NASA's Shuttle Program, formerly known as the Space Transportation System (STS), uses partially reusable rocket-launched vehicles to go into earth orbit, transport people and cargo between earth and orbiting spacecraft, and then glide to a runway landing on earth. The first flight of a space shuttle into orbit took place in 1981. The shuttle consists of a winged orbiter that carries crew and cargo; an expendable external tank of liquid fuel and oxidizer for the orbiter's three main rocket engines; and two large, reusable solid-propellant booster rockets. The orbiter lifts off vertically like an expendable launch vehicle but makes an un-powered descent similar to a glider. Each orbiter was designed to be reused up to 100 times. The Shuttle Challenger was one of the first four U.S. space shuttles. It made its first flight in 1983. At the launch for its tenth mission on January 20, 1986, faulty O-rings in the seams of its solid rocket booster failed and the booster exploded, destroying the Challenger and killing its seven-member crew. This tragic event was even more tragic in the fact that the families of the astronauts were present at the Florida launch site and witnessed the Challenger blow up some 90-miles above the earth's surface. Adding further to the tragedy was the fact that Sharon Christa MacAuliffe, a public school teacher, was one of the seven aboard who died. Shuttle Challenger was replaced in 1992 by Shuttle Endeavour. Our Challenger commemorative bill honors the brave astronauts and teacher aboard the Challenger.