A gravity assist (or "slingshot") manoeuvre lets a spacecraft change its speed and direction by swinging past a moving planet, borrowing a tiny sliver of the planet's own orbital momentum. NASA has used it on missions from Voyager to Cassini and Parker Solar Probe to reach speeds and destinations no rocket alone could afford. This lab integrates real two-body gravity, step by step, so the curving hyperbolic path you see is genuinely computed, not scripted.
Voyager 2's "Grand Tour" of Jupiter, Saturn, Uranus and Neptune only worked because each flyby's speed boost set up the next one — a rare planetary alignment that will not repeat for well over a century.
A spacecraft on a hyperbolic path swings past a moving planet, and the encounter genuinely bends its trajectory and shifts its Sun-relative speed — computed live from real two-body gravity rather than a scripted animation.
Relative to the planet, incoming and outgoing speed are equal — only direction changes. But because the planet is itself orbiting the Sun, adding its velocity back in can raise or lower the spacecraft's heliocentric speed.
Set the approach speed, aim distance and target planet, choose whether to pass behind or in front of the planet's motion, then launch the flyby and watch the speed and turn-angle readouts update.
Voyager 2's tour of all four giant planets relied on a rare alignment that let each gravity assist set up the next — an opportunity that will not recur for well over a century.