Space station Zero-Propellant Maneuver guidance trajectories compared to eigenaxis

The zero-propellant maneuver (ZPM) guidance concept has been used on November 5, 2006, and March 3, 2007 to reorient the International Space Station (ISS) 90 deg and 180 deg respectively with control moment gyroscopes (CMGs) without using any propellant. It will be shown that there are multiple ZPM trajectories that can perform the maneuver non- propulsively. Performing the same maneuver using an eigenaxis path would saturate the CMGs, requiring thrusters to regain attitude control. A condition is derived to explain why the CMGs saturate along the eigenaxis path. Flight results from the two ZPM demonstrations are presented.