Material damage system and method for determining same
Inventors
Assignees
National Aeronautics and Space Administration NASA
Publication Number
US-9766053-B1
Publication Date
2017-09-19
Expiration Date
2031-11-21
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Abstract
A system and method for determining a change in a thickness and temperature of a surface of a material are disclosed herein. The system and the method are usable in a thermal protection system of a space vehicle, such as an aeroshell of a space vehicle. The system and method may incorporate micro electric sensors arranged in a ladder network and capacitor strip sensors. Corrosion or ablation causes a change in an electrical property of the sensors. An amount of or rate of the corrosion or the ablation and a temperature of the material is determined based on the change of the electrical property of the sensors.
Core Innovation
The invention discloses a system and method for determining changes in the thickness and temperature of a surface of a susceptible material. This system involves using micro electric sensors arranged in configurations such as ladder networks and capacitor strips embedded within the material. Corrosion, ablation or other forms of damage cause changes in the electrical properties of these sensors, which are measured to determine both the amount or rate of material degradation and the temperature of the material.
The disclosed system and method address the problems in existing approaches for monitoring damage to materials, particularly in thermal protection systems of space vehicles. Current instrumentation relies on manually placed thermocouples and resistors embedded in plugs inserted into drilled holes in the protective material. These plugs are time-consuming to manufacture, problematic to integrate, and may create structural discontinuities leading to enhanced ablation and risk of plug loss during reentry, thereby compromising vehicle safety. Additionally, the limited number and placement of sensors hinder high resolution, large area profiling of temperature gradients and ablation rates.
The invention overcomes these limitations by embedding arrays of micro-scale sensors directly within the susceptible material, allowing real-time or near real-time measurement of temperature and thickness changes over large surface areas. The sensors include temperature-sensitive resistor ladder networks and temperature-independent capacitor strips that change electrical properties as the material ablates or corrodes. This configuration enables tomographic imaging of temperature and recession rates, improving monitoring capabilities and enhancing safety and effectiveness for applications such as space vehicle thermal protection systems.
Claims Coverage
The patent includes three independent claims, which cover a system for measuring thickness and temperature changes in a susceptible material, methods for these measurements, and embedding multiple sensors for assessing temperature and material degradation.
System for sensing thickness and temperature changes using first and second sensors with distinct electrical temperature sensitivities
The system comprises a material susceptible to corrosion or ablation with first and second sensors extending along its thickness, where the first sensor has an electrical property that changes with temperature and the second sensor remains constant with temperature changes. An electrical circuit monitors changes in electrical properties, and a processor determines both material thickness and temperature based on sensor measurements. The second sensor's capacitance varies with length changes.
Method for determining temperature and thickness of a susceptible material via micro electric sensors
Steps include positioning a first micro electric sensor and a second micro electric sensor within a susceptible material, applying current or voltage, exposing the material to a substance causing temperature and thickness changes, and determining temperature and thickness from electrical properties of the sensors, with the first sensor's electrical property more temperature-sensitive than the second. The second sensor's capacitance changes with length.
Method for embedding multiple sensors to determine temperature and thickness changes
Embedding a plurality of sensors including at least a first ladder sensor, a second ladder sensor with more rungs and less temperature-sensitive components than the first, and a capacitor strip. Applying current or voltage, exposing the material to temperature changes, ablating the material, and determining material temperature based on changes in electrical properties of the first and second ladder sensors, and thickness based on changes in the capacitor strip and the second ladder sensor.
The claims collectively cover systems and methods utilizing sensors with differing temperature sensitivities embedded in susceptible materials to detect and distinguish between thickness changes due to ablation or corrosion and temperature changes, employing electrical measurement techniques and processing to provide accurate characterization of material condition.
Stated Advantages
Reduces time and cost associated with manufacturing and integrating sensors compared to manual plug insertion.
Eliminates structural discontinuities and potential failure points caused by glued plugs, enhancing safety during material ablation.
Enables high resolution, large area measurement and tomographic profiling of material thickness and temperature.
Allows deployment of numerous micro-scale sensors to provide detailed, real-time monitoring of temperature gradients and ablation rates.
Compatible with materials used in thermal protection systems, enabling improved monitoring and optimization of protective materials in aerospace applications.
Documented Applications
Thermal protection systems of space vehicles, specifically aeroshell heat shields used during atmospheric re-entry.
Monitoring corrosion, erosion, and ablation in various industries where material surface damage and temperature measurement are necessary.
Braking materials of vehicles and fluid conduits, as examples of susceptible materials for the sensor system.
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