Thermal Performance of Capillary Pumped Loops Onboard Terra Spacecraft

Abstract

Diane ThiesLockheed M a r t i n Space Operations AbstractThe Terra spacecraft is the flagship of NASA's Earth Science Enterprise. It provides global data on the state of atmosphere, land and oceans, as well as their interactions with solar radiation and one another. Three Terra instruments utilize Capillary Pumped Heat Transport System (CPHTS) for temperature control: Each CPHTS, consisting of two capillary pumped loops (CPLs) and several heat pipes and electrical heaters, is designed for instrument heat loads ranging from 25W to 264W. The working fluid is ammonia. Since the launch of the Terra spacecraft, each CPHTS has been providing a stable interface temperature specified by the instrument under all modes of spacecraft and instrument operations. The ability to change the CPHTS operating temperature upon demand while in service has also extended the useful life of one instrument. This paper describes the design and on-orbit performance of the CPHTS thermal systems.

A numerical comparative study of the effect of working fluids and wick properties on the performance of capillary pumped loop with a flat evaporator

“…The start-up process consists of heating the evaporator to reservoir temperature and clearing of liquid from the vapor line until the vapor front is established inside the condenser [31][32][33]. The time required to initiate boiling inside the evaporator depends upon the heat load, the initial state of the fluid in the evaporator, the working fluid properties and the superheat caused by the presence of nucleation sites inside the porous wick.…”

Energy Harvesting and Thermal Management System in Aerospace

“…A total of six CPLS were used for thermal control of each of the three instruments on TERRA, allowing each instrument to be placed in the most favorable viewing position regardless of temperature. Another example of CPL application is on the refrigerator of the Hubble Space Telescope (Ku et al, 2004), which achieves refrigerator's cooling capacity of 8 W and needs to dissipate 300-400 W of heat.…”

Thermal Vacuum Testing of a Small Loop Heat Pipe with a PTFE Wick for Spacecraft Thermal Control

“…For example, ultra high molecular weight polyethylene wicks were used as a primary pump of the capillary pumped loop for TERRA satellite which was launched in 1999. The size of the pore radius was 15μm 5) . In a previous study, a PTFE wick with the following performance was developed 6) : -Pore radius: 0.8 ~ 2.2 μm -Porosity: 27 ~ 50% In the LHP fabricated in the present study for the thermal vacuum test, a wick with the pore radius of 1.2 μm and porosity of 34% was selected.…”

“…The current wick performance made of the porous metals for the stage-of-art LHPs in Space field are around 1~3 μm 2,3) . There are several reports on plastic wicks, but the development of wicks with small pore size and high permeability proved difficult 4,5) . On the other hand, in this research, PTFE wick with pore radii of 0.8 ~ 2.2 μm could be developed, and tests were conducted in an atmospheric condition to evaluate the basic performance of the LHP by changing power to the evaporator 6) .…”