Control Seminar

Rendezvous and Relative Motion Guidance for Space Situational Awareness

Morgan BaldwinDr.U.S. Air Force Research Laboratory

Since the beginning of manned space flight, the United States has chosen a manual course of action concerning rendezvous and relative motion. This approach enables flexibility for a given mission and eliminates the need for redundancy and complexity. With the increasing number of space objects, autonomous operations are needed to effectively, both in terms of cost and efficiency, complete certain space operations, including capture, servicing, monitoring, and inspection. An autonomous system is expensive during development, but the system can be standardized and cost benefits are achieved through the system's lifecycle.
Currently, guidance solutions are determined by ground operators employing impulsive models for spacecraft propulsion capability; only after lengthy analysis are these solutions uploaded to the spacecraft and implemented using closed-loop trajectory control. Spacecraft performing rendezvous maneuvers invariably have finite thrust limitations, and the actual burn(s) required to achieve a desired velocity change (Â^†V) are necessarily finite-time maneuvers during which the position change can have considerable effects on the terminal conditions of the vehicle. Specifically, the trajectory resulting from this finite-duration thruster burn can have significant position and/or velocity departures from the trajectory designed using impulsive-burn models. For rendezvous and relative motion missions where spacecraft separation distances are small, these errors can result in an unacceptable safety hazard. Therefore, while analyses based on impulsive velocity assumption serve well for purposes of feasibility studies and preliminary planning, they are incomplete with regard to onboard use.
This talk will present recent research on rendezvous and relative motion guidance. This includes far-field, finite-burn guidance, which is formulated using free-final time minimum fuel optimal control. To solve the far-field rendezvous solution, the engine on time, off time, and direction and magnitude of the thrust vector must be determined such that the deputy vehicle is at the correct position at the end of the maneuver to complete the midfield and relative motion portion of the rendezvous maneuver and meet the chief vehicle. Relative motion guidance will also be discussed. Model Predictive Control with Clohessy-Wiltshire-Hill equations are used to solve the minimum fuel, constant thrust relative motion guidance problem.
The talk will conclude with a brief discussion of the programs and opportunities within Space Vehicles Directorate for collaborations with University students & faculty.

Dr. Morgan Baldwin is a Research Aerospace Engineer in the Guidance, Navigation, & Control Section within the Spacecraft Component Technology Branch of the Space Vehicles Directorate of the U.S. Air Force Research Laboratory located at Kirtland Air Force Base in New Mexico. She received a B.S. from Virginia Tech in both Mathematics and Ocean Engineering in 2005, an M.S. from Iowa State University in 2007 in Applied Mathematics, an M.E. from Iowa State University in 2008 in Aerospace Engineering, and a Ph.D. from Iowa State in 2010 in Aerospace Engineering. Her research interests include navigation, trajectory optimization, and finite-burn guidance.

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