What is the gravitational assist maneuver used by Voyager at Jupiter called?

The gravitational assist maneuver used by Voyager at Jupiter is called a gravity assist. Instead of relying only on its rocket engines, Voyager flew close to Jupiter and used the planet’s moving gravitational field to change its speed and trajectory.

The technique had been proposed for ambitious outer-planet missions and was successfully demonstrated by Mariner 10 at Venus before Voyager used it at Jupiter. Jupiter’s enormous mass made it especially useful: the spacecraft gained energy from the planet’s orbital motion around the Sun while Jupiter’s gravity bent its path toward Saturn and, for Voyager 2, onward to Uranus and Neptune.

Gravity assist is sometimes confused with aerobraking, which uses atmospheric drag, or with an engine-powered maneuver. Voyager did fire small hydrazine thrusters for orientation and course corrections, but Jupiter supplied the major boost. The maneuver helped make the planets’ rare alignment practical for the famous “Grand Tour” mission design.