| The NASA Space Shuttle program,
officially called the Space Transportation System (STS), has been the United
States’ official means of launching man into outer space for the purpose of
exploration since its inception in the late 1960’s by President Richard Nixon.
The final design of the space shuttle, which is still used today, was
designed to carry between five and seven astronauts, and was to be used for
approximately 100 launches, or 10 years by the program. The first completed,
fully functional NASA space shuttle was the Columbia, which made her debut at
the Kennedy Space Center in Florida on March 25, 1979. Columbia was launched for
the first time on April 12, 1981. Other space shuttles to follow included
Challenger in 1982, Discovery in 1983, Atlantis in 1985 and Endeavour in 1991.
Challenger was lost when it exploded during ascent on January 28, 1986,
killing all seven astronauts aboard. Seventeen years later on February 1, 2003,
the Columbia space shuttle was
destroyed when it disintegrated during reentry, again killing all seven crew
members on board. Space shuttles still in active use by NASA today include
Atlantis, Discovery and Endeavour. Enterprise, Pathfinder, and Explorer are all
full-scale replicas of other active space shuttles, but were built for display
and test flights only, and have never actually entered orbit.
NASA's Space Shuttle at launch, consists of a now rust-colored, but formerly white colored, external tank (ET),
two white, slender solid rocket boosters (SRBs), and a winged orbiter (the space
shuttle in the narrow sense). The orbiter carries astronauts and payload such as
satellites or space station parts into low earth orbit. Normally, five to seven
astronauts ride in the orbiter, with two pilots. Eight have been carried, and
eleven could be accommodated in an emergency landing. The payload capacity is
50,000 lb (22,700 kg). When the orbiter's mission is complete, it fires its
orbital maneuvering thrusters to drop out of orbit and re-enters the Earth's
atmosphere. During the descent and landing, the shuttle orbiter acts as a glider
and makes a completely unpowered ("dead stick") landing. Five spaceworthy
orbiters were built, of which three remain.
The Shuttle is the first orbital spacecraft designed for partial reusability. It
carries payloads to low Earth orbit, provides crew rotation for the
International Space Station (ISS), and performs servicing missions. The orbiter
can also recover satellites and other payloads from orbit and return them to
Earth, but this capacity has not been used often. However, it has been used to
return large payloads from the ISS to Earth, as the Russian Soyuz spacecraft has
limited capacity for return payloads. Each Shuttle was designed for a projected
lifespan of 100 launches or 10 years' operational life. The man responsible for
the design of the STS was Maxime Faget, who had also overseen the Mercury,
Gemini and Apollo spacecraft designs. The crucial factor in the size and shape
of the Shuttle Orbiter was the requirement that it be able to accommodate the
largest planned spy satellites, and have the cross-range recovery range to meet
classified USAF missions requirement for a one-around abort for a polar launch.
Factors involved in opting for 'reusable' solid rockets and an expendable fuel
tank included the desire of the Pentagon to obtain a high-capacity payload
vehicle for satellite deployment, and the desire of the Nixon administration to
reduce the costs of space exploration by developing a spacecraft with reusable
components.
Six shuttles have been built, five of which were spaceworthy. The first orbiter,
Enterprise, was not built for actual space flight, and was used only for testing
purposes. Enterprise was followed by four operational space shuttles: Columbia,
Challenger, Discovery and Atlantis. Challenger was destroyed on launch in 1986,
and Endeavour was built as a replacement. Columbia was destroyed on re-entry in
2003.
NASA announced in 2004 that the Space Shuttle will be retired in 2010 and
replaced by the Orion, a new vehicle that is designed to take humans to the Moon
and beyond.
|
