Magnesium bodies

Started Mar 26, 2012 | Discussions thread
Leonard Migliore
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Stiffness
In reply to Owen, Mar 27, 2012

One big difference between plastic and metal is stiffness. This is typically quantified by the material's elastic modulus. Magnesium, which is about 40% denser than polycarbonate, has an elastic modulus 16 times larger. So a magnesium structure that's the same weight as a polycarbonate structure will deflect 1/12 as much. This is good for stuff like optics that you would like to keep in one place.

As it happens, most metals have similar ratios of stiffness to weight. Oddly, titanium is on the low end of this scale. What you really want is beryllium, which is 6 times stiffer than magnesium and has about the same density. Of course, it's hideously expensive and toxic, but it would make a nice camera body; a lot of optical devices in orbit are made of beryllium for the reasons I've described.
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Leonard Migliore

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