Reduced Gravity Control of Small Spacecraft using Control Moment Gyroscopes and On-Off Thrusters



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46th International Conference on Environmental Systems


Large spacecraft like the International Space Station have long benefited from the use of control moment gyroscopes (CMGs) as propellantless angular momentum devices, yet the large size of traditional CMGs generally prevent their application to small spacecraft platforms. Recent advances in the miniaturization of CMGs have motivated Draper and MIT to investigate the use of CMGs as attitude actuators for small spacecraft and for astronaut maneuvering units derived from NASA’s SAFER system. On-off thrusters typical in reaction control systems produce fixed forces and torques over variable on-times, and pointing precision is limited by a deadband arising from minimum torque magnitude and duration. CMGs, by contrast, produce variable torques by gimbaling a fixed-rate flywheel; small gimbal rates correspond to small torques while large gimbal rates correspond to large torques. This wider range of torques can enable smaller deadbands (enhanced pointing precision) as well as improved slewing and disturbance rejection. When applied to small spacecraft with moving parts or to astronaut maneuvering systems, CMGs can provide stability without the use of fuel during dynamic operations that would not be possible with traditional thruster reaction control. Microgravity demonstration of thruster and CMG attitude control with the MIT Synchronized Position Hold, Engage, Reorient Experimental Satellites (SPHERES) facility and Honeybee Robotics miniature CMGs was recently conducted aboard NASA’s Reduced Gravity Aircraft in August 2015 (Technology 138-P). CMG torques and SPHERES thruster torques on the same system were compared both in microgravity and in the laboratory. CMGs repeatedly generated both smaller and larger torques than thrusters alone could provide, indicating their capacity to improve control authority in the SPHERES system.


United States
Massachusetts Institute of Technology
ICES403: Extravehicular Activity: Operations
Vienna, Austria
Todd F. Sheerin, Massachusetts Institute of Technology, USA
Jose Gomez, Massachusetts Institute of Technology, USA
Danilo Roascio, Massachusetts Institute of Technology, USA
Jeffrey A. Hoffman, Massachusetts Institute of Technology, USA
The 46th International Conference on Environmental Systems was held in Vienna, Austria, USA on 10 July 2016 through 14 July 2016.


EVA, attitude control, stability, precision pointing, control moment gyroscopes, low gravity astronaut maneuvering unit, service and assembly spacecraft, inspection and maintenance spacecraft, MIT SPHERES, NASA Reduced Gravity Office, Draper Jetpack technology