Challenger
Orbiter OV-099
See also Space Transportation System and space shuttle
This orbiter was destroyed.

Entered service April 4, 1983.
Destroyed January 28, 1986, during its 10th mission.

Flights:
    STS-6    04/04/83
    STS-7    06/18/83
    STS-8    08/30/83
    STS-41B    02/03/84
    STS-41C    04/06/84
    STS-41G    10/05/84
    STS-51B    04/29/85
    STS-51F    07/29/85
    STS-61A    10/30/85
    STS-51L    01/28/86

When Rockwell was granted the contract to build orbiters for the Space Transportation System, two static test articles and two operational orbiters were approved for construction. The second of the two operational shuttle orbiters was Columbia, designated OV-102. The first was Enterprise, OV-101, which had been built for approach and landing tests. The original plan was to convert Enterprise to a fully operational orbiter, thus fulfilling the contract. However, in 1978, a decision was made to not modify OV-101, leaving Columbia the only operational orbiter vehicle. Challenger was built from one of the two static test articles, STA-099. This is the reason for Challenger's unusual designation: OV-099.

Challenger had a special modification in its payload bay which would allow it to carry a Centaur launch vehicle upper stage into orbit. This involved adding extra fuel piping into the bay, since the Centaur upper stage has a liquid-fuel rocket engine, as well as controls in the aft deck to control and monitor the rocket. Discovery has the same modification, but this has since been deemed to risky and there are no plans to use this functionality.

In one of the most tragic accidents in the history of the United States space program, Challenger was lost on January 28, 1986. The vehicle was destroyed, and all seven crew members aboard were lost. More detailed information on the accident can be found in some of the above write-ups. Until the loss of Columbia on February 1, 2003, Challenger was the only United States manned spacecraft to be lost during a mission. (Three astronauts were lost in a fire during a training operation during the Apollo program, but not during an actual mission.)

The rest of the orbiter fleet:
Enterprise * Columbia * Discovery * Atlantis * Endeavour