I’ve posted quite a bit on things related to the International Space Station, so I suppose it’d be useful to do a quick rundown on the lineage of the space station – how many have we had up there, how did we arrive at the present design – as the full solar panel array is unfurled in the skies above.
Space stations have a number of things to worry about. Increased radiation from the Sun and the radiation belts, remaining low enough to avoid these, but high enough to stay in orbit, producing power and recycling enough of the materials used by the inhabitants to remain habitable, shifting orbits in the case of possible collision with debris and having a reliable computer system. Some have been successful, others less so.
Who wants a bolthole in space?
Well, quite a few different powers would like some little getaway up near the stars. The two that were in the best position to do it, however, were the Soviet Union and the United States during the Cold War. The Space Race between the two was fought on many grounds – satellites, rocket technology – and some say ended with the planting of an American flag in the lunar regolith in 1969. However, the battle for manned orbital dominance raged on until the collapse of the Soviet Union and the unification of the two space programs.
Despite all this, the initial war that led to the building of the first US space station came not from external threats, but internal wrangling. Wernher von Braun, the ex-Nazi rocket scientist submitted proposals for an orbital station along with his Moon mission plans to the army in the late 1950’s. The following decade saw the US Air Force begin plans to put this into operation, much to the horror of the new NASA organisation. Nasa responded with Skylab, a space station built out of parts of the rocket that launched it, effectively blasting out the fuel and using the tank of one of the launch stages as the main body. However, before Skylab was able to fly, the Soviet Union already had two space station programs in operation – DOS, the civilian space station program and OPS, the military space station program. Almaz was the name of the OPS station program, however OPS stations were disguised and launched under the pretense of being civilian stations under the Salyut series.
In 1969, the Americans had landed on the Moon and put the Soviet space program on the back foot, desperately searching for a new direction. Vladimir Chelomei developed a military space station named Almaz. This did not meet with government approval and was initially abandoned, but mirroring the Air Force-Nasa conflict in the US, a more science oriented group under the leadership of Sergei Korolev proposed an adaption of Almaz for civilian scientific use. This could be developed and put into orbit far more swiftly than the American Skylab proposal and was immediately sanctioned. Although Almaz would be secretly resurrected within the Salyut program, on April 19th 1971, Salyut 1 became the first ever Space Station.
1st Generation Space Stations
The first generation space stations are so called because they consist of a single habitable tank and a docking port. In the case of Salyut 1, there were three main compartments – a docking cone around 2m in diameter, a 4m diameter main compartment, where people lived and worked and an auxiliary compartment, 2m in diameter, which was unpressurised and contained all the workings of the station. The station was 20m in length. The station also contained the Orion 1 Space Observatory, and during the space station’s operational time, Viktor Patsayev became the first human to operate a telescope outside of the Earth’s atmosphere, taking ultraviolet spectra of Vega and Beta Centauri. Until this point, telescopes had to be balloon, satellite or rocket mounted and flown without operators to view wavelengths outside the visible region (which are absorbed and stopped high in the Earth’s atmosphere). The first attempt at a manned mission to Salyut 1 failed when the crew found they couldn’t dock securely. Soyuz 11 managed to dock and the crew spent nearly 24 days on the station. They carried out astronomical, meteorological, geological and biological tests before finally departing after electrical fires and other problems on board. Sadly after they left, the Soyuz 11 vehicle depressurised during descent, killing the three Cosmonauts on board. Pressurised suites were always worn during descent after this accident. Salyut 1 was taken out of orbit and sent on a controlled descent over the Pacific ocean on October 11th 1971, ending a world first in space exploration.
Almaz returned in the form of Salyut 2, only to be destroyed during launch on April 4th 1973. A month later on May 11th, the real Salyut 2 was launched flawlessly, but a computer failure lead to the orbital rockets firing continuously until the fuel had run out. The Soviets covered up the loss by suggesting it was just an old rocket and allowed it to fall back to Earth. 14th, Skylab was launched by the US. Skylab barely made it to orbit, losing the micro-meteorite and sun shield as well as one of its main solar panels. The first manned mission to skylab, eleven days later, began with emergency repairs to salvage the station. These were successful and the astronauts remained on board for 28 days. Further missions to the station on the 28th of July and 16th of November put astronauts on the station for 59 and 84 days, respectively. Skylab carried out 2,000 hours of experiments including solar experiments that lead to the discovery of coronal holes – regions of the Sun that appear dark when viewed in x-ray, where the fast solar wind streams from. Skylab was abandoned in 1974 after the third crew departed and the US withdrew from manned spaceflight after the Apollo-Soyuz Test Project. Skylab remained in orbit until expansion of the atmosphere during an active period of the solar cycle began to initiate re-entry. The US had managed to re-establish contact and reorientated the station for re-entry over the Indian Ocean, from where some of it was later recovered.
A few months after Skylab was abandoned, Almaz made it into orbit under the name Salyut 3. Launched on the 25th June 1974, Salyut 3 obtained an altitude of around 270 km. Soyuz 14 launched on the 3rd of July to drop off a crew, who then remained for nearly sixteen days. Salyut 3 was the first station to maintain geostationary orbit – staying above the same spot on the Earth’s surface, allowing studies of that spot. This was achieved not by being in the Clark orbit (where the station would’ve naturally remained geostationary) but by firing the thrusters of the station repeatedly. Salyut 3 contained a number of cameras, a detachable module for recovery of data and a gun, fired three times against target satellites between 0.5-3km away, successfully destroying the target. On August 26th, Soyuz 15 launched to attempt to drop off a crew, but failed to dock. On the 23rd of September, the detachable module returned to Earth. On the 24th of January 1975, the gun was tested and later that day, Salyut 3 re-entered the atmosphere.
A month before the decay of Salyut 3, Salyut 4 was launched on December 26th 1974. A copy of the ill-fated DOS-3, Salyut 4 made it into orbit and provided a platform for x-ray studies of space. Soyuz 17 launched on February 10th 1975, dropping off a crew who remained for nearly 30 days to carry out astronomical observations. Soyuz 18 launched on May 24th and dropped off a crew for nearly 63 days for solar and Earth observations as well as biological experiments including vegetables grown in space and fitness training. Soyuz 20 made a three month unmanned dock to the station to prove it was durable for long period occupation. Salyut 4 was taken out of orbit on 2nd of February 1977 and re-entered the atmosphere the following day, burning up over the Pacific Ocean.
Salyut 5 was launched on 22nd of June 1976. It was the third and final Almaz station and was very similar to Salyut 3 in design, including the detachable data module. Soyuz 21 launched on July 6th to put the first crew on board. They remained for over 49 days, performing military and solar experiments as well as a link-up to schoolchildren on the ground. Poisonous gases filled the station at one point and the cosmonauts returned in poor physical and mental shape. Soyuz 24 launched on the 7th February 1977, putting a crew on board who stayed for over 17 days. They changed the cabin air, repaired the station and performed solar studies. The station ejected its data module the day after this mission ended. Although a third manned mission was planned, the station ran low on fuel and re-entered the atmosphere on the 8th of August 1977, ending the first generation of stations.
2nd Generation Space Stations
The second generation of space stations is considered to have begun with the addition of a second docking port to the original Almaz spaceframe in Salyut 6. The addition of a second docking port meant new crews and resupply modules could arrive at the station whilst the vehicle of the original crew remained docked, allowing long duration stays. Salyut 6 was launched on the 29th of September 1977, shortly after the end of the previous generation of stations. The station was composed of the most successful parts of the previous stations and meant for a long stay in orbit. During its lifetime and in addition to the manned crew, the station received 12 resupply trips, including fuel and equipment without disturbing the science going on. The station was also more habitable than previous versions, with cots for sleeping, showers, soundproofing for machinery and a gymnasium. The station carried a 1.5 meter telescope, operating in infrared, ultraviolet and submilimetre wavelengths. A radio telescope was later delivered and topographic and photographic cameras watched the Earth from above. In total, there were 6 long duration and 10 short duration stays on board Salyut 6, varying from just under four days to just under 185. Many astronomical and human adaptability experiments were carried out in this time, and the station welcomed visitors from all over the Warsaw Pact. After nearly half a decade in space, and following the launch of the next station, Salyut 6 was decommissioned and taken out of orbit on the 29th of June 1982 – by which time I was in the world, looking up at the stars.
The final Salyut station, and indeed the final of the second generation stations, was Salyut 7. Launched on the 19th of April 1982, Salyut 7 was originally the back up for Salyut 6, but as the intended next station Mir wasn’t out of development, 7 became the next mission. It served as a link between the second and third generations as the second docking port became used to test the adding of new modules to the station. The station had constant hot water, redesigned console seats, a fridge and electric ovens. A porthole had its UV filter stripped off to act as a sterilising bay. The visitors to the station included French and Indian cosmonauts. The station was used to test the docking of large modules directly and although it suffered several technical failures, the experience gained in salvaging the station was to be used extensively with Mir. Six crews stayed on Salyut 7, ranging from 8-237 days in duration. On 9th of September 1983, Salyut 7 suffered a fuel leak. Several tools were sent up and spacewalks undertaken to repair the leak successfully. On the 12th of February 1985, the station shut itself down and all contact was lost. The next mission to the station found the walls covered in ice and all systems down, though structurally intact. The fault was identified as a sensor controlling battery charge and after the batteries had been replaced, the station warmed up for several more years of operation. The station was taken out of orbit on the 7th of February 1991. This ended the second generation of space stations.
3rd Generation Space Stations
During Salyut 7’s stay in orbit, the nations below began to reach once again for new stations. In 1984, Reagan announced the US would be creating Space Station Freedom, later canceled but revived as the backbone of the International Space Station. In 1985, Europe announced the Space Station Columbus, which later became a module of the International Space Station. But it was in 1986 that the final Soviet station was launched, one whose technological achievements would underpin the design of the ISS, that station was Mir. Launched on the 19th of February 1986, the Mir core module was joined by the rest of the station’s modules in a ten year construction program that outlasted the Soviet Union below it. The result of an upgrade to Almaz first planned in 1976, from which the second generation appeared as a spin-off, Mir was the first space station designed for long term continuous inhabitence. Despite its long planning process, Mir was launched prematurely due to political imperative. As a result, the infrastructure wasn’t yet in place to launch all the required modules. Cosmonauts instead moved from Mir to Salyut 7, taking material from that station and taking it back to Mir over 124 days. The first 51 were spent turning on Mir and getting it working, the next fifty one on Salyut 7, gathering the material whilst an unmanned vehicle tested Mir’s transfer module and added more material. Then back for another 20 days on Mir conducting Earth observations. On September 5th 1989, the next module of Mir was launched and with it a human presence that would continue for just shy of a decade. Progress in building the station then continued until the launch of October the 2nd 1991. After this date, the Soviet Union fell without another launch and the two modules still to go had to be mothballed without the money to launch them. In September 1993, it was announced that the US and Russia would both co-operate in creating the International Space Station. This would involve two phases, the first would be shuttle missions to Mir. This meant a US presence on the station, the launch of the two modules mothballed previously and the construction and launch of an adapted docking module. In the mid 90’s Mir suffered two disasters – a small fire and a collision with an unmanned Progress vehicle, which holed one of the new modules. Although the station was severely damaged and the US nearly recalled its astronauts due to the perceived dangers, the station was repaired. US astronauts left in 1998 and all others cleared out by August 1999. Funding was diverted to the ISS and Mir burnt up over the South Pacific on March 23rd 2001.
The International Space Station is presently under construction. As I write, the space shuttle Discovery, which removed the final US astronauts from Mir is conducting the final ever shuttle mission, STS-119, and has installed the final solar panels, taking the images in the video below (click through for high definition). The ISS incorporates the planned Mir 2, Space Station Freedom and the Columbus project. It has been visited by people from sixteen nations and hosted the first six space tourists. It is expected to be completed by 2011 and already spans nearly 200 meters. The International Space Station can be viewed from the ground via timings released through Heaven’s Above or Nasa’s own version of that website. Apps have been developed to allow Heavens Above data to be twittered to people in certain areas – also includes an rss feed for those without twitter. And I’ve posted pictures of 1-second exposure trails of an ISS pass in a previous post. Like Mir, the ISS can also be tracked by amateur radio hams, and video footage of the day is also now being released.
Private Space Stations
Although many are planned, there are currently two private space stations in orbit of the Earth. Genesis I was launched on July 12th 2006 and Genesis II on June 28th 2007. I suffered a massive radiation event, but recovered and returned to optimal operating capacity. II carries a space bingo set for public entertainment, but both stations are unmanned and are intended as one third scale models of the real inflatable station to be launched in the future.