An Automatic Tree Search Algorithm for the Tisserand Graph

TL;DR

This paper introduces an automated tree search algorithm to efficiently explore the Tisserand graph for gravity-assisted trajectory design, enabling rapid identification of encounter sequences in complex multi-body systems.

Contribution

The paper presents a novel automatic tree search method for the Tisserand graph, improving the efficiency and automation of encounter sequence identification in trajectory planning.

Findings

Successfully validated against existing solutions

Able to handle complex multi-body scenarios

Integrated with trajectory optimization tools

Abstract

The Tisserand graph (TG) is a graphical tool commonly employed in the preliminary design of gravity-assisted trajectories. The TG is a two-dimensional map showing essential orbital information regarding the Keplerian orbits resulting from the close passage by one or more massive bodies, given the magnitude of the hyperbolic excess speed ($v_{\infty}$) and the minimum allowed pericenter height for each passage. Contours of constant $v_{\infty}$ populate the TG. Intersections between contours allow to link consecutive flybys and build sequences of encounters en route to a selected destination. When the number of perturbing bodies is large and many $v_{\infty}$ levels are considered, the identification of all the possible sequences of encounters through the visual inspection of the TG becomes a laborious task. Besides, if the sequences are used as input for a numerical code for trajectory design and optimization, an automated examination of the TG is desirable. This contribution describes an automatic technique to explore the TG and find all the encounter paths. The technique is based on a tree search method, and the intersections between contours are found using the regula-falsi scheme. The method is validated through comparisons with solutions available in the open literature. Examples are given of application to interplanetary mission scenarios, including the coupling with a trajectory optimizer.