Astronauts venture to far end of station on fourth spacewalk
NASA takes it slow and steady as team installs batteries.
CAPE CANAVERAL, Florida
At Mission Controlâ€™s request, a pair of spacewalking astronauts took it slow and easy heading out to the far end of the international space station Friday, then tackled a series of critical battery changes.
Christopher Cassidy and Thomas Marshburn ventured out as the shuttle-station complex soared 220 miles above Kazakhstan. By the time they had circled the planet, 1-1/2 hours later, they had their first fresh battery installed.
â€śHave fun storming the castle, guys,â€ť astronaut David Wolf called out from inside.
The last time Christopher Cassidy went out, two days earlier, he was so enthusiastic and moved so fast that the air-cleansing canister in his suit could not keep up. That resulted in rising carbon dioxide levels that forced an early end to the spacewalk.
â€śHeâ€™s a Navy SEAL, heâ€™s in great shape, and so we really needed to tell him, â€™Hey, we know you can do this really well and really fast ... just slow down a little and take your time,â€™ â€ś explained flight director Holly Ridings.
Cassidy and Marshburn took the advice to heart. â€śDonâ€™t work too hard, Tom, just take your time,â€ť Cassidy told his partner.
Despite Cassidyâ€™s effort to stay relaxed, however, his metabolic rate was a little high at one point and Mission Control gave some of the early battery tasks to Marshburn. That gave Cassidy, a 39-year-old Navy commander, a bit of a break.
â€śIâ€™m just going to sit here,â€ť Cassidy said. He noted that he wanted the lithium hydrogen canister in his suit â€” for removing his exhaled carbon dioxide â€” to operate at its maximum efficiency.
NASA added the unfinished battery work to Fridayâ€™s spacewalk, the fourth for shuttle Endeavourâ€™s visiting crew. That pushed the planned length of the spacewalk to 7-1/2 hours, an hour longer than usual.
Cassidy and Marshburn had four new batteries to plug in Friday. Two of those batteries should have been installed Wednesday.
The balky batteries â€” 3-foot-square bundles weighing about 370 pounds each â€” are designed to store power collected by the solar wings on the far left end of the space station. Cassidy managed to replace just two of the 9-year-old batteries on Wednesday, while working with Wolf.
Each of the six new batteries costs $3.6 million. The old ones will be returned to Earth aboard Endeavour at the end of next week.
One more spacewalk is planned for Monday.
Cassidy â€” an explosives and combat expert who went into Afghanistan two weeks after the Sept. 11, 2001, terrorist attacks â€” said in a series of TV interviews Thursday that he experienced no symptoms of carbon dioxide buildup during Wednesdayâ€™s spacewalk and was never worried.
Back at the launch site, meanwhile, NASA conducted more testing on the fuel tank that will be used for Discoveryâ€™s launch at the end of August. Shuttle managers want to be absolutely certain that the foam insulation on the central area of the tank was attached properly.
During Endeavourâ€™s liftoff on July 15, an unusually large amount of foam broke off and a few pieces struck the shuttle, causing minor damage.