fisher@dvinci.DEC (Burns Fisher, MRO3-1/E13, 231-4108) (04/20/84)
NO! There is absolutely no fuel left on board for the SSMEs (Space Shuttle Main Engines) after the ET (External Tank) drops. The SSMEs are not started again until the next launch. As a sanity check on this assertion, think of what you would have to do to save any reasonable quantity of liquid H2 and liquid O2. (Insulation, high pressure tanks, etc etc). Also think of how little energy is actually required to start the reentry process as compared to the amount required to get up into orbit to begin with. Using the SSMEs for deorbit does not make sense! Here are the major engines on the shuttle and their acronyms (in order of power): SRBs (Solid Rocket Boosters) - millions of pounds thrust. Used only during first (1.5?) minutes after launch, then dropped off and recovered. SSME (Space Shuttle Main Engines) - 10**5s of pounds thrust. Used from launch until just before orbital insertion. Draws fuel from ET (external tank) which is dropped just after the SSMEs stop. Not used again until the next launch. OMS (Orbital Maneuvering System) - 10**3s of pounds (?) thrust. Used to insert the shuttle into a reasonable orbit after the SSMEs stop. (OMS-1 and OMS-2 [OMS-1 was omitted during the last mission, because of the unusual trajectory/burn time planned for the SSMEs-required for the unusually high orbit]) Also used for orbital changes during the mission (e.g. rendezvous etc.), AND FOR DEORBIT BURN (retrofire for us old-timers). RCS (Reaction Control System) (isn't every rocket?). - Small thrust. Used to change or maintain orbiter attitude while on orbit. Also can be used to make small orbital corrections for station-keeping or final phases of rendezvous. Also used during the early phases of reentry for attitude control in various combinations with the control surfaces depending on the thickness of the atmosphere. RMS (Remote manipulator system). The "robot arm". Not an engine. Burns (picky picky) Fisher <Is this coming close to being a flame? Sorry...> UUCP: ... {decvax|allegra|ucbvax}!decwrl!rhea!dvinci!fisher ARPA: decwrl!rhea!dvinci!fisher@{Berkeley | SU-Shasta}
mat@hou5d.UUCP (04/21/84)
I believe that the SRB's each generate about 2.7 million lbs (what's that in Newtons?) of thrust. The three ``main engines'' contribute about another 1.4 million lbs. Total: A little over 7 million lbs. This is assuming the second generation SRBs and the 104% thrust liquid engines. Compare this with the Saturn V used on the last moon shot. Total thrust from five engines: about 7,780,000 lbs. The center engine was either a little more or less powerful than the others in order to avoid both excess stress to the structure of the booster and a troublesome reverse-direction gas flow under the booster. The main booster and second stage put 300,000 lbs in earth orbit! We've got to take the shuttle a bit further before it will be really ready to pave the way into space. -- from Mole End Mark Terribile (scrape..dig) hou5d!mat ,.. .,, ,,, ..,***_*.