Leroy Gordon Cooper, Jr., also known as Gordo Cooper, (March 6, 1927 – October 4, 2004) was an engineer and American astronaut. Cooper was one of the seven original astronauts in Project Mercury, the first manned space effort by the United States. He flew the longest spaceflight of the Mercury project, was the first American to sleep in orbit, and was the last American to launch alone into Earth orbit and conduct an entire solo orbital mission.