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A RETURN OF THE SPACE SHUTTLE ?

Previous Langley studies have mostly focused on rocket-powered single-stage-to-orbit VTHL and HTHL systems that would have mostly the same capabilities as the 1971 Shuttle, i.e. a 29.5t payload capability and 18.3m x 4.5m cargo bay size. Increasing space capabilities and the inevitable industrialization of space will place an even greater traffic demand on the Shuttle II than first projected. The Shuttle baseline concept will be upgraded by evolutionary steps.

System-level studies vehicles have been conducted by NASA under the name Future Space Transportation System (FSTS). FSTS began in April 1981 with the objective to define a launch-vehicle concept which improves space transportation capabilities and economics. A second aim was related to the projection of technology requirements beyond previous studies, especially in the areas of structures, propellant tankage, thermal protection, aerothermodynamics and operation.

The configuration chosen for the study is a two-stage, fully reusable, vertical liftoff, and horizontal landing system with a 150,000 lb. payload capability. The two stages are burned in parallel with the booster providing all the propellant until staging, which results in a large lateral c.g. movement. Nominally, the booster stages at Mach 3 and glides back to the launch site. Because of the large lateral c.g. travel, a scheme to trim the vehicle until staging occurred was developed that used both gimballing and throttling of the engines. Preliminary booster aerodynamics were determined, and the booster glideback trajectory was analyzed with and without winds. Finally, a preliminary abort analysis was conducted for each stage.

The FSTS however assumed the new vehicle would be larger; 68t (150 000 pounds) to LEO in a 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 would then be $8.4 billion [1980 $] and the cost per flight = $22.6M.

That proved a little too ambitious so late 1981 the FSTS was downscaled for more flexibility.

In early 1982, the Langley Research Center was asked by NASA Headquarters to initiate preliminary conceptual studies of a next-generation launch system for 2005 and beyond. Unlike the original one-size-fits-all 1971 Space Shuttle or the earlier Future Space Transportation System, the new system probably would consist of different vehicles -- manned and unmanned, large and small, expendable and reusable.

One such subcomponent was the "Shuttle II" which was envisioned as a fully reusable low-cost piloted vehicle capable of transporting 9,072kg to Space Station Liberty or Destiny in a 4.5 x 9m payload bay or 4,553kg to a 277km sunsynchronous orbit. NASA also wanted a more robust system capable of safely flying quick-sortie missions (<3 days duration) every two weeks with a minimum of maintenance and checkout between flights. The important missions were personnel transport, in-orbit servicing & repair, and return of high-valued commercial products from orbiting space platforms. In other words, missions where a "low dollars per flight" approach was regarded as more important than "low dollars per kilogram"; the latter requirement (low cost transportation of unmanned military & civilian heavy-lift payloads) was to be served by the Advanced Expendable Launch System.

Different "Shuttle II" concepts were investigated but the initially most promising concept appeared to be a VTHL TSTO with parallel staging at Mach 3. This was a very similar concept as the earlier FSTS baseline vehicle, albeit much smaller. CH4, LOX & LH2 propellants would have been used. VTHL SSTO also appeared feasible with modest advances in performance technologies. The Shuttle II's operational life would be 15 years, or 400 flights per vehicle