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More Solar Panel Problems For ISS
rufey writes "This week there have been two pieces of bad news from the International Space Station. First was the discovery of metal shavings inside a problematic rotary joint used to keep one set of solar panels in the optimal position for power generation. At the close of a subsequent spacewalk, after it was relocated to its permanent location, the unfurling of the 4B solar panel resulted in it tearing in two places. A spacewalk is now planned for November 4th to attempt to fix the tear. The upcoming spacewalk is not without risks, including the remote possibility of electrocution since it is impossible to stop the solar panel from generating electricity during the repair attempt. NASA says the ripped wing needs to be fixed or the solar rotary joint problem solved before any more shuttles can fly to the space station and continue construction. With a hard deadline of 2010 for Shuttle retirement, NASA does not have much wiggle room in the schedule in order to finish ISS construction."
No, it was created by the CAIB subsequent to the loss of Columbia.
No, because the CAIB requires the vehicles be recertified to extend their lives beyond that date - a very expensive and difficult process.
That being said - another limit, currently, is contractural. NASA has only contracted for so many External Tanks, SRB refurbishments, etc... Unless Congress coughs up more money (and approves the delays in converting facilities to support Ares/Constellation - I.E. more money) it simply isn't going to happen.
NASA routinely plans from 3-5 years out, to a decade or more. This is made necessary by the fact that planetary launch windows, if missed, may not recur for two years (Mars) or two _centuries_ (Pluto). Also, the hardware takes from months to years to assemble, on top of months to years of design and review effort. Training for a flight takes months. The Shuttle also has to be overhauled so often, a process taking months, so you have to plan ahead to make time available for that. Etc... Etc...
The AACS key is NOT 0xF606EEFD628B1CA427BEA93A9CA9773F
The panel cannot withstand the stress of rotation while the tear exists. The spacewalk will repair the panel to the point where it can be fully extended. Once fully extended, the tension on the panel helps it withstand the stresses of rotation.
The damage to the joint affects the opposite panel.
The fact that the MMU hasn't existed for over 20 years? NASA discontinued the project as being too risky with little benefit.
brightness is irrelevant to whether someone happens to have the right synapses fire in the right order to solve a particular problem.
And that was my point. Just because someone is bright, doesn't mean they will automatically think of every solution to a particular problem. Intelligence is not a free pass to discovering stuff (though it helps a lot!).
In the case of this particular example, she had done several other things in an effort to solve the problem, any number of which were potentially viable solutions, but didn't happen to think of this particular solution.
In my experience, the solution to a particular problem can come from any number of sources, some of which aren't necessarily the expected or "sanctioned" sources. Just because someone is both intelligent and an expert in their field does *not* mean they will think of the little bit that makes for a better solution.
To swerve randomly back on topic: it is conceivable that the electrocution hazard occurs during a particularly simple portion of the repair portion that can be performed in just a few minutes. A little scheduling to ensure that this particular action occurs during ISS "night" would be a good idea, in that case. It is entirely possible that no one at NASA thought of this. It is also exceedingly unlikely that they *didn't* think of it, but it certainly makes sense for someone to speak and say "hey, maybe we should do that at night, just in case."
Sort of like (car analogy) going ahead and double-checking with the guys at the tire store "you got the lug nuts all torqued down, right?" because sometimes they forget. Yeah sure, it's their job to do that and they're the experts and no one who's not an expert should suggest it because surely they thought of that, right? But don't you feel like an idiot watching your wheel bounce down the road.
rambling...
man, I feel like mold.
If you read the article, in fact if you had merely completely read the summary, you would understand that solar panels can not be turned off. Even in the absence of direct sunlight (which only occurs for a maximum of 36 minutes each orbit) they will still develop some power due to reflected light. You would also have noted that electrocution is a "remote risk."
If the problem were anywhere downstream of the sequential shunt units, they could lockout/tagout (btw, there is no OSHA in space), but it's upstream.
This is not design negligence. It's a fundamental fact of photovoltaics.