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Operator evaluation of a Mobility-Augmenting Jetpack with Integrated control-moment gyroscopes

While the direction for human space exploration may not be currently well-defined, there are many potential missions that could benefit from an astronaut mobility unit providing six-degree-of-freedom control during extravehicular activities (EVAs). The attitude-control system (ACS) for the Jetpack device currently under development at NASA Johnson Space Center is based on the Simplified Aid for EVA Rescue (SAFER), which uses gas thrusters for both attitude control and translation. The proposed astronaut mobility unit incorporates control concepts optimized to support EVA tasks and adds control-moment gyroscopes (CMGs) to the current Jetpack system. The control architecture of this Mobility-Augmenting Jetpack with Integrated CMGs (MAJIC) considers a concept of operations that includes scenarios such as surface sample collection, equipment deployment, satellite servicing, crewmember rescue, and contingency EVA missions at objects lacking built-in handholds or foot restraints. Momentum desaturation logic is incorporated into the MAJIC control algorithm and the CMGs are optimally sized using a Monte-Carlo simulation approach. The resulting ACS design is evaluated by test subjects in comparison to an idealized CMG ACS and the baseline Jetpack thrusters-only design using a human-in-the-loop, real-time, virtual-reality simulation. Results demonstrate that while the initial CMG size is too small for practical use during EVA missions, a design incorporating a larger CMG array with sufficient angular-momentum capability significantly reduces undesired compensating torques on the astronaut while conserving onboard fuel and extending the length of EVA missions.