Device Concept
Magnetostrictive crystals of terbium and dysprosium as developed by Arthur Clark (a consultant to this task) and his associates at the Naval Surface Warfare Center provide high force motion at long strokes.  The working stroke is around half a percent of crystal length, with a typical actuator crystal length of two centimeters.  The strokes are tunable based on the ratio of TbDy in the crystal. Generally longest strokes are available at temperatures below those of liquid nitrogen, which is also the temperature range of greatest interest for heat switch applications.  The switch shown below is a power-on-to-close configuration.  Other configurations are possible, including the introduction of a superconducting flux tube, to provide a bi-stable switch that will remain in either position without power.  The switch was developed through the level of a simple proof of concept model.

The Inventors and Developers

Concept & Design:        Robert Chave
Device Development:   Robert Ottocan, Lund University and JPL

Robert Ottocan used this work for his master thesis at Lund University, reference number CODEN:LUTMDN/(TMMV-5138)/1-32/199

NASA Awards
NASA New Technology Award, NPO-20274: "Heat Switch for Cryogenic Application, with Very Rapid Closure Time, and High Open Position Thermal Isolation to 15 Microwatts per Degree Kelvin." 1998 NASA New Technology Award, NPO-20502/0099b: "Flux Tube Drive for Magnetostrictive Heat Switch" 1999
 

Patent Claims
United States Patent entitled " Magnetostrictive Actuation", Serial Number 09/183,387, R. Chave, C. Lindensmith, J. Dooley, B. Fultz, and M. Birsan, Application filed, Oct. 29, 1998 claiming the benefit of U.S. Provisional Application No. 60/063, 991, filed Oct.  29, 1997