Balloon Flight Test of a Low-Temperature Radiator

Abstract

This paper presents the thermal design and analysis of a low-temperature radiator for the balloon-borne General Anti-Particle Spectrometer (GAPS) project. GAPS requires a radiator that can be cooled passively to below −50°C. However, a thermal design for a radiator operating below −50°C has not yet been established. The convective heat transfer of a low-pressure atmosphere, crucial to designing a low-temperature radiator, has not been investigated well. To validate our design concept of the low-temperature radiator, we mounted a scaled-down GAPS-radiator piggybacked on a balloon payload launched from Fort Sumner, NM, US. During the flight at float altitudes around 38 km, when the radiator was pointed away from the Sun, it was successfully chilled to −58°C. Temperatures measured during the flight agreed well with a numerical thermal model considering forced convection and natural convection. Consequently, the convective heat transfer coefficient was validated using the low-temperature radiator plate, where convective heat transfer occupied ~20 % of heat input in total during the floating phase. These results verify our design concept of the GAPS low-temperature radiator and can also contribute to the accurate thermal design of other balloon missions.