STS-55 (Space Transportation System 55), or D-2 was the 55th overall flight of the US Space Shuttle and the 14th flight of Shuttle Columbia. This flight was a multinational Spacelab flight involving 88 experiments from eleven different nations. The experiments ranged from biology sciences to simple earth observations.
Columbia carried to orbit the second reusable German Spacelab on the STS-55 mission and demonstrated the shuttle's ability for international cooperation, exploration, and scientific research in space. The Spacelab Module and an exterior experiment support structure contained in Columbia’s payload bay comprised the Spacelab D-2 payload. (The first German Spacelab flight, D-1, flew Shuttle mission 61-A in October 1985.) The U.S. and Germany gained valuable experience for future space station operations.
The D-2 mission, as it was commonly called, augmented the German microgravity research program started by the D-1 mission. The German Aerospace Research Establishment (DLR) had been tasked by the German Space Agency (DARA) to conduct the second mission. DLR, NASA, the European Space Agency (ESA), and agencies in France and Japan contributed to D-2's scientific program. Eleven nations participated in the experiments. Of the 88 experiments conducted on the D-2 mission, four were sponsored by NASA.
