A new method for optimizing yaw attitude maneuvers on the International Space Station (ISS) was developed. Docking and undocking operations often require 180° yaw rotations, which are the most common large maneuvers on the ISS. When optimized, some large maneuvers, previously performed using thrusters, could be performed using control moment gyroscopes (CMGs) or with significantly reduced thruster firings. The ability to perform a non-propulsive or low-propulsive 180° yaw maneuver on the ISS has been proven through the zero propellant maneuver (ZPM) and the optimal propellant maneuver (OPM). The ZPM and OPM were created by Draper Laboratory using the computational approach. Each maneuver is unique, and can only be calculated on the ground because significant computer resources are needed for the calculations.

In this innovation, a simplified analytical solution has been found for yaw maneuver optimization. Equations describing attitude and rate maneuver profiles have been obtained. In the suggested optimized case, the torques are significantly reduced, which reduces or eliminates thruster firings, saves an expensive propellant, reduces loads and contamination of the structure, and extends vehicle life. The obtained trajectories and the propellant consumption values have a good match with the optimal trajectories obtained using the existing computational method. The proposed analytical solution does not require a lot of computer resources and, therefore, can be implemented in the onboard software, thus making the maneuver automatic and significantly simplifying operations. This is the major benefit of the proposed method with respect to the existing computational approach. The proposed analytical solution is universal and can also be used for other orbiting space vehicles.

This work was done by Tatiana Dobrinskaya of United Space Alliance for Johnson Space Center. For further information, contact the JSC Technology Transfer Office at (281) 483-3809. MSC-25656-1

NASA Tech Briefs Magazine

This article first appeared in the March, 2016 issue of NASA Tech Briefs Magazine.

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