Technical Article on the James Webb Telescope

[Tuckerfan]

The making of the mirrors for the James Webb Telescope.

One of the most important components of the James Webb Space Telescope is its 6.5 meter mirror that is comprised of 18 beryllium segments. The mirror is the largest lightweight beryllium optic that has ever been made. Its segments were completed in March, 2007 by Axsys Technologies Inc. at its climate-controlled factory in Cullman, Alabama. Northrop Grumman Corp. is the prime contractor for James Webb Space Telescope.
Each mirror segment is about 1.5 meters across. Axsys used eight Mitsui Seiki USA Inc. ( www.mitsuiseiki.com) machining centers to produce the segments.
Mitsui Seiki supplied custom-built horizontal machining centers to produce the James Webb Space Telescope mirror segments. The machining centers combine a massive structure — the column weighs 11 tons, the bed is 20 tons — with the ability to position to within a few microns anywhere in the machining envelope.

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

[Spectre_of_Pithecanthropus]

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?

[Tuckerfan]

@Spectre of Pithecanthropus

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.

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.

[Tuckerfan]

@Spectre of Pithecanthropus

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

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.