By Seth Borenstein
Monday, May 18, 2009
HOUSTON, May 17 -- Spacewalkers' specially designed tools could not dislodge a balky bolt Sunday on the Hubble Space Telescope. So they took an approach more familiar to people puttering around down on Earth: brute force.
It worked, but the delay set the astronauts so far behind that they could not get all their tasks done. They had to abandon the replacement of some worn insulation on the telescope for at least a day.
The marathon spacewalk by Atlantis astronauts Michael Massimino and Michael Good took a little more than eight hours, the sixth-longest U.S. spacewalk and a few minutes longer than their Friday spacewalk.
The troublesome bolt attached a handrail to the outside of a scientific instrument Massimino needed to fix. The rail had to be removed or at least bent out of the way. When several tries with different expensive tools could not dislodge the stripped-out bolt, Mission Control in Houston told Massimino to go for the less-precise yank.
At Goddard Space Flight Center in Greenbelt, engineers twice tested that pull on a mock-up before Massimino was told to use his muscles.
"You hope you don't get to the point where you just close your eyes and pull and hope nothing happens," said James Cooper, the Goddard mechanical systems manager for the repair mission. "But we had run out of other options."
Astronauts were careful to tape pieces so they would not fly away and become potential missiles.
"This is like tying branches together in Boy Scouts," Good said.
Atlantis was out of video contact 350 miles above Earth, so controllers in Houston could only listen as Massimino took a breath and pulled.
After a second of silence, Massimino calmly said: "Disposal bag, please."
After nearly two hours of work on the bolt, astronauts went back to the plan to bring the Space Telescope Imaging Spectrograph back from the dead.
Early test results showed that the spectrograph, disabled by a power failure five years ago, was brought back to life. But when further tests started, the instrument put itself into "safe mode" because of temperature problems.
Three of the four Hubble spacewalks so far this mission have been delayed by niggling problems, such as stubborn bolts and objects that would not fit. A fifth and final spacewalk is set for Monday.