Swing-by (Gravity assist)
If spacecraft go really fast, fast enough to escape the gravity of our sun, then it would be able to leave our solar system!
But, achieving such a velocity is not that easy. So, what scientists did was come up with a really clever solution. It's called a swing-by!
What this means is, the object uses the gravities of other planets to alter its velocity. Let's say that a spacecraft comes close to Jupiter. What Jupiter's gravity would do is pull the ship closer, using its gravity, increasing its velocity. Then, the spacecraft would just barely avoid falling towards the planet, and "swing-by" the planet. The direction will have changed, and the speed might slow down a bit again, because the planet's trying to pull the spacecraft back. But here's where things get interesting: Jupiter's rotational speed gets added to the spacecraft's velocity.
This is how scientists are able to increase or decrease the velocity of a spacecraft, or even change its trajectory, or direction. This was how the Voyager and Pioneer space probes were able to take pictures of some of the planets in our solar system, as they flew by on their way towards outer space, gaining velocity with each "swing-by." Voyager 1 actually became the first space probe to leave our solar system entirely.
▇ Voyager 2 · ▇ Earth · ▇ Jupiter · ▇ Saturn · ▇ Uranus · ▇ Neptune · ▇ Sun
©NASA
This is the trajectory of Voyager 2. Starting from Earth, it was able to explore Jupiter, Saturn, Uranus, and Neptune by passing by them, and by gaining speed through swing-by, it was able to escape the solar system.
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