Search Results

The first space flight cryogenic flexible diode heat pipes (CFDHPs) were developed and verified under micro-gravity conditions on the Space Shuttle during STS-94 (July 1997) and the previous, minimum mission STS-83 (March 1997). The heat pipe working fluids were oxygen (with an operating range of 60 to 145 Kelvin) and methane (95 - 175 Kelvin). The heat pipes were verified as part of the Cryogenic Flexible Diode Heat Pipe (CRYOFD) flight experiment. CRYOFD was the third and fourth flights of the Hitchhiker based Cryogenic Test Bed (CTB). CRYOFD was managed by the Air Force Research Laboratory (AFRL) Phillips Research Site with NASA's Goddard Space Flight Center (GSFC) co-sponsoring the experiment, the Air Force's Space Test Program (STP) and GSFC's Hitchhiker (HH) group provided the Shuttle integration and support. Jackson and Tull (J&T) and Swales Aerospace, Inc. (SAI) executed the program as a Phase II SBIR under the AFRL.

An IBM Personal Computer (PC) version of the Groove Analysis Program (GAP) was developed to predict the steady state heat transport capability of axially grooved heat pipes for a specified groove geometry and working fluid. In the model, the heat transport capability of an axially grooved heat pipe, usually governed by the capillary limit, is determined by the numerical solution of the governing equation for momentum conservation with the appropriate boundary conditions. This paper discusses the theory behind the development of the GAP model. It also presents many useful capabilities of the model. Furthermore, correlations of flight test performance data using GAP are presented and discussed.

This paper presents the test results and data correlation for the Heat Pipe Performance Flight Experiment which was a Class D middeck experiment flown aboard the Space Shuttle Columbia (STS-52) in October of 1992. Three categories of heat pipe performance were examined: static mode, operation under applied acceleration, and re-wicking capability. Two aluminum/freon axially grooved heat pipes, ten copper/water axially grooved heat pipes, and four fibrous wick copper/water variable conductance heat pipes were tested. Ground and flight test results for the axially grooved heat pipes are discussed and correlated with analytical models. Correlation of flight test data for cryogenic axially grooved oxygen heat pipes and a description of the Groove Analysis Program (GAP) is also presented.

This paper summarizes flight test results which were obtained in the Cryogenic Two Phase Flight Experiment (CRYOTP). This was a HitchHiker canister experiment that was flown aboard the space shuttle Columbia in March of 1994. Two flight articles were tested independently. The first was a nitrogen heat pipe with five parallel fibrous copper cable wicks. It did not startup in either of two cooldown cycles. Post flight inspection of the heat pipe showed that it had its original fluid charge. The failure to startup is attributed to the large fluid inventory and the conduction gradient that existed due to nominal parasitic heat leaks along the titanium heat pipe tube. Complete success was obtained with the Brilliant Eyes Thermal Storage Unit (BETSU) which contains 2-methylpentane phase change material for temperature control at 120K. More than 200 hours of on orbit tests consisting of several cooldown cycles and 55 freeze/thaw cycles was obtained with BETSU.

This paper presents the analytical results of a thermal hydraulic study to determine an “optimum” two-phase heat pipe/heat exchanger radiator panel configuration for the Space Station Freedom. The study was based on using conventional axially grooved heat pipes in combination with integral two-phase heat exchangers. Various design parameters were traded to arrive at an optimized panel design that satisfied the thermal requirements. For two-phase flow across a radiator array consisting of eight panels with fourteen heat pipes per panel, small diameter lines acting as flow restrictions are needed at the exit of each heat exchanger to balance the flow across each panel and the radiator array. The paper also presents the test results with a representative subscale heat pipe/heat exchanger radiator panel. In general, the heat pipes exhibit transport capabilities that exceed the design requirements. Balanced flow across each heat exchanger was also demonstrated.

The Cryogenic Heat Pipe (CRYOHP) Experiment has been designed to test two cryogenic heat pipes independently in a micro-gravity environment. The CRYOHP experiment is manifested for flight aboard the shuttle (STS-53) which is scheduled for launch in November, 1992. This paper presents the design of this experiment and the thermal vacuum verification test results. A correlation of the test data and the planned mission operations are also provided.