U.S. Shuttle Fleet/U.S. Shuttle Fleet.iso/data/cex002.doc

Text File | 1995-04-04 | 3KB | 37 lines

One of the major problems with building the reusable Space Transportation System was
developing a heat-shield material that could survive the stress of reentry not once, but
many times.  The ablative materials developed on the old X-15 rocket plane and used on
the Mercury, Gemini, and Apollo spacecraft would not be satisfactory.  Ablative
substances allowed the reentry vehicle to survive, but left it with sufficient heat damage to
render it unflyable.

After many delays due to budget cutbacks and arguments over the very existence of the
space shuttle itself, a special type of ceramic tile was developed for the underside of the
shuttle.  Despite problems with keeping the tiles from falling off, this solution has worked
remarkably well, and produced a fully reusable shuttle orbiter.

On April 12, 1981, Commander John Young and Pilot Robert Crippen boarded the space
shuttle Columbia on launch pad 39B at the Kennedy Space Center.  Although the shuttle
orbiter had been flown in atmospheric gliding and landing tests, the vehicle had never been
launched into space before.  Before the launch sequence was initiated, no one knew for
sure if the system would actually work.

The shuttle orbiter is attached to a large conical external fuel tank, which supplies fuel to
the shuttle's main engines during launch.  The fuel tank is then discarded when the shuttle
reaches orbit.  On either side of the external fuel tank are solid rocket boosters, which had
never been used before in human space flight.  There were many new components that had
never flown before, and the system was very complicated.  The future of NASA, and
America's position as a leading space power were all riding on Columbia.

When this first shuttle slowly rose off the launch pad and accelerated into space, a new era
had begun in space exploration.  Clearly, reusable vehicles were going to have a dominant
role in the future of space flight.  Although the space shuttle has not realized the economic
benefits of reusable space craft, it has demonstrated that such systems do work and can be
improved upon.

Columbia has now flown more than 15 missions, including four Spacelab science missions.
In 1990, Columbia deployed the Ultraviolet Astronomy Telescope (ASTRO).  As
America's first operational space shuttle, Columbia has been retrofitted and upgraded
several times in its lifetime, and continues to be an active member of America's shuttle
fleet.