For most of the development of the Space Shuttle, until very near the point where the final design was chosen, it was just accepted that the Shuttle would be a two-stage fully reusable vehicle, with the first stage being a manned “Flyback” booster, equipped with wings and jet engines to return it to the launch site for quick and easy refurbishment and re-launch. The Orbiter itself would be equipped with internal propellant tanks, so there’d be no need to drop the External Tanks into the Indian ocean. On the whole, the concept certainly didn’t lack the coolness factor. Here, for example is one of the North American concepts, with two different Orbiters:
What’s not to love? While some of the boosters designs were dishwater-dull, being little more than basic rockets with wings, this NAA concept was an elegant design of blended surfaces.
In the end, of course, NASA went with the SRB’s. The official reason given was that they knew that a flyback booster would be operationally cheaper than the low-efficiency SRBs which needs to be fished out of the ocean and refurbed after each flight, but the SRBs would be cheaper to develop and could fly sooner with a Shuttle with an External Tank. This being the early 1970s, “Cheap Now” won out over “Cheap In The Long Run.”
There was, however, another reason why the flyback boosters were bypassed. They weren’t going to be just expensive to develop… it was becoming apparent that they were going to be NIGHTMARES to develop. They would essentially be subjected to roughly the same speeds and heating rates as the X-15… but would be bigger. The flyback booster is big. Really big. You just won’t believe how vastly, hugely, mindbogglingly big it is. I mean, you may think it’s a long way from nose to tail of a 747, but that’s just peanuts to flyback boosters, look:
The fuselage is several times the size of that of a 747, but the wings are quite small; this is made possible by the fact that the vast bulk of the flyback booster was empty space. Even so, it would have been an enormous vehicle, with a vast surface area.
The Space Shuttle, even after the SRB option was selected, was sold as being a $50 million per flight design, which could be turned around in two weeks by a reasonable number of technicians. And we all know how *that* turned out. I shudder to imagine what maintenance on the flyback booster would have been like.
I have no doubt that a vehicle like this could be designed, built, flown and put into service. I have no doubt that a vehicle like this could be made cost effective and reliable. I have no doubt that had they tried this in the mid-1970’s, it would have either failed, or been a catastrophically expensive hangar queen. That might have spelled the death of manned NASA flights by the mid 1980s… or it might have led to a truly cost effective manned space launch system by the late 1980.s Who knows. As it turned out, the Space Shuttle we actually got was far too expensive to be actually useful, but not so fantastically expensive that the government would easily give it up. Sometimes you need a truly massive financial disaster to cause a complete rethink.
16 Responses to “This is why we don’t flyback”
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Add that it was impossible even to think and develop a fully reusable shuttle with flyback booster with the amount of money NASA was budgteted in post-Apollo era. The SRB-external tank configuration was the only way to have a shuttle with that payload. A smaller Shuttle with lower (much lower, in the region of 9 tons) payload and shorter (much shorter) bay could have been built without a flyback booster and being fully reusable ((SRBs and internally placed tanks) But NASA, having lost the space station in 1970 had to justify the Shuttle as an universal space carrier.
I thought the between-flight inspections and maintenance would be complete mess also; there’s just too much surface area than needs to be looked at for any sort of damage; also if you get the sped high enough ( Faget’s fly-back boosters were going to get to Mach 12-15 IIRC) you would have a very hard time reversing course and returning to the launch site, so the fly-back booster might well end up on the eastern side of the Atlantic on each flight and have to fly back home again minus the upper component.
Figuring put what the heating and structural loads on the booster would be like as it returned to the atmosphere after releasing the upper component would be fun; it might come in like at a pretty steep angle like the Mercury capsule when it was Redstone launched, and those pulled pretty severe g’s, meaning a heavy structure would be needed for strength, even if you kept heating down to where titanium and Inconel could handle it.
If Dyna-Soar had continued as originally planned, maybe there would have been at least a small body of data about the actual post-reentry condition of a good-sized winged orbiter, and maybe it could have influenced some decisions about Shuttle in its design phase. This is assuming they would have gotten a few orbital flights in by the end of the 60s anyway. Maybe they would have realized that what they were proposing as far as fast, easy Orbiter turn-around was unrealistic. Dyna-Soar might have turned into a development system for the Orbiter, helping to solve some of the tile issues.
A guy can dream, anyway.
That’s exactly what I thought; Dyna-soar should have been continued to the flight stage not because of any military mission for it, but to see how the whole concept of a reusable aerodynamic space vehicle would work out economically in practice in a man-hours and maintenance sense.
I only very recently found out that the FDL-5 Lockheed spaceplane had gotten to the stage of sub-scale and full-scale airframe component manufacture, using columbium as a structural material, like the X-20 was going to do: http://picturetrail.com/sfx/album/view/23272850
(Scroll down the photos on the left side of the page; it looked like they were a lot more comfortable with flat sheet or sheet curved in only one dimension than any sophisticated three dimensionally formed structural pieces.)
This gave it a shape reminiscent of Krafft Ehricke’s space shuttle designs:
http://www.ninfinger.org/models/kitplans/revellh1828.html
Which not only looked great from a skin heat expansion point of view, but looked like it had F-117 style faceted stealth incorporated in its design.
It’s an excellent concept. Maybe in about 20 or 30 years from now, we will see this become reality.
Did anyone consider a lifting body combined with a flying wing?
Boeing and NASA has something in the works along that line.
Any links to pictures.
Is it safe to assume the technology for an unmanned flyback booster wasn’t considered achievable at the time? (Sometimes it’s difficult to keep in mind that microprocessors didn’t always exist.)
Offhand, I can’t think of any flyback booster designs from that era that *weren’t* manned.
Scott,
I don’t know that I agree.
Mach 6 is fast for metals, but not particularly so for thermal blankets and lightweight tiles not actually normal to the airstream and a compression shock. Tthe sides of the existing orbiter and the OMS pods are examples.
In addition there is a LOT of thermal mass to work with, nearly 500,000lbs dry mass could suck up an immense amount of thermal energy.
I’d be more concerned about impinging shocks between vehicles, and fratricide among the booster engines.
> Mach 6 is fast for metals, but not particularly so for thermal blankets and lightweight tiles not actually normal to the airstream and a compression shock.
Sure… but now you’re back the the tile maintenance nightmare, even if the tiles are less stressed than on the Orbiter.
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Sorry to necropost, but there was this Shuttle orbiter concept that seemed to be very wide and not very long, looking like a wide venetian blind segment.
How conpact would the shuttle stack have been if they had went all hypergolics, and how big would the ET have been?
Nice article.
But I also feel that the booster may not need to be that big, everything else can still stay as what space shuttle is, with a disposable external tank, etc. And in reality, the solid rocket boosters aren’t too big, and only boost the orbiter to less than mach 5 before separation.
I hope the new DARPA xs-1 project can really turn into something.
> the solid rocket boosters aren’t too big
But they are *far* denser than the liquid hydrogen in the flyback booster. Less dense = smaller.