Brazing RB-SiC Used in Large Aperture Space Optical System

Abstract

Because of the sic material’s superior optical characteristic, machine characteristic and hot characteristic, it becomes currently the space big aperture reflector choose firstly1. For larger aperture sic mirror, it is not economical and safe to make the monolithic body directly2,3. The SiC mirror brazed assembly with several segments can solve these problems. In this paper, one Φ600 mm sic plane mirror as demonstration welded with 3 radial segments is roughly grinded to the required figure at first, then the mirror is finely grinded and polished by the technology of CCOS, the mirror figure error is less than 1/20λ (λ = 632.8nm) in RMS finally. The problems of the preferential removal near braze joint are solved. The methods of reducing the residual stress of mirror are discussed. At last, some measurements and experiments are carried on, and the results conclude that the brazed SiC mirror can meet the requirement of large aperture optical systems