Measurement of Metallic Adhesion Force-to-Elongation Profile under High Separation-Rate Conditions

The Laser Interferometer Space Antenna (LISA) is a space mission, which will reveal gravitational waves. Some of its key technologies will be tested by means of the LISA Pathfinder mission, in order to reduce the risk correlated with LISA challenging requirements. Among its more critical subsystems, the Gravitational Reference Sensor (GRS) has been designed to host a 2kg Au-Pt cubic Test Mass (TM) in free-fall, with the tightest requirement ever set on the purity of a geodesic trajectory. The GRS shows a specific criticality related to the need to constrain the TM during the spacecraft launch and subsequently inject it in the geodesic, breaking the adhesion arisen at the contact surfaces with its mechanical constraints. The injection strategy is dynamic: by means of a quick retraction of the release-dedicated holding tips the TM is detached from the constraint, relying on its inertia. The experiment realized through the Transferred Momentum Measurement Facility reproduces the injection of the LISA TM into geodesic, aiming at quantifying the residual velocity of the mass after separation from the release tip. In the field of dynamic behaviour of materials, the TM injection constitutes a novel area of research, where the strength of metallic adhesion is explored under high separation-rate conditions.