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Monday, July 11, 2011

Skylab Falls, July 11, 1979

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Today in 1979, Skylab fell back to Earth after six years in orbit. This space station was the first attempt by the United States to put a long-term platform in space for the purpose of scientific experimentation. It remains the only space station that was completely of American design and construction.

The idea for a US space station dates back to the 1950’s, when the concept of using the discarded upper stage of a large rocket was first put on paper. This idea was far-reaching, so much so that it was not pursued for another decade. In the meantime, the US Air Force made plans to build a smaller station, essentially a manned spy satellite, called the Manned Orbiting Laboratory, or MLO. It would carry two men and several powerful telescopes. When plans for the MLO became known to NASA administrators, the program was immediately seen as a threat to their funding. And so it came to be that, while racing to put a man on the moon before the Soviets, the minds at NASA also began drawing up ideas for a space station.

At first, NASA wanted a station large enough to hold a crew of 24. A design of this magnitude would require orbital construction and an entirely new generation of reusable supply vehicles to transport the tons of food, water and other supplies needed to keep two dozen astronauts alive and productive for months at a time. But with the likelihood of budget cuts looming on the horizon, plans for the giant station were put on hold in lieu of a smaller, more affordable orbital lab. As time went by, however, the giant station and her new resupply craft did not die; eventually, the space station design became Space Station Freedom, a 1980’s proposal that was eventually scaled down to become the International Space Station. The resupply vessel became the Space Shuttle.

By the mid-1960’s, the design had been more or less finalized. The station would be made from one stage of a Saturn rocket, the S-IVB stage. Originally, the stage would actually be filled with hydrogen fuel since the only available lifting rocket, the Saturn 1B, needed to use that stage’s thrust to achieve orbit. Once in a safe orbit, the stage’s fuel tank would be vented to space and everything would be moved in. This planned changed when NASA canceled Apollo missions 18 through 20, freeing up large Saturn V rockets that could achieve Earth orbit without the thrust developed by the S-IVB stage. Thus, the space station could be assembled on the ground and launched into space as a complete package.

Skylab included the Apollo Telescope Mount, the EREP (or Earth Resources Experiment Package), the Multiple Docking Adapter (with two docking ports), the airlock (with EVA hatches for spacewalks), and the Orbital Workshop in the main body of the station, which housed much of the supporting systems. Power came from a solar array as well as fuel cells in the docked Apollo Command Service Module. The rear of the station included a large waste tank, tanks for maneuvering jets, and a heat radiator.

Skylab, as the space station was dubbed, was launched on May 14, 1973. While everything about the launch was within specifications, the station was discovered to be seriously damaged during its trip to Earth orbit. One of the station’s main solar panels had broken off completely and the other one was pinned to the side of the station by the remains of the micrometeoroid shield, another victim of the launch. The first crew to visit the station on May 25, 1973 stayed for 28 days and spent a great portion of that time doing repair work. The second crew came aboard on July 28 of the same year and stayed for 59 days. The final crew arrived on November 16, 1973 and lived aboard Skylab for 84 days. Each crew of Skylab broke the previous record for the most time spent in space by human beings.

During their time aboard Skylab, the crews performed solar experiments that led to the discovery of the Sun’s coronal holes. They also did experiments that led to a greater understanding of the human body’s ability to adapt to low-gravity environments. The astronauts had little free time, but they had been provided with a dart board, playing cards, books, and tape players for their non-working hours. However, looking out the station's window that provided a view of the Earth became the most popular activity for all the crews.

After the third crew left, Skylab was placed in an orbit that was expected to deteriorate in 8 years. The Space Shuttle was supposed to lift the station to a higher orbit in 1979, but the first Shuttle mission did not fly until 1981. An unmanned mission was planned, but funding was denied. Even if Skylab had been saved, it would probably have never been used again. The launch damage was worse than what could be fixed by the first crew and any future crews would have had to replace many critical systems before the station could be used long-term. The decision was taken to let Skylab fall.

The station met the thick part of Earth’s atmosphere on July 11, 1979. Debris fell over a wide area of the Indian Ocean and Western Australia. No one was injured by falling parts, but the Shire of Esperance in Australia fined the United States $400 for littering, a debt which remained unpaid until April, 2009, when American radio show host Scott Barley raised money from the listeners to his morning show and paid the fine on behalf of NASA. As of this writing, Barley has yet to be compensated by the space agency.

A second Skylab had been built as a backup at the same time as the one that flew, but it was never used. It is now on display at the National Air and Space Museum in Washington, DC.

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