Optical mirrors for aerospace applications are heavy constructions as a result of the high density of the materials (metal or ceramics). The goal of this project was to utilize CFRP and a new coating technique in order to produce optical mirrors with a reduction in mass of at least 80 percent compared to conventional systems. The challenge was the stability of the system under fluctuating temperatures.
The basis was the metallization process for CFRP developed at the IST. For this purpose, flat samples were chemically pickled using a special process and then electroplated with nickel. The reason for this was special requirements concerning the quality of the adhesion between the layer and the component. The nickel surface was turned to mirror quality at the Fraunhofer IPT by means of the UPD process (ultra-precise drilling). In the next step, parabolic mirrors with a diameter of approx. 30 cm were manufactured (INVENT) and nickel-plated (Fraunhofer IST). Prior to the UPD process, the mirrors were measured in order to exclude deformations due to internal stresses.
The result was a metallized CFRP parabolic mirror with significant weight savings. The stability under fluctuating temperatures could not be demonstrated; there is, however, a great potential for applications at constant temperature, e. g. earthbound mirrors for astronomical purposes which are movable and which operate at constant low temperatures.