Comment by glenstein
2 days ago
Not that we would literally do this with Voyager, but it makes me wonder at the potential utility of a string of probes, one sent every couple of [insert correct time interval, decades, centuries?], to effectively create a communication relay stretching out into deep space somewhere.
My understanding with the Voyagers 1 and 2 is (a) they will run out of power before they would ever get far enough to benefit from a relay and (b) they benefited from gravity slingshots due to planetary alignments that happen only once every 175 years.
So building on the Voyager probes is a no-go. But probes sent toward Alpha Centauri that relay signals? Toward the center of the Milky Way? Toward Andromeda? Yes it would take time scales far beyond human lifetimes to build out anything useful, and even at the "closest" scales it's a multi year round trip for information but I think Voyager, among other things, was meant to test our imaginations, our sense of possible and one thing they seem to naturally imply is the possibility of long distance probe relays.
Edit: As others rightly note, the probes would have to communicate with lasers, not with the 1970s radio engineering that powered Voyagers 1 and 2.
What you are describing has been proposed before, for example within context of projects like Breakthrough Starshot. In that the case the idea is to launch thousands of probes, each weighing only a few grams or less, and accelerating them to an appreciable fraction of the speed of light using solar sails and (powerful) earth-based lasers. The probes could reach alpha centauri within 20-30 years. There seems to be some debate though about whether cross-links between probes to enable relaying signals is ever practical from a power and mass perspective vs a single very large receiver on earth.
Indeed. I think the main reason to send thousands of probes is increasing the odds that they will survive the trip and also be in the right position to gather usable data to transmit back.
Also once you have created the infrastructure of hundreds or thousands of very powerful lasers to accelerate the tiny probes to incredibel speeds, sending many probes instead of a few doesn't add much to the cost anyway.
Sun as a focus lens. "Just" 500 AU.
The Voyager can be overtaken in several years if we to launch today a probe with nuclear reactor powered ionic thruster - all the existing today tech - which can get to 100-200km/s in 2-3 stages (and if we stretch the technology a bit into tomorrow, we can get 10x that).
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What these proposals like to forget (even if addressing everything else) is that you need to slow down once you arrive if you want to have any time at all for useful observation once you reach your destination.
What's the point of reaching alpha centauri in 30 years if you're gonna zip past everything interesting in seconds? Will the sensors we can cram on tiny probes even be able to capture useful data at all under these conditions?
Jupiter is 43 lightminutes from the Sun.
If we shoot a thousand probes at 0.1c directly at the Alpha Centauri star, they should have several hours within a Jupiter-distance range of the star to capture data. Seems like enough sensors and time to synthesize an interesting image of the system when all that data gets back to Earth.
Could the probe just fire off some mass when it got there?
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If I don't recall wrongly, Breakthrough Starshot was not a means for commnunicaiton relay as he describes.
It wasn't intended for a communications relay, but it was intended to have 2-way communication. I went down a rabbit hole reading ArXiv papers about it. Despite their tiny size, the probes could phone home with a smaller laser - according to the papers I read, spinning the photons a certain way would differentiate them from other photons, and we apparently have the equipment to detect and pick up those photons. The point of the communication would be for them to send back data and close-up images of the Alpha C system. Likewise, they could receive commands from earth by having dozens of probes effectively act as an interferometry array.
I bet you that this hasn't been proposed, though: https://www.youtube.com/watch?v=GfClJxdQ6Xs
I found that video very interesting! Especially the second half about apparent superliminal speed
really wonderful explanation
No one likes to think this but it’s very possible voyager is the farthest humanity will go. In fact realistically speaking it is the far more likeliest possibility.
Provided we don't wipe ourselves out, there's no technical reason why we can't go interstellar. It's just way harder and more energy intensive than most people imagine, so I doubt it's happening any time in the next few hundred years.
But we already understand the physics and feasibility of "slow" (single-digit fractions of c) interstellar propulsion systems. Nuclear pulse propulsion and fission fragment rockets require no new physics or exotic engineering leaps and could propel a probe to the stars, if one was so inclined. Fusion rockets would do a bit better, although we'd have to crack the fusion problem first. These sorts of things are well out of today's technology, but it's not unforeseeable in a few centuries. You could likewise imagine a generation ship a few centuries after that powered by similar technology.
The prerequisite for interstellar exploration is a substantial exploitation of our solar system's resources: terraform Mars, strip mine the asteroid belt, build giant space habitats like O'Neill cylinders. But if we ever get to that point - and I think it's reasonable to think we will, given enough time - an interstellar mission becomes the logical next step.
Will we ever get to the point where traveling between the stars is commonplace? No, I doubt it. But we may get to the point where once-in-a-century colonization missions are possible, and if that starts, there's no limit to humanity colonizing the Milky Way given a few million years.
Nuclear pulse and fission fragment designs require no new physics in the same way that a Saturn 5 didn't require new physics when compared to a Goddard toy rocket.
It's easy until you try to actually build the damn thing. Then you discover it's not easy at all, and there's actually quite a bit of new physics required.
It's not New Physics™ in the warp drive and wormhole sense, but any practical interstellar design is going to need some wild and extreme advances in materials science and manufacturing, never mind politics, psychology, and the design of stable life support ecologies.
The same applies to the rest. Napkin sketches and attractive vintage art from the 70s are a long way from a practical design.
We've all been brainwashed by Hollywood. Unfortunately CGI and balsa models are not reality. Building very large objects that don't deform and break under extremes of radiation, temperature changes, and all kinds of physical stresses is not remotely trivial. And we are nowhere close to approaching it.
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The other thing we could do to explore the galaxy is to become biologically something we would no longer recognize. We're viewing this from the lens of "humanity must remain biologically static" but I want to point out that that's not physically necessary here and that there is life on Earth that can stop its metabolism for decades and things like that.
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We don’t have to completely wipe ourselves out to regress or stagnate. There have been many civilizations that have regressed.
The child within me likes to dream and this is the dream I have!
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Yes, it's incredibly easy to do these things once you've done all these other, incredibly difficult things first.
The furthest a human has been is 250k miles (far side of the moon). The fastest a human has traveled is only 0.0037% the speed of light.
The ISS is about 260 miles from the Earth. At that height, the gravity is actually roughly the same as on the surface, it's only because it is in constant freefall that you experience weightlessness on it.
Mars is 140 million miles away. And not exactly hospitable.
I like how you treat "the fusion problem" with a throwaway, "Yeah, we'd have to solve that" as if we just haven't sufficiently applied ourselves yet.
All of those incredibly difficult things we have not even begun to do are the technical reasons we have not gone interstellar and may be the reason we will never do so.
And even if we solve the issue of accelerating a human being to acceptable speeds to reach another star, the next closest star is 4 light years away. That means light takes 4 years to reach. Even if you could average half the speed of light, that's 8 years, one way. Anything you send is gone.
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If I understand correctly, you're just basing that statement on climate change or war destroying us before we can do any better than Voyager, right? Because if we don't assume the destruction of humanity or the complete removal of our ability to make things leave Earth, then just based on "finite past vs. infinite future," it seems incredibly unlikely that we'd never be able to beat an extremely old project operating far beyond its designed scope.
Many reasons why. The probability is based on many many many factors. What you mentioned is just a fraction of the factors.
If we do ever reach that distance again it will be even less likely we do it for a third time.
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This is all based on the assumption that we are not able to build spacecrafts with faster speeds.
There was simply no incentive to do so yet. But one day we will build faster spacecrafts and then we are going to overtake it quite quickly.
Based on what? That we will never be able to make probes travelling faster than ~17km/s (relative to the Sun) that will eventually reach and overtake Voyager 1?
I certainly wouldn't bet against technological progress, and I say that as a complete doomer.
Well voyager depended on a solar system alignment that only happens every 175 years(?) so it'd be a while before we get that same advantage again. The longer it takes the further of a head start voyager gets?
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I was always wondering if there’s some sort of limitation in science. Just like in some games you can’t fly according to the rules (science), so there’s just no way to do that without cheating. What if e.g. in 5k years we will reach the limit? Basically like after playing a couple of months in minecraft the only thing you can do is to expand
No, that sounds wrong. I am sure future objects will go further.
We either go extinct or we populate the galaxy (potentially an evolution which will be unrecognisable)
Currently though there’s nothing planned to leave the solar system faster than voyager 1. New horizons will never catch up short of some weird gravity slingshot in millions of years which is probably just as likely to fling musks roadster out into interstellar space
Unless we go extinct. But I concur.
> In fact realistically speaking it is the far more likeliest possibility.
What insight do you have into this issue that would suggest this is true?
1. Get to AGI 2. Optimise for energy efficiency 3. Shoot billions of AGIs into space a year
... Be responsible for the very longterm torture of billions of intelligent lifeforms who are forced to drift through boring space for 1000s of years.
If you make it, you can make it like it.
I think it literally every day… and with literally every day the odds of our surpassing ourselves on this one gets, again very literally, further away.
The odds are pretty damn flat.
If we launched today, 1% faster would be enough.
If we launched in a hundred years, 1% faster would be enough.
And going faster is downright easy. We can beat Voyager's speed significantly any time we want (plus or minus ten years for planetary alignment).
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Not useful, because the signal are too weak to be picked up probe to probe.
On earth, the tiny signal from Voyager at this distance is picked up by dish the size of a football field; same with sending of the signal.
Very true insofar as it's a description of Voyager communications. Voyager was 1970s radio engineering. Radio signals spread wide, so you need a big dish to catch it. These days we are using lasers, and laser divergence is several orders of magnitude smaller. And regardless of tech, relay enforces a minimum distance for any signal to spread.
This is a silly counterexample - why would we launch them that far apart? It’s a terrible idea for multiple reasons. We’d want them close together, with some redundancy as well, in case of failures.
What dish size would be required for a “cylindrical/tubular mesh” of probes, say, 1AU apart (ie Earth-Sun distance)? I’m pretty sure that would be manageable, but open to being wrong. (For reference, Voyager 1 is 169AU from Earth, but I have no idea how dish size vs. signal strength works: https://science.nasa.gov/mission/voyager/where-are-voyager-1...)
Light year is 63,241 AU. That means tens of thousands of relays. It would super expensive and super unreliable. The other problem is that achievable speeds are super slow, Voyager is 25,000 years per light year which means that would wait 100,000 years for relays to Alpha Centauri to be possible.
Much easier just to send probe with large antenna or laser, and make a large antenna at Earth.
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The dish isn't the size of a football field, it's a 70 meter dish (football field is 110 meters), it can however, transmit at 400 kilowatts of power
Unlike the other comments I actually agree, physics has not changed since the 1970's, even the most focused laser and detector would need to be positioned perfectly to where the next probe would be, and with the nearest star 4 light years away we would be talking a chain of dozens, any of which may fail some way. The probes would also likely be small, cell-phone sized, power restricted, and difficult to shield (you couldn't just throw in the latest wiz-bang 2025 electronics as it all has to be hardened to work multiple decades) Best is a big, transmitter and good receiver one end.
You could send a good amount of small probes and make them become the big antenna dish basically. As long as you cover the bases, you can have layers of "big antenna dishes" in onion layers.
> the tiny signal from Voyager at this distance is picked up by dish the size of a football field
Lots of small fishes can resemble a large fish.
Laser communication could potentially address some of those issues.
Maybe, but if your probe is heading directly towards another solar system then it will be backlit by its destination.
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What if the probes carry smaller probes left behind at specific intervals that act as repeaters?
These baby probes could unfold a larger spiderweb antenna the size of a tennis court.
We need quantum entanglement based communication. Maybe without full collapse, using weak measurements, like Alice continuously broadcasts a "retrocausal carrier wave" by sequencing planned future post-selection measurements on her entangled qubits, which backward-propagates through time-symmetric quantum evolution to create detectable perturbations in the present states, biasing Bob's qubits away from pure randomness to encode message patterns.
Both parties perform weak measurements on their qubits to extract these subtle signals without collapsing the entanglement, preserving high coherence across the stream. A quantum Maxwell's demon (e.g. many experiments but can be done: https://pubmed.ncbi.nlm.nih.gov/30185956/) then adaptively selects the strongest perturbations from the wave, filters out noise, and feeds them into error correction to reliably decode and amplify the full message.
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The problem is each relay needs its own power source so it's not going to be as light and small as you would like. Solar power doesn't work very well outside of the solar system, or even really in the outer solar system.
On the plus side your big probe could push off of the small probe to give itself a further boost, also necessary because otherwise the small probes need thrusters to slow themselves to a stop.
You can't leave anything behind. That would need to be accelerated to 50,000 km/h or have even bigger rockets than launched Voyager in the first place.
Sure, drop one repeater every light-day. 1500 of them. Each one will need fuel to decelerate enough to remain in place.
Football field might even be too small…
Wasn’t Arecibo used for Voyager?
It might have from time to time... but it had limited ability to track.
As I type this, DNS Now is currently receiving data from Voyager 1. https://eyes.nasa.gov/apps/dsn-now/dsn.html
https://imgur.com/a/kXbhRsj for a screen shot of the relevant data.
The antenna data is https://www.mdscc.nasa.gov/index.php/en/dss-63-2/
No. Or not any more, DSS-43 at the Canberra Deep Dish Communication Complex is the only antenna that can communicate with the Voyagers.
I think only the Grand Tour program was possible every 175 years: From Wikipedia [1]: "that an alignment of Jupiter, Saturn, Uranus, and Neptune that would occur in the late 1970s would enable a single spacecraft to visit all of the outer planets by using gravity assists."
Gravity assists with more than one planet are more frequent. Cassini-Huygens [2] as example had five (Venus, Venus, Earth, Jupiter, Saturn)
I would suspect when the goal ist only to leave the solar system as fast as possible (and don't reach a specific planet) they are much more often.
[1] https://en.wikipedia.org/wiki/Grand_Tour_program [2] https://en.wikipedia.org/wiki/Cassini%E2%80%93Huygens
Well, the voyager power source is still pretty good. But as I understand it the thermocouple that converts heat to electricity has degraded. Because the Pu-238 half life is 87 years so they wouldn't even be down to half yet..
I wonder if we can go the reverse direction, where instead of launching more probes from Earth to serve as relays, the spacecraft would launch physical media toward Earth packed with whatever data it has collected. Given advancements in data storage density, we could achieve higher bandwidth than what's possible with radios.
The logistics would be difficult since it involves catch those flying media, especially if the spacecraft were ejecting them as a form of propulsion, they might not even be flying toward Earth. I was just thinking how early spy satellites would drop physical film, and maybe there are some old ideas like those that are still worth trying today.
The spacecraft is moving away from the sun at escape velocity. How is it going to launch anything backwards and have it make it all the way back to earth?
I think they're working on laser data transmission.
Binary encoding by pulsing the ion stream. Then picking that up with terrestrial telescopes. Very clever!
Smoke signals in space. I love it.
With current probes being so "slow" (peak speed of the Voyager probes was on the order of 0.005% the speed of light) I wonder if even doing 10 probes at once per decade gets you more data back than working towards faster probe for less total time.
You could use this to create a relay in reverse order, but I also wonder if having a 50-100 year old relay would be any better than just using modern tech directly on the newest, fastest probe and then moving on to the next when there are enough improvements.
My intuition is that the extra mass for the receivers would be a large negative in terms of travel time (1/sqrt(m) penalty assuming you can give each probe fixed kinetic energy).
Plus keeping a probe as active part of a relay is a major power drain, since it will have to be active for a substantial percentage of the whole multi-decade journey and there's basically no accessible energy in interstellar space.
Then again, it's still far from clear to me that sending any signal from a probe only a few grams in size can be received at Earth with any plausible receiver, lasers or not.
Thoughtful intuitions all around. My understanding is that lasers don't necessitate the big reception dish, but instead have a 1m or smaller reflective telescope. The laser setup is lighter, lower power and gas precedent in modern space missions.
Probes I suspect would realistically have to be large enough to send strong signals over long distances, so weightier than a few grams.
I think 99% downtime is an existing paradigm for lots of space stuff, e.g. NASA's DSOC and KRUSTY, so room for optimism there.
Though I think I agree with you that an energy payload as well as general hardware reliability are probably the bottlenecks over long distances. I have more thoughts on this that probably deserve a seperate post (e.g. periodic zipper-style replacements that cascade through the whole relay line) but to keep this on honoring the Voyager, I will say for the Voyager is at least for me huge for opening my imagination for next steps inspired by it.
I also spend far too much time wondering about sending out swarms of probes and if you could somehow rendezvous them and add fuel midjourney and so on!
The problem I see is that lasers are still subject to diffraction, and this is worse the smaller the aperture is relative to wavelength. Due to the small probe mass which you need to split with observation equipment, support systems and presumably some microscale nuclear power supply, you could maybe with a few breakthroughs in engineering manage a wispy affair on the order of a metre at most. It it scales with diameter and mass scales with diameter squared.
So the beam divergence of a visible light laser end with a diameter of over 18 million km over 4 light years. With 100W of transmission power, that's 0.1pW per square kilometer of receiver. Which isn't nothing, but it's not huge either.
I really don't see how the Starwisp type microprobes will actually work on a practical level at any time in the foreseeable future, even if the propulsion works. Not only is the communications a problem, but so is power, computational resources, observation equipment, radiation shielding and everything in between. But anything massier than that requires mindboggling amounts of fuel. And the problem is so much worse if you want to stop at the destination rather than scream past at a modest fraction of c and hope to snap a photo on the way past.
It really seems (sadly, in a way) that building gigantic telescopes will be a lot more instructive than any plausible probe for quite some time. An gravitational lens telescope would be a far better, and probably almost as challenging, project for learning about exoplanets. Not least it would be about 3 times further from Earth than Voyagers.
Could a probe return data by semaphore? Wave a flag that blocks the light of Alpha Centauri as seen from a telescope off to the side of the sun, say at the distance of Neptune's orbit. It should be possible to hide Alpha Centauri behind a relatively small semaphore until the probe gets fairly close.
Neat idea, but it looks like the math doesn't really work out: https://space.stackexchange.com/questions/66295/is-interstel...
Though it looks like these folks are thinking about blocking from near the star, which requires megastructures for anything detectable. I haven't done even back of the envelope calculations but I'd guess the limiting factor is you'd only be causing an eclipse/transit in an unusably narrow angle directly behind the craft. As you get closer the cone expands but the signal weakens.
Americium battery could last a lot longer.
That's how the mongols communicated but with guys on horses.
This is a link budget problem. A probe has to have a certain transmit power, receive sensitivity, physical size, fuel for orientation, etc. So you have to come up with the optimums there were it makes sense at all which isn't easy, especially compared to having one big station near earth that communicates point to point with the deep space whatever.
It might just have to be much too big to be worth it in the next n centuries.
If humans settle Mars it'll probably make sense to build one there for marginal improvement and better coverage with the different orbits of Earth and Mars.
Hmm, do you realize, that even if you have 1B probes everywhere. You're still bound by speed of light communication speed, right?
It's faster than probe speed in this age, yeah. But still not enough, if we're talking distances to other specific planets, stars, etc.
Two possible ways to solve this, humans will become immortal or speed of light bypass method will be discovered.
the post office has utility even if the messages have very high latency.
also if this probe network reduces the transmission costs to normal terrestrial levels (and not requiring , say, a 400kw tx dish..) it could drastically increases the utility of the link -- and all of this without discussing how much bandwidth a link network across the stars might possess compared to our current link to Voyager..
(this is all said with the presumption of a reason to have such distance communications channels.. )
Seems like the problem OP is trying to solve for here is not latency, it's signal power and redundancy.
You're exactly right and thank you for carefully reading! I very explicitly said that there was a multi year round trip for information even in the best case (e.g. Alpha Centauri), to get out ahead of the well-actually's.
As you noted, some of the gains could be signal power, redundancy, the ability to maintain a quality signal over arbitrary distance; but most importantly, seeing the universe from the perspective of the lead probe in the relay, some arbitrary distance away.