[ATM] If it's in a supremely stiff cell, that does not twist,why would a thin mirror sag?

[dgood at aha.org (Good, Donald)]

I don't think there is any resistance to your logic.  The lack of agreement
occurs in the details when you try to define what is a "properly designed
supplemental support" and "suitable materials".  Add to that cost, weight
(portability), and ease of construction, then not only should you not expect
agreement, but there are many useful solutions to pick from, depending on
design goals.  

Also, ATM'ers have a tendency to lapse into discussions of ideal situations
(I know I do) and have to draw themselves back to reality from time to time.
But the desire to build that perfect machine is always a strong temptation.

Don


-----Original Message-----
From: artbianconi@blast.net [mailto:artbianconi@blast.net]
Sent: Friday, February 13, 2004 8:28 AM
To: atm@atmlist.net
Subject: [ATM] If it's in a supremely stiff cell, that does not twist,
why would a thin mirror sag?


Maybe I am dense.

Maybe I am stupid.

No matter how I try I cannot fathom why a thin mirror would not maintain its

parabolic surface if held by a uniformly planar cell made of of carbon
fiber.

If it be true that the sagging issue begins with using a thin mirror,
instead of a 
thick one and goes away to a major degree when the mirror is made thick 
again, then any properly designed supplimental support made from suitable 
materials, should restore the correct geometry and prevent the distortion.

There seems to be a great deal of resistance to this logic.

I don't understand.

Art Bianconi

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