Medical tests in space. Astronaut Guion Bluford tries out the treadmill on Shuttle Challenger during Mission STS-8. The treadmill was used to allow astronauts to exercise during medical tests in orbit. Bluford was the first black astronaut, and has flown as mission specialist on three Shuttle missions to date (STS-8, 61A and STS-39). Bluford is a colonel in the US Air Force, and has a doctorate in aerospace engineering. Mission STS- 8 was the first Shuttle night launch and night landing, and flew between 30 August and 5 September 1983.