Risky Business
NASA revealed plans for a spacewalk to repair a torn solar panel today. The work will entail astronaut Scott Parazynski riding the robotic arm of the International Space Station to make the repairs. One of many potential hazards is the fact that this will be "live line" work - the solar panel is producing electricity. There is no way to turn it off or safe the system.
The space agency said astronauts will attempt to repair the working power-generating solar array, which partially tore at its hinges during deployment on Oct. 30. Mission managers indicated most details are set for the spacewalk, but gave themselves a 1:08 a.m. ET (0508 GMT) deadline early Friday to ship complete instructions up to astronauts.
"We're faced with a difficult situation," said David Wolf, head of the EVA branch for the astronaut office, here at Johnson Space Center. "I think we're onto a solution that should work and get us pretty close to a permanently acceptable situation."
The extravehicular activity, or EVA, will send STS-120 astronaut Scott Parazynski on a one-hour ride on an extended robotic arm to the damage site while fellow astronaut Doug Wheelock looks on. Donning protective goggles, astronauts in space worked today to craft "cuff links" that should button up the 2.5-foot (0.76-meter) tear in the array.
If Parazynski does not effect a repair from his 90-foot-long (27-meter-long) robotic ride, mission managers said spacewalkers could try again on a following day.
Derek Hassmann, ISS lead flight director for the STS-120 mission, said teams are still working around the clock to get the complete details together for the fourth spacewalk. Management teams delayed the EVA to Saturday to buy more time.
"We knew it would be a full-court press to get there on Friday, and I'm disappointed that we didn't get there," Hassmann said. "But I'm satisfied we made a good call."
This is going to be a very dangerous EVA for Scott Parazynski. Keep him in your thoughts and prayers.
By NortonPete, Thursday, 1 November , 2007 @ 8:34 pm
110Volt kills more people than any other voltage because 110 volt is the most common power available in the US.
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Hassmann said the EVA carries a risk of electric shock via the 110 volts coursing through one part of the solar wing, which generates about 13.4 horsepower (that of medium-sized backup generator).
“Once [solar arrays] are deployed, they start producing power as they’re designed to do,” Hassmann said of the 110-foot (33.5-meter) sail of solar cells. “There’s nothing we can safe or turn off the array while it’s deployed.”
Well God speed and be careful.
By Gaius, Thursday, 1 November , 2007 @ 8:37 pm
It would be DC current, NortonPete. Less lethal than AC but dangerous even so.