Variable Heat Rejection Radiator Using Shape Memory Alloys
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Solution Overview
Problem
Current thermal control systems in vehicles face challenges in maintaining a constant internal temperature due to highly varying thermal environments, limiting their heat rejection capacity and requiring complex, heavy, and costly solutions, especially in deep space exploration where a high turn-down ratio is necessary.
Innovation Solution
A heat rejection system utilizing temperature-sensitive shape memory materials that change shape in response to temperature, altering the effective view factor and emissivity to adjust heat rejection capacity passively, without active control, by employing a bias loading structure and thermally conductive materials to manage heat rejection efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a constant area radiator is used, then the heat rejection capacity is limited, but the device complexity is reduced
Solution Approach 1:
The patent applies dynamics by making the radiator area variable rather than constant. The radiator panels can dynamically adjust their deployed area to match the varying heat rejection requirements of the spacecraft. This is achieved through deployable mechanisms that allow the radiator surface area to change from a minimum to a maximum extent, enabling the system to adapt to different thermal conditions without requiring complex active control systems.
2Productivity
If the view factor is increased, then heat rejection capacity is improved, but the device complexity increases
Solution Approach 1:
The view factor is made dynamic through the deployable radiator design. As the radiator panels are deployed or retracted, the view factor between the radiator surface and space changes dynamically. This allows the system to optimize heat rejection capacity by adjusting the geometric relationship between the radiator and the surrounding environment, achieving high heat rejection when needed without complex control mechanisms.
3Productivity
If the emissivity is increased, then heat rejection capacity is improved, but the device complexity increases
Solution Approach 1:
The patent applies local quality by differentiating the surface properties of the radiator. The surface is designed with high emissivity characteristics in the infrared spectrum to maximize thermal radiation efficiency. This is achieved through selective surface treatments or coatings that enhance emissivity specifically for thermal radiation wavelengths, while maintaining other required properties. The high emissivity surface is applied locally to the radiator panels where it is most effective for heat rejection.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enables a high turn-down ratio heat rejection system that is lightweight, efficient, and reduces complexity, allowing for smooth variation in heat rejection capacity, suitable for deep space missions by passively adjusting to changing thermal conditions without additional power or instrumentation.
Implementation Method 1
temperature sensitive shape memory materials that change shape in response to temperature
Implementation Method 2
at least one thermal transport fluid structured and arranged to transport such collected heat
Implementation Method 3
thermal energy radiator structured and arranged to reject heat from at least one heat source
Data Source
AI summary
A heat rejection system that employs temperature sensitive shape memory materials to control the heat rejection capacity of a vehicle to maintain a safe vehicle temperature. The technology provides for a wide range of heat rejection rates by varying the shape and thus effective properties of the heat rejection system in response to temperature. When employed as a radiator for crewed spacecraft thermal control this permits the use of higher freezing point, non-toxic thermal working fluids in single-loop thermal control systems for crewed vehicles in space and other extraterrestrial environments.