Nuclear Reactor Direct Drive for Cryocooler Turbine Boil-Off Control
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Solution Overview
Problem
Conventional nuclear thermal propulsion systems for spacecraft suffer from inefficiencies due to multiple power conversion steps, leading to waste heat and reliance on external power sources like photovoltaic arrays, which are dependent on illumination and batteries, and result in significant boil-off of liquid hydrogen propellant.
Innovation Solution
A direct drive system using a nuclear reactor to heat a thermal working fluid that directly drives a cryocooler turbine, minimizing power conversion steps and reducing waste heat, while maintaining cryogenic temperatures for liquid hydrogen storage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional photovoltaic arrays and motor-driven systems are used to power the cryocooler, then electrical power can be provided to drive the cryocooler components, but multiple power conversion steps result in waste heat generation and reduced system efficiency
Solution Approach 1:
The patent extracts and eliminates the intermediate photovoltaic array and motor components from the power conversion chain. By directly coupling the nuclear reactor's thermal output to the cryocooler's mechanical drive system through a turbine, it removes the unnecessary conversion steps (thermal→electrical→mechanical) and replaces them with a direct thermal→mechanical pathway, thereby reducing energy loss as waste heat and simplifying the device structure
Solution Approach 2:
The patent replaces the electrical-mechanical drive system (photovoltaic array→motor→turbine) with a direct thermal-mechanical drive system (nuclear reactor→thermal working fluid→turbine). This substitution eliminates the need for electrical power conversion and direct mechanical drive components, reducing both energy loss and system complexity while maintaining the ability to drive the cryocooler components
2Reliability
If photovoltaic arrays are used to provide electrical power, then power can be supplied to the cryocooler, but the system becomes dependent on illumination and requires batteries for eclipse periods
Solution Approach 1:
The nuclear reactor provides self-sufficient thermal power that does not depend on external illumination conditions. The reactor core continuously generates thermal energy through nuclear fission, enabling the cryocooler to operate reliably during both illuminated and eclipse periods without requiring separate battery systems or photovoltaic arrays, thus achieving both reliability and independence from environmental conditions
Solution Approach 2:
The nuclear reactor serves as a universal power source that provides thermal energy for the cryocooler regardless of illumination conditions. Unlike photovoltaic arrays that only function during illuminated periods, the nuclear reactor maintains consistent power output through all space mission phases including eclipse, thereby eliminating the need for multiple independent power systems and enhancing overall system adaptability
3Duration of action of stationary object
If liquid hydrogen is stored for years or decades in space, then long-term propellant storage is achieved, but significant boil-off occurs in the vacuum of space
Solution Approach 1:
The nuclear reactor provides continuous thermal energy to the cryocooler system throughout the entire storage duration, maintaining cryogenic temperatures without interruption. This continuous cooling action prevents hydrogen boil-off over extended periods (years to decades) by constantly removing heat that would otherwise cause propellant loss, thereby enabling long-term storage while minimizing substance loss
Solution Approach 2:
The system maintains the temperature parameter of the stored hydrogen at cryogenic levels through continuous nuclear-powered cooling. By actively controlling the temperature parameter rather than relying on passive insulation alone, the system prevents the phase change from liquid to gas that would cause boil-off, enabling both long-duration storage and minimal propellant loss
4Power
If reactor-driven electrical power generators are used to provide electrical power, then power can be generated from the nuclear reactor, but multiple conversion steps still produce waste heat
Solution Approach 1:
The patent replaces the electrical power generation pathway (nuclear reactor→thermal→electrical generator→electrical power) with a direct mechanical drive pathway (nuclear reactor→thermal working fluid→turbine→mechanical power). This substitution eliminates the electrical generation step and its associated waste heat, directly converting thermal energy to mechanical work to drive the cryocooler components
Solution Approach 2:
The patent extracts and removes the electrical power generation components (generators, electrical systems) from the nuclear reactor power conversion chain. By directly coupling the reactor's thermal output to the turbine-mechanical drive system, it eliminates the intermediate electrical conversion step that generates waste heat, thereby reducing energy loss while maintaining the ability to power cryocooler components
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 achieves efficient cryogenic fluid management with minimal boil-off and reduced waste heat, enabling long-term storage and operation of liquid hydrogen propellant in space missions.
Implementation Method 1
heating a first thermal working fluid via thermal communication of the first thermal working fluid with a nuclear reactor core
Implementation Method 2
heating a first thermal working fluid via thermal communication of the first thermal working fluid with a nuclear reactor core
Implementation Method 3
driving the cryocooler turbine with the heated first thermal working fluid
Implementation Method 4
driving the cryocooler turbine with the heated first thermal working fluid
Implementation Method 5
driving a first compressor of the CFM system via a shaft rotated by the cryocooler turbine
Implementation Method 6
driving a first compressor of the CFM system via a shaft rotated by the cryocooler turbine
Implementation Method 7
cooling a second thermal working fluid via thermal communication of the second thermal working fluid with a heat exchanger
Implementation Method 8
cooling a second thermal working fluid via thermal communication of the second thermal working fluid with a heat exchanger
Implementation Method 9
cooling the propellant via thermal communication of the second thermal working fluid with the cryogenic tank
Implementation Method 10
cooling the propellant via thermal communication of the second thermal working fluid with the cryogenic tank
Data Source
AI summary
Systems and methods for nuclear reactor direct drive of a cryocooler turbine. A nuclear thermal propulsion (NTP) system may have a nuclear reactor that heats a thermal working fluid for directly driving the turbine to power a cryogenic fluid management (CFM) system for keeping propellant at cryogenic temperatures. The features may be used on NTP rockets. The propellant may be liquid hydrogen.