Skylab: America’s First Space Station
In the 1960’s NASA investigated ways to gain further spaceflight experience after the Apollo Lunar missions. Some plans involved launching a space station, or orbital workshop as it became known, on two-stage, Saturn IB rockets.
The hydrogen tank of the Saturn S-IVB stage offered ample room for setting up an orbital workshop. Early plans involved what would be known as the “wet” workshop. Launched full of liquid oxygen and liquid hydrogen, the S-IVB would function normally as the rockets second stage during ascent. Most of the fuel would be consumed as the J-2 engine propelled the stage into orbit. Once safely in orbit, remaining fuel and oxidizer could be vented into space, allowing the hydrogen tank to later be pressurized with a breathable atmosphere and occupied by astronauts. Special fittings would be attached to the walls allowing equipment and experiments to be mounted when astronauts arrived. Floors and walls, formed by an aluminum grid structure, with ample openings so as not to interfere with fuel flow, could be pre-installed in the tank.
On top of the S-IVB stage would be a Multiple Docking Adaptor, or MDA. The MDA would have up to five docking ports for Apollo spacecraft or expansion modules. The MDA would contain many pieces of equipment that would be installed within the vented hydrogen tank when astronauts arrived.
Concerns existed about the length of time needed for astronauts, working in zero-g, to unpack large amounts of equipment launched in the MDA, transfer it into the workshop, and install it.
In 1969, it became apparent that several Saturn 5 rockets, already purchased, would remain unused after the Apollo Lunar missions. A decision was made to switch the Skylab launch from the smaller Saturn IB rocket to the much more capable Saturn 5 rocket. The greater capacity of the larger rocket meant that the S-IVB stage would not need to function as a rocket stage during launch. The “dry” workshop, as it became known, would be fully equipped on the ground. There was even enough capacity to launch the Apollo Telescope Mount on the same rocket. Earlier plans had the telescope mount launching separately and docking with the workshop.
Disaster on Launch Day
The Skylab space station was launched on 14 May 1973. Shortly after liftoff, a large micrometeoroid shield, designed to protect the orbital workshop, started to structurally fail. Within seconds, aerodynamic forces stripped the shield completely free from the station. As the shield tore off, one of two main solar array wings, designed to deploy only in the vacuum of space, partially deployed. Several minutes later, after the second stage finished its burn, retro rockets fired to separate the booster from the station. Exhaust from these retro rockets impacted the partially deployed solar array and ripped it from the station.
Once in orbit, more problems soon became apparent. Not only had the micrometeoroid shield and one solar wing been completely torn off, but the opposite array, while still attached to the station, had been tangled in debris and failed to deploy.
The situation continued to worsen. The missing micrometeoroid shield exposed the station to higher levels of solar heating then it was designed for. Temperatures in the station rose to 126 deg F (52 deg C).
Rescue and Repair
Fortunately, the four solar arrays on the Apollo Telescope Mount (ATM) deployed as planned. This power allowed controllers to operate the station, at least at a minimum level, until repairs could be made.
The first Skylab crew, scheduled to lift off the day following Skylab’s launch, was delayed while tools and techniques were quickly developed to repair the crippled station.
On 25 May 1973, the first Skylab crew, led by veteran astronaut Charles Conrad, lifted off from Kennedy Space Center. They carried with them several solar shades, designed to shade the orbital workshop, and a variety of cutters and other tools designed to free the jammed solar array.
With an internal temperature well over 100 degrees Fahrenheit, astronauts could initially spend only short periods of time in the station. On their second day in orbit, the crew was able to deploy a solar shade, known as the ‘parasol’. The parasol was deployed through an airlock in the side of the orbital workshop. The 22ft by 24ft parasol, composed of woven nylon, mylar, and aluminum, reflected enough solar energy to lower the internal temperatures to tolerable levels.
The first attempt to free the jammed solar array failed. A second attempt, on June 7, successfully released the solar panel. The station now had twice as much power available.
Despite the added workload required to repair the station, the crew was able to complete nearly all planned scientific objectives.
Skylab was ultimately visited by three crews. Each crew, consisting of a commander, a pilot, and a science pilot, was transported to the station using Apollo spacecraft, launched on Saturn IB rockets. Each successive crew stayed longer then the previous mission. Durations of 28 days, 59 days, and 84 days were achieved.
On 11 July 1979, Skylab re-entered Earth’s atmosphere. Debris from the station fell over the Indian ocean and parts of Australia.
Despite nearly catastrophic problems early on, Skylab proved highly successful and completed all of its major objectives. Proving that humans could do productive work for prolonged periods of time while in orbit.
Mir Space Station
The Mir base module was launched on 20 February 1986. Large expansion modules, launched on Proton rockets, were periodically added to the station. These modules used automated docking techniques developed during the missions of Salyut 6 and 7.
Crews were launched using Soyuz rockets and capsules. Progress spacecraft, also launched on Soyuz rockets, carried food, fuel, water, and other supplies to the station.
Starting in July 1995, several American space shuttles docked with the Mir station. Seven American astronauts lived onboard the station for extended periods of time. Shannon Lucid’s six month tour was the longest American stay on the station.
Cosmonauts performed many long duration stays aboard the station. Several spent over one year on the station. Dr. Valeri Polyakov lived aboard the station for a record 438 consecutive days.
With the International Space Station under construction in the late 1990’s, Mir was abandoned. Using progress tugs, Russian controllers were able to re-enter the station over a remote area of the Pacific ocean.
Operated in orbit for over a decade, the Mir space station proved human outposts could be maintained for extended periods of time.
International Space Station
In partnership with the United States, Russia, Japan and Canada, Europe is sharing in the greatest international project of all time – the International Space Station. The 360-tonne International Space Station has more than 820 cubic metres of pressurised space – enough room for its crew of six persons and a vast array of scientific experiments.
Station construction began in November 1998 with the launch of Russia’s Zarya module. Assembly was delayed due to the tragic loss of Space Shuttle Columbia, which also resulted in the decision to retire all Space Shuttles after completion of the Station. The last major part of the Space Station delivered by a Space Shuttle was the AMS-02 instrument in May 2011.
One more pressurised module will be attached to the Station: Russia’s Nauka Multipurpose Laboratory Module is as big as Zarya and Zvezda. It will be installed on the Earth-facing docking port of the Zvezda module.
ESA is responsible for two key Station elements: the European Columbus laboratory and the Automated Transfer Vehicles (ATV).
The Columbus laboratory forms a substantial part of the Station’s research capability. Fitted with ten interchangeable payload racks, Columbus is a multifunction laboratory that specialises in research in fluid physics, materials science and life sciences.
Europe’s second biggest contribution is the Automated Transfer Vehicle, a supply ship lifted into orbit on an Ariane-5 launcher.
ATV carries up to 7 tonnes of cargo including provisions, scientific payloads and propellant. Once docked, the craft can use its engines to boost the Station to a higher orbit counteracting the faint drag of Earth’s atmosphere.
After the first spacecraft, ATV Jules Verne, ATV Johannes Kepler was launched in 2011 and the next one ATV Edoardo Amaldi was launched in 2012. The fourth, ATV Albert Einstein, will be launched in 2013.
European scientists and engineers contribute to equipment and design across much of the International Space Station. More than a third of pressurised Station elements are designed and built in Europe.
The European-made Cupola is a dome-like structure with a panoramic window that is used as a control room for astronauts operating Station equipment. Cupola’s circular top window is 80 cm in diameter makeing it the largest window ever to fly in space, while six side windows open the view to all directions.
In fact, European technology plays an important part in most Station sections. For example in the United States Destiny module, Europe has installed a material science rack and freezer units. The Japanese module Kibo also uses a European freezer.
European astronauts and users
Only a tiny fraction of the Europeans working on the Space Station will ever go to space. Large dedicated teams of engineers, scientists, technicians and support personnel make spaceflight possible. European mission control centres run experiments and share Station command with Russia and the United States. Astronauts will always be part of a large scientific team on Earth.
Nine User Support and Operation Centres in Europe are responsible for the use and implementation of European payloads on the International Space Station. Under ESA management, the Operation Centres conduct tasks needed to prepare and operate experiments. They act as the link between science teams on ground and the Space Station.
Participation in the International Space Station allows thousands of Europe’s brightest people at hundreds of universities and companies in ESA’s Member States to work on the leading edge of science and engineering.
Now that the Station is fully assembled and astronauts spend more time on science people European scientists are among the first to benefit from the space research facilities they have helped to build.
21 Aug, 2013
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