Design of a low-thrust gravity-assisted rendezvous trajectory to Halley's comet

TL;DR

This study designs a low-thrust gravity-assisted rendezvous trajectory to comet 1P/Halley by integrating a planetary gravity assist with electric propulsion to enable a zero-relative-velocity encounter well before Halley’s peak activity. A two-step approach first constructs impulsive solutions that minimize total impulse, then converts them into low-thrust arcs that respect finite power and propellant limits from a 1000 kg spacecraft powered by RTGs and a 36 mN Hall thruster. Two GA options are explored: Earth–Jupiter–Halley and Earth–Saturn–Halley, each yielding multiple high-energy solutions (C3) and rendezvous dates; LT formulations show propellant efficiency improves at the cost of higher total impulse, with Saturn providing more favorable energy budgets. Among the candidates, S1 (Earth–Saturn–Halley) offers early encounter opportunities at large heliocentric distances, while J1 (Earth–Jupiter–Halley) provides a viable fallback with a longer lead time for mission development. The results demonstrate feasibility of Halley rendezvous using existing propulsion technology, enabling early scientific observations of comet activity before perihelion.

Abstract

Comets are the most pristine planetesimals left from the formation of the Solar System. They carry unique information on the materials and the physical processes which led to the presence of planets and moons. Many important questions about cometary physics, such as origin, constituents and mechanism of cometary activity, remain unanswered. The next perihelion of comet 1P/Halley, in 2061, is an excellent opportunity to revisit this object of outstanding scientific and cultural relevance. In 1986, during its latest approach to the Sun, several flyby targeted Halley's comet to observe its nucleus and shed light on its properties, origin, and evolution. However, due to its retrograde orbit and high ecliptic inclination, the quality of data was limited by the large relative velocity and short time spent by the spacecraft inside the coma of the comet. A rendezvous mission like ESA/Rosetta would overcome such limitations, but the trajectory design is extremely challenging due to the shortcomings of current propulsion technology. Given the considerable lead times of spacecraft development and the long duration of the interplanetary transfer required to reach the comet, it is imperative to start mission planning several decades in advance. This study presents a low-thrust rendezvous strategy to reach the comet before the phase of intense activity during the close approach to the Sun. The trajectory design combines a gravity-assist maneuver with electric propulsion arcs to maximize scientific payload mass while constraining transfer duration. A propulsive plane change maneuver would be prohibitive. To keep the propellant budget within reasonable limits, most of the plane change maneuver is achieved via either a Jupiter or a Saturn flyby. The interplanetary low-thrust gravity-assisted trajectory design strategy is described, followed by the presentation of multiple proof-of-concept solutions.

Figures (16)

• Figure 1: Flyby geometry in planetocentric frame $\{ {\bf u}_1 , {\bf u}_2 , {\bf u}_3 \}$.
• Figure 2: Low-thrust design strategy: backward (left) and forward (right) propagation.
• Figure 3: Earth-Jupiter transfer. Launch energy ($C3$) vs. Flyby date.
• Figure 4: Earth-Jupiter transfer. Launch date vs. Flyby date.
• Figure 5: Earth-Jupiter-Halley trajectory. Total impulse ($\Delta V_{\textrm{tot}}$) vs. Flyby date.