Prebreathe Protocol Before Spacewalkers Exit Station

Expedition 28 spacewalkers Mike Fossum and Ron Garan are using the new In Suit Light Exercise (ISLE) protocol to prepare for today’s excursion, a technique first used on shuttle mission STS-134. Rather than “camping out” in the Quest Airlock at low air pressure last night, the pair waited until this morning to breathe pure oxygen through air masks for an hour as the air pressure inside Quest is lowered to 10.2 pounds per square inch.

After that, they will don their spacesuits and perform light exercise, moving their legs inside the suits for 50 minutes to raise their metabolic rate and purge nitrogen from their bloodstreams. This procedure uses less of the space station’s oxygen supply than the “campout” did and achieves the same results, protecting the spacewalkers from “the bends” when they enter the vacuum of space.

The spacewalk is slated to start at 8:44 a.m. EDT.