Ultra-Stable ALLVAR Alloy Development for Space Telescopes

This NASA SBIR Phase I proposal is in response to the need for Ultra-Stable Telescope Structures and is designed to evaluate ALLVAR Alloys for their potential as metering and support structures for optics that are critical to NASA’s future missions. Telescopes used for astrophysics, exoplanet, and planetary studies require picometer stability over several minutes to hours. Building large support structures with picometer level stability is a challenge with currently available materials due to their brittle nature in the case of Zerodur and ULE or their requirement to have tight thermal control in the case of SiC or carbon fiber composites. ALLVAR Alloys offer a new material solution for thermally stable structures. They exhibit negative thermal expansion and can compensate for the positive thermal expansion of other materials to stabilize a telescope. The ultimate goal of this work is to create an ultra-stable ALLVAR Alloy metering structure manufacturing process. Bars with low thermal expansion have previously been made by welding ALLVAR Alloys to commercially available Titanium alloys, but their dimensional stability over thermal fluctuations is above the pm stability limit. This Phase I project is designed to better understand the individual stability of the titanium and ALLVAR Alloys and to evaluate hydroxide bonding for mounting mirrors to ALLVAR in preparation for pm level stability tests. The Phase II project would run full scale pm level stability tests in an effort to evaluate the relaxation manufacturing steps and understand how welding the ALLVAR Alloy to titanium may affect the material’s stability.