Gravity assist facts for kids
A gravitational slingshot, gravity assist maneuver or swing-by is the use of the relative movement and gravity of a planet to alter the path and speed of a spacecraft, typically in order to save fuel, time, and expense. Gravity assistance can be used to speed up, slow down and/or change the path of a spacecraft. The "assist" is provided by the motion of the gravitating body as it pulls on the spacecraft.
Images for kids
Cassini's speed related to Sun. The various gravity assists form visible peaks on the left, while the periodic variation on the right is caused by the spacecraft's orbit around Saturn. The data was from JPL Horizons Ephemeris System. The speed above is in kilometers per second. Note also that the minimum speed achieved during Saturnian orbit is more or less equal to Saturn's own orbital velocity, which is the ~5 km/s velocity which Cassini matched to enter orbit.
Gravity assist Facts for Kids. Kiddle Encyclopedia.