Space The Skylab

A view of the Skylab. picture courtesy NASA

As NASA had shut down assembly lines to the Saturn V rocket by August 1968, any remanining rockets could be used for further lunar exploration or to launch a U.S. Earth-orbiting space station as part of the Apollo Applications Program (AAP). A year later, NASA opted for one of both version of it, with the station launched with already outfitted living and working quarters. In February 1970, NASA eventually redesignated the AAP into the Skylab. After the Apollo program had ended in 1972 with the last, Apollo 17 mission, NASA just used the program's last parts and vehicles into a new program, the 'Skylab'. The 'Apollo Applications Program' had like a objective to develop science-based human space missions using hardware originally developed for the effort to land astronauts on the Moon. NASA's Marshall center provided the Saturn launch vehicles for the four Skylab missions and directed many of the station's experiments. Skylab also grew out of a program that first was thought about in the mid-1950's by one of the German engineers, Krafft Ehricke, who worked for the U.S. Air Force on the Atlas ICBM missile. And as one of the ideas of what else could we do with the Atlas, Krafft Ericke thought about if we could launch these missiles into orbit around the Earth, we could evacuate them, fill them with air, and then people could live onboard. That was not followed too seriously. Launched on May 14, 1973, Skylab orbited Earth from 1973 to 1979. That 169,950-pound space station of sort included a workshop, solar observatory, docking adapter and systems to allow three crews to spend up to 84 days in space. The missions there were officially part of the Apollo program. The Skylab was the U.S.A.'s first space station, with a weight 100 tons, and an orbital science and engineering laboratory. That endeavour might have been too a U.S. response to that the Soviet USSR, at the time, was boldly engaging into its lasting program of manned orbital station, since 1971. The Skylab was larger and more complex that the first Soviet experimental space station Salyut which had launched by 1971. The Skylab worked one year only however, with three crews succeding themselves at the station between May 14, 1973 and February 8th, 1974, as they carried out 270 scientific and technical investigations and logged a combined 171 days on orbit. The Skylab consisted of a modified Saturn V stage, which had been turned into an habitable and working space. Equiped with solar arrays for power production, the Skylab was orbiting at a speed of 16,000 mph (9,900 km/h), as the crew were catching the station aboard Apollo Command and Service Modules. The missions at the Skylab unfolded under the supervisation of the Mission Control, at Houston. A Apollo command module remained docked to Skylab like a lifeboat for about three months from 1973 to 1974. Once in orbit, it took the crew 8 hours to rendezvous with the Skylab

The Skylab complex consisted of four major components: the Orbital Workshop (OWS), the Airlock Module (AM), the Multiple Docking Adapter (MDA), and the Apollo Telescope Mount (ATM). The Apollo Command and Service Module transported crews to and from Skylab and remained attached to the station throughout a crew’s occupancy. check a diagram of the Skylab. The OWS, converted from the upper stage of a Saturn rocket, served as the main working, living and sleeping compartment for the crews, and contained exercise equipment, a galley, and many of the scientific experiments, in particular for the life sciences studies. Two large solar arrays on the OWS provided 12.4 kW of power to the station. The AM enabled astronauts to conduct spacewalks, while the MDA included a prime and backup docking port for the Apollo spacecraft and housed the Earth Resources Experiment Package. The ATM contained telescopes for solar observations and four solar arrays for additional power. Once in orbit, the complex weighed 170,000 pounds, by far the heaviest spacecraft to date. For the first time in human spaceflight, Skylab’s second docking port enabled a rescue capability. A second Apollo capsule carrying two astronauts could come to the aid of the resident three-person crew should their spacecraft become disabled, with all five returning to Earth in the new spacecraft

Among the experiments conducted aboard the Skylab, the station served as the greatest solar observatory of its time. The crewmembers also performed experiments in microgravity, medicine, and Earth observation. The Skylab also was instrumental into creating new technologies necessitated by a prolonged, manned stay in space (like special showers, exercise equipement, or kitchen facilities, for example, all working in microgravity) and into beginning to catch what the effects of long stays in space on crews were. The ongoing activity of astronauts just going about their daily lives in orbit was one of the greatest of all the scientific experiments aboard the station. Spacewalks had been scheduled in the sole purpose to change out the film in an instrument, the 'Apollo Telescope Mount', but the first two crews had to perform some more, to repair the two solar panels of the station, which had been damaged by a meteoroid shield which came to hit those during launch, or to fix thrusters' leak which came to occur. Due to vibrations during liftoff of unmanned modules, a critical meteoroid shield had ripped off, taking one of the craft's two primary solar panels with it. Engineers in mission control maneuvered Skylab's secondary solar panels to face the Sun to provide as much electricity as possible. Because of the loss of the meteoroid shield, however, this positioning caused workshop temperatures to rise to 126° F. Meanwhile, in an intensive 10-day period, NASA engineers developed procedures and trained the crew to make the workshop habitable. At the same time, engineers rolled Skylab to lower the temperature of the workshop. Engineers and astronauts at the JSC and Marshall Space Flight Center selected one option that met the criteria of being ready in time for the first crew’s launch, small enough to fit in the Command Module, and not require space walking, which was a parasol constructed of aluminum poles and fabric made of nylon, Mylar and aluminum and deployed from the inside of the station. The parasol was designed, manufactured and tested in just a few days and stowed aboard the Skylab Command Module the night before launch. The first crew, after launch and six hours into their flight approached Skylab as they performed a fly-around to observe damage, trying then to cut away the solar array debris through a 40-minute Stand-up Extravehicular Activity (SEVA) where astronaut Weitz standing out of the Apollo spacecraft and Kerwin holding him by the legs. Then, aboard the station, by deploying the parasol-type sunshield from the inside through Skylab's solar scientific airlock. The lack of power from the missing and jammed solar arrays however curtailed further activities. In the Neutral Buoyancy Simulator at Marshall Space Flight Center, Skylab 2 backup commander Russell Schweickart and Skylab 4 crewmember Edward Gibson practiced techniques that could be used during a spacewalk and relayed that information to the onboard crew. On June 7, 1973, on their 14th day in space, Conrad and Kerwin floated out of Skylab’s Airlock Module. They set up a 25-foot pole with cable cutter tool at the end that closed partway over the aluminum strap from the micrometeoroid shield that was holding down the solar array. Conrad used the pole as a handhold to translate down the solar wing and attached a rope to its structure. Kerwin closed the jaws on the cutter tool the rest of the way, slicing through the metal strap. The solar wing partially opened, but its hinge had frozen in the cold of space preventing it from fully opening. Conrad and Kerwin then both pulled on the rope to overcome the frozen hinge and the wing sprung fully open, bouncing the astronauts away – luckily their space suit tethers kept them from floating off into space. Once the wing opened, the individual solar panels deployed and shortly Mission Control notified the crew that they were generating power! Conrad and Kerwin climbed back inside Skylab after 3 hours and 25 minutes, the longest spacewalk in Earth orbit to date. During another spacewalk, the second crew deployed another sunshield. After that, Conrad, Weitz and Kerwin focused on completing as much science as possible, research being the primary goal of Skylab. Based on health data gathered about astronauts during the mission, flight doctors increased the caloric intake and amount of exercise for the next Skylab crew. Before leaving the crew prepared Skylab for an unmanned period until the second crew arrived in July. After separation, the Command Module (CM) splashed down about 800 miles southwest of San Diego and 6.5 miles from the prime recovery ship, the aircraft carrier USS Ticonderoga. A unexpected side trip occurred two days after the crew return to Earth, and flown from the carrier by a helicopter, as U.S. President Richard M. Nixon invited the crew to the Western White House in San Clemente, California, where he was holding a summit with Soviet General Secretary Leonid Brezhnev. On the other hand, the crew broke with medical protocols by removing the surgical masks they wore to prevent any infections. Each Skylab crew consisted into a commander, a pilot and a scientist

The Skylab Crews

Date of Launch	Crewmembers	Duration	Remarks
May 14th, 1973	Pete Conrad (commander), Paul Weitz (pilot), Joe Kerwinh (science pilot)	28 d	prior to the launch, 11 days before, the launch of the Skylab proper had occurred, powered by a Saturn V rocket as that was the last flight of a Saturn V launcher (the Saturn 1B rocket that was originally designated to launch the LM-2 during the Apollo program, came out of storage to launch that first Skylab crew). Launch of the first crew to inhabit the station was delayed 10 days, launching actually May 25th, while NASA developed a plan to save the damaged Skylab. On June 18, the Skylab 2 crew broke the 24-day endurance record set by the Soviet Soyuz 11 crew in 1971
July 28th, 1973	Alan Bean, Jack Lousma, Owen Garriott	59 d	the crew launched atop a Saturn IB rocket. the crew deployed a twin pole solar shield to replace the original protecting panel two months after it was ripped off during the May 1973 launch
na	Gerald P. Carr (commander), William R. Pogue (pilot), Edward G. Gibson (science pilot)	84 d	the return of the third crew, on Feb. 8, 1974 marked the end of the Skylab program as the duration of the stay constituted a world record at the time

Crewmembers inside the Skylab. picture courtesy Marshall Space Flight Center, Kennedy Space Center

Originally planned for August 17, 1973, NASA accelerated the launch date of the second crew by 3 weeks due to concerns with the ability of Skylab's replacement parasol to continue to cool the station and problems with its attitude-sensing gyroscopes. This second crew would deploy a more permanent sun shade, and NASA stowed replacement gyroscopes into the Command Module in case they were needed. The major goals of the mission were for the crew to conduct a variety of scientific experiments during their 59 days in space, more than doubling the previous crew's orbital duration. To better counteract the effects of the long-duration mission, the second crew planned to spend more time exercising while onboard, based on the experiences of the first crew. Shortly after reaching orbit, one of the four clusters or quads of thrusters began to leak. The thrusters are located at 90-degree intervals around the Service Module (SM) and used for attitude control and rendezvous maneuvers. The only solution was to shut off that quad, forcing the crew to complete the rendezvous, inspection fly-around and docking using only the three working quads, a scenario they never practiced before the mission. With the help of a handheld calculator to make calculations on how fast they were approaching the station, the crew successfully completed the difficult maneuvers and docked. Shortly after their move into the space station, all three crewmembers experienced symptoms of space motion sickness, causing them to fall behind their timelines. Managers delayed the first extravehicular activity (EVA) or spacewalk planned by several days to allow them to recover. In the meantime, a second set of thrusters on the SM began to leak and the crew quickly shut that quad down. Ground controllers began to be concerned that with only half its thrusters operating, the SM may not be able to safely return the crew to Earth. NASA managers decided to put in place a unique feature of Skylab: a rescue capability. Workers at KSC accelerated work to assemble and transfer to the pad the next Saturn IB rocket and Apollo spacecraft to be able to launch it. In this rescue scenario, two astronauts would fly to Skylab and dock at its lateral docking port and bring the resident crew home in a Command Module modified to return all five crewmembers. In the end, managers decided that the Skylab 3 crew could use workaround procedures that the two rescue astronauts deviced in ground simulators to return home safely with only half the thrusters working, and called off the rescue attempt. With the crew feeling better and the crisis over the leaking thrusters averted, the three Skylab astronauts began working on their science program and preparing for the first spacewalk of the mission. They activated the Earth Resources Experiment Package (EREP), a suite of sensors that observed the Earth in the visible, infrared and microwave spectra, and completed several scans of various sites. As a technology demonstration, the crew practiced flying the Astronaut Maneuvering Unit (AMU) inside the spacious dome of the Skylab's Orbital Workshop as it was a test demonstration of the Manned Maneuvering Unit, a jetpack-like device allowing an astronaut to freely operate outside a spacecraft and used later in the Shuttle program during satellite servicing missions. One of the -- student -- experiments that garnered much attention was the study of how two spiders spun their webs in space and they seemed to adapt quite well. A two-astronauts spacewalk installed a more permanent sunshade over the space station. Engineers at the Marshall Space Flight Center developed this twin-pole sunshade shortly after Skylab was damaged during its launch as the first Skylab crew brought it to space aboard their Command. Its intallation had been delayed to the second Skylab crew as it required a complex spacewalk to install, and that crew had time to train in the Neutral Buoyancy Simulator (NBS) at the Marshall center. The twin-pole sunshade was deployed over the first emergency parasol during the 6-hour 31-minute spacewalk, the longest Earth-orbital spacewalk up to that date. The second EVA of the mission occurred on August 24 performing technical tasks and, on the next day, the crew surpassed the first Skylab crew's 28-day record for the longest human space flight. On August 27, the crew sent a message to the ground as part of the formal dedication ceremony for that the formerly Manned Spacecraft Center was renamed Lyndon B. Johnson Space Center

The third and final mission to the Skylab space station got underway with a launch on November 16, 1973 as the crew was a first all-rookie one since Gemini 8 in 1966. The spacecraft docked with the Skylab eight hours after, for a three-month stay. They kept making science, and also focused upon observing Comet Kohoutek, discovered earlier in the year. Two astronauts performed a spacewalk to replace film canisters and deploy a experiment package. A treadmill deviced by NASA and that the third crew had brought with them to the station, allowed for more exercise to maintain leg and back muscle mass and strength. The Skylab 4 crew on its 33rd day aboard the Skylab space station, when on Dec. 18, 1973, the Soviet Union launched Soyuz 13, with two cosmonautes aboard, on a eight-day science mission. This marked the first time in history that American astronauts and Soviet cosmonauts were in space at the same time. Since the two spacecraft were in different orbits, the crews could neither see nor communicate with one another. But the event highlighted the preparations then underway for the Apollo Soyuz Test Project (ASTP), the first cooperative human space mission between the United States and the Soviet Union, planned for July 1975. The ASTP was a project that arose in May 1972 in an agreement signed by President Richard M. Nixon and Soviet Premier Aleksey N. Kosygin. ASTP development was well underway by December 1973, with meetings between American and Soviet managers, engineers, and crewmembers taking place at regular intervals in both countries. The three Skylab astronauts and two Soyuz cosmonauts also marked the largest number of people in space at the same time, a record that stood for nine years. Skylab observations of comet Kohoutek were coordinated with ground-based and space-based measurements, including by the Mariner 10 spacecraft then on its way to Venus. On Christmas Day, the observations were performed during a spacewalk, during seven hours and one minute, the longest Earth orbital spacewalk to that time. Four days later, a further 3-hour 39-minute spacewalk provided for additional cometary observations. The third crew space flight duration record of 84 days stood for four years. Before return, they had to mothball the station. Mission Control teleprinted instructions to the crew, which required 15 feet of paper to print! After undocking, they performed an inspection fly-around of the Skylab space station and where they were the first crew to spend Thanksgiving, Christmas, and New Year holidays in space. Because of the additional exercise and better nutrition, the third crew returned in better physical condition than the other two crews who had spent less time in space. Thence the Skylab had been configured for unpiloted operations, with Mission Control maintaining control of the vehicle and the Service Module's Reaction Control System thrusters had been fired to raise the orbit's altitude, and it was predicted that the station would stay in orbit until the early 1980's. Following the final crewed phase of the Skylab mission, ground controllers performed engineering tests of certain Skylab systems -tests that ground personnel were reluctant to do while the crews were aboard. Results from these tests helped to determine causes of failures during the mission and to obtain data on long-term degradation of space systems. There were discussions of possibly revisiting Skylab once the space shuttle was flying regularly, or at least to have shuttle crewmembers remotely attach a rocket engine to the station to either boost it into a higher orbit or command it to a controlled reentry. Unfortunately, greater than predicted solar activity increased atmospheric drag and caused Skylab to lose altitude more rapidly than expected. Delays in the shuttle program finally made any rescue of the station impossible. On July 11, 1979, during its 34,981st orbit around the Earth, engineers in Mission Control at the Johnson Space Center in Houston sent the final command to Skylab to turn off its control moment gyros, sending it into a slow tumble. This was the best that flight controllers could do to ensure that Skylab would not reenter over a populated area such as North America. Skylab reentered the Earth's atmosphere thus by July 11, 1979, the station breaking up into hundreds of pieces, several large enough to survive to the ground, and the debris field eventually extended from the eastern Indian Ocean into Australia, fortunately over sparsely populated areas

A view of both the Saturn IB rocket and the Command and Service Module which carried astronauts to the Skylab. picture courtesy NASA

Skylab also was instrumental in providing U.S. high school students an opportunity to participate in a major national space project as administered by the National Science Teachers Association, with students to submit proposals for experiments that could be performed aboard the station and 25 students were able to participate in 19 experiments. The Skylab program is generally regarded like the program which allowed for further long-duration stays of crews in space, like with the Space Shuttle mission or the joint Russian-U.S. missions. Such long stays in space are currently further improving in their methods and techniques, since 1998, with the building of the International Space Station (ISS). Two crewmembers of the Skylab, Carr and Pogue, were involved into the development, during 13 years, of what became the ISS. More than 170,000 images had been provided by the Skylab to astronomers, while Earth scientists received 46,000