The comment below @TomSpilker's answer

I'd love to see anything in LEO that can impart 20.89km/s of delta V to anything.

got me wondering what the highest velocity a spacecraft has left the Earth, relative to Earth?

This could be expressed as $v_{\infty}$ km/s or $C_3$ (km^2/s^2) relative to Earth.


1 Answer 1


That would be the New Horizons spacecraft, launched to a V-infinity of 16.26 km/s, with a monumental propulsion effort. The article describes the launch vehicle. Not only did it use a big Atlas V 551 with an expensive, high-performance Centaur upper stage, it had a third stage: an ATK Star 48B, a huge addition considering the New Horizons spacecraft weighed in at only 478 kg at launch.


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