Station crew set for innovative spacewalk
BY WILLIAM HARWOOD
STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION
Posted: February 3, 2006
Space station commander Bill McArthur and flight engineer Valery Tokarev are gearing up to venture outside the orbital lab complex late today to perform critical maintenance and to "launch" an old Russian spacesuit loaded with ham radio gear.
Making the 64th spacewalk devoted to station assembly and maintenance, McArthur and Tokarev are scheduled to open the hatch of the Pirs airlock module around 5:20 p.m. to begin a six-hour excursion.
Going into today's outing, 56 astronauts representing five nations had logged 378 hours and 40 minutes of spacewalk time since December 1998. This will be the second space station EVA by McArthur and Tokarev, who last worked outside on Nov. 7.
But one of the cable cutters fired late last year for no apparent reason, severing one of the two power-data-video cables needed to operate the platform. NASA astronauts plan to replace the severed cable during the next shuttle flight but until then, flight controllers want to make sure that whatever caused the suspect cable cutter to fire can't happen again.
The issue is critical because the station's robot arm is required to install extensions to the lab's solar array truss during upcoming assembly flights. NASA flight rules prohibit the movement of the arm transporter until full redundancy is available.
While installation of the safing bolt is the most technically significant objective of today's spacewalk, it will take a backseat in media coverage to the deployment of an old Russian Orlan spacesuit loaded with amateur radio equipment.
McArthur and Tokarev plan to "launch" SuitSat right after exiting the Pirs airlock module, gently pushing it away in a retrograde direction along the station's orbital path.
In a scene reminiscent of actor Gary Lockwood's cinematic death in "2001: A Space Odyssey," the spacesuit will float away like an overboard astronaut, remaining in orbit for several days until finally burning up in the atmosphere.
During its brief orbital lifetime, however, the spacesuit will transmit telemetry, using a digitized voice, on an FM frequency that can be heard by normal police scanners and similar radios: 145.990 MHz. Amateur radio operators with more sophisticated equipment can try to pick up a slow-scan TV image beamed down from SuitSat.
"SuitSat is a Russian brainstorm," Frank Bauer, a ham radio enthusiast and manager at NASA's Goddard Space Flight Center, said on a NASA web page. "Some of our Russian partners in the ISS program, mainly a group led by Sergey Samburov, had an idea: Maybe we can turn old spacesuits into useful satellites."
Intended to inspire students in a global educational effort, the spacesuit is equipped with three batteries, sensors and a Kenwood radio transmitter.
"As SuitSat circles Earth, it will transmit its condition to the ground," Bauer said. "Will the suit overheat? How long will the batteries last? Can we get a clear transmission if the suit tumbles?"
Students, teachers, Scout leaders, amateur radio enthusiasts and other interested readers can use NASA's J-Pass satellite tracking utility to determine when SuitSat will be above the local horizon and thus within range of radio scanners: http://science.nasa.gov/RealTime/JPass/25/JPass.asp.
After launching SuitSat, McArthur and Tokarev will make their way to the top of the Russian Zarya module's docking adapter and move over to the U.S. side of the station. They will remove a Russian grapple fixture that has been stored on the side of a U.S. component and reposition it on Zarya's docking adapter. The grapple fixture will be used during a future mission to anchor a Russian space crane. The crane, in turn, will be used to move Russian micrometeoroid panels.
With the grapple fixture in place, the spacewalkers will move up to the station's solar array truss for installation of the safing bolt on the mobile transporter.
"On December 16th, we suffered a failure of a trailing umbilical system cable," said Kirk Shireman, deputy space station program manager. "This cable provides power, data and video to the mobile transporter when its translating. This is one of two cables that perform this function. After analyzing it, we believe the cable was cut by a failure in the TUS disconnect actuator, which is located on the interface umbilical assembly. ... That's where we believe this failure occurred.
"We believe the most likely cause of this anomaly is a mechanical failure inside that TUS disconnect actuator. From looking at the potential failure modes, we know we can insert a safing bolt on the remaining good IUA. This would prevent those failures, or most of those failures, from causing this TDA from inadvertently actuating and cutting the remaining good TUS cable. We won't know for sure about the failure until we can actually ... bring it back down to the ground for further analysis. But we believe by installing this bolt it can protect us from the most likely causes of that failure."
Installation of the safing bolt is considered a relative routine task. McArthur and Tokarev also will remove the severed cable from the mechanism to make sure it can't get snagged or otherwise hang up the transporter.
With the safing bolt in place, the spacewalkers will make their way back to the Pirs airlock module and retrieve a Russian space exposure experiment called Biorisk. The final task of the spacewalk is to float back to the aft end of the Zvezda command module for a detailed photo survey to document the condition of various external systems.
"Over the past few weeks, the crew has been using photos, briefings, video and computer software graphics to help study the mechanics of the (bolt safing) task as well as to visualize the entire sequence of the EVA," said Anna Jarvis, Expedition 12 lead spacewalk officer.
"It's been six months since the crew's last water run training and three months since their last spacewalk. This tends to be a factor in the crew's efficiency when they're outside. However, for increment crews, they have an advantage over shuttle-type crew members in that they're very well adapted to maneuvering themselves in a weightless environment. So we're anticipating a very successful and very productive EVA."