We now come to the crux of the matter, which bears on many of the points to follow. Airplanes, with their wings and wheels, are specifically designed for repeated and frequent use. They land with all parts intact, taxi up to the ramp,

Fig. 2.4 The ballistic landing technique has certain disadvantages (courtesy NASA)

and are quickly readied for the next flight. The exchange of passengers and cargo, refueling, and other services such as routine maintenance and wing de-icing are all parts of an intricate but efficient infrastructure. This allows relatively simple, economic operations of many airplanes of all sizes and descriptions at a single airport, all under an umbrella of amazing safety and affordability.

Ever since the early Chinese fired their primitive powder rockets at the attacking Mongol hordes eight centuries ago, rocket men have been in the habit of throwing away their missiles (Fig. 2.4). On the other hand, ever since the Wright brothers made their initial heavier-than-air powered flights one century ago, pilots have been in the habit of reusing their aircraft. To this day, ballistic launch vehicles get rid of the greater bulk of their structure on every launch. This fact alone has kept the costs and hazards of rockets at a high level.

The spacelines of the future would never consider operating throwaway rockets. Given a choice between ballistic vehicles that might land anywhere in case of in-flight failure, or winged vehicles that can at least be glided and guided by a pilot, the choice is obvious (Fig. 2.5). Winged vehicles are automatically reusable, and their operation is well understood. The aviation industry has existed for over 100 years. Every aircraft that has ever flown has been designed not only for reuse, but for daily use. This is not the case with ballistic rockets. As a result, the safety record with aircraft is much better than with rockets, because there has been far more experience in aviation than is the case with spaceflight. For this reason alone, spaceplanes should be developed from existing airplanes by appropriate modifications. A good spaceplane should be able to operate as an efficient airplane first, and then be upgraded for spaceflight. This is far easier said than done, and will require sustained effort. Space tourism will provide the sustainable impetus to make this happen.

Fig. 2.5 The X-2 after landing on a collapsed nose wheel. With wings and pilot, both craft and occupants can fly again (courtesy NASA)

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