Skylab is the name for the first and only purely American space station as well as the name for the space missions in this context.
Even during the preparation of the Apollo program already thinking about the future of manned space flight were made at NASA. For this, the Saturn / Apollo Applications Office was established in August 1965. This had to search for the task on the usage options for the Apollo hardware. The purpose was to get the accumulated knowledge of the engineers who would otherwise have been released after the end of the Apollo program. Man attacked fairly early on proposals to rebuild a high school of a Saturn rocket to a space station and to use the Apollo spacecraft and Saturn 1B rockets that do not got to use for transporting personnel.
Even before NASA was looking for new astronauts. This time were not asked test pilots, but scientists. On June 28, 1965 Owen Garriott, Edward Gibson, Duane E. Graveline, Joseph Kerwin, Frank C. Michel and Harrison Schmitt were presented to the public as a science astronauts.
Unlike the Apollo program that clearly had the moon landing goal, the objectives of the Apollo Application Programs were rather vague. Many proposals have been drawn had the Saturn rockets and Apollo spacecraft as a basis. The only project, however, realized, was an Earth orbital space station with a crew of three. Originally the plan was to start them with a Saturn 1B and expand the S- IVB upper stage empty burned in several flights to a space station ( concept "wet workshop" ). It was found, however, that this approach was too costly. It waved in the summer of 1969 to the plan, assemble the space station on the ground and with a Saturn V, in which only the two lower levels contributed to the drive to start ( "dry workshop" ). For this purpose the missile SA -513 was used, which was previously provided for Apollo 18. The Apollo 20 mission was canceled in January 1970 from the moon program because no Saturn V stood longer available. As of February 1970, the name was officially used for the Skylab space station.
The McDonnell Douglas in 1970 presented two copies of the space station here. One was used for training, the other was the flight model. It was an attempt to bring the training model as Skylab B also into space, but this was rejected for financial reasons.
The construction of Skylab
The space laboratory Skylab consisted mainly of the second stage of the Saturn 1-B rocket AS- 212 ( identical to the third stage of a Saturn V), which has already been provided on the ground with supplies and equipment. For the start so only two stages of the Saturn V were used. This was the first and also the last launch of a Saturn V in this configuration, because so far this type of missile was used for the Apollo spacecraft. This part of the station was the Orbital Workshop ( OWS). He weighed 35.8 tonnes. The crew lived and worked in the hydrogen tank with a usable internal volume of 275 m³. The oxygen tank was equipped with a lock and used as a rubbish pit. In OWS, there was the equipment, all food supplies, the total water resources and pressure tanks for the fuel for attitude control. In addition to the living room, bedroom and sanitary premises, experiments were carried out there, especially Earth observation through a window and medical examinations. The OWS had two small locks for experiments on the sun and facing away from the station; former was occupied permanently for the repair of thermal protection. The habitable volume was repeatedly divided into dining and relaxation areas as well as individual sleeping cabins, especially with latticed flooring, in which the astronauts were able to hook it with special shoes. Due to the large diameter of a volume of 280 m³ was habitable. This volume was exceeded only by the Mir in its final stage.
The instrument ring of Saturn V joined to the OWS, which was maintained in order to avoid changes to the launch facilities. He steered the launcher and admitted after the start when Skylab had arrived in orbit, the control to the internal computer of Skylab from. After OWS was followed by the 22 -ton airlock, the Airlock Module ( AM). It contained an airlock to exit, unbolted the OWS on the docking adapter, included the control of telescopes and all gases for the station in pressurized tanks. Their width decreased from 6.7 to 3.04 m back. They had a length of 5.2 m and an internal volume of 17.4 m³.
It was followed by the cylindrical Multiple Docking Adapter ( MDA). He was 3.04 m wide, 5.2 m long and had a mass of 6260 kg. He had two docking sites for the Apollo command capsule: a radially and in the extension of the longitudinal axis. The radial docking site was meant for a Notkapsel that could have been started if a return with the first capsule would not have been possible but was functionally equivalent to the axial.
For safe solar viewing, which was an important goal of Skylab, the space station also had an observatory, the Apollo Telescope Mount (ATM ), which was extended sideways after reaching the orbit in a position to the MDA. It weighed 11,066 kg, was 6 m wide and 4.4 m high. His solar telescopes could be precisely aligned to 2.5 arc seconds. Was controlled by the OWG from which the films on an outboard maneuver (EVA) had to be changed. The power supply was planned with four solar panels on ATM and two more by the main module. Alone the solar panels of the ATM had a wingspan of 31 m. The ATM used components of the LM and concerned with its spin wheels the alignment of the entire station.
Recently there was the docked Apollo spacecraft as Command and Service Module (CSM ). The CSM took over all communication with the Earth, as Skylab, apart from its on-board telemetry, did not have its own transmitter. Furthermore, the life support systems of the CSM once a month had to take over the gas cleaning when the molecular sieves of Skylab were baked. The CSM was therefore an integral part of the station.
The mass was about 90 tons. Overall, Skylab was much larger than the Soviet space station Salyut 1, which was launched in April 1971. With a favorable position of the sun Skylab was observed with the naked eye as a luminous point even in the daytime.
The launch of Skylab 1
The launch of this first American space station should be from Launch Complex 39 -A at Cape Canaveral on 14 May 1973. The next day, the first crew should follow with a Saturn 1B rocket from the launch pad 39 -B. The three crews were wearing the mission designations Skylab 2, Skylab 3 and Skylab 4.
Saturn V which should be used for SkyLab 1, SA -513, was a little shorter than the models, which were used for the moon flights. She had no rescue rocket, no Apollo spaceship and an adapter for the Lunar Module. In addition, this rocket took only two steps. Instead of the third stage they transported the space station with a cone-shaped panel at the top. This flight was the last of a Saturn V.
It was the first time that the countdown was prepared by two Saturn rockets simultaneously. Like it but had already given in December 1965, when Gemini 7 and Gemini 6 were launched sequentially.
The orbit was chosen with an inclination of 50 ° so that large parts of the land areas of the earth were flown over.
Damage at the start
Skylab 1 lifted as planned on 14 May 1973. But even 63 seconds after the start of the ground station received alarming telemetry signals. Apparently, a panel had come loose, causing one of the solar modules and the meteorites and thermal shield were torn down. Later research showed that the error was caused by lack of coordination of the design departments (see Not - Invented -Here syndrome). Although the space station reached the planned orbit, but was not functional.
While it succeeded the flight line, extend the four solar modules solar observatory, but it seemed problems with the other two modules to give, so that a total of only stood about half the electrical power available. The lack of meteorite shield should also serve as thermal insulation, which is why the temperature rose sharply in the station had to be so afraid that that food, drugs and movies would be spoiled.
As a first reaction to the launch of Skylab 2 was delayed until they could get a clear picture of the situation. In addition, the flight management tried to achieve a favorable orientation of Skylab. Goods facing the functional cells of the sun, although sufficient energy could be obtained, at the same time the station but heated up rapidly. Turned to the station so that the body lay with the missing shield in the shade, gave the solar cell from a lack of power and the state of charge of the batteries fell sharply. The NASA engineers now had to keep the problem, energy reserves, fuel reserves and temperature of the space station in the frame. Would it not be possible within days to repair the damage, the station would be lost. For two weeks, the station was controlled during the Skylab - 2 mission has been prepared.
It succeeded the teams during the Skylab missions 2 and Skylab 3, to repair the damage. The station was then fully functional. More about the repair work ( eng.: On- Orbit Servicing ) in the relevant articles.
Three crews of three astronauts spent a total of 513 man-days in space. Since the launch of Skylab was counted as Mission 1, the manned missions starting with the number 2:
- Skylab 3: July 28, 1973 - September 25, 1973
- Crew: Alan L. Bean, Dr. Owen K. Garriott, Jack R. Lousma
- Skylab 4: November 16, 1973 - February 8, 1974
- Crew: Gerald P. Carr, Dr. Edward G. Gibson, William R. Pogue
The tasks of the crews initially included the repair of the damaged space station. Further evidence on the effects of long-term stay were obtained in zero gravity. Moreover, in addition to some animal studies with fish and spiders extensive sun and Earth observations and images of comet C/1973 E1 belonged ( Kohoutek ) to the program. It was found that the consumption of resources was much smaller than expected. The crew lived on the started with Skylab 1 supplies and food, water and gases. Originally, the second and third crew should stay during 56 consecutive days at the space station. However, the lower consumption made a stay of 59 and 84 days possible, with the last crew inventories added some additional movies and in particular brought.
It should be noted that Skylab did not have the (simple) possibility of refilling (or similar by fueling ) decreed what is essential on the subsequent understanding of a space station. A part of the resources, however, would be at least in part of a EVA was supplemented using the valves used on the earth.
The launch took place, as later the Apollo -Soyuz project, from a shorter essay by a launch pad.
During operation of Skylab a skeleton crew was kept in readiness, which would have the primary team can save ( Skylab rescue plan ). But there was a Apollo capsule with two more seats under the original and another Saturn IB available. It was intended that Vance Brand and Don Lind flew for two to Skylab and their comrades returned. This mission was never carried out, both astronauts were but later missions.
After three crews had inhabited the space station 28, 59 and 84 days, she was pushed on 8 February 1974, the Apollo spacecraft from Skylab 4 in a higher orbit. On board remained about one-third of the original water supply of 2720 liters (equivalent to approximately 180 man-days ), oxygen for about 420 man-days, and similar supplies of nearly all other consumables. According to the calculations of the NASA Skylab should remain functional after the reboost about nine more years. The re-entry into the Earth's atmosphere was estimated to be March 1983. It was planned at this time that about 1979 a space shuttle could dock with a drive module of Skylab to bring the space laboratory back into a higher orbit. This should be done with the canceled mission STS -2a. However, there were no concrete plans for further use of the station, which would have been problematic because of the old technology.
Most systems of the space station were shut down, and Skylab orbited the Earth for several years, without being noticed. In March 1978, the contact with Skylab was resumed. Apparently the station rotating largely uncontrolled, with a period of six minutes per revolution, and the radios worked only if the solar panels were in sunlight. After a week, it was possible to load multiple batteries remotely. The central computer was still working satisfactorily, the position control but was significantly affected by the failure of a star sensor and the partial failure of one of the three reaction wheels.
However, it turned out that Skylab fell faster than calculated. This was due to the unexpectedly extended due to high solar activity, the upper atmosphere of the earth and the resulting increase in deceleration. Furthermore, we knew at that point that the space shuttle would not be ready in time. An alternative mission, for example, with a titanium III as a carrier, was discarded. On 19 December 1978, NASA announced that Skylab could not save that one but everything would undertake to minimize the risk of crash damage. To this end, NASA worked closely with the Authority's North American Aerospace Defense Command ( NORAD ). NASA and NORAD used, different calculation methods for re-entry and therefore came up with different results for the time and place of decline. Officially, however, the NORAD results were always announced.
NASA planned to be able to control the orientation of the space station, the atmospheric friction to slow down or speed up the crash. By remote control SkyLab should then be added to some point in rotation with known aerodynamics. The danger zone could be moved within narrow limits.
The crash was then carried out on 11 July 1979. The last orbit of Skylab led mostly over water surfaces, and NASA was the last control command to transfer the danger zone of North America away to the Atlantic and the Indian Ocean. In fact, the station broke later than calculated in several parts, so that the crash area was further east than planned. Affected the area south-east of Perth in Western Australia was hurting at Balladonia where debris rained down in the dark hours of the morning without someone. Various parts were salvaged, brought to the U.S. and there identified after NASA had awarded a reward for the first Fund. The authorities of the Australian community Esperance Shire NASA sent a penalty notice over 400 dollars for the illegal disposal of waste. NASA refused to pay; until 2009, the outstanding amount from a U.S. radio station was settled.
The total mission cost about 2.6 billion U.S. dollars.