Novel approach to supercritical helium flight cryostat support structures

Abstract

A unique system for structural support of optical flight cryostats has been designed, constructed, fully tested and flight qualified. The principal feature is a single epoxy fibreglass cylinder which serves both as a radiation shield cooled over its entire length and as an integral part of the internal structural support. The result is a high cryogen to package ratio, with simple and reliable mechanical joints and no additional adhesive bonds required in the structural load path. Additional advantages include quicker fabrication, low cryogen usage rates, and a rigid support (measured in excess of 100 Hz on all three principal axes). This Paper describes the technical approach, thermal and structural analysis used in the design of a 38 dm 3 flight system, as well as the results of the thermal and environmental testing for shock (in excess of 20g †), random vibration and cryogen hold time. The system was designed to meet ASME requirements while maintaining a high cryogen to cryostat weight ratio of approximately 1:5. In addition to maintaining the cold finger temperature below 9 K with an instrument heat load of approximately 1 2 W , providing gas cooling to the support structure and intercepting radiation heat inputs, the system provided 65 W of cooling as the exiting gas was warmed up from the cryostat exhaust temperature of 40 K to room temperature.