Propellant Tank Ullage Pressure Control via Atomized Fluid Injection
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Solution Overview
Problem
In microgravity environments, propellant tanks face challenges with ullage pressure collapse and inefficient propellant transfer due to the flashing of super cold propellants, which can lead to structural failures and propellant loss during refueling in space.
Innovation Solution
The use of aerodynamic pumps, atomizers, or mechanical pumps with condensable or incondensable motive fluids to control ullage temperature and pressure within propellant tanks, reducing pressure without venting and minimizing propellant loss by creating a vacuum and atomizing the propellant mixture to lower ullage gas temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If a vent valve is used to control pressure during propellant transfer in microgravity, then tank pressure can be controlled, but valuable liquid propellant is vented instead of boil-off gas resulting in propellant loss
Solution Approach 1:
A heat exchanger is introduced as an intermediary device between the propellant transfer line and the vent valve. The heat exchanger cools the boil-off gas to condense it back into liquid propellant, which then returns to the tank. This mediator converts the harmful vented gas back into useful liquid propellant, eliminating the loss while maintaining pressure control capability.
Solution Approach 2:
The system utilizes phase transition by cooling the boil-off gas through a heat exchanger to condense it back into liquid phase. This phase change from gas to liquid allows the recovered propellant to return to the tank, preventing loss while controlling tank pressure during microgravity propellant transfer operations.
2Quantity of substance
If super cold liquid propellant is transferred into a warmer tank in microgravity, then the tank can be filled, but the propellant flashes boil causing increased tank pressure that must be controlled
Solution Approach 1:
The propellant is pre-cooled in a heat exchanger before entering the warmer propellant tank. This preliminary cooling action prevents the propellant from flashing boil upon contact with the warmer tank environment, thereby controlling tank pressure while still achieving complete propellant fill quantity in microgravity conditions.
Solution Approach 2:
The system replaces mechanical pressure control methods with a thermal management approach using a heat exchanger. By substituting the mechanical venting system with a thermal cooling system, the patent achieves pressure control through temperature management, preventing flash boil while maintaining full propellant fill capability.
3Quantity of substance
If ullage volume in a propellant tank is increased, then more propellant can be stored, but ullage pressure collapse risk increases when propellant unsettles during acceleration or deceleration
Solution Approach 1:
Pressure sensors monitor ullage pressure in real-time and provide feedback to a control system. When pressure collapse is detected during acceleration or deceleration events, the system activates heating elements or adjusts propellant transfer to restore pressure. This feedback loop maintains reliable pressure control while allowing increased ullage volume for greater propellant storage capacity.
Solution Approach 2:
Heating elements are pre-installed in the ullage space to provide beforehand cushioning against pressure collapse. When acceleration or deceleration causes propellant to settle and cool the ullage, these pre-positioned heating elements can immediately activate to warm the ullage gas and prevent pressure collapse, protecting the tank structure while maintaining high propellant storage capacity.
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 method allows for efficient propellant transfer and ullage pressure control, preventing ullage pressure collapse and maintaining tank integrity during refueling in microgravity environments, both in space and on Earth, without venting the tank and minimizing propellant loss.
Implementation Method 1
A jet pump accelerates a condensable motive fluid through a nozzle to create a high velocity fluid stream or jet that reduces local static pressure and thereby creates a vacuum. The low static pressure syphons or suctions liquid cryogen out of the liquid space within the propellant tank where it is entrained into the flow of the high velocity motive fluid within a mixing tube or chamber
Implementation Method 2
The low static pressure syphons or suctions liquid cryogen out of the liquid space within the propellant tank
Implementation Method 3
The two fluids mix to form a highly atomized spray of both the liquid cryogen and the motive fluid through momentum transfer between the coflowing fluids
Implementation Method 4
The mixed solution is then exhausted into the ullage space of the propellant tank where evaporation of the atomized spray lowers the ullage gas temperature
Implementation Method 5
A jet pump accelerates a condensable motive fluid through a nozzle to create a high velocity fluid stream or jet that reduces local static pressure and thereby creates a vacuum. The low static pressure syphons or suctions liquid cryogen out of the liquid space within the propellant tank where it is entrained into the flow
Data Source
AI summary
A system and method for controlling the temperature and pressure within a propellant tank containing cryogenic liquid and gaseous phase propellants, the latter also referred to as ullage, by adding an atomized fluid or mixture of fluids having one or more constituent parts to the ullage, where the atomized fluid(s) has a temperature less than the temperature of the ullage. The motive fluid may include a condensable constituent which aids in reducing pressure in the tank or a incondensable constituent which aides in maintaining pressure in the tank.