Dan Butler

Flight Testing of the Capillary Pumped Loop Flight Experiment

The Capillary Pumped Loop 3 (CAPL 3) experiment was a multiple evaporator capillary pumped loop experiment that flew in the Space Shuttle payload bay in December 2001 (STS‐108). The main objective of CAPL 3 was to demonstrate in micro‐gravity a multiple evaporator capillary pumped loop system, capable of reliable start‐up, reliable continuous operation, and heat load sharing, with hardware for a deployable radiator. Tests performed on orbit included start‐ups, power cycles, low power tests (100 W total), high power tests (up to 1447 W total), heat load sharing, variable/fixed conductance transition tests, and saturation temperature change tests. The majority of the tests were completed successfully, although the experiment did exhibit an unexpected sensitivity to shuttle maneuvers. This paper describes the experiment, the tests performed during the mission, and the test results.

Loop heat pipes and capillary pumped loops-an applications perspective

Capillary pumped loops (CPLs) and loop heat pipes (LHPs) are versatile two-phase heat transfer devices which have recently gained increasing acceptance in space applications. Both systems work based on the same principles and have very similar designs. Nevertheless, some differences exist in the construction of the evaporator and the hydro-accumulator, and these differences lead to very distinct operating characteristics for each loop. This paper presents comparisons of the two loops from an applications perspective, and addresses their impact on spacecraft design, integration, and test. Some technical challenges and issues for both loops are also addressed.

Testing of a Miniature Loop Heat Pipe Using a Thermal Electrical Cooler for Temperature Control

This paper describes the design and testing of a miniature LHP having a 7 mm O.D. evaporator with an integral CC. The vapor line and liquid line are made of 1.6mm stainless steel tubing. The evaporator and the CC are connected on the outer surface by a copper strap and a thermoelectric (TEC) is installed on the strap. The TEC is used to control the CC temperature by applying an electrical current for heating or cooling. Tests performed in ambient included start-up, power cycle, sink temperature cycle, and CC temperature control using TEC. The LHP demonstrated very robust operation in all tests where the heat load varied between 0.5W and 1OOW, and the sink temperature varied between 243K and 293K. The heat leak from the evaporator to the CC was extremely small. The TEC was able to control the CC temperature within +/-0.3K under all test conditions, and the required control heater power was less than 1W.

The capillary pumped loop III (CAPL III) flight demonstration description and status

To realize the full benefits of capillary pump loop (CPL) devices, for use in spacecraft thermal control subsystems, a reliable, load sharing, multiple evaporator system must be developed and successfully demonstrated in space. The Capillary Pumped Loop Flight Experiment 3 (CAPL III) will be the second attempt to flight demonstrate a multiple evaporator CPL in space environment. Using the lessons learned from CAPL I, which was flown aboard STS-60 in February 1994, new hardware and concepts are being developed for CAPL III to enable load sharing between evaporators, reliable system start-up/re-start, and reliable continuous operation. Started in May 1996, CAPL III is primarily a joint venture between the Naval Research Laboratory and the NASA-Goddard Space Flight Center, with Swales and Associates, Inc. as an industry partner. The program is scheduled to meet an STS flight opportunity in mid-1998. This paper will present the requirements and the preliminary design description of the CAPL III CPL system.