Using telescopic deployable structures can significantly reduce the large empty volume taken up by some types of optical payloads, thereby positively impacting launch vehicle options and mission costs. However, these structures add complexity with the need for a deployment mechanism, making system reliability crucial. The goal was to develop a simple, passive deployment mechanism to minimize added complexities and ensure deployment reliability. Previous work addressed the viability of wire-driven concepts in telescopic optical barrels for Cassegrain-type telescopes, where the optical barrel supports the secondary mirror at one end and encloses the primary mirror at the other end. This concept was also applied to optical baffles, with the focus on nanosatellite and CubeSat applications. Here the work has been extended to larger optical instruments, where the baffle is required to extend to approximately one meter in length, with a stowed length being approximately a quarter of the deployed length. The motorization is produced by a constant torque spring which winds a system of wires that drives the segments of the telescopic assembly. To control and reduce the speed of the deployment a damper component has been developed and integrated in the mechanism. The deployment damper is customized and sized in accordance with the environmental conditions and multiple measurements are taken to verify its compliance with the system-level requirements. The hold-down and release mechanism (HDRM) utilized to constrain the stowed baffle during launch is a burn-wire system. This enabled multiple restraining points which distribute the reaction forces avoiding large loads and stress, coupled with simplicity and reliability. The tension in the constraining wire is maintained by linear springs and is cut by a Kanthal hot wire in a way that ensures increased reliability of the HDRM. FEA was performed to drive the design of the structure and ensure requirements, such as deployed and stowed natural frequency and acceptable stress levels, were met. The designs which were manufactured ranged from a 3-segment 1/3-scale to full-size engineering and qualification models which were extensively tested. A gravity offload mechanism has been implemented to independently support the various segments, enabling the terrestrial simulation of microgravity deployment. The tests on the full-scale models enabled tuning of the transmission ratio and the amount of damping in the deployment mechanism required to produce a smooth translation, while keeping the final shock at the end of the deployment (i.e. when the segments reach their stops) within an acceptable level.
Aglietti et al. (Sun,) studied this question.