Ultra-Stable ALLVAR Alloy Strut Development for Space Telescopes

This NASA SBIR Phase II 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 NASArsquo;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. Bars with thermal stability approaching Zerodurrsquo;s have previously been made by joining ALLVAR Alloys to commercially available Titanium alloys, and the Phase I effort developed stabilization processes for improved dimensional stability. This Phase II project is designed to leverage the Phase I development to create an ultra-stable ALLVAR Alloy hexapod structure and compare its performance to Invar, a commonly used low CTE material. The Phase II project would run full scale pm level stability tests of both assemblies in an effort to quantify the ALLVAR Alloyrsquo;s performance as an ultra-stable strut.