A Modal-Based Measurement of Adhesion Impulses in Space Mechanisms

The adhesion impulses generated at the separation of metallic surfaces in vacuum have a significant impact on the performance of launch-lock and release mechanisms in space systems and, therefore, on the success of a space mission. The testing approach presented in this paper features a suspended plate, with a gold coated insert, that is put in contact and loaded with an actuator representing the release mechanism used in the LISA Pathfinder (LPF) mission. At the retraction of the release mechanism, the adhesive bonds are stretched until failure, transferring an impulse to the plate. The adhesion impulse characterization technique presented here uses the multimode response of the plate as measurement principle. Each mode is treated as an independent dynamic system, whose vibrations are influenced by the adhesion impulse. The technique described in this paper exploits the redundancy introduced by multiple vibration modes to estimate the effect of an array of loading directions on the adhesion impulse developed at the retraction of the release mechanism.