STS-54Space Shuttle Endeavour lifts off on the 53rd shuttle flight, a six-day mission to launch the fifth TDRS (Tracking & Data Relay Satellite) and perform assorted experiments. A five-hour spacewalk is conducted in the cargo bay to practice spacewalking techniques for future missions. Aboard Endeavour for her third flight are Commander John Casper, Pilot Donald McMonagle, and mission specialists Mario Runco, Gregory Harbaugh and Susan Helms.