Skylab was the United States's first, and to date only, national space station. It orbited the Earth for six years, from 1973 to 1979. It was abandoned for several years before its demise, which came during a planned re-entry which failed to burn up all of the debris before some could reach the ground, as it happened in western Australia.
- Design and Construction -
American astronomers had been envisioning the possibility of an orbiting space station, a permanent site for space operations rather than temporary flights like those accomplished by the Mercury and Gemini projects, since the late 1950s, when the military's Project Horizon imagined an ambitious space program ultimately stretching to the construction of a manned, armed outpost on the Moon. Ultimately the new organization of the National Aeronautics and Space Administration (NASA) did not make permanent space stations a priority.
However, the vision for space stations was never fully lost, kept alive as it was by speculative writers imagining future habitation in space, on the one hand, and military strategic planners, on the other. The latter never lost sight of the Soviet Union's determination to build its own space stations; indeed, the Soviet military actually launched three military space stations, under the name Almaz (Russian for Diamond). Plans percolated throughout the 1960s, encouraged by German-American Werner von Braun, until McDonnell-Douglas was contracted in 1969 to design a space station initially designated the Orbital Workshop.
The result was Skylab, based on a pair of upper stages of Saturn IVB rockets. Skylab launched in 1973 aboard a modified Saturn V rocket and achieved orbat, despite damage to its micrometeoroid shield and to its solar panels which had to be repaired by the later crew. The spacecraft was a weighty 170,000 pounds, consisting of a heavily modified Apollo moon mission spacecraft. The crew section, designed for habitation and scientific work, was the first time NASA had ever worried about providing necessary creature comforts, such as a shower and a private sleeping area, on its spacecraft.
- Human Inhabitants and Missions -
Overall, Skylab was inhabited for 171 days, although it remained in orbit for several years afterward. Three missions, in total, occupied the space station: SL-2, SL-3, and SL-4. (The designation "SL-1" was reserved for the actual launch of the space station, which was initially unmanned.) For the first time, American astronauts spent many weeks in space at a time, working as well as relaxing and playing.
Skylab's first crew, SL-2, consisted of Charles Conrad, Paul Weitz, and Joseph Kerwin. The three men faced a daunting task: the only previous space station crew, the Russian cosmonauts of Salyut 1, had survived their 23-day mission only to tragically die during re-entry. The mission was successful, lasting from May 25 to June 22. The astronauts' principal tasks were to repair the damage done during launch, replacing the damaged meteoroid shield with a less-capable sun shade which did at least cool the spacecraft enough that it could be inhabited by a crew, and then repairing the solar panel, which had failed to deploy properly and therefore left the station with a severe energy deficit.
The second crew - Alan Bean, Jack Lousma, and Owen Garriott - had a more ambitious agenda. They were in space for a total of 59 days, completing repairs to the shield and then conducting a number of medical experiments to determine potential problems of long-term living in space.
The third and last crew, Gerald Carr, William Pogue, and Edward Gibson, were the most successful, spending a then-record-setting 84 days in space. This was also the busiest Skylab mission yet, resulting in complaints from the astronauts at one point that the work schedule set was far too demanding. Pogue later translated his experiences on the space station into an educational, question-and-answer-style book about life in space aimed at youth, "How Do You Go to the Bathroom in Space?"
A fourth and final Skylab mission, Skylab 5, was planned to send Skylab into a higher orbit, but never launched. In addition, NASA built a second version of Skylab, which it originally contemplated launching as a second space station, Skylab B. It never flew, and is currently exhibited at the National Air and Space Museum.
- Abandonment and Re-Entry -
After the third habitation mission, SL-4, ended in February 1974, Skylab was left abandoned. This was not the result of a single decision: NASA continued to develop speculative plans for reoccupying the space station as late as 1978, and even intended one of the first Space Shuttle missions to be an attempt at reactivating Skylab. At the time it was abandoned, it had still held ample quantities of water and oxygen in storage, and could have replenished both through supply missions, potentially by the Space Shuttle, in the same way that the present-day International Space Station is regularly resupplied by cargo flights. At the very least, mission planners agreed, reactivating Skylab in orbit would be orders of magnitude cheaper than building an entirely new space station on the ground and launching it into orbit.
Ultimately, however, NASA found that it had run out of time. SL-4 had boosted Skylab's decaying orbit, but increased solar flares led to increased drag in low Earth orbit, which in turn led to a faster-than-expected orbital decay. In the meantime, the Space Shuttle's first flight was substantially delayed, until 1981.
The result was that, on July 11, 1979, NASA deliberately deorbited Skylab, sending it plunging into the atmosphere. It was hoped that the re-entry would be steep enough that the spacecraft would be entirely burned up. As it turned out, this occurred more slowly than expected, and substantial debris landed in western Australia. (The Shire of Esperance fined NASA for littering.) Ultimately several pieces of the debris were recovered and put on display.
- The Future of American Space Stations -
Skylab was the first and last purely American-built space station. A successor, Freedom, was announced by the Reagan administration but ultimately scrapped in favour of contributing to what became today's jointly built International Space Station. In the meantime, the Russians capitalized on their Salyut experience to launch the Mir space station in 1986. Mir was unquestionably less malfunction-prone and more successful than Skylab (although this is understandable, given that it was designed and launched a decade later and took advantage of earlier experiences in both countries' space programs).
Today, both Mir and Skylab are relics of the past, both having been sent plunging back into Earth's atmosphere. The only space station still in orbit is the International Space Station, the largest and most ambitious space project ever attempted. The International Space Station was pieced together through launches of separate modules between 1998 and the present, and will probably remain in orbit into the 2020s. At over $100 billion, it will ultimately cost at least ten times as much as Skylab, in current dollar terms.