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Proceedings Paper

Mechanical design of a completely open-foldable dome for EST
Author(s): Robert H. Hammerschlag; Johannes N. M. Kommers; Simon J. van Leverink; Felix C. M. Bettonvil; Simon Visser; Aswin P. L. Jägers; Guus Sliepen
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Paper Abstract

In the context of the EST design study for a 4m-class solar telescope and a study for large open-foldable domes of the Dutch Technology Foundation STW, a design is made for the 20 to 30m diameter range. Detailed designs are made for three specific diameter sizes: 23, 28 and 33m. Smaller-size open-foldable domes based on tensioned cloth and in use at the Dutch Open Telescope (7m) and the GREGOR (9m) have proven to be all-weather stable and very effective for good seeing conditions for solar telescopes. The cloth has shown no degradation over the past 14 (DOT) resp. 6 (GREGOR) years of experience and no permanent elongation with the frequent de-tensioning and tensioning during opening and closing. The application of cloth permits a dome design leaving, when opened, the telescope completely free without any structure over the telescope and no massive structures besides or under it. Basis for the new design is the available prestretched stable cloth, which is nowadays produced in much stronger qualities than used for DOT and GREGOR. The larger curvature radius requires larger tension in the cloth, but combination with stronger cloth fits for the upscaling. Calculations show that the steel construction geometries of the GREGOR dome can be upscaled with a few adjustments. Bearings and drives remain within normal sizes. Cost calculations show that open-foldable domes of this size are remarkably lower in price than closed domes. In addition, an interesting option is presented for a semi-transparent windshield of which the position can be adapted to the wind direction. This shield gives an effective wind protection of the region around the primary mirror without disturbing the wind flows above the shield and without stagnant air or big eddies behind it. It is storm safe and the costs are only a fraction of the open-foldable dome costs.

Paper Details

Date Published: 28 July 2010
PDF: 20 pages
Proc. SPIE 7733, Ground-based and Airborne Telescopes III, 77330J (28 July 2010); doi: 10.1117/12.857807
Show Author Affiliations
Robert H. Hammerschlag, Utrecht Univ. (Netherlands)
Johannes N. M. Kommers, Hankom Engineering (Netherlands)
Simon J. van Leverink, Machinefabriek P.M. Duyvis (Netherlands)
Felix C. M. Bettonvil, Utrecht Univ. (Netherlands)
Simon Visser, Poly-Ned BV (Netherlands)
Aswin P. L. Jägers, Utrecht Univ. (Netherlands)
Guus Sliepen, Utrecht Univ. (Netherlands)

Published in SPIE Proceedings Vol. 7733:
Ground-based and Airborne Telescopes III
Larry M. Stepp; Roberto Gilmozzi; Helen J. Hall, Editor(s)

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