The next shuttle mission after Challenger was the flight of
Discover, in September 1988. There followed a series of feats in space to rival
those the shuttle fleet accomplished before the Challenger Disaster. One of the
first things Endeavour did was to facilitate the capture of a communication
satellite in the first three person space walk. The Hubble Space Telescope was
deployed and then serviced in subsequent missions. More Spacelab and Spacehab
science missions were executed. Numerous satellites and space probes were
deployed, including the Ulysses probe to study the sun, the Galileo Jupiter
orbiter, and the Magellan Venus probe. The shuttle fleet supported the joint
America/Russian missions to the Russian space station Mir. Shuttles helped to
begin construction of the International Space Station.
The Search for New Solutions
Even so, with the realization that the space shuttle fleet
would not be the answer to the problem of cheap access to space, other
solutions were being sought. Both the Advance Launch System (ALS) and the
National Launch System (NLS) were projects attempting to find a way to replace
expendable rockets with 1950s technology. Both were cancelled when the development costs
ballooned and when the prospect of deploying space based weapons under the SDI
program faded with the end of the Cold War.
The Evolved Expendable Launch Vehicle (EELV) program,
started in the early 1990s, was more successful in that it actually led to the
development of actual launch vehicles. These were the Boeing Delta IV and the
Lockheed Martin Atlas V. These two families of launch vehicles are designed to
address both military and commercial markets.
The search for a new way to launch people into space
continued apace. Even before the Challenger Disaster, NASA and the Department
of Defense began a joint project to build the National Aerospace Plane (NASP).
This project would have developed a family of hypersonic vehicles that would
provide high speed global air transportation, a long range air defense
interceptor, and a low cost, single stage to orbit space craft. Once again the
old story of cost overruns eventually doomed the project. Nevertheless, NASA
continued to research hypersonic flight technologies.
The DC-X was a subscale prototype vehicle developed under
the Strategic Defense Initiative for a proposed single stage to orbit vehicle
to be called the Delta Clipper. The DC-X was a rocket that both launched and
landed vertically. The DC-X flew in a
series of successful flight tests in August and September of 1993, with a
second series from June 1994-July 1995. An enhance version of the DC-X, known
as the DC-XA, was flight tested under the auspices of NASA from May 1996 to
July 1996, when the vehicle was destroyed when it tipped over upon landing.
The X-33 was a program started during the Clinton
Administration to develop a single stage to orbit vehicle to replace the space
shuttle. Though Boeing proposed a prototype based on the vertical take off and
landing concept pioneered by the DC-X/DC-XA program, NASA instead choose a
vertical takeoff, horizontal landing prototype proposed by Lockheed Martin.
This prototype, had it been successful, would have led to a full scale single
stage to orbit vehicle known as Venture Star. However, the attempt to develop
too much leading edge technology too soon led to cost overruns, schedule
slippages, and eventual cancellation.
A kind of companion program to the X-33, the X-34, was
designed to develop a low cost, air-launched vehicle, much like the successful
Pegasus launcher. X-34 suffered much the same fate as the X-33.