Air Force Wants Reusable Fly-Back Rockets 94
FleaPlus writes "The Air Force is initiating a pathfinder program to develop a first-stage rocket booster capable of gliding back to a runway so it can be easily reused. Lockheed Martin has already launched a secretive prototype, and a Cal Poly team has a prototype based on Buzz Aldrin's Starcraft/StarBooster design (video). The Air Force estimates such a booster could cut launch costs by 50% over the current Atlas 5 and Delta 4 rockets, and could also offer a rapid surge/replacement capability if combined with reusable spacecraft like the recently launched X-37B. Initial test flights are planned for 2013."
Re:Sensible (Score:3, Informative)
The shuttle was originally designed to be a full piggyback system. They just wouldn't fund it.
This idea has been around for a long time (Score:5, Informative)
Boeing did a study of making a winged Saturn V first stage back in 1962.
http://www.astronautix.com/lvs/winturnv.htm [astronautix.com]
The payload penalty might be problematic. Also, you can't really cluster more than 2 flyback stages due to the size of the wings. If you could use a parafoil and land with skids, that might solve that problem and to be fair western rockets don't really use clustering (Delta IV Heavy being a notable exception).
Re:Sensible (Score:1, Informative)
Not right now. SSTO with chemical rockets is just plain impossible. Weight-to-payload ratio is murderous.
It's funny, it seems to depend on who's running the numbers whether SSTO is "plain impossible" or not.
Jerry Pournelle has run the numbers and contended for decades that an SSTO with a liftoff weight of about 600,000 lbs should be able to make orbit, maybe. The problem being that whether or not it makes orbit and how much payload it can carry is in the noise, that we can't tell until we build one and try it. DC-X was to be the predecessor of a full scale test vehicle.
Dr Pournelle may not be a rocket scientist himself, but he knows a lot of rocket scientists and he's smarter than me and, probably, you. So I'd say it's worth a shot.
Having said that, my understanding is that he agrees that 2STO may be more practical in the short term.
Big Differences (Score:3, Informative)
I think it would be a mistake to assume that. An orbital ship isn't fundamentally any more complicated than a passenger jetliner.
They're vastly different, not only in terms of what's under the skin (specially engineered components, ultra-hazardous chemicals, etc), but also in terms of economics. Jetliners are designed from the outset to be economical enough to make a profit, not to exceed physical performance goals. If Boeing can't make a jet that makes money for other people, then they drop the project, even if it's interesting. See the Sonic Cruiser for the latest example in a long line of them.
Private companies, by contrast, are just now taking the same approach to building rockets. And since NASA is a government agency... they're not concerned with profit at all.... then their priorities are performance and technical achievement. Cost has always far down on the list of NASA's priorities. Their in-house slogan during the Moon Race was, after all, "money is no object, but time is of the essence".
When NASA says that they're building something with economy in mind, they always fail in some way, because they don't really have the same kind understanding about economy as a business that lives and dies by profit. This is the main reason, even more than politics, that the Shuttle became so expensive, and why the Clinton Era "better, faster, cheaper" programs had so many spectacular failures.
I'm a big proponent of SSTO
I love the idea of SSTO, but it's the spacefaring equivalent of Cold Fusion; a modern day pipe dream at current technology levels. Lockheed couldn't even get it to work with the X-33, let alone with the VentureStar it was supposed to spawn.
Re:Sensible (Score:3, Informative)
G-forces in orbital space flight are not as problematic as you seem to think. Space Shuttle launch and reentry is generally 2-3 gravities (more for astronaut comfort than out of any actual safety concern). Everything from high-performance aircraft to race cars experience far more than that on a routine basis.
The forces are also largely predictable and steady. We know when they'll happen and their direction, and their buildup is gradual rather than a shock, making engineering for them quite easy.
There are lots of things about space flight that are difficult, dealing with the g-forces just isn't high on the list.
Re:Sensible (Score:3, Informative)
The issue here is that in the first second of a rocket launch, the thrust of the rocket pushes the empty rocket and all the fuel, while in the middle of the flight the thrust of the rocket pushes the rocket and half the fuel. For the last 10% of the flight, the thrust pushes forward the rocket and 10% of the fuel.
Now, if we separate the last 10% of the fuel in a detachable rocket with only 10% of the mass of the total launch vehicle, we don't end up with 100% of the speed of the launch vehicle but with 90% of the speed and a new, small vehicle with full fuel (allowing maybe another 70% increase in speed).
Until the mass of the launch vehicle is a very small part of the mass of the fuel, SSTO won't be as efficient as multi-stage rockets.
Re:Simple (Score:5, Informative)
Sort of like Formula One motors. No one reuses them. Why not? No one cares. You build them. You use them, they wear out after 20 hours, and you build another one. Simpler, cheaper, better.
SpaceX regularly test-fire their engines with full mission-duration burns, then use the same engines on their launchers. Their engines are designed for re-use, to the extent of avoiding ablative coatings and materials wherever possible. They've even been careful to design for immersion in salt water so that in theory they can recover first stages, give them a quick going over, and whack them back on the launch pad.
As someone who works in the space industry, I think that saying, "You shouldn't reuse rockets," is a rather blinkered and negative attitude. With that sort of stance, how could we ever improve the state of the art?