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November 03, 2007

Anticipation and Preparation

Friday on the Internatonal Space Station has been a day of anticipation and preparation. As I write, spacewalkers Parazynski and Wheelock are in the Quest airlock, prebreathing pure oxygen prior to getting into their EVA spacesuits. Anticipation is high for what is probably the most hazardous EVA in history, and preparation has been done to the extent possible for an attempt to repair the torn solar array on the P6 truss. The exact nature of the problem is unknown, and thus what will be required to repair the damage is not well known either. Spacewalkers Parazynksi and Wheelock will attempt the repair, with Wheelock stationed at the base of the solar array and Parazynski attached to the OBSS on the end of the shuttle arm, held in the grasp of the station arm. The combined reach of the two arms along with Parazynski's own long reach will be enough to put the spacewalker in the vicinity of the two tears in the solar panel.

The major hazard stems from the fact that the solar array on the P6 truss is energized and producing electrical power. There is no way to turn it off before Parazynski starts the delicate operation of trying to repair the tears. There is definitely an electric shock hazard, but the crew has done everything possible to mitigate the hazard. They have covered all metal projections from Parazynski's spacesuit with insulating tape and have insulated his tools also. He may be called upon to cut one or more guide wires, however, and it is pretty hard to insulate the blades of a pair of wire cutters.

Probably the most hazardous aspect of the spacewalk is the fact that it is unanticipated. Up until now, every spacewalk ever attempted on the ISS has been practiced beforehand in the neutral bouyancy tank on Earth for many hours. The repair of the P6 solar array is uncharted territory. Parazynski will have to diagnose the problem on the spot, determine the best course of action, and then do it, all within the time constraints of the consumables in his spacesuit. Because of the hostility of the space environment, any EVA is risky. This one however, raises the risk to a new level. Success on this job will show that fifty years after the launch of Sputnik and 46 years after Alan Shepard became the first American in space, NASA still has the right stuff.

Allen Taylor
NSS member

The Zetetic Forum
Database Central

Posted by allen.taylor at November 3, 2007 03:01 AM



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