James Webb Space Telescope's mirror blanks have now been con

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Chris McMahan

Posted: Thu Feb 08, 2007 2:25 pm

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Nice story on the blanks for the new space telescope here:

http://www.physorg.com/news90084957.html

- Chris

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=ooO=(_)=Ooo=====================================
Chris McMahan | first_initiallastname@one.dot.net
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George

Posted: Fri Feb 09, 2007 3:51 am

Guest

"Chris McMahan" <first_initiallastname@one.dot.net> wrote in message
news:ufy9gv74o.fsf@one.dot.net...

Quote:

Great news. Hooefully, someone said a prayer over it that went something
like this:

"Oh Lord, please don't let me screw this up". Lol

George

William C. Keel

Posted: Fri Feb 09, 2007 10:19 am

Guest

George <george@yourservice.com> wrote:

Quote:

"Chris McMahan" <first_initiallastname@one.dot.net> wrote in message
news:ufy9gv74o.fsf@one.dot.net...

Nice story on the blanks for the new space telescope here:

http://www.physorg.com/news90084957.html

- Chris

--
(. .)
=ooO=(_)=Ooo=====================================
Chris McMahan | first_initiallastname@one.dot.net
=================================================

Great news. Hooefully, someone said a prayer over it that went something
like this:

"Oh Lord, please don't let me screw this up". Lol

They do worry about these things a lot more now. Subsets of the
JWST optics (I vaguely recall up to 6 segments at a time) can ber
tested (in a cryogenic environment) in the great
big vacuum tank in Huntsville that was built to test and calibrate
Chandra. Cost something like $110 million, money that NASA HQ and
Congress were more than happy to spend after the HST mirror fiasco.
(The Chandra project scientist has remarked on what an unwitting
favor HST did them, since they got nothing but complaints
in response to their earlier pleas for a proper calibration facility).
The tank has a 500-meter extension so that a suitable small-looking
X-ray source could be observed.

Some students and I had the chance to visit the JWST blanks as they
were being machined (Axsys is about two hours up the road). Beryllium
is nasty and tedious stuff to work with. They have 6 or 8 multiton
digital milling machines completely inside vacuum chambers - the
liquid lubricant behaves in interesting ways. Each black went in
weighting about 400 kg and came out more like 20 kg. The milling
removed everything that wasn't a 2mm curved front surface and
a triangular network of 4mm supporting vanes. The blanks are
a couple of million dollars each, but by melting down the powder
from the vacuum tanks, they get most of it back. The supporting
vanes were thickened to 4mm as the launch plan evolved to Ariane V
and the deployment plan went to a foldout triptych which sits
vertically in the booster. They don't even like to hear the phrase
"accordion fold".

Bill Keel

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