About Orbital Mechanic

Launch a probe and slingshot it past real planets, using today's actual planetary positions pulled from NASA JPL Horizons — the optimal trajectory genuinely changes day to day, the same way it does for real mission planners. Each gravity assist steals a small amount of a planet's orbital momentum to boost your probe's speed, no fuel required.

Under the hood it's the inverse-square law: gravitational pull falls off with the square of distance, which is exactly why timing your closest approach matters so much for how much speed you pick up.