Where does this come from, and can I check it?

A flyby borrows a little orbital energy from the planet it passes. The figure is taken from NASA Science, which is linked in full on this page. Every fact on Mondo Knows names its source rather than repeating an unsourced claim.

Is this really a space fact?

Yes. It sits on the Space shelf, one of 2,600 sourced facts grouped into space, animals, the human body, history, science and more. Category pages collect every fact in the same field.

What else can I read about it?

The links under the fact point to a quiz, game, puzzle or calculator on the same subject, and the shelf below shows related facts. The wording here is original, and quoted phrases are marked as quotations.

Mondo Knows Facts

Gravity assists trade planetary motion for spacecraft speed

A flyby borrows a little orbital energy from the planet it passes During a flyby a spacecraft and a planet exchange momentum, and because the planet is far more massive, the craft's speed changes while the planet's barely does. Voyager 2 used alignments at Jupiter, Saturn and Uranus to reach Neptune. The trick only works against a moving target: the craft gains speed in the Sun's frame, not relative to the planet. It sits in Mondo's space collection, one of 200 facts that each trace back to the reference below.

Where this comes from

NASA Science

Facts that can change over time are reviewed and updated. If something here looks wrong, Mondo would rather know than be confidently incorrect.

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Tags: gravity-assist, trajectory, voyager

Gravity assists trade planetary motion for spacecraft speed: the short answers

Where does this come from, and can I check it?: A flyby borrows a little orbital energy from the planet it passes. The figure is taken from NASA Science, which is linked in full on this page. Every fact on Mondo Knows names its source rather than repeating an unsourced claim.
Is this really a space fact?: Yes. It sits on the Space shelf, one of 2,600 sourced facts grouped into space, animals, the human body, history, science and more. Category pages collect every fact in the same field.
What else can I read about it?: The links under the fact point to a quiz, game, puzzle or calculator on the same subject, and the shelf below shows related facts. The wording here is original, and quoted phrases are marked as quotations.