Experimental Characterization Of Shape Memory Alloy Based Hold Down And Release Mechanism (HDRM)

Abstract

In satellite technology, release mechanisms are crucial for deploying essential components such as solar panels and antennas. While historically depend on pyrotechnic systems, these mechanisms face drawbacks like generating high pyro shock levels, lack of reset capability, and safety hazards. Consequently, there's a growing focus on developing non-pyrotechnic alternatives. This change aims to overcome limitations while enhancing safety, reliability, and efficiency in satellite deployment systems, powerful innovation towards more advanced release mechanisms for future missions. This Project reports a development and experimental characterization of a shape memory alloy (SMA) based Hold-Down and Release Mechanism (HDRM) designed for deployable space telescopes. The HDRM utilizes SMA technology to restrain the telescope during launch and release it afterwards. The SMA cylinder, constructed from Nitinol, is initially compressed. Upon heating, it elongates, producing sufficient force to fracture the notched bolt in tension and consequently release the joint. This transformation converts the HDRM from a rigid joint to a releasing mechanism. The experimental setup involves measuring the force-displacement characteristics of the SMA actuator and the breaking strength of the notched fasteners. Results indicate that the SMA actuator can generate sufficient force to break the fasteners. Bolt preload measurements are crucial to ensure proper functioning, with strain gauges used as an alternative to costly load sensors. A miniature model of the HDRM is developed, incorporating strain-based bolt preload measurement and temperature monitoring. Finally, successful tests were carried out using an experimental configuration comprising the SMA actuator, bolt, and associated components. These tests effectively demonstrated the potential of utilizing these alloys for deployment devices.