Best Laid Plans of Mice and Men
OK, call me a sourpuss, but how were they really expecting this to go right? Of course I am refering to the retraction of one of the big solar panels on ISS. This particular panel has been extended for something like six years, and my personal opinion is that it's a miracle the thing managed to fold up at all. The panels consist of photovoltaic wafers bonded onto what we call a flex circuit (kapton substrate with embedded circuit traces) in my industry -- the material is thin, translucent, characteristically yellow to honey brown in color, pretty tough -- although prone to cracking if folded too sharply or too much.
One of the big issues with flex circuits is the tendency to break the embedded copper circuit traces within the kapton. If one of these breaks, your panel is pretty much done for, and this could become an issue with multiple extensions and retractions of the solar array.
Why I bring this up at all, and why I titled this blog after the Robert Burns quote, is because it seems to me that if there had been better planning on the initial solar array placement, then this retraction mess could have been avoided all-together. For instance, if the initial array had been installed rotated 90 degrees to it's current orientation, then it wouldn't have interfered with the new array installed during the previous shuttle mission one iota, and we'ld be about one shuttle mission and about $500 million further along.
There's probably something I'm missing. So anyone who knows what the ISS designers were thinking, please give a shout out.
One last thing. Who the heck pumps a hundred amps through a sheet of plastic??