What percent of the total available fuel onboard the space shuttle, external tank, and rocket boosters was required to launch and get the space shuttle into orbit? Or phrased another way, what percent of the initial fuel load was left for maneuvering and reentry?
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1$\begingroup$ I would say, based on your alternative phrasing, that 0% of the external tank and booster were available for maneuvering and reentry, simply because they're jettisoned during/after launch. But then again, that's probably not what you're getting at. $\endgroup$– SteveJan 14, 2017 at 11:38
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$\begingroup$ They were jettisoned when empty (tank), or burned out so far they'd have less than 1 own TWR (weigh the stack down instead of propelling it) - boosters. The shuttle would finish circularizing using on-board hypergolics but I'm not sure how much it used up that way vs what remained for maneuvers. $\endgroup$– SF.Jan 14, 2017 at 15:09
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$\begingroup$ The percentage would be silly small simply due to the original fuel load being pretty large. Remember that the SRBs totalled over 1100 tons, plus well over 700 tons of fuel in the external tank, and compare this to the weight of the entire orbiter including its on-board fuel of about 110 tons. The entire orbiter is about 5.5% of total mass at ignition, and only a tiny fraction of the orbiter mass is fuel. $\endgroup$– userJan 15, 2017 at 15:44
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The Shuttle had three propulsion systems:
- the solid rocket boosters (SRB), mounted at the side
- the main engines (SSME), mounted in the orbiter and fed from the external tank
- the orbital manoeuvring system (OMS), mounted in the orbiter and fed from tanks inside the orbiter
During launch, the SRBs were fired until they burned out, and the SSMEs were run until the external tank was almost dry. The SRBs were still generating a minute amount of thrust when they were dropped, but we can effectively assume 100% fuel usage.
The external tank still had a small amount of fuel in it when it was dropped, because it was safer and more controllable to shut down the main engines rather than let them run dry. I don't have a figure to hand, but I suspect this would be <1% of the total fuel mass.
After this point, the SSMEs played no further role in the launch. The Shuttle was still on a suborbital trajectory (or a highly elliptical orbit), and the OMS was used to perform the final orbital insertion burn.
I'm finding it difficult to nail down an exact figure (it would depend heavily on mission profile and payload) but Jenkins' The Space Shuttle (2001 ed, p. 390) suggests an average of about 500fps of fuel was used during ascent, out of a total of 1000fps.
So in total - 100% (or effectively 100%) of the SRBs and external tank, and ~50% of the OMS fuel carried in the orbiter.
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1$\begingroup$ The delta V you mention for orbital insertion seems way too high. This answer will point you to a document that gives the delta V for most of the orbital insertion burns for the shuttle missions. space.stackexchange.com/questions/18030/… $\endgroup$ Jan 14, 2017 at 13:49
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$\begingroup$ Hmm, high but plausible for some flights - eg STS-58 had 398fps on the OMS burn, plus a bit for adjustment during ascent. But you're right it looks like way more than most flights would need. I wonder why the book quotes such a high number; perhaps 500 is the amount generally reserved for launch? $\endgroup$ Jan 14, 2017 at 14:05
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$\begingroup$ Could be. That's a great book but maybe better on history than ops (although I have an older edition). $\endgroup$ Jan 14, 2017 at 14:12
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$\begingroup$ OMS deorbit burn was "usually" 200-550 ft/s according to the Shuttle Crew Operations Manual. space.stackexchange.com/q/12011/415 h/t to Organic Marble for the citation there. This is the absolute minimum you'd want to leave in the OMS tanks. Add to that a bit of maneuvering during the on-orbit mission and if the total OMS tankage was 1000 ft/s you are looking at anywhere between 250 and 700 ft/s available for final orbital insertion during ascent. Remember that OMS was used to maneuver away from the ET. $\endgroup$– userJan 15, 2017 at 15:41
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$\begingroup$ Actually, the RCS (reaction control system) was used to fly away from the ET. Its down-firing jets were much better suited for this task than the aft-firing OMS. $\endgroup$ Jan 15, 2017 at 16:32