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August 13, 2007

Summer Lessons in Space

So what did you do on your summer vacation? Mission Specialist and Teacher Barbara Morgan will surely have some stories to tell when school starts this fall. She launched into space with her six crewmates onboard the Shuttle Endeavour on Wednesday, August 8. Though the launch looked perfect, at least one wayward piece of foam managed to impact the fragile thermal tiles and gouge out a hole.

Perhaps one of the lessons that Barbara will share with students is how important it is to treat small problems seriously. The Space Shuttle Columbia was lost because foam falling off during launch was not considered a serious problem. Now there are cameras watching the launch from multiple angles. There’s a camera on the tank. The rendezvous with the space station includes a pitch maneuver so the belly can be carefully photographed. The shuttle arm is used to check any suspicious areas. Programs and history data and sample materials are ready for analysis and testing on the ground. Repair kits and procedures and astronauts trained for spacewalks are ready if the need arises.

On this mission, STS-118, photos revealed five damaged areas.

So Sunday, August 12, Barbara and fellow astronaut Tracy Caldwell, swung the shuttle arm around for a closer look at the damage. They used a camera and also a laser that precisely mapped the hills and valleys of the biggest gouge. Engineers will use this data to carve out the same shape in tiles on the ground. Then they will blast them with a torch to simulate entry heating, watching for burn-through to the shuttle’s aluminum skin underneath. The crater is about 1.5 inches deep, the thickness of the tile, so there is cause for concern. Depending what they find, they may recommend various repair options or decide to just leave the damaged tile as is.

On the last shuttle flight, the astronauts repaired a thermal blanket that had come loose during launch. That particular kind of damage was not anticipated, and still the crew was able to fix it after only one day of preparation. The STS-118 crew is already trained to repair the kind of damage shown in today’s inspection. The question is whether or not a spacewalk is really necessary. It may be that the hole, though deep, is not large enough or in such a critical location to be worth fixing. It was noted in the press conference Sunday that shuttles have survived entry with larger holes—on STS-1, they landed with whole tiles missing!

But lessons have been learned. Hard lessons. So, NASA is not going to assume that this gouge is not serious until the data proves it is not serious.

Also, the location on the external tank that produced the foam was not considered to be an area that would cause risk to the shuttle. Apparently, this piece of foam ricocheted off a strut before impacting the belly. Managers are now considering whether or not they have to redo the existing tanks, replacing some aluminum with titanium that will not form ice and cause foam to separate. Analyses must be done to determine if this is necessary and what impact it may have on the launch schedule.

Meanwhile the other business of STS-118 continues. The first spacewalk, completed on Saturday by Rick Mastracchio and Dave Williams, smoothly attached the new piece to the end of the starboard truss. Nicknamed “Stubby” by the crew, it will separate the two sets of solar arrays on that side. More work is planned “outside” for Monday.

Thanks to the work of the previous shuttle crew hooking up the new power system, this shuttle was given the go to extend their flight to 14 days. The shuttle uses fuel cells, combining hydrogen and oxygen to make electrical power and water. The shuttle can only carry so many tanks of hydrogen and oxygen, limiting its stay time in orbit. The new space station system allows the shuttle to draw electrical power from the station’s solar arrays. This is an exciting new capability. Not only does it allow shuttle missions to stay longer, it means that future space vehicles may not have to carry as much hydrogen and oxygen to orbit.

The undocking from the station is now scheduled for August 20 with a landing on Wednesday, August 22. I’m leaving soon on my own summer travels, but hope to catch some of the spacewalks and the landing on television or the Internet. I look forward to hearing all about Barbara’s summer adventure in space when she gets back. I’ll bet she has some exciting new lessons to teach us all.

Marianne Dyson

Posted by m_dyson at August 13, 2007 01:55 AM



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