WASHINGTON -Cosmonauts aboard the International Space Station are preparing to return homenext month aboard a Soyuz spacecraft, while Russian engineers believe they?ve isolatedthe glitch that sent the last two landings careening off-course, missionmanagers said Thursday.
Expedition17 station commander Sergei Volkov and flight engineer Oleg Kononenko are dueto land on Oct. 23 to end a six-month mission that includedspacewalk surgery on their Soyuz TMA-12 spacecraft to help engineersunderstand why one of five separation explosive bolts on similar vehicles failedto fire during the recent landings.
Volkov andKononenko removed the suspect bolt in a Julyspacewalk so it can be returned to Earth for analysis.
Stationastronauts aboard Soyuz craft last October and April reentered the Earth?satmosphere at a bumpy, steeper-than-normal angle because the failed explosivebolt kept their landing capsule attached to an adjoining module longer thanplanned. The glitch sent them on a steeper, so-called?ballistic landing? that subjected the astronauts to higher gravitationalforces and sent them hundreds of miles off-course.
Russianengineers believe electrical arcs triggered by ungrounded insulation near thebolt?s location on the Soyuz can cause the pyrotechnic device to fail, saidNASA space station program manager Mike Suffredini in a mission briefing. Thesparks stem from the electrical potential generated between the space station?sexpansive U.S. solar arrays and the surrounding environment.
?Where it?sfailed to separate each time, they?ve determined there?s been some arcing, ifyou will, or equalizing of voltage in this area,? Suffredini told reporters.?This, over time, has caused the pyros to be ineffective.?
With thesuspect bolt removed from Soyuz TMA-12, Russian engineers believe Volkov and Kononenkowill have a smoother ride. Similar bolts on future Soyuz are also beingreplaced, Suffredini said.
?Given thatcause, they believe they?ve made the steps necessary so that we won?texperience ballistic reentry for those reasons,? he added.
Suffrediniadded that while NASA engineers found it is possible that the Soyuz pyrotechnicbolts could be affected by sparks from the station?s surrounding environment,they believe a much higher electrical potential would be required to cause the arcingeffect.
WhileVolkov and Kononenko prepare for their return to Earth, their NASA crewmateGregory Chamitoff is looking forward to seeing some new faces. Chamitoff joinedthe two cosmonauts midway through their Expedition 17 mission in June and willstay aboard the station to join the incoming Expedition 18 commander MikeFincke, of NASA, and Russian flight engineer Yuri Lonchakov.
The SoyuzTMA-13 spacecraft carrying that new crew is slatedto launch Oct. 12 from the Central Asian spaceport of Baikonur Cosmodromein Kazakhstan.
Alsolaunching to the station with the Expedition 18 crew will be American spacetourist Richard Garriott, an American computer game developer who is paying $30million for a 10-day spaceflight. His mission, the sixth privately paid ticketto the space station, was arranged with Russia?s Federal Space Agency by theVirginia-based firm Space Adventures.
Garriott isthe son of retired NASAastronaut Owen Garriott, making him the first second-generation Americanastronaut when he launches into orbit next month. He has lined up a host ofscience experiments and educational outreach projects for the shortspaceflight, and will return to Earth with Volkov and Kononenko in late October.
Bycoincidence, Volkov is the son of famed Russian cosmonaut Alexander Volkov, andbecame the world?sfirst second-generation spaceflyer when he launched in April.
DuringExpedition 18, station astronauts plan to work alongside visiting NASA spaceshuttle crews to install a new bathroom, sleeping quarters and life supportequipment that will allow the orbital laboratory to double its crew size to sixpeople in 2009. Chamitoff is due to return to Earth in November during thefirst of those shuttle missions, with two other one-person crew swaps to followon subsequent flights.
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