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Explainer: the International Space Station

The International Space Station after undocking from the now-retired Endeavour space shuttle. NASA

As the most visible man-made object in the night sky the International Space Station (ISS) is of significance to humankind. It takes humans from being explorers of space to being residents of space.

The Russians launched Zarya, the first module of the ISS, on November 20, 1998. It has grown considerably since then and has been continuously inhabited since November 2, 2000.

Some 208 individuals from 35 expeditions have visited it since then. It’s the ninth space station to be inhabited, following the Salyut (and Almaz), Skylab and Mir stations.

Science and the space station

The ISS fulfils three broad research roles: space medicine, Earth and solar studies, and microgravity experiments.

The Zarya module. Wikimedia Commons

Understanding the response of the human body to low and microgravity is critical for space exploration. Astronauts undergoing long periods of weightlessness – such as in flights to and from Mars – will need to understand the impact of this on their ability to carry out tasks, both routine and emergency.

The space station provides an ideal environment to study many aspects of humans in space, including: balance, digestion, muscle and bone retention and heart behaviour.

It also provides a unique window on the earth and sun – one in which scientists can use their understanding to respond to opportunities as they arise as well as conduct scheduled experiments and observations.

As a solar observatory, the space station is clear of Earth’s atmosphere, giving a unique perspective on terrestrial weather and atmospheric science.

What happens if you wring out a wet cloth in microgravity?

The four laboratory sections house experiments selected on their scientific merit or educational and industrial interest. These include understanding how microgravity effects animal and plant growth, and understanding and developing novel industrial processes.

One of the main “big science” experiments on the space station is the alpha magnetic spectrometer (AMS) – an instrument designed to search for dark matter.

The AMS has been in operation and collecting data since June 27, 2011 and has an expected operational lifetime in excess of ten years.

The International Space Station with the Endeavour Space Shuttle docked, along with descriptions of each section of the station. NASA

A tour of the International Space Station

Approaching the the Rassvet dock in your Soyuz spacecraft, you realise just how big and frail the space station is.

Its most visible features are the eight solar arrays. They generate 84 kilowatts of power and have a wingspan of 73 metres, wider than a Boeing 777. They, along with the array of habitable modules, are supported by a central truss.

An hour-long tour of the ISS.

As you dock you can see nearby the Russian crew’s Soyuz craft docked at Poisk. At the other end, on the Harmony node, is a newly captured SpaceX Dragon supply ship.

Through the cramped airlock you enter the Zarya module. After taking a moment to orient yourself in this weightless environment, you proceed down a circular tunnel to the Zvezda service module.

This is the space station control and services centre, containing the Russian guidance and navigation computers.

It’s also the sleeping and hygiene quarters for two of the cosmonauts. In an emergency it can support all six of the crew.

Back through Zarya you’ll come to the US-built Unity node, a galley where it is possible for all the crew to gather and eat together.

Mealtime in the Unity node. NASA

Just off from this is the Italian-built Tranquility node, which is multi-purpose - with storage, berthing and habitation facilities. It houses the ESA-built observatory, the Cupola.

With its six side windows and a top window the Cupola gives observers a Millenium Falcon-type view of Earth below.

You wind your way back to Unity then through the truss structure (that supports the solar arrays and the Canadarm2) to the Destiny Laboratory – the primary US research facility. Continuing on from here, you reach Harmony.

You note the Destiny and Harmony nodes are square, rather than round like the older modules. This gives four usable working “walls” - there is no up or down, so no floor or ceiling.

Besides velcroing objects to every available “wall” space, the next noticeable thing is the total absence of chairs.

Harmony is home to four crew. The sleeping berths radiate into each “wall”. Each is about the size of a phone booth and have a sleeping bag-type arrangement as well as computer and space for personal effects.

NASA astronauts Ron Garan (bottom) and Cady Coleman, European Space Agency astronaut Paolo Nespoli (left) and Russian cosmonaut Alexander Samokutyaev, all Expedition 27 flight engineers, pose for a photo in the Harmony node of the International Space Station. NASA

Sleeping on the ISS is a novel experience. The station orbits Earth every 90 minutes, which means there is a sunrise and sunset every hour and a half.

The Harmony node also houses sanitary (yes, that is your toothbrush and toothpaste velcroed to the wall) and exercise facilities. A treadmill, gym and seatless exercise bike are part of the necessary exercise regime to ensure muscle does not waste away in the microgravity environment of the space station.

Off Harmony are the Japanese Kibo and European Columbus laboratories.

And … that’s it! This is your world for the next six months, all 388 cubic metres of it - about half the interior space of a Jumbo jet.

The international space residents

The first expedition of William Shepherd (US), Yuri Gidzenko (Russia) and Sergei Krikalev (Russia) was launched on a Russian Soyuz on October 31, 2000 and returned on the space shuttle Discovery on March 21, 2001.

Expedition #35 crew. NASA.

At the moment, the ISS is hosting a six-person expedition, #35. Current commander Chris Hadfield (Canada) and flight engineers Tom Marshburn (US) and Roman Romanenko (Russia) docked on December 21, 2012.

Robonaut 2, or R2, the first humanoid robot to travel to space and the first US-built robot to visit the space station, performs a few finger motion and sensor checkouts aboard the ISS. NASA

Chris Cassidy (US), Alexander Misurkin (Russia), and Pavel Vinogradov (Russia), also flight engineers, docked on March 28, this year, replacing then-commander Kevin Ford (US) and flight engineers Oleg Novitskiy (Russia) and Evgeny Tarelkin (Russia).

You can watch the ISS crew live when they’re on duty.

Expedition #35 is an all-male crew, but 31 women have flown to the space station – including Expedition 16 commander Peggy Whitson, the station’s first female commander. In all, there have been nationals from 15 countries, including seven tourists.

International co-operation

In the Memorandum of Understanding between NASA and Roscosmos, the ISS is to provide for a variety of capabilities, such as

  • a laboratory in space, for the conduct of science and applications and the development of new technologies

  • a permanent observatory in high-inclination orbit, from which to observe Earth, the Solar System and the rest of the Universe

  • a transportation node where payloads and vehicles are stationed, assembled, processed and deployed to their destination

  • a servicing capability from which payloads and vehicles are maintained, repaired, replenished and refurbished

  • an assembly capability from which large space structures and systems are assembled and verified

  • a research and technology capability in space, where the unique space environment enhances commercial opportunities and encourages commercial investment in space

  • a storage depot for consumables, payloads and spares

  • a staging base for possible future missions, such as a permanent lunar base, a human mission to Mars, robotic planetary probes, a human mission to survey the asteroids, and a scientific and communications facility in geosynchronous orbit

In the 2010 US National Space Policy, the ISS was given additional roles of serving commercial, diplomatic and educational purposes.

The ISS has acted as an example and vehicle for international co-operation, but the US has vetoed China’s participation. China, as a result, is now pursuing its own space laboratory program.

The first of these, Tiangong-1, is in orbit and has docked with Shenzou-9, but is still to be inhabited.

Where to?

The US Administration will fund the ISS until 2020. With continued interest from the international community, the space station should continue as a vehicle for fruitful science and demonstration of international co-operation for at least this decade.

The development of commercial spacecraft also provides a second string to the station’s future. SpaceX has demonstrated its capability to deliver cargo and possibly crew to supplement the ageing Russian Soyuz capability.

Only time will tell whether the US allows the addition of China and India, Asia’s space-capable nations, to the ISS fraternity.

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