Astronauts Suited Up For Spacewalk No. 3

Endeavour mission specialists Drew Feustel and Mike Fincke are suited up in the U.S. Quest airlock at the International Space Station, stepping through a new approach to preparing for spacewalking work in the vacuum of low Earth orbit.

Feustel and Fincke are lifting their legs and moving their arms to raise their metabolic rates. The idea is to more quickly purge nitrogen gas from their bloodstreams. Nitrogen gas bubbles could cause potentially painful or deadly bouts of what SCUBA divers call "the bends." All spacewalkers are subject to decompression sickness because they work in low-pressure suits in a vacuum environment.

The new protocol calls for light exercise for in the airlock for 50 minutes. The exercising is done in increments of four minutes followed by a minute of rest.

The In-Suit Light Exercise procedure obviates the need for astronauts to "camp out" in the Quest airlock overnight prior to a spacewalk -- the standard operating procedure. NASA would like to avoid isolating astronauts in the airlock. Among other things, it would separate the crew members in the event of an emergency evacuation from the station.

The new protocol also reduces the amount of oxygen astronauts must breathe in advance of a spacewalk. That saves limited supplies aboard the outpost.

Feustel and Fincke are preparing to embark on the third of four spacewalks planned during Endeavour's 12th and final stay at the station. Its Endeavour's 25th and final flight before shuttle fleet retirement.

The planned 6.5-hour excursion is scheduled to begin at 1:46 a.m. But the astronauts are running about 15 minutes ahead of schedule and could exit the Quest airlock a few minutes early.