A Non-Pyrotechnic Heavy-Load Hold Down Release Mechanism for Space Gimbals

Continuously rotating gimbals for scanning purposes are widely used in space applications. For high-precision gimbals, it is essential to lock the gimbal before launch and unlock it on orbit. This kind of gimbal puts forward the need for hold down release mechanisms that are able to clear the gap between the rotating and fixed parts at release. Existing technologies either lack the function of gap avoidance after separation or rely more or less on the elastic deformation of the structure or limited spring forces for unlocking, which are either unreliable or complicated. To address this problem, this paper presents the design of a novel non-pyrotechnic heavy-load hold down release mechanism (HDRM) based on shape memory alloy actuator. The proposed HDRM is shock-free and capable of clearing an axial gap of 8 mm for safe rotating at release. The structure and operational principle of the proposed design are straightforward. Detailed tests show the proposed HDRM may withstand a maximum external force of 50 KN with relatively high stiffness under 15 KN of preload, indicating a better performance than existing products. The HDRM demonstrates its promising usage as an alternative to traditional pyrotechnic and non-pyrotechnic HDRMs.