Station spacewalk begins
BY WILLIAM HARWOOD
STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION
Posted: January 30, 2008
Floating in the international space station's Quest airlock module, commander Peggy Whitson and flight engineer Dan Tani switched their spacesuits to battery power at 4:56 a.m. today - 24 minutes ahead of schedule - to officially kick off a planned six-and-a-half-hour spacewalk. The primary goal of the excursion is to replace a faulty solar array positioning motor to improve electrical generation and clear the way for attachment of European and Japanese research modules.
This is the 101st spacewalk devoted to space station assembly and maintenance since construction began in 1998. For identification, Whitson, call sign EV-1, is wearing a spacesuit with solid red stripes around the legs while Tani's suit (EV-2) features broken stripes.
Today's spacewalk is a bit riskier than usual for two reasons: A mistake managing the latches that hold the motor and its housing in place could result in the solar panel's inadvertent release; and because of the shock hazard associated with unplugging and replugging power cables that route 160-volt electricity from the array into the station. To eliminate any chance of a potentially fatal shock, the work will take place when the station is in Earth's shadow and the arrays are not generating any significant power.
"The choreography for the EVA will be very complex, both on orbit and with the ground," Tani said. "Because we're dealing with a solar array that produces kilowatts of power, we have to be very conscientious of when we're going to be opening connections that will expose us to that power. So the bulk of the activities will have to be performed at night when the solar array is not producing any power, or much power, at all."
The bearing motor roll ring module, or BMRRM (pronounced "broom"), is roughly the size of a beer keg and weighs more than 200 pounds. Replacing it is complicated, Whitson said, "because it's really the guts of what's holding the solar array in place. And so Dan and I will have to coordinate when we release and grapple onto the (motor housing) canister in order not to lose the solar array. That would lose us a whole lot of style points!"
Here is an updated timeline of events, including when live television from the station is possible (in EST; times approximate; NOTE: the first minute of each eclipse period, and the last two minutes, are not usable because of residual power generation):
04:56 AM...Spacewalk begins 05:12 AM...ISS TV downlink window opens 05:49 AM...ISS TV downlink window closes 06:10 AM...ISS TV downlink window opens 06:22 AM...ISS TV downlink window closes 06:47 AM...ISS TV downlink window opens 06:52 AM...ISS enters eclipse 07:00 AM...Failed BMRRM removal begins in eclipse 07:27 AM...ISS enters sunlight 07:35 AM...ISS TV downlink window closes 08:24 AM...ISS TV downlink window opens 08:25 AM...ISS enters eclipse 08:30 AM...New BMRRM installation begins in eclipse 09:00 AM...ISS enters sunlight 09:10 AM...ISS TV downlink window closes 09:55 AM...ISS enters eclipse 10:00 AM...ISS TV downlink window opens 10:05 AM...Solar alpha rotary joint inspection begins 10:30 AM...ISS enters sunlight 11:20 AM...ISS TV downlink window closes 11:26 AM...Spacewalk ends (time approximate) 11:30 AM...ISS enters eclipse 11:35 AM...ISS TV downlink window opens 12:05 PM...ISS enters sunlight 12:59 PM...ISS TV downlink window closes