Adaptive Deployable Thin Spherical Shell Reflectors

Abstract

This paper begins with a quick survey of potential space applications and a brief review of previous experiments on the shape control of a spherical shell reflector with a thin film of PVDF-TrFE. Next, the problem of thermal sensitivity is addressed numerically; it is found that, because of the large thermal expansion of the active material, the surface figure error generated by a linear thermal gradient on a unimorph reflector is considerable and its correction requires large control voltages. The surface figure accuracy can be greatly improved by a balanced design (i.e., adding a passive layer symmetrical to the PVDF-TrFE layer) and using a low CTE substrate. Finally, the paper considers a petal reflector; the unimorph design is even more sensitive than the full reflector to the thermal gradient, but the balanced design turns out to be better than the full reflector, both from the point of view of the surface figure error and the control voltages.