Acoustic levitation at high temperatures in the microgravity of space

Acoustic levitation of a small specimen is obtained in the energy well produced by a single axis arrangement consisting of a sound source and a small acoustic reflector. At high temperatures, the acoustic forces are generally insufficient to levitate a specimen except in the microgravity environment available in space. A single axis acoustic levitator (SAAL) has been built to levitate a specimen inside a high‐temperature furnace where it may be heated, melted, cooled, and solidified while being positioned without physical contact. The acoustic field configuration in such a containerless processing device has been analyzed and the expected levitation or positioning forces are calculated for the specific case of the NASA‐SAAL experimental hardware as flown on the Space Shuttle on the STS‐61A mission. This experiment successfully levitated and processed three samples at temperatures from 600 °C to 1550 °C. Experimental data are presented and the results compared with those predicted. [Work supported by NASA.]