Suborbital spaceplanes are already being built, with the financial backing of Richard Branson and his Virgin Galactic Spacelines. The technical expertise is being supplied by Scaled Composites of Mojave, California, who has the experience in designing and building SpaceShipOne. Other companies are also working on the suborbital spaceplane concept, notably Bristol Spaceplanes and XCOR Aerospace. Although the Bristol Spaceplanes Ascender is planned to be the second stage in a two-stage-to-orbit design, the Ascender itself could easily serve as a suborbital spaceplane, offering tourist rides into deep space. XCOR Aerospace's Xerus spaceplane is designed to take off under its own power from a runway and fly into suborbit. The company has identified three markets: (1) space tourists, (2) microgravity experiments, and (3) small payloads to be boosted into orbit from the edge of the atmosphere. XCOR's methane-fueled rocket engines have already achieved a good operating and safety record. Of these three potential markets, it is clearly the prospect of space tourism that will provide the most paying customers. Small markets undoubtedly exist, as well, for upper atmospheric or microgravity experiments and small payloads requiring a boost into orbit. But in terms of sheer numbers, these will pale in comparison to the legions of adventurous souls who will gladly pay a small fortune for the experience of their lives. These trailblazing space tourists will understand perfectly well that mature spaceplanes will take time - and money - to develop. This development process will begin with the suborbital space lob: a few moments of exhilarating acceleration, a few minutes of weightlessness, and a peek at our planet from the inky realm of space.
Spaceplanes are here to stay, but they have a long way to go before they mature into what could be called advanced spaceplanes (Fig. 5.10 and Chap. 9). They need to harness energies about 30 times greater than what either the X-15 or SpaceShipOne was capable of. Can it be done? It took 44 years for airplanes to advance from the 30-mph Wright Flyer to the 700-mph X-1. This represents a 30-fold increase in speed and energy, analogous to what is required of spaceplanes. There is much work to do, and plenty of challenges to keep engineers busy well into the future.
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