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Snapped Cable Damages Arecibo observatory radio telescope:

Grey Havoc

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dan_inbox

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If it is not somehow proofed against meteorites, what will be the life expectancy of a 1km-wide structure?
 

Orionblamblam

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If it is not somehow proofed against meteorites, what will be the life expectancy of a 1km-wide structure?

Probably a very long time. The structure would be akin to a wire mesh net; much of it's area would be open space that micrometeorites would simply pass through. The rest could be hit and torn to bits with little actual damage to the dishes functionality.
 

Hobbes

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that depends on the frequencies you want to operate at. At 1.42 GHz (21 cm, hydrogen wavelength) the mesh can be ~ 5x5 cm. Higher frequencies need a smaller mesh.
 

Orionblamblam

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that depends on the frequencies you want to operate at. At 1.42 GHz (21 cm, hydrogen wavelength) the mesh can be ~ 5x5 cm. Higher frequencies need a smaller mesh.
Sure. But the point remains: the surface of a radio dish is going to be many orders of magnitude less fussy than an optical scope. And the lightweight, relatively fragile nature of the material, whether it's a woven net, or sheets of foil, or etched foil, actually works in your favor when dealing with a lunar environment. On earth, wind can tear a really lightweight mesh. On the moon, you can blast it 24/7 with micometeors. Each one will punch a hole not much bigger than the impactor, with little effect on the surrounding reflector material. Punch a billion microscopic holes it it, it just won't matter. The total area taken out in a century of normal bombardment would be a vanishingly small fraction of the total and would possibly not even be noticed. Shoot, you could probably have spiderbots crawling around it non-stop repairing little dings, with a one-year rotation period.
 
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