Gravity Slingshot

About this simulation

This simulation shows a gravity assist, the trick space probes use to gain speed. Students set the approach angle, the planet speed and the ship speed, choose to pass behind or in front of the planet, and watch the path with an optional trail. Readouts show speed before, speed now, speed after and the change. Passing behind the planet speeds the ship up, passing in front slows it down. Teachers can use it to discuss relative motion, vectors and conservation of momentum with real missions like Voyager 2.

What students can explore

Fly behind the planet and read the Change readout.
Switch Fly-by side to In front of the planet and compare the result.
Vary Approach angle and find the angle with the biggest gain.
Raise Planet speed and see how the gain changes.
Turn on Path trail to see how the path bends around the planet.

Learning objectives

1Explain how a spacecraft gains speed from a moving planet.
2Compare speeds measured in the planet's frame and in the Sun's frame.
3Predict whether a fly-by behind or in front speeds up the ship.
4Use vector addition to interpret a change in velocity.

Questions teachers ask

Is the gravity slingshot simulation free to use?

Yes. It is completely free and runs in any modern web browser, including on interactive whiteboards, tablets, Chromebooks and phones. There is nothing to install and no sign-up or account is needed.

Does the planet lose speed when the ship gains it?

Yes, but the planet is so massive that its slowing is unmeasurably small. Momentum is conserved, and the ship gains what the planet loses.

Why does passing behind the planet speed the ship up?

In the planet's own frame the ship leaves as fast as it arrived but is turned. In the Sun's frame the turned velocity adds to the planet's velocity, which increases speed on a trailing pass.

How do I use the gravity slingshot simulation?

Set speeds and angle, run the fly-by and record speed before and after. Repeat on the other side of the planet and compare the changes.

Embed this simulation

Drop it into your LMS, blog, or class site — free.

<iframe src="https://kiwibee.io/en/simulations/gravity-slingshot-3d-simulation/embed" title="Gravity Slingshot | KiwiBee" loading="lazy" allowfullscreen style="width:100%;height:min(70vh,620px);min-height:420px;border:0;border-radius:16px"></iframe>

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