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A planetary outpost flexible heat pipe heat rejection radiator was designed to reject 25 kW of waste heat. To confirm its performance, a representative segment of this radiator was constructed. The segment was delivered to NASA JSC for future thermal vacuum chamber testing. The innovative portion of this radiator is the heat pipe envelope material; it is a polymer/metal laminate that is lightweight, flexible, heat sealable, vacuum tight, and resistant to UV radiation. The radiator segment consisted of eighty-four (84) vertically oriented, reflux boiling type heat pipes with water as the working fluid. Each heat pipe was 1.9 cm in diameter and 100 cm long. The condenser portion of the heat pipe was constructed from the laminate material; the evaporator portion was 8 cm long and constructed from copper. Integrated into the evaporator was a flow-through porous media heat exchanger that permitted direct circulation of the lunar outpost cooling fluid.

A passive anti icing system for the engine cowl of the Global Hawk UAV was designed and evaluated under a NASA Phase I SBIR Program. The system utilizes five Loop Heat Pipes to remove 3.8 kW of waste heat from the hydraulic system and deliver it to the engine inlet during icing conditions. During non-icing conditions the heat is bypassed to relief valves on the fuel ullage tank to maintain their temperature above freezing. The system masses 18.5 kg and replaces some 15 lbs of existing equipment. A Phase II program to integrate the system aboard the aircraft is underway with the goal of starting flight tests in early 1999.

Current state-of-the-art space radiators are too heavy (5-7 kg/m2) and voluminous to be feasible for some future space missions. Accordingly, there is a need for a revolutionary advanced space radiator system. This paper describes an effort to satisfy that need through the development of an unfurlable heat pipe radiating system. The innovative portion of the unfurlable radiator is the pressure envelope: it is a thin, flexible, heat sealable polymer/metal laminate that is vacuum tight. The laminate allows the radiator to be compactly rolled or folded, easily stowed for transit to space and then unfurled to present a large radiating surface. Condensate return to the evaporator is achieved by a combination of capillary pumping via a flexible porous cable wick and the advanced capillary pumped loop methods of entrainment. The mass density of the radiator is 1.76 kg/m2, representing a reduction in mass of at least a factor of 3 over current radiator technology.

The current trend in military avionics design is to physically move electronics closer to the components they control. This saves on weight, increases component maintainability, reduces aircraft manufacturing costs, and reduces the amount of electromagnetic shielding required. A disadvantage to this trend is the difficulty in achieving thermal control of these remotely located electronics. Accordingly, this thermal control issue is being addressed through the development of a loop heat pipe cold plate (LHPCP). The LHPCP is different than previous hardware of its kind by the fact that it operates in any orientation. The prototype LHPCP that was fabricated and tested was 30 inches long and weighed 1.2 pounds and was able to transport a minimum of 160 watts in any orientation. Future LHPCPs will be made flexible to allow relative motion between the package to be cooled and the heat sink.

This paper describes the transfer of Russian fine pore sintered powder metal wick structure fabrication technology to the United States for use in the construction of U.S. made loop heat pipes (LHPs), capillary pumped loops (CPLs) and heat pipes. Sintered powder metal wick structures have been used in U.S. made heat pipes for over twenty-five years. The typical pore radii for these wick structures range from 10 to 100 microns. Use of a wick material with a pore radius less than 10 microns was limited due to the high pressure drop encountered when used in a standard heat pipe. Conversely, the Russian loop heat pipe is able to get around this high pressure drop constraint due to its unique evaporator design. Prior to the work presented in this paper, the U.S. concentrated on the development of wick structure materials above 10 microns which created a technology void with the advent of the LHP.

The objective of this paper is to describe the results of a technical effort that demonstrated the feasibility of a heat pipe radiator for the M109 A6 Howitzer. The technical effort consisted of the following three parts: establishing full-scale M109 A6 radiator design requirements, designing a full scale heat pipe radiator, and fabricating and testing a representative segment of the full scale heat pipe radiator to demonstrate thermal and hydraulic performance. The design predictions of the heat pipe radiator showed good agreement with the measured test results. Experimental test results indicated that the representative segment heat pipe radiator met and exceeded the design heat load requirement under extreme environmental conditions.

The current trend in military avionics design is to physically move electronics closer to the components they control. This saves on weight, increases component maintainability, reduces aircraft manufacturing costs, and reduces the amount of electromagnetic shielding. A disadvantage to this trend is the difficulty in achieving thermal control of these remotely located electronics. Accordingly, this thermal control issue is being addressed through the development of a flexible loop heat pipe cold plate (FLHPCP). The FLHPCP is different than previous hardware of its kind by the fact that it operates in any orientation. The prototype FLHPCP that was fabricated and tested was 29 inches long and weighed 1.7 pounds. At full adverse orientation (evaporator vertically above condenser), the prototype met the 45 watt heat load requirement at an average evaporator cold plate-to-condenser cold plate temperature drop of 20°C. Reduction of this temperature drop is planned in future development.

A proof-of-concept (POC) lightweight lunar radiator was fabricated and tested. The POC radiator has a specific weight of 5 kg/kW one quarter the specific weight of current space radiators. The significant weight reduction was due to the radiator's unique design. It is a multicellular heat pipe radiator utilizing the lunar gravity for condensate return. The innovation of this radiator is the laminated film material used as the heat pipe envelope. By utilizing a flexible, durable, leak tight laminate structure instead of the typical ridged heat pipe envelope, significant weight reductions were achieved. In addition, the resulting radiator is extremely flexible, allowing it to be rolled or folded and compactly stored during transit to the lunar surface. Testing demonstrated that a laminated film heat pipe radiator offers improved performance and significant mass savings over conventional space radiators.

This paper presents the design and performance of a flexible heat pipe cold plate (FHPCP) that was developed for transporting heat from electronics mounted directly on an F/A-18 aileron actuator to a nearby heat sink. The most obvious heat sink is surrounding structure. A one dimensional steady state heat conduction analysis presented in this paper indicates that utilizing structure is feasible for this application.