Astronauts suit up for third and final spacewalk
BY WILLIAM HARWOOD
STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION
Posted: February 15, 2008
Astronauts Rex Walheim and Stan Love are gearing up for a third and final spacewalk today, a planned six-and-a-half-hour excursion to mount a pair of science packages on the hull of the new Columbus research module and to move a faulty space station gyroscope to the shuttle Atlantis for return to Earth.
The spacewalk, the 104th devoted to station assembly and maintenance since construction began in 1998, is scheduled to start around 8:40 a.m. when Walheim and Love, floating in the Quest airlock module, switch their spacesuits to battery power.
"The three main goals are to bring the two exposed payloads that the Europeans want on the outside of Columbus and attach them to Columbus," Walheim said in a NASA interview. "Also, we're going to bring back a control moment gyro, or a CMG, that had failed earlier in the space station program. (An earlier crew) replaced it, so there's a new one that's working, but we have to take the failed one back home.
"Stan's going to have quite the (robot) arm rides taking these payloads back and forth, and I'm going to assist him."
If time is available at the end of the spacewalk, the astronauts plan to rub an improvised tool featuring a spacesuit glove wrapped around a socket wrench across a small impact crater seen earlier on an airlock handrail. The goal is to find out if rough edges around the tiny crater could be responsible for glove damage noted during recent spacewalks.
One other possible "get-ahead" task involves a quick inspection of the station's right side solar alpha rotary joint, or SARJ, one of two that rotate outboard solar arrays to track the sun. The starboard SARJ has been shut down since late last year because of excessive vibration and internal contamination. If time is available today, Love and Walheim will inspect and photograph an area of the 10-foot-wide bearing race ring where engineers have spotted what appears to be a small defect.
It's not clear whether the defect might be a tiny crater or the result of some sort of debris resting on the surface of the race ring.
Here is a timeline of today's activity (in EST and mission elapsed time; includes revision I of the NASA television schedule):
EST........DD...HH...MM...EVENT 02/15/08 03:45 AM...07...13...00...STS/ISS crew wakeup 04:20 AM...07...13...35...EVA-3: Airlock repress to 14.7 psi 05:15 AM...07...14...30...Flight director update on NASA TV 05:30 AM...07...14...45...EVA-3: Airlock campout preps 05:35 AM...07...14...50...Space station daily planning conference 06:00 AM...07...15...15...Columbus module activation continues 07:00 AM...07...16...15...EVA-3: Spacesuit purge 07:15 AM...07...16...30...EVA-3: Spacesuit oxygen pre-breathe 08:05 AM...07...17...20...EVA-3: Airlock depressurization 08:35 AM...07...17...50...EVA-3: Spacesuits to battery power (spacewalk begins) 08:40 AM...07...17...55...EVA-3: Airlock egress 08:55 AM...07...18...10...EVA-3: SOLAR transfer from shuttle to Columbus 11:10 AM...07...20...25...Crew meals begin 11:35 AM...07...20...50...EVA-3: Gyroscope transfer to shuttle 12:50 PM...07...22...05...EVA-3: EUTEF transfer from shuttle to Columbus 02:25 PM...07...23...40...EVA-3: Cleanup and ingress 03:05 PM...08...00...20...EVA-3: Airlock repressurization 03:15 PM...08...00...30...Spacesuit servicing 04:30 PM...08...01...45...Mission status briefing on NASA TV 06:15 PM...08...03...30...Station crew sleep begins 06:45 PM...08...04...00...Shuttle crew sleep begins 07:00 PM...08...04...15...Daily video highlights reel on NASA TV
"For EVA-3, I like to joke, I am the 'meat end effector:' I am the thing on the (robot) arm that grabs things," Love said in a NASA interview. "Rex and I will start at the airlock, we will make our way to the shuttle's payload bay, where the arm will be waiting for us, and it'll already have on it what we call the APFR - again, you are nothing at NASA without an acronym, articulating portable foot restraint - toe clip. It allows a person to stand and have a solid base for their feet somewhere, and there's a spot on the arm where you can put one of these things. That will be in place, I'll hop in there, and then we will start removing refrigerators, or refrigerator-sized objects.
"First will be SOLAR, which is a solar telescope that mounts on the outside of Columbus. It's like a little satellite ... but it gets its attitude control, its power and its data feed all through the space station, so it's a little satellite that mounts on the outside of space station. We will pick it up from the payload bay, there's one bolt that holds it in place, then riding the arm I will carry it up to Columbus. Once it's bolted in place - and driving that bolt connects all its power and data connections all at the same time - we'll back away."
The SOLAR instrument package will be mounted on the upper of two attachment platforms on the outboard bulkhead of the Columbus module. At that point, the station arm will move Love to an external storage platform near the Quest airlock so he and Walheim can move the faulty gyroscope back to Atlantis for return to Earth.
"The space station holds its attitude in space using big, heavy gyroscopes and over the history of station we've had two of these fail," Love said. "The STS-118 crew removed the CMG-3, the CMG of interest here, and put it on a platform for us; we're bringing it home. So we'll go over by the airlock, grab that CMG, unbolt it, the arm will swing me over to the shuttle payload bay and we'll plunk it down in the exact same slot that we pulled SOLAR out of because it's the same structural interface there."
The space station uses four 500-pound control moment gyros to change its orientation in space without having to fire rocket thrusters. The devices are critical to space station operations and NASA wants to get the failed unit back to Earth so engineers can figure out what went wrong.
"Stan will come underneath that stowage platform and we'll remove some of the insulation that's around it so he can grab onto some handrails. Then I'll do the bolt and release it and then he can take it off back to the payload bay. When he gets a ride to the payload bay, I'll go scurry down there, free-floating as we call it - basically just walk with my hands - and get down there and help him put it back on the space shuttlešs carrier so that we can bring it home."
With the CMG safely bolted down in the shuttle's cargo bay, "we'll move over to EuTEF (the European Technology Exposure Facility), which is an external exposure facility, basically, looking at how materials respond to being exposed to space for a long period of time; another little satellite that mounts on the outside of Columbus," Love said. "I'll pick it up, we'll unbolt it, we'll drag it up, riding the arm, up to Columbus and stick it on another External Payload Facility, bolt it in place, and then our EVA is done."
The EuTEF package will be mounted on Columbus' lower external attachment bracket.
"We have some cleanup work - we have to move the toe clip off the arm, we're not allowed to leave it there; we have some safety tethers that we had strung on previous EVAs, we have to clean all that up since it's the last EVA of the flight. If there's any extra time we may do extra tasks."