Engineering and operational characteristics of the extended duration orbiter
A program is being pursued to lengthen the mission duration of the Space Shuttle from 10 days to 16 days, with future plans to increase the on-orbit stay time to 28 days. Presently, the length of the mission is limited by fuel cell reactants, stowage constraints, and life-support system consumables. In December 1988, NASA gained approval to begin the design and development of the extensive modifications to OV-102 Columbia required to extend its mission duration to 16 days. Additionally, OV-105 Endeavour is now being manufactured so as not to preclude its transformation to a 28-day vehicle in the future, should that program gain subsequent approval and funding. The first extended duration orbiter (EDO) launch of Columbia is slated for March 1992 with the US microgravity laboratory (USML) as its payload. Scientific payloads such as the USML and Spacelab, which require longer periods of zero gravity or the vacuum of space, will greatly benefit from the EDO program.