HERCCULES: A university balloon-borne experiment for BEXUS 32 to characterize the thermal environment in the stratosphere using COTS

Abstract

The thermal analysis of stratospheric balloon payloads is still a complex task due to the variable thermal environment during the flight phases as well as due to the convective effects during the ascent. An experiment named HERCCULES has been successfully launched from Esrange Space Centre (Kiruna, Sweden) in September 2023 as part of the REXUS/BEXUS programme. This experiment aimed of serving as a heat transfer and thermal environment characterization platform that allow to validate previously developed methodologies for the worst-case thermal environmental conditions’ selection and the thermal analysis of these platforms. The experiment has been developed in an academic environment and the design, manufacturing, integration and test activities were mainly performed by Bachelor, Master and Ph.D. students with the mentorship of the European Space Agency. A low-cost design was achieved by using Commercial Off-the-Shelf (COTS) without compromising its performance capabilities. The obtained measurements show a colder behavior of the external elements with regard to the worst-case analysis during the first part of the ascent phase. In addition, radiative fluxes measured during the flight show a deviation in the infrared downward flux of about -50Wm−2 at 5km of altitude and a maximum fluctuation of about the 20% in the solar fluxes measurements. Significant advancements have been made for similar missions in terms of mechanical standardization, the use of COTS sensors and electronic components, the improvement of the reliability of the thermal analysis and the development of a software design adhered to standards and recommendations for critical systems.