GammaPC - Gammascopes
Some of our most recent experiments have been with Mylar mirrors. Aluminized Mylar is 93% reflective, which is only 2% less reflective than aluminized (or silvered) glass mirrors.
Part 1 Mathcad Calculations
Here, we use a simple round band to stretch the material into a flat, round shape, which can then be modified into a catenary shape, which cannot be used for telescope making. However, if electric fields are used to modify the shape of the mirror, a parabolic or hyperbolic shape can be created, which can be used for telescope applications.
Part 2 Designing the TemplateThe cost of the material to make a one-meter mirror: about $2.00
Part 3 Making the TemplateThe cost to make a one-meter mirror out of glass: about $100,000.
Part 4 Making the Base Plate Mold
The cost of putting telescopes in space is astronomical (pun intended), but a lightweight telescope made of Mylar would cost a fraction of what it would cost to put a similarly-sized glass telescope in space.
Part 5Our experiments have shown that we can actually bend a stretched sheet of aluminized Mylar into whatever shape we like with electric fields. Controlling electric fields and their shape is in the thrust of this project. Very large electric fields (roughly 100kV) are required to do this.
Part 6While this is an excellent example of this use of Mylar in space exploration (in fact, Mylar was originally developed for use by NASA in early spaceflight), it can also be used on the ground by amateur and professional astronomers to replace the large and expensive telescopes we use now. To buy the die for a 20" telescope mirror (just the glass, then you have to grind it) costs around $15,000. The same amount of aluminized Mylar costs about 50 cents. The only things that remain to be worked on are the electronic circuits and adaptive controls for the electric bending fields.
This type of technology puts the price of professional astronomer-class telescopes within economical reach of the ordinary amateur astronomer. If aluminized Mylar can be made in large enough sheets, these types of telescopes could eventually rival the very large telescopes throughout the world in quality and speed. Normally, a sheet of aluminized Mylar can be purchased that is 50" wide, which limits the maximum size of a telescope mirror to that aperture. Now we can use aluminized Mylar for making something besides toy balloons. References: 1. Mylar Polyester Film, DuPont Teijin Films, Data Sheet. 2. Theory of Plates and Shells, S. Timoshenko, S. Woinowsky-Krieger, 2nd. Ed., McGraw-Hill Book Company, 1959. 3. Mechanics of Materials, Sixth Ed., James M. Gere, Thomson Learning, Inc., 2004 4. Large Deflection of a Circular Clamped Plate under Uniform Pressure, Wei-Zang Chien, Chinese Jour. Phys., vol. VII, no. 2, pp 102-113, 1947 5. A NonLinear Theory of Bending and Buckling of Thin Elestic Shallow Spherical Shells, A. Kaplan & Y. C. Fung, National Advisory Commitee for Aeronautics (NACA), Technical Note 3212, 1954 6. Experiments with Pneumatically-Formed Metalized Polyester Mirrors, Chapter 24, Bruce D. Holenstein, Richard J. Mitchell, Dylan R Holenstein, Kevin A Iott and Robert H. Koch, The Alt-Az Initiative: Telescope, Mirror, & Instrument Developments, 2010, Genet. 7. Stretched Membrane with electrostatic curvature (SMEC): A new technology for ultra-lightweight space telescopes, Roger Angel, James Burge, Keith Hege, Matthew Kenworthy and Neville Wolf, Steward Observatory, UA Tucson. 8. Basic Wavefront Aberration Theory for Optical Metrology, James C. Wyant and Katherine Creath, Applied Optics and Optical Engineering, Vol. XI, Academic Press, 1992. 9. Flat Membrane Mirrors for Space Telescopes, Brian Stamper, Roger Angel, James Burge and Neville Woolf 10. Large Deflections of Clamped Circular Plates Under Initial Tension and Transitions to Membrane Behavior, Mark Sheplak and John Dugunji, TBI Journal of Applied Mechanics.