Modular membrane controlled three-phase deployable radiator
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Solution Overview
Problem
Current spacecraft thermal management systems with fixed radiators fail to maintain coolant temperature at design levels across varying heat loads, requiring active control and adding complexity and weight, while passive turn-down capabilities below 200:1 are insufficient for orbital applications.
Innovation Solution
A deployable radiator system with a modular membrane-controlled three-phase design using ammonia as the working fluid, incorporating a phase separator and bypass control valve to achieve a high turndown ratio of 200:1 through selective freezing and thawing of ammonia in the radiator condenser, ensuring consistent coolant temperature and handling high pressures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed radiator design is used, then the structure is simple and reliable, but the system cannot maintain coolant temperature at design levels across varying heat loads, requiring active control mechanisms
Solution Approach 1:
The radiator system uses passive turn-down capability where the working fluid automatically freezes and thaws in response to heat load variations, maintaining coolant temperature without requiring active control mechanisms. The system serves itself by utilizing the phase change properties of the working fluid to modulate heat rejection proportional to the applied heat load.
Solution Approach 2:
The patent employs freezing and thawing of the ammonia working fluid in the radiator condenser to achieve passive turn-down capability. During low heat load conditions, the working fluid freezes, reducing heat rejection area and maintaining coolant temperature. During high heat load conditions, the fluid thaws, increasing heat rejection capacity.
2Device complexity
If passive turn-down capability below 200:1 is used, then the system is simpler, but the turndown ratio is insufficient for orbital applications requiring cooling over a large wide range of operating modes
Solution Approach 1:
The patent achieves a 200:1 turndown ratio by utilizing the phase transition of ammonia working fluid between solid and liquid states in the radiator condenser. This phase change mechanism enables the system to adapt to a wide range of heat loads from 2.5 W to 500 W while maintaining coolant temperature at 25°C, providing the necessary adaptability for orbital applications.
3Temperature
If active control mechanisms are added to maintain coolant temperature, then temperature stability is improved, but the system weight and complexity increase
Solution Approach 1:
The radiator system maintains coolant temperature stability through passive mechanisms where the working fluid automatically freezes and thaws in response to temperature and heat load variations. This self-regulating behavior eliminates the need for active control mechanisms, reducing system weight while maintaining temperature stability at 25°C across the 200:1 heat load range.
4Adaptability or versatility
If freezing of ammonia working fluid is allowed for turn-down capability, then passive turn-down ratio increases, but high pressures are experienced during freezing and thawing events
Solution Approach 1:
The radiator system incorporates design features that accommodate and cushion the high pressures experienced during freezing and thawing events of the ammonia working fluid. The structural design includes pressure relief mechanisms and robust construction in the radiator condenser to handle the stress of phase change while enabling the 200:1 passive turn-down 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 system effectively maintains coolant temperature at 25°C across a 2.5 to 500 W heat load range, achieving a 200:1 turndown ratio with passive control, reducing complexity and weight, and ensuring reliable operation in orbital environments for extended periods.
Implementation Method 1
passive turn-down capability via stagnation and freeze of the ammonia working fluid in the radiator condenser
Implementation Method 2
Sections of the radiator will selectively freeze to assist the turndown
Implementation Method 3
The phase separator is an integrated membrane phase separator that achieves separation via capillary action
Implementation Method 4
rejecting heat to deep space at −269° C.
Data Source
AI summary
A radiator system uses an innovative passive control scheme in combination with dependable mechanical design features to meet or exceed the requirements for orbital applications. The disclosed radiator system is unique because we target an extremely high turndown ratio of 200:1 with an entirely passive two-phase pumped loop using ammonia as the working fluid. Sections of the radiator will selectively freeze to assist the turndown, and the mechanical design of the radiator can handle the high pressures experienced during such freezing and thawing events.