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Donald Ellison

Publications and source records attributed to Donald Ellison.

3 records
All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

Analytical Partial Derivatives of the Q-Law Guidance Algorithm

One method of producing low-thrust trajectories is the closed-loop Q-Law guidance algorithm. This work wraps Q-Law inside a nonlinear programming problem to search for locally optimal gain combinations and enforce nonlinear constraints on the initial state. Gradient-based trajectory optimization has been shown to benefit greatly when analytical partial derivatives are supplied to the optimizer. This paper presents the Q-Law optimization problem setup and derives the Q-Law thrust vector partial derivatives for the State Transition Matrix required by standard nonlinear optimization software.

Jackson L Shannon↗
NASA NTRSDate not supplied

Exploration of Low-Thrust Lunar Swingby Escape Trajectories

Spiral escape trajectories enable a spacecraft to escape Earth’s gravity and travel into inter-planetary space under its own power. This analysis demonstrates how to design spiral escape trajectories that leverage single and double Lunar gravity assists and compares the effectiveness of each trajectory type. The trajectories are constructed by combining backwards propagated Q-Law and a perturbed Sims-Flanagan transcription to design the spiral and interplanetary phases, respectively. We demonstrate that these mission types result in significant propellant savings when compared to a conventional, no Lunar swingby spiral escape, and are highly beneficial for the interplanetary rideshare mission concept.

Jackson L Shannon↗