English: This illustration shows general characteristics of the Skylab with callouts of its major components. In an early effort to extend the use of Apollo for further applications, NASA established the Apollo Applications Program (AAP) in August of 1965. The AAP was to include long-duration Earth orbital missions during which astronauts would carry out scientific, technological, and engineering experiments in space by utilizing modified Saturn launch vehicles and the Apollo spacecraft. Established in 1970, the Skylab Program was the forerunner of the AAP. The goals of the Skylab were to enrich our scientific knowledge of the Earth, the Sun, the stars, and cosmic space; to study the effects of weightlessness on living organisms, including man; to study the effects of the processing and manufacturing of materials utilizing the absence of gravity; and to conduct Earth resource observations. The Skylab also conducted 19 selected experiments submitted by high school students. Skylab's 3 different 3-man crews spent up to 84 days in Earth orbit. The Marshall Space Flight Center (MSFC) had responsibility for developing and integrating most of the major components of the Skylab: the Orbital Workshop (OWS), Airlock Module (AM), Multiple Docking Adapter (MDA), Apollo Telescope Mount (ATM), Payload Shroud (PS), and most of the experiments. MSFC was also responsible for providing the Saturn IB launch vehicles for three Apollo spacecraft and crews and a Saturn V launch vehicle for the Skylab.