A DYNAMIC TECHNIQUE FOR THERMOPHYSICAL MEASUREMENTS AT HIGH-TEMPERATURES IN A MICROGRAVITY ENVIRONMENT

Millisecond-resolution dynamic techniques for thermophysical measurements, when utilized in the laboratory, are limited to the study of materials in their solid phase because the specimen becomes geometrically unstable during melting and collapses, due (at least in part) to the influence of gravity. Therefore, a millisecond-resolution dynamic technique is being developed for use in a microgravity environment in order to extend accurate measurements of selected thermophysical properties of electrically conducting refractory materials to temperatures above their melting point. The basic method involves heating the specimen resistively from ambient temperature to temperatures above its melting point in about 1 s by passing an electrical current pulse through it, while simultaneously recording the pertinent experimental quantities. A compact pulse-heating system, suitable for microgravity simulations with NASA's KC-135 aircraft, has been constructed and initial experiments have been performed to study the geometrical stability of rapidly melting specimens. Preliminary results show that rod-shaped specimens can be successfully pulseheated into their liquid phase. © 1990 Plenum Publishing Corporation.