Nevertheless, the economics of preparing a single stage, rather than two stages, have kept space engineers interested in SSTO designs. Future RLVs also are expected to employ more advanced, reliable systems, making them safer than expendable launch vehicles, and thus allow launches from inland sites (i.e., no stages to splash down into the ocean), perhaps even airports, where weather is less of a concern than at coastal spaceports.
Early Concepts
Because it was easier to adapt existing military missiles, which are designed for a single flight, most launchers have been expendable. Nevertheless, space visionaries have often focused on RLVs. One of the most significant early concepts was a three-stage vehicle designed by German-born American engineer Wernher von Braun in 1952 and popularized in his book Across the Space Frontier. The first two stages would parachute into the ocean forrecovery while the winged third stage, carrying crew and cargo, landed like an airplane. The 1951 movie When Worlds Collide depicted a rocket-powered sled that gives a vehicle its initial boost.
Several RLV concepts were advanced in the 1960s. Notable among these was a reusable design by a man named Philip Bono, then with Douglas Aircraft Company. His design comprised a core vehicle holding a payload bay, liquid oxygen tank, and a ring of small rocket engines around the base.
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