Satrun V / Skylab I launch at Kennedy Space Center

2013 marks the 40th anniversary of the Skylab, America’s first space station.

Skylab began in the early 1960s when NASA managers, particularly those at the Marshall Space Flight Center, looked at ways to use modified Apollo hardware for lunar and earth-orbital scientific programs. The concepts were variously titled “Extended Apollo,” “Apollo X,” and the “Apollo Extension System.” By 1965, these studies became known as the “Apollo Applications Program,” or AAP. Two years later, the AAP proposal comprised 14 earth-orbital flights and 3 lunar missions, culminating in a two-week lunar surface expedition with a mobile laboratory. Such an expanded manned space program would need four launches each per year of both Saturn IB and Saturn V rockets.

Budget constraints forced the elimination of the lunar portion of AAP by the time of the Apollo landings and so many of AAP’s lunar exploration goals became part of Apollo that the expanded program became superfluous. AAP became strictly an earth-orbiting space station program with the elimination of the lunar expeditions. The initial concept was to use only the Saturn IB for the AAP space station. The first launch would comprise a manned CSM and the Mapping & Survey System (M&SS) module for Earth observation. Three days later, an unmanned Saturn IB was to blast off with a Multiple Docking Adapter (MDA) and airlock attached to the top of the S-IVB stage. Once the stage reached orbit, the astronauts were to rendezvous with it, attach the M&SS to one of the MDA ports, and convert the empty S-IVB into an orbiting laboratory. Electrical power for the laboratory came from two arrays of solar cells mounted on the S-IVB. The converted S-IVB was called the Orbital Workshop, or OWS.

The concept of transforming a previously live rocket stage into a space station was known as the “wet” workshop. A subsequent mission would deliver the Apollo Telescope Mount (ATM), a solar observatory, to the AAP station, where it would be docked to the MDA. The ATM was to use a LM ascent stage structure attached to a battery of telescopes where the descent stage would have been. Controls for the instruments replaced the normal LM instrument panels. Four arrays of solar panels provided electrical power for the ATM. It would have taken four launches to completely assemble the AAP cluster.

By the middle of 1969, there was a growing consensus within NASA that the wet workshop should be dropped in favor of a “dry” one launched by a Saturn V. Apollo 8’s success eliminated the need for one of the preliminary lunar missions, so a Saturn V became available for the space station program. With the dry workshop, the station would be fully outfitted before launch. The M&SS instruments would be housed inside the MDA, and the ATM would also be attached to the workshop during its initial launch. Mounted on a moveable truss, the ATM swung into position alongside the MDA once the station was in orbit. The redesigned ATM no longer used the LM Ascent Stage structure, and the instrument controls were mounted inside the MDA. The MDA had two docking ports for Apollo spacecraft.

Between the MDA and OWS, there was an airlock so astronauts could perform EVA’s without depressurizing the entire station. It had hatches on each end and an outward opening hatch for extravehicular activities. When designing the Airlock Module, engineers adapted the proven Gemini spacecraft hatch for the EVA hatch. For an EVA, the space-suited astronauts entered the airlock, sealed the end hatches, emptied the air from the compartment, then opened the Gemini-style hatch. Extravehicular activities were necessary to retrieve film canisters from the redesigned ATM. On February 17, 1970, AAP became Skylab.

Switching from the wet workshop to the dry workshop delayed the program, but NASA felt the delay was more than offset by the increased productivity by having a fully operable space station with the first launch. NASA converted S IV-B stage serial number 212 into the OWS. The converted stage had no engine. Within the workshop, what was originally the liquid hydrogen tank became the 10,000 – cubic foot laboratory and living area. The smaller liquid oxygen tank became a trash dump.

The MDA contained the control panel for the Apollo Telescope Mount (ATM), the Earth Resources Experiments Package (EREP), materials processing furnace, and other experimental equipment. Four solar arrays totaling 1,200 square feet extended from the ATM. The OWS had two solar array “wings” that were to unfold in orbit.

The Skylab OWS was launched on May 14, 1973. This was the last flight of a Saturn V, and the only two-stage version of the gigantic booster to be launched. The OWS had a thin metal shield to protect it from micrometeorites and shade it from the sun’s heat. Sixty-three seconds into the flight, the shield tore away, taking one of the two solar panels with it. The other panel was jammed shut by debris. These panels provided most of Skylab’s electricity. When Skylab reached orbit, the sun’s rays beat mercilessly on the OWS. Temperatures inside the station soared. Only the ATM solar arrays unfolded, providing just enough power to keep the station alive. Skylab was in danger of being a powerless, overheated derelict.

The launch of the first crew, comprising Pete Conrad, Joseph Kerwin, and Paul Weitz, was postponed while NASA engineers sought ways to salvage the program.

By orienting the station 45 degrees to the Sun, ground control brought Skylab’s internal temperature down to 130 degrees Fahrenheit. But, this came at a price — the ATM solar panels no longer faced the Sun, so even less power was available for critical systems. Working around the clock, teams devised several makeshift sun shades and created a tool kit to release the remaining solar array. One of the biggest challenges was that nobody knew precisely what the astronauts would find so three different shields were needed to handle various contingencies.

However, the question still remained, could Skylab be saved?


Written by Greg Kennedy on May 14th, 2013 , Space History

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