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Spacewalk underway to work on the Soyuz spacecraft BY WILLIAM HARWOOD STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION Posted: July 10, 2008 Space station commander Sergei Volkov and Oleg Kononenko depressurized the Pirs airlock module today and opened an outer hatch at 2:48 p.m. to officially kick off a dramatic six-hour spacewalk. The primary goals of the excursion are to unlock one of five connectors holding two Soyuz spacecraft modules together and to remove an explosive bolt to help Russian engineers figure out what might have caused back-to-back module separation problems during the two most recent Soyuz landings. Removing critical hardware from a Soyuz spacecraft - the space station crew's lifeboat - is unprecedented, as is handling an explosive bolt. The pyrotechnic device has an explosive potential roughly equivalent to an M-80 firework. But Vladimir Solovyev, chief Russian flight director, told Volkov and Kononenko on Wednesday that extensive testing showed the device was safe to handle. "It cannot fire so you should not be concerned at all," Solovyev said. "It also withstands shock up to 100 Gs and does not fire, it's been tested. So if you really wanted to fire (it), you would have to really try to knock it with a hammer. But even then, it's not possible for it to fire." The cosmonauts will guard against any static charge build up and the pyrobolt will be inserted into a blast-proof steel sleeve. It then will be brought back into the space station for eventual return to Earth. This is the 113th spacewalk devoted to station assembly and maintenance since construction began in December 1998, the 14th so far this year and the first for Expedition 17 commander Volkov, 35, and flight engineer Kononenko, 44. Going into today's excursion, space station EVA time stood at 706 hours and 36 minutes. The Soyuz TMA-12 spacecraft docked to the Pirs module will be used by Volkov, Kononenko and a space tourist to return to Earth in late October. Because it currently is docked to Pirs, and because Pirs must be depressurized for today's spacewalk, NASA flight engineer Gregory Chamitoff is sitting out the spacewalk inside the Soyuz because of the remote possibility of a problem repressurizing the Pirs module later today. In that case, Chamitoff would not be able to reach the Soyuz in an emergency. This way, if a repressurization problem occurs, Volkov and Kononenko would join Chamitoff in the TMA-12 spacecraft and they would fly it to another docking port on Friday. The Soyuz is made up of three connected sections, but only one of them - the central descent module - is designed to withstand the rigors of atmospheric entry and carry a crew back to Earth. The three modules separate, using explosive bolts, just before re-entry begins. The modules can safely separate if two of the five connectors fail to work, although such failures result in steep, rougher-than-usual ballistic re-entries. "There are five locking bolts on the Soyuz that hold the instrument (and propulsion) module to the descent module," U.S. space station Flight Director Bob Dempsey said Tuesday. "In a normal re-entry, these locks are released by pyrobolts, which explode and release the locks and then the instrument module is separated and the descent module re-enters the atmosphere. We'll be inspecting one of these locking assemblies, No. 5, and we'll be removing one of the two pyrobolts that are associated with that locking mechanism." Each of the five connectors holding the propulsion module to the descent module feature two redundant pyrobolts. Engineers do not know of any problems that might affect the normal separation of the Soyuz TMA-12 crew module, but they don't yet know what caused separation problems last May 19 and Oct. 21. In both cases, the upper orbital module separated from the crew module normally just before atmospheric entry, but the lower propulsion/instrumentation module hung up. Both spacecraft then flew steeper, so-called ballistic trajectories that subjected the crews to extreme buffeting until the lower modules broke free due to aerodynamic stress. Volkov, wearing a spacesuit with red stripes, is using the call sign EV-1. Kononenko, wearing a suit with blue stripes, is EV-2. With his feet anchored to me end of a telescoping boom, Kononenko will be positioned over the Soyuz worksite and use a knife to cut through multi-layer insulation over the descent module/propulsion module interface. Volkov will make his way down the boom and join Kononenko for a detailed photo survey. Volkov then will use a wrench to disconnect one of the two pyrobolts at the connector in question. The bolt will be inserted into a blast-proof steel sleeve for return to the station. "Our desire is straight forward," Solovyev told Volkov and Kononenko on Wednesday. "What we expect from you during this EVA is to take out one pyrobolt, thereby breaking this mechanical contact. Less of a priority is to return this pyrobolt. We would like to, of course, see what you notice before you start cutting the MLI (multi-layer insulation) and after you dig inside the niche through the cutout you make in the MLI. "The important thing here to remember is that we would like to see as many pictures as possible," he said. "We have been holding meetings after meetings with different commissions to discuss the situation with the pyrobolts and what's happening with them. This is what we decided to do because we think we have exhausted all of the studies that exist on the ground. So we need to figure out what to do with this series of Soyuz vehicles. "So, like I said, we need to break this mechanical contact, which brought us into the ballistic descent twice before. So again, make sure you take as many pictures as possible because as you know, we sometimes have video, sometimes we don't, sometimes we don't see very well what you're seeing. So we would like to look at that pyrobolt as well as possible, especially when you're inside the niche." To provide better video coverage of the work, Kononenko's spacesuit is equipped with a NASA helmet cam video system. Another camera has been mounted in a window in the Zvezda command module that looks straight down on the work site. Video from that camera, Kononenko's helmet cam and cameras mounted on the space station's solar power truss will be sent back to Earth through NASA's satellite relay system.
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VIDEO:
EXPEDITION 17 SPACEWALK PREVIEW BRIEFING 