Skylab

Overview

NASA had studied concepts for space stations, including an inflatable, donut-shaped station, since the earliest days of the space program. But it was not until the Saturn rocket came into existence in the mid-1960s that the Skylab program was born. Initially called the Apollo Applications Program, Skylab was designed to use leftover Apollo hardware to achieve extended stays by astronauts in Earth orbit.

At first there were two competing concepts.The first was the so-called “wet” workshop, where a Saturn IB rocket would be launched and fueled and its S-IVB upper stage vented and refurbished in orbit. The second was the “dry” workshop, in which the outfitting of an empty S-IVB stage would be done on the ground beforehand and launched on a Saturn V. In July 1969, while the Apollo 11 astronauts were completing their historic lunar landing mission, program managers made their decision: the “dry” workshop concept won.

The Skylab space station weighed approximately 907,108 kilograms (100 tons). It was placed into orbit by the last Saturn V launch vehicle. Three separate astronaut crews then met up with the orbiting workshop using modified Apollo Command and Service Modules (CSM) launched by smaller Saturn IB rockets.

Skylab had a habitable volume of just over 283.17 cubic meters (10,000 cubic feet). It was divided into two levels separated by a metal floor, which was actually an open grid into which the astronauts’ cleated shoes could be locked. The “upper” floor had storage lockers; a large, empty volume for conducting experiments; plus two scientific airlocks, one pointing down at Earth, the other toward the Sun. The lower floor had compartmented “rooms” with many of the comforts of home: a dining room table, three bedrooms, a work area, a shower, and a bathroom.

The largest piece of scientific equipment, attached to one end of the cylindrical workshop,was theApolloTelescope Mount (ATM), used to study the Sun in different wavelengths with no atmospheric interference. The ATM had its own electricity-generating solar panels. Skylab also had an airlock module for spacewalks (required for repairs, experiment deployments, and routine changing of film in the ATM). The Apollo Command and Service Module remained attached to the station’s multiple docking adapter while the astronauts were on board.

The space station itself was launched 14 May 1973, on the unpiloted Skylab 1 mission. Beginning only 63 seconds after the launch, however, the workshop’s combination meteorite shield and sunshade was torn loose by aerodynamic stress, taking one of the two electricity-producing solar arrays with it and preventing the other from deploying properly. The crew was supposed to have launched the next day, but they waited on the ground for 10 days while a fix was worked out (see Skylab 2).

In the course of the next nine months, three different crews lived aboard Skylab for one, two, then three months at a time. The station, which orbited at an altitude of 434.52 kilometers (269.4 statute miles), was deactivated between flights. Together, the nine Skylab astronauts chalked up a combined total of 513 days in orbit, during which they conducted thousands of experiments and observations, studying (in decreasing order of the amount of crew time spent) solar astronomy, life sciences, Earth observations, astrophysics, human/systems studies, Comet Kohoutek observations (Skylab 4 only), materials science, and student experiments.

Skylab showed the value of having humans working for long periods in orbit on a wide variety of scientific studies and proved that they could survive the ordeal. The empty Skylab station reentered and burned up in the atmosphere on 11 July 1979, more than five years after the last crew left.

Skylab Statistics

Bibliography

NASA Sources

• Compton, W. David, and Benson, Charles D. Living and Working in Space: A History of Skylab. NASA SP-4208, 1983. Available online at http://history.nasa.gov/SP-4208/sp4208.htm.
• Newkirk, Roland W., and Ertel, Ivan D., with Brooks, Courtney G. Skylab: A Chronology. NASA SP-4011, 1977. Available online at http://history.nasa.gov/SP-4011/cover.htm.
• Pitts, John A. The Human Factor: Biomedicine in the Manned Space Program to 1980. NASA SP-4213, 1985. Available online at http://history.nasa.gov/SP-4213/sp4213.htm.

Skylab Missions

Skylab 3

28 July–25 September 1973

Crew: Alan L. Bean, Jack R. Lousma, Owen K. Garriott

After an early bout of motion sickness, the three-person Skylab 3 crew settled down to a 59-day stay aboard the space station. During the flight, Owen Garriott and Jack Lousma deployed a second sunshield on a spacewalk lasting 6.5 hours, the first and longest of three Skylab 3 spacewalks. During their two months in orbit, the astronauts continued a busy schedule of experiments, including a student experiment to determine whether spiders could spin webs in weightlessness (they could). They also tested a jet-powered Astronaut Maneuvering Unit (AMU) backpack inside the spacious volume of Skylab’s forward compartment, which had been carried but never flown on Gemini missions in the 1960s. The AMU proved a capable form of one-man space transportation and helped engineers design the more sophisticated Manned Maneuvering Unit (MMU) used on the Space Shuttle in the 1980s.

Skylab 4

16 November 1973–8 February 1974

Crew: Gerald P. Carr, William R. Pogue, Edward G. Gibson

Clocking in at 84 days, 1 hour, 15 minutes, and 31 seconds, Skylab 4 remains the longest U.S. spaceflight to date. To help keep the crew in shape, a treadmill was added to the on-board bicycle-like ergometer. As a result of the exercise, the Skylab 4 crew was in better physical condition upon their return to Earth than previous Skylab crews, even though an excessive work pace had caused some tension during the flight.Comet Kohoutek was among the special targets observed by the Skylab 4 crew,as were a solar eclipse and solar flares.The astronauts conducted four spacewalks, including one on Christmas Day to view Kohoutek, and set records for time spent on experiments in every discipline from medical investigations to materials science.