This question got me thinking, would the Space Shuttle have been able to use its main engines to roll up to speed and take off horizontally like an airplane? (I'm not asking about getting to space, just flying around) What would the take off be like? What would forward flight powered by the main engines be like?

Did the space shuttle even carry fuel for the main engines internally? Before posting this question, I tried to find the answer myself, but I've had trouble finding any mention of it, only talk about the external tank. It seems to me you might want to have at least a little, just in case. If it did carry fuel, how long might it be able to fly for that way?

Would there have been anyway to put a usable fuel tank in the cargo bay?

(I realize that this will mostly be speculation, just asking for fun, if that's frowned upon, please let me know)

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    $\begingroup$ Buran did, but it didn't have the main engines, and required external ferrying jet engines for the trick. $\endgroup$ – Zeiss Ikon Oct 2 '19 at 18:17
  • $\begingroup$ Indeed, in terms of capability of the basic planform, the Buran atmospheric test article could take off with the added jet engines. Also interesting to note if you look at the picture at en.wikipedia.org/wiki/OK-GLI that the nose gear strut is longer creating a positive angle of attack on the ground, not just compared to the shuttle's which is short, but compared to the spacecraft version of the Buran which seems to sit level on its gear. $\endgroup$ – Chris Stratton Oct 3 '19 at 18:41

Despite the scene in Moonraker the Shuttle orbiter carried no fuel for the main engines.

Further, the orbiter sat nose down on its landing gear, lacked the elevator authority to raise the nose off the ground at landing speed, and could not retract its landing gear (it used a straight-fall gravity deployment). The OMS didn't have enough thrust or delta-V at sea level to accelerate the orbiter from a stop to flight speed, even without the pitch authority issue.

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    $\begingroup$ Thank you. I did wonder about elevator authority. Assuming there was fuel for them, I wonder if gimbaling the main engines would be enough to get the nose up. $\endgroup$ – notloc Oct 2 '19 at 18:35
  • $\begingroup$ They're set at a pretty high offset angle to counter the off center External Tank anyway -- I think the question might be whether you could avoid them just flipping the orbiter without that mass. They were okay just before cutoff, but adding fuel mass in the cargo bay might "tip" things... $\endgroup$ – Zeiss Ikon Oct 2 '19 at 18:40
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    $\begingroup$ Can you cite a source for claiming that using OMS in the atmosphere was considered? $\endgroup$ – Bret Copeland Oct 2 '19 at 19:31
  • $\begingroup$ @BretCopeland Not offhand. Shuttle Down came out well before the Challenger disaster -- the Shuttle may not have even been flying yet -- and additional planning on the part of NASA or pilots would have been done in the early 1980s. I do recall reading G. Harry Stine (aka Lee Correy) writing that he'd spoken to shuttle pilots about the possibility. $\endgroup$ – Zeiss Ikon Oct 2 '19 at 19:36
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    $\begingroup$ Assuming that story is accurate, a science fiction writer having a conversation with some shuttle pilots about a hypothetical is a far stretch from "there were contingency plans". I'm very skeptical that NASA ever considered using the OMS in the atmosphere. The thrust to weight ratio is very low and there's very very little fuel left at the end of the mission. If they did consider it, I'd love to know about it, but without a source, it doesn't feel credible. $\endgroup$ – Bret Copeland Oct 2 '19 at 23:05

The cargo payload capacity of the Shuttle is about 22 tonnes when external tank weights 760 tonnes when full and is used up in 8.5 minutes. Hence it would be enough fuel for 14 seconds of flight. The thrust of the single engine, RS-25, 1860 kN, is more than three times that of the 777's GE90, 513 kN. Hence for 14 seconds we have near 5 times more thrust for about 2,5 times lighter machine (110 t vs 247 t). Hence I think it could take off and then glide while of course not into space. It would fly more like WW2 ME 163 Komet. It also may need adjustments of flight control surfaces as such flight is very different from that it usually does.


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