Evaluation of a Magnetically-Driven Bearingless Pump for Spacecraft Thermal Management

High-performance capillary heat transport devices such as Loop Heat Pipes (LHPs) and Capillary Pumped Loops (CPLs) are becoming important heat transport devices for spacebased thermal control systems (TCS) simply because the thermal requirements of future spacecraft and satellites outgrow the capabilities of conventional heat pipes. Like heat pipes, LHPs and CPLs contain no mechanical moving part to wear out or to introduce unwanted vibration to the host system. Each of the LHP and CPL technologies has many advantages in its own right. However, a complete TCS may require many specialized thermal control functions that neither LHP nor CPL alone can provide. Moreover, the need for smaller and lightweight TCS demands that the pumping capability of the heat transport loop be at least one-order-of-magnitude higher than those of LHPs and CPLs. The U.S. Naval Research Laboratory proposed the concept of hybrid two-phase capillary/mechanical pumped loop for next-generation space TCS. In the hybrid loop, a mechanical pump augments the capillary pumping head of a multiple-evaporator LHP or CPL. The capillary pumps provide a nearperfect liquid-vapor separation at the evaporators and, therefore, retain the effectiveness of the two-phase (evaporative) heat transfer of the LHP/CPL. A test program was carried out at NRL to assess the capability and reliability/durability of a magnetically-driven bearingless pump manufactured by Advanced Bionics Incorporated for use in the hybrid loop. Results of the test program are presented in this paper to demonstrate the feasibility of the hybrid loop concept for future TCS design.