Aˈpollo ˌProgram the US government space programme to send people to the Moon, which succeeded in 1969 when the Apollo 11 spacecraft landed on the Moon. Apollo 13 was a later unsuccessful attempt to land on the Moon again, and the words one of the astronauts used when he thought something was going wrong, ‘Houston, we have a problem’, are sometimes now used in a humorous way. → Armstrong, Neil, Gemini Program, the, Houston, Mercury program, the