The ESA probe BepiColombo flew past Earth on the way to Mercury. The probe launched in 2018 and made the last visit of our home before continuing onward to the final destination. The spacecraft needs to shed velocity to arrive at Mercury in 2025 at a velocity to enter orbit. The spacecraft will make multiple additional planetary flybys of Venus and Mercury to slow down to enter orbit.

In space travel, mission planners need to balance mission resources. The amount of fuel required to either speed up or slow down a spacecraft greatly impacts the cost of the mission. Using a longer flight path can reduce the propellent requirements for a mission but the mission will take longer. Gravity assists can, therefore, allow a spacecraft to be launched on a cheaper, less powerful rocket.

Gravity assist flyby?