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Daring spacewalk today to save station solar wing BY WILLIAM HARWOOD STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION Posted: November 3, 2007 Astronauts Scott Parazynski and Doug Wheelock are suiting up in the space station's Quest airlock module this morning for a high-stakes spacewalk to repair a mangled solar array. If the orbital surgery is successful, the partially deployed solar wing will be fully extended and NASA will be clear to press ahead with plans to launch a European research module in December. If the fix falls short, more repair work could be needed and the next shuttle flight likely would slip into next year. But NASA managers are optimistic Parazynski, a physician trained in emergency medicine and one of the agency's most experienced spacewalkers, will be able to clear a snarled guidewire and install cufflink-like suspenders around two rips in the blanket to strengthen it enough for full extension.
Parazynski and Wheelock are scheduled to begin the dramatic spacewalk around 6:30 a.m., but they got off to a fast start today and they could begin the excursion up to a half hour early. This will be the 96th spacewalk devoted to station assembly and maintenance since construction began in 1998, the 19th so far this year and the fourth for the Discovery astronauts. Parazynski, Wheelock and station astronaut Dan Tani have logged 19 hours and 55 minutes of spacewalk time so far during Discovery's flight. After leaving the Quest airlock on the right side of the station's central Unity module, Parazynski and Wheelock will make their way up onto the lab's main solar power truss, which runs right angle to the long axis formed by the station's pressurized modules. Parazynski will attach a foot restraint to a 50-foot boom carried by the station's robot arm and then lock his boots in place for a spectacular 45-minute ride to the damaged array. Wheelock, meanwhile, will make his way to the base of the P6-4B solar array on the far left end of the main power truss and provide verbal guidance cues for arm operators Stephanie Wilson and Tani, working inside the Destiny laboratory module. The P6-4B solar array is half a football field from the space station's pressurized modules. The robot arm alone cannot reach the damage site, even when positioned at a work site on the end of the power truss. But using the shuttle's heat shield inspection boom as an extension, the space crane can just barely get Parazynski into position. After reaching the damage site, Parazynski first will inspect the mangled section of the 4B solar blanket to determine what might be needed to release an apparently snarled guidewire believed to have ripped open two blanket panel hinges during deployment Tuesday. Because the solar array is generating electricity, Parazynski's tools and the exposed metal on his spacesuit were covered in non-conducting tape to minimize the risk of a shock. NASA managers said that risk was minimal, but the spacewalkers were cautioned not to touch any exposed wires or conducting surfaces. Before addressing the presumed snarl, Parazynski will attach a homemade clip, dubbed a cufflink, threading clasps on each end through reinforced holes above and below the rips in the blanket. That way, if the tension on the blanket changes because of work to free the snarl, it will not widen the tears that are already there. Five such cufflinks will be installed across the 15-foot width of the blanket before any attempt is made to complete its extension. If NASA is lucky, Parazynski will be able to simply move the guidewire to one side, freeing the snarl. If the tangle cannot be freed, he will cut the wire and Wheelock will use pliers at the base of the array to control its winding back onto a take-up reel. "He'll assess the damage, that's his first job, to figure out what is really wrong up there," station flight director Heather Rarick said late Friday. "He'll call down that assessment, then he'll probably be given a go to install the cufflinks, which will provide some stabilization for the solar array. And he'll do that in the middle of the solar array and that'll help prevent any further tears as he's working. "His next job is then to try to make sure the guide wire is released from its location. We think that's what's caught in the damaged area. So he'll either move it away if he can do it without requiring any cutting, otherwise he'll need to do some cutting. There's also a hinge pin that's sticking out that he'll need to cut and then he'll need to install four additional cufflinks to provide the final amounts of stabilization for the wing." The spacewalk is timelined to last up to six hours and 30 minutes. But Hassmann said if Parazynski doesn't run into any major problems, the actual repair work could be completed in as little as a half hour. The astronauts inside the space station will attempt to redeploy the repair panel as soon as Parazynski can be moved out of the way. Here is an updated timeline of today's activity (in EDT and mission elapsed time; includes revision M of the NASA television schedule, updated spacewalk timeline): EDT........DD...HH...MM...EVENT 11/03/07 01:38 AM...10...14...00...STS/ISS crew wakeup 02:13 AM...10...14...35...EVA-4: Airlock repress; hygiene break 03:23 AM...10...15...45...EVA-4: Airlock campout resumes 04:53 AM...10...17...15...EVA-4: Spacesuit purge 05:08 AM...10...17...30...EVA-4: Oxygen pre-breathe 05:13 AM...10...17...35...Shuttle boom (OBSS) handoff to station arm (SSRMS) 05:58 AM...10...18...20...EVA-4: Airlock depress 06:28 AM...10...18...50...EVA-4: Spacesuits to battery power 06:33 AM...10...18...55...EVA-4: Airlock egress 07:03 AM..................SSRMS/OBSS setup ..........................1. Move to P1 truss/bay 12; perform tether swap ..........................2. Install work site interface extension ..........................3. Install foot restraint on WIF extension ..........................4. Astronaut gets In foot restraint 07:33 AM..................SSRMS maneuver to P6-4B solar array wing ..........................1. Check OBSS stability prior to P1 departure ..........................2. Station arm moves astronaut to P6-4B SAW 08:33 AM..................Solar array troubleshooting ..........................1. Assess/report guide wire configuration ..........................2. Clear guide wires; cut if necessary ..........................3. Install hinge stabilization cufflinks 11:03 AM..................OBSS maneuver to egress point ..........................1. SSRMS moves OBSS back to P1 bay 12 for egress 11:33 AM..................Astronaut egress and OBSS cleanup ..........................1. Egress foot restraint; remove/stow OBSS hardware 12:03 PM..................EVA cleanup ..........................1. Stow WIF extender on ESP-2; stow tools ..........................2. Return to airlock 12:33 PM...11...00...55...EVA-4: Cleanup and airlock ingress 01:08 PM...11...01...30...EVA-4: Airlock repressurization 01:13 PM...11...01...35...SSRMS/OBSS handoff maneuver 01:18 PM...11...01...40...Spacesuit servicing 01:58 PM...11...02...20...SRMS grapples OBSS 02:13 PM...11...02...35...SSRMS releases OBSS 02:58 PM...11...03...20...SRMS maneuver 03:00 PM...11...03...22...Mission status briefing on NASA TV 03:38 PM...11...04...00...Crew choice downlink 05:38 PM...11...06...00...ISS crew sleep begins 06:08 PM...11...06...30...STS crew sleep begins 07:00 PM...11...07...22...Daily video highlights reel on NASA TV 10:00 PM...11...10...22...Flight director update on NASA TV The 17-ton P6 solar array truss segment was launched in 2000 to provide power during the initial stages of assembly. The lab's main power truss is now built and equipped with huge sets of solar panels on each end: starboard 4 (S4) on the right side and port 4 (P4) on the left. The outermost right side S6 arrays, scheduled for launch next fall, will be attached to a short spacer segment known as S5. On Tuesday, P6 was unbolted from its initial mounting point and moved to the far left end of the power truss and bolted to the P5 spacer segment. The first of its two solar array wings, known as P6-2B, extended a full 110 feet as required, but the crew aborted deployment of the 4B wing when one section of hinged blanket slats hung up, presumably due to a guide wire snag. Two seams between adjacent slats pulled open, resulting in separate tears, and the edges of several nearby slats were crumpled. The largest rip measured some two-and-a-half feet long. Eighty percent deployed, the P6-4B array can generate 97 percent of the electricity of a fully extended wing. But with a partially deployed panel, none of the arrays on the left side of the main power truss can be rotated as required to track the sun without risking additional damage. As a result, the station's left-side solar alpha rotary joint, or SARJ, is locked in place until the damage is fixed.
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