How do satellites use gravity for slingshot manoeuvres?

Satellites use gravity for slingshot manoeuvres by harnessing the gravitational pull of a planet or moon to gain speed.

In more detail, this technique, also known as a gravity assist or gravitational slingshot, involves a spacecraft using the gravity of a planet or moon to alter its speed and trajectory. This is a common method used in space exploration to save fuel, extend spacecraft lifetimes and achieve difficult trajectories.

The principle behind a gravity assist is relatively simple. As a spacecraft approaches a planet, it falls into the planet's gravitational field, accelerating towards the planet. This acceleration increases the spacecraft's velocity. If the spacecraft is then able to exit the planet's gravitational field on the opposite side, it will retain this increased velocity. This is similar to how a slingshot works, with the planet playing the role of the slinger, and the spacecraft the stone being flung.

However, the spacecraft doesn't just gain speed from this manoeuvre. The direction of its path can also be changed. The angle at which the spacecraft approaches the planet and the planet's own motion both affect the spacecraft's exit trajectory. This allows for complex manoeuvres, such as those needed to reach the outer planets of our solar system.

The gravity assist technique was first used in the 1960s, with NASA's Mariner 10 mission to Mercury. Since then, it has been used in many notable missions, including the Voyager missions to the outer planets and the New Horizons mission to Pluto.

It's important to note that while gravity assists can provide a significant boost, they require very precise navigation. The spacecraft must approach the planet at just the right angle and speed to achieve the desired effect. This requires careful planning and precise control of the spacecraft. Despite these challenges, gravity assists remain a crucial tool in space exploration.