Gravity Assists

Stealing speed from planets

An interactive lesson with 7 steps, about 6 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• In the planet’s frame the flyby speed is unchanged. In the Sun’s frame, it can increase.
• The planet loses an immeasurably small amount of orbital energy.
• Gravity assists sent Voyager 2 past all four giant planets.

Steps

1. The slingshot
2. One flyby, two points of view
3. Where does the energy come from?
4. Head-on bounce
5. Plan a flyby
6. Speeding up or slowing down
7. The Grand Tour