Variable Emittance Thermochromic Material for Satellite Thermal Control
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Solution Overview
Problem
Spacecrafts with low mass have difficulty regulating temperature due to low thermal capacitance, making them susceptible to extreme temperature swings, and existing thermal management systems are costly, complex, and risky for catastrophic damage in space.
Innovation Solution
A variable emittance thermochromic material with spatially isolated transition metal-based particles that change properties from non-metallic to semi-metallic as temperature increases, maintaining high emittance at high temperatures and low emittance at low temperatures, integrated into a device for passive thermal control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If passive radiative surfaces with fixed thermal emissivity are used, then heat dissipation is simplified, but temperature regulation effectiveness deteriorates due to inability to adapt to varying temperature conditions
Solution Approach 1:
The patent applies parameter changes by utilizing materials whose thermal emissivity parameter dynamically changes with temperature. The thermochromic material transitions from low emissivity at low temperatures to high emissivity at high temperatures, automatically adapting to temperature conditions without complex control systems.
Solution Approach 2:
The patent employs composite materials combining thermochromic substances with matrix materials to create surfaces with temperature-dependent emissivity. This composite structure enables the surface to exhibit different thermal radiation properties at different temperatures, resolving the contradiction between simplicity and effectiveness.
2Temperature
If active thermal management systems are used, then temperature control precision is improved, but system reliability deteriorates due to risk of catastrophic damage in space
Solution Approach 1:
The patent implements self-service by designing a thermal management system that automatically regulates temperature without external control or power supply. The thermochromic material inherently responds to temperature changes, adjusting its emissivity to maintain thermal balance, thereby eliminating the need for complex active control systems that could fail.
Solution Approach 2:
The patent replaces mechanical/electrical active control systems with a passive physical phenomenon-based system. Instead of using motors, heaters, or electronic controllers that can fail, the system utilizes the inherent thermochromic property of materials to achieve temperature regulation, significantly improving reliability.
3Power
If thermal radiators are sized for maximum power dissipation, then heat dissipation capability is improved, but weight increases which is problematic for smaller spacecraft
Solution Approach 1:
The patent applies dynamics by making the thermal emissivity of the radiator surface dynamic rather than static. The thermochromic coating automatically adjusts its emissivity based on temperature, allowing the same radiator surface to provide different levels of heat dissipation as needed, thereby reducing the overall size and weight required for maximum power dissipation capability.
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
The material effectively regulates temperature within a spacecraft, reducing the risk of damage and operational failures due to extreme temperatures, while being cost-effective and simpler in design compared to active systems.
Implementation Method 1
spatially isolated particles, wherein the particles are of a transition metal based complex having temperature dependent properties including a range of non-metallic properties at relatively low temperatures including low emittance, a range of metallic properties at relatively high temperatures and a range of semi-metallic properties, including high emittance, within a temperature range below relatively high temperatures
Data Source
AI summary
The emittance value is a measure of an amount of energy expelled from a given surface area relative to a black-body reference. Depending on the specific coating a change in the emittance value is actively or passively effected. There are known active variable emittance thermal control coatings. However, such coatings are actually panels housing a mixture of both high and low emissivity materials that are electrically manipulated to control the emittance value of the panel. These “coatings” are classified as either electrochromic or electrophorectic. Both electrochromic and electrophorectic coatings require an applied voltage to cause a change in the emittance value of the coating. By contrast, aspects of the present invention do not include active variable emittance thermal control coatings. Aspects of the present invention do include passive variable emittance thermal control coatings and materials. In accordance with aspects of the present invention “passive” means that the variable emittance value changes in response to changes in the environment without active control (e.g. neither a voltage nor a current is applied). More specifically, in accordance with one aspect of the invention a passive variable emittance thermochromic material is provided that has a relatively low emittance value at low temperatures and a relatively high emittance value at high temperatures.