Spacewalk's Success Hinges on Bolt
Stuck Fastener Is Hurdle as Hubble Gets New Camera
Friday, May 15, 2009
Four astronauts with four PhDs, backed by the collective brainpower of NASA and riding a multibillion-dollar spacecraft, came face to face yesterday with what appeared to be an immovable object: a bolt.
The bolt secured the celebrated Wide Field and Planetary Camera 2 to the inside of the Hubble Space Telescope. For almost 16 years it had kept the camera in place. And it had no intention of relenting at this late date, no matter how much the astronauts wanted to swap the old camera for a new one.
If the bolt didn't budge, the old camera would not budge, either, and the new, more sensitive replacement, capable of probing even farther into the depths of space and time, would return to Earth as a $132 million piece of ballast. All of this made for high drama during the first of five scheduled spacewalks in five days to service the Hubble.
Spacewalkers John Grunsfeld (doctorate in physics) and Andrew Feustel (doctorate in geological sciences), who will be a team on three of the spacewalks, began their seven-hour, 20-minute extra-vehicular scramble at 8:52 a.m. Feustel stood on the end of a robotic arm operated from within the shuttle by Megan McArthur (doctorate in oceanography). Feustel's and Grunsfeld's movements were coordinated by Mike Massimino (doctorate in mechanical engineering).
"Too cool!" Feustel said as he came out of the airlock. "Hoo-hoo!"
The first major task was the removal of the Wide Field and Planetary Camera 2, the instrument that took many of the Hubble's most famous images. The astronauts needed to replace it with the Wide Field Camera 3.
Feustel used a hand-held socket wrench with an extension to try to loosen the bolt, which was hidden from sight but accessible via a hole in the camera's exterior. But it remained stuck.
Grunsfeld retreated to the airlock to fetch a new tool for Feustel, but that one didn't work, either.
Feustel went back to the socket wrench, which had been designed to apply only a certain amount of force before slipping, a precaution against breaking the bolt and trapping the old camera inside the telescope.
"Still slipping," Feustel reported time and again.
The astronauts had one final option: more elbow grease. They could remove the constraints on the wrench to permit Feustel to put as much force on the bolt as he wished.
"What are the implications if I over-torque and break the bolt?" Feustel asked.