ISS crew to walk in space soon

The International Space Station (ISS) crew, i.e. Russian cosmonaut Gennady Padalka and US astronaut Michael Fincke, will be preparing for their June 16 space walk today.

The crew will devote virtually the entire day to practicing their June 16 EVA (Extra-Vehicular Activity), subsequently repairing a defective gyroscope seven days from now. Padalka and Fincke will check their spacesuits for airtightness levels, also separating water inside both Orlan-M spacesuits' hydraulic systems and adjusting their size in the evening, Valery Lyndin, a spokesman for the Russian mission control center, told RIA Novosti.

In his words, both men will install space lights on spacesuit helmets June 10, also filling their water flasks and installing them inside spacesuits. Moreover, Padalka and Fincke will check the operation air valves inside the Pirs (Pier) docking module, from where they will venture into outer space. The crew will also test the communications network, installing US tools on Russian spacesuits; the aforesaid tools will be used to repair the gyroscope on the ISS external surface.

Padalka and Fincke will put on their respective spacesuits June 11, practicing simulated EVA operations inside the station; this training session is called the "dry run".

On February 27, 2004 the ISS crew was forced to shorten its EVA duration because Russian cosmonaut Alexander Kaleri's spacesuit had overheated.

On May 24, 2004 NASA officially asked the Russian mission control center to help perform a space walk involving Orlan-M spacesuits. It turned out during preparations for outer-space repair operations that the cooling system of US EMU (Extravehicular Mobility Unit) had developed a malfunction. Subsequent attempts to repair that system produced no results whatsoever. In this connection, the crew had to opt for another repair-operations concept. Both men will exit from the Russian segment's Pirs airlock, which is located 24.4meters from the site of repair work. After that, they will use a Russian-made Strela (Cargo Boom) crane for reaching the defective US gyroscope, subsequently replacing its power-supply unit.

ISS crews can use Russian spacesuits as well as US EMU systems. Crew members wearing Orlan-M spacesuits can exit from the Russian segment's Pirs docking module, also using the US segment's Quest airlock. Meanwhile spacesuit is adapted for the Quest airlock only.

The semi-rigid Orlan-M spacesuit features an integral metal breastplate comprising the body and the helmet. Meanwhile its legs and sleeves feature soft materials. This spacesuit can be used for repeat space walks.

The Orlan-M spacesuit is a modified version of Orlan spacesuits, which were used rather successfully by orbital-station crews in the course of their long-duration missions.

Orlan-M spacesuits were first tried out by mission commander Vasily Tsibliyev and second flight engineer US astronaut Jerry Linenger during their April 29, 1997 EVA. Both men exited from the Kvant-2 module's airlock compartment of the Russian Mir orbital station.

The EMU and the Orlan differ from each other to some extent.

One can enter the Orlan-M spacesuit through its rear section. At the same time, anyone wishing to wear the EMU spacesuit must be helped by someone else; even special devices can't accomplish this objective.

Russian spacesuits, which have a four-year service life, are serviced and repaired in orbit. Meanwhile the Hamilton Sunstrand company, which has manufactured the EMU, says it can be used for 25 space walks over a 180-day period. After that, the EMU must be brought back to Earth for subsequent repairs.

The Orlan is a one-size-fits-all spacesuit, which can be worn by cosmonauts 165-190-cm tall; the length of its sleeves and legs can be adjusted to fit any spaceman. Meanwhile there are nine standard EMU sizes; four standard sizes are generally used; custom-made spacesuits or soft-cover elements have to be delivered for any big crew member.

Each Orlan-M spacesuit weighs 110 kg. Aluminium alloys have been used to make all Soviet and Russian spacesuits ever since the times of the first Soviet space-technology designer Sergei Korolev, who demanded that all systems must be as light as possible. The EMU features quite a few stainless-steel parts. The US spacesuit weighs 136 kg (minus SAFER, i.e. Simplified Aid for EVA Rescue, equipment.) SAFER equipment, which is, in fact, a small strap-on compressed-gas jet-propulsion unit for returning the astronaut to the station, in case he has left its surface.

Russian spacesuits feature duplicated main systems, i.e. insulating linings, ventilators, water pumps, and pressure regulators. Each spacesuit comes complete with an emergency oxygen tank; its breastplate and double-visor helmet feature rubber linings, as well. The United States perceives EMU systems as quite dependable, preferring not to duplicate them, for the most part.