Skylab
Overview
 
Skylab was a space station
Space station
A space station is a spacecraft capable of supporting a crew which is designed to remain in space for an extended period of time, and to which other spacecraft can dock. A space station is distinguished from other spacecraft used for human spaceflight by its lack of major propulsion or landing...

 launched and operated by NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...

, the space agency of the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

. Skylab orbited the Earth from 1973 to 1979, and included a workshop, a solar observatory, and other systems. It was launched unmanned by a modified Saturn V
Saturn V
The Saturn V was an American human-rated expendable rocket used by NASA's Apollo and Skylab programs from 1967 until 1973. A multistage liquid-fueled launch vehicle, NASA launched 13 Saturn Vs from the Kennedy Space Center, Florida with no loss of crew or payload...

 rocket, with a mass of 169950 pounds (77 MT). Three manned missions to the station, conducted between 1973 and 1974 using the Apollo Command/Service Module (CSM) atop the smaller Saturn IB
Saturn IB
The Saturn IB was an American launch vehicle commissioned by the National Aeronautics and Space Administration for use in the Apollo program...

, each delivered a three-astronaut crew.
Discussions
Encyclopedia
Skylab was a space station
Space station
A space station is a spacecraft capable of supporting a crew which is designed to remain in space for an extended period of time, and to which other spacecraft can dock. A space station is distinguished from other spacecraft used for human spaceflight by its lack of major propulsion or landing...

 launched and operated by NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...

, the space agency of the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

. Skylab orbited the Earth from 1973 to 1979, and included a workshop, a solar observatory, and other systems. It was launched unmanned by a modified Saturn V
Saturn V
The Saturn V was an American human-rated expendable rocket used by NASA's Apollo and Skylab programs from 1967 until 1973. A multistage liquid-fueled launch vehicle, NASA launched 13 Saturn Vs from the Kennedy Space Center, Florida with no loss of crew or payload...

 rocket, with a mass of 169950 pounds (77 MT). Three manned missions to the station, conducted between 1973 and 1974 using the Apollo Command/Service Module (CSM) atop the smaller Saturn IB
Saturn IB
The Saturn IB was an American launch vehicle commissioned by the National Aeronautics and Space Administration for use in the Apollo program...

, each delivered a three-astronaut crew. On the third mission, an additional Apollo / Saturn IB stood by, ready for launch if needed to rescue the crew in orbit.

Skylab included an Apollo Telescope Mount
Apollo Telescope Mount
The Apollo Telescope Mount, or ATM, is the name of a solar observatory that was attached to Skylab, the first US space station.The ATM was one of a number of projects that came out of the late 1960s Apollo Applications Program, which studied a wide variety of ways to use the infrastructure...

 (a multi-spectral solar observatory), Multiple Docking Adapter with two docking ports, Airlock Module with EVA hatches, and the Orbital Workshop, the main habitable volume of the station. Power came from solar arrays, as well as fuel cells in the docked Apollo CSM. The rear of the station included a large waste tank, propellant tanks for maneuvering jets, and a heat radiator.

The station was damaged at launch when the micrometeroid shield separated from the station and tore away, depriving the station of most of its power, removing protection from intense solar heating, and threatening to make the station unusable. The first crew was able to save it in the first ever in-space major repair, by deploying a replacement heat shade and freeing the single remaining, jammed main solar array.

Numerous scientific experiments were conducted aboard Skylab during its operational life, and crews were able to confirm the existence of coronal holes in the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...

. The Earth Resources Experiment Package (EREP), was used to view the Earth with sensors that recorded data in the visible, infrared, and microwave spectral regions. Thousands of photographs of Earth were taken, and records for human time spent in orbit were extended.

Plans were made to refurbish and reuse Skylab, using the Space Shuttle
Space Shuttle
The Space Shuttle was a manned orbital rocket and spacecraft system operated by NASA on 135 missions from 1981 to 2011. The system combined rocket launch, orbital spacecraft, and re-entry spaceplane with modular add-ons...

 to boost its orbit and repair it. However, development of the Shuttle was delayed, and Skylab reentered Earth's atmosphere and disintegrated in 1979, with debris striking portions of Western Australia
Western Australia
Western Australia is a state of Australia, occupying the entire western third of the Australian continent. It is bounded by the Indian Ocean to the north and west, the Great Australian Bight and Indian Ocean to the south, the Northern Territory to the north-east and South Australia to the south-east...

.

After Skylab's demise, the focus shifted to the reusable Spacelab
Spacelab
Spacelab was a reusable laboratory used on certain spaceflights flown by the Space Shuttle. The laboratory consisted of multiple components, including a pressurized module, an unpressurized carrier and other related hardware housed in the Shuttle's cargo bay...

 module, an orbital workshop that could be deployed from the Space Shuttle and returned to Earth. The next American space station project was Space Station Freedom
Space Station Freedom
Space Station Freedom was a NASA project to construct a permanently manned Earth-orbiting space station in the 1980s. Although approved by then-president Ronald Reagan and announced in the 1984 State of the Union Address, Freedom was never constructed or completed as originally designed, and after...

, which was never completed, although it eventually led to the construction of the US Orbital Segment
US Orbital Segment
The US Orbital Segment is the name given to the components of the International Space Station constructed and operated by the US National Aeronautics and Space Administration , European Space Agency , Canadian Space Agency and Japan Aerospace Exploration Agency .The segment currently consists of...

 of the International Space Station
International Space Station
The International Space Station is a habitable, artificial satellite in low Earth orbit. The ISS follows the Salyut, Almaz, Cosmos, Skylab, and Mir space stations, as the 11th space station launched, not including the Genesis I and II prototypes...

, starting in 1998. Shuttle-Mir was another project, and led to the U.S. funding Spektr
Spektr
Spektr was the fifth module of the Mir Space Station. The module was designed for remote observation of Earth's environment containing atmospheric and surface research equipment...

, Priroda
Priroda
The Priroda module was the seventh and final module of the Mir Space Station. Its primary purpose was to conduct Earth resource experiments through remote sensing and to develop and verify remote sensing methods...

, and the Mir Docking Module
Mir Docking Module
The Stykovochnyy Otsek , GRAU index 316GK, otherwise known as the Mir docking module or SO, was the sixth module of the Russian space station Mir, launched in November 1995 aboard the...

 in the 1990s.

Background

The exact origin of the project is difficult to pinpoint because a number of different but related proposals were developed by various government agencies before Skylab itself was launched.

Early studies

A key event took place in 1959, when rocket scientist and space architect Wernher von Braun
Wernher von Braun
Wernher Magnus Maximilian, Freiherr von Braun was a German rocket scientist, aerospace engineer, space architect, and one of the leading figures in the development of rocket technology in Nazi Germany during World War II and in the United States after that.A former member of the Nazi party,...

, then head of the Development Operations Division at the Army Ballistic Missile Agency
Army Ballistic Missile Agency
The Army Ballistic Missile Agency was the agency formed to develop the US Army's first intermediate range ballistic missile. It was established at Redstone Arsenal on February 1, 1956 and commanded by Major General John B...

, submitted his final Project Horizon
Project Horizon
Project Horizon was a study to determine the feasibility of constructing a scientific / military base on the Moon. On June 8, 1959, a group at the Army Ballistic Missile Agency produced for the U.S. Department of the Army a report entitled Project Horizon, A U.S. Army Study for the Establishment...

 plans to the U.S. Army. The overall goal of Horizon was to place a human on the Moon
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...

, a mission that would soon be taken over by the rapidly forming NASA. Although concentrating on the Moon missions, von Braun also detailed an orbiting laboratory built out of an Horizon upper stage, an idea used for Skylab.

A number of NASA centers studied various space station designs in the early 1960s. Studies generally looked at platforms launched by the Saturn V, followed up by crews launched on Saturn IB using an Apollo Command/Service Module, or a Gemini capsule
Project Gemini
Project Gemini was the second human spaceflight program of NASA, the civilian space agency of the United States government. Project Gemini was conducted between projects Mercury and Apollo, with ten manned flights occurring in 1965 and 1966....

on a Titan II-C
Titan II GLV
The Titan II GLV or Gemini-Titan was an American expendable launch system derived from the Titan II missile, which was used to launch twelve Gemini missions for NASA between 1964 and 1966...

, the latter being much less expensive in the case where cargo was not needed. Proposals ranged from an Apollo-based station with two to three men, or a small "canister" for four men with Gemini capsules resupplying it, to a large, rotating station with 24 men and an operating lifetime of about five years.

Air Force competition

In September 1963, NASA and the Department of Defense
United States Department of Defense
The United States Department of Defense is the U.S...

 (DoD) agreed to cooperate in building a space station. In December, the US Air Force
United States Air Force
The United States Air Force is the aerial warfare service branch of the United States Armed Forces and one of the American uniformed services. Initially part of the United States Army, the USAF was formed as a separate branch of the military on September 18, 1947 under the National Security Act of...

 nonetheless announced Manned Orbital Laboratory (MOL), a small space station primarily intended for photo reconnaissance using large telescopes directed by a two-man crew. The station was the same diameter as a Titan II
Titan II GLV
The Titan II GLV or Gemini-Titan was an American expendable launch system derived from the Titan II missile, which was used to launch twelve Gemini missions for NASA between 1964 and 1966...

 upper stage, and would be launched with the crew riding atop in a modified Gemini capsule with a hatch cut into the heat shield
Heat shield
A heat shield is designed to shield a substance from absorbing excessive heat from an outside source by either dissipating, reflecting or simply absorbing the heat...

 on the bottom of the capsule. MOL competed for funding with a NASA station for the next five years, and led to changes being made to the NASA plans, so that they would resemble MOL less.

Apollo Applications Program

After landing on the moon in 1969, NASA management was concerned about losing the 400,000 workers involved in Apollo. It set up the Apollo Logistic Support System Office, originally intended to study various ways to modify the Apollo hardware for scientific missions. The office initially proposed a number of projects for direct scientific study, including an extended-stay lunar mission which required two Saturn V launchers, a "lunar truck" based on the Lunar Module (LEM), a large manned solar telescope using an LEM as its crew quarters, and small space stations using a variety of LEM or CSM-based hardware. Although it did not look at the space station specifically, over the next two years the office would become increasingly dedicated to this role. In August 1965, the office was renamed, becoming the Apollo Applications Program (AAP).

As part of their general work, in August 1964 the Manned Spacecraft Center
Lyndon B. Johnson Space Center
The Lyndon B. Johnson Space Center is the National Aeronautics and Space Administration's center for human spaceflight training, research and flight control. The center consists of a complex of 100 buildings constructed on 1,620 acres in Houston, Texas, USA...

 (MSC) presented studies on an expendable lab known as Apollo "X", short for Apollo Extension System. "Apollo X" would have replaced the LEM carried on the top of the S-IVB
S-IVB
The S-IVB was built by the Douglas Aircraft Company and served as the third stage on the Saturn V and second stage on the Saturn IB. It had one J-2 engine...

 stage with a small space station slightly larger than the CSM's service area, containing supplies and experiments for missions between 15 and 45 days' duration. Using this study as a baseline, a number of different mission profiles were looked at over the next six months.

Wet workshop

Wernher von Braun proposed a more ambitious plan to build a much larger station. His design replaced the S-IVB third stage of a complete Saturn V with an aeroshell, primarily as an adapter for the CSM on top. Inside the shell was a cylindrical equipment section slightly smaller in diameter than the CSM. On reaching orbit, the S-II
S-II
The S-II was the second stage of the Saturn V rocket. It was built by North American Aviation. Using liquid hydrogen and liquid oxygen it had five J-2 engines in a cross pattern...

 second stage would be vented to remove any remaining hydrogen fuel, then the equipment section would be slid into it via a large inspection hatch. The station filled the entire interior of the S-II stage's hydrogen tank, with the equipment section forming a "spine" and living quarters between it and the walls of the booster. This would have resulted in a very large 33 by living area. Power was to be provided by solar cell
Solar cell
A solar cell is a solid state electrical device that converts the energy of light directly into electricity by the photovoltaic effect....

s lining the outside of the S-II stage.

One problem with this proposal was that it required a dedicated Saturn V launch to fly the station. Engineers could not "piggyback" the station's launch on a lunar mission, which required a working S-IVB stage. At the time the design was being proposed, all of the then-contracted Saturn Vs were already earmarked for Moon missions. Further work led to the idea of building a smaller station based on the S-IVB instead, launching it on a surplus Saturn IB. Several planned Earth-orbit test missions for the LEM and CSM had been canceled, leaving a number of Saturn IBs free for use.

Since the Saturn I had a much lower throw-weight
Throw-weight
Throw-weight is a measure of the effective weight of ballistic missile payloads. It is measured in kilograms or metric tons. Throw-weight equals the total weight of a missile's warheads, reentry vehicles, self-contained dispensing mechanisms, penetration aids, and guidance systems — generally all...

 capability, the S-IV
S-IV
The S-IV was the second stage of the Saturn I, a rocket-powered launch vehicle used by NASA for early flights in the Apollo program.The S-IV was manufactured by the Douglas Aircraft Company and later modified by them to the S-IVB, a similar but distinct stage used on the Saturn IB and Saturn V...

 stage could not be left empty; its thrust would be needed for the mission. This limitation led to the development of the "wet workshop" concept, which led naturally out of von Braun's idea of using an existing stage after its fuel had burned off. However, in this case the station was to be built out of the S-IVB stage itself, as opposed to the S-II below it. A number of S-IVB-based stations were studied at MSC, but even the earliest, from mid-1965, had much in common with the Skylab design that actually flew. An airlock
Airlock
An airlock is a device which permits the passage of people and objects between a pressure vessel and its surroundings while minimizing the change of pressure in the vessel and loss of air from it...

 was placed in the equipment area immediately below where the LEM sat on a Moon mission, and a minimum amount of equipment was installed in the tank itself in order to avoid taking up too much fuel volume. After launch, a follow-up mission launched by a Saturn IB would carry up additional equipment in place of its LEM, including solar panels, an equipment section and docking adapter, and various experiments. Douglas Aircraft, builder of the S-IVB stage, was asked to prepare proposals along these lines. The company had for several years been proposing stations based on the S-IV that the S-IVB replaced.

On 1 April 1966, MSC sent out contracts to Douglas, Grumman, and McDonnell
McDonnell Aircraft
The McDonnell Aircraft Corporation was an American aerospace manufacturer based in St. Louis, Missouri. The company was founded on July 16, 1939 by James Smith McDonnell, and was best known for its military fighters, including the F-4 Phantom II, and manned spacecraft including the Mercury capsule...

 for the conversion of a S-IVB spent stage, under the name Saturn S-IVB spent-stage experiment support module (SSESM). In May, astronauts voiced concerns over the purging of the stage's hydrogen tank in space. Nevertheless, in late July it was announced that the Orbital Workshop would be launched as a part of Apollo mission AS-209, originally one of the Earth-orbit CSM test launches, followed by two Saturn I/CSM crew launches, AAP-1 and AAP-2.

MOL remained AAP's chief competitor for funds, although the two programs cooperated on technology. NASA considered flying experiments on MOL, or using its Titan IIIC booster instead of the much more expensive Saturn IB, but decided that the Air Force station was not large enough, and that converting Apollo hardware for use with Titan would be too slow and too expensive. The DoD later canceled MOL in June 1969.

Dry workshop

Design work continued over the next two years, in an era of shrinking budgets. In August 1967, NASA announced that the lunar mapping and base construction missions examined by the AAP were being canceled. Only the Earth-orbiting missions remained, namely the Orbital Workshop and Apollo Telescope Mount
Apollo Telescope Mount
The Apollo Telescope Mount, or ATM, is the name of a solar observatory that was attached to Skylab, the first US space station.The ATM was one of a number of projects that came out of the late 1960s Apollo Applications Program, which studied a wide variety of ways to use the infrastructure...

 solar observatory. Later, several Moon missions were canceled as well, originally to be Apollo missions 18 through 20. The cancellation of these missions freed up three Saturn V boosters for the AAP program. Although this would have allowed them to develop von Braun's original S-II based mission, by this time so much work had been done on the S-IV based design that work continued on this baseline. With the extra power available, the wet workshop was no longer needed; the S-IC and S-II lower stages could launch a "dry workshop", with its interior already prepared, directly into orbit.

Habitability

A dry workshop simplified plans for the interior of the station. Industrial design
Industrial design
Industrial design is the use of a combination of applied art and applied science to improve the aesthetics, ergonomics, and usability of a product, but it may also be used to improve the product's marketability and production...

 firm Raymond Loewy
Raymond Loewy
Raymond Loewy was an industrial designer, and the first to be featured on the cover of Time Magazine, on October 31, 1949. Born in France, he spent most of his professional career in the United States...

/William Snaith recommended emphasizing habitability
Habitability
Habitability is the conformance of a residence or abode to the implied warranty of habitability. A residence that complies is said to be "habitable". It is an implied warranty or contract, meaning it does not have to be an express contract, covenant, or provision of a contract...

 and comfort for the astronauts by, for example, providing a wardroom
Wardroom
The wardroom is the mess-cabin of naval commissioned officers above the rank of Midshipman. The term the wardroom is also used to refer to those individuals with the right to occupy that wardroom, meaning "the officers of the wardroom"....

 for meals and relaxation, and a window to view the Earth and space, although astronauts who participated in Skylab planning were dubious about the designers' focus on areas such as color scheme
Color scheme
In color theory, a color scheme is the choice of colors used in design for a range of media. For example, the use of a white background with black text is an example of a basic and commonly default color scheme in web design....

s. Habitability had not previously been an area of concern when building spacecraft, due to their small volume and brief mission durations, but the Skylab missions would last for months. NASA sent a scientist on Jacques Piccard's Ben Franklin submarine in the Gulf Stream
Gulf Stream
The Gulf Stream, together with its northern extension towards Europe, the North Atlantic Drift, is a powerful, warm, and swift Atlantic ocean current that originates at the tip of Florida, and follows the eastern coastlines of the United States and Newfoundland before crossing the Atlantic Ocean...

 in July and August 1969, to learn how six people would live in an enclosed space for four weeks.

Astronauts were uninterested in watching movies on a proposed entertainment center
Entertainment center
A home entertainment center is a piece of furniture seen in many homes in North America, which houses major electronic items, such as a television set, a VCR and/or DVD player, stereo components , and cable or satellite television receivers...

 or playing games, but did want books and individual music choices. Food was also important; early Apollo crews complained about its quality, and a NASA volunteer found living on the Apollo food for four days on Earth to be intolerable; its taste and composition, in the form of cubes and squeeze tubes, were unpleasant. Skylab food significantly improved on its predecessors by prioritizing edibility over scientific needs.

Each astronaut had a private sleeping area the size of a small walk-in closet, with a curtain, sleeping bag
Sleeping bag
A sleeping bag is a protective "bag" for a person to sleep in, essentially a blanket that can be closed with a zipper or similar means, and functions as a bed in situations where a bed is unavailable . Its primary purpose is to provide warmth and thermal insulation...

, and locker. Designers also added a shower and a toilet
Space toilet
A space toilet, or zero gravity toilet, is a toilet that can be used in a weightless environment. In the absence of weight the collection and retention of liquid and solid waste is directed by use of air flow. Since the air used to direct the waste is returned to the cabin, it is filtered...

; the latter was both for comfort and to obtain precise urine and feces samples for examination on Earth.

Completion and launch

On 8 August 1969, the McDonnell Douglas
McDonnell Douglas
McDonnell Douglas was a major American aerospace manufacturer and defense contractor, producing a number of famous commercial and military aircraft. It formed from a merger of McDonnell Aircraft and Douglas Aircraft in 1967. McDonnell Douglas was based at Lambert-St. Louis International Airport...

 Corporation received a contract for the conversion of two existing S-IVB stages to the Orbital Workshop configuration. One of the S-IV test stages was shipped to McDonnell Douglas for the construction of a mock-up in January 1970. The Orbital Workshop was renamed "Skylab" in February 1970 as a result of a NASA contest. The actual stage that flew was the upper stage of the AS-212 rocket (the S-IVB stage - S-IVB 212). The mission computer used aboard Skylab was the IBM
IBM
International Business Machines Corporation or IBM is an American multinational technology and consulting corporation headquartered in Armonk, New York, United States. IBM manufactures and sells computer hardware and software, and it offers infrastructure, hosting and consulting services in areas...

 System/4Pi TC-1, a relative of the AP-101 Space Shuttle computers.

Skylab was launched 14 May 1973 by a Saturn V (the last launch of such a rocket) with the upper stage removed, but with the avionics remaining in the same position (different from the Saturn INT-21
Saturn INT-21
The Saturn INT-21 was a study for an American orbital launch vehicle of the 1970s. It was derived from the Saturn V rocket used for the Apollo program, using its first and second stages, but lacking the third stage. The guidance unit would be moved from the top of the third stage to the top of the...

 rocket, which could launch payloads not based on the S-IVB) into a 235-nautical-mile (435-km) orbit. The launch is sometimes referred to as Skylab 1, or SL-1. Severe damage was sustained during launch and deployment, including the loss of the station's micrometeoroid
METEOR
METEOR is a metric for the evaluation of machine translation output. The metric is based on the harmonic mean of unigram precision and recall, with recall weighted higher than precision...

 shield/sun shade and one of its main solar panels. Debris from the lost micrometeoroid shield further complicated matters by pinning the remaining solar panel to the side of the station, preventing its deployment and thus leaving the station with a huge power deficit.

Manned missions

Three manned missions were made to Skylab: SL-2
Skylab 2
-Backup crew:-Support crew:*Robert L. Crippen*Richard H. Truly*Henry W. Hartsfield, Jr*William E. Thornton-Mission parameters:*Mass: 19,979 kg*Maximum Altitude: 440 km*Distance: 18,536,730.9 km...

, SL-3
Skylab 3
Skylab 3 was the second manned mission to Skylab. The Skylab 3 mission started July 28, 1973, with the launch of three astronauts on the Saturn IB rocket, and lasted 59 days, 11 hours and 9 minutes...

 and SL-4
Skylab 4
Skylab 4 was the fourth Skylab mission and placed the third and final crew on board the space station. The mission started November 16, 1973 with the launch of three astronauts on a Saturn IB rocket, and lasted 84 days, 1 hour and 16 minutes...

 (see also the Mission designations section below).

The station underwent extensive repair during a spacewalk (extra-vehicular activity, or EVA) by the crew of the SL-2 mission, which launched on 25 May 1973 atop a Saturn IB. If the crew had failed to repair Skylab in time, the plastic insulation inside the station would have melted, releasing poisonous gas and making Skylab completely uninhabitable. They stayed in orbit with Skylab for 28 days. Two additional missions followed, with the launch dates of 28 July 1973 (SL-3) and 16 November 1973 (SL-4), and mission durations of 59 and 84 days, respectively. The last Skylab crew returned to the Earth on 8 February 1974.

Orbital operations

Skylab orbited Earth 2,476 times during the 171 days and 13 hours of its occupation during the three manned Skylab missions. Astronauts performed ten spacewalks, totaling 42 hours and 16 minutes. Skylab logged about 2,000 hours of scientific and medical experiments, 127,000 frames of film of the Sun and 46,000 of the Earth. Solar experiments included photographs of eight solar flare
Solar flare
A solar flare is a sudden brightening observed over the Sun surface or the solar limb, which is interpreted as a large energy release of up to 6 × 1025 joules of energy . The flare ejects clouds of electrons, ions, and atoms through the corona into space. These clouds typically reach Earth a day...

s, and produced valuable results that scientists stated would have been impossible to obtain with unmanned spacecraft. The existence of the Sun's coronal holes
Coronal holes
Coronal holes are areas where the Sun's corona is darker, colder, and has lower-density plasma than average. These were found when X-ray telescopes in the Skylab mission were flown above the Earth's atmosphere to reveal the structure of the corona. Coronal holes are linked to unipolar...

 were confirmed because of these efforts. Many of the experiments conducted investigated the astronauts' adaptation to extended periods of microgravity.

A typical day began at 6 AM Central Time Zone
Central Time zone
In North America, the Central Time Zone refers to national time zones which observe standard time by subtracting six hours from UTC , and daylight saving, or summer time by subtracting five hours...

. Although the toilet was small and noisy, both veteran astronauts—who had endured earlier missions' rudimentary waste-collection systems—and rookies complimented it. The first crew enjoyed taking a shower once a week, but found drying themselves in weightlessness and vacuuming excess water difficult; later crews usually cleaned themselves daily with wet washcloths instead of using the shower. Astronauts also found that bending over in weightlessness to put on socks or tie shoelaces strained their stomach muscles.

Breakfast began at 7 AM. Astronauts usually stood to eat, as sitting in microgravity also strained their stomach muscles. They reported that their food—although greatly improved from Apollo—was bland and repetitive, and weightlessness caused utensils, food containers, and bits of food to float away; also, gas in their drinking water contributed to flatulence
Flatulence
Flatulence is the expulsion through the rectum of a mixture of gases that are byproducts of the digestion process of mammals and other animals. The medical term for the mixture of gases is flatus, informally known as a fart, or simply gas...

. After breakfast and preparation for lunch, experiments, tests and repairs of spacecraft systems and, if possible, 90 minutes of physical exercise followed. After dinner, which was scheduled for 6 PM, crews performed household chores and prepared for the next day's experiments. Following lengthy daily instructions (some of which were up to 15 meters long) sent via teleprinter
Teleprinter
A teleprinter is a electromechanical typewriter that can be used to communicate typed messages from point to point and point to multipoint over a variety of communication channels that range from a simple electrical connection, such as a pair of wires, to the use of radio and microwave as the...

, the crews were often busy enough to postpone sleep.

Each Skylab mission set a record for the amount of time astronauts spent in space. The station offered "a highly satisfactory living and working environment for crews." Although it had a dart set
Darts
Darts is a form of throwing game where darts are thrown at a circular target fixed to a wall. Though various boards and games have been used in the past, the term "darts" usually now refers to a standardised game involving a specific board design and set of rules...

, playing cards, and other recreational equipment in addition to books and music players, the window with its view of Earth became the most popular way to relax in orbit.

Post SL-4 plans

Skylab was abandoned after the end of the SL-4 mission in February 1974. At the time, NASA discouraged any discussion of additional visits due to the station's age, but in 1977 and 1978, when the agency still believed the Space Shuttle
Space Shuttle
The Space Shuttle was a manned orbital rocket and spacecraft system operated by NASA on 135 missions from 1981 to 2011. The system combined rocket launch, orbital spacecraft, and re-entry spaceplane with modular add-ons...

 would be ready by 1979, it completed two studies on reusing the station. By September 1978, the agency believed Skylab was safe for crews, with all major systems intact and operational. It still had 180 man-days of water and 420 man-days of oxygen, and astronauts could refill both; the station could hold up to about 600 to 700 man-days of drinkable water and 420 man-days of food.

The studies cited several benefits from reusing Skylab, which one called a resource worth "hundreds of millions of dollars" already in orbit. Since no more Saturn Vs existed after the end of the Apollo program, four to five shuttle flights and extensive space architecture
Space architecture
Space architecture, in its simplest definition, is the theory and practice of designing and building inhabited environments in outer space. The architectural approach to spacecraft design addresses the total built environment, drawing from diverse disciplines including physiology, psychology, and...

 would have been needed to build another station as large as Skylab's 12400 cubic feet (351.1 m³) volume. Its ample size—much greater than that of the shuttle alone, or even the shuttle plus Spacelab
Spacelab
Spacelab was a reusable laboratory used on certain spaceflights flown by the Space Shuttle. The laboratory consisted of multiple components, including a pressurized module, an unpressurized carrier and other related hardware housed in the Shuttle's cargo bay...

—was enough, with some modifications, for up to seven astronauts of both sexes, and experiments needing a long duration in space; even a movie projector for recreation was possible.

Proponents of Skylab's reuse also said repairing and upgrading Skylab would provide information on the results of long-duration exposure to space for future stations. The most serious issue for reactivation was stationkeeping, as one of the station's gyroscope
Gyroscope
A gyroscope is a device for measuring or maintaining orientation, based on the principles of angular momentum. In essence, a mechanical gyroscope is a spinning wheel or disk whose axle is free to take any orientation...

s had failed and the attitude control system
Attitude control system
In spaceflight, the attitude control system or attitude determination and control system of a spacecraft consists of equipment to measure, report and change the orientation of the vehicle.- Components :...

 needed refueling; these issues would need EVA to fix or replace. The station had not been designed for extensive resupply. However, while plans had originally called for Skylab crews to perform only limited maintenance they successfully made major repairs during EVA, such as the SL-2 crew's deploying of the solar panel and the SL-4 crew's repair of the primary coolant loop. The SL-2 crew fixed one item during EVA by, reportedly, "hit[ting] it with [a] hammer."

Some studies also said, beyond the opportunity for space construction and maintenance experience, reactivating the station would free up shuttle flights for other uses, and reduce the need to modify the shuttle for long-duration missions
Extended Duration Orbiter
The Extended Duration Orbiter program was a project by NASA to prepare for long-term microgravity research aboard Space Station Freedom, which later evolved into the International Space Station. Scientists and NASA needed practical experience in managing progressively longer times for their...

. Even if the station were not manned again, went one argument, it would serve as a useful experimental platform.

Shuttle mission plans

The reactivation would likely have occurred in four phases:
  1. An early Space Shuttle flight would have boosted Skylab to a higher orbit, adding five years of operational life. The shuttle might have pushed or towed the station, but attaching a booster—the Teleoperated Retrieval System (TRS)—to the station would have been more likely, based on astronauts' training for the task. Martin Marietta
    Martin Marietta
    Martin Marietta Corporation was an American company founded in 1961 through the merger of The Martin Company and American-Marietta Corporation. The combined company became a leader in chemicals, aerospace, and electronics. In 1995, it merged with Lockheed Corporation to form Lockheed Martin. The...

     won the contract for the $26 million TRS, which contained about three tons of propellant, and began work in April 1978.
  2. In two shuttle flights, Skylab would have been refurbished. In January 1982, the first mission would have attached a docking adapter and conducted repairs. In August 1983, a second crew would have replaced several system components.
  3. In March 1984, shuttle crews would have attached a solar-powered Power Expansion Package, refurbished scientific equipment, and conducted 30- to 90-day missions using the Apollo Telescope Mount and the earth resources experiments.
  4. Over five years, Skylab would have been expanded to accommodate six to eight astronauts, with a new large docking/interface module, additional logistics modules, Spacelab modules and pallets, and an orbital vehicle space dock using the shuttle's external tank.


The first three phases would have required about $60 million in 1980s dollars, not including launch costs.

After departure

After a boost of 6.8 miles (10.9 km) by SL-4's Apollo CSM before its departure, Skylab was left in a parking orbit
Parking orbit
A parking orbit is a temporary orbit used during the launch of a satellite or other space probe. A launch vehicle boosts into the parking orbit, then coasts for a while, then fires again to enter the final desired trajectory...

 of 269 miles (432.9 km) by 283 miles (455.4 km) that was expected to last until at least the early 1980s, based on estimates of the 11-year sunspot cycle that began in 1976. At the end of SL-4, only one Saturn IB rocket remained in the inventory—it was later used for Apollo-Soyuz Test Project
Apollo-Soyuz Test Project
-Backup crew:-Crew notes:Jack Swigert had originally been assigned as the command module pilot for the ASTP prime crew, but prior to the official announcement he was removed as punishment for his involvement in the Apollo 15 postage stamp scandal.-Soyuz crew:...

—while all other Saturn IB and Saturn V rocket parts had been donated to museums. NASA began considering the potential risks of a space station reentry as early as 1962, but decided to not incorporate a retrorocket
Retrorocket
A retrorocket is a rocket engine providing thrust opposing the motion of a spacecraft, thereby causing it to decelerate.-History:...

 system in Skylab due to cost and acceptable risk.

The spent 49-ton Saturn V
Saturn V
The Saturn V was an American human-rated expendable rocket used by NASA's Apollo and Skylab programs from 1967 until 1973. A multistage liquid-fueled launch vehicle, NASA launched 13 Saturn Vs from the Kennedy Space Center, Florida with no loss of crew or payload...

 S-II
S-II
The S-II was the second stage of the Saturn V rocket. It was built by North American Aviation. Using liquid hydrogen and liquid oxygen it had five J-2 engines in a cross pattern...

 stage which had launched Skylab in 1973 remained in orbit for almost two years, and made an uncontrolled reentry on January 11, 1975. Some debris, most prominently the five heavy J-2 engines, likely survived to impact in the North Atlantic Ocean. Although this event did not receive heavy media or public attention, it was followed closely by NASA and the Air Force, and helped emphasize the need for improved planning and public awareness for Skylab's eventual reentry.

Solar activity

Greater-than-expected solar activity heated the outer layers of the Earth's atmosphere and thereby increased drag on Skylab. By late 1977, NORAD accurately forecast a reentry in mid-1979; a National Oceanic and Atmospheric Administration
National Oceanic and Atmospheric Administration
The National Oceanic and Atmospheric Administration , pronounced , like "noah", is a scientific agency within the United States Department of Commerce focused on the conditions of the oceans and the atmosphere...

 (NOAA) scientist criticized NASA for using an inaccurate model for the second most-intense sunspot cycle in a century, and for ignoring NOAA predictions published in 1976.

The reentry of the USSR's nuclear powered Cosmos 954
Cosmos 954
Kosmos 954 was a Soviet Radar Ocean Reconnaissance Satellite with an onboard nuclear reactor. The satellite was launched on September 18, 1977 and was designed to track nuclear submarines...

 in January 1978, and the resulting radioactive debris fall in northern Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

, drew more attention to Skylab's orbit. Although Skylab did not contain radioactive materials, the State Department
United States Department of State
The United States Department of State , is the United States federal executive department responsible for international relations of the United States, equivalent to the foreign ministries of other countries...

 warned NASA about the potential diplomatic repercussions of station debris. Ground controllers re-established contact with Skylab in March 1978 and recharged its batteries. Although NASA worked on plans to reboost Skylab with the Space Shuttle
Space Shuttle
The Space Shuttle was a manned orbital rocket and spacecraft system operated by NASA on 135 missions from 1981 to 2011. The system combined rocket launch, orbital spacecraft, and re-entry spaceplane with modular add-ons...

 through 1978 and the TRS was almost complete, the agency gave up in December when it became clear that the shuttle would not be ready in time; its first flight, STS-1
STS-1
STS-1 was the first orbital flight of NASA's Space Shuttle program. Space Shuttle Columbia launched on 12 April 1981, and returned to Earth on 14 April, having orbited the Earth 37 times during the 54.5-hour mission. It was the first American manned space flight since the Apollo-Soyuz Test Project...

, did not occur until April 1981. Also rejected was a proposal to launch the TRS using one or two unmanned rockets.

Re-entry

Skylab's demise was an international media event, with merchandising, wagering on the time and place of re-entry, and nightly news reports. The San Francisco Examiner offered a $10,000 prize for the first piece of Skylab delivered to its offices; the competing Chronicle
San Francisco Chronicle
thumb|right|upright|The Chronicle Building following the [[1906 San Francisco earthquake|1906 earthquake]] and fireThe San Francisco Chronicle is a newspaper serving primarily the San Francisco Bay Area of the U.S. state of California, but distributed throughout Northern and Central California,...

offered $200,000 if a subscriber suffered personal or property damage. NASA calculated that the odds of station re-entry debris hitting a human were 1 to 152—although the odds of debris hitting a city of 100,000 or more were 1 to 7—and special teams were readied to head to any country hit by debris and requesting help.

Ground controllers adjusted Skylab's orientation for ideal re-entry dynamics in the hours before reentry at approximately 16:37 UTC 11 July 1979. They aimed the station at a spot 810 miles (1,303.6 km) south southeast of Cape Town, South Africa. The station did not burn up as fast as NASA expected, however. Due to a 4% calculation error, debris landed southeast of Perth, Western Australia
Perth, Western Australia
Perth is the capital and largest city of the Australian state of Western Australia and the fourth most populous city in Australia. The Perth metropolitan area has an estimated population of almost 1,700,000....

, and was found between Esperance
Esperance, Western Australia
Esperance is a large town in the Goldfields-Esperance region of Western Australia, located on the Southern Ocean coastline approximately east-southeast of the state capital, Perth. The shire of Esperance is home to 9,536 people as of the 2006 census, its major industries are tourism, agriculture,...

 and Rawlinna, from 31° to 34°S and 122° to 126°E. The Shire of Esperance
Shire of Esperance
The Shire of Esperance is a Local Government Area in the Goldfields-Esperance region of Western Australia, about south of the city of Kalgoorlie and about east-southeast of the state capital, Perth...

 fined the United States A$400 for littering, a fine which remained unpaid for 30 years. The fine was paid in April 2009, when radio show host Scott Barley of Highway Radio raised the funds from his morning show listeners and paid the fine on behalf of NASA.

Seventeen-year-old Stan Thornton found a few pieces of Skylab at his home in Esperance and caught a flight to San Francisco, where he collected the Examiner prize. In a coincidence for the organizers, the annual Miss Universe
Miss Universe
Miss Universe is an annual international beauty contest that is run by the Miss Universe Organization. The pageant is the most publicized beauty contest in the world with 600 million viewers....

 pageant was scheduled to be held a few days later, on 20 July 1979 in Perth. A large piece of Skylab debris was displayed on the stage.

After the demise of Skylab, NASA did not launch another space station until it began construction of the International Space Station
International Space Station
The International Space Station is a habitable, artificial satellite in low Earth orbit. The ISS follows the Salyut, Almaz, Cosmos, Skylab, and Mir space stations, as the 11th space station launched, not including the Genesis I and II prototypes...

 (ISS) in 1998, in partnership with Russia
Russia
Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...

, the European Space Agency
European Space Agency
The European Space Agency , established in 1975, is an intergovernmental organisation dedicated to the exploration of space, currently with 18 member states...

 (ESA), Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

 and Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

. A proposed all-American successor to Skylab, Space Station Freedom, was merged into the plans for the ISS in 1993.

Skylab 5

Skylab 5 would have been a short 20-day mission to conduct scientific experiments and boost Skylab into a higher orbit. Vance Brand (commander), Don Lind (command module pilot), and William B. Lenoir
William B. Lenoir
William Benjamin "Bill" Lenoir was an American engineer and a former NASA astronaut.Lenoir was born on March 14, 1939, in Miami, Florida. He was divorced and remarried, and was survived by three grown children. His recreational interests included sailing, wood-working and outdoor activities...

 (science pilot) would have been the crew for this mission, with Brand and Lind being the prime crew for the never-flown Skylab Rescue
Skylab Rescue
Brand flew in 1975 during the Apollo-Soyuz Test Project as command module pilot, later commanding three Space Shuttle missions . Lind would wait another decade before he flew as a mission specialist on STS-51-B in 1985.-External links:* * * * * * *...

 flights. Brand and Lind also trained for a mission that would have aimed Skylab for a controlled deorbit.

Skylab B

A flight-quality backup Skylab was built. NASA considered using it for a second station in May 1973 or later, to be called Skylab B (S-IVB 515), but decided against it. Launching another Skylab with another Saturn V rocket would have been very costly, and it was decided to spend this money on the development of the Space Shuttle instead. The backup is on display at the National Air and Space Museum
National Air and Space Museum
The National Air and Space Museum of the Smithsonian Institution holds the largest collection of historic aircraft and spacecraft in the world. It was established in 1976. Located in Washington, D.C., United States, it is a center for research into the history and science of aviation and...

 in Washington, D.C.
Washington, D.C.
Washington, D.C., formally the District of Columbia and commonly referred to as Washington, "the District", or simply D.C., is the capital of the United States. On July 16, 1790, the United States Congress approved the creation of a permanent national capital as permitted by the U.S. Constitution....


Engineering mock-ups

A full-size training mock-up once used for astronaut training is located at the Lyndon B. Johnson Space Center
Lyndon B. Johnson Space Center
The Lyndon B. Johnson Space Center is the National Aeronautics and Space Administration's center for human spaceflight training, research and flight control. The center consists of a complex of 100 buildings constructed on 1,620 acres in Houston, Texas, USA...

 visitor's center in Houston, Texas
Houston, Texas
Houston is the fourth-largest city in the United States, and the largest city in the state of Texas. According to the 2010 U.S. Census, the city had a population of 2.1 million people within an area of . Houston is the seat of Harris County and the economic center of , which is the ...

. Another full-size training mock-up has been decaying in a museum parking lot exposed to the elements in Huntsville, Alabama
Huntsville, Alabama
Huntsville is a city located primarily in Madison County in the central part of the far northern region of the U.S. state of Alabama. Huntsville is the county seat of Madison County. The city extends west into neighboring Limestone County. Huntsville's population was 180,105 as of the 2010 Census....

, after it was moved outdoors to make way for an exhibit on the Soviet and later Russian Mir
Mir
Mir was a space station operated in low Earth orbit from 1986 to 2001, at first by the Soviet Union and then by Russia. Assembled in orbit from 1986 to 1996, Mir was the first modular space station and had a greater mass than that of any previous spacecraft, holding the record for the...

space station. This Skylab engineering mock-up was being considered for restoration and display at the U.S. Space & Rocket Center.

Mission designations

The numerical identification of the manned Skylab missions was the cause of some confusion. Originally, the unmanned launch of Skylab and the three manned missions to the station were numbered SL-1 through SL-4. During the preparations for the manned missions, some documentation was created with a different scheme -- SLM-1 through SLM-3 -- for those missions only. William Pogue credits Pete Conrad
Pete Conrad
Charles "Pete" Conrad, Jr. was an American naval officer, astronaut and engineer, and the third person to walk on the Moon during the Apollo 12 mission. He set an eight-day space endurance record along with command pilot Gordon Cooper on the Gemini 5 mission, and commanded the Gemini 11 mission...

 with asking the Skylab program director which scheme should be used for the mission patches, and the astronauts were told to use 1-2-3, not 2-3-4. By the time NASA administrators tried to reverse this decision, it was too late, as all the in-flight clothing had already been manufactured and shipped with the 1-2-3 mission patches.
Mission Emblem Commander Pilot Science Pilot Launch date Landing date Duration (days)
Skylab 1 SL-1 unmanned launch of space station 1973-05-14
17:30:00 UTC
1979-07-11
16:37:00 UTC
2248.96
Skylab 2 SL-2 (SLM-1)
Skylab 2
-Backup crew:-Support crew:*Robert L. Crippen*Richard H. Truly*Henry W. Hartsfield, Jr*William E. Thornton-Mission parameters:*Mass: 19,979 kg*Maximum Altitude: 440 km*Distance: 18,536,730.9 km...

Pete Conrad
Pete Conrad
Charles "Pete" Conrad, Jr. was an American naval officer, astronaut and engineer, and the third person to walk on the Moon during the Apollo 12 mission. He set an eight-day space endurance record along with command pilot Gordon Cooper on the Gemini 5 mission, and commanded the Gemini 11 mission...

Paul Weitz
Paul J. Weitz
Paul Joseph Weitz is an American former astronaut who flew in space twice.-Personal data:Born in Erie, Pennsylvania, on July 25, 1932. Married to the former Suzanne M. Berry of Harborcreek, Pennsylvania. Two children: Matthew and Cynthia. Hunting and fishing are among his hobbies. His mother, Mrs...

Joseph Kerwin 1973-05-25
13:00:00 UTC
1973-06-22
13:49:48 UTC
28.03
Skylab 3 SL-3 (SLM-2)
Skylab 3
Skylab 3 was the second manned mission to Skylab. The Skylab 3 mission started July 28, 1973, with the launch of three astronauts on the Saturn IB rocket, and lasted 59 days, 11 hours and 9 minutes...

Alan Bean
Alan Bean
Alan LaVern Bean is a former NASA astronaut, engineer, and painter. Bean was selected to become an astronaut by NASA in 1963 as part of Astronaut Group 3. He made his first flight into space aboard Apollo 12, the second manned mission to land on the Moon, at the age of thirty-seven years in...

Jack Lousma Owen Garriott 1973-07-28
11:10:50 UTC
1973-09-25
22:19:51 UTC
59.46
Skylab 4 SL-4 (SLM-3)
Skylab 4
Skylab 4 was the fourth Skylab mission and placed the third and final crew on board the space station. The mission started November 16, 1973 with the launch of three astronauts on a Saturn IB rocket, and lasted 84 days, 1 hour and 16 minutes...

Gerald Carr
Gerald P. Carr
Gerald Paul Carr is an engineer, retired United States Marine Corps colonel and former NASA astronaut. He was commander of Skylab 4, the third and final manned visit to the Skylab Orbital Workshop, from November 16, 1973 to February 8, 1974.-Biography:Carr was born in Denver, Colorado on August...

William Pogue
William R. Pogue
William Reid Pogue is a retired American astronaut who is also an accomplished teacher, public speaker, and author.-Biography:...

Edward Gibson
Edward Gibson
Edward George Gibson, PhD, is a former NASA astronaut, pilot, and engineer.Before becoming a NASA astronaut, Gibson graduated from the University of Rochester and the California Institute of Technology...

1973-11-16
14:01:23 UTC
1974-02-08
15:16:53 UTC
84.04

Gallery

See also

  • Skylab Medical Experiment Altitude Test (SMEAT)
    Skylab Medical Experiment Altitude Test
    The Skylab Medical Experiment Altitude Test, or SMEAT, was a 56-day simulation of an American Skylab space mission from July 26–September 19, 1972 at NASA's Manned Spacecraft Center in Houston, Texas...

  • Splashdown (spacecraft landing)
    Splashdown (spacecraft landing)
    Splashdown is the method of landing a spacecraft by parachute in a body of water. It was used by American manned spacecraft prior to the Space Shuttle program. It is also possible for the Russian Soyuz spacecraft and Chinese Shenzhou spacecraft to land in water, though this is only a contingency...

  • Mir
    Mir
    Mir was a space station operated in low Earth orbit from 1986 to 2001, at first by the Soviet Union and then by Russia. Assembled in orbit from 1986 to 1996, Mir was the first modular space station and had a greater mass than that of any previous spacecraft, holding the record for the...


Further reading


NASA


3rd Party

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