Development of a 60K Thermal Storage Unit

Abstract

Thermal storage units (TSUs) with embedded phase change materials (PCMs) can improve the performance and reduce the weight of space-based IR sensor systems. This paper summarizes the findings of a Phillips Laboratory-sponsored SBIR program to develop TSU technology at an operational temperature of 60 K. During Phase I of this program, nitrogen trifluoride (NF3) was identified as a promising PCM, despite a small degree of single-phase supercooling. So far in Phase II, an improved design methodology was developed which divides the TSU into two volumes: a heat exchanger volume and a storage volume. This approach increases TSU energy storage capacity and thermal stability while reducing both weight and volume. Testing in Phase II has shown that an aluminum foam core suppresses NF3 supercooling and eliminates concerns over heat exchanger filling in microgravity. Current plans call for a 6000 J TSU to be tested on- orbit in a.Hitchhiker GAS Canister experiment on the STS in mid-1998. In this flight system, the TSU heat exchanger will have a beryllium shell for CTE compatibility with beryllium focal planes and an aluminum foam core. The TSU storage tank will be made of thin-walled titanium. A low pressure (P < 100 psi) system will be utilized to minimize safety concerns.