Nov. 2, 2007 -- Planning for one of NASA's riskiest spacewalks ever conceived is down to the wire.
Team Four, a group on standby to tackle any emergencies that come up during a space shuttle or space station mission, has been activated in Mission Control, headed by flight director Ginger Kerrick. The group launched into action Sunday, when astronaut Dan Tani opened a panel on a solar array and found metal shavings, indicating something wasn't working the way it should.
The solar array troubles have multiplied for the space agency since Tani's discovery Sunday. When Cmdr. Pam Melroy attempted to deploy another solar array earlier this week, she discovered it was torn.
Hundreds of engineers and spacewalk experts are working around the clock, scrambling to come up with a safe way for two spacewalking astronauts to fix that torn solar array without getting electrocuted.
Astronauts spend much of their training practicing spacewalks and working out the details before they launch, but no one did any advance planning before Discovery launched for this emergency spacewalk now scheduled for Saturday.
Spacewalkers Scott Parazynski and Doug Wheelock will be working a long way from safety inside the space station as they attempt to mend a torn solar blanket that is generating 120 volts of electricity. The solar array can't be turned off, so it is in essence a live wire that could shock or even electrocute the astronaut if he slips up.
Derek Hassman, lead space station flight director, believes that won't happen.
"We've got adequate controls in place where we are comfortable with the shock hazard," said Hassman.
Astronaut Dave Wolf heads spacewalk planning for the astronaut office. He is confident the teams at the Johnson Space Center can choreograph this spacewalk safely but worries about putting Scott Parazynski on the end of a 90-foot arm and boom with an extension that will leave him more than 30 minutes away from safety if something happens during the spacewalk.
Wolf says it won't be a perfect plan, but it will be a good plan, and his team will be ready when Parazynski opens the hatch and floats out Saturday morning.
"At some point, we have to execute the plan we have instead of having the perfect plan to execute," he said.
He does worry about exposing the astronauts to the solar array.
"We always are [concerned] when you are close to a damaged electrical power system," he said.
What's at stake? The future of the international space station.
Right now, the solar wings on both sides of the space station are crippled. Both systems are producing power for the orbiting outpost, but expansion of the space station may stop if the solar arrays can't be restored to full capacity.
Both sets of solar wings on the space station have a huge joint shaped like a Ferris wheel that allows the wings to track the sun as the space station orbits Earth. Something -- and no one knows what -- in the joint on the starboard array is grinding, and until engineers figure out what it is that solar array is parked.
NASA was going to send astronauts out on a spacewalk to inspect the joint but canceled it when a solar panel tore on the other set of arrays.
The tear happened when astronauts sent commands to a computer to unroll it and part of it snagged. By the time they noticed it and aborted the deployment, it had torn a 2½ foot hole in the panel.
Space station program manager Mike Suffredini said fixing this solar blanket is the top priority in the space program. The $5.6 million panel generates roughly 15 percent of the space station's electricity. There are no spares onboard, and if this panel can't be repaired, it would have to be jettisoned. It would take months before another panel could be delivered and installed.
NASA is trying to finish building the space station by 2010, when the space shuttle fleet is scheduled to quit flying.
Several important additions are scheduled for launch in the next few months. The European Columbus laboratory is supposed to go up on the next shuttle flight in December, and the Japanese Kibo module is scheduled to launch on Valentine's Day 2008. Analysts are calculating how much power they can provide for new additions if these solar arrays can't be fixed.
The man leading the repair spacewalk is Scott Parazynski, on his fifthshuttle flight. He is a very experienced spacewalker, with an eclectic background. He is an ER doctor, and he, at one time, coached the luge team for the Philippines in the 1988 Olympic Games.
This spacewalk -- perhaps his last -- will probably be the most memorable. He is going to be the first astronaut to ride on the end of a boom, grasped by the station's robotic arm. Parazynski will rely on the robotics operators inside the space station to gethim safely out to the solar array -- close enough to repair the damage but not close enough to get hurt by the electrical current.
Clever engineers designed a cufflink like device to fix the torn solar array. It will be used to sew up the 2½ foot hole.
If the repair doesn't work, Discovery's mission will be extended to allow spacewalkers time to go out another day and try again. If the repair succeeds, Discovery will return to Earth Wednesday, Nov. 7.