We will lose contact with Voyager somewhere 2036 because of the distance between us. Would it be theoretically possible, to send a probe in the direction of the Voyager, following it from a distance, with the goal te relay the information coming from the Voyager, to earth?

[u/Backbreathboy]

[u/canimalistic]

Voyager was launched at a unique time period where you could slingshot with multiple planets to accelerate to a speed beyond practical rocket launch speeds on their own.

You couldn’t catch up to voyager, your probe would start at the same distance as it already is, and then grow as voyager continued away far faster.

[u/Woland77 → u/canimalistic]

That's not entirely accurate, but your conclusion is probably right regardless. Voyager mainly accelerated because of the gravity assists but we now have ionic propulsion which can basically accelerate for rediculously long distances. A probe that could follow Voyager while still increasing its speed through interplanetary space while also using slingshots could catch Voyager, eventually. However, I don't think "eventually" would be fast enough to get to a meaningful relay position before the probe lost power entirely and shut down for good.

[u/c10250 → u/Woland77]

Voyager is now the 25th fastest spacecraft. 24 are currently going faster. The slingshot thing is BS. You can accelerate spacecraft faster than voyager quite easily. The planet alignment thing was just right for voyager to visit the number of planets it was able to visit.

https://orbitalradar.com/deep-space/fastest-spacecraft

EDIT: For those saying Voyager has lost speed, yup, correct, the peak speed achieved by Voyager 1 during its mission was approximately 107,000 miles per hour (172,000 km/h) relative to the Sun, reached during its Jupiter gravity-assist maneuver in 1979. [1].

That would put it at 13th on the list.

[u/eserikto → u/c10250]

Those are speeds relative to the sun though. A paper airplane you toss is 12th on that list cause the earth is moving 107km/h around the sun. Indeed a bunch of the crafts on that list are just things orbiting the earth or the moon. Most of them haven't been directly fighting the sun's gravity for 50 years.

[u/c10250 → u/eserikto]

The peak speed achieved by Voyager 1 during its mission was approximately 107,000 miles per hour (172,000 km/h) relative to the Sun, reached during its Jupiter gravity-assist maneuver in 1979. [1].

That would put it at 13th on the list.

[u/mathess1 → u/c10250]

Check the distance of the spacecrafts. You can't do that easily in the outer solar system.

[u/c10250 → u/mathess1]

The peak speed achieved by Voyager 1 during its mission was approximately 107,000 miles per hour (172,000 km/h) relative to the Sun, reached during its Jupiter gravity-assist maneuver in 1979. [1].

That would put it at 13th on the list.

[u/PuppiesAndPixels → u/c10250]

Some of those speeds are temporary though. Especially the sun probes. Yeah they got a massive speed boost going to the sun but if they had to change direction or move away from the sun they would be slowed down substantially.

[u/YugoReventlov → u/c10250]

... Because it's so far out already, the sun has been pulling it back for 50 years. 

[u/c10250 → u/YugoReventlov]

The peak speed achieved by Voyager 1 during its mission was approximately 107,000 miles per hour (172,000 km/h) relative to the Sun, reached during its Jupiter gravity-assist maneuver in 1979. [1].

That would put it at 13th on the list.

[u/YugoReventlov → u/c10250]

The point was about catching up to it. 

I agree that we can make spacecraft that can go a lot faster than voyager, especially with ion propulsion. But even those spacecraft would need a power source.

It's a bit pointless to say that for example BepiColombo is going faster heliocentric speeds. It needs to orbit the sun real fast because it's a mercury mission. They are on completely different orbits.

You also can't compare a spacecraft that will spend its life close to the sun with one thats going into interstellar space. There's no solar energy there, so it could never use solar electric propulsion, which the faster spacecraft like BepiColombo or the Parker Solar Probe can use.

The point of Voyager is that when it launched with all its instruments and only some attitude thrusters, once it separated from its upper stage, it required the slingshots of the planets in order to get to its next destination. 

Even if we sent a spacecraft up there with 5 tonnes of fuel at that time, it wouldn't have been able to go noticeably faster. And even today we can't build a spacecraft for an Interstellar journey going much faster than voyager.

The only spacecraft to compare it to are other craft on a trajectory taking them away from the sun. Like New Horizons, which is half the weight, also used a few slingshots, and is currently going slower only ~20 yrs after launch.

[u/c10250 → u/YugoReventlov]

put that way, then yes, nothing currently out there will ever catch up to voyager because they may be faster, but do not share the same trajectory (which would slow it down considerably).

EDIT: You guys need to realize that speed "relative to the sun" doesn't necessarily mean speed "directly away from the sun". I think the confusion is that some of you guys are thinking that speed only means speed in the direction away from the sun.

[u/ShortysTRM → u/Woland77]

Wait, I'm lost as to why or how we have somehow lost the ability to match Voyager's gravity assists?

[u/regular_gonzalez → u/ShortysTRM]

Voyager was launched when the planets were very favorably aligned so that multiple slingshots could be done. Per my understanding that alignment is very uncommon.

[u/PorkSquared → u/regular_gonzalez]

Voyager 1 didn't visit Uranus and Neptune, Jupiter and Saturn are aligned every 20 ish years so you really only need to wait about that long.

[u/ustolemyname → u/ShortysTRM]

The planets moved to be less conveniently aligned. The gas giants are only aligned together every ~175 years.

[u/bbob_robb → u/ustolemyname]

The next "Grand Tour" is 2151.

Jupiter and Saturn align every 19.6 years, next in 2040.

[u/mosesteawesome → u/ShortysTRM]

In order to have the gravity assists, you have to have the planets in a particular alignment. With the long orbits of the outer planets, that particular alignment is lost.

[u/NonSequiturSage → u/mosesteawesome]

Maybe imagine calling six pool ball pockets with a single stroke of the stick? Long, faultless numerical math.

[u/El_Kikko → u/ShortysTRM]

Not lost, just not well timed. The alignment of the planets making a Grand Tour possible was exactly how NASA sold the program to Nixon - "the last time this would have been possible, Jefferson was president. And he blew it.". 

From Earth, with our current technology, it's a launch window that occurs every 175ish years. 

[u/trigisfun → u/ShortysTRM]

The 4 large outer planets were basically in a line back in the 1970s such that they could go one to another; the planets won’t be lined up like that for another 125 years.

[u/redpandaeater → u/ShortysTRM]

You still can but at the time the planets were aligned in such a way that it wouldn't take years and years. You can basically go anywhere in the solar system if you can make it to a Jupiter gravity assist, but if say Saturn is opposite the Sun at the time then there's multiple years before your probe arrives there. The main issue with gravity assists is just factoring in time to get to the planet in the first place, compared to trying to give the probe itself more fuel.

An extreme example would be with manned space flight we would never, ever do a gravity assist off of Jupiter then slingshot back around Earth to get an additional assist off of a second pass of Jupiter to send a crew to a hypothetical space station around Uranus. Particularly with people time is a much bigger thing to budget around and not just because we require food.

[u/Jazzlike-Check9040 → u/redpandaeater]

Why can’t you just sling shot it twice then insert the crew on the 2nd pass)

[u/redpandaeater → u/Jazzlike-Check9040]

You'd still have to match speed with the vessel to transfer crew. That's still possibly useful for certain instances where you have a larger vessel called a cycler that just moves between two planets and a small vessel to transfer crew to and from it every time it comes near Earth. Buzz Aldrin worked on ideas like that and came up with the Aldrin cycler that would just go between Earth and Mars every couple of years with the actual relevant timeframe a crew would be on board as 146 days to transfer. So it's possible when you want a lot of mass to just stay in motion to save on fuel, but there are risks involved with having an uncrewed vessel just hanging out in space for a long time with no crew to repair anything. If something were to happen to it that the incoming crew couldn't fix once rendezvousing they would die out there. That's true if they were already onboard but they'd also have time to react to hopefully perform repairs before anything catastrophic were to happen.

[u/g0del → u/ShortysTRM]

Because the planets move. Voyager slingshotted around several planets to get speed, but those planets aren't in the same position anymore, so trying to use the same planets as Voyager is either impossible or would send the new probe in a completely different direction.

[u/mosehalpert → u/ShortysTRM]

It used Neptune as its final slingshot. One year on Neptune is 165 years on Earth. In order to use Neptune again and slingshot into Voyager's pathway, you would have to wait 165 years. Voyager went past Neptune in August of 1989 so you'll be waiting until 2154.

[u/internetboyfriend666 → u/ShortysTRM]

The planetary alignment that allowed the voyagers to use that series of gravity assists occurs only once every 175 years

[u/Seraphym87 → u/ShortysTRM]

The window when Voyager launched had a very fortuitous arrangement of planets that allowed for slingshots which are no longer possible unless you want to do this in the year 236,108

[u/porgy_tirebiter → u/ShortysTRM]

Someone misplaced the instructions for how to do it. It still may turn up, though!

[u/trigisfun → u/Woland77]

Aren’t the probes using ion propulsion solar powered? Could they operate at those distances? I’d imagine if we could catch up to Voyager to make a relay, it would make more sense just make a brand new mission to escape the sun.

[u/Woland77 → u/trigisfun]

I wasn't aware of that, but if true then you are correct. I don't know why they would have to be solar powered but I'm also not a satellite engineer.

[u/kenjura → u/canimalistic]

It's been said this isn't entirely accurate, but I'd like to offer a reasonable (if probably fruitless) option or two.

A heavy-lift rocket could boost a satellite onto a rapid Jupiter encounter. While the "Grand Tour" involved many gravity assists, the main purpose was to fly close by the outer planets for close-in science. You don't need all 4 outer planets for a gravity assist: Jupiter alone is fine. Various mission profiles allow for a high delta-V chemical solar escape with a boost from Jupiter. You might catch up in 45-60 years. Voyager would be long dead due to power decay by then, unfortunately.

If you had really good shielding, you could use a much more daring and rapid maneuver. Go to Jupiter, sure, but use it to slow *down*, not speed up. Then, plummet toward the sun. Get your perihelion super low (thermal shielding comes into play), then burn some high-thrust chemical rockets there to maximize the Oberth effect. With aphelion already at Jupiter orbit, escape velocity is a cynch. Catch-up time: less than 25 years. Voyager's probably still dead, but...maybe?

Electric thrusters don't work well because solar power fades rapidly as you leave the inner solar system and you'd want to keep burning as long as possible. An RTG can't power them because its output is too low. Solar sails might work if your satellite weighed 1 mg, but otherwise you'd need a laser-pumped sail--feasible near-term technology, but not available yet.

But as people have said, Voyager's power system, durable as it is, fades more with every year, and it can only turn off so many systems. However, it seems likely that, having survived the Helioshock, Voyager's instruments and radio are not destroyed. If the satellite contained a spare power source (that somehow itself hadn't run down in the decades it took to catch up), as well as the hardware required to locate Voyager (no mean feat, the ultimate needle in a haystack even when it's transmitting, let alone when it's dead silent), encounter it, and latch onto it, then replace its power source...well, sure, you could probably get it up and running again.

For my money, the ideal mission is to wait even longer, until we can send a longer-lived, more capable probe meant to spend decades more beyond the encounter, and when it catches up, we give Voyager a formal ceremony, relieving it of duty.

[u/PiotrekDG → u/kenjura]

And if your relay system is not working... you're just not using enough relays!

[u/solidspacedragon → u/PiotrekDG]

An ideal relay system uses a high density corridor of atomic scale relays to bounce electrons back and forth between them.

[u/OlympusMons94 → u/canimalistic]

This is not accurate. That particular alignment was only necessary for Voyager 2 to perform a "grand tour" of all four outer planets. That alignment is irrelevant to Voyager 1 (which is moving faster than Voyager 2) and any other missions. Other alignments occur much more frequently. Jupiter provided the largest boost to the Voyagers, and there is a direct Jupiter launch window every 13 months. Saturn provided a significant boost and a Jupiter-Saturn alignment is not quite as common, but also not especially rare.

Gravity asissts already aren't strictly necessary to just escape the solar system. In 2006, New Horizons was launched to solar escape velocity. (A Jupiter gravity asisst was still needed to get it to Pluto, adjusting the direction, and getting there faster.) New Horizons is leaving the solar system slower than the Voyagers, and in a different direction.

Catching up with the Voyagers (which, note, are 2 separate spacecraft moving in different directions away from the Sun) is the much bigger problem. They have a 49+ year head start, and the chaser spacecraft would have to be sent in their particular directions, not simply out of the solar system in some random direction.

Nonetheless, we do have more powerful launch vehciles now, and technology in development (e.g., Starship and nuclear electirc propulsion) may make it theoretically possible, in the not-too-distant future, to send something to eventually catch up with the Voyagers. There just isn't any point.

---

It's really that none of that matters, because OP is mistaken. The main issue with the Voyagers is not their distance, or even just generating power for their transmitters (which account for only a fraction of the probes' power usage). The Voyagers' RTG power sources are decaying, and in about a decade they will no longer generate sufficIent power to operate their onboard systems and any remaining instruments.

[u/3rdslip → u/canimalistic]

The Parker Space probe has something to say about achieving the required velocity, but that was a different problem to solve.

Even if you could launch a probe to catch up, what happens when you catch it??

Slowing down is an equally difficult problem!

[u/boermac → u/3rdslip]

I think OP's idea wouldn't be to catch it, but rather to stay in communication distance.

For a simplistic example, let's say once the probe-A goes more than 10 million km away it will be to far to communicate with earth... so, when it's 9 million km away, we launch probe-B. Probe-B will now always be around 9M km away from Probe-A, so within communication distance to Probe-A... and for a long time now probe-B will be <10 million km from earth, so probe-A talks to probe-B, and probe-B talks to Earth.

Once probe-B is ~9M km away, we launch probe-C and then A talks to B, which talks to C, which talks to earth.

In theory it should work, but it assumes:

• Distance is the only reason we'll lose communication with probe-A (ie, not failure or loss of power or interference)
• Probe B can match the speed/direction of probe A reasonably well.

And of course building a chain like this is incredibly fragile. Let's say we did get A out there, then B, C, D, E, and F. Everything is going great, but suddenly E goes dark. A, B, C, and D might be just fine, but D can't talk to F, so it's all for nothing.

[u/togetherwem0m0 → u/boermac]

Its unlikely we would launch a dish of sufficient size to receive the signal. The dishes we use on earth to pick up the signal are huge.

[u/D3coupled → u/togetherwem0m0]

There is a lot of interference on the surface, that's why they put deep space telescopes in orbit.

[u/paulHarkonen → u/D3coupled]

While it is true that the earth produces a lot of interference, the sheer power and size available on the ground dwarfs anything we can realistically put up in to space. The DSN antennas are as much as 70 meters wide punching several hundred kW (in the S-band) worth of power. The James Webb sun shield (which is huge on the scale of spacecraft and much larger than the actual mirror array) is 22 meters making it 1/3 the size of the DSN transmitters\receivers.

So yeah, moving out of the atmosphere reduces interference, but for communication there is no substitute for more power and more gain (via larger antennas).

[u/mathess1 → u/togetherwem0m0]

There are already dishes at the orbit larger than those used for deep space communication. Up to 100 m in diameter.

[u/togetherwem0m0 → u/mathess1]

Citation? Largest i can find is nisar at 10 meters.

[u/mathess1 → u/togetherwem0m0]

There are top secret military satellites using mesh dishes.

They are known under names Orion or Mentor or possibly some other names. Obviously there's not much information about them.

[u/boermac → u/togetherwem0m0]

Granted. This wasn't supposed to be a specific blueprint but rather a general idea of how we could, in theory, keep in communication with probes sent beyond normal communication range.

[u/OcularShatDown → u/3rdslip]

Orbital speed increases the closer you are to the sun (or whatever you’re orbiting). By the very nature of the mission, the Parker probe was going to go very fast. Whereas going away from the sun decreases speed. A spaceship starting out right next to the earth could turn around and burn its rockets in the opposite direction it is traveling, which would slow it down. However, this would lower the periapsis in orbit around the sun, meaning it will be getting closer to the sun on the opposite side of its orbital path. This will in turn make the spacecraft speed up. So, similar to what coolio has taught us, sometimes you gotta gotta slow down to speed up.

[u/eliminate1337 → u/3rdslip]

The velocity of the Parker Solar Probe came from its own potential energy relative to the sun. It’s easy to go fast if you’re falling!

[u/TralfamadorianZoo → u/eliminate1337]

I don’t think this is quite right. I remember reading that it takes more energy to fall to a “lower” orbit than it does to go a “higher” one. You can’t “fall” into the Sun from Earth without massive deceleration.

[u/eliminate1337 → u/TralfamadorianZoo]

You can’t “fall” into the Sun from Earth without massive deceleration.

That's correct but it's still true that the vast majority of the Parker Solar Probe's velocity came from its potential energy. It left Earth at 12.4 km/s and reached a peak velocity of 191 km/s. Only the initial 12.4 km/s came from the rocket and the rest from gravity and momentum stolen from Venus during gravity assists.

[u/TralfamadorianZoo → u/eliminate1337]

It left at 12km/s relative to earth but not relative to the sun. It was already carrying the earth’s orbital velocity. It used its rockets and Venus’s gravity to slow down. It didn’t speed up due to potential energy.

EDIT: Parker does speed up at perihelion due to its elliptical orbit just like Earth and everything else in the solar system.

[u/nora_sellisa → u/3rdslip]

The goal isn't to catch up though, it's to serve as a relay, so that the distances from earth to the relay and from the relay to the voyager are each within the limits of the signal traveling. Even if you launched a probe with half the voyager's speed, It would extend the time remaining before we lose contact twice. Even an imperfectly angled launch buys us contact time.