The Apollo Applications Program (AAP) was established by NASA headquarters in 1968 to develop science based manned space missions using surplus material from the Apollo Lunar Landing Program. Initially the AAP office in Washington was an off shoot of the Apollo "X" bureau also known as the "Apollo Extension Series" that was developing technology concepts for mission proposals based on the Saturn IB and Saturn V boosters such as a Space Station, the Grand Tour and "Voyager program" of Mars Lander probes and a manned lunar base. The Apollo lunar base proposal saw an unmanned Saturn V used to land a shelter based on the Apollo Command/Service Module (CSM) on the moon. A second Saturn V would carry a three man crew and a modified CSM and Apollo Lunar Module (LM) to the moon. The two man excursion team would have a surface stay time of nearly 200 days and use of an advanced lunar rover and a lunar flyer as well as logistics to construct a larger shelter. The isolation of the CSM pilot was a concern for mission planners so proposals that it would be a three man landing team or that the CSM would rendezvous with an orbiting module were considered.
When procurement of Saturn Vs other than those required for the Lunar landing was stopped in 1968 focus shifted to AAP. Aside from attempting to show that Apollo presented value for money NASA and the main contractors of Boeing, Grumann, North American and Rockwell also hoped to put-off the inevitable scaling down of staff and facilities following the completion of the first moon landing.
Three AAP proposals were selected for development:
The Apollo Telescope Mission would be an earth orbiting mission for Solar Observation. The Telescope would be based on a modified Lunar Module ascent stage and launched using a S-IVB. The Telescope would be docked to a CSM with a three man crew. Solar panels on the Telescope would provide additional power allowing an extended mission of 21-28 days. The Telescope module would include a pressurized compartment providing additional living and workspace for the crew.
The Apollo Manned Survey Mission proposed an Earth observation science module also based on the Lunar Module ascent stage and would also have been launched using a S-IVB vehicle into a high inclination orbit. It was also proposed that a surplus Saturn V would launch a manned lunar survey mission to establish suitable sites for later manned landings.
The Wet Workshop concept provided for a low-budget earth orbiting space station. A modified S-IVB would be launched into orbit the second stage carrying a docking module and large solar panels. An Apollo CSM would then be able to dock with the Second stage and enter the now empty fuel tanks which would provide a workshop in space. The interior space could be pressurized and it was also suggested that the Apollo Telescope and Survey Mission modules might be docked to the Wet Workshop to create a modular space station.
Originally AAP missions would alternate with Apollo Lunar missions starting in 1969. However when NASA's 1969 budget was cut focus was shifted to the Skylab dry workshop space station proposal which managed to accommodate the equipment already specified for the AAP missions.