Editing Skylab (section)

== Operational history ==
=== Completion and launch ===
[[File:SKYLAB I - view from a distance.jpg|thumb|upright=1.2|Launch of the modified [[Saturn V]] rocket carrying the Skylab space station]]

On August 8, 1969, the [[McDonnell Douglas|McDonnell Douglas 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.<ref>{{harvp|Benson|Compton|1983|p=115}}.</ref> 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]] [[System 4 Pi|System/4Pi]] TC-1, a relative of the [[IBM System/4 Pi|AP-101]] Space Shuttle computers. The Saturn V with serial number SA-513, originally produced for the Apollo program – before the cancellation of Apollo 18, 19, and 20 – was repurposed and redesigned to launch Skylab.<ref>{{cite web |last=Tate |first=Kara |title=Skylab: How NASA's First Space Station Worked |website=[[Space.com]] |date=May 12, 2013 |type=Infographic |url=http://www.space.com/21055-skylab-space-station-nasa-infographic.html |access-date=April 24, 2014}}</ref> The Saturn V's third stage was removed and replaced with Skylab, but with the controlling [[Saturn V Instrument Unit|instrument unit]] remaining in its standard position.

Skylab was launched on May 14, 1973, by the modified Saturn V. The launch is sometimes referred to as Skylab 1. Severe damage was sustained during launch and deployment, including the loss of the station's [[micrometeoroid]] shield/sun shade and one of its main [[Solar panels on spacecraft|solar panel]]s. Debris from the lost micrometeoroid shield became tangled in the remaining solar panel, preventing its full deployment and thus leaving the station with a huge power deficit.<ref>{{harvp|Benson|Compton|1983|pp=253–255}}.</ref>

Immediately following Skylab's launch, [[Kennedy Space Center Launch Complex 39|Pad 39A]] at [[Kennedy Space Center]] was deactivated, and construction proceeded to modify it for the Space Shuttle program, originally targeting [[Cancelled Space Shuttle missions#STS-1A|a maiden launch in March 1979]]. The crewed missions to Skylab would occur using a Saturn IB rocket from Launch Pad 39B.

Skylab 1 was the last uncrewed launch from LC-39A until February 19, 2017, when [[SpaceX CRS-10]] was launched from there. 

=== Crewed missions ===
[[File:S73-32568skylab3saturnibnight.jpg|thumb|right|upright|Skylab 3's Saturn IB at night, July 1973]]
[[File:Skylab 3 flyaround.jpg|thumb|left|Skylab in orbit in 1973 as flown, docking ports in view]]

Three crewed missions, [[#Mission designations|designated]] [[Skylab 2]], [[Skylab 3]], and [[Skylab 4]], were made to Skylab in [[Apollo command and service module]]s. The first crewed mission, Skylab 2, was launched on May 25, 1973, by a Saturn IB and involved extensive repairs to the station. The crew deployed a parasol-like sunshade through a small instrument port from the inside of the station, bringing station temperatures down to acceptable levels and preventing overheating that would have melted the plastic insulation inside the station and released poisonous gases. This solution was designed by [[Jack Kinzler]], who won the [[NASA Distinguished Service Medal]] for his efforts. The crew conducted further repairs via two [[spacewalk]]s ([[extravehicular activity]] or EVA). The crew stayed in orbit with Skylab for 28 days. Two additional missions followed, with the launch dates of July 28, 1973, (Skylab 3) and November 16, 1973, (Skylab 4), and mission durations of 59 and 84 days, respectively. The last Skylab crew returned to Earth on February 8, 1974.<ref>{{cite web |url = https://space.skyrocket.de/doc_sdat/apollo-csm.htm |title = Apollo 201, 202, 4 – 17 / Skylab 2, 3, 4 / ASTP (CSM)}}</ref>

In addition to the three crewed missions, there was a rescue mission on standby that had a crew of two, but could take five back down.
* Skylab 2: launched May 25, 1973<ref>{{Cite web |title=SL-2 (Skylab 1) |url=http://heroicrelics.org/naval-aviation/apollo-sl-2/index.html |access-date=2023-02-19 | publisher= Naval Aviation Museum |website=heroicrelics.org}} {{pd-notice}}</ref>
* Skylab 3: launched July 28, 1973
* Skylab 4: launched November 16, 1973
* Skylab 5: cancelled
* Skylab Rescue on standby

Also of note was the three-man crew of [[Skylab Medical Experiment Altitude Test]] (SMEAT), who spent 56 days in 1972 at low-pressure on Earth to evaluate medical experiment equipment.<ref name="part3b">{{cite web |url=https://history.nasa.gov/SP-4011/part3b.htm|title=part3b|website=history.nasa.gov|access-date=19 January 2017}} {{PD-notice}}</ref> This was a spaceflight analog test in full gravity, but Skylab hardware was tested and medical knowledge was gained.

=== Orbital operations ===
[[File:Astronaut Owen Garriott Performs EVA During Skylab 3 - GPN-2002-000065.jpg|thumb|left|[[Owen Garriott]] performing an EVA in 1973]]
{{Bar graph
| title       = Days in space
| float       = right
| bar_width   = 10
| width_units = em
| data_max    = 100
| label_type  = Mission
| data_type   = #
| label1      = [[Skylab 2]]
| data1       = 28
| label2      = [[Skylab 3]]
| data2       = 60
| label3      = [[Skylab 4]]
| data3       = 84
}}

Originally intended to be visited by one 28–day and two 56–day missions for a total of 140 days,<ref name="frielingv5no4">{{cite journal |last=Frieling |first=Thomas |title=Skylab B:Unflowm Missions, Lost Opportunities |url=http://forum.nasaspaceflight.com/index.php?action=dlattach;topic=13040.0;attach=106506 |journal=QUEST |volume=5 |issue=4 |pages=12–21 |quote=Three crews, launched atop Saturn 1Bs, would visit the space station for visits of 28 days for the first crew and 56 days each for the final two crews.}}</ref> Skylab was ultimately occupied for 171 days and 13 hours during its three crewed expeditions, orbiting the Earth 2,476 times. Each of these extended the human record of 23 days for amount of time spent in space set by the Soviet [[Soyuz 11]] crew aboard the space station [[Salyut 1]] on June 30, 1971. Skylab&nbsp;2 lasted 28 days, Skylab&nbsp;3{{snd}} 56&nbsp;days, and Skylab&nbsp;4{{snd}} 84&nbsp;days. 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 Earth.<ref>{{harvp|Benson|Compton|1983|p=340}}.</ref> Solar experiments included photographs of eight [[solar flare]]s and produced valuable results<ref>{{harvp|Belew|1977|p=155}}.</ref> that scientists stated would have been impossible to obtain with uncrewed spacecraft.<ref>{{harvp|Benson|Compton|1983|pp=342–344}}.</ref> The existence of the Sun's [[coronal hole]]s was confirmed because of these efforts.<ref>{{harvp|Benson|Compton|1983|p=357}}.</ref> Many of the experiments conducted investigated the astronauts' adaptation to extended periods of [[Micro-g environment|microgravity]].

A typical day began at 6 a.m. [[Central Time Zone]].<ref>{{harvp|Benson|Compton|1983|pp=307–308}}.</ref> Although the toilet was small and noisy, both veteran astronauts{{snd}} who had endured earlier missions' rudimentary waste-collection systems{{snd}} and rookies complimented it.<ref>{{harvp|Benson|Compton|1983|pp=165, 307}}.</ref><ref name="harvp|Belew|1977|p=80|ps"/><ref name="time19730625"/> The first crew enjoyed taking a shower once a week, but found drying themselves in weightlessness<ref name="time19730625">{{cite news |url=http://www.time.com/time/printout/0,8816,907462,00.html |archive-url=https://archive.today/20130104224215/http://www.time.com/time/printout/0,8816,907462,00.html |url-status=dead|archive-date=January 4, 2013 |title=Living It Up in Space |publisher=Time |date=June 25, 1973 |page=61}}</ref> 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 abdominal muscles.<ref>{{harvp|Benson|Compton|1983|pp=306–308}}.</ref>

Breakfast began at 7 a.m. Astronauts usually stood to eat, as sitting in microgravity also strained their abdominal muscles. They reported that their food{{snd}} although greatly improved from Apollo{{snd}} 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]]. After breakfast and preparation for lunch, experiments, tests and repairs of spacecraft systems and, if possible, 90 minutes of physical exercise followed; the station had a bicycle and other equipment, and astronauts could jog around the water tank. After dinner, which was scheduled for 6&nbsp;p.m., 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]], the crews were often busy enough to postpone sleep.<ref>{{harvp|Benson|Compton|1983|pp=309, 334}}.</ref><ref>{{harvp|Martin Marietta|Bendix|1978|pp=2–7}}.</ref> The station offered what a later study called "a highly satisfactory living and working environment for crews", with enough room for personal privacy.<ref>{{harvp|Martin Marietta|Bendix|1978|pp=2–4}}.</ref> Although it had a [[Darts|dart set]],<ref name="darts">{{cite web |url=http://www.nasm.si.edu/collections/artifact.cfm?id=A19731653000 |title=Darts Game, Skylab |publisher=Smithsonian National Air and Space Museum |access-date=May 25, 2010 |archive-date=April 9, 2010 |archive-url=https://web.archive.org/web/20100409004413/http://nasm.si.edu/collections/artifact.cfm?id=A19731653000 |url-status=dead}} {{PD-notice}}</ref> [[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.<ref>{{harvp|Belew|1977|pp=79–80, 134–135}}.</ref>