From a Summer Internship to a Solar System Tour: The Gravity-Assist Breakthrough

In 1961, UCLA graduate student Michael Minovitch, working at JPL, used an IBM 7090 to simulate thousands of trajectories and, by analyzing the encounter from the planet’s frame, discovered gravity assist: a spacecraft can gain speed by borrowing a planet’s orbital motion without using fuel. This insight, demonstrated on a room-sized computer, enabled outer‑solar‑system missions like Pioneer 10/11 and later Voyager to reach distant planets with far less propellant. Although Minovitch fought for proper credit, gravity assist became a cornerstone of spaceflight, illustrating how a planet’s motion can transfer energy to a passing spacecraft during a flyby.