Laser Ranging Propellant Mass Measurement in Zero Gravity
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Solution Overview
Problem
Conventional methods for determining propellant mass and center of gravity in three-axis stabilized spacecraft are inaccurate due to the absence of a significant gravitational field, leading to errors in propellant remaining predictions and inefficient mission planning, especially in zero or low gravity environments.
Innovation Solution
A system and method using a ranging device coupled to the interior of a propellant tank to determine the location of a membrane within the tank, calculating propellant volume and mass based on ranging signal delays, and determining the center of gravity by accounting for temperature and pressure variations, without requiring additional hardware like pressure gauges or moving parts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional gravity-based methods are used to determine propellant content, then measurement is simple in spin-stabilized satellites, but the method is inappropriate for three-axis stabilized spacecraft due to absence of gravitational field
Solution Approach 1:
The patent replaces gravity-based mechanical measurement methods with a laser ranging system that uses electromagnetic waves to measure membrane displacement. The laser ranging device transmits laser beams to the propellant membrane and measures the time of flight of the reflected signals, enabling propellant mass determination in zero-gravity environments where conventional methods fail.
Solution Approach 2:
The patent introduces a laser beam as an intermediary to measure the position of the propellant membrane. The laser ranging device uses the light signal as a mediator to indirectly determine propellant mass by measuring the displacement of the membrane from its neutral position, rather than directly measuring gravitational effects.
2Measurement precision
If pressure monitoring method is used to deduce propellant volume, then measurement can be performed in zero gravity, but narrow pressure range results in unacceptable measurement error
Solution Approach 1:
The patent replaces pressure-based thermodynamic deduction with laser ranging measurement. Instead of monitoring pressure changes to infer propellant volume, the system directly measures the physical position of the propellant membrane using laser time-of-flight, providing accurate measurements across the full propellant consumption range without relying on narrow pressure variations.
Solution Approach 2:
The patent changes the measurement parameter from pressure (which has a narrow operational range) to laser time-of-flight distance (which provides a wide measurement range). By measuring the physical displacement of the membrane from its neutral position, the system achieves high precision across the entire propellant depletion cycle from 100% to 0% remaining.
3Device complexity
If bookkeeping approach is used to calculate propellant mass, then no additional hardware is needed, but temperature and pressure uncertainties lead to cumulative errors over operational life
Solution Approach 1:
The patent implements a self-measuring system where the laser ranging device continuously and autonomously measures the actual propellant membrane position. This eliminates the need for manual bookkeeping and external temperature/pressure data, as the system directly determines propellant mass through physical measurement, automatically compensating for environmental variations.
Solution Approach 2:
The patent replaces the computational bookkeeping method with a direct physical measurement system. Instead of calculating propellant mass by subtracting estimated consumed amounts from initial load, the laser ranging device directly measures the current propellant mass through membrane position, eliminating cumulative errors from temperature and pressure uncertainties.
4Device complexity
If bookkeeping method is used to track propellant consumption, then implementation is simple, but incapable of accurately accounting for propellant leakage leading to erroneous end of life predictions
Solution Approach 1:
The laser ranging measurement system continuously and autonomously monitors the actual propellant mass, automatically detecting any discrepancies caused by leakage. The system compares measured mass against expected consumption based on thruster operations, identifying unaccounted mass loss from leakage without requiring complex additional sensors or manual intervention.
Solution Approach 2:
The patent implements a feedback mechanism where the laser ranging device continuously provides actual propellant mass measurements to the control system. This feedback loop enables real-time detection of propellant leakage by comparing measured mass with predicted consumption, allowing the system to adjust end-of-life predictions and alert operators to anomalies.
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 approach provides accurate propellant content and center of gravity calculations, minimizing User Range Error and extending mission lifetimes, while reducing complexity and costs by eliminating the need for additional equipment and accounting for potential propellant leakage.
Implementation Method 1
a ranging device coupled to an interior of a propellant tank of the spacecraft, wherein the ranging device is configured to receive a ranging echo signal to facilitate determining a location of a membrane within the propellant tank
Data Source
AI summary
A system for determining a propellant content and a center of gravity in a three-axis stabilized spacecraft includes a ranging device that is coupled to an interior of a propellant tank of the spacecraft. The ranging device is configured to receive a ranging echo to facilitate determining a location of a membrane within the propellant tank.