STS-51-B

The mission insignia features the Challenger with her payload doors open, to show the onboard SpaceLab. The orbiter rides over the American flag. The seven crewmembers are represented by the 7 stars on the patch, that indirectly refer to the Mercury Seven as a nod to their legacy. Behind the orbiter, the contours of Pegasus can be seen, as a reference to the ESA. The white board surrounding it all has the appearance of a space suit helmet, with the names of the two respective teams grouped around them on a round band encircling the insignia , and the two mission specialists on an added section below. To further create some sort of contrast, the team colors are reprised for each member's name.

Overmyer using a treadmill on Challenger's middeck.

Challenger lifted off from Kennedy Space Center (KSC)'s launch pad 39A at 12:02 pm EDT on April 29, 1985. The crew members included Robert F. Overmyer, commander; Frederick D. Gregory, pilot; Don L. Lind, Norman E. Thagard and William E. Thornton, mission specialists; and Lodewijk van den Berg, of EG&G Energy Management, Inc., and Taylor G. Wang, of the Jet Propulsion Laboratory, both payload specialists.[3] Average age of 48.6 was the oldest for an American space mission.[4] Similar to the previous Spacelab mission, the crew was divided roughly in half to cover 12-hour shifts, with Overmyer, Lind, Thornton and Wang forming the Gold team, and Gregory, Thagard and van den Berg as the Silver team.

STS-51-B was the second flight of the European Space Agency's Spacelab pressurized module, and the first with the Spacelab module in a fully operational configuration. Spacelab's capabilities for multi-disciplinary research in microgravity were successfully demonstrated. The gravity gradient attitude of the orbiter proved quite stable, allowing the delicate experiments in materials processing and fluid mechanics to proceed normally. The crew operated around the clock in two 12-hour shifts. Two squirrel monkeys and 24 rats were flown in special cages,[5] the second time American astronauts flew live non-human mammals aboard the shuttle. The crew members in orbit were supported 24 hours a day by a temporary Payload Operations Control Center, located at the Johnson Space Center.

On the mission, Spacelab carried 15 primary experiments, of which 14 were successfully performed. Two Getaway Special experiments required that they be deployed from their canisters, a first for the program. These were NUSAT (Northern Utah Satellite) and GLOMR (Global Low Orbiting Message Relay Satellite). NUSAT deployed successfully, but GLOMR did not deploy, and was returned to Earth.

Challenger landed safely at Edwards Air Force Base at 12:11 pm EDT on May 6, 1985, after a mission lasting 7 days, 8 minutes and 46 seconds.

While participating in the investigation into the destruction of Challenger during STS-51-L in 1986, Overmyer discovered that a problem with the shuttle's O-rings, similar to that which led to the disaster, had emerged during the launch of STS-51-B. Morton Thiokol engineers told Lind after the mission that "you came within three-tenths of one second of dying."[6] It was the problem with the O-rings on the left solid rocket motor on this launch (SRM 16A) that prompted Roger Boisjoly to write his famous memo to Bob Lund about the potential for the O-rings to cause catastrophic failure. (See "Report of the Presidential Commission on the Space Shuttle Challenger Accident". Report of the Presidential Commission on the Space Shuttle Challenger Accident, Volume 5.)

• List of human spaceflights
• List of Space Shuttle missions

 This article incorporates public domain material from websites or documents of the National Aeronautics and Space Administration.

• NASA mission summary
• STS-51B Video Highlights