Rocket Motor Classification via Exhaust Plume Radiance Spectral Analysis
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Solution Overview
Problem
Current methods for real-time or near real-time classification and identification of solid propellant rockets are limited by the accuracy of radar-based ballistic trajectory estimation and the high cost and daylight limitations of high-resolution optical imagers for visible band detection.
Innovation Solution
Detecting and processing the optical radiance of the rocket exhaust plume to extract a motor signature based on the frequency of the dominant mode, which corresponds to the length or sound velocity to length ratio of the rocket motor, allowing for classification or identification without requiring a high-resolution image.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If radar-based ballistic trajectory estimation is used for rocket classification, then the system can operate in all weather conditions and provide real-time tracking, but the classification accuracy is limited and latency is increased due to the need to estimate trajectory over flight portions
Solution Approach 1:
The patent extracts the classification problem from the complex ballistic trajectory estimation process. Instead of relying on radar to track and estimate the entire flight trajectory for classification, the system extracts only the exhaust plume optical radiance signal and processes it directly to determine rocket type, eliminating the time-consuming trajectory estimation step while improving accuracy through direct signature analysis
Solution Approach 2:
The patent replaces the mechanical/radar-based trajectory estimation system with an optical sensing and signal processing system. Instead of using radar waves and computational trajectory modeling, the system uses optical detectors to capture exhaust plume radiance and applies spectral analysis to directly identify rocket characteristics, achieving both faster response and higher accuracy
2Measurement precision
If high-resolution optical imagers in the visible band are used for rocket detection, then spatial information for classification can be obtained, but the system is limited to daylight operation only
Solution Approach 1:
The patent changes the operational parameter from visible light detection to infrared detection. By detecting thermal radiation in the infrared band rather than reflected visible light, the system maintains high measurement precision for exhaust plume characterization while gaining the ability to operate continuously regardless of daylight conditions, as infrared radiation from hot exhaust is detectable at all times
Solution Approach 2:
The patent substitutes visible band optical imaging with infrared optical sensing. Instead of using pixelated imagers that capture spatial information in the visible spectrum (requiring daylight), the system uses infrared detectors to capture thermal radiation from the exhaust plume, enabling operation in all lighting conditions while still providing sufficient information for accurate rocket classification
3Adaptability or versatility
If high-resolution optical imagers in the IR band are used for rocket detection, then operation can continue in low light conditions, but the cost of the imager increases significantly
Solution Approach 1:
The patent extracts only the essential information needed for classification from the exhaust plume - specifically the optical radiance signal characteristics and spectral features - rather than requiring full high-resolution spatial imaging. This extraction approach allows the use of lower-cost infrared detectors that capture radiance intensity and temporal variations without the need for expensive high-resolution IR camera systems
Solution Approach 2:
The patent applies partial action by detecting only the optical radiance signal from the exhaust plume without requiring complete spatial resolution. By focusing on the temporal and spectral characteristics of the radiance signal rather than full spatial imaging, the system achieves the necessary classification capability with less expensive infrared detectors, reducing cost while maintaining operational flexibility
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 enables accurate and rapid classification or identification of rockets, improving the estimation of impact or firing points by augmenting radar systems with motor length or sound velocity to length ratio data, and can operate across multiple spectral bands, including visible, IR, and UV.
Implementation Method 1
the optical radiance of the rocket motor exhaust plume is collected over a field of view, sensed and converted to an electrical signal
Data Source
AI summary
Pressure variations within a solid propellant rocket motor produce like variations in the optical radiance of the motor exhaust plume. The periodicity of the variation is related to the length L of the rocket motor or speed of sound in the rocket motor combustion chamber to length ratio a/L. The optical radiance is collected and converted to electrical signals that are sampled at or above the Nyquist rate. An array of single-pixel photo detectors is well suited to provide amplitude data at high sample rates. The sampled data from the one or more detectors is assembled to form a high fidelity time sequence. A window of sampled data is processed to form a signal frequency spectrum. The mode structure in the frequency spectrum is related to the rocket motor length or speed of sound in the rocket motor chamber to length ratio. The rocket motor length or speed of sound to length ratio is used alone or in combination with other information to either classify or identify the rocket motor.