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Space Shuttle Atlantis Delayed Again
eldavojohn writes "An electrical short cause the space shuttle Atlantis to be delayed since a lightning strike to the pad and Tropical Storm Ernesto caused delays. From the article:
'Liftoff was only hours away Wednesday morning when engineers reported a short in one of three fuel cells that supplies electricity for all the on-board systems, including the crew compartment.' It also points out that 'The faulty cell is currently operational even with the short. But after the 2003 Columbia disaster, which killed all seven astronauts, NASA says it has adopted an aggressive, safety-conscious approach to launching.' It causes one to wonder whether pre-Columbia-disaster NASA would have just replaced the fuel cell on the fly without telling anyone — and whether or not that is an ethically sound choice."
It's complex system. You often see similar issues with modern jet aircraft. There are so many things than can degrade or fail that it is unusual for 100% of the systems to be working perfectly. You end up making a list of what systems must be working before takeoff. That's also why there are redundant systems. You don't want to be in a situation where you are one failure away from a catastrophe. You don't want to be running on a single fuel cell. With two fuel cells, you can lose one, abort the mission and safely return to Earth. With three fuel cells, you can lose one and safely continue the mission.
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The poster of the above comment is a friend of mine, aside from being a pre-space shuttle space program junkie and also a big fan of apollo 12, and he explains the above post as this (over IM):
I figured those of us who haven't spent weeks in the Air and Space museum, or read the audio transcripts from all available NASA flights, would want an explanation.
~Wx
sig?
Instead of speculating, ask or look it up. They began to move it back to the building before Ernesto, but reversed course because it would almost certainly mean that they'd miss their launch window. Missing a launch window has serious costs associated with it; the faster the shuttles launch, the cheaper payload delivered by the shuttle is because most of the shuttle costs are constant, not per-launch. As a consequence, it's often worth it to weather the numerous weaker Florida storms, even if it risks the shuttle getting struck by lightning.
Basically, it comes down to: if they get hit, they miss the launch window and have to repair the shuttle -- but that repair won't cost as much as the delay will, and to move the shuttle to safety would almost certainly cause the launch window to be missed.
Back during the Apollo days, we used to *launch* during thunderstorms. One craft was actually struck by lighting midlaunch (I mean, come on, you're in a metal craft venting a huge plume of partially ionized gas behind you) and nearly had to abort. We're not that crazy any more, though.
As for weather predictions, our weather predicting ability has gone up tremendously in the past decades, in case you hadn't noticed the standard "three day forecast" becoming a "ten day forecast." However, chaos theory causes fundamental limitations on weather prediction systems. The shuttle team simply cannot react quickly enough because of the size of the vehicle. Nor would they want to, as discussed above.
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