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Spacewalkers to work as plumbers outside the station BY WILLIAM HARWOOD STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION Posted: February 13, 2010 
Astronauts Robert Behnken and Nicholas Patrick prepared for a planned six-and-a-half-hour spacewalk Saturday to hook up ammonia coolant lines between the new Tranquility module and the International Space Station.
The primary objective of the crew's second spacewalk is the connection of ammonia coolant loops to carry away the heat generated by Tranquility's electrical systems. Two independent coolant loops will be connected but only one of them - loop A - will be activated, allowing engineers to begin powering up the new module. The spacewalk was scheduled to begin around 9:09 p.m. EST. For identification, Behnken, call sign EV-1, will be wearing a suit with red stripes around the legs. Patrick, EV-2, will be wearing an unmarked suit. This will be the 139th spacewalk devoted to station assembly since construction began in 1998, the second of three planned by Behnken and Patrick and the third so far this year. Total station EVA assembly time stood at 861 hours and 34 minutes going into Saturday's excursion. The Tranquility module, also known as node 3, was attached to the left side of the station's central Unity module during the crew's first spacewalk overnight Thursday. The astronauts worked overnight Friday to make internal connections between the new module and the station and to prepare a multi-window cupola attached to the far end of Tranquility for relocation to the module's Earth-facing port overnight Sunday. But the crew ran into problems installing a protective cover on the outboard side of the Tranquility hatch where the cupola is currently attached. Engineers are troubleshooting an interference issue that is preventing the cover from going into place. Plans to depressurize the cupola in preparation for its upcoming move were delayed. Station commander Jeffrey Williams reported Saturday that a closer inspection indicated removal of a few bolts would eliminate the interference. Photos were downlinked to engineers in Houston while Behnken and Patrick pressed ahead with their spacewalk preparations. "The major activities, of course, are installing the ammonia lines and wrapping them in protective insulation," said station Flight Director Bob Dempsey. "This is going to be the major portion, the first half of the EVA. "All four ammonia jumper lines will be installed, but only two of them, what we call the A loop, will be integrated into the external thermal control system. At that point, the ground will have already prepared the node 3 by activating some of the basic computer and power systems. Once we have that thermal control system activated, we will then complete the activation of the module. At that point, at the end of the EVA, we'll have one leg of our redundant system fully operational. "The remainder of the EVA will be preparing some gap spanners, which the crew uses for (moving around the module's exterior), putting some handrails in place, putting in some sockets that will be used for foot restraints down the road if we ever need it, general outfitting of the module. They will also be preparing the node 3 nadir port, the common berthing mechanism, by removing some launch locks so we can open the petals we'll use to berth the cupola." NASA originally planned to attach Tranquility to the Unity module's Earth-facing port, but engineers decided to move it to the left side of the module to improve visibility for robot arm operators and to provide more clearance for Soyuz spacecraft docking at a nearby Russian port. But connectors needed to circulate ammonia coolant to and from Tranquility were not correctly positioned, or "clocked," for Tranquility to be attached to Unity's left-side port. Custom 16-foot extension hoses were ordered, but problems during recent pressure tests forced NASA to develop an alternative approach. NASA managers ultimately decided to connect shorter flight-qualified hoses to solve the problem while improvements were ordered to bring the longer hoses up to flight standards as a backup. For redundancy, the space station has two independent cooling loops and during Saturday's spacewalk, Behnken and Patrick plan to connect the supply and return lines for both loops. But only loop A will be pressurized. Loop B will be pressurized during a third spacewalk overnight Tuesday. Saturday's flight plan calls for Behnken and Patrick to unfold a large sheet of multi-layer insulation and tether it in place. Then, the coolant lines will be laid down and the insulation wrapped around them. "That's the biggest single challenge in all three of the EVAs, is getting the ammonia lines right," said Patrick. "Because there are four of them, and then there's this huge piece of insulation that we call MLI, for multi-layer insulation, it's about 20 feet long but it looks like it's a hundred feet long, shaped like a Y. "It comes out of the bag very carefully and deliberately and we lay that down along the path of the ammonia jumpers. We put that MLI insulation behind some tethers that hold it in the right place and then, one at a time, we take the ammonia jumpers out of their bag and connect them to the lab and the new node 3 and open the valves." While no one expects any leaks, the astronauts will be prepared for possible decontamination procedures if any problems are encountered. "When we first open up the valve and allow the ammonia to flow, that'll be our first indication if there's any leaking," Dempsey said before launch. "If there's something that happens at that point, there's not really any automated computer response. We will shut down the lines, have the crew take some sort of response, which may be to close the valve or something like that. "If you didn't do anything with a leak, you could drain a large quantity of ammonia," he said. "However, we do have a number of valves at various places, mainly right on both sides where we will open the valves and connect them, that we could shut." Here is an updated timeline of today's activity (in EST and mission elapsed time; includes revision F of the NASA television schedule): EST........DD...HH...MM...EVENT 02/13 04:14 PM...05...12...00...Crew wakeup 04:54 PM...05...12...40...EVA-1: Airlock repress/hygiene break 05:39 PM...05...13...25...EVA-1: Airlock depress to 10.2 psi 07:34 PM...05...15...20...EVA-2: Spacesuit purge 07:39 PM...05...15...25...Starboard deck IMV install 07:39 PM...05...15...25...Node 3 overhead IMV cap 07:49 PM...05...15...35...EVA-2: Spacesuit prebreathe 08:04 PM...05...15...50...Node 3 VAP cap removal 08:39 PM...05...16...25...Starboard overhead IMV install 08:39 PM...05...16...25...EVA-2: Crew lock depressurization 08:54 PM...05...16...40...Node 3 PPRV cap removal 09:09 PM...05...16...55...EVA-2: Spacesuits to battery power 09:14 PM...05...17...00...EVA-2: Airlock egress 09:39 PM...05...17...25...Node 3 ISP stowage transfer 09:49 PM...05...17...35...EVA-2: Node 3 MLI layout 10:09 PM...05...17...55...EVA-2: Ammonia jumper install 11:34 PM...05...19...20...EVA-2: Ammonia MLI install 02/14 12:19 AM...05...20...05...EVA-2: EV2: Open lab loop A QDs 12:19 AM...05...20...05...EVA-2: EV1: Open node 3 loop A QDs 12:39 AM...05...20...25...EVA-2: Ammonia MLI closure 12:54 AM...05...20...40...Node 3 ISP 1 removal 01:09 AM...05...20...55...EVA-2: EV2: Node 3 outfitting 01:19 AM...05...21...05...EVA-2: EV1: Node 3 outfitting 01:39 AM...05...21...25...Node 3 ISP 2 removal 02:24 AM...05...22...10...Starboard deck IMV checkout 02:54 AM...05...22...40...Starboard overhead IMV checkout 03:09 AM...05...22...55...EVA-2: Cleanup and ingress 03:39 AM...05...23...25...EVA-2: Airlock repressurization 03:54 AM...05...23...40...Node 3 CDC troubleshooting 03:54 AM...05...23...40...Spacesuit servicing 05:30 AM...06...01...16...Mission status briefing on NTV 07:44 AM...06...03...30...ISS crew sleep begins 08:14 AM...06...04...00...STS crew sleep begins 09:00 AM...06...04...46...Daily highlights reel on NTV 01:30 PM...06...09...16...Flight director's update on NTV 04:14 PM...06...12...00...Crew wakeup
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MISSION INDEX |
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VIDEO:
STEP-BY-STEP PREVIEW OF SPACEWALK NO. 1 