Gravity Assist (Slingshot Maneuver): How Spacecraft Gain Speed from Planets

The slingshot maneuver (gravity assist) uses a planet’s gravity to alter a spacecraft’s trajectory and velocity.

How It Works

As the craft passes a planet, gravitational pull accelerates it, changing its velocity vector. Geometry determines whether it speeds up, slows down, or changes direction.

Applications

1. Increase velocity: Pass ahead of planet’s orbit.
2. Decrease velocity: Pass behind planet’s orbit.
3. Change direction: Redirect to new target.

Historic Missions

Voyager, Cassini-Huygens, New Horizons—all used gravity assists to reach distant destinations with minimal fuel.

Success requires precise calculations of planet mass, velocity, flyby distance, and desired Δv.