posted 10-30-2007 11:41 AM               

Re-deployment of the P6 solar arrays began well with the P6-2B wing unfurling without issue. The same was true for the 115-foot P6-4B until nearly the end of the deploy, when ISS Expedition 16 commander Peggy Whitson spotted a tear in the right array:

posted 10-30-2007 02:21 PM               

Looks like EVA 4 is going to be the "Mr. Goodwrench" flight with inspections of the ailing SARJ and more then likely a patch of the solar array tear. Crazy stuff!

posted 10-30-2007 03:38 PM               

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Originally posted by Jay Chladek:
Looks like EVA 4 is going to be the "Mr. Goodwrench" flight with inspections of the ailing SARJ and more then likely a patch of the solar array tear.

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The good news is that they don't believe the array's power lines were severed by the 2.5 foot long tear, as they are still seeing the power generation they would expect to see with an intact wing. It does appear however, that the outer hinge has come free from the panel, which is troublesome as it is through the weight-bearing hinge that the wing is pulled taught, which in turn is necessary for the array to be structurally stable for the solar alpha rotary joint (SARJ) to safely rotate and track the sun.

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Only solution I can think of would be RMS 2 with the OBSS in its grasp to allow a spacewalking astronaut to get a firm brace to make a Kapton tape repair.

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posted 10-30-2007 06:09 PM               

If RMS 2 can grapple OBSS and hold it stable enough, that would be the only effective way I can see putting someone out there to inspect and repair it unless they try retracting the array to a closer point. As ominous as that tear looks, I would be more worried about the potential ramifications of pulling it back, considering the challenge of folding it back the first time on a couple previous missions (without tears).

posted 10-31-2007 09:42 AM               

Station manager Michael Suffredini had previously said that the deployment of the arrays would take precedence, however there are only a few options for how spacewalkers might reach the P6-4B array and with those come trade-offs that could affect the remainder of the STS-120 mission.

There are reports that the chosen course of action may include using the orbiter's boom (OBSS) attached to the space station's robotic arm to reach the damaged array, but a final decision has yet to be reached.

posted 10-31-2007 09:55 AM               

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NASA and contractor engineers worked through the night assessing a variety of options for possible repairs to fix a ripped solar blanket on a partially extended space station array. Station program managers recommended early today, sources said, that NASA delay a fourth spacewalk from Thursday to Friday and devote the excursion to solar array repair work.

Under that scenario, the astronauts would forego any immediate inspection of a contaminated solar array rotary joint, deferring that work to a later mission, and delay a spacewalk by station commander Peggy Whitson and flight engineer Yuri Malenchenko until after the shuttle Discovery departs.

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posted 10-31-2007 01:59 PM               

I will have to check, but I think part of the reason why the first Solar Array was installed first in a vertical position relative to the station had to do with the Russians being unable to supply the planned solar array tower for the Russian segment. Although it does seem that the station was designed early on with the capability to put the array there.

Columbia's loss didn't help matters as that P6 array spent over three more years unfurled then originally planned. As I recall in the sequence, two of the next four missions right after STS-107 returned would have involved pretty much the same solar array assembly sequence we saw on STS-115, 116 and 117. If Columbia hadn't been lost, then these steps would have taken place within a year of the P6 array's original deployment.

posted 10-31-2007 02:57 PM               

There are two tears: a 2.5-foot tear (that can be seen in the photos above) and a second tear, about 1/3 in size, in the outboard bay. Controllers believe that the damage occurred after a guide wire became hard snagged in a grommet (a ring through which the guide wire passes).

STS-120 spacewalker Scott Parazysnki will anchor himself on one end of the OBSS, which itself will be grappled by the SSRMS from its middle post, to be positioned by arm operator Dan Tani to the site of the tears.

Meanwhile, Doug Wheelock will position himself at the base of the P6 truss, to assist with observing clearances for the arm.

Controllers are still working on the details of what Parazynski will do once at the array, but he will attempt the clear the snag. If that cannot be done, he may cut one or two of the guide wires to release the snag. He will then install load-bearing straps to allow the array to be fully extended without risk to further damaging the array.

As of now, Parazynski will not try to repair the tears themselves. If the array can be deployed and deemed structurally sound, then the ISS program is content with operating at 95% power generation (though the P6 array) for the remainder of the station's on-orbit life.

The hope is that Parazynski and Wheelock will be able to complete the work necessary during the mission's fourth spacewalk, presently scheduled for Friday. However, should they need more time, a fifth spacewalk could be made on Sunday, extending STS-120 by another day.

posted 10-31-2007 03:03 PM               

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Originally posted by Robert Pearlman:
One problem, though not unsurmountable, is that the OBSS grapple is not compatible with the SSRMS, thus its instrumentation (e.g. cameras) would not be powered if used in such a manner.

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posted 11-01-2007 06:46 PM               

Using strips of aluminum, a hole punch, bolt connector and 66 feet of wire, astronauts constructed solar array hinge stabilizers that should allow them to take the pressure off of the damaged hinges on the solar array.

The contraption will work similarly to a cufflink, with the wire fed through a hole on the solar array and the strip of aluminum supporting it from below.

Scott Parazynski will make the repair while suspended from a boom attached to the station's robotic arm. Doug Wheelock will assist from the station's truss. Stephanie Wilson and Dan Tani will be operating the the robotic arm from the work station inside the Destiny laboratory.

The following summary of the prepare was uplinked to the crews aboard the shuttle and ISS:

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Summary Discussion of Blanket Repair

One of the solar array blanket Grommets has become snagged on the guide wire. This has caused a bunch of the panels to be pushed out ahead of this snag. When no more panels were in the box to be pulled out, the tension in the cable pulled on that grommet and ripped the piano hinge of the blanket between two panels. Best case, if we could clear that snag point, the bunched up panels (grommets) above/beyond the snag would slide down the guide wire towards the base and unload the guide wire. We suspect that whatever caused the snag at that one grommet may continue to snag other grommets. We really don't know if the problem is with a cut or bent grommet or a kink or fray in the guide wire. As the array deploys, this bad spot continues to extend and will eventually move out of our reach with a crewman on the boom. Our first move will be to try and clear the snag and evaluate how the cable behaves with the next grommets.

In addition to taking care of this snag, we also have to repair the torn blanket hinge. We have developed these splints (here to known as cuff links) of stiff wire that can be installed into guide pin holes to position that blanket flap back to a normal position. Each end has a toggle like a cuff link that can be inserted into the hole. It should toggle automatically so it won't come out. The snag has to be released first so the torn flap can be repaired before that part of the array deploys out beyond our reach. In the end, we may need 3-5 of these installed to repair the blanket.

If we could get 100% confident that it would not snag again, we could continue deploy. If it is going to snag again, we need to get that out of the system before it gets out of our reach. It seems unlikely we will have an identifiably bad grommet that we could cut out (not an easy thing to do). It also seems unlikely we will be able to get 100% confident the cable will not snag again.

We will try first to tease the cable snag point (fray or kink) through the 10-15grommets we know it still has to pass through to get to full deployment. We need you to pull on the blankets so the bunched up panels outboard of the snag are all flat and fully deployed on the final side of the snag where they are supposed to be in the final configuration

If the above will not work, that will lead us to cutting the cable. We believe the cable is really there just to keep things aligned during retraction so the array can live without it in the final deployed configuration. The tension in the cable is only 1 pound. We are continuing to analyze this.

If we cut the cable, we will need to cut it both above and below the snag point (fray/kink). Cutting below the snag point (towards the base) should be done firstso the clean cable can retract back to the base into its reel. We need to control the speed of retraction. This could be accomplished with the TPS Scraper (other crewman needs needle nose pliers) at the base of the array where the cable goes into the box. Press the tool against it to act as a brake. This inboard reel housing completely encloses the reel. We don't care what the cable does in the reel housing area in the end. The worst it could do is bundle up in a mess and stop the retraction. This would leave cable below the snag captured in the grommets much like the cable above the snag. The cable outboard/above the snag point will remain a fixed length and should just remain captured in the grommets above the snag point. We want to cut it as close to the tip as we can to minimize its length.

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posted 11-01-2007 07:15 PM               

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Originally posted by Lunatiki:
Will it be aired live?

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posted 11-01-2007 08:01 PM               

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Originally posted by NavySpaceFan:
If they succeed, this will rival the saving of Skylab as the greatest feat of on orbit repair.

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Skylab was a bit more seat of the pants. But actually the Russians get the record for best save of a space station when the crew of Soyuz T-13 managed to successfully save the Salyut 7 space station. Granted there were no EVA repairs done, but they did manage to dock successfully by manual with a completely dead and slowly tumbling Salyut and spent the next few weeks bringing it back online and fully operational.

I have to wonder if Arthur Clarke got inspiration from that mission when he wrote about the salvage of the Spaceship Discovery in his book "2010: Odyssey 2".

posted 11-02-2007 05:46 AM               

How to build space station-saving cufflinks

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How exactly does one assemble a space station saving cufflink from spare parts? Very carefully, as appears to be the case in this, the seven-part instructions that were uplinked to the astronauts, complete with illustrations for key steps.

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posted 11-02-2007 07:22 AM               

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Originally posted by Jay Chladek:
Skylab was a bit more seat of the pants. But actually the Russians get the record for best save of a space station when the crew of Soyuz T-13 managed to successfully save the Salyut 7 space station.

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posted 11-03-2007 01:09 AM               

Once outside, Parazynski will anchor himself to the orbiter's boom (OBSS), which has already been grappled by the station's robotic arm (SSRMS). Stephanie Wilson and Dan Tani will control the arm to position Parazynski near where the P6-4B array was torn, as the following two images illustrate:

Once positioned, Parazynski will assess the condition of the array, providing the first up close inspection of the damage. If, as ground controllers believe, the tears were caused by a snagged guide wire, Parazynski, assisted by Wheelock stationed at the base of the P6 array, will try to clear the snag and if necessary, cut the guide wire free.

Parazynski will also install five hinge stabilizers, or "cufflinks", to allow the array to be fully extended without putting additional tension on the tears. The cufflinks will be installed as follows:

posted 11-03-2007 05:23 AM               

"Go out there and fix that thing for us," radioed ISS Expedition 16 commander Peggy Whitson to Parazynski at the start of the spacewalk.

posted 11-03-2007 05:47 AM               

STS-120 commander Pam Melroy reported getting a clearer look at the tear site, relaying to the spacewalkers that the snagged guide wire appears to be tangled, a "furball."

posted 11-03-2007 06:28 AM               

Only 20 degrees above the southern horizon here in Indiana, but I think I'll step outside a take a look anyway.