Twelfth Columbia flight. The first mission since Skylab to do intensive investigations into the effects of weightlessness on humans. Data learned from this flight will be used in NASA's planning for longer Shuttle missions set for 1992, and in the planning of Space Station Freedom. Landed at Edwards Air Force Base, CA. on June 14, 1991. Mission Duration: 218 hours 15 minutes 14 seconds.

Launch Date: June 5, 1991 Launch Vehicle: Columbia Crew: Commander: Bryan O. O'Connor, Pilot: Sidney M. Gutierrez, Mission Specialists: James P. Bagian, Tamara E. Jernigan, M. Rhea Seddon, Payload Specialists: Drew F. Gaffney, Millie Hughes-Fulford.