ASETS-II Oscillating Heat Pipe Space Flight Experiment: Ground Truth Results

Abstract

The ASETS-II experiment consists of three oscillating heat pipes (OHPs), an electronics box, and mounting structures that control boundary conditions. Each OHP consists of 34 channels in a typical single-layer closed loop design. Butane was selected as the working fluid for OHP #1 and #2 for its performance stability. R-134a was selected for OHP #3 in order to explore the Bond number limit’s influence on OHP operation in microgravity. The ASETS-II Flight and Flight Spare hardware were subjected to a comprehensive set of ground testing to baseline performance prior to flight testing. For most test conditions, the Flight and Flight Spare test results for OHP #1 and OHP #2 are within the margin of uncertainty in the measurements. OHP #3 on the Flight hardware performs similarly to OHP #3 on the Flight Spare hardware; however, the difference in performance is outside the margin of uncertainty in the measurements. This variation in performance may be attributable to the fact that OHP #3 is being pushed to operate near its Bond number limit.

Asets-Ii Oscillating Heat Pipe Space Flight Experiment: The First Six Months on Orbit

“…Data collected during the first six months of on-orbit (OO) operations is presented here against the original ground truth (GT) data that was collected for the same OHPs as described in (Taft and Smith 2017). In the analysis of all test cases, experiments were categorized as either "Working" or "Not Working," denoting that the OHPs exhibited sustained steady oscillatory behavior or not, respectively.…”

“…Ground testing has shown that OHP #3 hits an operating limitlikely the swept length, Ls, limit-between 20 W and 40 W of heat input from the small area heater, depending on the condenser temperature (Taft and Smith 2017). In a microgravity environment, the Bo limit should no longer be a factor on OHP operation.…”