1 September 1991 Method of making ultralight primary mirrors
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In this paper the fabrication of ultralight mirror segments is described. The mirrors are made from HTP (high thermal performance material), better known as a third generation derivative of the Space Shuttle heat shield tile. The HTP material has a density of only about 0.14 gms/cc and is made from tangled fibers of aluminum oxide and silicon dioxide sintered together as a non-isotropic material. HTP material is also stiff, and undergoes very small shrinkage and expansion due to thermal effects. When one side of an HTP surface is coated with a suitable glassy substance, such as fused silica, fine mirrors can be made. HTP material also outgasses quickly, thereby preventing annoying virtual leaks which can result in condensation of gaseous species onto optical surfaces. Experiments have shown that a one-centimeter-thick specimen of HTP material will outgas from one atmosphere pressure down to the ambient pressure at low earth orbit in eight minutes when the pumping rate is 200 liters/sec.
© (1991) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Richard R. Zito, Richard R. Zito, } "Method of making ultralight primary mirrors", Proc. SPIE 1494, Space Astronomical Telescopes and Instruments, (1 September 1991); doi: 10.1117/12.46746; https://doi.org/10.1117/12.46746

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