How does a space probe use gravity to save fuel?
Quick Answer
It flies past a planet to steal a little of that planet’s orbital momentum, bending its path and changing speed without much fuel. This is called a gravity assist.
The Full Story
A gravity assist uses the motion and gravity of a planet to alter a spacecraft’s trajectory. As the probe passes the planet, it can gain speed or lose speed relative to the Sun, depending on the geometry of the flyby. This technique has been essential for deep-space missions because carrying enough fuel for every maneuver would be impractical. The Voyager spacecraft, launched in 1977, famously used gravity assists from the outer planets to explore the outer Solar System and beyond.
Key Facts
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