Building “near-space” payloads and lofting them into the stratosphere on weather balloon flights is far less expensive than launching payloads into outer space using rockets. However, even weather balloon flights can feel costly and be time-consuming, especially in educational contexts. Hence it is best for payloads to be ground-tested as rigorously as possible before flight, to identify (and remedy) potential failures.
One particularly useful device for simultaneously exposing payloads to the low temperatures and low pressures they will experience on a stratospheric balloon flight is a thermal-vacuum chamber (called a thermal-vac for short), such as the home-built “High Altitude Chamber” reported on by Howard Brooks of DePauw University. Using such a chamber, one can “bring the stratosphere (at least its low pressure and low temperature characteristics) into a lab or classroom” before deploying hardware and expending consumable resources on potentially-unsuccessful flight tests.
This paper discusses our experiences constructing, then making various modifications to, Brooks’ thermal-vac chamber. While maintaining low cost, we were able to reach lower pressures and lower temperatures than Brooks reported, in part by using aluminum endplates (rather than Lexan) and by using dry-ice cooling (rather than deep-freezer cooling). We also used removable rubber gaskets for sealing the chamber and used simple metal feed-throughs to supply power to internal components from an external DC power supply to reduce the number of batteries depleted during thermal-vac testing. We also constructed a microcontroller-based sensor suite to monitor chamber conditions that is capable of communicating with the outside by short-range XBee radio. This provides real-time access to chamber environmental conditions and allows commanding of internal electric heaters and recirculation fans as desired without breaking the chamber’s vacuum seal.
Keywords: stratospheric, ballooning, thermal-vac, chamber, environmental
How to Cite:
Meyer J. & Straub B. & Flaten J., (2020) “Improving a Low-Cost Thermal-Vac Chamber for Testing Stratospheric Ballooning Payloads”, Academic High Altitude Conference 2019(1). doi: https://doi.org//ahac.243