Characterizing Electroadhesion in Vacuum: Experimental and Simulation Frameworks for Space Docking

Electroadhesion(EA) is a promising mechanism for soft docking, detumbling, and proximity operations in space, but its performance under vacuum and space-relevant contact conditions remains poorly quantified. This paper presents a combined experimental and simulation framework to evaluate EA pad behavior in both atmospheric and vacuum environments. Two vacuum-compatible EA pad designs are investigated: a flexible printed circuit (FPC) pad using Kapton polyimide film and a bi-layer-coated pad combining a polyimide primer with a high-permittivity polyurethane topcoat. Finite-element simulations in COMSOL Multiphysics are used to estimate electroadhesive normal forces and explore parametric sensitivities, while complementary experiments are conducted using two testbeds. Shear and normal force measurements, performed by InOrbit Aerospace, quantify achievable EA forces in atmospheric conditions, while a fully vacuum-compatible rotator-stage setup enables qualitative comparison of adhesion performance between atmospheric and vacuum environments. The results show that surface conformity and contact mechanics dominate EA performance and introduce substantial variability in observed electroadhesive forces. Vacuum testing consistently improves repeatability and achievable adhesion, likely due to the elimination of humidity-related effects, but also reveals long-lived dielectric polarization of the EA pad complicating deadhesion. Both tested pad designs withstand significantly higher voltages than commonly reported in the literature, enabling higher forces (peak of 18 N shear force at 6 kV); measured normal forces agree in order of magnitude with simulations, but simulations predict higher dependence on applied voltage. Shear forces are observed to be significantly stronger than normal forces for both pad designs. The novel bi-layer coating does not outperform the monolayer coated pads as predicted by previous computational studies. Overall, these findings highlight key challenges for electroadhesion deployment in space, most notably the need for reliable and controllable deadhesion mechanisms and the implications of operating at higher voltages. At the same time, the results indicate that vacuum operation improves adhesion repeatability and robustness relative to atmospheric testing, motivating more systematic and quantitative electroadhesion characterization under space-relevant vacuum conditions.