Innovative research from the Beijing Institute of Technology is exploring the use of moons for gravitational assists, a technique that could significantly reduce fuel consumption and mission costs for space exploration.
Traditionally, spacecraft have utilized gravity assists from planets to alter their trajectories. However, the concept of employing a planet's moons, particularly those within weak stability boundaries (WSBs), offers new opportunities for trajectory adjustments. Jupiter, with its extensive system of 97 moons, presents a prime environment for such maneuvers. Simulations involving a gravity assist from Callisto, one of Jupiter's Galilean moons, have shown a notable decrease in the fuel needed for a spacecraft to achieve a stable orbit within the Jovian system.
The European Space Agency's (ESA) Jupiter Icy Moons Explorer (JUICE) mission is a current example of this evolving strategy. In August 2024, JUICE successfully executed a dual gravity assist, using both Earth and its Moon to refine its path toward Jupiter. This maneuver was a crucial part of JUICE's eight-year journey to study Jupiter's icy moons, including Callisto, Europa, and Ganymede.
Similarly, the BepiColombo mission, a joint project between ESA and the Japan Aerospace Exploration Agency (JAXA), has employed multiple gravity assists to reach Mercury. Launched in 2018, BepiColombo has conducted several flybys of Earth, Venus, and Mercury itself. Its most recent Mercury flyby occurred on January 9, 2025. These carefully planned maneuvers are designed to gradually decrease the spacecraft's velocity, enabling it to enter orbit around Mercury in late 2026.
The integration of moon-based gravity assists into mission planning represents a significant advancement in interplanetary travel. By carefully considering the gravitational interactions between planets and their moons, mission designers can identify novel opportunities for efficient trajectory adjustments. This strategy not only conserves valuable fuel but also opens up new possibilities for exploring the solar system with greater efficiency and reduced cost.