Free-return trajectory

Imagine you are playing with your toy car by rolling it down a big slope. Now, let's pretend that you want to throw your toy car in the air and make it come back to you without needing to touch it. That's what a free-return trajectory is!

In space, this trajectory is a special type of route that a spacecraft can follow without the need for any engine maneuvers. The spacecraft is launched in such a way that it flies past a planet or a moon and using the planet's gravity to change its course, allowing it to return to Earth without the need for any extra fuel or adjustments.

Just like a toy car that goes up and down the slope, the spacecraft's path is carefully planned to make sure it comes back to Earth safely. Think of it like a boomerang - the spacecraft is thrown out, it goes around the planet, and then it comes back to where it started from. This type of trajectory is useful for missions where we need to do some observation or investigation of a celestial body like the Moon or an asteroid, but we also want to make sure that we have enough fuel to get back home.

Overall, a free-return trajectory is a clever way of using the gravity of planets and moons to help spacecraft explore the solar system without using up too much fuel. So just like how you can make your toy car come back without any extra effort, spacecraft can come back home after completing their mission using the free-return trajectory.