Skylab was the first U.S. space station and the only one operated exclusively by the U.S.
It was launched un-crewed by NASA on May 14, 1973 from Launch Complex 39A of the Kennedy Space Center.
The station was launched on a two-stage version of the Saturn V rocket which placed it into the required orbit.
The station module experienced serious damage during its deployment in orbit, requiring innovative repairs by the station crews to initiate and maintain Skylab's operation.
Skylab remained in orbit for over six years, with 24 weeks of occupation, by three station crews called Skylab 2, 3, and 4. The launch of the station was designated Skylab 1. Each crew consisted of three astronauts transported in the Apollo command and service modules (CSMs) launched by Saturn IB rockets.
Operations by the crews included repairs to Skylab, solar and Earth observation and hundreds of experiments.
Skylab was left in a parking orbit after the last mission to the station, Skylab 4. NASA had planned to re-boost the station using the new Space Shuttle, but the shuttle was not ready in time. The stations orbit decayed sooner than expected leading to its disintegrated in the atmosphere on July 11, 1979 scattering debris across the Indian Ocean and Western Australia.
Skylab References: Wikipedia | NASA | Historic Spacecraft | Encyclopedia Astronautica
In the early 1960's NASA studied various space station designs which generally looked at platforms launched by the Saturn V. These would be used by crews carried on Apollo command and service module launched by Saturn IB rockets. Alternatively crews would use Gemini capsules launched by Titan II-C rockets. This option would be much less expensive as long as cargo was not needed.
NASA was concerned about losing Apollo program workers after the moon landing in 1969. The Apollo Logistic Support System Office was therefore created to study various ways to modify the Apollo hardware for scientific missions. The office initially proposed a number of projects including an extended-stay lunar mission, a large crewed solar telescope using a Lunar Module and a variety of small space stations using Lunar Modules or Apollo command and service modules. In August 1965, the office was renamed to the Apollo Applications Program (AAP).
In November 1964 it was proposed to build a large station based on the second stage of a Saturn V rocket. The design replaced the third stage with an aeroshell and an adapter for the Apollo command and service module on top. Inside the shell was a three meter cylindrical equipment section. On reaching orbit, the second stage would be vented to remove any remaining hydrogen fuel, then the equipment section would be slid into it via a large inspection hatch. This became known as a "wet workshop" concept, because of the conversion of an active fuel tank.
The workshop filled the entire interior of the second stage's hydrogen tank, with the equipment section forming a "spine" and living quarters located between it and the walls of the booster. Power was to be provided by solar cells lining the outside of the second stage.
This proposal required a dedicated Saturn V launch and it was not known if any Saturn Vs would be available after the Moon landing. However there were a number of Saturn IBs free for use and a smaller "wet workshop" could be based on them. They could be launched as the second stage of a Saturn IB.
A number of stations based on the Saturn V's third stage, S-IVB, were studied from mid-1965, These had much in common with the Skylab design that eventually flew. An airlock would be attached to the hydrogen tank and a minimum amount of equipment would be installed in the tank itself in order to avoid taking up too much fuel volume. Floors of the station would be made from an open metal framework that allowed the fuel to flow through it. After launch, a follow-up mission launched by a Saturn IB would carry solar panels, an equipment section and docking adapter.
In August 1967 Nasa cancelled the proposed lunar mapping and base construction missions leaving only the Earth-orbiting missions remaining in the Apollo Applications Program (AAP). These included the Orbital Workshop and Apollo Telescope Mount solar observatory. The success of Apollo 8 in December 1968, made it likely that a Saturn V rocket would be available to launch a "dry workshop", with its interior already prepared, directly into orbit.
Several Moon missions were also canceled, which freed up three Saturn V boosters for the AAP program. With the extra power of the Saturn V's available, the wet workshop concept was no longer needed.
The final design of Skylab included an orbital workshop (the main habitable space inside Skylab) based on the Saturn V's third stage, S-IVB, the Apollo Telescope Mount (a multi-spectral solar observatory), a multiple docking adapter with two docking ports, an airlock module with extravehicular activity (EVA) hatches.
Electrical power came from solar arrays, attached to the outside of the workshop module, and fuel cells in the docked Apollo command and service module. The rear of the station included a large waste tank, propellant tanks for maneuvering jets, and a heat radiator.
A dry workshop simplified plans for the interior of the station. Habitability and comfort for the astronauts was provided by a wardroom for meals and relaxation plus a window to view Earth and space. Habitability had not previously been an area of concern when building spacecraft due to their brief mission durations. The Skylab missions, however, would last for months.
Astronauts also requested books, individual music choices and improved food choices. For sleeping in space, each astronaut had a private area the size of a small walk-in closet, with a curtain, sleeping bag, and locker. Designers also added a shower and a toilet for comfort and to obtain precise urine and feces samples for examination on Earth. Skylab did not have recycling systems for urine and did not dispose of waste by dumping it into space. The liquid oxygen tank below the workshop was used to store trash and wastewater.
Astronauts usually stood to eat, as sitting in microgravity strained their abdominal muscles. Although the food was an improvement from the Apollo missions it was reported as bland and repetitive. Weightlessness also caused utensils, food containers, and bits of food to float away and gas in the drinking water contributed to flatulence.
The station had a bicycle and other equipment, and astronauts could jog around the water tank. Recreational equipment included a darts set, playing cards, books and music players. The window with its view of Earth. however, became the most popular way to relax in orbit.
More details on the design and functions of the station are given in the "Components" page.
Skylab was occupied for 171 days during its three crewed expeditions, each of which extended the human record for the amount of time spent in space. The Skylab 2 mission occupied the station for 28 days, Skylab 3 for 56 days and Skylab 4 for 84 days. Astronauts performed ten spacewalks and logged about 2,000 hours of scientific and medical experiments including the astronauts' adaptation to extended periods of microgravity. Solar experiments included photographs of eight solar flares and produced valuable results that would have been impossible to obtain with un-crewed spacecraft.
More details of the missions and experiments are given in the "Operation" page.