Many people believe that NASA's extensive use of computers has kept the agency at the forefront of computer development. This study evaluates the hypothesis in regard to computers used on board manned spacecraft. The results show that NASA's contributions to computer science were made primarily in the areas of software verification and fault tolerance, and that overall, NASA has adopted proved technology for manned space flight operations. This technology is consistently behind the state of the art in terms of hardware, but the continued use of older technology in manned spacecraft is not necessarily a negative development. The computer power used in the Apollo, Gemini, and shuttle programs has been sufficient for the requirements of the missions. Most important, reliability has been ensured.