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Evaluation of GLAS Demonstration Model Loop Heat Pipe Thermal Vacuum Performance with Various Fluid ChargesTwo loop heat pipes (LHPs) are to be used for tight thermal control of the Geoscience Laser Altimeter System (GLAS) instrument, planned for flight in late 2001. The LHPs are charged with Propylene as a working fluid. One LHP will be used to transport 110 W from a laser a radiator, the other will transport 190 W from electronic boxes to a separate radiator. The application includes a large amount of thermal mass in each LHP system and low initial startup powers. This along with some non-ideal flight design compromises, such as a less than ideal charge level for this design concept with a symmetrical secondary wick, lead to inadequate performance of the flight LHPs during the flight thermal vacuum test in October of 2000. This presentation focuses on identifying; the sources of the flight test difficulties by modifying the charge and test setup of the successfully tested Development Model Loop Heat Pipe (DM LHP). While very similar to the flight design, the DM L14P did have several significant difference in design and method of testing. These differences were evaluated for affect on performance by conforming the DM LHP to look more like the flight units. The major difference that was evaluated was the relative fill level of the working fluid within the concentrically design LHP compensation chamber. Other differences were also assessed through performance testing including starter heater size and "hot biasing" of major interior components. Performance was assessed with respect to startup, low power operation, conductance, and control heater power. The results of the testing showed that performance improves as initial charge increases, and when the starter heater is made smaller. The "hot biasing" of the major components did not appear to have a detrimental effect. As a result of test results of the DM LHP, modifications are being made to the flight units to increase the fluid charge and increase the watt-density of the starter heater.
Document ID
20010029449
Acquisition Source
Goddard Space Flight Center
Document Type
Conference Paper
Authors
Baker, Charles
(Orbital Sciences Corp. Greenbelt, MD United States)
Butler, Dan
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Ku, Jentung
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Grob, Eric
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Swanson, Ted
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Nikitkin, Michael
(Discovery Center of Idaho, Inc. United States)
Paquin, Krista C.
Date Acquired
August 20, 2013
Publication Date
January 1, 2001
Subject Category
Fluid Mechanics And Thermodynamics
Meeting Information
Meeting: STAIFF 2001
Location: Alberquerque, NM
Country: United States
Start Date: February 11, 2001
End Date: February 14, 2001
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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