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."

Comments

Re:Deadline

[DerekLyons]

Why is 2010 such a "hard" deadline? Was it not created solely by politicians who wanted to divert resources to go to Mars?

No, it was created by the CAIB subsequent to the loss of Columbia.
 
 

As such, can it not be moved just as easily as it was created?

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.
 
 

It is, after all, three years away. If we can't move deadlines that far out, isn't there a chance we're overplanning, and leaving ourselves completely vulnerable to unexpected circumstances, exactly like this solar panel issue?

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...

Re:Electrocution?

[rbarreira]

Did you read the article?

Flight controllers have already warned Parazynski not to touch the electricity-generating solar cells that cover virtually the entire wing. If the metal of a tool he was holding melted, it could burn a hole into his glove.

Re:Impossible to stop the solar panel from generat

[Boilermaker84]

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.

Re:NASA Neglecting Lock Out and Tag Out Procedure

[Anonymous Coward]

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.