175 Cryogenic Temperature Testing of NEA Fuse Wire Mechanism 

Edwin Vega and Geoff Kaczynski 

Abstract 

NEA has over 10 years of continuous innovation in the field of space rated non-pyrotechnic release mechanisms. At the heart of our technology is the NEA patented Fuse Wire Assembly (FWA). NEA utilizes our patented FWA design across all our product lines to initiate the release operation of our restraint and release devices and our battery bypass switches. Most recently, as part of a deep space mission, cryogenic temperature testing was performed on our FWA down at 18° Kelvin (K). The testing discussed in this paper validates that the FWA, which is a critical component of the overall mechanism design, is robust enough to reliably operate in space at extremely low power levels and temperatures. In this paper, NEA will describe the cryogenic temperature tests along with test results. As the space community explores further into our solar system and beyond, this validation testing of our product enables new found confidence that existing technologies can be used for fielding deployable structure in deep space.    Introduction   All major space agencies and organizations are funding missions for spacecrafts to explore our solar system and beyond. As soon as a spacecraft leaves the earth orbiting environment, it experiences extreme cold temperatures with the background radiation of the universe. Today’s missions require several staged deployments during multiple phases of their missions, such as entering orbit, decent, landing and deployment of instruments. For today’s missions, the restraint and release device must be proven to operate in deep space cryogenic temperatures to ensure mission success.  The NEA release mechanism is used to provide restraint and release functions for critical deployment operations on spacecraft such as solar arrays, antennas, radiators and payloads after launch. The FWA in the release mechanism is a critical element. Each release mechanism’s FWA is single or redundantly initiated. Actuation time variation between multiple mechanisms FWA is less than 10 milliseconds when a nominal firing pulse is applied to all units simultaneously.   

Basic Design 

The patented NEA FWA design is simplistic in operation and design. Upon receiving a specified electrical pulse of 1.2 amps or greater, the fuse wire breaks starting the release sequence of the preloaded release rod. The shock induced by release of the tensile load is typically less than 300 G’s. Each FWA is fully refurbished after each ground-based test actuation. The principle of operation is as follows:   A fuse wire is wrapped between two electric terminals.    A process controlled load is placed on the fuse wire.    When current is applied via the spacecraft firing system, the fuse wire heats lowering its yield  strength.    The fuse wire yields once the applied load exceeds the strength of the fuse wire.     Breaking of the fuse wire allows the release system to activate and allow deployment.                                                                 * NEA Electronics Inc., Moorpark, CA  

Proceedings of the 41st Aerospace Mechanisms Symposium, Jet Propulsion Laboratory, May 16-18, 2012