RE: ATM Has anyone worked with membrane mirrors?

[astillma@nit.AirTouch.COM (Anthony Stillman)]

>Do they produce a parabolic shape or spherical?

It depends on the eleastic characteristics of the membrane.  Assuming Hooke's law
 is in force (for mild streching a good guess) and the pressure differential is
 uniform as is the membrane, the curve generated could best be described as a
 cantinary of revolution (a catinoide ?).  This is amazingly close to a
 parabalode, but it is not and for large mirrors correction is needed.  This is
 why I find the approach outlined in Unusual Telescopes so intreging.  Here
 using an electic field between the membrane and rings below on a substrait the
 figure can be adjusted.

There is nothing here that says the intervening material has to be air.  I suspect
 a number of dielectic compounds could be used. Oil, airojell, plastic, this could
 even be allowed to set up, a slow cure epoxy mirror all ready for use.


Anthony