DESIGN AND ANALYSIS OF A NOVEL, ULTRA-LIGHT, CRYOGENIC DEWAR FOR BALLOON-BORNE OBSERVATORIES

Abstract

The deployment of cryogenic Dewars aboard high-altitude balloons is critical to astronomical observation at submillimeter wavelengths. Balloon-borne, cryogenically cooled telescopes are limited in size by weight restrictions of the balloons, which is dominated by the Dewars. This thesis presents a portion of the multi-phase BOBCAT project which reduces Dewar weight with the use of thin-walled designs and a novel multi-layer insulation (MLI) system. The BOBCAT-1 mission used conventional Dewar technology to demonstrate cryogen transfer at float altitude and establish baseline thermal performance of balloon-borne Dewars. Design and assembly of the BOBCAT-2 ultra-light Dewar showed successful fabrication of the thin-walled vessel and novel MLI system. Thermal modelling predicts that the BOBCAT-2 Dewar will experience an order of magnitude increase in heat transfer through the MLI, equivalent to a 60% increase through the Dewar in total, due to its larger volume and decreased number of radiation shields relative to the BOBCAT-1 Dewar.