So there were four small spaceplanes, conceived by four separate nations, each to be launched by a ballistic missile, and not one of them ever flew. In every case, funding was either cut off or never appeared at all. Every one of these spaceplanes was to have perched atop a rocket, ridden into space, and glided back for reuse. Reusability is supposed to be a good thing. Since these were reusable spacecraft, what went wrong?
Dyna-Soar was canceled, in part because NASA's rapidly developing Gemini program was planning to put a two-man crew into space atop a Titan II rocket. This missile, borrowed from the US Air Force, did not require strap-on solid rocket boosters. The Titan III rocket did. And this was the vehicle intended for both Dyna-Soar and the Air Force's Manned Orbiting Laboratory. Dyna-Soar was canceled in favor of Manned Orbiting Laboratory, but it, too, eventually met the dreaded budget axe.
European engineers were concerned about weight as well. The 21-metric-ton Hermes was all the Ariane 5 launch vehicle could handle, and much of that weight was in the form of wings, wheels, ejection seats, and the throwaway Resource Module. Downgrading Hermes from six to three crewmembers at the same time as its payload shrank from 10,000 lb to around 6,500 lb made the money handlers think twice.
In Japan, the original HOPE concept weighed 10 tons, yet was able to deliver only 1 ton to a space station. And 10 tons was right at the limit of the H-II booster
then being developed. The much heavier 22-ton manned spaceplane would have needed a much more powerful booster, such as the proposed H-IID.
Finally, the cash-strapped Russian government was not about to sink money into a tiny spaceplane when it was very familiar with the greater payload capacity of Soyuz and the unmanned Progress supply vessels.
There is a recognizable pattern here, and that pattern has to do with two things: payload capacity and partial reusability. By perching a winged spacecraft on top of a ballistic missile (Fig. 6.5), the wings, the landing gear, the tail, and all the other quintessentially airplane-like characteristics of the spaceplane become dead weight during launch. This dead weight directly subtracts from the payload that the launch vehicle otherwise would be able to place into orbit. As a result, Gemini-Titan outperformed Dyna-Soar, just as Soyuz outdoes Kliper. In addition, the sizes and masses of the reusable components are very small when compared with the sizes and masses of the throwaway components - the huge booster rockets. Therefore, reusability becomes a nonissue. Funding concerns, and other factors such as pay-load capacity, completely override it.
Winged spaceplanes can be launched ballistically, as we know (Space Shuttle and Buran), but only by using draconian measures. A huge, external supply of propellants, in either liquid or solid form, has to be attached to the reusable spaceplane. Furthermore, these large spaceplanes have relatively large payload capacities, on the order of 30 tons, but again only by using drastically large boosters. For all of these reasons, it seems, the small ballistic spaceplane has never managed to get much past the planning stage. But as we shall see, there are other ways of getting into space, including riding piggyback.
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