Abstract: Apparatus for holding a space vehicle at a constant temperature including llular sandwich on the outer surface of the space vehicle, the cellular sandwich having two outer layers and translucent cells between the two outer layers, the translucent cells containing phase change material, the outer layer that is more distant from the space vehicle able to transmit sunlight to the translucent cells and able to transmit radiation away from the translucent cells, the phase change material absorbing sunlight and radiating energy to maintain the space vehicle at a constant temperature in sunlight and darkness.

Abstract: A composite structure having predetermined temperature/time profiles is made by combining in chemically separate yet intimate thermal relation a plurality of phase change mediums which change phase at differing temperatures in the overall range of the predetermined temperature/time profiles. Each of the phase change mediums changes phase at a different temperature in sequence for defining the thermal storage capacity of the structure and generally approximating the predetermined temperature/time profiles throughout the overall temperature range.