Space Shuttle

The space shuttles have performed a wide variety of tasks in over two decades of operation. Some examples of the kinds of activities carried out during shuttle flights include the following:

• After the launch of the Challenger on February 3, 1984 (mission STS-41B), astronauts Bruce McCandless II and Robert L. Stewart conducted untethered space walks to test the Manned Maneuvering Unit backpacks, which allowed them to propel themselves through space near the shuttle. The shuttle also released into orbit two communication satellites, the Indonesian Palapa and the American Westar. Both satellites failed soon after release but were recovered and returned to Earth by the Discovery in 1984 (STS-51A).
• During the Challenger flight that began on April 29, 1985 (STS-51B), crew members carried out a number of experiments in Spacelab 3 to determine the effects of microgravity on living organisms and on the processing of materials. They grew crystals of mercury (II) oxide over a period of several days, observed the behavior of two monkeys and 24 rats in a microgravity environment, and studied the behavior of liquid droplets held in suspension by sound waves.
• The Discovery mission launched August 27, 1985 (STS-51I) deposited three communications satellites in orbit. On the same flight, astronauts William F. Fisher and James D. Van Hoften left the shuttle to make repairs on a Syncom satellite that had been placed in orbit during flight STS-51D but had malfunctioned.
• One of the most important shuttle missions ever was the repair of the Hubble Space Telescope by the crew of the Endeavor in December, 1993 (STS-61). The Hubble had been deployed, by a shuttle mission several years earlier, with a defective mirror; fortunately, it had been designed to be repaired by spacewalking astronauts. The crew of the Endeavor latched on to the Hubble with the shuttle's robotic arm, installed a corrective optics package that restored the Hubble to full functionality. The Hubble has since produced a unique wealth of astronomical knowledge.