Shape Memory Alloy Actuator for the DORA Deployable Telescope

The future of spaceborne observations increasingly relies on reducing payload size while maintaining high-performance standards. The miniaturisation of satellites is strongly dependent on advanced deployment technologies for satellite appendages, enabling significant volume reduction and, consequently, lowering the mission costs. As a result, there is significant interest in developing actuators and deployment devices to improve the compactness of deployable structures. Current advancements in the field are focused on passive deployment methods, such as elastic elements and shape control devices, as they offer simpler and more reliable alternatives to conventional electric actuators that can introduce higher complexity, deterioration and failure risks. This work describes the design of a Shape Memory Alloy (SMA) actuator for the deployment mechanism of DORA (Deployable Optics for Remote Sensing Applications), a Cassegrain telescope framed in a mission for Earth observation from low Earth orbit (LEO) for monitoring emissions and diffusion of pollutants. The need to replace previously selected linear electric actuators derives from the possibility of enhancing the mechanism's reliability by simultaneously reducing the required resources, either in terms of mass or power. The proposed design exploits the Shape Memory Effect (SME) of Nitinol wires actuated through the selfheating dissipation. The feasibility design of the intended SMA technology is described, and the wire's characteristics are identified to guarantee deployment and fulfil available size and power constraints. Performed testing activity is presented as well, mandatory to assess the actuator's performance under constant stress conditions and to validate the proposed design by deploying a mockup of the telescope.