Green Monopropellant Microtube Combustor for CubeSat Propulsion Project

Most existing spacecraft thermal subsystems rely on single-phase heat transfer, but the drive towards lighter, smaller, higher power subsystems to make future missions possible will require use of two-phase thermal systems. The key challenge in developing two-phase thermal systems is the development of a heat transfer database and reliable models for flow boiling in variable gravity environments from which the performance of two-phase heat exchangers in spacecraft can be confidently predicted. University of Maryland researchers leveraged parabolic flights to obtain local measurements of the wall heat transfer coefficient with high temporal and spatial resolution using infrared (IR) camera and an IR transparent silicon tube. Test conditions included bubbly flow, slug flow, churn flow, annular flow, inverse annular flow, and ultimately dryout. Flow visualization was also performed. The flight demonstrations enabled a preliminary overview of the test matrix for a future ISS experiment.