The Space Shuttle
The Space Shuttle is a reusable vehicle that can enter earth orbit and then return to earth to land like a conventional airplane. A vehicle of this nature would make possible the manned delivery of satellites into orbit and their subsequent repair or retrieval. The vehicle also could serve for several days as a manned orbital laboratory. Tests of a U. S. space shuttle are scheduled to begin in the late 1970's.
Because of budget problems, the proposed U.S. space shuttle is a compromise with previous plans for a system in which both the booster and the orbiter vehicle would be manned. The unmanned, recoverable-booster stage would consist of two large, solid-propellant rockets mounted in parallel. Their combined thrust of more than 5 million pounds (2.25 million kg) would allow the shuttle to carry as much as 65,000 pounds (29,250 kg) of payload on each flight. The orbiter vehicle would be essentially a hybrid spacecraft and airplane, resembling a delta-wing plane about the size of a DC-9 and weighing approximately 70 tons (63 metric tons).
The shuttle would be launched by the combined energy of the booster stage and the or-biter's three liquid-propellant engines, which would have a total thrust of 1.4 million pounds (0.63 million kg). At an altitude of about 25 miles (40 km) the booster stage would separate and descend by parachute to the ocean for later recovery. Meanwhile the orbiter, manned by two pilots and two flight engineers, would enter space under its own power and later return to earth to make a conventional landing at an airfield.
Proponents of the space shuttle program hold that the vehicle will replace practically all of the one-shot-only launch vehicles currently in use, offering substantial reductions in the cost of delivering a payload into orbit, and simplifying payload design. Almost any kind of scientific or applications satellite can be orbited in this manner. Critics of the program hold that the true value of the program depends on what they feel would be an undesirable resurgence in manned space efforts, and that the projected cost is un-realistically low, but proponents maintain that unmanned payloads are the only shuttle purpose and that the cost is accurate.