# Which is the longest distance traveled by a space craft?

Which is the longest distance traveled by a space craft? Manned or unmanned? I believe it's Voyager, but I am not sure about the distance it traveled or is still traveling.

I believe the mission would be a one way mission obviously, but I may be wrong.

• Distance travelled relative to what? We're all travelling tremendous distances relative to the Sun. Sep 29, 2016 at 13:19

The spacecraft farthest away from Earth is Voyager 1. But that's not necessarily the longest distance traveled. If you accept the distance traveled while in orbit, a spacecraft can rack up a lot of miles while staying close to Earth.

Let's try this for Helios I:
launched in 1974, so 42 years ago. 367.920 hours, 1.324 *109 seconds, at 45 km/s this is 59 *109 km traveled, much further than Voyager's 19 *109 km.

The Helios probes are in an eccentric probe. Assuming a speed of 70 km/s at perihelion and 30 km/s at aphelion (close to Earth's speed), a straight average is 45 km/s.
A better value can be calculated by finding its orbital period and the length of one orbit, I'm having some trouble figuring out how to find that length.

• Speed record actually now belongs to Juno, which at the time of Jupiter intercept achieved 73 km/s. Sep 29, 2016 at 13:04
• Yes, but that's not useful for this calculation: with its highly elliptical orbit, Juno will be traveling slower than that most of the time. Sep 29, 2016 at 13:25
• Helios was also quite eccentric, so... By that measure, your time is off, it will spend far more time at a slower speed. The speed you listed was the highest achieved, at the point closest to the sun, the furthest point will be much slower. Sep 29, 2016 at 13:48
• changed the calculation a bit, using an average speed instead of maximum. Sep 29, 2016 at 16:38
• – uhoh
Dec 19, 2020 at 4:57