Manned Orbiting Laboratory

The Manned Orbiting Laboratory (MOL), originally referred to as the Manned Orbital Laboratory, was part of the United States Air Force's manned spaceflight program, a successor to the cancelled Boeing X-20 Dyna-Soar military reconnaissance space plane project. The project was developed from several early Air Force and NASA concepts of manned space stations to be used for reconnaissance purposes. MOL evolved into a single-use laboratory, with which crews would be launched on 40-day missions and return to Earth using a Gemini B spacecraft, derived from NASA's Gemini program.

The MOL program was announced to the public on December 10, 1963, as a manned platform to prove the utility of man in space for military missions. Astronauts selected for the program were later told of the reconnaissance mission for the program. The contractor for the MOL was the Douglas Aircraft Company. The Gemini B was externally similar to NASA's Gemini spacecraft, although it underwent several modifications, including the addition of a circular hatch through the heat shield, which allowed passage between the spacecraft and the laboratory.

MOL was cancelled in 1969, during the height of the Apollo program, when it was shown that unmanned reconnaissance satellites could achieve the same objectives much more cost-effectively. U.S. space station development was instead pursued with the civilian NASA Skylab (Apollo Applications Program) which flew in the mid-1970s.

In the 1970s, the Soviet Union launched several Almaz military space stations, very similar to the MOL in intent, but cancelled the military program in 1977.