Live in orbit: Walheim unbolting tank

Walheim and the nitrogen tank









Schlegel and Walheim

Spacewalkers working in payload bay

Riding the space station robot arm, Rex Walheim is unbolting a nitrogen tank in the shuttle's payload bay. It will be swapped with an empty tank on the space station.

Nitrogen in the tank is used to pressurize the space station's cooling system, which circulates ammonia, a toxic form of nitrogen with three hydrogen atoms attached.

Beginning the mission's second spacewalk at 9:27 a.m. EST, Walheim and German astronaut Hans Schlegel climbed to the payload bay.

"Welcome to spacewalking, Hans," said Walheim, who is making his fourth spacewalk.

"I'm holding on to Columbus. It's a good feeling," said Schlegel as he climbed across the newly installed European laboratory on his first spacewalk.

Schlegel is on a mission of redemption, having missed his first spacewalk Monday due a medical condition that neither NASA nor he would disclose. He has recovered.

Click for interactive graphic on Columbus installation.

Click for STS-122 fact sheet.

Click for NASA-TV schedule, which details mission events.















The nitrogen tank assembly (NTA) sits in the payload bay beneath two European experiments, SOLAR and EUTEF. The spacewalkers will return the old tank to the payload bay.