Technical Article on the James Webb Telescope

The making of the mirrors for the James Webb Telescope.

I’m surprised that they’re using beryllium, as that’s some nasty stuff.

I assume you are referring to the hazards of ingestion by humans. Given that spacecraft are usually prepared in ultraclean facilities and manipulated by remotely controlled tools, or by people in protective suits, I don’t see the problem.

Beryllium is the lightest reasonably stable metal known; perfect for a space telescope.

OTOH I don’t know how reflective it is. Will there be a layer of silver electroplated on?

Yeah, but there’s the problem of disposing of all the chips, etc. That stuff has to be properly handled as well, which is expensive.

I don’t know if they’d coat it with silver or not. May not have to, if they can polish the metal bright enough.

In checking with the machinist board I frequent, it seems that you can polish it to a high degree of reflectivity, so they won’t need to silver plate it.