Science

Space station astronauts hook up life-support to Harmony

by William Atkins

Wednesday, 21 November 2007

International Space Station commander Peggy Whitson and ISS flight engineer Daniel Tani are out floating in space (Tuesday, November 20, 2007) next to the space station connecting cooling lines and power cables to the new Harmony module.

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Watch the spacewalk on NASA Television.

With their work to connect an electrical power grid and cooling network to the module, the astronauts are preparing for next month’s arrival of NASA’s space shuttle Atlantis and its STS-122 seven-member crew. They will bring with them, inside the orbiter’s cargo bay, the European Space Agency’s Columbus scientific laboratory, which will be hooked up to the 17-ton Harmony.

When Atlantis arrives in December, it will dock with the station at the pressurized mating adapter-2 (PDA-2), a docking mechanism that is attached on the forward hatch of the Harmony module. The Harmony module and the PDA-2 must be completely ready in order for Atlantis to dock with the space station.

The pair of spacewalkers began their extravehicular activities (EVAs) a little bit after 5 a.m. EST. Their outside work should take them about six or seven hours.

One of their tasks on Tuesday is to move an 18.5-foot (5.6-meter) external cooling system tray that contains plumbing lines. The lines contain ammonia coolant, which is dangerous to astronauts if some of the substance should get on their spacesuits and enter the space station. If the frozen ammonia gets inside the space station, it could become gaseous, and then mix with the air inside, possibly causing respiratory problems to the astronauts.

Ammonia gas is a serious respiratory tract irritant for humans. Contact with the gas by the human body first causes nose and throat irritations. Later, if in sufficient quantities, it can cause pulmonary edema, or an accumulation of fluids in the lungs. Breathing difficulties occur and, in some cases, death can be the end result.

Consequently, the spacewalkers have to be extra careful not to contaminate their spacesuits, and their living quarters, with the ammonia.

The pair of astronauts will finish the connections to Harmony on Saturday, November 24, 2007. This spacewalk is scheduled to begin around 6 a.m. EST, although it may begin earlier if the astronauts are ahead of schedule. It will be shown on NASA TV.

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