Electrospray Propulsion Performance for Cubesat Missions

Abstract

Motivated by a proposed mission to construct, from multiple CubeSats, a large aperture radio telescope behind the Moon to detect emissions from exoplanets, and the ongoing development of electrospray propulsion (ESP) that promises to meet the needs of SmallSats, efficient Earth to Moon transfer options are identified and compared as a step in characterizing ESP performance. ESP operates at constant input power and has two thrust modes: a droplet mode with higher thrust and lower specific impulse, and an ion mode with lower thrust and higher specific impulse. Using the (patched) circular restricted 3-body model augmented for the ESP thrust, optimal transfers considering time and mass are computed for each of these modes. All the transfers start from a circular parking orbit with an initial velocity impulse provided by the launch vehicle and involve riding or shadowing invariant manifolds of unstable periodic orbits to reduce propellant consumption. A low-energy transfer using a long-duration ion-mode low-thrust assist while the CubeSat shadows the stable and unstable manifolds of a Sun-Earth libration orbit emerges as an attractive option.