Naked Science Forum
Non Life Sciences => Technology => Topic started by: nighthawk on 11/12/2008 14:21:09
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...and how would efficiency be affected if it was different? I've read on wikipedia that the pressure is only 0.3% of atmospheric pressure, is this true, wouldn't that crush the glass?
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The pressure is inwards and a cylinder is a very strong shape ' in compression'.
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There is a lot of misconception about vacuum (or partial vacuum) being somehow an almost infinite force. Even if you could create a perfect vacuum in a container the maximum pressure (on the earth's surface) is only ever 1 atmosphere (about 14.7 lbs/sq in). Similarly, in a pressurised spacecraft this pressure is in an outward direction and it is only a little lower than this in a modern passenger aircraft at 35,000 feet. Aircraft are made quite strong (for other reasons) but spacecraft can be quite flimsy structures to keep weight down.
Compare this 1 atmosphere pressure to what a submarine has to withstand, which can be over 100 atmospheres and, for specially designed submersibles, much more. Even a diver at 10m depth will be doubling the pressure on himself.
As SC says, a cylinder is a strong structure even though the glass is quite thin.