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Langley single-stage-to-orbit launch. The NASA/Langley Research Center's "Future Space
Transportation System" study commenced in October 1981. Its goal was to define a successor to
the Space Shuttle; the new system was to become operational in 2005. Previous Langley studies
had mostly focused on rocket-powered single-stage-to-orbit VTHL and HTHL systems that would
have mostly the same capabilities as the current Shuttle, i.e. a 29.5t payload capability and
18.3m x 4.5m cargo bay size. The FSTS however assumed the new vehicle would be larger; 68t to
LEO (27m x 6m diameter envelope). Missions included future space station (486km, 31 degr.
orbit) & space tug support in 2005-2020; about 57% of the total payload mass was expected to be
propellant. The projected flight rate was 15-38 missions per year using 2-4 vehicles, and the
transportation cost goal was <$150/lb. The projected total life-cycle cost (based on 1980
Space Shuttle projections of $45M/flight) would then be $8.4 billion [1980 $] and the cost per
flight = $22.6M.
The FSTS study concluded that TSTO+advanced technologies produce a much smaller vehicle than a
single-stage-to-orbit system. Operational considerations and minimum weight requirements forced
the designers to settle for a smaller external, encapsulated payload pod rather than a
Shuttle-type internal cargo bay. Small wingtips on the orbiter work better at supersonic speeds
and weigh less than a traditional vertical tail. Parallel staging+propellant crossfeed were
introduced to reduce the length of the TSTO, simplify the mating process, reduce axial loads on
the booster and reduce the total number of engines. The main drawback is significant lateral
movement of CG as the booster's tanks are depleted, so the engines require a large gimbal
range. Staging at Mach 3 works best since the booster needs no thermal protection or auxiliary
propulsion (which otherwise would increase the dry mass by 9%) to return to the launch site.
Thrust: 28,150kN(s). Total Mass: 2222.6 tonnes. Total Length: 57.3m.
Payload capability: 68,000kg to a 31 degree 486km orbit; Payload bay: 27m x 6m diameter.
Stage 1 : 5 x 2,830KN thrust hydrocarbon engines. Liftoff thrust: 14,150 KN. Isp: 355s [vac.]. Gross Mass: 975,223kg. Empty Mass: 76,657kg. Length: . Width: . Propellants: LOX/kerosene.
Stage 2 : 7 x modified SSME. Liftoff thrust: 14,000 KN. Isp:465s [vac.] . Gross Mass: 1,246,000kg. Empty Mass: 130,181kg. Length: 57.3m. Span:45.4m. Propellants: LOX/LH2.
"FSTS Study" -- Freeman et al, Astronautics & Aeronautics, 1983/June/p.38
"Future Space Shuttle Design Under Study" -- Space World, 1984/January/p.18