NASA's Space Shuttle was conceived as a reusable spacecraft that would reduce the cost of space access. The first orbital flight, STS-1, launched on April 12, 1981, with John Young and Robert Crippen aboard Columbia. The Shuttle had a delta-wing orbiter, solid rocket boosters, and an external fuel tank. It could carry 65,000 pounds to low Earth orbit and land on a conventional runway. But the program was marred by two catastrophic losses. On January 28, 1986, Challenger broke apart 73 seconds after launch when an O-ring seal failed in the right solid rocket booster. All seven crew members died, including schoolteacher Christa McAuliffe. On February 1, 2003, Columbia disintegrated during reentry when a piece of foam insulation from the external tank struck the leading edge of the left wing, breaching the thermal protection system. All seven crew members died. The program completed 135 missions before retiring in 2011. The Shuttle proved that winged spacecraft could operate, but it never achieved the cost savings promised.