next generation launch engine/fuel

[vulture4]

The X-15s made 199 flights, and the program cost about $6 million/year, not a lot even then. Experiments with a scramjet engine were beginning when the program was terminated; the flyable mockup of the X-15 scramjet is in the museum at Wright-Patterson. It was our only fully reusable spacecraft. Obviously it had only one seat, but that was 50 years ago. A liquid-fueled air-launched spacecraft is still a viable concept and the X-34, the logical follow-on to the X-15, would have advanced it greatly. Unfortunately Sean O'Keefe canceled it. Burt Rutan, who's company built the X-34 airframe, offered to fly the prototypes at his own expense. NASA inexplicably refused. If there is anyone reading this who knows why, please speak up. The X-34s are still gathering dust.

 

[vogon13]

Regarding SR-71 performance:

Note the guvmint has confirmed the SR-71 as Mach 3 capable, and claimed some records in the Mach 3 speed regime.

Also note the advanced titanium construction of the SR-71.


Then contemplate the XB-70 Valkyrie, with similar Mach 3 speed claims and enormously cheaper stainless steel skin and non-ramjet afterburner type 'conventional' engines .


Obviously, the turbo ramjet SR-71 is capable of a much higher top speed than the Mach 3 and change that is claimed.

Insiders (not divulgeing secure info, just informed speculation) feel a realistic top speed of the SR-71 is in the Mach 4 area, although for what duration is even more speculative. Cruising at Mach 3 with a 'dart' capability of Mach 4 for >30 minutes is probably not too far off what the technology could deliver.

 

[scottb50]

Regarding SR-71 performance:

Note the guvmint has confirmed the SR-71 as Mach 3 capable, and claimed some records in the Mach 3 speed regime.

Also note the advanced titanium construction of the SR-71.


Then contemplate the XB-70 Valkyrie, with similar Mach 3 speed claims and enormously cheaper stainless steel skin and non-ramjet afterburner type 'conventional' engines .


Obviously, the turbo ramjet SR-71 is capable of a much higher top speed than the Mach 3 and change that is claimed.

Insiders (not divulgeing secure info, just informed speculation) feel a realistic top speed of the SR-71 is in the Mach 4 area, although for what duration is even more speculative. Cruising at Mach 3 with a 'dart' capability of Mach 4 for >30 minutes is probably not too far off what the technology could deliver.

Either way it is not fast enough to light a scramjet and up to the point the scramjet lights it's dead weight and producing aerodynamic drag.

Look at the testing of scramjets, they need a B-52 to get them off the ground, a rocket to get them fast enough to light and they run for a few seconds before they run out of fuel. There is no way to get near orbital velocity with a scramjet before it burns up, it would have to be an interim stage between a rocket and another rocket which, to my thinking, makes the idea of just using rockets a whole lot simpler.

As a high speed missile it would allow long range at high altitude and a high speed decent, as far as being useful getting to orbit it doesn't make much sense. If it was possible to have a turbo-jet/ramjet/rocket/scramjet/rocket hybrid it might work. That's why a TSTO makes a whole lot more sense, rockets and turbojets for the first stage and rockets for the second. A much simpler configuration.

 

[halman]

scottb50,

Of course this thread belongs in Aviation! Because the key to inexpensive, simple launches is to take off horizontally, using an airfoil to generate lift. Lifting the space vehicle to 50,000 feet gets it above nearly 3/4's of the atmosphere, so that the rocket power of the space vehicle can be used almost exclusively to gain speed. By using ground assist to get the launch vehicle going fast enough to take off, engine requirements are greatly reduced. For the 5 or 6 minutes it takes to get from 400 miles per hour at 50,000 feet to 17,000 miles per hour at 160 miles, simple, cheap, proven rocket engines which burn kerosene and lox will be adequate. We have learned enough that we don't have to extract every possible erg of energy out of our launch systems to make orbit.

By getting away from the step-rocket design, we can alter our thinking about getting into orbit. Years and years of watching rockets go straight up has left many people thinking that the goal is to climb to the orbital altitude. Then, somehow, the space vehicle starts to orbit, and everything is cool. But, as the Rutan designed SpaceShip One proved, going straight up will get you into space, but it won't get you into orbit. Achieving orbit means reaching velocities measured in miles per second, not miles per hour.

Until we have learned a great deal more about physics, I don't foresee the application of nuclear power to atmospheric space flight. The thrust required to attain orbit is much too great, and the ejecting material heated by passing through a reactor core is almost certain to cause some radiation to reach the environment. Once we turn our attention to journeys from orbit to orbit, then nuclear power becomes attractive.

The secret to reaching orbit is not some exotic new fuel, or engine. It is to be as efficient as possible in building our space craft and how we operate them. At one time, turboprop engines were too expensive, too demanding to use in general aviation. Now that we have worked with turbines for a couple of generations, we have learned a great deal about them, and most new propeller driven aircraft have turboprop engines. To achieve the greatest efficiency, I believe that we are going to see a revolution in the materials used to build space craft. Properly constructed, carbon components can be stronger than steel in the same application. By making the frame of the space ship out of carbon, the weight of the vehicle can be reduced significantly,

By building a spacecraft which is designed solely to carry people, we can make our vehicle much smaller than the present shuttle system. The next generation vehicle may be the same size as the shuttle, but the payload bay area would be where the fuel tanks are. The cheapest way to send large amounts of mass into orbit is still a really big step-rocket. Until a space elevator is built, that isn't likely to change, because of the aerodynamic advantages a large rocket has over a small one. But there will need to be a constant flow of people back and forth between Earth and orbit, as researchers, field engineers, technicians, and operators are rotated on and off duty. This is where developing safe, reliable, cheap transportation to Low Earth Orbit is critical.

 

[scottb50]

scottb50,

Of course this thread belongs in Aviation! Because the key to inexpensive, simple launches is to take off horizontally, using an airfoil to generate lift. Lifting the space vehicle to 50,000 feet gets it above nearly 3/4's of the atmosphere, so that the rocket power of the space vehicle can be used almost exclusively to gain speed. By using ground assist to get the launch vehicle going fast enough to take off, engine requirements are greatly reduced. For the 5 or 6 minutes it takes to get from 400 miles per hour at 50,000 feet to 17,000 miles per hour at 160 miles, simple, cheap, proven rocket engines which burn kerosene and lox will be adequate. We have learned enough that we don't have to extract every possible erg of energy out of our launch systems to make orbit.

By getting away from the step-rocket design, we can alter our thinking about getting into orbit. Years and years of watching rockets go straight up has left many people thinking that the goal is to climb to the orbital altitude. Then, somehow, the space vehicle starts to orbit, and everything is cool. But, as the Rutan designed SpaceShip One proved, going straight up will get you into space, but it won't get you into orbit. Achieving orbit means reaching velocities measured in miles per second, not miles per hour.

Until we have learned a great deal more about physics, I don't foresee the application of nuclear power to atmospheric space flight. The thrust required to attain orbit is much too great, and the ejecting material heated by passing through a reactor core is almost certain to cause some radiation to reach the environment. Once we turn our attention to journeys from orbit to orbit, then nuclear power becomes attractive.

The secret to reaching orbit is not some exotic new fuel, or engine. It is to be as efficient as possible in building our space craft and how we operate them. At one time, turboprop engines were too expensive, too demanding to use in general aviation. Now that we have worked with turbines for a couple of generations, we have learned a great deal about them, and most new propeller driven aircraft have turboprop engines. To achieve the greatest efficiency, I believe that we are going to see a revolution in the materials used to build space craft. Properly constructed, carbon components can be stronger than steel in the same application. By making the frame of the space ship out of carbon, the weight of the vehicle can be reduced significantly,

By building a spacecraft which is designed solely to carry people, we can make our vehicle much smaller than the present shuttle system. The next generation vehicle may be the same size as the shuttle, but the payload bay area would be where the fuel tanks are. The cheapest way to send large amounts of mass into orbit is still a really big step-rocket. Until a space elevator is built, that isn't likely to change, because of the aerodynamic advantages a large rocket has over a small one. But there will need to be a constant flow of people back and forth between Earth and orbit, as researchers, field engineers, technicians, and operators are rotated on and off duty. This is where developing safe, reliable, cheap transportation to Low Earth Orbit is critical.

The big problem with what you talk about is the requirement to get a payload from 50,000 feet and Mach.8 to orbit. The one system that does it the Pegasus can put about 1,000 pounds into orbit and takes an L1011 to get to altitude, for a significant payload or passenger capacity the uplift requirements would require a proportionately bigger aircraft.

The optimum means is a TSTO rocket, vertical launch with powered fly-back capability and a restartable upper stage.

 

[vulture4]

The X-15 flew 199 times, costing only about $6M/yr in later years, not much even then. Of course it had limited capacity and was suborbital, but that was 50 years ago.. . The engine could operate a remarkable (for a rocket) 1 hour between overhauls, unfortunately Reaction Motors was bought by Thiokol and shut down. It burned LOX and anhydrous ammonia, but methane or LH2 would probably be a better choice for fuel. When the program was canceled they were working on a scramjet for the X-15; the nonfunctional but flyable prototype scramjet is in the museum at Wright-Patterson

The basic concept, an air-launched vehicle with all-liquid propulsion may be the best option if we are ever o achieve practical cost. It's still the only _fully_ reusable spacecraft ever built, since the SpaceShip I requires a new fuel tank and nozzle for each flight. Pegasus has demonstrated that air launch into orbit is perfectly feasible, and liquid fuel engines have significantly better performance in this application. Rutan's White Knight II demonstrates that a specialized carrier aircraft can launch a much larger orbital vehicle to altitude than a converted airliner or bomber of the same size.

The logical successor to the X-15 was the X-34, since an unpiloted but fully reusable vehicle would be much more practical for testing new technology than a manned craft. Unfortunately NASA canceled the X-34, and when Burt Rutan, the world's most famous aerospace engineer, offered to fly the X-34 prototypes with his own funds, NASA refused. As a result the prototypes, built with our tax dollars, are rusting and will soon be unflyable, if they aren't already. If there is _anybody_ reading this who can explain why NASA doesn't want the X-34's, the successor to the X-15, to fly, even at no expense to them, please let us know. There may be a good reason, but if so NASA has not revealed it.

 

[scottb50]

The X-15 flew 199 times, costing only about $6M/yr in later years, not much even then. Of course it had limited capacity and was suborbital, but that was 50 years ago.. . The engine could operate a remarkable (for a rocket) 1 hour between overhauls, unfortunately Reaction Motors was bought by Thiokol and shut down. It burned LOX and anhydrous ammonia, but methane or LH2 would probably be a better choice for fuel. When the program was canceled they were working on a scramjet for the X-15; the nonfunctional but flyable prototype scramjet is in the museum at Wright-Patterson

The basic concept, an air-launched vehicle with all-liquid propulsion may be the best option if we are ever o achieve practical cost. It's still the only _fully_ reusable spacecraft ever built, since the SpaceShip I requires a new fuel tank and nozzle for each flight. Pegasus has demonstrated that air launch into orbit is perfectly feasible, and liquid fuel engines have significantly better performance in this application. Rutan's White Knight II demonstrates that a specialized carrier aircraft can launch a much larger orbital vehicle to altitude than a converted airliner or bomber of the same size.

The logical successor to the X-15 was the X-34, since an unpiloted but fully reusable vehicle would be much more practical for testing new technology than a manned craft. Unfortunately NASA canceled the X-34, and when Burt Rutan, the world's most famous aerospace engineer, offered to fly the X-34 prototypes with his own funds, NASA refused. As a result the prototypes, built with our tax dollars, are rusting and will soon be unflyable, if they aren't already. If there is _anybody_ reading this who can explain why NASA doesn't want the X-34's, the successor to the X-15, to fly, even at no expense to them, please let us know. There may be a good reason, but if so NASA has not revealed it.

Comparing the White Knights capability to the Orbital L-1011 is like comparing apples to oranges. A 950 pound payload needs 51,000 pounds of vehicle and propellant to get to orbit, Space Ship 1 weighted 7920 and carries 400 pounds. I would be surprised if White Knight 2 could come close to carrying Pegasus, though numbers haven't been released for it.

Wasting the power to get to a speed to ignite scramjets as opposed to using it to get out of the atmosphere, then using the scramjet for a few seconds before a rocket has to be used to get to orbit pretty much rules it out. As far as a multicycle engine, turbojet, ramjet, scram jet rocket the complexity and propellant needed far outweighs the advantage of using a rocket to begin with.

Rockets actually have the capability to be a lot more reliable then combustion engines. The main failure areas are highspeed turbopumps and lack of control for solid boosters, both areas that can be dealt with fairly simply. Beyond that they can be reduced to basically a few on/off valves as opposed to high speed rotors and compressors needed now.

 

[vogon13]

IIRC (and we are going back a long way here), it seems the choice of LOX/NH3 for the X-15 engine had much to do with the fuel and oxidizer being rather close in density and this made maintaining the weight balance of the craft as the engines ran much simpler.

The 2 chemicals being cheap and plentiful probably did not hurt too much, either.

 

[halman]

scottb50,

Of course it will take a large aircraft to haul a vehicle nearly the size of the shuttle to 50,000 feet, but so what? I envision a wing about 100 meters across, powered by as many as 12 of the largest turbofan engines available. Probably, people will say, "It will never work." They said the same thing about the Boeing model 299, the prototype of the B-17. If you compare the B-17 to a 747, the B-17 looks tiny. People also said that humans would die if they were to travel as fast as a mile a minute, and that traveling through a rail tunnel a mile in length would be insufferable.

It is true that vertical launching is the most efficient way known to launch payloads into space, which is why we have been doing it that way. But the most efficient does not mean the cheapest, or the safest. And cheap and safe are what we need to make space travel a workable proposition. Taking off into space should be a simple, routine process, which only requires a few people.

But we will have to build aircraft totally different than what we are used to. The L-1011 is a swept wing aircraft, with a large cabin. Probably the only reason that it was chosen for launch the Pegasus was because they are available dirt cheap. The White Knight Two has a rated payload capacity af 17,000 kilograms, which is only 1,000 kilograms shy of the smaller of the two Pegasus variants, yet the White Knight Two is a heck of a lot smaller than an L-1011. But it was designed specifically for carrying weight to altitude, not for flying long distances at high speed, as the L-1011 was.

 

[scottb50]

scottb50,

Of course it will take a large aircraft to haul a vehicle nearly the size of the shuttle to 50,000 feet, but so what? I envision a wing about 100 meters across, powered by as many as 12 of the largest turbofan engines available. Probably, people will say, "It will never work." They said the same thing about the Boeing model 299, the prototype of the B-17. If you compare the B-17 to a 747, the B-17 looks tiny. People also said that humans would die if they were to travel as fast as a mile a minute, and that traveling through a rail tunnel a mile in length would be insufferable.

It is true that vertical launching is the most efficient way known to launch payloads into space, which is why we have been doing it that way. But the most efficient does not mean the cheapest, or the safest. And cheap and safe are what we need to make space travel a workable proposition. Taking off into space should be a simple, routine process, which only requires a few people.

But we will have to build aircraft totally different than what we are used to. The L-1011 is a swept wing aircraft, with a large cabin. Probably the only reason that it was chosen for launch the Pegasus was because they are available dirt cheap. The White Knight Two has a rated payload capacity af 17,000 kilograms, which is only 1,000 kilograms shy of the smaller of the two Pegasus variants, yet the White Knight Two is a heck of a lot smaller than an L-1011. But it was designed specifically for carrying weight to altitude, not for flying long distances at high speed, as the L-1011 was.

What you keep overlooking is once the rocket is released from the carrier plane it will take nearly the same amount of energy to get to orbit as it would if it was launched from the ground. The Tarus Orbital uses, replaces the L-1011 with a Castor solid first stage and, basically a Pegasus from there. 160,000 pounds launch weight 3,300 pounds to orbit.

 

[halman]

scottb50,

You are entirely correct that the amount of energy needed to get a payload into orbit from a velocity of 400 mph at an altitude of 50,000 feet is essentially the same as the energy needed to get a payload into orbit from the ground at a standing stop, and I am not overlooking that. What I am looking at is a design where motors do not need the ultimate in turbopump performance, or the most powerful fuel. Where the vehicle is able to accelerate at full throttle continuously from ignition until orbital velocity is achieved, and where the vehicle can be pointed down range instead of straight up at engine ignition. Most of all, I am looking at a way to get around launching straight up, because that contributes massively to the cost of space flight.

We have to use the highest performance possible to launch straight up, because gravity is working against us with all of its power. Every second we climb vertically, we lose 20 miles per hour. If we experience a failure, we will probably fall back on to the ground. To avoid failures, the ultimate in materials and engineering have to be used, and every possible aspect of the vehicle must be monitored continuously, before and during the launch. Because the motors are under so much stress, they must be completely taken apart and rebuilt after each flight if they are to be reused, a process which is very expensive. Even the slightest problem with any equipment can result in an abort, because performance is so critical.

I have advocated for a Big Dumb Booster in the past, and I continue to advocate for the same right now. However, somebody already does that pretty well, so I think that we should focus on what we have learned from operating the world's first aerospace plane, and build a system for getting the most important cargo of all, people, into space and to bring them back safely. Without having to call out the Navy every time somebody comes back. Without spending billions of dollars just to get up there and back. Until we can make the cost per pound of people going into orbit significantly less, space exploration is not going to do well.

What I have been purposing was possible 40 years ago, according to what the engineers working at NASA thought, because they are the ones who proposed it, more or less. I have added the refinement of the catapult so that the carrier wing does not have to be built strong enough to support the full payload at take-off. I figure that we can also save a little fuel by accelerating the several million pounds of mass the combined vehicle will certainly weigh with external help. It would be possible to get the wing moving at 100 miles per hour above its stall speed before the cradle would release it, which would insure that there was enough lift to begin climbing. And an abort does not mean a fiery crash, because the track could be long enough for the combined vehicle to be slowed down safely from take-off speed.

 

[vattas]

Rockets are launched straight up because they need to get above most of the atmosphere as soon as possible. If you immediately pointed downrange after liftoff, you will certainly loose more than 20mph because of the friction. Stress on the structure and other components will be much much greater than when climbing straight up until you get out of atmosphere and then pointing downrange.

 

[halman]

At 50,000 feet, you are already above about 3/4's of the atmosphere. Heading down range with a small angle of elevation at 2 gravities will boost the vehicle in altitude as the Earth curves away beneath it.

Most rockets turn downrange soon after take off, but only a little.