Astronauts ready for 4th spacewalk of busy mission
20 Mar 2008 09:19:27 GMT Source: Reuters
By Ed Stoddard HOUSTON, March 20 (Reuters) - Astronauts aboard the International Space Station prepared for a spacewalk on Thursday to test a heat shield repair technique and replace a failed circuit breaker. It will be the fourth of five spacewalks scheduled during space shuttle Endeavor's busy 12-day visit to the orbital outpost for construction and repair work. "It will be a very ambitious day. It's a day that we've been waiting for for awhile," shuttle flight director Mike Moses said at the Johnson Space Center in Houston late on Wednesday. The heat shield test had been planned on a previous shuttle mission, but had to be shelved for more urgent tasks. Astronauts Robert Behnken and Mike Foreman will "camp out" during their sleep period in the station's Quest airlock to purge nitrogen from their bodies ahead of the spacewalk, which was set to start at 6:28 p.m. EDT (2228 GMT) on Thursday. The repair technique to be tested on the spacewalk will be conducted on experimental heat shield tiles that have been intentionally damaged. NASA wants to do the test before sending a shuttle crew to fix the Hubble Space Telescope this summer. Astronauts flying to Hubble won't be able to reach the space station for shelter if their ship is too damaged to return to Earth. NASA developed inspection and repair options after losing shuttle Columbia and its seven-member crew in a 2003 due to undetected heat shield damage. Thursday's test will involve an instrument called a tile repair ablator dispenser, which is essentially a sophisticated caulk gun. It will dispense a gooey material to fill gouges in the damaged tiles. Such damage could be inflicted during take-off. It is hoped the substance would protect the tiles during re-entry into the Earth's atmosphere. The sample tiles will be returned to Earth to undergo extensive testing on the ground. The procedure has been tested extensively in a vacuum and at zero gravity, but not in space. The astronauts had much of Wednesday off, taking a much needed break from their grueling mission. The crew has already assembled a Canadian-built robotic maintenance man on a trip also used to deliver a storage room for Japan's upcoming Kibo laboratory complex.
Yigal Master, a senior research development engineer at Aqwise, holds a "biomass carrier" at the company's plant in Yavne, south of Tel Aviv March 11, 2008. A recycling system developed in ...
