines are omitted. Note the presence of extensible legs for vertical landing.
Figure 14 (above)
Figure 15 (above)
That now covers the essential elements of the JET assemblies. Next come the cables and hoses (as we continue our journey from the outermost elements towards the innermost). Very few diagrams are needed here. The cables should be derated to cover several times more than their expected loads. If, for instance, each launch-assist tower plus JET assembly exerts 10% to 15% of the weight of the rocket (to keep the cradle forcibly mated to the rocket) of upwards lifting force on the rocket, then the cables, per tower, should be able to lift or suspend 50% or more of the rocket’s weight. Cables should be periodically inspected for degradation, obviously, and there’s not much more to be said there.
Hoses will be attached to the tow cables for mechanical support. Hoses should be derated for pressures to be handled, “TBD” (To Be Determined; this author is not smart enough to tell the reader what PSIs, Pounds per Square Inch, of pressures should exist at various stages of the fluids’ journeys), and periodically be inspected and tested as well, just like the cables. Here, there is a less-obvious factor to be considered, for the hoses, though. That is, when gasses and liquids are intermingled, as air and water will be, in one hose or set of hoses, and JP4 and nitrogen or helium in the other hose or hoses… Please recall the afore-mentioned safety measures… Then gasses v/s liquids tend (via surface tension effects if nothing else) to “clump”, or segregate. This will not be good for the rocket engines that are ultimately being fed. So, for lack of anything else, better, to call them, periodically, throughout the lengths of the hoses, “apple corers” or gas / liquid re-mixers will be periodically be embedded inside the hoses. Think of a razor-edge “apple coring” device that you might keep in your kitchen. These will periodically, during the travels of the liquids and gasses, in their journeys down the hoses, be embedded inside the hoses, to prevent “clumping”. A single drawing should suffice:
Figure 16 (above)
2 March 2013 update: Hi all of you rocketry and jet propulsion fans, I have finally received an un-solicited email relating to the business (topics) of this web site! A manufacturer of hoses (suitable for uses as here described) emailed me. So I hereby grant them some free advertising, here is their contact information. Following that, is my email response to them, asking about the proposed device shown above in figure 16. I don’t have a budget to develop the ideas I show here; Bill Gates has NOT yet offered to fund my ideas! But discussions about the ideas here, and where to buy suitable parts or materials? Yes, absolutely, let’s get those conversations going!!!
Hi Mr. Tung,
I got your email a while back and am now finally responding. Apparently you have actually glanced at my web site at www.rocketslinger.com and have noticed that I mention uses for fire-resistant industrial-grade hoses. I have added your contact information to my web site, as the least I can do for you. Sad to say, I have no budget to actually spend on high-pressure hoses, or anything else I describe in my web site, I am just an amateur fan of rocketry and jet engines… And I also want to help fend off “patent trolls” in this particular type of technology! … So anyway, no, sorry, I have no money to spend buying your hoses. If you do have spare time to look some more at my web site, please look at “Figure 16” (use that as a search string). You see that I have proposed a method of periodically mounting an “apple corer” style liquids and gasses re-mixer, inside the hose, so that liquids v/s gasses “clumping” would be prevented (globs of liquids would be periodically re-mixed with the gasses, if the mix is flowing at high speeds). Perhaps some would call this a “homogenizer”… Is this something that is done in the hoses industry? Is there a better way to do this? Is there a special term for such things? I can’t buy from you, sorry… But I am interested in the industry. If you care to respond to this, I will be surer to post your response on my web site.
Thanks! -Titus, AKA RocketSlinger@SBCGlobal.net
… Back to original web site materials now…
Air intermixed with water is not a problem, it will help to oxidize the JP4 as the fluid masses are injected into the rocket engine. Nitrogen gas intermixed with the JP4 contributes nothing other than inert reaction mass, and so, if desired, should be separated out from the JP4, at least partially. Part-ways down the down-sloping tow cables… Or down at the cradle area or mounted on the nozzle extender walls… With NO anti-clumping “apple corer devices” between the JET and this “separator tank”, on the JP4 fuel line… A tank would allow gravity/acceleration and spin separation between the JP4 and nitrogen gas, with the gas being bled (most of it at least) off of the top of the tank. This tank should ideally be funnel-shaped, with the fast-flowing JP4 directed downwards in a spiraling motion along the sides of the funnel; small funnel end down, large funnel end up, gas-bleed valve to the top middle of the funnel. Then the anti-clumping devices can be inserted further down the JP4 line, to keep the JP4 intermingled with whatever remaining nitrogen gas that makes it through the separation tank.
Hoses and cables are now at least summarily covered. Next comes the rocket’s “cradle”, which encircles the base of the rocket, and supports extensions to the rocket nozzles. The nozzle extensions will be covered first. For the sake of simplicity, only one rocket engine will be shown at first, but the whole scheme here could apply to a multi-engine rocket as well. Admittedly, when the number of rocket engines gets up past 4 or 5, the plumbing would get difficult, in order to add extra reaction mass to engines that are in the middle of other rocket engines. Here is a side view of a single-engine assist scheme:
Figure 17 (above)
The above drawing shows (in heavy blue lines towards the bottom) hollow shapes for the nozzle extensions. These should actually be three-dimensionally honey-combed structures for compromising between weight and strength. Note the presence of gaskets between the walls of the nozzle extensions (which of course stay behind on Terra Firma after the brief ride up as assisted by the rocket-assist towers etc.) and the walls of the rocket’s original nozzles. The gasket falls away when the nozzle and the nozzle extensions part ways. The gasket is needed for preventing the escape of hot gasses due to mechanical mis-matches, and for protecting both the true nozzle walls, and the nozzle extension walls, from abrasion due to mechanical shock and vibrations. Asbestos can be used if no other suitable materials can be found, but only if permission from the health and safety NAZIs can be obtained, or if the rockets are built in a nation with more appreciation for common-sense compromises between engineering effectiveness, and environmental regulations, than is available in the USA today.
Note that some rockets (such as liquid-oxygen and liquid-hydrogen fueled NASA rockets) do not have a “throat” or a combustion chamber that is different from the nozzle or expansion area; for these rocket engines, the nozzle (expansion area) is the one and the same as the combustion chamber. There, liquid fuel feed lines are embedded into the nozzle walls, to simultaneously cool down the nozzle walls, and to pre-gassify (pre-heat) what was frigidly cold liquid, to become flammable gasses. In this scheme, the high-temperature gasket would prevent the bottom-most fuel-feed lines from feeding the fires, during the assistance-launch phase. This is a good thing, since (during the assisted-launch phase) we want to save (be miserly with) the primary rocket’s fuel, anyway. There would be only one combustion chamber, not two. After the nozzle extensions and the gasket falls away, the bottom-most fuel-feed lines would then be available for powering the rest of the rocket’s ascent. That scheme is not much different than the first, but here below is a drawing. Also note that since this drawing is simpler than is the case with the two combustion chambers and the two constriction throats, it (the simpler case) will be used in subsequent drawings.
Figure 18 (above)
As far as handling a multiple of rocket engines goes, if the number of engines is small, separate nozzle extensions can be used (some of them may be a bit misshapen at the bottom, or truncated in their innermost walls, at the bottom). In other words, only at the outermost walls of the clumped-together nozzles extensions or unified nozzle extension, only there, would the nozzle extension wall need to reach the ground, pre-launch, for weight-bearing purposes. The inner dividing walls can be truncated, and the unified expansion area is still highly pressurized by escaping super-hot gasses, propelling the rocket (plus assist cradle and nozzle extensions) upward. Note that in the below drawing, a constriction “throat” is still added to both engines, during the assisted ascent phase, so as to maintain high enough pressures and temperatures to burn up the added, injected JP4 and pressurized air (and to vaporize the injected water as well). Without the constriction throat, temperatures and pressures in the combustion chamber are too low.
Figure 19 (above)
If we go yet higher in numbers of rocket engines, then only the engines on the outermost edges of the clump of engines, can easily be “plumbed” to bring them additional reaction mass. Accordingly, only the outermost ones will have “plumbing”, and only the outermost ones will have “constriction throats”. As shown below… Red explosion-signs mean powered by rocket fuel carried by the rocket itself, and blue means using “imported” reaction mass from the assist scheme, please recall…
Figure 20 (above)
A top view of the cradle and nozzle extensions is hardly needed for the single-engine scheme. However, with a high number of rocket engines being supported, the design can get confusing. So here is a top-down drawing of this. The outermost, very heavy blue lined circle represents the outermost walls, that touch the ground for weight-bearing purposes, and encompass the entire hot-gasses expansion area, for lift. The black circles represent where the rocket nozzles touch the cradle / nozzle extender. The outermost rocket engines can easily be fed extra reaction mass, and so they show constricted throats (blue, smaller circles inside them; open white holes being the insides of the “throats”). Innermost engines do not (they show only minimal blue inside the black circles, where blue walls meet black walls, vertically, where cradle / nozzle extender meets rocket nozzle walls). Innermost circles show wider white holes, meaning no throat constrictions, that is. Filled-in blue areas (not all filled in, this author is too lazy!) represent the structure of the top of the cradle, where the cradle / nozzle extender assembly top, creates a fire-wall between the unified expansion area, and the rocket. A ridiculously high number of rocket engines is shown to demonstrate the general principles.
One single top view of the bigger picture, for the entire cradle assembly, should suffice. The number of launch-assist towers could be other than 4, but 4 is assumed in this primary design description, so 4 is shown. The cables-attached structural element could be called the “lifting frame” and should be square for 4 launch towers, 5-sided for 5 towers, and so on. The “lifting frame” could be hollow for re-distributing reaction-mass fluids, but doing so means re-directing the fluid-flow motions (impeding flow). The number of “struts”, then, down from the lifting frame to the nozzle extender, can vary also, and can also be hollow for accommodating fluid flow. Using hoses might be simpler. The number of struts should rise as the number of rocket engines rises, probably, but need NOT match the number of launch-assist towers. A lower total number of rocket engines keep things simpler, as far as re-directing fluid flow goes. Also it means that ALL of the rocket engines, and not just the ones on the outermost periphery, can be fed additional reaction mass, easily. So the below drawing shows only 4 rocket engines, but 8 struts for distributing mechanical forces better.
Figure 22 (above)
Only one major element of the design needs to be described in detail, and that is the matter of injecting the added reaction fluids into the combustion chamber. It is possible that the feed hoses could be constructed to resist (carry) high-enough pressures that the pressurized fluids would be highly-enough pressurized to be shot straight into the combustion chamber without assistance. However, such extremely-high pressure hoses might present safety (rupture) hazards, and might be so heavy as to impede the whole assist mechanism. We assume here that safety and efficiency considerations require a boost pump to inject the fluids, permitting relatively lower-pressurized, lighter-weight hoses. It might even be wise to have separate boost pumps for air and water on the one hand, v/s JP4 (with a bit of “parasitical” safety nitrogen gas intermingled with it, as mentioned before) on the other hand. However, note that it is common practice to intermingle an oxidizer and an oxidant, in a high-pressure, high-flow-rate environment, such as the pre-mixer right before the tip of an oxy-acetylene torch, for example. If premature combustion sets in, it is rapidly “shown the door”, bar-room bouncer-style, by the high speeds of the fluid flow, and is promptly spat out into the main combustion chamber (the torch’s external flame in the welder’s case). So here, all fluids will meet, right as they feed a rigid-walled, rotating-helical-screw-turbine-style injector pump, which force-feeds the fluids into the combustion chamber.
Two designs are shown here, each of which powers the injector turbo-pump with rotational energy derived from a small jet engine. Once again, JP4 is available throughout the system, as is ambient air, so why not? JP4 has excellent energy density.
The first scheme shown will be to bury the turbo-pump into the walls of the nozzle extenders. A clear advantage here is that there need not be ANY injection point modification of the original nozzle walls of the original rocket (the part that ascends after demating with the assisting, extended nozzle). Conversely, a clear disadvantage is that a belt or chain is needed to transfer rotational energy from the small jet engine to the turbo-pump. This is an added point of possible failure. The drawings here below show only the outer wall of the combustion chamber.
Figure 23 (above)
The second scheme shown will be eliminate the belt or chain, which reduces complexity and points of failure. Also, the turbo-pump is more accessibly for maintenance or replacement. The turbo-pump here is mounted on the rotating central shaft of the jet engine, and the entire assembly can swivel or pivot to clear the path for the demate process. The price is, the nozzle walls (of the true rocket, not the assisting assembly) must be modified to create a pressure-fitted injection point, which is also a point of failure. De-mating it may create a bit of downwards, parasitical drag on the rocket, lasting only for the de-mating time period. An inherent one-way flow valve must be built in so as to not spill rocket exhaust after demating. Think of the safety relief decoupling mechanism built into the gasoline hoses at the gas station…
The above-described schemes leave some major, expensive elements exposed to the rocket’s exhaust during the demating, which may be an un-acceptable. Even yet another scenario might embed a contiguous, integrated, in-line jet engine and turbo pump as shown in the second of the 2 above drawings (no belt or chain), with the entire assembly buried into the walls of the rocket nozzle extension. This might not all fit very well, and breathing external air would become a little more troublesome for the jet (or it would have to parasitize the main rocket engine’s combustion chamber for pressurized gasses to drive the turbine, which is certainly a viable choice). But such scenarios are certainly possible (and would eliminate both failure points, the injection point and the belt or chain). And it would shield expensive system elements from the exhaust of the rocket during demating. So, all told, this third (un-illustrated) choice may actually be best. If room (space) is an issue, especially vertical space in the nozzle extender, then more, smaller turbo-pumps, not fewer large ones, can be used.
This concludes the summary descriptions for the major elements of the jet-assisted vertical “sling shot” for assisting rocket launches.
Detailed Discussions of Principles, Trade-Offs, and Alternatives
Now that the basic, primary elements of the proposed design have been described, let’s move off to show a minimal amount of math, or at least numbers, to show that this idea is both practical and effective. Then let’s go over principles, trade-offs, and alternatives or variations of this design.
First, what kinds of speeds can we expect at various points in time and in elevations off of the launch pad? http://en.wikipedia.org/wiki/Thrust-to-weight_ratio shows the space shuttle as having, at take-off, a mere 1.5 for thrust-to-weight ratio, which also means the astronauts feel 1.5 “Gees” (acceleration force as a multiple of Earth’s gravity at sea level). The launch-assist method here described assumes 2 “Gees” of acceleration… Too much would mean that the rocket would be travelling too fast, by the top of the 1,200 foot assist towers, for the injectors to be timed well enough to do their job. Too slow would mean the assist scheme is not doing its job well enough to achieve its goals (increase payload and/or reduce fuel and vehicle mass of the rocket itself). 2 “Gees” may or may not be the optimal target number, but it is probably close, and can show that resulting numbers are realistic. The question of, how fast do you “fall into the sky” at 2 Gees, one Gee being cancelled out by Earth’s gravity, is exactly the same as the question of, how fast does an object fall in Earth’s gravity? http://answers.yahoo.com/question/index?qid=20090624115259AA3RuYH shows how to use calculus to derive time for a given distance. The rest of the math is elementary. Because this author is lazy, the exact correct “G” for Earth, at 32.2 feet/second-squared is rounded down to just 32 for calculating the below table… So our assisted rocket is going to pull very slightly less than 2 “Gees” off of the launch pad. The below table shows distance, time, and speed above the launch pad.
12 feet - 0.87 secs, 28 ft/sec, 19 mph
25 feet - 1.25 secs, 40 ft/sec, 27 mph
50 feet - 1.8 secs, 58 ft/sec, 40 mph
100 feet – 2.5 secs, 80 ft/sec, 54 mph
200 feet – 3.5 secs, 112 ft/sec, 76 mph
300 feet – 4.3 secs, 138 ft/sec, 87 mph
400 feet – 5.0 secs, 160 ft/sec, 94 mph
500 feet – 5.6 secs, 179 ft/sec, 122 mph
600 feet – 6.1 secs, 195 ft/sec, 133 mph
700 feet – 6.6 secs, 211 ft/sec, 144 mph
800 feet – 7.1 secs, 227 ft/sec, 155 mph
900 feet – 7.5 secs, 240 ft/sec, 164 mph
1,000 feet – 7.9 secs, 253 ft/sec, 173 mph
1,100 feet – 8.3 secs, 266 ft/sec, 181 mph
1,200 feet – 8.7 secs, 278 ft/sec, 190 mph
1,300 feet – 9.0 secs, 288 ft/sec, 196 mph
1,400 feet – 9.4 secs, 301 ft/sec, 205 mph
1,500 feet – 9.7 secs, 310 ft/sec, 211 mph
So then a nine-second assisted burn time, and 2 “Gees”, and 1,200 foot tall launch-assist towers sound like good numbers. The towers are not so tall as to be impractical, and the injectors embedded in the rails should still be able to “keep up”.
Now, what about the amount of fuel sitting in the rocket, at launch, that can be saved by the assisted-launch scheme? For this, we consult http://en.wikipedia.org/wiki/Rocket and search for the below out-take:
Begin Wiki quote:
Main article: Tsiolkovsky rocket equation
The delta-v capacity of a rocket is the theoretical total change in velocity that a rocket can achieve without any external interference (without air drag or gravity or other forces).
is the initial total mass, including propellant, in kg (or lb)
is the final total mass in kg (or lb)
is the effective exhaust velocity in m/s or (ft/s)
is the delta-v in m/s (or ft/s)
End Wiki quote.
From the preceding table we chose a 9-second burn, but that’s with the Earth’s gravity negating 1 of the 2 Gees being pulled. Now re-calculate and see what our delta-V would be if Earth’s G was not there, so we can see what Tsiolkovsky rocket equation has to say… Use 64 ft/second-squared here, rounding off again… This below table shows a launch profile of a rocket lifting off of the Earth at 2 “Gees” of acceleration, if the Earth had no gravity… Alternately, in the real world, it shows a rocket lifting off at 3 “Gees”. This is done so that we can see what our speed is after a 9-second burn (our “delta V” at 2 “Gees” in the real world, with the rocket having to burn enough fuel to counter-act the Earth’s one “G”; in other words, we are correcting the rocket equation, which excludes gravity, to include gravity). The whole table is shown just to give the reader another look at how the numbers stack up at a higher rate of acceleration. The real purpose is to get the 576 ft/sec “delta V”, which is what we’d have after the 9-second, 2-Gee burn if Earth’s gravity is taken out.
100 feet – 1.8 secs, 115 ft/sec
400 feet – 3.5 secs, 224 ft/sec
800 feet – 5.0 secs, 320 ft/sec
1,200 feet – 6.1 secs, 390 ft/sec
1,600 feet – 7.1 secs, 454 ft/sec
2,000 feet – 7.9 secs, 506 ft/sec
2,500 feet – 8.8 secs, 563 ft/sec
2,600 feet - 9.0 secs, 576 ft/sec ***
2,700 feet – 9.2 secs, 589 ft/sec
Use 576 ft/sec for “delta V”, then. For the rocket’s exhaust velocity, “Wiki” ( http://en.wikipedia.org/wiki/Specific_impulse ) tells us that says a bi-propellant exhaust velocity for example is on the order of 4,400 meters per second! 4,400 times 3.28 feet/meter is 14,432 ft/sec. ( 576 ft/sec ) / ( 14,432 ft/sec ) = 0.04 … Now the “Ln” in the equation means natural log, and just iteratively plugging some numbers in there and taking natural logs to solve the equation, M0 / M1 (initial mass over final mass after the burn) comes out to ln(1.04 / 1) = 0.04 … Only 4% of your (including fuel) mass is blasted away in the first 9 seconds of burn. Admittedly in the assisted-launch scenario, SOME of the initial mass of rocket fuel sitting in the rocket (proper), on the launch pad, pre-launch, is going to have to be burned to get the temperature up (in the secondary combustion chamber or in the combined combustion chamber), in order to ignite the JP4. This amount of fuel can easily be counter-balanced (or exceeded) by the additional thrust (lift force) conveyed to the rocket through the JETs and cables. And we didn’t calculate for air resistance either… These calculations are quite rough, and are merely intended to show that the percentage of launch-weight fuel that is expended in the first few seconds off of the launch pad, is NOT horribly significant, if we pull only 2 “Gees”. The assisted-launch scheme, then, is not horribly gainful if we limit ourselves to pulling 2 “Gees” for human-passenger comfort and safety (and the assist towers are limited to 1,200 feet or so). Parenthetically, NOTE that if advances are made in materials sciences that permit the economical construction of much taller towers, then suddenly the ideas here described, will become MUCH more attractive!
Note also that if we go back to “Wiki” and re-run the numbers, not for a “bi-propellant” fuel (like in the old Apollo/Saturn 5 days), but for a solid-rocket fuel (as in PART of the space shuttle scheme), then the exhaust velocities are significantly lower. Solid rocket fuel then… 2,500 meters per second, 2,500 times 3.28 feet/meter is 8,200 ft/sec. ( 576 ft/sec ) / ( 8,200 ft/sec ) = 0.07 … Iteratively solve again and ln(1.073/1) is 0.07, so our assist scheme, pulling 2 “Gees” for 1,200 feet (9 second burn), would save us about 7.3% of initial launch weight. Space shuttle being a blend of dual liquid fuels and solid fuels, halfway between 4% and 7% is maybe 5.5% or so… That is what we could expect to save in the scheme so far described, for a new, modern launch system. Still not that great.
However, if we pull much higher “Gee” forces for launching robust cargo (excluding humans), then perhaps the capital costs for initially building the launch-assist scheme can be paid off that way. Then we can still use the same scheme for launching humans, as a smaller side benefit. Suppose we pull 10 “Gees”, meaning that we “fall into the sky” at 9 “Gees” (take out Earth’s gravity, of course). We will be travelling MUCH faster by the time we get to the tips of the towers, and it is questionable if the propellant injectors will be able to keep up. In this scenario, perhaps it would be best for the JET assemblies to stop sipping fuel, and rely on reserve tanks only, and to rely on the tow cables more heavily, to get the “bang for the buck”, at the upper reaches of the towers.
So for reference, here are the numbers, re-crunched for “falling into the sky” at 9 “Gees” or pulling 10 G-forces (for those mathematics masochists intent on re-creating my numbers, I used 32.2 ft/sec-squared this time, times 9 is 290, 290 / 2 = 145 for the square root of distance / 145. Then take time * multiply by 32.2 * 9 = 290 = to get speed, 5,280 feet per mile, 60 secs * 60 minutes… * ( 60 * 60) / 5,280 = *0.68 ) :
12 feet - 0.29 secs, 84.1 ft/sec, 57 mph
25 feet - 0.42 secs, 121.8 ft/sec, 83 mph
50 feet - 0.59 secs, 171 ft/sec, 116 mph
100 feet – 0.83 secs, 241 ft/sec, 164 mph
200 feet – 1.17 secs, 339 ft/sec, 231 mph
300 feet – 1.44 secs, 418 ft/sec, 284 mph
400 feet – 1.66 secs, 481 ft/sec, 327 mph
500 feet – 1.86 secs, 539 ft/sec, 367 mph
600 feet – 2.03 secs, 589 ft/sec, 401 mph
700 feet – 2.20 secs, 638 ft/sec, 434 mph
800 feet – 2.35 secs, 682 ft/sec, 464 mph
900 feet – 2.49 secs, 722 ft/sec, 491 mph
1,000 feet – 2.63 secs, 763 ft/sec, 519 mph
1,100 feet – 2.75 secs, 798 ft/sec, 543 mph
1,200 feet – 2.88 secs, 835 ft/sec, 568 mph
1,300 feet – 2.99 secs, 867 ft/sec, 590 mph ***
1,400 feet – 3.11 secs, 901 ft/sec, 613 mph
1,500 feet – 3.22 secs, 934 ft/sec, 635 mph
Call it a 3-second burn for launch-assist towers 1,300 feet tall then. Reactant injectors (rail embedded) may or may not be able to keep up any more, at these speeds (this is an engineering question, not a science or mathematics question). But for the sake of getting some more numbers for analysis, let’s continue. In order to solve the “rocket equation” for how much fuel we’d save pulling ten “Gees”, we have to correct for gravity, and see, what is our speed if Earth’s gravity isn’t there, and we are pulling 11 “Gees” instead. 11 * 32.2 = 354, 354 / 2 = 177 …
1,000 feet – 2.38 secs, 843 ft/sec
1,100 feet – 2.49 secs, 881 ft/sec
1,200 feet – 2.60 secs, 920 ft/sec
1,300 feet – 2.71 secs, 959 ft/sec
1,400 feet – 2.81 secs, 995 ft/sec
1,500 feet – 2.91 secs, 1,030 ft/sec
1,600 feet – 3.01 secs, 1,066 ft/sec ***
1,700 feet – 3.10 secs, 1,097 ft/sec
Oooops, confession, I corrected for the Earth’s gravity TWICE above, I should have used 10 “Gees” not 11 “Gees”… I was just testing you, Dear Reader! The numbers are close enough, though; I won’t re-run them.
1,066 ft/second then is a good number to throw into the “rocket equation” to get a good idea of what we might save with a 1,300 foot tall assist tower, and pulling 10 or 11 “Gees” for 3 seconds. Run the numbers only once this time, use exhaust velocity halfway between a bi-propellant and a solid fuel (approximate a modern, shuttle-like setup). Halfway between 2,500 m/s (solid) and 4,400 m/s (bi-propellant) is ( 2,500 + 4,400 ) / 2 = 3,450… Times 3.28 feet/meter = 11,316 ft/sec. ( 1,066 ft/sec ) / ( 11,316 ft/sec ) = 0.094 … Iteratively solve again and ln(1.1/1) is 0.095, we are now saving about 10% of our launch weight with the assist scheme. Still not stellar… BUT, what if us getting up to a speed of 190 mph (pulling 2 Gees) or 590 mph (pulling 10 Gees) before we clear the tower tops, or some halfway point between these 2 numbers… What if this allows a new type of rocket or jet or rocket/jet hybrid to go into operation at that point? Save that thought for later!
Before delving back into details of the assisted-launch scheme, a few words about basic principles seem to be warranted. http://en.wikipedia.org/wiki/Rocket and then specifically the drawing at http://upload.wikimedia.org/wikipedia/commons/4/47/Rocket_nozzle_expansion.svg are very instructive. Everyone knows that rockets propel themselves by “throwing mass out their rear ends” just like a motor-boat and water, or an airplane and air. So that explains the need for a combustion chamber (almost entirely enclosed, often, to maintain temperatures and compression to sustain combustion) with a hole (“throat” of constriction) for “throwing mass out your $#%#”, if you will. But what about the flaring nozzle? Why is it needed? Because additional thrust can be obtained by the pressures of the escaping hot gasses. If the hot gasses behind or below the nozzle are more highly pressurized than the ambient air (or vacuum, vacuum being very thin gas, actually), then they “push” against the nozzle wall, imparting more thrust to the rocket.
Rockets launched from sea level or anywhere in the lower atmosphere, have rocket nozzles that are “grossly over-expanded”, meaning they are much larger than they need to be, for working in the lower atmosphere. Their hot gasses cool down fast enough that a lot of the nozzle “goes to waste”, and is extra mass carried without benefit in the lower atmosphere. Only at higher elevations, in thinner air, do the hot gasses (at the tail end of the nozzle) finally, clearly exceed the pressure of the atmosphere, so that even the tail end of the nozzle is giving additional thrust to the rocket. In the near-perfect vacuum of space, finally, the “air pressure” is near nothing, and so there, one might want a 50-foot long nozzle to capture ALL the benefit of the pressure differentials, at the logical extreme. There, our nozzle is “under-expanded”, then, in the interests, of course, of saving mass in that nozzle.
The launch-assist scheme can “solve” this problem, at least for the first 1,200 feet of launch. Air pressure differentials across 1,200 feet are minimal, so the extended nozzles can be fairly accurately tailored to be exactly what they need to be, for the first phase of launch.
The “Lifting Frame” Part of the “Cradle”, and Trade-Offs There
Bouncing around to a few topics in more detail, concerning the assisted-launch scheme, there is the “cradle” and “lifting frame”, for example. Why bother with the lifting frame (and struts from there to the nozzle extenders as well) at all? Why not send the lift cables and hoses straight on down to the nozzle extenders, dispensing with all the rest, in order to save mass? Well, two reasons: ‘1) By adding the lifting frame, the lifting frame materials can specialize in being optimally light-weight, yet being resistant to the high tension (“pulling-apart”) forces that they will have to withstand. The lifting frame could perhaps even be primarily made of very thick, low-flexibility cables. By un-burdening the nozzle expanders from having to withstand the high tension forces of the lift cables, the nozzle expander design can concentrate on specializing to do its job, and let the lifting frame specialize in doing its job, with perhaps less mass overall. ‘2) Stability and control. We don’t want the rocket to topple over. Where the tow cables meet the lifting frame is where the control point is. In fact, there is a trade-off there as well. The below drawing shows, in series, no lifting frame at all, v/s a deeper and deeper “basket” or “cradle” (longer and longer struts). Imagine the JET assemblies controlling (via controlled thrust and via brakes) the tilt of the cradle plus rocket, and trying to keep the rocket correctly balanced. Too-shallow of a cradle (or no cradle) invites instability, and too-deep of a cradle loses efficiency, in that more and more of the height of the launch-assist towers goes to waste. The optimal balance must be found as the JET assemblies “rock the cradle”! The rocket’s center of mass is shown as a red dot. Ideally the center of mass stays low for stability. Blue arrows shows the tilt-control or swiveling-forces focus. More stability means not only more wasted vertical capacity of the assist scheme, but also increased weight in the struts. The proper compromise must be found and implemented.
Figure 25 (above)
The “Struts” Part of the “Cradle”
Adding the lifting frame is also a good idea because now we can add struts as well. The struts can largely be made out of, or contain, shock absorbers (gas-pressure-filled and/or spring-loaded). These will help isolate the nozzle extenders to rocket nozzles interface from shock and vibrations. Struts (as well as the lifting frame) could be hollow to accommodate propellant flow if desired (even hollow shock absorbers can be designed for this). On the “Rube Goldberg” side of things (probably not practical, for high-speed fluid-flow needed here), hollow shock absorbers could be designed with one-way valves such that mechanical energy absorbed by the shock absorbers, could help propel the conducted fluids. Also somewhat obvious but deserving mention, the swivel point (swivel bearings) for the assembly of small jet engine plus turbo-pump shown in figure 24 could be part of a strut (for structural mass conservation). The strut could become a 2-pronged fork before it hits the nozzle extenders, allowing the space between the 2 prongs to accommodate the turbo-pump.
Discussion of Control Scheme Variables and Options V/S Number of Rocket Engines, Etc.
Conventional rocket launches today allow the rocket engines to swivel. This allows great power and flexibility to the control system. In the event of a large upset in stability, thrust re-direction can over-correct for it and then recover. In a maneuver that is familiar to car drivers who have driven on icy roads, the back end must follow the front end to execute a recovery. A simple set of drawings should suffice to illustrate the idea:
Figure 26 (above)
During the assisted-launch phase, the free-swiveling rocket engine can only be used as part of the control scheme in very limited circumstances. One scheme would be with only TWO launch-assist towers, and the rocket and cradle “walking the tightrope” between the two. In this case, the free-swiveling rocket engine(s) would only have a freedom of motion perpendicular to the “tightrope”, and the brakes v/s thrust on the JET assemblies would have to complete the control equations. If there were more than one rocket engine, they would all have to be in-line (centered on the “tightrope”) for this scheme to work. This whole idea seems at least slightly preposterous, but not entirely prohibited, so it does not deserve a drawing. Also preposterous (MORE preposterous that is, but once again not prohibited by laws of physics) would be to have the rocket engines not only be swivel-able, but also be on telescoping members with respect to the main rocket body, so that a rigid, unified nozzle extender could mate, in three dimensions, to multiple rocket nozzles, three-dimensionally arrayed, swiveling and telescoping at once, so that the outermost “lips” of their nozzles remain in one plane (which plane mates to the unified nozzles extender). This is not plausible in engineering terms, but is mentioned in an academic vein, in the name of completeness… This is the only way (other than the afore-mentioned tightrope scheme) that multiple swiveling nozzles can accommodate the assisted lift scheme envisioned here. So what this means is, the control scheme for the assisted-lift technique MUST prevent wild gyrations in configuration… It will not be as robust a control scheme as is the case with a free-flying rocket. Realistically, during assisted-lift launch phase, the thrust and the brakes of the JET assemblies will have to be in control.
What must be prevented, is any scenario in which the center of gravity of the rocket exceeds (or realistically, even gets close to) the swivel points where the lift cables meet the cradle. Since the lift cables come in at a 45 degree angle, the cable lift forces have both an “X” and a “Y” component. If the JET assembly creates more thrust (or takes pressure off of its brakes) to create more mixed “X” (horizontal) and “Y” (vertical) forces, it is going to create more “X” force, in a manner in which is going to help the situation, whether or not the “tipping point” has been exceeded. That is, the opposite lift tower and its tow cable, which has to drop back or slow down, is going to have to “give some slack”, which causes the “X” or “pull-on” force of the pulling-harder lift assembly to help the situation. But the increased “Y” pull, post-tipping-point, is going to aggravate the situation! It risks having the rocket topple or break, that is. A drawing should hopefully clear up the concepts:
Figure 27 (above)
The above drawing should also be interpreted to say, the rockets designed to use the assisted-lift technique should be designed with a low center of gravity. Also one could conclude that a wider top opening of the cradle leads to more stability (albeit at the costs of a more massive cradle). Precision, quick control (primarily with fast-reacting brakes between the JET assemblies and the launch-assist towers) will be vitally essential. The launch towers must be widely enough spaced to allow “slack” in the tow cables, for the control scheme to work. Alternately put, the rocket-plus-cradle assembly must have some freedom to travel North-South, East-West, without banging into a tower, during the 1,200 feet of assisted lift, for the control scheme to work.
The following ideas are probably not practical, or needed, in terms of costs and extra mass, but are included in the name of academic completeness: ‘1) If the cradle is deep enough, swiveling mechanical members (that swivel upwards out of the way when the rocket departs the cable) could be mounted on the lift frame, so as to go out and touch the rocket, during assisted lift phase, to prevent toppling, and ‘2) the rocket itself could include, towards its top, thrusters pointed in different directions in order to combat toppling.
As mentioned, two lift towers is theoretically possible, but likely not plausible. Three is better, but 4 is probably best. More than 4 gets complex, and provides more opportunities for an accident to cripple or destroy the towers. More towers make for more targets for accidents, that is.
“Flying Off of the Rails” is Indeed Hazardous!
Somewhat haphazardly bouncing from topic to topic, one of the very most serious potential weak spots in this entire scenario is what happens at the end of the assisted-lift phase. If not alleviated, the hazards at the tops of the towers are very serious. If the JET assemblies do NOT fly off of the tops of the buildings, then they must brake to a stop at the tops of their journeys, wasting much of the building’s costs (that do not add extra lift, at the tops of the towers). Also, the cradle assembly will continue upwards, yanking upwards at the JET assemblies at the end of the journey, as well. Academic completeness time again: If the braking method is used, and the JET assemblies start to brake well enough ahead of time to kill the entire upwards velocity of the cradle assembly, then yet more vertical capacity of the towers goes to waste. If the entire velocity of the cradle assembly is NOT killed by the time the JET assemblies reach full-stop at or near the tower tops, then, due to momentum, it will travel upwards to the point where (up past the JET assemblies and tower tops, inverting the 45-degree cable angle momentarily) it will forcefully yank inwards towards the launch site at the center, on all of the buildings, via the now-inverted cables. The buildings must then be built strong enough to resist that cables-snap action. Perhaps with horizontal cross-members between the building tops? That would be hard to accomplish if the buildings are sufficiently widely separated, and these cross-members would also provide more targets for accidents (think falling or exploding rocket). Travelling now clearly into “Rube Goldberg” territory, the cross-members, if used, could be equipped with explosive bolts for self-destruction if they come into danger, and there is sufficient warning time. The cross-bars can be sacrificed to prevent the towers from coming down with them, that is, in the face of impending disaster. If going-astray rockets can be rigged to self-destruct on command (as they often are), then so can segments of launch-assist towers..
Suffice it to say, then, that having the JET assemblies fly clear off of the tops of the towers seems to be a good choice. This does, however, present its own set of challenges: What happens when the JET assemblies fly off the ends of the rails? For most of the upwards journey, the forces of the jet engines are counter-balanced by the cables from the “harp towers”, as the reader will recall. And co-planarity of the JET assembly with the plane of the vertical rail is enforced by the (reasonably) tight-fitting mating surfaces between the rail and the JET assembly’s fuselage, and by the rollers on that fuselage.
But what happens during the fractions of a second when the JET assembly fuselage is half on the rails, half off of the rails? During this time, twisting or torsional forces threaten to wreak havoc on the rail and on the JET assembly (co-planarity enforcement is lost). So what needs to be done is: ‘1) Towards the last legs of the upwards journey, the rail’s injectors must start (on the JP4 side) to inject either nothing (depending on the JET assembly to release nitrogen into its intake and funnel area to purge JP4), or to inject, from the rails, nothing but pressurized nitrogen to accomplish a “purge” of most JP4, so that there won’t be much of a JP4 spill when the JET assembly flies off of the rail, ‘2) At the tail end of the upwards journey, the jet engines must be swiveled to provide thrust that is slightly to moderately greater than the pulling forces of the tow cables, and with the thrust also aligned to be parallel to the tow cables (previously to that they have been mostly vertically oriented in order to deliver maximum vertical towing forces), ‘3) The tower’s brake pads must give way to rollers instead, after the rail stops, so that the JET assembly, with thrust slightly greater than the pull forces of the tow cables, can “roll” right up the building side for a little while, and ‘4) then finally we REALLY come to the final demate. The JET assemblies could cut down their thrust so as to stop rolling up the side of the building, pulling slowly away. That is least traumatic, but a jet cannot change it thrust very rapidly. So that means more vertical building space to waste. A compromise is to deliberately throw in a “sacrificial crunch area” (think barrels along the highway, in front of concrete wall abutments) at the top of the building, which would need to be replaced after each flight operation. The “crunch are” absorbs the extra “push force” with which the JET assembly is still pushing into the building, post-demate from the rail.
OK, that latter crunch-barrels idea is possible and is retained (once again) for academic completeness. If this author was to be accused of “making things up as he goes alone”, he would be forced to confess! The clearly better alternative (requiring far less maintenance or replacements) here for smoothing the transition of the JET assembly off of the launch-assist tower-top is this: Place a large tapering-back hinged plane at the top of the tower, and put large spring-loaded or gas-pressure-filled shock absorbers to the rear of the hinged plane (with rollers). Now the trauma (risk of sudden uncontrolled motions) is taken out of the departure of the JET assembly off of the top of the building. Here are some drawings to illustrate:
Figure 28 (above)
Figure 29 (above)
Figure 30 (above)
More Details About the JET Assemblies
The JET assemblies may or may not need to include a swivel motor inside the “fuselage”, see Figure 12. If the jet engines themselves have sufficiently quick-reacting and powerful thrust vectoring embedded in them, this swivel motor will not be needed. This author knows next to nothing special about embedded thrust vectoring inside jet engines. The JET assemblies will probably NOT need very large (or perhaps even, any at all) airflow-directing fins or wings as are shown in drawings here (but they look cool, right?). Since they will never travel at exceedingly great speeds, and since they will land slowly, vertically, after a short trip, the air-flow control can be minimal to non-existent, most likely. Their journeys, post-building-tops, will likely be very short. A probably-non-preferred alternate scenario is for them to carry enough jet fuel to continue their rocket-assisting duties (feeding the rockets more auxiliary reaction mass) well past the building tops. Since they must continue (in the post-building-top mode) by burning and providing self-carried fuel, AND since their thrust must be directed at an angle to maintain separation distance from the rocket, this scenario is possible but not plausible.
It is true that in the above-described scenario, the JET’s brakes are lost at the top tip of the launch tower. There goes a major fraction of your launch-control system! But before this happens, the rocket (proper) should fully power its engines (increase self-carried fuel-feed rate to normal), and lift up out of the cradle, assuming its own, normal, self-sufficient control scheme.
One alternative design for the JET involves more than two funnel-and-deflection-louvers (fluid receptacle) assemblies. This could be done with or without changing the basic shape of the rail. Suppose, for instance, that we wanted to separate JP4 v/s air v/s water. Instead of 2 flat faces to the rail, we could have 3 flat faces. OR, we could retain the 2-flat-faces design as has always been shown here. In either case, we could make room for 3 separate columns of injectors inside the rail, and 3 separate fluid-receptacle assemblies inside the JET. The importance of near-perfectly sealing some such fluid receptacle compartments v/s another will vary. Separating air from JP4, for example, will be more important than separating air v/s water.
For now, this is all of the additional comments about the JET assemblies.
More Details About the Nozzle Extenders
A few more comments about the nozzle extenders may be in order. Comments were made, earlier, about truncating or omitting walls between one nozzle extender and another (fusing them together into one giant nozzle extender, with only the outermost nozzle walls being very long, reaching down to the ground for structural support pre-launch, and containing the hot gasses till the hot gasses are optimally expanded, deriving additional thrust). Another way to say this is, if adjacent streams of pressurized gasses press against each other, the hot gasses are providing, from one stream to another, the internal “nozzle walls” there… Throwing in an internal nozzle wall, with high pressures on both sides, does not allow for a pressure differential to push the rocket upwards... The additional mass carried, for the internal inter-hot-gasses-streams, goes to waste. This is NOT true, though, if there is a large gap in between semi-adjacent nozzles on the rocket proper. This can be illustrated with two more drawings that are oriented towards showing an alternative scheme for applying the assisted-lift technique, and that is what might be called the “doughnut-shaped” or toroid-type nozzle extender. This goes towards solving the “plumbing problem” of providing supplemental reaction mass to multiples of rocket engines. The rocket (proper) in this case, has engines directly slightly outwards, around the bottom, with NO engines in the center. The nozzle extender will then have an inner wall for weight bearing (pre-launch) and an outer wall, which may or may not bother to extend far enough to reach the ground. If the outer walls are extended far enough to reach the ground, “over-expanded” they may then be, yes, but… There may be an advantage in doing that, for making room for turbo-pumps mounted entirely inside the nozzle walls, as previously mentioned.
Figure 31 (above)
In the toroid scheme, complete nozzle-extender walls are needed in a “doughnut shape” (heavy multiple blue lines below, inner and outer walls), but there will be NO need, inside the doughnut, for vertical walls between one stream of hot gasses, and another, which is immediately adjacent (travelling in a circle around the donut). The top view should clarify this idea:
Figure 32 (above)
In other words, referring back to Figure 21, the toroid scheme solves a potential problem with what was discussed earlier surrounding figure 21… The innermost rocket engines in figure 21, cannot get “plumbing” for additional reaction mass, very easily. If the (un-supplemented) innermost rocket engines are NOT putting out enough high-pressure gasses, the inner “doughnut wall” as shown above, may be needed, to extract more thrust (via gas-pressure differentials), even in the case of figure 21. By arraying all rocket engines out along the periphery, and using the “doughnut approach”, all rocket engines can easily get additional reaction mass, and the gas-pressure differentials are optimally used for thrust. The “firewall” above isn’t really so much needed as a firewall, in the case above, it is more-so the structural material that holds the entire super-assembly of unified nozzles extender, together. The so-called “firewall” obviously needs to be placed below (or at the point) where the rocket-proper’s bottom tips of nozzles touch the nozzle extender.
Another set of options (concerning nozzle extenders) that needs to be explored is one that also involves propellant fluids. The primary design described how JP4, compressed air, and water would all be thrown into the secondary combustion chamber in some rocket designs, or into the combined primary/secondary combustion chamber in those (typically liquid hydrogen and liquid oxygen) rocket engines where the combustion chamber and nozzle are one and the same. However (especially if the amounts of water involved are large), then injecting water at this point would dampen the fires too much. This author is not smart enough to spell out the trade-offs and pick the right choice here (amounts of water and where to inject), but the previously-designed design may be optimal. If it is not, if the extra masses and complexities to be added to the nozzle extenders are worth it (to use more water, for example, w/o damping the fires), then several other options are available.
First, simplest, and easiest, is simply to inject the compressed air and JP4 in the added-on combustion chamber, without significant amounts of water. Then inject the water in the added-on nozzle or expansion area, with separate turbo-pumps. Call it the “water after-burner”, if you will, although of course the water “merely” turns to steam, it doesn’t burn. It DOES expand as it turns to steam, though, adding a great deal of thrust! Now the water does NOT dampen the fires. Water and air could be separately handled all the way from the tower, through the JETs and hoses, to the cradle. The extra complexity is probably not worth it. Near-perfection of separating air v/s water is not needed. Instead, the better alternate here would be, at the nozzles extender area, to add a liquid-gas separator. This has previously been described in terms of separating an inert gas from JP4, but here again is a similar summary:
A tank would allow gravity/acceleration and spin separation between the air and water, with the air being drawn (most of it at least) off of the top of the tank. This tank should ideally be funnel-shaped, with the fast-flowing air-water mix directed downwards in a spiraling motion along the sides of the funnel; small funnel end down, large funnel end up, air-bleed outlet to the top middle of the funnel.
If the use of exceeding large amount of water is actually the most cost-effective here, and the amount of pressure and heat in the extended nozzle area is not sufficient to flash all the water into steam, then another option is open to us. Actually, heat and pressure must be combined with time, to really figure this out. Those of us who have worked with ceramics and kilns know about “heat work”, or subjecting matter to heat, over a time period. To increase heat, time, and pressure, to the injected water, to force all of the water to flash to steam, yet ANOTHER “combustion chamber” preceding a final “constriction throat” could be added. “Combustion chamber” here is actually a “flash-to-steam” chamber here at the final stage, if we are to be honest about functional names..
On a rocket that has a true combustion chamber and then a constriction throat as part of the rocket-proper’s design, there would then be THREE chambers and THREE constrictions throats. One (rocket proper, combustion chamber) for self-carried reactants to provide starting heat, one (nozzle extender, combustion chamber) for added-on compressed air and JP4 from the assist scheme, and a final set (nozzle extender, flash-to-steam chamber) for injected water. The last and final chamber and constriction throat would have to be the largest, having accumulated the most propellants.
A typical NASA-style LOX (Liquid Oxygen and liquid hydrogen) rocket with the rocket-proper having a combined combustion chamber and nozzle area, would have TWO (not three) combustion areas and constriction throats in this scheme… One (rocket proper PLUS assist scheme, combustion chamber) for self-carried reactants to provide starting heat, PLUS also for added-on compressed air and JP4 from the assist scheme, and a second / final set (nozzle extender, flash-to-steam chamber) for injected water.
The basic, simple idea of a chamber and a constriction throat here is the same as always… Constrict your chemical reaction area (be it combustion or water flashing to steam) with limited exit area, so as to increase heat, pressure, and dwell time in the chamber.
More Alternatives for the Injectors and Injected Fluids
The injector assembles embedded in the rail could possibly be powered by alternative methods (other than gunpowder or explosives as was mentioned earlier). Explosive release of steam pressure is one such method, or even electromagnetically powered rail guns could be used to propel the propellant fluids. But probably the more plausible and practical alternative would be to use sudden, explosive release of pent-up hydraulic forces. See for instance http://www.npr.org/2011/11/09/141931203/-power-for-the-planet-company-bets-big-on-fusion which describes an attempt to achieve controlled thermonuclear fusion, part of which technical effort relies on well-timed and powerful bursts from hydraulic pistons (AKA “air guns”; the working hydraulic fluid here is air). To quote from the web site:
“And just as the heated atoms get into the center, Laberge fires 200 pistons, powered with compressed air, which surround the sphere. "Those are compressed air guns ... that send a big compression wave, squash the thing, and away you go!"
If such “air guns” are powerful and well-synchronized enough for attempting controlled thermonuclear fusion, they could very well be a practical part of the assisted-launch methods here described.
Referring back to Figure 10, there is this matter of topping off the JP4, in the JP4 injector, with nitrogen gas as opposed to air, to suppress fire hazards. Plus the slow-reacting solenoid at the rail’s surface, to contain the nitrogen gas… An alternative to this whole scheme, which might be considerably less expensive, would be to fill this “air gap” with some sort of only-mildly combustible, fairly stiff foam, which would resist allowing the JP4 to out-gas, and which would, of course, still achieve the objective of replacing air (with its fire-hazard ingredient of oxygen, which we want to keep separate from the JP4 until the time is right). The author is no expert chemist, but, consider this: A stiff, mildly combustible emulsified petroleum foam fills the air gap. The gasses filling the bubbles in the foam are inert or combustible rather than oxygen- containing air. A thin layer of film or fine-grain mesh, slightly recessed from the surface of the rail, is tacked on top of the mildly-combustible foam, to retain the foam’s shape (resisting sagging) until the JP4 injector is activated. Thus, air (oxygen) to be parasitically injected along with the JP4, is minimized. The foam and the retentive thin film or mesh are both formulated to be easily chopped up and mixed up into the JP4 and burned up along with the JP4 (are formulated to be “digestible” by this system). This scheme would probably save money compared to what was described before (inert gas).
Admittedly, “emulsified petroleum” has another, far scarier name… “napalm”. So yes, pre-launch, even a mildly combustible formulation of “napalm” on the exposed surface of the rail, presents a security hazard. Think terrorists, stupid and evil people, etc. So this alternative increases the requirements for good site security.
9-15-2012 Update: Napalm, on second thought, is an inferior (dangerous) choice for the job at hand (topping off the fuel injector to eliminate the air pocket). A blend of low-volatility, low-flammability, but still flammable, waxes, like paraffin wax, and petroleum tar or thick oil, to create something still enough to retain its shape, but otherwise easily digestible by the system, would probably be better.
Earlier, the possibility of adding oxidizers and oxidants (in low-enough concentrations to preserve safety) to the water, in alternating towers, was mentioned. This would have at least a slight disadvantage, in that, in any multiple-rocket-engine scheme, the complexity of the hoses (or inside-the-hollow-lifting-frame-and-struts) fluids re-distribution scheme is increased. That is, oxidizer and oxidant-spiked “flavors” of water, from alternating launch towers, must be intermixed. Unless, that is, each rocket engine is fueled (by the rocket proper) slightly differently, during the 9-seconds-or-so, assisted burn. Those rocket engines who are given oxidant-spiked water, for example, feed slightly more oxidizer (liquid oxygen for example) than oxidant to the throttled-back primary fire (fueled by the rocket’s self-carried propellant). Excess self-carried oxygen can then burn up the excess oxidant in one set of engines, and vice versa for those engines that get oxidizer-spiked water. This alternative is probably better than dealing with the excessively complicated plumbing that is needed to mix 2 different “flavors” of water.
Yet another entirely different take on this matter would be to say, liquid oxygen is heavier than liquid hydrogen (in the mix of 2 hydrogen atoms to one oxygen atom as must be used). So if we want “bang for the buck” on saving self-carried fuel mass for the rocket proper, in a hydrogen-and-oxygen scheme for example, then ALL rocket engines would be supplemented with oxidizer-spiked water during the assisted-lift scheme, and none would be supplemented with oxidant-spiked water. The rocket proper’s engines then all feed more hydrogen and less oxygen than is normal, for a normal mix, during the assisted burn. Another way to say it is, both self-carried oxygen and self-carried hydrogen are way scaled back from normal, during the assisted burn, but the oxygen is further scaled back than the hydrogen is, since the water will be oxidizer-spiked. Thus, the rocket proper saves even more, oxygen-wise, which is the heavier reactant to be carried.
In any scheme in which the weight of the oxidant is greater than the oxidizer, for the self-carried reactants, then the incentives (and the scheme) is simply inverted, and the assistance scheme universally adds oxidant-spiked water instead (if self-carried reactants are going to be used to balance the water-spiking scheme in the first place).
With apologies to the reader, this document sometimes presents inferior alternatives, to them immediately replace them with better alternatives. But, one of the main purposes of this document is to list ALL even vaguely plausible alternatives, to fend off all of the machinations of the patent lawyers… Otherwise, the human race will spend its resources fighting (lawyer-wise and otherwise) rather than lighting up their rocket ships to go and explore and colonize the galaxy. So, all alternatives must be spelled out. Prevent the lawyers from adding a tiny little bit of excessive self-carried oxidant to an imbalanced reactants-supplementing scheme, and then claiming a patent on the whole scheme (or, more likely, fighting endlessly about it). March on, Brave Reader!
Along those lines, we must now torpedo the idea of spiking the water with any oxidizers at all (as being expensive and un-needed). Ambient air is the world’s cheapest oxidizer. Compressed air is the world’s 2nd-cheapest oxidizer. Any un-burned or partially-burned JP4 or other oxidant contributes to pollution (smog). So it is clear that the BEST alternative is to go way heavy on the compressed air, to make sure all oxidants have more than enough oxygen, and then some. Supplementing the compressed air with oxygen gas is also possible, but expensive and dangerous.
This does, however, still leave us with the possibility of saving money and/or improving effectiveness, by adding oxidant(s) to the water. Cheap oxidants? Why not use water-soluble agricultural and food-production wastes? Or even low-toxicity industrial wastes or biomedical wastes? As long as the waste water meets a fairly short list of qualifications, it should be suitable. Using it in a setup where there’s much spillage may not make sense, also. But here’s the short list of qualifiers: ‘1) Oxidant content must be high enough to out-weight the costs of transport, when justified by its utility as a supplemental rocket-assist fuel, PLUS any utility to be gained by the rocket-assist scheme being used as a way to safely dispose of otherwise-mildly or moderately dangerous pollutants. Radioactive wastes are not going to be made harmless by being flashed into high-temperature steam, for example. Delicate organic compounds (by-products) from drug production, though, might be suitable. ‘2) Objectionable smell or objectionable pollutants that survive the rocket fires must be minimized to an acceptable level. ‘3) The water impurities must not be so noxious to the launch-assist system as to degrade its lifespan. Clay / silt / mud content for example, if too high, will clog up and grind on all parts of the system, especially turbo-pumps. Salts aren’t good either.
So there you have it… Slightly absurd, perhaps, but… Wastewater? Why not? Run-off from the pickle factory? The fish cannery? Hopefully, it will not be necessary to list each and every possible category of food-production wastes to fend off the patent lawyers here!
Another set of alternative propellants can briefly be described here, but fall more into the near-distance science fiction category for now. Nano-tech industries are still too undeveloped for these ideas to be affordable yet. However, carbon “soccer balls”, nanospheres, or “buckyballs” could be constructed to contain oxidants, oxidizers, or explosives. Consider, for example, the original invention of dynamite… Nitroglycerin enclosed in some of nature’s version of “buckyballs” or nanospheres (diatomaceous earth, made of tiny silicon shells of long-dead diatoms). The dangerously unstable (sensitive to mechanical shock) liquid is made far more stable in this manner. If buckyballs could be economically designed to stabilize nitroglycerin, some other explosive, or a mix of oxidizers and oxidants, or to suspend an oxidizer in buckyballs in a liquid matrix of liquid oxidant (or vice versa), then it is entirely possible that ONE liquid fuel could be designed to safely explode in a combustion or explosion chamber, ONLY in the presence of very high temperatures. This could work in an assist scheme as described here, or in a regular, convention rocket scheme.
Super-cold liquid oxygen and/or liquid hydrogen or other liquefied, super-chilled gasses could theoretically be used in an assist scheme (injectors in the rails, & hoses as here described)… No laws of physics prohibit it… But practical and safety reasons make it prohibitive.
This concludes additional notes about propellant mass injectors and injected fluids at this time.
Trade-Offs and Alternatives for the Over-All Scheme
Some of the trade-offs have already been mentioned (more buildings means more targets for rocket accidents). Others are obvious… The buildings get more expensive as the get taller. Another set of variables not yet mentioned: Angle of the tow cables, distance from launch-assist towers to rocket and cradle, and whether or not the buildings are straight vertical. In favor of closely spacing the buildings is low mass and expense of tow cables and hoses, and lower real estate costs. Against close spacing is less North-South, East-West maneuverability room for the launch-control scheme, higher probability of rocket-on-towers accidents, and rocket-flame hazards to the buildings.
The angle at which the hoses and cables come down from the towers also invoke the same costs and benefits as mentioned above, plus more. A steep angle means that the JETs have to start their ascent at a higher starting point, further up the towers, wasting the usefulness of part of the expenses of the tall towers. A shallow angle increases the stresses (tension, pull forces) on the cables, and means that the buildings and rails have to be strengthened to resist those additional pulling forces as well. 45 degrees is almost definitely optimal.
One scenario is perhaps plausible but not practical, but at least deserves mention. That is a set of ideas that go along with, do NOT have the JETs fly off of the tops of the buildings, but rather, have them brake to a stop at the ends of their journeys. In this scenario, the towers and rails (or at least, the faces of the buildings that face the rocket) could be tilted outwards away from the rocket. The cables angle would start out steep at the bottom, shallow at the top. The towers could actually curve a bit outwards (increasing tilt angle) towards the top. The prime benefit here would be that the cradle assembly then does NOT, nearly as badly, have as much room to fly upwards, snapping back on the tow cables, when it is being brought to a halt after its ascent. The costs of beefed-up, stronger buildings, cables, and rails (especially considering the masses that have to be supported at building-top height, to withstand the still-remaining snap action of the cables, at cradle-trip end) is probably prohibitive.
Concerning the braking-to-a-stop-at-the-top scenario, another set of alternatives or options deserves mention. Consider demating time, at which point we have, at much expense, built up considerable upwards momentum into the cradle assembly, only to have to waste it by killing it with the brakes and/or cables-snapping action. Why not, instead, somehow transfer its upwards momentum to the rocket, instead? There are at least two alternatives here for killing the upwards momentum of cradle, while transferring it to the rocket proper.
The first option, we might call the “Rube Goldberg Meets Wile E. Coyote” option. Here, we mount, from the lifting frame (or from protrusions from the nozzle extenders) to the rocket proper, going upwards from the lifting frame to the rocket body, to meet structurally-reinforced lifting spots part-ways up the rocket body… Some large pistons that are pre-filled with highly compressed air, and/or mechanical springs. These lifting pistons are equipped with flanges that are bolted together with explosive bolts. At demating time, the explosive bolts are all simultaneously detonated. The cradle is flung downwards, and the rocket is flung upwards (by suddenly-released, pent-up expansive energy stored in the telescoping pistons, of course). Such pistons could be designed to either fall apart, or remain intact, after activation, whichever is more efficient. The pistons or remnants of the exploded lifting pistons must now somehow (perhaps with small rockets) be removed from harm’s way (prevented from damaging the rocket). Disadvantages: Extra mass to be carried, extra complexity. Advantage: Could also be used as an additional method to stabilize the rocket during assisted-lift phase. Also, such pistons could be designed to be powerful enough to not only cancel the upwards momentum of the “cradle” (including nozzle extenders), but substantial parts of the upwards momentum of the JET assemblies as well (coupled through the tow cables).
Perhaps more plausible is the following option: The nozzles extender assembly, at the throat (constriction) area, is equipped with a method of shutting off (or almost entirely shutting off) its throat. This is done exactly at demating time, just as the rocket-proper ramps up its reactant-feed rate to full normal. The resulting high pressures (small explosion if you will) of super-pressurized hot gasses (which no longer can escape through the constriction throat of the nozzles extender assembly) will “blow apart” the rocket from the cradle. Rocket is flung upwards, cradle is flung downwards, with little extra added mass or complexity. Disadvantage: Will probably not be as effective at cancelling all the momentum of the cradle, let alone the JET assemblies, as the first-listed method might be able to do.
The method by which this might be accomplished could be as follows: Pie-shape-tipped wedges are arrayed around the constriction throat, held back by small or weak springs pulling them outwards (plus they are held outwards by the high gas pressures inside the constriction throat). At demate time, the turbo-pump pushed fluids that remain (just water and air; JP4 should have been purged by this time) are solenoid-switched to stop feeding the combustion chamber. Instead, they are now suddenly switched to push inwards on the pie-shape-tipped wedges, which shut off the constriction throat.
Another disadvantage here is that the resulting explosion will blow out the gaskets between rocket-proper nozzle, and nozzle extender, with great force, tearing said gaskets to shreds. Using asbestos in this scenario (blowing asbestos shreds all over the countryside) is now probably in the totally unacceptable category. A better, safer high-temperature gasket material would need to be found. The good news is, said gasket material needs only to live for a nine-second burn. All you chemists, step up and do your thing!
Either of the two above-described scenarios could also be used along with the JETs-fly-off-the-tower-tops scenario; there is no prohibition there. Sudden motions or forces on the JETs, in this scenario, might be troublesome enough to make it not worthwhile. The advantages, though, of using either of the above techniques, along with the braking-to-a-stop method, would make the idea attractive.
A Short Description of the Sequence of Preparing for Launch, and Launching
A short walk-through of the entire sequence of preparation for launch, and launching, seems to be called for. The main scenario, not an alternate, is described here. Some ideas have been previously described, and some will be new to the reader.
Well before launch, the rocket-facing sides of the rails need to be greased, and the fluid injectors have to be prepped and filled. A special JET-like assembly could climb or descend the face of the rail to accomplish this, under its own power or, probably more practically, it could be stored at tower-top, and spooled out/down and back up, by a crane and cables system. Some fractions of this preparation will be by machines, some by humans. Maintaining and filling the injectors will be some combination of inside-the-tower activities, and rail-crawler activities.
A thorough visual inspection of the pre-greased rail surface should be made immediately before launch. This can be done from opposing towers, and might be assisted by television cameras mounted at the top edge of the JET assemblies themselves. Where JET meets rail, top edge, is clearly a danger zone here. We do NOT want dead birds, collections of insects, fallen objects, or pennies placed on the rail by children, to endanger our mission!
Immediately before launch, jet engines and turbo-pumps should already be revved up, straining and self-testing (on the JET assemblies and at the nozzle extenders). Hoses should probably be at least partially pre-filled. However, solenoids at the bases of the turbo-pumps on or in the nozzle extenders should NOT yet release the assisted-scheme propellants… The fires must be lit first!
“Lighting the fires” may be made slightly more troublesome here than in the past. The rocket (proper) needs to release fuel and oxidant, AND light the fire. A small set of dual squirts of “hypergolic” propellants (like hydrazine and nitrogen tetroxide, which self-ignite when touching each other, see http://www.braeunig.us/space/propel.htm ) could be released either by the rocket proper, or by the nozzles extender. This is not a preferred solution, though, due to the hazardous natures of the materials involved. Guns shooting granulated white phosphorus up from below, through the constriction throat(s), into the combustion chamber(s), may be a better choice.
After heat sensors indicate all fires are lit, the obvious needs to happen… Solenoids open up, fluids flow, and jet engines are fully powered up. Fluid injectors embedded in the rails feed the system in a timed sequence, as previously described. The rocket (proper) assumes normal mode and lifts up out of the cradle, towards the tops of the buildings. The JET assemblies fly off the tops of the buildings, and, powered by reserve tanks of JP4, travel in tandem, sideways, to gently, vertically land in an empty field close nearby, setting the cradle down first. Modern avionics should be up to the challenge of devising an automated control system to make it all happen!
Solid-Fueled Rockets and Aborted Launches
Solid-fueled booster rockets could be part of the whole scheme here, although it might be difficult to have them burn fuel more slowly during the first, assisted-lift scheme, 9-seconds-or-so burn, and then accelerate the burn rate later. Gaining fuel conservation for solid-fuel rockets, via this scheme, then, seems to fall into the “possible but not plausible” category. And solid-fuel rockets cannot easily be “un-lit”… Once they start their burns, they will continue to burn, period (short of drastic measures). Some liquid-fueled rockets (like those of Space-X) can rise up some distance off of the launch pads, detect a problem, then settle right back down on the launch pad (an obvious safety benefit). Solid fueled boosters can NOT be part of this safe-launch-abort-after-lighting-the-fires scheme! The various parts of the control system of the assisted-launch technique here described (controlled thrust on jet engines, controlled injectors, controlled turbo-pumps, and brakes for a controlled descent of the JET assemblies) could be designed to be compatible with safe partial-launch aborts… IF the solid boosters are kept out! Assisted launch as described here, then, might best be described as an alternative to solid fuel boosters. Partial-launch aborts here will obviously have some limits, with this scheme… Perhaps 1/3 to ½ of the way through those 1,200 feet or so. Afterwards, the momentum will be too large to stop. If the rocket wants to make a controlled vertical landing after that, it will have to side-step before doing so, since running the assisted-launch technique backwards is preposterous.
A prime reason (other than the above) why the scheme described here is a good replacement for solid-rocket boosters is, the method here does not pollute the atmosphere with ozone-degrading chlorine. See http://blogs.howstuffworks.com/2009/08/21/does-the-exhaust-from-rockets-create-pollution/ .
Ceramic Turbine Blades for High-Speed Jet Engines, Mounted on the Outer Engine Wall
The following ideas may not be very directly related to the primary ideas described here (jet-propelled vertical rocket assistance). However, while we are about the business of “defensively publishing” ideas related to rocket and jet propulsion, to prevent patent lawyers from “gumming up the works” of technological progress, why not? Also, see further below, ceramic turbine blades could be used in a “variable geometry” engine that is a jet engine at first, at lower elevations, and turns into a rocket engine at higher altitudes.
See http://www.popsci.com/military-aviation-space/article/2008-01/green-skies-mach-5 for example, or, the Feb. 2008 issue of “Popular Science”… Or Google “hydrogen hyperjet” or “Reaction Engines Scimitar”. It seems that for extremely high speeds (Mach 4, Mach 5, or higher speeds), a common complaint is that conventional (metal) compressor and/or turbine blades in jet engines will melt. In the worlds of materials sciences and engineering, it is well known that certain ceramics are far more tolerant of high temperatures than metals are. However, ceramics (unlike metals) are not good in tension modes (being “stretched out” or pulled apart)… They are good in compression modes, not in tensions modes. Also keep in mind that any BENDING forces will take a structural element, and create both compression (on the inside edges of the element, on the edge that the tips of the element are being bent towards), and tension. Tension will be created on the edge of the structural element that the tips are being bent away from. Think for example of a steel-reinforced concrete bridge beam with a heavy truck on top. The top of the beam will be in compression, the bottom of the beam will be in tension.
Now take a conventional jet engine (metal compressor blades and metal turbine blades, all center-mounted). The blades are all in tension (being center-mounted and spinning, centrifugal force puts them in tension). Invert the design, and substitute ceramic blades. That is, the ceramic blades are all OUTER WALL mounted, not center-mounted. There is NOTHING in the middle; the middle can now be a raging firestorm, with nothing but the tips of the heat-resistance ceramic blades nearby. The outer walls of the jet engine are spinning cylinders, where the ceramic blades are mounted (cylinders perhaps made of metal), but they can be cooled (from the outside). The ceramic blades are now in compression, which is the proper mode for ceramics.
An intermediate-to-high-speed jet engine could perhaps be designed with both compressor and turbine blades made of ceramics… Or perhaps metal and ceramic blades could somehow be intermixed. Major stumbling blocks probably include the following: ‘1) With a spinning cylinder design for outer-wall-mounted blades, the angular momentum becomes very large. Spinning the assembly up and down will take lots of power. ‘2) How does one inject fuel between the compressor stage and the turbine stage? Through a rapidly spinning cylinder with holes in it? Fighting centrifugal forces that want to throw the fuel back outwards? Could be tough! ‘3) Any attempts to rapidly speed up or slow down spinning ceramic engine blades will put one edge of a given blade into tension and the other into compression, due to the momentum of the blade. Any designer will have to keep this in mind, to create a safe design.
For higher-speed designs, the compressor can be replaced by “ramming the air” with the high speed of the aircraft alone. That leaves only the turbine area, where outer-wall-mounted ceramic engine blades could be used. This is a design that needs to be investigated… And now it has been “defensively published”; the patent lawyers have hopefully been banished!
A Tour of More Variations on This Scheme (to Include More-Fantastic, Science-Fiction-Like Ideas)
Methods other than jet propulsion could be used to propel variations of the JET assemblies up the sides of the launch-assist towers. Electrified rails, electromagnetic propulsion, electric-or-other-driven elevator motors and cables, or even gravity-driven masses coupled to cables could be used. If gravity-driven masses are used, their energy (upon the ends of their downwards movements) could be re-captured. One efficient method of energy re-capture would be to have them fall onto the ends of giant pressurized-air pistons, pressurizing the contained air even more. Excess pressurized air can then be used to inject into the assisted-rocket scheme, or used in air-driven motors. Jet power was selected here as the primary alternative, since the technology is mature, well-proven, and energy-dense, as well as reasonably practical and inexpensive.
It would be possible to provide the pressurized air for injection into the nozzle extenders, from the compressors in the main jet engines on the JET assemblies, or even from jet engines that are part of the nozzle extender assembly. However, this would not be optimal. Compressed gasses heat up, and heat is hazardous. Compressed air pre-stored on the launch-assist towers will cool down to ambient temperatures well ahead of time, so that when they expand (during their trip through the hoses), they will be cooler than ambient air. This helps preserve the life of the hoses and turbo-pumps, and reduces fire hazards. Then, when COOL air is injected into the combustion chamber, it expands more as it heats up, than hot air would. Getting rocket propulsion is very much related to getting those hot gasses to want to expand greatly (get yourself some maximum pressure differential across the nozzle walls). Cold air, then, not just-recently-heated-by-the-jet-engines-compressors, air, is clearly preferred.
Now for a brief digression before going on to describe some more “wild” ideas… And that is to briefly slam the lawyers some more. They help to gum up the works of invention, industry, and creativity. Google “Munchkin v/s Furminator” or variations of it, and find, for example, http://books.google.com/books?id=z6Tjs-4Ya3AC&pg=PA56&lpg=PA56&dq=furminator+munchkin&source=bl&ots=aySupmkMyB&sig=Ye0fcxC-o7Vyju447pw886VHt-c&hl=en&sa=X&ei=ddjYT-mRJIys8ATD1cTLAw&ved=0CHgQ6AEwBQ#v=onepage&q=furminator%20munchkin&f=false , for those interested in the legal aspects of such things. They got a patent on the idea of a pet-grooming comb shaped like a small rake, and put others (who had already been selling such things) out of business. This writer personally recalls similar horse-grooming combs in use decades ago. So no matter how trivial or obvious an idea is, one can get a patent, if one has enough money for lawyers. And patenting can even be done (or at least attempted) without showing the idea in practice, just for the purpose of PREVENTING the use of the process being “patented”; see http://www.organicconsumers.org/ge/humChimp.html ). We must bravely march on, and defensively publish more ideas!
As far as the launch towers themselves are concerned, one has to wonder, sometimes, why are human-created buildings so short and stubby, compared to the wondrously tall mountains constructed by nature? The answer is, because human buildings are hollow, and usually with very steep “slopes”, as compared to mountains. Which brings us to the assisted-launch scheme, and the fact that having the rocket come crashing back down onto your very expensive launch-assist towers and supports, is a prime hazard spot in this design.
How about, instead, if you have billions of dollars to spare, you have a mountain (or an extinct volcano with a pre-excavated crater area already there) rigged up as a launch-assist tower? The rails are mounted to 4 sides of a giant cavity in the middle of the mountain. Multiple large tunnels must be built into the mountain for bringing in materials and support, AND to allow the hot gasses to escape during launch. The hot gasses should be allowed liberal exit room, or else the pressure differentials across the nozzle walls, and the exhaust velocities of the hot gasses, and hence, also the magnitude of thrust, will be reduced. Carving up a whole large mountain is obviously a very expensive proposition, but far more than 1,200 feet of vertical launch-assist space could be gained that way. And the flanks of the mountain would be impervious to rocket explosions, pretty much.
The other alternative is to build oneself an artificial mountain, from scratch, in order to obtain those two benefits. One could also mutate the idea into turning the launch-assist scheme into a giant missile silo, or a giant gun barrel. High “Gee” forces here, of course, will stress out (or kill!) living cargo (such as humans). But one could certainly inject steam, compressed air, explosives, or other sources of pressure, behind the rocket, and up the silo or gun barrel it goes! The source of pressurized gasses can be from an assist scheme similar to what is described here (vertically pre-stored, injected into the assist scheme from the silo walls, turned into hot gasses by the vertically travelling assembly), or the hot or compressed gasses could be injected straight into the silo, below the rocket. A relatively air-tight seal at the bottom of the rocket would be needed, along with perhaps some padding. Along the flanks of the rocket, padding could be added… Think of giant slices of Styrofoam, or light-weight padding or hollow shapes, like slices of an orange, with a hollow at the center of the orange slices, for the rocket… That will all fall away after the rocket exits the silo / gun barrel. Now there is no need for electronic course control for the duration of the assisted launch. There, hopefully the patent trolls have been fended off!
One more wild foray into semi-science fiction-ish ideas: One can read of “space elevators” that depend on carbon-based nanotech fibers, see http://en.wikipedia.org/wiki/Space_elevator . One can also read about a “fusion ramjet”, see http://en.wikipedia.org/wiki/Bussard_ramjet . Now how about a hybrid of these two ideas brought back further down-to-earth and to the closer future? How about large-scale hollow carbon buckyballs that are manufactured to be filled with hydrogen? Think of gas-proof buckyballs (or sheets of graphene that have been wrapped up into a sphere) with hydrogen gas inside them. These balls (be they the size of grapes or of beach-balls) can all be strung together to (or strung to a rope of nanotech fibers), one to the other, in a tube or ribbon shape, and reach far, far into the sky, perhaps for miles and miles. Being lighter than air, our hydrogen balloons will float, and do so even better than helium balloons.
Now in one scenario, the lifting power of this long-long tube or ribbon of hydrogen-filled spheres will be sufficient to lift the rocket (with fires un-lit) far up into the atmosphere, first. Or maybe not… But in either case, once the fires are lit, the top of the rocket is a funnel, that sucks in air (oxidizer) and carbon balls full of hydrogen gas (both of which are oxidants). The rocket climbs the string of balls by “eating” them up, shredding the gas-filled balls, and burning them at the bottom of the rocket, and up and away we go! ***IF*** the gas-balls can be made to be safe (gas-tight) and economically enough, this is very likely to be more practical (attainable) in the near future, as opposed to a “space elevator”. Lawyers and patent trolls, you are hereby banished away from patenting this idea!
Hybrid Rocket / Jet Engines, or Variable-Geometry Jet Engines
Prior calculations showed that (in the 2 “Gees” case) we might save 4% of initial launch weight, in fuel, by “cheating” the rule of “you have to burn the fuel to lift the fuel to burn the fuel”, that makes space flight so expensive. In the 10 to 11 “Gees” category, with an affordable and practical height of launch-assist towers… ***IF*** the propellant mass-injectors in the rails can keep up… Then we can expect to save 10% of launch mass. Not very impressive, perhaps…
But, as was alluded to earlier, when mentioning ceramic jet-engine blades… What if the assist scheme was augmented with jet engines (or hybrid rocket / jet engines or variable geometry engines) that have a high thrust-to-weight ratio? Now perhaps, the assist scheme can get the rocket up to speed enough, by the time it clears the launch-assist towers, that such a new type of engine could be working effectively. ***IF*** such engines can be designed to be air-breathing, then the rocket would not need to carry nearly as much oxygen as they do in current designs.
Consider first a jet engine that could actually be used in any kind of aircraft today, where the front (compressor) blades are center-mounted, and the rear (turbine) blades are outer-wall mounted. Outer-wall-mounted turbine blades could be made of ceramics (for heat resistance). This will be our starting design, and then we will add elements to adapt it to the assist scheme, and for variable geometry.
The drawings below show the simple starting scheme, in a side view and then in cross sections travelling from front to rear (intake to outlet).
Figure 33 (above)
The drawing is repeated with cross-sections side-by-side with the side view, for further clarification.
Figure 34 (above)
Note that the spokes of the wheel could be tilted, in the same way as the turbine blades are tilted, so that the spokes of the wheel, too, just like the turbine blades themselves, actually serve as turbine blades as well as structural elements holding the entire spinning assembly together. Such wheel-spokes could also be several layers deep.
Note also (as previously mentioned) that center-mounted blades are put into structural tension mode, generally speaking, while outer-wall-mounted blades are generally put into structural compression mode, by centrifugal forces. The turbine blades in the above design, then, could be ceramic. Or they could be ceramic-clad metal. The spinning outer wall of the turbine area could be exposed to ambient air for cooling (or it could be enclosed, either way). If the spinning outer wall in the turbine area is left exposed to ambient air, it could also have protruding propeller blades out into the ambient air, so as to achieve 2 objectives simultaneously: Gather more cooling power, and propel the vehicle forwards or upwards (create a turbo-prop, essentially). Also note that (since the blades are arranged 3-dimensionally), there is no reason why the center-line of the turbine area must be left clear (the tips of turbine blades can over-lap). Also note that the turbine blades are NOT restricted to being long-thin-knife shaped. In order to resist any bending motions (which are not good for ceramics), they could be shaped like a wedge or a shark’s tooth (pie-slice-shaped). And then finally, also note that the turbine area could be cone-shaped or rocket-nozzle-shaped, so that (certainly at least at higher elevations, in thinner air) it could, rocket-like, derive thrust from gas pressure differentials… ESPECIALLY if, later on during the ascent of a rocket / jet hybrid’s ascent, the turbine blades were melted, cut, or blasted away.
Alternately put, how does a rocket nozzle derive thrust from a gas pressure differential across the nozzle wall? Because the higher (superheated) gas pressure below the nozzle wall is higher than above the nozzle wall, as the rocket ascends, and the gasses-pushing-upwards-force is NOT counter-balanced anywhere else on the rocket’s body. If, though, one has put turbine blades into the nozzle, there is a down-wards thrusting (pushing) gas pressure differential there from the top side of the turbine blade with respect to the bottom side of the turbine blade, which is essentially pushing the vehicle back downwards (this is just another version of the “no free lunch” principle; the derived engine-spinning force of the turbine blades has a cost). Turbine blades are more harmful than helpful, as the vehicle ascends, and the air is too thin to sustain jet-engine mode. To convert to rocket-engine mode, design your turbine engine blades to melt over time, or blow them out by injecting explosives into the engine… Or, if the enclosed-turbine-area design is chosen, there is even the option of blowing out the entire turbine section!
In the interests of making at least some of this more clear, it’s time for some more drawings before moving on…
Figure 35 (above)
Now in the below drawing, we are starting to migrate towards the variable-geometry engine. Note that on the right side, we can entertain visions of the launch-assist scheme. An upwards-pointed funnel shape or shapes (with embedded one-way flow valve(s)) could receive propellants from the assist scheme. Male on the assist-side or propellant-injecting side, and female on the receiving side, for easy de-mate at separation time, of course. Also the assist scheme could have other provisions (motors, clutches, gears engaging to a small section of the outer rim of the turbine area of the rocket’s engine) for helping to spin up the rocket’s engines, right before lift-off. Assist-scheme details have already been covered, and would not differ much here.
Figure 36 (above)
Now what about more options for variable geometry? If we cannot design a good scheme for “planned failure” of the turbine blades at high altitudes (they melt out or we somehow blow them away with explosives or abrasives or chemicals), then we might either have to live with their parasitical effects at high altitudes, or we might enclose the entire nozzle / turbine area and cut it away at high altitudes (yes, do that over the open ocean, and warn ships in the region to clear out of the area, by all means). Maybe a saw blade would do the trick… Or cutting torches, perhaps. Or a set of strategically located explosive bolts? If so, how do you keep engine heat from setting off the explosives prematurely? Consult Wile E. Coyote!
Actually, being able to cut out the turbines section is not all that crazy of an idea… If the enclosing nozzle walls are made strongly enough to resist a slightly chaotic separation of the turbines section, and the (??) saw blades or cutting torches are applied at multiple points around the spinning turbines assembly, it is not all that unreasonable to believe that the separation could be accomplished without serious damage to the enclosing nozzle walls. Also, if the cutting away of the turbines was done progressively, proceeding from one thin slice to another (instead of “one fell swoop”), that might help. Cutting torches, PLUS saw blades embedded into the enclosing nozzle walls, might be a method by which all this could be done in small bits and pieces, avoiding any large, uncontrolled, chaotic (i.e., destructive) events.
And what about the compressor area? After the air is too thin to sustain air-breathing jet-engine mode, then reactants added to your now-a-rocket-engine-not-a-jet-engine, will want to blow hot gasses upwards as well as downwards, which is not good at all. That is, self-carried oxygen is going to have to start being injected into the combustion chamber as the air gets too thin. AND, frankly speaking, if we are to have a vigorous assisted-launch mode, with a large amount of reactants added during that phase as well, then the pressures in the combustion area may be tempted to “blow-back” upwards as well, during that time. So it would be good to have a shut-off provision between the compressor and the reaction chamber. Then if we do that, we might as well also (during spin-up, assisted launch time, and also at post-conversion-to-rocket time, ***IF*** we plan to just flat-out have to deal with the parasitical effects of the spinning turbine blades) make provisions to side-vent, downwards, the bled-off pressurized air from the compressors. If we are to bleed off (waste) compressed air for any significant period of time, we will want to direct the air downwards, for additional thrust. So add (switchable) bleed-off-downwards-side-vents to the compressor, a shut-off gate before the reaction chamber, and a provision for shedding the turbines section. Some of these elements may or may not actually make sense (some may be needed, some not). But here they are all, diagrammed.
Also keep in mind, all of the air-breathing elements here can be supplemented with regular rocket engines (for example, at the bottom of the rocket, while the variable-geometry engines hug the bottom, outer periphery). The variable geometry engines need not deliver greater than 1 for a thrust-to-weight ratio, ALL of the time, merely MOST of the time. For example, a few seconds or even whole minutes’ worth of slight ineffectiveness, immediately after departing the launch-assist tower tops (if such towers are used), can be “paid back for” later on, at higher speeds. Just at the end of the day, we need to be better off breathing external air at least some of the time, than we are, carrying all of our own oxygen, for the entire launch scheme.
PS, the above drawing shows the turbine blades at a straight angle, which is not good if we want more-pure structural compression mode for ceramic or ceramic-containing blades. That is, if we are to be honest, and include the downwards-pushing forces of the escaping hot gasses on the turbine blades, as well as centrifugal forces, then these blades must actually be tilted at least slightly UPWARDS . This fault is corrected in the below drawing.
Figure 37 (above)
Actually, the correction that has been made (in the angle of the turbine blades as we moved from Figure 36 to Figure 37 above) is in the correct direction, if we have ceramic or ceramic-containing turbine blades that we wish to keep in “structural compression mode”. However, the change may or may not have not gone far enough… Where are all of you public-domain rocket scientists that I have been looking for, to fill in all of the details? Help-help-help!!! PLEASE help fend off the “patent trolls” and allow humanity to escape to the stars!!!
What might the shut-off area look like? This is a mechanical detail. Basically we could have fewer, taller-vertically, swiveling vent blades, or more, shorter-vertically, swiveling vent blades. Shorter means more complexity, but less space taken up. Taller means less complexity, but more space is taken up. Vent blades must swivel around motor-actuated rods coming in, presumably from the rocket-body side, into the compressed-air section of the engine. A round void in these vent blades must be left in the middle, for the spinning shaft.
Figure 38 (above)
In more detail, just exactly what would a ceramic turbine blade look like? In other words, the previously described idea of cutting away parts of an entire turbine section, in flight, thus leaving an enclosing nozzle behind, is plausible but probably not practical (or at least, it is sub-optimal). It requires extra mass and complexity, including the enclosing nozzle walls to be left behind, AND it includes possibly chaotic and destructive materials behavior as the cutting is done... And finally, it sheds a lot of material that can do damage on the ground (or on ships at sea) far below it. If we can design a ceramic or ceramic-containing turbine blade instead, that melts, falls out, and/or fails or otherwise fades away after the appropriate amount of time, then those blades can go away and leave behind them, a rocket engine, without any of those extra troubles.
This is not at all as hard to do as one might at first imagine. There are some special devices that have been used for centuries now, known as pyrometric cones. These are made out of ceramics themselves. “Heat work” (heat soaked in by the cone over time) slowly melts (turns internal particles into glass or glass-like, thick-liquids) the cone. These cones are used to mechanically trigger the turning-off action of a ceramic kiln’s electric power switch, for instance (this author owns such a kiln with cone-triggered switch). Here’s the critical item: These cones are precisely manufactured to melt (“fail”) at fairly precisely, the exactly amount of “heat work”, or time and temperature, that is needed for a given kind of ceramic, pottery, or porcelain firing (different cones are used for different types of firings). So to imagine the manufacture of ceramic jet engine turbine blades, that melt away, at the right time (elevation), inside the variable geometry engine, is not at all very far-fetched.
For reference, see http://www.bigceramicstore.com/information/ConeChart.html and http://en.wikipedia.org/wiki/Ceramic (which says ceramics are already used as coatings for turbine blades) and http://en.wikipedia.org/wiki/Pyrometric_cone (which describes cones as being made of ceramics).
So imagine our shark’s-tooth-shaped or pie-wedge-shaped, outer-wall-mounted turbine blade. SOME parts of SOME of the turbine blades, we will want to stay left behind, so as to form an internal “constriction throat” for our now-a-rocket-engine. As the reader will recall, the constriction throat is needed to make sure that the reactants stays there long enough to create conditions of high pressure and temperature (and not be spewed out only half-burned). One of the previous drawings showed a hybrid jet/rocket engine with the spinning turbine section having a constriction throat built right into the walls (figure 37). That may not be needed, and may cut into the effectiveness of the design in jet-engine mode. What if we built that tapered “nozzle wall” shape into the turbine blades themselves? What if the turbine blades closest to the combustion chamber were to have only their very tips melt away over time, and then, the further that we travelled away from the combustion chamber, more and more of the turbine blades was designed to melt and fall away? The below drawing shows such a turbine section… Melt-away-the-blades areas in red, stay-behind-to-form-the-virtual-nozzle-walls parts of the turbine blades in black. Why the thin line of black into the red? Read further below…
Figure 39 (above)
So that’s what a cross-sectional view of a turbine might look like in this scenario. As far as these turbine blades themselves are concerned, their bases would be either solid metal, or solid metal enclosed in protective sheaths of ceramics (if temperatures are so high that the metal needs protection). If the solid-metal bases do need a protective sheath of ceramic, then these pieces of ceramic would be high-temperature ceramic, NOT melt-away-able, pyrometric type materials. The melt-able tips of the ceramic blades (the entirety of the blade as the aft-most or bottom section of the turbine) would contain a metal interior for strength and resistance to deformation, but… Here comes the important part… They would be highly perforated, Swiss-cheese style. These perforations would be filled with hockey-puck shaped plugs of pyrometric material, as would the entire section of ceramic material enclosing the melt-able tip. All of this would be assembled and glued together; the glue need NOT be temperature-resistant, since centrifugal force in the turbine will push the entire blade assembly up against the turbine wall anyways. After the meltable ceramics (pyrometric material) melts away, the highly perforated interior metal core of the blade is so perforated that it might as well not even be there, as far as the flow of hot gasses is concerned. The remnants of burned-away turbine blades will be slightly parasitic, yes, but not enough to matter, if the design is done right.
The metal core of the turbine blades, plus sleeves or sheaths of pyrometric material (non-pyrometric ceramic, optionally, for the don’t-melt-it-away base of the blade), and the hockey-puck pyrometric fillers for the holes, can all be manufactured using today’s conventional methods, then glued together, using NO complex or high-tech methods… Hand-into-mitten style. This should all be relatively inexpensive.
Figure 40 (above)
The above-shown approach is likely the best, but this particular author must humbly confess, that he is speculating, and doesn’t know the answers to many-many associated questions, such as:
‘1) Just how bad really ARE the parasitical effects of remnant, skeletal remains of turbine blades?
‘2) Are the metals used to make high-performance turbine blades so horribly expensive (titanium for instance?), that discarding some parts of some of them in-flight, would be unacceptable? Would this pose much of a safety hazard to the earth below, to shed metal parts of blades?
‘3) Would the “virtual rocket nozzle” inside the turbine area of figure 39 (where melt-away parts of blades taper off into turbine blades segments that remain intact) be effective, or are there major flaws in this idea?
‘4) Going way back to figures 36 & 37, would the “constriction throat” (necked-off area in an hour-glass shape) detract much from the jet-engine mode?
‘5) Does a rocket nozzle really HAVE to be cone-shaped, or could it be barrel (cylinder) shaped, with good efficiency?
Depending on the answers to the above, alternate scenarios for turbine blades composition and arrangements within the turbine should be considered… And documented here, once again, to fend off the patent trolls and the overly broad patents!
Consider, for example, a scenario in which case the barrel-shaped rocket nozzle is judged to be efficient enough, and the metal in the blades is considered inexpensive enough, to justify shedding them in-flight (at high altitudes, where the air has become too thin, self-carried oxygen has started being added to the reaction chamber, and the ceramic blades have started to melt). In this case, the ceramic blades could be made of many segments of metal core (no need for them to be perforated in this case), enclosed, once again, in pyrometric ceramics. The metal cores are segments that couple to each other tongue-and-groove-style, but are encased in the ceramic. The tongue-and-groove mated metal resists bending, even as the pyrometric ceramic turns weak, approaching liquid state. After the ceramic melts away, though, turbulent airflow, shock, and vibrations can practically guarantee that the metal parts will decouple and fall away. To guard against chaotic materials behavior ( all of the blades falling apart at the same time due to a domino effect, possibly endangering the whole vehicle), it would probably be best to use low-melting-points ceramics at the innermost tips of the blades, and in aft sections of the engine, working in a graduated fashion towards higher and higher melting points as one works towards the outer walls of the turbine, and upwards or forwards. Thus, the weakest parts will fall out in a graduated fashion, without quite so much danger of “runaway positive feedback” as engineers would call it (AKA “domino effect” in this case). In this case, a cross-section of a turbine blade might look like this:
Figure 41 (above)
As a fine, miniscule little refinement of the above idea, let it be mentioned in passing… A fine-scale hooks-and-barbs surface finish on the tongue-and-groove mating of the internal metal elements, could make it easy for the metal elements to remain together, when encased by surrounding ceramic sheaths… Resisting shock-and-vibrations forces that otherwise could loosen the cohesion of these internal elements. But those hooks-and-barbs fine-scale elements, then, AFTER the enclosing ceramics melt away, will RESIST allowing shock and vibration to put the metal segments back into their original mated position! Resembling a one-way ratchet, forcing the disintegration, but ONLY after the melting away of the enclosing ceramic sheaths allows the freedom of motion for these internal metal elements to overcome the “hooks and barbs” effect.
As mentioned before, once again, all of this could be glued together with low-temperature glue (admittedly the complexity of manufacture has gone up, and the above scheme may become more vulnerable to shock and vibration and the need for more secure fastening methods may increase)… And centrifugal force is our friend, if we stick to the whole scheme of mounting the blades on a spinning outer wall, pointed inwards. Centrifugal force will hold it together, till the ceramic elements melt one by one, in a graduated fashion. Absent an enclosing ceramic sheath, each metal element, in turn, will shake loose and fall away. The arrangement within the turbine area will facilitate gradual (non-traumatic) disintegration of these blades, given that we already know how to finely graduate the “heat work” or melting temperatures of required of pyrometric ceramics, is “obvious to the casual observer”, as your engineering professor used to say, and so will not be illustrated (for now, pending all of the fans of this website banding together, and DEMANDING an illustration)!
So in the above scenario, this scheme would be suitable for allowing almost ALL of the turbine blades to fall away… Leaving the question of, what serves to be the constriction throat of the rocket engine, then? Perhaps one that is pre-built-in, as in figures 36 & 37. But if that is not practical… AND if a properly shaped “rocket nozzle” in the form of a tapered cone is vitally essential… If, otherwise stated, it is essential that the escaping high-pressure gasses in the rocket nozzle have “something to push against” as they escape out the aft end, at a correctly placed angle, and loosely spaced remnant turbine blades just will not “cut the mustard”… Once again, this author could elaborate and add more drawings if needed to refine these points… Then just perhaps it is time to consider a third and final configuration of turbine blade construction, and arrangement of the blades within the turbine.
In the below, we theorize that a long “barrel shape” or plain-cylinder shape of rocket nozzle will NOT suffice, and that the first scenario (figures 39 & 40) is not efficient, either. The escaping hot, pressurized rocket-nozzle gasses (molecules) just absolutely DEMAND that they have a nice, tapered surface to bang off of, escaping out the back end, so as to make SURE that they deliver optimum thrust to the rocket body (not sneaking off sideways and muddying up our picture of thrust efficiency, as they escape, especially at the very aft-most edges of the rocket nozzle or crude barrel pretending to be a rocket nozzle, for example). Well, then, what can we do to improve the escaping molecules’ chances of banging off at the right angle? Especially knowing that remnant turbine blades left behind, by their very nature, are loosely spaced, providing a weak molecular rebounding surface?
Well, we are NOT out of tricks yet! The determined engineer INSISTS that dumb, stupid, inert materials of the universe must obey our collective and creative will! So what we do in this case is, we resort to an ages-old, common little trick that everyone who has ever owned a door-hinge will recognize… We use a door hinge! 3 elements is all that is needed… A central bolt or rod to rotate around, and inter-locked fingers clasping the rod from the other 2 elements of the hinge. A simple hinge will be placed inside the metal core of the ceramic-encased turbine blade. Hinges, as we all know, can be built to allow motion in one direction, and in the other direction, only up to a limit. The turbine blade here envisioned has hinges built into the metal cores, that allow the hinge (only after the encasing ceramics melt away) to bend the metal tip of the blade, ONLY downwards / aft-wards, and NOT upwards. The encasing ceramic sheaths can be kept in ALMOST pure compression mode, if we tilt the turbine blade VERY slightly downwards, against the balance of the two forces… Escaping hot gasses push the turbine blades downwards (aft-wards), and centrifugal forces push them upwards / towards the turbine wall. The balance between these 2 forces is what was discussed earlier, and is why the adjustment was made between figures 26 and 37, see above. So now if we tilt the turbine blades very slightly back downwards yet against this balance, in an engineering compromise, there will a tendency for the turbine blade to “listen to” the pressures of the escaping hot gasses, which want to bend the turbine blade the other way (downwards / aft-wards), and to discount / ignore the centrifugal forces bending it towards the turbine wall (upwards). The slight bias will keep the partially-ceramic blade in MOSTLY compression mode, which is what we want (ceramics are not good in tension or bending modes, our materials engineers will always tell us). But now if we put a one-way-limited hinge (with limited motion range) inside the partially-meltable metal-and-ceramic turbine blade, we can pretty much guarantee, if a slight bias is added, that after the ceramics start to melt away, the bend-able blade-tip will collapse downwards / aft-wards.
We want to avoid “domino effect” or trauma, and so we put the lowest-temperature blade-bending effects aft-wards (once again). We let the collapsing (bending) blade-tips fall downwards (aft-wards), where they will rest on the tips of their aft-wards neighbors (if they have any). Keeping in mind that this is actually very three-dimensional, not two-dimensional as here shown in cut-away views, then post-blades-collapse, a very-much-more solid (contiguous) rocket-nozzle wall, in the more-conventional shape, will be left behind. ***IF*** it is highly desired for the sake of efficiency, that the half-broken blades have tips that bend back towards the turbine walls, then at least SOME of the escaping gasses will need a clear path through the remaining stubs of still-unbroken turbine-blades-bases, from reaction chamber to the aft edge of the turbine, to maintain spin energy (else spin energy may be entirely lost, and hence centrifugal energy that keeps the broken blade tips pushed outwards, will be lost also).
The below drawing follows the same conventions as before… Rainbow colored, with RED colors melting at the highest temperatures. This drawing should suffice to illustrate the graduated bending-downwards of successive layers of turbine blades, which will leave behind them, a fairly conventional rocket-nozzle shape. Notice that a gas channel is left, at the outermost edges, for conventional turbine operation to impart at least SOME remaining spin energy, so as to maintain the outwards orientation of the “broken”, hinged tips of the blades (due to centrifugal force of course).
Figure 42 (above)
(OK, the above drawing “cheats” a bit from top to bottom if one compares the two drawings; the non-melt-away bases of the aft-most blades grew in length, but the general idea should still be clear).
The above-described turbines (partially ceramic blades, mounted on the outer wall of a spinning turbine section of the engine) would work if the amount of “heat work” required to melt the blades, is less than the heat energy spent during a relatively short time that a vertically-launched rocket would need, to reach the high altitudes where blade melt-down is a good thing. This idea is hardly implausible. ***IF*** the ceramics could be designed to last even longer before melting, then an “aerospace plane” (conventional horizontal, airport launch) could be based on similar ceramic-blade-based designs. Keep in mind (refer back to figure 35) that external turbo-prop propellers could be mounted, pointing outwards, from the exposed outer wall of the spinning turbine area, for such a design to be able to gain additional thrust (this would be especially handy for an “aerospace plane” at low altitudes, it seems, to this author at least). Also keep in mind, such a heavy-lift aerospace plane could use mid-air refueling at about 40,000 feet or so, before proceeding further upwards. Mid-air refueling on the way up would be a good way to economically boost large payloads up towards eventual orbit, in this scheme… ***IF*** ceramic blade melting can be postponed long enough, or if some other alternate solution can be found, then melt-away ceramic blades may be part of the solution, for an “aerospace plane”. Alternate examples: multiple engines, some not activated until high altitudes are reached, or one vehicle carried or towed by another.
Variable-Geometry Jet/Rocket Engines, Further Notes, Updated 9-9-‘12
Hi all you propulsion fans, I’m back after a month-plus of not working on this web site. Please accept my apologies for an abrupt change in writing style, but I’m tired of trying to keep this all rather “professional” and third-person type style. I’ve not been getting a ton of feedback from the “professionals” anyway, so from here on in, I’ll be writing even less formally… More like me! But the subject matter stays all the same… And the objective remains the same! Fight off the ossification caused by patent lawyers! Defensively publish some more! I was sickened to see Apple getting away with patents on “a rectangular-shaped computer tablet with rounded corners”, and the like. So now can I “defensively publish” descriptions of every conceivable size, color, and shape of rocket and jet vehicle, and free the propulsion designers from future patent slavery? Maybe! But that would be rather boring… I will try to stick with describing seriously, significant ideas that might actually work. On the other hand, since I am NOT formally educated or trained in propulsion, I don’t know very certainly at all, which of my ideas are totally worthless, and which have good potential for working out well. So, same as I have in the past, when I come up with what I think are newer and better ideas, the older ones (which I suspect are sometimes not as good, perhaps even worthless) will remain documented here. I don’t know which will work, and which will not… So they must all stay, to carry maximum potential of fending off the patent lawyers. I want to take my vacation in orbit or on the moon one of these days, and the patent lawyers are NOT going to help me get there affordably! So back to the task at hand!
Concerning the use of pyrometric ceramic materials in turbine blades, upon further consideration, I now have hopefully better-optimized ideas here. The above are NOT optimized; the below are better. Here is a summary, and then we’ll get to the drawings for clarification: The idea of tiling the turbine blades slightly upwards or forwards, into the prevailing wind of the hot gasses if you will, is NOT the best idea, since, in three dimensions, it complicates the arrangements of these blades, and it isn’t really needed. The idea of staggering the amount of heat-work required to melt the pyrometric ceramic, so that the rear-most blades bend down first, is retained as a good idea. The hinge mechanism is selected as best suited for further refinement. The idea of coating or encapsulating the entire turbine blade from hinge up to tip, is discarded as un-necessarily expensive and massive (adds angular momentum as well as mass). If, instead, the entire turbine blade (including the hinge) is made of metal, and only the hinge is selectively encased in pyrometric ceramics, then these ceramics can be supported (and kept in compression mode) by adding a protruding “ledge” of metal, right underneath the hinge. Hence, there will be no more need to tilt the entire turbine blade upwards, and over-all mass is reduced.
Figure 43 (above)
In the above drawing, as before, centrifugal force keeps the ceramic materials in compression, so long as the blades are mounted on the (spinning) outer wall. Note also that, if at the leading and lagging edges of the blade, the ledge of supporting metal (on the non-hinged part of the blade) extends all around the hinged blade (on both ends as well as both sides), then the ceramics could be cast as one solid piece, covering the blade like a glove covers a hand. This time, though, the tip of the finger in the glove is cast aside, and, good riddance! There is, once again, no need to blend metals and ceramics together in any fancy manufacturing processes. The ceramics could be glued on, even using low-temperature glue, and centrifugal force will keep them in place (for the short duration of a one-time flight life of the refurbished blade). Using light-gauge wire, bailing-wire style, to secure them as an additional measure, would be a good idea, probably. This could be done by threading the wire through holes in the blade, above and below the hinge and ceramics, to lightly encase the ceramics and hinge area. Also, small holes in the “base pan” or ledge of metal that protrudes from the blade, to support the ceramics, might best be added so as to allow liquefied ceramics to flow out (after pre-planned ceramics failure).
As far as the weak metal parts of the blade (in both the hinged and un-hinged parts of the blade) are concerned, these are there to mechanically secure and support the ceramics, and to provide over-all mechanical security of the blade, but only up until such time as the ceramics melt. Pre-planned weakness of these metal parts could be achieved by adding divots, holes, or slots to the metal, or simply by making these metal parts significantly thinner than the other parts of the blade. The big picture here is that it should be fairly easy to design a blade (as shown here or very similarly) in such a manner that weak metal parts plus intact ceramics makes a good strong blade, but the blade will fold when the ceramics melt and the weak metal parts are then (by their lonesome, without the help of the now-gone ceramics) no longer strong enough to withstand the “prevailing wind”.
The next drawing is simply a flattened view from inside the turbine area, to show the obvious, which is that the ceramic blades have to be tilted in order to do their jobs. Here they are shown both before they start to fold, and after they start to fold. Folding starts at the aft-most blades and works forwards, of course, as controlled by different grades of pyrometric ceramics. If you think about this in three dimensions, you can see why I am discarding or disfavoring my earlier ideas of tilting the blades into the “prevailing wind”; this change is a very good way to simplify things.
Figure 44 (above)
The next drawing shows a side view, again, of the entire turbine area. If you refer back to Figure 28, you can see a drawing of a “shut-off area”, which for sure, would be needed in this or any other similar jet-engine-to-rocket-engine conversion scenario, between the combustion area (reaction chamber) and the compressor area, to prevent forward exhaust after the air gets too thin (compressor fails). A similar shut-off area (but with a much bigger hole or void in the middle) might possibly also be needed to create a “constriction throat” as in a conventional rocket engine. In the jet-engine mode, the presence of the turbine blades provides an impediment to hot gasses escaping, so as to improve the “dwell time” in a high-heat, high-pressure reaction area, for combustion to complete. In the absence of effective turbine blades after planned turbine-blade failure, the constriction throat (partial shut-off area) may be needed. This of course would be located between the combustion chamber and the former turbine area, now becoming a rocket nozzle.
Figure 45 (above)
In Figure #42 and associated verbiage, I previous stated that it is probably a good idea to retain SOME spin to the turbine area (imparted by allowing for SOME hot gasses to escape at the outer rim of the outer spinning wall of the turbine). The spin is for the purpose of retaining some centrifugal force, to force the tips of the bent blades out towards the wall; to make the bent blades create a virtual (or partial semblance of a) more-conventional rocket nozzle. The escape of hot gasses at the rim, there, is going to happen, in this design, whether we deliberately and intentionally design for it, or not, I think, on considering it some more. There really is little if any need to make allowances for it, either. The reasons why? Well, the “gas pressure differentials” across a nozzle wall, that I mentioned much, much earlier, isn’t much of a relevant way to think about things, in this case. If you insist in talking gas pressure differentials here, well, then, think about very, very little air pressure remaining in the high atmosphere, and that , after the conversion from jet to rocket engine, there is going to be WAY high pressure in the combustion chamber, pushing upwards against the shut-off area, with nothing but thin air pushing against the front or leading edge of the entire assembly.
The better way (in this case at least) to think about rocket nozzles is, they prevent the hot gasses from escaping at sharp angles away from the rocket body. If the hot gasses escape COMPLETELY STRAIGHT (completely opposite the direction of travel of the rocket) from the rocket, thrust is optimized. If they escape at anything approaching a right angle, for instance, away from the flight path of the rocket, then thrust becomes inefficient. The below drawing should clarify this.
Anyway, the presence of the bent blades, as well as the turbine walls, all of which are in-line with the desired gas flow, will be plenty enough to prevent wild-angled escape of the hot gasses. One more drawing them for clarification…
Figure 46 (above)
Note that the shut-off area between the compressor and the combustion chamber can be controlled in shades and degrees; it is not a binary on-off thing. The same will be true of the partial shut-off between combustion chamber and turbine area (if this is used in the first place). How does one determine, to what degree is one or the other or both, to be shut off during what time in the flight? Also, at what point in the flight will self-carried oxygen start to be added to the jet engine, now becoming a rocket engine? When does that happen, and how fast? I will have to leave this to the experts, to computer simulations, and to actual test flights. I would suggest having strain gauges in place in the mounting of each individual engine, so that performance (more thrust means more strain, more metal being bent more) can be monitored, per engine (not just measuring acceleration of the whole craft). Every few seconds, automated flight controls could tweak these and other variables, to find the optimal settings, for each engine. Turbine blade folding will doubtlessly progress differently in each engine, and in each flight.
Variable-Geometry Jet/Rocket Engines, Further Notes, Updated 11-10-‘12
One clear problem that occurs to me, with respect to the entire scheme above, is, plainly and simply, “wobbling”. As the blades fold, there will inevitably be radial asymmetries built up in the radial distribution of angular momentum. Think of the little balancing metal tabs or weights that the car tire guy has to put on your assembly of tire plus wheel, at the corner garage or tire-sales joint. Over time, the blades-folding process will, despite our best engineering efforts, proceed haphazardly. So… One possible solution is to mount tracks all around the outer circumference of the turbine area, which varying-sized weights can travel around on. Wobbling would tend to force these weights (if left to travel freely) to the outermost radius, furthest away from the rotational axis… Thereby worsening the problem! So these weights would need to have a power source, and a method of propulsion (or of crawling along the length of the circumferential tracks), and the local intelligence (or signals from elsewhere on the vehicle) to direct them to actively crawl AGAINST the direction in which centrifugal force “wants to” send them.
I don’t have any way-creative ideas on how to deal with all of that (hey all of you other amateur would-be rocket scientists, where ARE you, PLEASE help out here!). Email me at RocketSlinger@SBCGlobal.net with your ideas please; I will be happy to give you credit for your ideas if you’d like that. The only possibly-helpful suggestions would be, with any significant amount of air density left outside of the vehicle (and that is the time during which the conversion process happens, before we approach the vacuum of space), and no fixed outer wall surrounding the spinning turbines area, then the balancing masses are free to integrate into themselves, small fins or “sails” to tip this way or that way, into the surrounding airstream, to gain propulsion or track-crawling power. Perhaps it might be possible to build into these crawling masses, sensors to detect which way they should crawl. Here, I am short on details or ideas. Vibrations (FREE energy in the system!) might also somehow be of use. A flip-able one-way ratcheting mechanism to NOT allow the weight to move in the WRONG direction here, would fairly obviously be a possibly helpful ingredient of the whole scheme.
Yet another approach would be to have actively tilt-able external “turbo-prop” blades (see Figure 35) pointing into the external airstream. Dispense with the travelling weights on the circumferential tracks… Instead, tilt the external blades to throw air outwards, away from the wobble (only on the correct side of the rotating assembly) to push back against the wobble force, to correct it. Rather on the Rube-Goldbergish side of things I would say… And of doubtful effectiveness as air gets thinner and thinner.
A probably-more-implausible method of active balancing might be to have mounted on the outside of this spinning wall, a hollow tube full of dense liquid (water or oil). Build-in sensors all around the tube would detect fluid pressure inside the tube. Where-ever the fluid pressure is the greatest (where the off-center masses have concentrated, and therefor started to make the engine assembly wobble), an external energy source (??? Electric, airflow, vibrations, ???) would apply “squeeze power” or displacement power to force the fluid to go elsewhere. Inflate small balloons inside the tube, say, or have the tube itself be made of flexible, squeeze-able material (not rigid). Force the mass of the fluid inside the tube, then, to go to OPPOSITE of where it “wants to be” (due, of course, once again, to wobble that starts to set in, sending the highest-mass parts of the assembly out to an even greater radius, aggravating the wobble even more… We need an ACTIVE, powered, semi-intelligent entity here that wants to make our off-center masses “crawl up-hill”, to go and kill the imbalance). If the tube is rigid-walled, then some part of it would need to be air-filled rather than incompressible-fluid-filled, so as to allow the squeezed (displaced) fluid to be able to travel somewhere.
Another (simplest) approach would be to give up on the idea of the spinning turbines area being exposed. The idea in Figure 35 (pointing-outwards “turbo-prop” blades out there for additional propulsion at lower elevations, in denser air) would then be excluded. But, by enclosing the entire spinning-turbine area inside a fixed (non-spinning) outer wall, then another bearing surface can countervail against destructive wobble forces. This one deserves a drawing, see below. Notice that the folding blades have deliberately been shown to have folded asymmetrically (a prime, pro-wobble source of instability).
Figure 47 (above)
02-24-2013 Update: All right, y’all have not listened to my desperate cries for help, here, in the turbine-spin-mass, active-balancing-technology department, so, after many months of background tasking this in my multi-processor brain, I have come up with some better tentative solutions. This particular root web-page is getting way too long, and so, I am spinning off a sub-page at www.rocketslinger.com/turbine_spin_balancer/ …
Pre-stored reaction mass (propellant), vertically arrayed, could be a practical (albeit probably high-initial-capital-costs) method to reduce the costs of rocket launches, at least as far vertically as tower construction economics will permit. This is especially true if such a scheme could enable the launch of rockets supplemented with air-breathing engines (jet to rocket convertible, variable geometry engines). Jet propulsion could be a practical part of the methods for achieving many elements of such a scheme. These (and related) ideas deserve to be investigated and developed further. Jet engines that can convert to rocket engines, especially those using structural-compression-mode, pyrometric-ceramic-containing turbine blades, also deserve to be investigated and developed.
Preview of Coming Attractions
Hi all of you rocketslinger web-site fans! Unless I hear you want something else… Next thing I am working on, is to make the below off-shoot web site (a sub-site), since this one is getting large enough to load slowly, I suspect, for some folks. Next I am planning to explore, suppose we use the rail-embedded-with-reaction-mass (fuel, compressed air, water) idea as presented here, but cut it down to ONE rail only, a large one. Suppose we mount it at a 30 or 40 degree angle, maybe more, instead of vertically. Now we can build it on a mountain-side. Or we can build our own (perhaps skeletal, not solid) mountain to support such a thing. How would we build it economically? What sorts of things could we launch off of it? Come soon to a web site near you!
PS, Dear Readers, I suppose I’ve ragged on the patent lawyers and patent trolls enough by now… I’ll try to cut that out in my new stuff. You’ve heard my views on this already… And oh by the way, I don’t resent patents that are narrowly targeted at EXACTLY what technology has been developed, often at great expense. It makes sense that such investments should be protected and rewarded. It is just that patents have become way, way too broad, vague, and all-encompassing… That’s what we’re fending off here.
Link to Texas Art Concrete, AKA TexArtCrete, a Sole Proprietor Art Business:
Link to sub-page for Icy-Words Lander, AKA Europa Lander: www.rocketslinger.com/Icy_Lander/
Link to sub-page: www.rocketslinger.com/MntnMntdRcktRail/
Link to next sub-page: www.rocketslinger.com/turbine_spin_balancer/
Link to next sub-page: http://rocketslinger.com/Var_Cfg_Rck_Nzl/
Link to sub-page about a totally different field of endeavor: www.rocketslinger.com/SemiLamarckism/
Link to fictional works by Yours Truly: www.rocketslinger.com/RocketManFiction/
Anti-Patent-Trolls Magic Spell at www.rocketslinger.com/Near_Universal_Defensive_Publication/