Abstract: Apparatus for providing a simulated space environment for the testing of articles under low temperature conditions comprising a liquid nitrogen head tank, liquid nitrogen subcooler pumps, a liquid nitrogen subcooler coil, a liquid nitrogen head tank makeup pumps, a low pressure liquid nitrogen storage tank, a high pressure liquid nitrogen storage tank, a liquid nitrogen transfer pump, a vacuum chamber and thermal simulation heat exchanger shrouds contained within the vacuum chamber. Appropriate internal and external piping connects these components so that the apparatus can be operated both in a subcooled pressurized closed loop system as well as in a gravity convection system. While liquid nitrogen in this apparatus will produce a stable uniform temperature of -297.degree. F. within the shroud containing the article to be tested, other liquids with similar low temperature characteristics may be used.

Abstract: A seal joining a vacuum vessel head to a shell includes a flange on the head and a flange on the shell with a seal ring interposed therebetween. Spacers transfer the weight of the head and the vacuum load in the vessel to the seal ring. A sealing skirt attaches to the head flange and to the seal ring.