> Today’s mind-blowing stat: Voyager’s transmitters use just 23 watts, roughly the same as an incandescent refrigerator bulb, yet we are able to interpret the 0.1 billion-billionth of a Watt that makes it to our 70 m dish from 11 billion kilometers away. Both spacecraft are expected to last another 5 years, until their plutonium batteries decay beyond usefulness and they drift with our golden record more or less forever among the stars.
23W with extremely high gain though. It was difficult to find a number, but this source [0] gives the gain at 47dB (dBi or dBd isn't specified). With that high of gain, the effective radiated power is over 1 million Watts (because it is concentrated into a very narrow beam).
Also using phrases like "0.1 billion-billionth of a Watt" is misleading, and not how radio signals are actually described. For example 0.1 million-billionth of a Watt sounds pretty small too, but describes the power level of a usable, and not particularly uncommon LTE signal level.
Here's a related thought: if we ever manage to send a probe to the closest star, what a tough problem communication with home will be. The distance is about 2000 times higher than where Voyager is now. So the signal will be about 4 million times weaker due to the quadratic attenuation alone, and maybe 100 million if we consider the absorption by the interstellar medium. On top of that, when the probe will phone home, it's going to be a few seconds of arc away from a phenomenally bright source of electromagnetic radiation: the star itself.
You can fix this by using a bigger transmitting antenna (but Voyager's is already 3.7m, not small at all), or a bigger receiving antenna (the current ones are 20m). Or a stronger signal. But it appears we'd need to go from 23W to GigaWatts .
One thing is sure: we won't be able to send a pound-size probe.
The gain of a 3.5m parabolic antenna on the tx end, and they're using from 45 to 70 meter size dishes on the earth end to communicate with them. The NASA goldstone 70m dish has some serious gain.
I heard a rumour that by the time they've gotten to another solar system, they will have evaporated into a metallic cloud; that's how long this next part of their journey is.
Why would they? They will be very cold. Occasional cosmic rays aren't enough to evaporate them. They can last hundreds of thousands of years, if not millions.
Millions of years? Fat chance. A few days ago this post https://news.ycombinator.com/item?id=21327269 explained that during the galactic collision of the Milky Way and Andromeda in 4B years, no two stars will likely collide because of the sheer amount of empty space. Keeping that in perspective, I highly doubt that Voyager would find its way anywhere in some mere millions of years.
Technically you're talking about sublimation rather than evaporation. And no, it won't be very likely for the Voyagers to disappear. Most likely they will be damaged by impact or get absorbed by massive object, but sublimation at 10K will take a very very long time.
I don't have the data, but if you want to calculate the rate of sublimation, you need to look at the vapor pressure of various metals at interstellar temperatures.
But they're in interstellar space. I imagine high-energy collisions (with hydrogen atoms or loose protons) would be a more likely cause of evaporation, and I don't know the numbers for that.
Google says that's about a gram of hydrogen. Is that enough to destroy a craft? I have little intuition, but I imagine touching a gram of 55,000-degree (Farenheit) anything would be destructive.
Will the craft be radiating heat away from itself?
TL;DR two data points (trajectories) is not enough to understand the dynamics of the heliopause, as we saw different flow in each, but it’s all we got.
I cannot imagine the feeling of pride you must have if you worked on the Voyager program in any capacity. The first interstellar spacecraft, over 40 years old, and someone's still writing FORTRAN or ASM for it. So cool.
If by "outlive" you mean "continue to exist"... the Voyagers have a finite useful lifespan defined by the output of their RTGs, and that's expected to drop below useable levels sometime around 2025 (for both craft). But they'll still be out there, barring a random encounter with an asteroid or something.
I think that two grains of sand on beaches of the opposite ends of the Earth are probably more likely to interact than a random rock and a tiny satellite that has left the Solar System into interstellar space.
In fact, in about 40,000 years, Voyager 1 will pass within about 1.6 light-years of the star Gliese 445. It's also likely that it's as close to a star as Voyager 1 will be again, ever.
Space is pretty empty compared to Earth or even our own Solar System.
I know this sounds contrived, but imagine the mission beeing not reliant on continous operation, but just a operation of any kind to continue.
Could one just harvest the background radiation for energy, and switch on, once some storage capacitator reaches a critical threshold. A device harvesting this weak, but continous energy source, could work indefinatly?
Telecom satellites in geostationary orbit will be up there on a geological time scale. Humankind could knock itself down to a pre bronze age level of technology and rediscover spaceflight long before the orbits of any of them decay into the atmosphere.
If they were travelling in a straight linear track across the Milky Way, they'd be about 275 thousand light years from Earth, or somewhat further from us than the Milky Way is across (150k - 200k light years). Current speed of Voyager 2 relative to Earth is 5.4 * 10^8 km/yr, a half-billion km/yr, or 0.05 millilightyears/yr.
In truth, they'll be orbiting the galactic centre in an orbit somewhat offset from the Solar System. The Milky Way will have completed about 20 rotations. No idea what the resulting offset would be, but all but certainly somewhere within the galactic disk itself.
Space is big. You just won't believe how vastly, hugely, mind-bogglingly big it is.
> Space is big. You just won't believe how vastly, hugely, mind-bogglingly big it is.
I liked Neil deGrasse Tyson's description of how what we call space is still ridiculously close to our planet and how far away everything else actually is, using a standard classroom globe for scale: https://youtu.be/Tt0uV5d8tss?t=99
Actually, I believe they stand a decent chance of some future billionaire recovereing them and putting them into a museum or a private collection in a hundred years or so.
That writeup, while accurate, was back in 2013 before Starship / Super Heavy was a serious concept. And if everything pans out with it, we can get huge amounts of stuff up a lot cheaper. It even says that an ion drive (based on 2013 technology) will work, but we will have an issue with re-capture once it gets to Earth.
That can be solved with a much larger ion drive, which will be much cheaper to launch (along with appropriate amounts of propellant) using Starship (or its future successors). And if a wealthy individual that has everything wants to retrieve that golden record for his personal collection, and is willing to spend a couple billion on it, well I'm sure that Musk's great grandkid will be more than willing to oblige.
Interesting thank you. That's what my second question was going to be, if it could stop it and bring it back and how hard that might be. Seems the answer is- very hard.
Maybe it's power of simplicity. When I coded 8086 assembly program, it's less likely to have bugs. There are just a few registers to use, most things are next to bare metal. Like what could go wrong moving hex around if we know exactly what we are doing.
Yeah...the stuff we do in most industries today is so complex that if we used Assembly or even C, nothing would ever get done. The problem is the abstractions we need (OS, high level langs) create many additional layers of complexity that can fail and bite you.
I might have a rudimentary understanding of electronics and digital design and could write Assembly and kind of understand the full toolchain from A to Z, but on a modern computer (hardware, BIOS, OS, programming language...etc) there is no hope.
Everything is a trade-off. If I had to write code for a probe today I would opt for the absolute simplest hardware and software so there is a lot less room for error.
A lot of modern complexity is kind of incidental. We need to deal with GUIs, protocols, out of order execution, parallel and concurrent programming. The core of things didn't change that much, you store a bunch of things in memory, you sort then, you search things, you move them to disk storage, you retrieve them and so on.
If you wanted to run a factory floor and the machines in it just by using either assembly or C and our knowledge of a bunch of algorithms, it would probably work, but without all the advantages we leverage by modern technologies. Instead of "Select ProdOrders where....", considering we once have done a bunch of "create table" and "create index", we would have to manually define the disk structures layouts by hand, hand write sorting routines for each one. It would take armies of programmers, but a single iphone would suffice for all IT needs of a large multinational bank. The user interface would be terrible, you'll need speacialized operators for simply entering data on the system, or extracting results.
But in a space probe, you don't need to care about user interfaces, ever-changing business requirements, nice integration points, so you could probably get away with a very simple and primitive time-sharing os, in a single-threaded CPU, by using only C and a barebones standard library, dropping from time to time to inline assembly.
Actually it is an interesting imagination exercise. It makes me think that even if a catastrophic event happened like an EMP, we would probably be using computers again to help rebuild the world in less than 20 years. As long as we had people with the knowledge to deal with the basics.
IMHO, a much more reasonable approach would be to have a minimalistic bootloader running on a separate hardware with some kind of redundancy + a more or less regular system for the rest of the logic. If the cost of error is simply deploying a patch using a dedicated high-reliability channel, you don't need to suffer and restrict yourself to stone-age technology.
My heart is really on edge for the folks working on JWST. Decades of work perched atop a giant bomb to get into space, then it's like six months from T-0 on the launch pad to first science images. Errybody going to have ulcers.
They got Chuck Berry's Johnny B. Goode and Izlel je Delyo Hagdutin on it so at least they captured both America and the centuries-long ripple of enmity between various Eastern European Slavs and the Anatolians.
"It was amazing to work on this cutting-edge data from spacecraft that were launched before I was born and still doing amazing science"
I'm equally amazed (as a non-scientist) when I reflect that reading about the Voyager missions was one of the first things that opened up the infinite wonders of science to me some thirty years ago, and here we are still getting new data and new riddles to solve from those same probes.
Voyager 1 and 2 had to happen in a narrow window of time to take advantage of favorable planetary alignments. If we launched something like this now, it would take an order of magnitude more fuel and still not be able to go as fast. The next window for exploring interstellar space so efficiently isn't until 2150.
Of course there are other long-term missions we could be trying now; but it's not quite so straightforward (due to the mechanics of space-time) as we're led to believe.
For that matter, we could consider this whole anthropocene climate change thing we're doing to be one long-term experiment. You're welcome, children of the future, for all this wonderful data we're generating for you.
What we use the SpaceX starship - fully refueled in orbit - as a second stage? Put a 3rd stage in/on it to launch a probe. Fire the 3rd stage down in jupiters gravity well to get the most from it, or whatever trickery can be had. I suspect we could get to the heliopause a bit quicker even without such nice planetary alignment.
With SpaceX pushing down launch costs, it would really be possible to launch these probes regularly and in large nunmbers. Maybe there could be an NGO that collects donations and builds thousands of always the same exploration probes, to reduce cost. If each proble was named by whoever donated the money for it, that would probably increase donations further.
I was a kid, and I remember the kind of science mini encyclopedias parents used to buy for their kids on the early 80's.
And one thing that I remember from one of those books is a big two page full color photo of voyager.
It is amazing to know that this thing that fascinated me when I was a little kid, it is still travelling and doing useful science out there.
>And on the other side of the boundary, the interstellar medium is at least 54,000 degrees Fahrenheit, which is hotter than expected. However, this plasma is so thin and diffuse, the average temperature around the Voyager probes remains extremely cold.
I don't understand this. If the medium is 54,000 degrees wouldn't it have incinerated the probes? How can an extremely diffuse plasma be 54,000 degrees and yet also be extremely cold?
Temperature relates to how fast atoms are moving. If they're moving very fast, then we say it's very hot. Damage from high temperature however requires a substantial quantity of those atoms, not just that they be moving quickly.
But there are very very few atoms in the interstellar medium. They are moving very fast, but there are very few of them indeed.
To incinerate something, there would need to be a lot of atoms indeed moving at high temperature. An isolated atom hitting the probe, even at relatively high speed, won't be doing much incinerating.
It's like a sparrow hitting a building. Won't do much, even it's a fast-moving sparrow. But a billion sparrows hitting it in unison - that might be a problem.
Have you ever reached into a hot oven and grabbed a sheet of tinfoil with your bare hands? The foil is 350F (or hotter) but you don't feel anything because it's so thin and flimsy. There is not enough mass to hold enough energy to hurt you.
seriously? I assumed that it simply cooled more quickly because of high surface area to mass ratio; not that it actually was 400F but I couldn't feel it.
It doesn't make intuitive sense to me but I do understand the explanation.
Not OP, but if you inspect the overlay, just right next to it there's a <script> with a closeOverlay function. OP probably tried to inspect/delete DOM element and found that function.
We may have to wait a while - Voyager relied on a rare once every 175 year planetary alignment for gravitational slingshotting. It's only a shame the whole Grand Tour that Voyager had once been intended to be a small part of never happened.
Depending on the mission there's no doubt other alignments that would give the gravity assist.
Do we have any newer propulsion methods that would make a difference in these super-long-running missions? (I am not a rocket scientist... but I'm thinking along the lines of something like a low-impulse ion thruster that uses a relatively small amount of fuel but can run for a very, very long time)
Yes, the new missions now have a Delta-V of something like 11 kilometers per second, which is insane. For instance, the New Horizons which only took 9 years to get to Pluto had thrusters with a Delta-V of only like 0.27 kilometers per second, so most of the trip was done using gravity assists. Missions now can do some crazy things like orbit two separate bodies.
To put it into perspective, Voyager 1 has a current speed of 17 kilometers per second. So the Dawn craft has most of that trip covered without gravity assists if it wanted. AFAIK there's nothing stopping us from loading up some craft with more fuel and larger ion engines except for launch weight. And even then, if we mastered orbital refueling we could surpass that.
As it stands, the craft can carry approximately the same amount of Delta-V that the rocket that got it into space. Equivalent to tons of fuel from chemical rockets.
> To put it into perspective, Voyager 1 has a current speed of 17 kilometers per second
And the Earth has 30 km/s, yet we don't get Voyager "for free" and then some just from LEO. You can't compare speeds in different parts of the gravity well against each other because then you're ignoring the dv required to get from here to there.
One of the biggest problems is that NASA's Plutonium-238 stockpile is running low, and is only barely being replenished (it was an artifact of nuclear weapon production, at the time). Each of Voyager 1 and 2 used something like 15kg of it for their RTGs. Because they were so heavily powered, the half-life won't power the craft down for decades.
The availability of Pu-238 is why European missions can't go past Jupiter without coordinating with NASA -- politically is impossible for them to produce nuclear spacecraft, but solar power becomes ineffective farther from the sun.
But given that NASA has a limited Pu-238 stockpile, they're only stocking new craft with the minimum necessary to hit the key science objectives.
This was a mostly political problem with Congress kicking the can down the road for 20 years. According to the article they've restarted production although a bit slower than they wanted.
Of course you can't stockpile radioactive materials for too long. Their very nature limits their shelf life. So constant production is necessary if you want to use it on missions.
I wonder how long that reactor would provide useful energy. U-235 has a half life of 700 million years. If it were to last that long, they'd be dealing with thermonuclear Long Now-type problems.
The Kilopower reactor uses a chain reaction to trigger fission so the U-235 will be depleted much faster than the half-life. Wikipedia says its operational life is 12-15 years.
Do you know if the new designs proposed using thermophotovoltaics and silicon-carbide pellets are more efficient than traditional RTGs in their use of plutonium? Eli Yablonovitch mentions work being done at Berkely: https://www.youtube.com/watch?v=lDxJsa8miNQ&t=3280
There's a quote I thought of when you said this. It's from a very old Wired article (back when Negroponte was a part of it) titled "The Millennium Clock" by Danny Hillis:
"I think of the oak beams in the ceiling of College Hall at New College, Oxford. Last century, when the beams needed replacing, carpenters used oak trees that had been planted in 1386 when the dining hall was first built. The 14th-century builder had planted the trees in anticipation of the time, hundreds of years in the future, when the beams would need replacing. Did the carpenters plant new trees to replace the beams again a few hundred years from now?"
I sincerely hope we do launch more deep space probes in the near future, for our collective far future selves.
The original builder felt strongly enough about the oak beams to plant replacements. The restorers, or whoever hired them, did not. Perhaps they knew that 500 years in the future there would be better alternatives and were not as locked into the original design as the first builder was.
Not all such decisions are short-sighted.
Edit: I think it's been shown elsewhere that it is not the date that you launch the next probe that is important, but the speed at which it travels.
Not only that, but according to the article, when New Horizons "runs out of power in the 2030s, it’ll fall silent more than a billion miles short of the heliosphere’s outer edge."
It would be pretty neat if we launched Voyager 3 & 4 around 2150, following the same 175 year cycle "Grand Tour" of the original Voyagers. I also wonder if the power source in 2150 would still need to be a RTG or if we will have an alternative by then.
Do you mean interstellar probes? The Voyager missions were primarily planetary exploration missions, which NASA and other space agencies continue to run with new probes every few years. The interstellar exploration piece was kind of a secondary feature of the missions taking advantage of high speeds from all the gravity assists along the way.
I don't think we'll see a dedicated interstellar probe for a long time. It just takes too much energy to get out that far in a reasonable amount of time without radical designs or a big leap in propulsion technology.
The propulsion technology for an interstellar mission is available today, there are proposals for probes powered by RTGs or even nuclear reactors and driven by ion engines. Jupiter-Saturn conjunctions that can be exploited for gravity assists happen every 20 years or so: https://en.wikipedia.org/wiki/Interstellar_probe#Proposed_in...
It's entirely a political problem. There is no will to fund such a mission, and what's worse is that in the US funding is approved year by year.
In nuclear engines the fuel and propellant is separate. I keep wondering how much gas a rocket needs to take with it in order to have something to push against. Nuclear fuel is incredibly energy-dense, but the density of the gas used for propulsion in a nuclear rocket can't be much different from what's used in conventional rockets.
The JIMO mission was supposed to have 12 tons of xenon on board, a substantial amount of the yearly production (~ 70 tons). You do wonder how Elon Musk's Starlink madness will affect the xenon price.
The StarLink satellites use krypton thrusters instead of xenon [0]. They need more electic power to run, but produce higher specific impulse [1]. And krypton is cheap.
There's a (partly funded!) project to send a 'chain' of probes to α Centauri[1], as long as they don't need to slow down when they get there, they can shoot right through and relay results back, as I understand it.
With launch costs plummeting it may be possible to launch a bigass booster and give an interstellar probe a real kick even without a magical planetary alignment.
The question then becomes: what instruments would you put on this that would tell us something the Voyager probes have not? What is your mission beyond "making something go even further away from us"?
As per the article, exploring the trailing edge of the heliopause would be interesting and is something that hasn't yet been done. But yes, presumably instrumentation has also improved over the last 50 years, so hopefully we could get better data as well.
Most of the thrust of rocket is loss to get out of the earth gravity well.
I believe that this is wrong.
The Earth weighs 5.96e+24 kg and has radius 3.37e6 meters. The Sun weighs 1.98e30 kg and our orbit has radius 1.496e11 meters. That means that the potential well for getting away from Earth is about 11,800,000 joules/kg while for getting out of the Sun's gravity well is about 882,800,000 joules/kg. Assuming that I did the math right, that's about 7.5 times as hard.
It therefore takes a lot more energy to climb out of the Solar System than it does to climb out of Earth's gravity well. Voyager got a LOT of energy from those gravitational slingshots.
You're trying to compare apples to apples here, when the situation we have is actually apples to oranges ;).
A probe has to launch from the surface of the earth. But counterintuitively the probes start out already in solar orbit, even before they're launched -- because the earth is in solar orbit. More than half the energy required to achieve escape velocity is needed just to get into a roughly circular relatively low orbit around the gravitating body you're trying to escape from, and by virtue of being launched from the earth the probes get that velocity for free. Furthermore, the earth's orbit isn't really "low" with respect to the sun. We're fairly far out there, so the fraction of the energy needed to go from earth orbit to a solar escape trajectory is even less.
Put another way: a probe launched from the earth gets no help leaving earth's gravity well. But once it does it gets a huge automatic gravity assist from the earth itself as it enters solar orbit.
There's a saying among KSP players: "Orbit is halfway to anywhere".
It takes a lot of energy to escape Earth's gravity well. It takes a comparatively tiny amount to escape the Sun's, as a sibling poster pointed out. It would be actually harder to visit, say, Mercury, as you now have to shed all the energy Earth has given you for free, in order to "fall" into the Sun's well.
Voyager wanted to visit multiple planetary bodies – changing orbital parameters is not cheap. But if all it wanted was to get out of the system, burning straight out would probably be cheaper (in Delta-V terms). The closer to Earth the better, for the Oberth effect.
This is correct. On my astrodynamics written qual, one of the questions was whether it would be more energy efficient to solve Earth’s trash problem by launching garbage into the sun or into deep space. Surprisingly, the answer turned out to be deep space, and it wasn’t that close.
> Wouldn't it be possible if we launched from the moon instead?
It would be cheaper in fuel terms, and require less thrust, but it'd also require us to manufacture propellant on the lunar surface and fly everything we can't build there from Earth (and landing on the Moon is purely propulsive).
> By atomic composition, the most abundant element found on the Moon is oxygen. It composes 60% of the Moon's crust by weight, followed by 16-17% silicon, 6-10% aluminum, 4-6% calcium, 3-6% magnesium, 2-5% iron, and 1-2% titanium.
You have oxygen. You have aluminum. You can now make a solid rocket. There's some magnesium there too if you want to use that instead.
It's kind of hilarious that the hardest thing to find in the inner solar system, off Earth (and, of course, the Sun), isn't precisely water but hydrogen.
I wonder if these probes may rather be captured by humans in a few hundred or thousands of years and placed in museums back on earth. With faster space travel techniques that is a possible scenario.
I wonder if there is a documentary with visual explanations. It would be amazing to watch and understand.
I recently saw a mind-bending documentary[0] titled "Timelapse of the future", there's a brief mention of Voyager, it shows what happens to the universe in the long run and how it ends.
It is kind of weird to me that they say the Voyager craft are in interstellar space, when their distance in AU from the sun is a great deal less than the aphelion of Sedna's orbit and other sednoids.
> Today’s mind-blowing stat: Voyager’s transmitters use just 23 watts, roughly the same as an incandescent refrigerator bulb, yet we are able to interpret the 0.1 billion-billionth of a Watt that makes it to our 70 m dish from 11 billion kilometers away. Both spacecraft are expected to last another 5 years, until their plutonium batteries decay beyond usefulness and they drift with our golden record more or less forever among the stars.