Volker Seibert

Game-changing approaches to affordable advanced lightweight mirrors II: new cases analyzed for extreme ZERODUR lightweighting and relief from the classical polishing parameter constraint

Previously we established that the combination of new machining parameters for openbacked monolithic lightweighted ZERODUR® mirror substrates, coupled with new methods for optical finishing of aggressively lightweighted mirrors, have relieved classical mirror design constraints imposed upon 1.2m diameter lightweight mirrors. We demonstrate that openback mirror substrates now offer comparable mass, Eigenfrequency and substructure print-through performance to the sandwich-mirror architecture, but with considerably less manufacturing effort than for sandwich mirrors. Here we extend the analyses of the first paper from 1.2m diameter down to 0.6m in diameter and up to 2.4m diameter and 4m diameter mirrors.

Game-changing approaches to affordable advanced lightweight mirrors: Extreme Zerodur lightweighting and relief from the classical polishing parameter constraint

Recent game-changing technology greatly extends the design possibilities and range of applications for aggressively lightweighted open-back Zerodur® mirrors. We have compared several lightweighting design approaches under this new technology. Analytic comparisons are for 1.2m mirrors, all constrained to have a free-free first Eigenfrequency of 200 Hz. Figures of merit include resulting mass, thickness and relative cost. Much more aggressive masses are now available in open-back mirrors, competitive with the more expensive closed-back sandwich mirrors. These breakthroughs are relevant to spaceborne implementation of lightweight mirrors ranging from a few tenths of a meter in diameter to up to 4 meters in diameter.

ZERODUR iso-grid design of a 3 m class light weighted mirror blank for the E-ELT M5

The tip and tilt M5 mirror of the European Extremly Large Telescope (E-ELT) requires a demanding approach in light weighting. The approximately 3 m x 2.5 m elliptical plano mirror is specified to a weight of less than 500 kg with high Eigenfrequencies and low deformation under different inclination angles. In 2011 SCHOTT has presented a study to develop a design for the M5 mirror blank of the ESO E-ELT. The design presented was based on a radial square design to achieve the best compromise between performance and manufacturability. With the fabrication of a prototype section SCHOTT demonstrated its capability to manufacture the demanding features including pockets with 350 mm depth, thin walls and sloped pocket bottoms. Now 3 years later SCHOTT presents an iso-grid based design that is in accordance with the manufacturability progress that has been demonstrated in various ELZM (Extremely Lightweighted ZERODUR Mirrors) publications in the last two years. The achievements on the specified mechanical parameters are compared to the first approach from 2011. In this paper the results are presented and the performance parameters are discussed.

Design and fabrication of a 3m class light weighted mirror blank for the E-ELT M5

In the recent past, SCHOTT has demonstrated its ability to manufacture large light weighted ZERODUR® mirror blanks for telescope projects like the GREGOR solar-telescope, for example. In 2010, SCHOTT was commissioned with a study aimed at developing a design for the M5 mirror blank of the ESO E-ELT. The tip and tilt M5 mirror of the European Extremely Large Telescope (E-ELT) requires a demanding approach in light weighting. The approximately 3.1 m x 2.5 m elliptical plano mirror is specified to a weight of less than 500 kg with high Eigenfrequencies and low deformation under different inclination angles. The study was divided into two parts. The first part focused on coming up with an optimized light weighted design with respect to performance and processability with finite element modeling. In the second part of the study, a concept for the processing sequence including melting, cold-processing, acid etching and handling of the M5 blank was developed. By producing a prototype section, SCHOTT demonstrated its ability to manufacture the demanding features, including pockets 350 mm in depth, thin walls and sloped pocket bottoms. This paper outlines the results of the design work, processing concept and demonstrator fabrication.

Glass Products Under Mechanical and Thermal Loads

Airbag igniters are small assemblies consisting of a sealing component with specified electrical properties and an explosive. Robust igniters must guarantee the reliability of the electrical properties and of the explosive for many years. Thus, the components must not exhibit any form of corrosion and the assembly must be air-tight. Otherwise, the explosive could degrade by moisture, for example.