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Why didn't the space shuttle solid rocket boosters have wings and tires to land the same way the orbiter lands? I don't think they haven't thought of that so there must be something that led them not to choose that design, right?

Nathan Tuggy
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ALz
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3 Answers3

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Wings, engines to fly back to the launch site, and landing gear are heavier than parachutes. Using this design on the SRBs could have resulted in a significant payload to orbit reduction (every 10 pounds added to the SRBs resulted in 1 pound less payload that could be carried to orbit).

However, this was studied for the case of liquid fueled flyback boosters. Another interesting shuttle upgrade that never went through. And, resulting in a crew member comment "I guess we would be 3rd in line for the runway if we had to do an RTLS."

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Organic Marble
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  • Two questions: 1) "to orbit reduction" I didn't get that part (not a native speaker) can you explain pls. 2) What was the reason the design didn't go through? Budget? – ALz May 01 '17 at 20:13
  • Good point on the first, edited answer to give details and a reference. For the second, yes, the shuttle system was never quite bad enough to invest the money for a major upgrade. – Organic Marble May 01 '17 at 20:16
  • Did they consider the other design before creating the original space shuttle and the weight concern you mentioned was their excuse? If yes, could using bigger, more thrust generating multi-stage boosters solve the problem? – ALz May 02 '17 at 00:10
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    See Russell Borogove's answer but yes, the original shuttle proposal was for a fully reusable system where the shuttle orbiter launched on a giant reusable manned flyback booster. When NASA was told they had only $4 billion for development, they changed the design to the expendable tank and refurbishable SRBs (increased operations cost, lower development cost). The flyback LRBs were a later proposal to make the existing system more reusable, only the tank would be expended. – Organic Marble May 02 '17 at 00:14
  • As well as the additional weight - wouldn't the wings increase drag, slowing ascent, and requiring more fuel to achieve orbit (more fuel on the pad again reducing payload). – HorusKol May 02 '17 at 02:59
  • Could well be. In the first graphic, it looks like the LRB wings might be folded at launch, perhaps to mitigate the issues you mention. – Organic Marble May 02 '17 at 03:16
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    Agreed on the third in line quote, that's priceless :) and @ALz, to answer your question about to orbit reduction, that's just a sentence fragment - the meaning can be understood better if you read it as a whole: could have resulted in a significant payload-to-orbit reduction, rephrasing for clarity would give us it could have resulted in a significant reduction in what payload could be lifted into orbit. – flith May 02 '17 at 10:45
  • @HorusKol: Hm.... the Shuttle throttled back at about 30 seconds after liftoff to deal with "max Q" (maximum aerodynamic pressure), then throttled back up at about 60 seconds. Which means, after not even a minute you were rapidly getting to altitudes where atmospheric drag becomes a non-issue. I'm not sure those comparably small wings would have mattered that much in those few seconds. But I'm neither a rocket scientist nor that good at math. ;-) – DevSolar May 02 '17 at 13:05
  • The wings on the orbiter itself had to be factored into ascent trajectory designs; the stack had to fly at a negative angle of attack till about Mach 2.2 to stay near the wing's zero-lift angle. It's true that you gain altitude quickly but such things are still a consideration. – Organic Marble May 02 '17 at 13:08
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    With all new liquid fueled boosters there would be no reduction in payload capability; the new boosters would provide more total impulse than the original SRBs, canceling the drag losses. – Russell Borogove May 02 '17 at 13:54
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    It's, let us say, interesting? ...that the flyback booster proposal handwaves away the development of a large RP-LOX staged combustion engine properly sized for the booster. – Russell Borogove May 02 '17 at 14:00
  • @RussellBorogove in the graphic I posted, the engines on the LRBs appear to be smaller than the SSMEs. In fact they look kind of Musk-y in their number and size. However, I don't know where I got that picture from any more. There were a lot of different flavors of LRB proposals over the years. I remember having to scope one for the simulator at one point, but it was not even mature enough to say if it were to be pump or pressure fed. – Organic Marble May 02 '17 at 15:21
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    You'd need to scale up the Merlin about 2x. The Boeing proposal calls for 4x 900klbf engines per booster at 340s Isp which might as well be a flashing sign reading "RD-180". – Russell Borogove May 02 '17 at 15:39
  • The graphic seems to have at least 8 engines per LRB. Could be total BS artist conception, of course. – Organic Marble May 02 '17 at 15:41
  • About the "3rd in line" comment - given that the flyback LFB(s) would have had their own jet engines and been in powered flight, couldn't they have been diverted to a different landing site(s) (Jacksonville, Miami, and Orlando come to mind) if the orbiter had to perform an RTLS? – Vikki May 31 '18 at 17:53
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    I don't think it got far enough for that kind of detailed planning. Not sure that commercial airports were set up for robot boosters in the pattern back then though. Plus - it was a quip. – Organic Marble May 31 '18 at 18:09
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    A year late, but RD-180 is a two nozzle engine, so four of them would get you 8 nozzles. Your illustration looks pretty similar to the ca 1998 Lockheed Martin proposal. – Russell Borogove Jul 21 '18 at 18:45
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In addition to the booster upgrade proposals that Organic Marble mentions, some early shuttle proposals considered using a single large liquid-fueled winged booster that would fly back to the launch site. The development budget for the shuttle didn't allow that strategy to be pursued.

http://www.nss.org/resources/library/shuttledecision/chapter08.htm

Russell Borogove
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It's all about trade-offs. Parachutes are much simpler, lighter, and safer for recovering a "dumb" booster. Wings, landing gear, and control systems add an awful lot of weight (therefore reducing payload) and complexity for pretty much zero return on investment. I also imagine there would've been all kinds of stability problems from adding two extra sets of side-mounted wings to the stack.

PHChilly
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