Spacecraft Two-Phase Thermal Control

DURATION: THREE DAYS
COURSE NO.: 2135

As satellite design-lives are extended and the power of communication equipment is increased, the problem of satellite thermal design becomes increasingly significant. Because of the need to efficiently transfer large amounts of heat in space, two-phase thermal control devices are being used more extensively than ever. High performance heat pipes, loop heat pipes and capillary pumped loops form the backbone of most spacecraft thermal control systems. These devices rely on evaporation and condensation of a working fluid and can passively transfer heat over long distances with small temperature drops, effectively operating as a super thermal conductor. In this course, we describe the basic laws of heat transfer, conduction, convection and radiation and how they apply to spacecraft thermal systems. We provide useful data and show practical examples of how to analyze and design two-phase spacecraft thermal systems. We provide rules of thumb for selecting the best thermal management solution. We discuss heat pipe, loop heat pipe and capillary pump loop history, theory and design. How to select different working fluids, containment envelopes, wicks and the sizing of these devices will be covered. Transient operation will be discussed. Issues with respect to welding TIG, electron beam, and the use of friction welding will be covered. Spacecraft radiator design is discussed, including fixed and deployable radiators. This includes surface coatings, structural considerations, optimum tube spacing, micrometeoroid protection, materials selection, interface issues between heat pipe panels, and deployable radiator mechanisms. Testing will also be discussed, 1g versus operation in 0g issues, instrumentation, acceptance versus qualification. Lessons learned will be covered with issues such as welding, materials issues, processing, integration, configuration management, testing, non-condensable gas generation, as well as program management.

COURSE MATERIALS:
Include extensive notes and reference materials.

System analysts, program managers, project managers, power system engineers, test engineers, and all mechanical and aerospace engineers that do not have a detailed background with two-phase thermal control hardware.

This course will provide an end-to-end, in-depth knowledge of two-phase spacecraft thermal control devices for satellites. Overall design philosophy for thermal systems as well as design rules of thumb will be provided. The design, analysis and fabrication of thermal control hardware (such as heat pipes, loop heat pipes and capillary pumped loops), radiators (fixed and deployable) and surface coatings will be covered. Testing in 1g versus 0g will be discussed along with other issues. Lessons learned will be provided including issues with welding, testing, materials, processing, on-orbit operation and more.

1. Two-phase Thermal Control Technologies .
   

   Discussion of Constant Conductance Heat Pipes, Variable Conductance Heat Pipes, Loop Heat Pipes and Capillary Pumped Loops. History and Applications – Rules of thumb for space applications. Theory of Operation: Fundamentals, Wetting, Pressure Balance, Transport Limitations. Theory Constant and Variable Conductance Heat Pipes. Theory of Loop Heat Pipes and Capillary Pumped Loops. Design: Working Fluids, Wicks, Container, Materials Compatibility, Fluid Inventory, Welding. Design of Heat Pipes: Performance Curves, Requirements, Ground Testing, Spacecraft Integration and Test, On-Orbit Degradation. Design Loop Heat Pipes and Capillary Pumped Loops: Performance Curves, Requirements, Ground Testing, Spacecraft Integration and Test, On-Orbit Degradation.

2. Spacecraft Radiator Design.
   

   Optimum Tube Spacing. Normalizing Radiation Heat Transfer for Design. Micro Meteoroids. Optical Solar Reflectors. Structure and Materials. Fixed and Deployable Designs.

3. Testing.
   

   1g versus 0g. Instrumentation. Acceptance criteria. Qualification.

4. Lessons Learned.
   

   Welding – Mil Spec 2219 Class A,B,C. Materials – Aluminum Extrusions and Bimetallic Welds Joints. Processing – Cleaning and Outgassing. Integration – Bend Radius with respect to Mating Heat Pipes. Configuration Management - Problems. Testing – Testing in 1g. On-Orbit Operation – Gas Generation, Transients. Handling and Shipping. Earned Value Program Management.