Skylab was the prototype for large orbital laboratories and demonstrated conclusively the ability of humans to function productively for prolonged periods in microgravity. Skylab also collected invaluable data about solar astronomy and Earth’s resources.
Creation of the Skylab spacecraft sprang from the desire of the National Aeronautics and Space Administration (NASA) for a program that could apply hardware developed for Apollo lunar missions to other manned spaceflight objectives. William C. Schneider was appointed the NASA project director of Skylab. By late 1965, the space agency had approved a manned Earth-orbiting laboratory as the program to follow Apollo. The laboratory was to be created inside the third stage of a Saturn 5 rocket, with crews ferried to it by Apollo command modules. Two laboratories were built, but before the first was launched on May 14, 1973, it was evident that funding constraints would prevent the second from ever going into space.
Skylab was seriously damaged when launch vibrations tore off a thermal shield, ripping away one of two large solar collectors and jamming the other closed. Mission planners considered abandoning Skylab immediately, since internal temperatures were too high and electrical power too low for it to carry out its tasks. A makeshift thermal shield was created by engineers at the Johnson Space Center in Houston, and the first crew of astronauts conducted a successful space walk
Skylab was not the first space station. The Soviet Union launched Salyut
Skylab’s sophisticated payload was geared to the project’s multiple research objectives. Highest priority was placed on gaining insight into an astronaut’s ability to withstand prolonged spaceflight, particularly the physiological effects of exposure to microgravity. Skylab was also heavily instrumented for research in solar astronomy and Earth resources observation. Finally, it carried a varied assortment of corollary experiments and science demonstrations involving investigations in astronomy, biology, botany, and metals processing. The “corollaries” and “science demos,” as the crews referred to them, were intended, at least in part, to discover technical and commercial applications for the microgravity environment, as NASA was already looking ahead to applications for future space stations.
Floating in the forward dome of the orbital workshop, Skylab 4 commander Gerald P. Carr plays in zero gravity.
As the crews went about their duties aboard Skylab, they were also providing information about two other significant sets of questions. One set of questions sought to determine whether human involvement in space missions made a sufficiently valuable contribution to justify the expense and danger. Specific experiments were included to evaluate the astronauts’ ability to use tools, but, in a sense, every task tested the arguments favoring their being there at all. A related agenda was to study the myriad astronaut-spacecraft interfaces and to evaluate the fixtures and amenities that affect the habitability of a spacecraft for missions of long duration. The astronauts were asked to comment on virtually every aspect of space living, from the decor of the station and the design of the eating utensils to the type and placement of various restraint systems at their work stations.
The interior space of Skylab was arranged with one eye to the needs of its varied research program and the other to the comfort, convenience, and psychological preferences of the crew. The largest element of the spacecraft was the orbital workshop (OWS), which was divided into two decks. One deck was designed to offer something approaching conventional ships’ quarters for the crew. The deck assumed the circular bulkhead closing off the bottom of the converted Saturn 5 third stage as the “floor” and provided a “ceiling” that gave the equivalent of normal headroom in many naval vessels. Between these two surfaces were “walls” separating the space into several compartments, which were entered through rectangular doors instead of round hatches. There were no engineering or structural requirements for this design, but it imposed an artificial sense of “up and down” on the occupants solely to evaluate how important this consideration might be. The second deck contrasted sharply with the first; it was a large open space more than 6 meters in diameter and approximately 12 meters long, containing no strong visual cues to help the crew orient themselves to a local vertical. The third manned volume, the Multiple Docking Adapter (MDA), was a tubular passageway whose circumference was lined with control panels. It presented the crew with a strong axial orientation and a very weak radial one.
About 270 different scientific and engineering experiments were dedicated to furnishing information about crew health and performance. Some thirty-five hundred hours of the astronauts’ time aboard Skylab were spent in determining when the effects of weightlessness began to have a noticeable impact on health and whether the debilitation increased gradually and continuously throughout the mission or reached a plateau and stabilized. These experiments were incredibly thorough, causing the crew to believe that they were laboratory subjects. Their activities were so rigidly monitored that every mouthful of food, every urination, and every solid waste elimination was reported. Never before had so much detailed information been collected for such a long period on a group of humans.
Skylab’s vantage point beyond the atmosphere permitted observation of the Sun in X-ray and ultraviolet wavelengths, opening up a wealth of information unobtainable on Earth. An unmanned module called the Apollo Telescope Mount (ATM), attached to the exterior of the laboratory, carried two X-ray telescopes, three ultraviolet telescopes, and a device for continuous study of the solar corona. These instruments could be operated in a semiautomatic mode according to a daily observing program, but were frequently controlled in a manual mode for ten to twelve hours per day in order to capture sudden developments, as the Sun proved to be more active than was expected.
Complicated instrumentation to study Earth from space was a rather late addition to Skylab’s payload. (Ironically, the value of Earth studies from orbit had not been generally appreciated until the Apollo flights began to underscore the fact that the planet is a delicate oasis.) The Earth Resources Experiment Package (EREP) was included primarily to evaluate designs for a variety of equipment for remotely sensing Earth’s surface and developing a database to be used in interpreting images provided by spaceborne instrumentation. As the spacecraft viewed Earth from a few hundred kilometers above, researchers on the ground gathered simultaneous information from the fields, forests, lakes, and oceans that were being imaged. The scientists needed these data, called ground truth, to evaluate the EREP images and to learn to recognize particular conditions and problems by the radiation “signatures” visible from space.
To bring a large amount of Earth’s surface under EREP’s scrutiny, Skylab followed an orbit inclined 50 degrees to the equator, allowing it to pass over every place between 50 degrees north and 50 degrees south latitude. The three manned missions to Skylab were spaced about ninety days apart so that the Earth-observing program could gather data spanning several seasons of the year.
The crew selected for Skylab 2 were Pete Conrad, Joseph P. Kerwin, and Paul J. Weitz. Alan L. Bean commanded Skylab 3, with a crew of Owen K. Garriott and Jack R. Lousma. The astronauts chosen for Skylab 4 were Gerald P. Carr (the commander), Edward G. Gibson, and William R. Pogue. The information gathered by these astronauts was invaluable for future space exploration.
Events provided the project with an immediate opportunity to dramatically demonstrate the contribution that astronauts could make to orbital operations. The first crew undoubtedly saved the $285 million spacecraft with their initial space walks, but they also repaired so many other problems with the spacecraft that they were nicknamed the “Fix-it Crew.” Subsequent crews also were frequently called on to repair equipment, and astronauts were often able to obtain solar and Earth images that their automatic equipment would have missed, by reacting more quickly or by compensating for problems.
Although Skylab demonstrated humans’ ability to make repairs and compensate for faulty equipment to an extent never thought possible when manned spaceflight began, regulating the workload proved more difficult than expected. Prior to occupancy, it had been intended that each astronaut would work eight hours a day, six days a week. It was soon evident that there was enough work to do to keep the crew busy sixteen hours a day, seven days a week. Eventually, the third crew balked and refused to accept such a grueling workload. It became apparent that the difficulties of even ordinary tasks took a heavy toll on endurance.
By the completion of the third crew’s occupancy of Skylab, the project had clearly shown humans’ ability to adjust physiologically to long-term space habitation. The degradation of the cardiovascular, skeletal, and muscular systems proved to stabilize after several weeks, and the crews that stayed in orbit longer even demonstrated an ability to recapture some of their preflight fitness through an intense regimen of appropriate exercise. This success notwithstanding, it was learned that the effects of prolonged spaceflight on the blood and vascular systems are extensive and in some respects severe. Red blood cell mass was found to decrease constantly while in orbit, with negative impact on the judgment and behavior patterns of the astronauts. This was compounded by the tendency for body fluids to migrate from the limbs to the upper body and head in microgravity conditions. A direct consequence of these observations was the recommendation that future space station crews be rotated every ninety days.
The astronauts’ psychological reactions to their home in space helped shape the design of later space laboratories. Skylab’s first deck, with its familiar up-down spatial references, was strongly preferred by eight of the nine astronauts. The Skylab crew were enthusiastic also about the porthole in their wardroom, provided for enjoyment rather than operational necessity.
Skylab surprised scientists with the dramatic success of its solar observation program. Data obtained from more than 160,000 solar photographs revealed a star that was vastly more turbulent than expected and that responded rapidly in complex ways to disturbances in its magnetic field. These discoveries caused a complete rethinking of how the Sun produces and distributes its energy.
The multispectral imaging technologies evaluated through the special EREP instrumentation led directly to a generation of powerful remote sensing satellites, which have proven extremely effective in studying an enormous range of Earth phenomena. Skylab’s Earth imaging was credited also with discovering intriguing “hills and valleys” on the ocean surface, new fishing grounds, underground water for drought-stricken West Africa, new geothermal hot spots, and valuable deposits of oil and ores. Skylab’s demise was as much a sensation as its delivery into orbit. It crashed to Earth in Western Australia on July 11, 1979.
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Bilstein, Roger E. Stages to Saturn: A Technological History of the Apollo/Saturn Launch Vehicles. Gainesville: University Press of Florida, 2003. Traces the development of the family of massive Saturn launch vehicles that carried the Apollo astronauts to the Moon and boosted Skylab into orbit. Recounts the stirring exploits of NASA’s operations, from orbital missions around Earth testing Apollo equipment to journeys to the Moon and back. -
Canby, Thomas Y. “Skylab, Outpost on the Frontier of Space.” National Geographic, October, 1974, 441-493. Presents a good overview, with readable text and exceptional photographs selected from in-flight pictures taken by the crews. Includes a photo-essay titled “Skylab Looks at Earth,” containing a representative selection of photographs illustrating some of the features visible to Skylab’s Earth imaging systems. -
Compton, W. David, and Charles D. Benson. Living and Working in Space. NASA SP-4208. Washington, D.C.: U.S. Government Printing Office, 1983. Provides a detailed official overview of the Skylab program from beginning to end, including the results of its research investigations. Intended for the general reader, the volume is well illustrated and more historical than technical. -
Cooper, Henry S. F., Jr. House in Space. New York: Holt, Rinehart and Winston, 1976. A highly readable discussion. Cooper has captured the essence of the experience of living for weeks aboard the spacecraft. Suitable for high school and adult readers, the book illuminates both the news-making triumphs and many lesser moments of pleasure and frustration. Contains black-and-white photographs. No index. -
Eddy, John A. A New Sun: The Solar Results from Skylab. NASA SP-402. Washington, D.C.: Scientific and Technical Information Office, 1979. A compendium of the photographs obtained with Skylab’s ATM, together with background information and a description of the instruments. Text and photographs are ample and well organized in this 200-page book, suitable for laypersons with a good understanding of general science. -
Gibson, Edward G. “The Sun as Never Seen Before.” National Geographic, October, 1974, 493-503. Brief, nontechnical article highlights the discoveries made in Skylab’s solar observing program. Illustrated with spectacular photographs of the Sun and accompanied by text prepared by the science pilot of Skylab 4. Conveys some of the reasons for scientific enthusiasm about Skylab’s solar data. Recommended for a wide audience. -
Robinson, George S. “The Biology of Skylab.” In Living in Outer Space. Washington, D.C.: Public Affairs Press, 1975. Summarizes the major conclusions from the Skylab Life Sciences Experiments pertaining to human adaptation to spaceflight, and their implications for space colonization, including the legal and psychological ramifications of the impairments in human physiology. Robinson, a law scholar and NASA administrator, is writing for the advanced reader and specialist. -
Shayler, David J. Skylab: America’s Space Station. Chichester, England: Springer-Praxis, 2001. David Shayler tells the Skylab story well, but without footnotes. From the perspective of more than a quarter-century after the missions, Shayler uses official NASA documentation and interviews with the astronauts and key personnel to present the story of Skylab. Also presents an assessment of lessons learned in the context of current programs. -
“Skylab.” In Life in Space. Alexandria, Va.: Time-Life Books, 1983. A photo-essay containing several pages of text covering aspects of living aboard the spacecraft, from coping with weightlessness and space sickness to the equipment problems that plagued the first crew and the chaotic jumble of unstowed equipment with which the last crew struggled.
Russians Launch the Salyut Space Station
Launch of the First Earth Resources Technology Satellite
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Spacelab 1 Is Launched Aboard the Space Shuttle
First Permanently Manned Space Station Is Launched
International Space Station Is Manned