Design of a Sensor System and Software to Predict Aero-Thermal Ablation

Photo of Rob Fromm, Christof Van Der Schyf, and TJ Weaver Students: Rob Fromm, Christof Van Der Schyf, and TJ Weaver

Sponsor: Los Alamos National Laboratory

Date: Spring 2011

Requirements:
The primary concern is that the sensor did not structurally compromise the tiles by drilling or cutting into them. The sensor also is required to have an overall accuracy of ±5%. Expenditures related to the project were not to exceed $5,000.

Problem:
Heat shielding tiles on intercontinental ballistic missiles become thinner over the course of missile flight. This causes the aerodynamic properties of the craft to change. Without continuous data on the tiles' dimensions, the changes lead to reduced flight stability and decreased guidance system effectiveness. To address this, a sensor was designed to take real-time thickness measurements of individual heat tiles.

Solution:
The team's solution involved an ultrasonic transducer coupled with a thermal probe placed on the back surface of individual heat tiles. The transducer emits acoustic signals and receives echoes off the front surface of the tile. The thermal probe takes temperature readings and estimates the thermal profile of the material. Coupling "speed of sound vs. temperature" curves with the acoustic and thermal data, a thickness value is calculated. The "speed of sound vs. temperature" curve was experimentally determined by the team, and the thermal characterization was developed from boundary condition estimates.

Photo related to Design of a Sensor System and Software to Predict Aero-Thermal Ablation project
Joomla SEF URLs by Artio