Astronaut-centric analysis of a jetpack with integrated control-moment gyroscopes for enhanced extravehicular activity performance

Abstract

As a stepping-stone towards eventual human exploration of Mars, NASA plans to explore low-gravity objects. Since the surface environments encountered on such missions would limit the independent mobility of astronauts, a maneuvering unit that offers counter reaction forces and torques during movements and tasks will likely be required. The next-generation maneuvering and stability system proposed in this research incorporates control moment gyroscopes (CMGs) into an extravehicular activity (EVA) jetpack device currently being considered at NASA Johnson Space Center (JSC). This Mobility Augmenting Jetpack with Integrated CMGs (MAJIC) system will offer rigid attitude control not previously required for EVA tasks. This research project was designed to: (1) assess EVA task motions, astronaut dynamics, and mission concepts to support the objective comparison of the original jets-only Jetpack system and MAJIC, and (2) analyze the performance of both systems based on user evaluations of the two control configurations. An EVA task list with associated motions and tools was compiled to develop a relevant mission concept of operations that would inform the subsequent research objectives. A method for analyzing astronaut dynamics during these EVA tasks was developed and used to compare system stability of the proposed (CMG-augmented) vs. current (jets-only) control systems. The combined astronaut dynamics and controls models formed a full simulation that was integrated into a Virtual Reality (VR) environment at JSC to offer a platform for two human evaluations comparing the proposed and current control systems. Although computational analyses demonstrated increased attitude stability and decreased fuel consumption consistently across all missions and EVA tasks, results from the user evaluations were mixed. In the preliminary user evaluation, users showed overwhelming preference for MAJIC during worksite EVA tasks that incorporated astronaut motions, but no trend for piloted missions that did not incorporate astronaut motions. The results of the follow-up user evaluation indicate that benefits of MAJIC are more pronounced in certain mission scenarios, including ones in which mass and moment of inertia properties are increased (e.g. when tools are used). Future work should explore these mission scenarios further and continue development of motion capture capabilities to include full-body actuation and contact models within the virtual reality environment.