Low-Energy Round-Trip Trajectories to Near-Earth Objects using Low Thrust

Abstract

Near-Earth Objects (NEOs) are attractive exploration targets due to their accessibility, scientific value, and resources. Although trajectory design has revealed efficient pathways to these bodies, systematic strategies for Earth-NEO transfers, especially with low thrust, remain limited. This work presents a streamlined methodology that blends the Sun-Earth circular restricted three-body problem (CR3BP) with the heliocentric two-body problem (2BP) to design low-energy round-trip trajectories. The current planar implementation enables efficient large-scale exploration of near-Earth space. Three-body manifold trajectories and transit orbits provide natural pathways for Earth departure and return through the L1 and L2 libration points, while the 2BP framework identifies spacecraft-NEO encounters through intersections of their elliptical orbits. This hybrid structure supports generating large collections of round-trip trajectories without heavy optimization, enabling rapid preliminary mission design across broad NEO populations. Rendezvous and takeoff maneuvers are first modeled as impulsive, then translated into low-thrust arcs to improve propellant efficiency. Round-trip transfers are assembled by combining compatible outbound and inbound branches under simple mission constraints. This modular approach is well suited for complex mission architectures that conventional patched-conics methods cannot systematically uncover. Applied to a representative NEO population, the method yields a large ensemble of round-trip trajectories with low launch and return energies, broad temporal flexibility, and competitive rendezvous and departure impulses compared to existing 2BP solutions.

Figures (16)

• Figure 1: Schematic representation of the trajectory design strategy showing the outbound and inbound phases connected through the NEO stay period.
• Figure 2: Phase angle between the synodic ($x,y,z$) and inertial ($X,Y,Z$) barycentric reference frames.
• Figure 3: Semimajor axis (y-axis), eccentricity (marker size), and inclination (color) of selected NEOs.
• Figure 4: Ecliptic view of the region of space accessed by MTs and TOs (delimited by purple lines) with the orbits of Earth and selected NEOs.
• Figure 5: Sequence of events of an Earth-NEO-Earth round-trip transfer designed with the patched-CR3BP/2BP method.