Vertically Ejecting Shape Memory Alloy based Flat Pack Hold Down and Release Mechanism

Shape Memory Alloys (SMAs) are increasingly being adopted in aerospace and space systems due to their high force-to-weight ratio, unique thermo-mechanical response, and large recoverable strains. Their availability in various geometric forms—such as wires, tubes, and strips—also makes them easily integrable in different mechanisms. With the combination of input (stimuli) and output (motion) in one single body, SMAs reduce the number of parts and the need for complex linkages, thereby making the mechanisms simpler, more lightweight, and inherently more reliable. Leveraging these attributes, SMA-based Hold-Down and Release Mechanisms (HDRMs) have emerged as a promising alternative to traditional pyrotechnic devices, which often suffer from high release shocks (>1000 g), debris issues, and single-use limitations.

In this work, an SMA-based pin ejector HDRM with flat geometry has been designed, fabricated, and tested. The actuator features a flat design, rather than the traditional cylindrical configuration, to facilitate integration in low-height spaces, such as between solar panels. The HDRM thus has ejection perpendicular to the largest surface. Metal parts were fabricated from aluminum and were MIL-grade anodized to prevent jamming in sub-zero and high-vibration environments. Different ground tests were conducted to determine the actuation time at different temperatures, the minimum/ maximum fire currents, and the actuation time at various currents.

The results demonstrate that the flat, compact, debris-free, low-shock design is a promising candidate for aerospace and space systems with sensitive electronics and payloads.