The space shuttle is the world's first reusable spacecraft, and the first spacecraft in history that can carry large satellites both to and from orbit. The shuttle launches like a rocket, maneuvers in Earth orbit like a spacecraft and lands like an airplane. Each of the three space shuttle orbiters now in operation -- Discovery, Atlantis and Endeavour -- is designed to fly at least 100 missions. So far, altogether they have flown a combined total of slightly more than one-fourth of that.

Columbia was the first space shuttle orbiter to be delivered to NASA's Kennedy Space Center, Fla., in March 1979. Columbia and the STS-107 crew were lost Feb. 1, 2003, during re-entry. The orbiter Challenger was delivered to KSC in July 1982 and was destroyed in an explosion during ascent in January 1986. Discovery was delivered in November 1983.

Atlantis was delivered in April 1985. Endeavour was built as a replacement following the Challenger accident and was delivered to Florida in May 1991. An early space shuttle orbiter, the Enterprise, never flew in space but was used for approach and landing tests at the Dryden Flight Research Center and several launch pad studies in the late 1970s.

The space shuttle consists of three major components: the orbiter which houses the crew; a large external fuel tank that holds fuel for the main engines; and two solid rocket boosters which provide most of the shuttle's lift during the first two minutes of flight. All of the components are reused except for the external fuel tank, which burns up in the atmosphere after each launch.

The longest the shuttle has stayed in orbit on any single mission is 17.5 days on mission STS-80 in November 1996. Normally, missions may be planned for anywhere from five to 16 days in duration. The smallest crew ever to fly on the shuttle numbered two people on the first few missions.
The largest crew numbered eight people. Normally, crews may range in size from five to seven people. The shuttle is designed to reach orbits
ranging from about 185 kilometers to 643 kilometers (115 statute miles to 400 statute miles) high.

The shuttle has the most reliable launch record of any rocket now in operation. Since 1981, it has boosted more than 1.36 million kilograms (3 million pounds) of cargo into orbit. More than than 600 crew members have flown on its missions. Although it has been in operation for more than 20 years, the shuttle has continually evolved and is significantly different today than when it first was launched. NASA has made literally thousands of major and minor modifications to the original design that have made it safer, more reliable and more capable today than ever before.

Since 1992 alone, NASA has made engine and system improvements that are estimated to have tripled the safety of flying the space shuttle, and the number of problems experienced while a space shuttle is in flight has decreased by 70 percent. During the same period, the cost of operating the shuttle has decreased by one and a quarter billion dollars annually — a reduction of more than 40 percent. At the same time,
because of weight reductions and other improvements, the cargo the shuttle can carry has increased by 7.3 metric tons (8 tons.)

NASA is prepared to continue flying the shuttle for at least the next decade and plans to continue to improve the shuttle during the next five years, with goals of increasing its safety by improving the highest-risk components. NASA will also be working to correct the problems identified by the Columbia Accident Investigation Board during the investigation of the STS-107 accident.

In managing and operating the space shuttle, NASA holds the safety of the crew as its highest priority.