November 20, 2006. Copyright, 2006, Graphic News. All rights reserved

Picture caption

These seven astronauts take a break from training to pose for the STS-116 crew portrait. Scheduled to launch aboard the Space Shuttle Discovery are, front row (from the left), astronauts William A. Oefelein, pilot; Joan E. Higginbotham, mission specialist; and Mark L. Polansky, commander. On the back row (from the left) are astronauts Robert L. Curbeam, Nicholas J.M. Patrick, Sunita L. Williams and the European Space Agency's Christer Fuglesang, all mission specialists. Williams will join Expedition 14 in progress to serve as a flight engineer aboard the International Space Station. The crewmembers are attired in training versions of their shuttle launch and entry 

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Working out in space

LONDON, November 20, Graphic News: When Swedish-born astronaut Christer Fuglesang and Americans Robert Curbeam and Sunita Williams -- the spacewalkers on shuttle mission STS-116 -- step through the airlock into the vacuum of space, they will each be wearing a state-of-the-art EMU, or Extravehicular Mobility Unit.

The space suit must protect the wearer not only from the deadly void of space but from cosmic radiation, high-velocity particles of space dust, blinding solar glare, and extremes of temperature, from a searing 135 degrees Centigrade (275¡F) in direct sunlight to minus 82 degrees (-116¡F) in the shade. Each $12 million EMU is literally a spacecraft in itself.

To dress to work in space is a time-consuming, 25-step activity, which begins the night before the spacewalk, or extra-vehicular activity (EVA).

Normal air pressure on the International Space Station (ISS) is 14.7lb per square inch (psi), or one bar. This is the same as at sea level on Earth, and has the same composition of 20 percent oxygen and 80 percent nitrogen. The EMU operates with a 100 percent oxygen atmosphere at 4.3 psi -- about 25 percent of an atmosphere or 0.25 bar. The astronautÕs blood supply must be purged of any nitrogen or else, like a deep sea diver, nitrogen bubbles will squeeze out from solution in the blood, causing the bends.

The night that Discovery docks with the ISS, Fuglesang and Curbeam will take their sleeping bags into the Quest Airlock for what is called a Òcamp-out pre-breatheÓ. The pressure will be reduced to 0.7 bar and the oxygen increased.

Their EVA on flight day four will begin with a 30-minute exercise period on a stationary bicycle while breathing pure oxygen through a facemask. This rapidly purges the blood stream of excess nitrogen. After making final visits to the toilet, while still breathing from now sweat-fogged facemasks, they will return to the airlock and seal the compartment from the rest of the ISS. The pressure is lowered to the equivalent of being on a mountain at 9,200 feet (2,800 metres), and only then are the oxygen masks removed and suiting up can begin.

It takes about six hours from the time they wake in the morning to the time the airlock hatch is opened.

With the help of an extra crew member each spacewalker tugs on and straightens out wrinkles in their synthetic-fibre long underwear. Each steps into the Lower Torso Assembly (LTA) which contains the legs and boots, and dons the fibreglass Hard Upper Torso (HUT) Assembly to which the arms are attached.The LTA and HUT are locked together.

The composite helmet with a gold-plated polycarbonate visor needs special attention. Each astronaut cleans their visor and spreads a thin layer of anti-fog on the inside surface. If there is too much anti-fog it can make the eyes sting and water; too little and it will fog up -- it has to be just right. A ÒvalsalvaÓ device is installed on the inside of the helmet. Shaped like two small side-by-side mounds, this block of soft rubber is used to pinch the nose, without a helping hand, to clear the ears during pressure changes. 
A drink bag with straw is filled with almost a litre of water and squeezed to expel any air. If air remains it will burp out, creating fluid spheres inside the helmet -- these invariably find their way onto the visor or ricochet around the inside of the helmet as if playing three-dimensional pinball.

The suit-up requires placing a wrist mirror and checklist on the sleeves. This is needed because the helmet wonÕt allow direct reading of instruments on the chest panel -- the data on these is displayed in back-to-front text.

After checking the lights and TV camera, the helper installs the helmet. Inner comfort gloves are pulled on and the outer gloves are mated to the arms.

Once the Life Support System ÒbackpackÓ -- which holds enough oxygen to last for about seven hours -- has been locked to the HUT and the complete suit has been checked for leaks by increasing the pressure to 0.20 bar above airlock pressure, the outer airlock door can be finally opened.

Only then can Fuglesang, Curbeam and Williams begin their six-and-a half hour spacewalk, working in orbit some 220 miles (354km) above the Earth.
/ENDS