When will New Horizons overtake Voyager 1 in distance from the Sun?



Basically, what the title asks. To my understanding, New Horizons is currently the fastest spacecraft that's moving away from the Sun, with arguably only Helios-A and Helios-B possibly faster still, but in an elliptical orbit around the Sun, so they won't make it out of the heliosphere.

So I'm curious, when will New Horizons traverse larger distance from the Sun than the Voyager 1 will in that time, and at approximately what distance?

I'm not entirely sure this can yet be calculated with any precision, since we don't know which Kuiper belt object will be selected for New Horizons visit after its Pluto flyby (or do we?), so feel free to make broad assumptions in your calculations.


Posted 2014-01-28T11:18:00.123

Reputation: 59 419



New Horizons will never overtake Voyager 1.

Although New Horizons is currently faster than any other man-made object, it won't be by the time it reaches the outer corners of the solar system.

From the John Hopkins University/Applied Physics Laboratory New Horizons page:

Though New Horizons will also reach 100 AU, it will never pass Voyager 1, because Voyager was boosted by multiple gravity assists that make its speed faster than New Horizons will travel. Voyager 1 is escaping the solar system at 17 kilometers per second. When New Horizons reaches that same distance 32 years from now, propelled by a single planetary swingby, it will be moving about 13 kilometers per second.


Posted 2014-01-28T11:18:00.123

Reputation: 5 209

@gerrit: Presumably its path through the Pluto system will be selected so it can reach its next target, a Kuiper Belt object that, as far as I know, has not yet been selected.Keith Thompson 2014-12-12T23:48:35.873

1So New Horizons doesn't get any speed boost from slingshooting past Pluto? Or is the plan to even reduce relative velocity to assume orbit in the Kuiper belt?TildalWave 2014-01-28T11:54:53.757

7Pluto is gravitationally tiny and won't have any significant influence on New Horizons' orbit. Perhaps a tiny correction but I wouldn't think so. New Horizons won't go into orbit anywhere. I don't know if they plan to use any fuel to slow down at all (but I could look it up). I wouldn't think so.gerrit 2014-01-28T12:09:27.817


Here's a nice graph of Voyager 2's speed, and the difference made by the gravitational assists:
Voyager speed graph
You can see that the probe slowed down between assists. New Horizons would follow a similar graph, but with fewer assists its speed will end up below Voyager 2's, as @gerrit said.


Posted 2014-01-28T11:18:00.123

Reputation: 63 604

@TidalWave you could probably extract the relevant information from the JPL HORIZONS ephemeris service.pericynthion 2014-06-16T23:51:42.703

Since Neptune was the last target slowing down would make sense anyway. Less issues with tracking and more time for the encounter. – None – 2014-12-12T20:21:11.373

2The graph looks like it left Earth with slightly more speed than the escape velocity needed to leave the solar system. But then it dropped below escape velocity again. I would assume a probe at escape velocity would stay at escape velocity. What am I missing?kasperd 2015-07-15T14:30:16.940

The probe is under the influence of the Sun's gravity, so it's in orbit of the Sun. When you go to a higher orbit, your speed decreases (you're converting kinetic energy into potential energy). See http://space.stackexchange.com/questions/4140/orbital-mechanics-why-doesnt-thrust-get-converted-to-speed

Hobbes 2015-07-15T14:38:37.333

2@Hobbes That explains why the speed can be drawn as a function of distance. Each such graph would either reach zero velocity at some finite distance or converge towards some constant at infinite distance. But the voyager 2 graph doesn't follow such a line, since it starts about one pixel above the escape velocity and then drops below escape velocity.kasperd 2015-07-15T14:53:08.757

Good point, and one that deserves a better explanation than can fit in a comment. If you ask this as a new question, we can give a detailed answer.Hobbes 2015-07-15T15:37:04.933


@kasperd, I asked your question here as I'm also curious what the reason is

neelsg 2015-07-29T07:54:08.903


Thanks, yes, I understand that there's gravitational influence on the probes even at those distances, of course, but I didn't find any directly comparable data on their velocities at more or less same distances without any gravitational assist maneuvers later changing it. Actually, I still can't find it to directly compare New Horizons and Voyager 1. There is data for Voyager 1 and 2 though, of which Voyager 1 was/is faster than what the graph for Voyager 2 from Wikipedia that you're attaching is showing.

TildalWave 2014-01-28T13:17:05.830

1The delta-V from the Sun's influence is the same for any probe (and proportional to $1/r^2$) , so you'd only need to know the probe's initial speed, and the delta-V gain from planetary gravitational assists to calculate the current speed of various probes.Hobbes 2014-01-28T14:13:35.053

Well, their velocity past any gravity assist slingshots, since they didn't follow same trajectory, yes. And that's what I couldn't find. I found velocities for Voyager 1 & 2 on the same date, from which I could calculate their velocities relative to the Sun at any distance to it once they're out of region of significant gravitational perturbations of the gas giants, but I just didn't find any such numbers for New Horizons. But I'll take those calculations from M. Buckley on New Horizons page. Thanks to both. :)TildalWave 2014-01-28T14:34:54.510

11It's interesting that the Neptune fly-by resulted in gravity braking - not an assist.EtherDragon 2014-01-28T22:48:39.500

9To get a Triton flyby, a high-priority science objective, Voyager 2 had to go over the North pole of Neptune. That resulted in a net reduction in heliocentric energy.Mark Adler 2014-03-25T01:22:54.147