Capacitance-Based Propellant Mass Measurement in Microgravity

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Solution Overview

Problem

Conventional propellant mass measuring systems in microgravity environments are inaccurate, especially when the fuel level is low, due to challenges in accurately determining liquid mass in moving or splashing conditions, and vaporization issues that lead to pressure increases and propellant loss.

Innovation Solution

A capacitance-based measurement system using electrodes and capacitance measuring circuits within fuel tanks, connected to computing systems, which can determine propellant mass by measuring capacitance changes regardless of fluid orientation, and includes liquid acquisition devices to direct propellant flow while minimizing vapor bubble formation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional propellant mass measuring systems are used in microgravity environments, then the system can operate in space, but measurement accuracy deteriorates especially at low fuel levels

Engineering Contradiction:

Improvepropellant mass measurement accuracyVSAvoidmeasurement reliability at low fuel levels

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent replaces conventional mechanical or electrical contact-based mass measurement systems with a capacitance-based measurement system. The capacitance probe measures changes in electrical capacitance caused by the dielectric properties of the propellant, eliminating mechanical contact issues and providing accurate measurements even when propellant levels are low or when the propellant is in motion.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent utilizes changes in electrical capacitance parameters to detect propellant mass. By measuring the capacitance between a probe electrode and the tank wall, the system detects changes in the dielectric environment caused by varying propellant levels and masses, providing continuous accurate measurement throughout the propellant consumption cycle.

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If capacitance-based measurement is used, then measurement accuracy improves, but device complexity increases due to additional electrodes and circuits

Engineering Contradiction:

Improvepropellant mass measurement accuracyVSAvoidcomplexity of electrodes and measurement circuits

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent makes the fuel tank wall serve dual functions: as both the containment structure and as one electrode of the capacitance measurement system. This eliminates the need for a separate ground electrode, reducing component count while maintaining measurement capability.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The system uses the existing conductive structure of the fuel tank itself as part of the measurement circuitry. The tank wall acts as the reference electrode, eliminating the need for additional external components and simplifying the overall device architecture.

Inventive Principle:

Principle #25Self-service

3Productivity

If liquid acquisition devices are used to direct propellant flow, then propellant delivery improves, but vapor bubble formation increases causing measurement errors

Engineering Contradiction:

Improvepropellant delivery efficiencyVSAvoidcapacitance measurement accuracy

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The capacitance measurement system provides continuous feedback on the actual propellant level and mass, allowing the liquid acquisition device operation to be monitored and adjusted. This feedback mechanism helps distinguish between genuine propellant level changes and transient effects caused by vapor bubbles, improving measurement reliability.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The capacitance measurement system operates continuously and is insensitive to transient disturbances such as vapor bubbles. By providing continuous measurement rather than intermittent sampling, the system maintains accurate propellant mass determination even during dynamic liquid acquisition device operation when vapor bubbles may be present.

Inventive Principle:

Principle #20Continuity of useful action

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 provides accurate and reliable propellant mass measurements in microgravity environments, even at low fuel levels, by averaging capacitance measurements over time and reducing vapor bubble agitation, thus improving measurement precision and preventing propellant loss.

Implementation Method 1

Methodology Applied

Scientific EffectCapacitance: Capacitance

Data Source

PatentUS12055427B1Apparatus and method for determination of liquid mass

Publication Date: 2024.08.06 UNIVERSITY OF ALABAMA

AI summary

The present disclosure generally pertains to devices and methods for determining propellant mass based on average measurements irrespective of the fluid orientation in a fuel tank. The device is useful in detecting fuel levels in tanks where the fuel is in motion, for instance in aircraft (i.e., undergoing varying acceleration maneuvers) or spacecraft (i.e., a microgravity environment). The devices and methods can also be used for determining the liquid in a surface tension screen liquid acquisition device (LAD), and particularly, the incipient breakdown as gas bubbles enter or are formed inside the LAD as the screen dries or heat transfer induces vaporization. The same basic electrode configuration can be used to stir the liquid to reduce thermal stratification and condense vapor bubbles.