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Airbus Unveils Its First Stage Reuseability Concept
schwit1 writes: The competition heats up: Airbus unveiled Friday its prototype design to recover and reuse the engines and avionics of its Ariane rockets. From the article: "The Airbus team concluded that SpaceX's design of returning the full stage to Earth could be simplified by separating the propulsion bay from the rest of the stage, protecting the motor on reentry and, using the winglets and turbofans, return horizontally to a conventional air strip. "We are using an aerodynamic shield so that the motor is not subjected to such high stress on reentry," [technical director Herve] Gilibert said. "We need very little fuel for the turbofans and the performance penalty we pay for the Ariane 6 launcher is far less than the 30 percent or more performance penalty that SpaceX pays for the reusable Falcon 9 first stage." Gee, for decades Arianespace and Boeing and Lockheed Martin and everyone else in the launch industry insisted it made no economic sense to try to recover and reuse the first stage of their rockets. Then SpaceX comes along and makes an effort to do so, without as yet even coming close, and suddenly everyone agrees it is economically essential to do it as well. Isn't competition wonderful?
Why reuse something when you can trick governments to pay for it again. That make perfect economic sense until someone reveals the fraud.
Silence is a state of mime.
The idea that SpaceX "did not even come close" is ridiculous. It was the FIRST to operate on the principle that it was practical, and has twice now come very close to getting it done. In only... what... 4 tries? On a target far smaller than the continents aimed at by Russia and EU?
I find this whole announcement to be saying: "Yeah, us too! Maybe a few years from now."
So its basically the Vulcan concept, a detachable avionics/engine package at the back and an expendable everything else. I suppose its an improvement from what we currently have but not by much. The only real difference from Vulcan is that instead of being snagged out of the air by a helicopter it glides back to some location under some power. I suppose I can see why Airbus and ULA are going for such concepts, they should be pretty cheap to develop (though I am sure they'll try to squeeze every dollar they can out of their respective benefactors), are relatively low risk and will still let them justify big launch bills with tank/upper stage replacement. But if SpaceX can pull off a Falcon first stage recovery even a majority of the time they'll blow this and Vulcan out of the water. Fuel is cheap, replacing tanks and stages is expensive.
This has the look of a paper concept that nobody's put any engineering work into yet. Some possibly show-stopping engineering challenges:
1) The air-breathing engines are dead weight dragged most of the way to orbit. And turboprops and turbofans are pretty damned heavy compared to rocket engines: for many applications, the weight of fuel and tankage is so much greater than the engines that engine mass is irrelevant, but that's not the case here. SpaceX's design makes use of engines that need to go to space anyway.
2) Looking at the videos, the design relies on folding propellers that deploy in flight. This is ... not an easy thing to do. I'm not aware of any aircraft larger than a duck that uses this technique, even on carrier-based aircraft where space is at a premium.
3) While rocket engines are pretty lightweight compared to turbine engines, it's still a lot of weight to fly back home. The video shows a flyback aircraft with very short stubby wings. In addition, the wings can't be asymmetric lifting airfoils or they'd push the rocket sideways during lauch: the have to be flat boards. The return vehicle is likely to have a very high stall speed, making landing a challenge.
4) The video shows no details on how this propulsion module is attached to the fuel tank above it. This is difficult: enormous fuel and oxidizer pipes need to pass through the nose of the propulsion module, along with gigantic clamps attaching it to the fuel tank... but this surface is exposed to re-entry heating on the flight back. How do you route plumbing and avionics through your heat shield?
"The Airbus team concluded that SpaceX's design of returning the full stage to Earth could be simplified by separating the propulsion bay from the rest of the stage, protecting the motor on reentry and, using the winglets and turbofans, return horizontally to a conventional air strip."
Interesting definition of "simplified" they're using. They're not even recovering the entire first stage, and they're basically bolting a jet airplane onto it to achieve that much. Propellant is as cheap as dirt, they're avoiding paying tens of thousands of dollars in propellant by instead paying for jet aircraft maintenance and operations and an entirely new set of cryogenic tankage and a substantial amount of aerospace vehicle structure for each flight. SpaceX is just making the first stage a bit bigger (and looking at things like additional propellant chilling to increase density) so it has the extra capacity required.
"We are using an aerodynamic shield so that the motor is not subjected to such high stress on reentry"
Thus solving an issue that SpaceX has already shown isn't actually a major problem...they have been regularly bringing entire intact first stages through reentry and down to sea level for some time now.
As for SpaceX not "coming close"...their second attempt actually brought the vehicle to a halt on the landing pad, though with mangled landing gear, and the reasons for the control issues during the final burn are well understood. They are extremely close...odds are quite good that their third attempt (in a bit under 2 weeks) will be a success.
That's my point. Progress happens in all fields of engineering, but computer engineering happens at such a radically different tempo that it's not a useful comparison.
Space, as it turns out, is really hard. There are two basic kinds of techological miracle: working with microscopic quantities of matter and energy, and working with vast amounts. Science fiction authors of the '60s assumed that mega-scale engineering would continue at the incredible pace set during the 20th century, but it turns out we were just getting to the hard part. But they drastically underestimated what we'd be able to do with micro-scale engineering.