Neutral-Axis Springs for Thin-Wall Integral Boom Hinges

A document proposes the use of neutral- axis springs to augment the unfolding torques of hinges that are integral parts of thin-wall composite-material booms used to deploy scientific instruments from spacecraft. A spring according to the proposal would most likely be made of metal and could be either flat or curved in the manner of a measuring tape. Under the unfolded, straightboom condition, each spring would lie along the neutral axis of a boom. The spring would be connected to the boom by two supports at fixed locations on the boom. The spring would be fixed to one of the supports and would be free to slide through the other support. The width, thickness, and material of the spring would be chosen to tailor the spring stiffness to provide the desired torque margin to assist in deployment of the boom. The spring would also contribute to the stiffness of the boom against bending and torsion, and could contribute some damping that would help suppress unwanted vibrations caused by the deployment process or by external disturbances.