The present invention provides a thermal, and if desired, a radiation barrier to protect the exterior surface of a spacecraft. In particular, the present invention protects the polymeric materials of construction utilized in inflatable and expandable spacecraft from the deleterious effects of both thermal and radiation aging. The protective barrier is formed from a tube or tubes through which a fluid circulates. The tube segment substantially enclose the spacecraft, and in particular, the critical layers that are desired to be protected. This protective barrier provides a thermal heat sink, temperature equalization, and a waste heat rejection system, that can moderate the temperature extremes encountered by spacecraft. In addition, dependent on the fluid selected, substantial radiation shielding can be provided that can protect the entire spacecraft.