Part 4/11:
To enter orbit around Mercury, spacecraft often need to perform multiple gravitational flybys with other planets, essentially using the gravity of passing bodies to slow down—akin to a billiards player setting up for the next shot. This process, while beneficial in lowering fuel requirements, results in extended travel durations. Where Mariner 10 executed three flybys, Messenger required an elaborate trajectory that involved 15 solar orbits and passes by both Earth and Venus.
The Complexities of Reaching Venus
Transitioning to Venus presents a consistent pattern: while many missions to Mars have comparatively swift travel times, Venus missions take much longer durations.