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October 30, 2007

A Very Significant Anomaly

Today's scheduled EVA 3 promised to be one of the most demanding, even before an extra task was added. It lived up to expectations in that regard. However, the real excitement began after the spacewalkers had completed their tasks.

All major objectives of the 7 hour and 8 minute spacewalk were met. After discovering what appeared to be metal shavings inside the starboard Solar Alpha Rotary Joint (SARJ) during EVA 2, an inspection of the port SARJ was added to EVA 3. Spacewalker Scott Parazynski performed the inspection and gave the unit a clean bill of health, noting that the race ring was completely clean and that there was no evidence of any unwanted particles anywhere in the unit.

The major task of EVA 3 was the movement of the P6 truss to its permanent position next to the P5 truss. P6 was successfully moved and bolted in place, and electrically connected. A photovoltaic radiator was also deployed. At that point control transferred to Houston to initiate redeployment of the P6 2B and 4B solar arrays. After depoyment of both arrays was begun, control reverted to the crew inside the ISS. The deployment of the 2B array proceeded without a hitch. However, when the 4B array was almost completely deployed, the crew spotted an anomaly and aborted the deployment.

A tear in the 4B solar array about two and a half feet long was noticed. ISS Program Manager Mike Suffredini characterized the tear as a very significant anomaly. Deciding what to do about it is causing the folks in Houston to burn the midnight oil. Even if nothing is done, the 4B array will still be able to deliver 97% of its rated power. However, if the problem can be corrected before the shuttle leaves, it would be better than leaving things as they are. As a result, an extra flight day has been added to the schedule between EVA 4 and EVA 5. EVA 4 will include a detailed examination of the troublesome starboard SARJ.

After Spacewalker Douglas H. "Wheels" Wheelock returned from today's spacewalk, he noticed a hole in his right glove. Holes and cuts in EVA gloves are a concern, if they penetrate all the way through the glove material. That did not happen this time, but is worrysome nonetheless. Venting your spacesuit's air to space through a glove hole is probably something you would want to avoid if you were in Wheels' position. There are apparently a number of sharp edges on the exterior of the ISS that spacewalkers must avoid. Unfortunately, some of these sharp edges may be located on the hand-holds that are specifically designed for spacewalkers to grab. Micrometeoroid damage can convert a carefully designed hand-hold into a hazard. Now that the cut glove situation has cropped up more than once, I expect procedures may be changed to adjust. The gloves may also be in for an upgrade at some time in the future.

Allen G. Taylor
NSS Member

Posted by allen.taylor at October 30, 2007 02:53 AM



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