Saying farewell is hard, and in the case of the Voyager 1 & 2 spacecraft doubly so, seeing as how they have been with us for more than 47 years. From the highs of the 1970s and 1980s during their primary mission in our Solar System, to their journey into the unknown of Deep Space, every bit of information which their instruments record and send back is something unique that we could not obtain any other way. Yet with the shutting down of two more instruments, both spacecraft are now getting awfully close to the end of their extended missions.
Last February 25 the cosmic ray system (CRS) on Voyager 1 was disabled, with the Low Energy Charged Particle Instrument (LECP) on Voyager 2 to follow on March 24. With each spacecraft losing about 4 watts of available power per year from their RTGs, the next few instruments to be turned off are already known. Voyager 1’s LECP will be turned off next year, with that same year Voyager 2’s CRS also getting disabled.
This would leave both spacecraft with only their magnetometer (MAG) and plasma wave subsystem (PWS). These provide data on the local magnetic field and electron density, respectively, with at least one of these instruments on each spacecraft likely to remain active until the end of this decade, possibly into the next. With some luck both spacecraft will see their 50th birthday before humanity’s only presence in Deep Space falls silent.
Thanks to [Mark Stevens] for the tip.
So can we improve upon Voyager 1/2 and the 635,266km/h fast Parker Solar Probe? Build something longer lasting and eject it from our solar system at a new record breaking speed?
Is the interstellar plasma flow worth for continued studying?
I think there’s a reason all three of those examples are probes that kept going after their primary mission. Launching something with the energy to escape not just Earth’s gravity well but also Sol’s is very expensive. It tends to be easier to sell it as “this thing is going to Jupiter and by then it will be on it’s way out of the system”.
Well my thoughts were about what did we learn thus far to do it even better, if the research is worth it. Voyager 1/2 are our legacy as humans with the golden records.
A faster probe that could erect a solar sail and might reach a distant star (Alpha centauri) in many thousand years:
(40 233 600 000 000 km) / (635 266 km/h) =
7 225 years
I’m aware it’s a leisure to ponder about the sweet things in life such as science in an ivory tower. Send it as follow up message for Voyager 1/2 to tell where we went wrong in the last 47 years.
Parker only goes that fast because of orbital mechanics when it’s at perihelion right next to the sun – I don’t think we have the capability to eject anything from the solar system at anywhere near that speed (though the solar sail idea is pretty cool)
A lot of the seventies probes also benefited from a very rare planetary alignment for gravity assist. It would require even more propellant now.
Has anybody done (I’m sure someone has) an Oberth-effect simulation/calculation of how fast we could get an interstellar probe going if we slingshotted it past the sun at the distance of the Parker perihelion?
I suspect at that speed a gravity assist from (e.g.) Jupiter will be peanuts in comparison.
Slingshotting around the Sun gives exactly zero increase in speed relative to the Sun. That’s not how slingshots work.
Slingshots around Jupiter works because you’re stealing orbital speed from Jupiter.
Oberth just deals with the efficiency of a reaction, rocket engine (higher initial speed gives greater motor efficiency). You might combine those effects with a slingshot as well, to also steal orbital energy.
To expand on what Pat said, gravity slingshots do nothing for your speed relative to what gives the slingshot, it’s only relative to other objects. For example, a gravity slingshot using the moon can speed you up or slow you down relative to Earth, while one using a planet will speed you up relative to the sun. Theoretically, if you started far enough away, a gravity slingshot using the sun would speed you up relative to the center of our galaxy, but it wouldn’t affect your speed relative to our solar system.
Once again he’s talking about the Oberth effect, which is an increase in propulsive efficiency which occurs when you are diving down into an object’s gravity well from a high elliptical orbit and you do a burn at the point with the highest velocity (periapse). “Slingshot” isn’t exactly the correct term, I think he mixed those up but that’s a rather informal term anyway.
https://outsidetheasylum.blog/an-actually-intuitive-explanation-of-the-oberth-effect/
Yeah, the ‘slingshot’ part is what threw me off when I read it. That and comparing it to a gravity assist: the Oberth effect multiplies a burn, whereas a gravity assist just gives you free delta-v.
So you can’t really compare the two: if you say, for instance “you can either do a gravity assist around Jupiter and then another around Saturn, or you could do a 5 km/s burn at perijove during a Jupiter gravity assist” you might think the second is easier… except it requires you to have enough fuel for a 5 km/s burn, whereas the first just requires you to do your orbital mechanics. The logistics of having a significant extra stage on space probes is really high.
No speed increase if you don’t perform a burn at perihelion, you mean.
The whole point is to do that burn, to take advantage of the Oberth effect.
Essentially you are gaining the potential energy of all the propellant you carry down the well, and turning that into kinetic energy at the bottom, slingshotting your way out at much increased speed over simply burning that propellant at (say) the distance of Earth from the Sun.
“to take advantage of the Oberth effect.”
Oh, crap, I misread your comment! Man, and I could’ve looked so cool, too, because I could’ve just pointed you straight to the Interstellar Probe website:
https://interstellarprobe.jhuapl.edu/
which has an entire appendix just for that! Hilariously it actually uses a Jupiter gravity assist just to get you to the Sun in the first place and would be way closer than Parker (almost 360 km/s!).
Short answer is “it’d be cool except it’d take so much extra mass and effort to get there it ain’t worth it.”
A previous HAD comment mentioned that using a gravity slingshot can just be thought of as if the objects were billiard balls bouncing off of each other (albeit one is very small and the other very large). You only gain velocity when you bounce off an appropriately moving object.
i can imagine a space telescope sent out to the solar gravitational focal point would gather considerable data on the way. getting there, and powering it, and do it in the lifespan of those who started it, and the power supply, would all be considerable challenges. also given the orbital velocity there is damn slow, you will need to send out many such missions to scan different areas of interest in the sky. alternatively we may find something interesting in the oort cloud. these are all decades long missions with current propulsion technologies.
Yes, we can improve upon the Voyagers. JHUAPL did a study for an interstellar mission in ~2019, finding the highest speed we could launch a mission to outside the heliosphere. Using then-current technology with minimal development (a larger solid booster based on the STAR 48) they found a speed of 7 AU per year (twice as fast as the Voyagers) was the highest achievable.
They studied things like an Oberth-Kuiper maneuver, slingshotting around the sun, but found the heat shielding required to get close enough to the sun to get any gain was so heavy the net gain was zero.
I always feel a profound sadness when one of our precious few enclaves out into space falls silent.
They aren’t just machines. They carry with them the essence of our species. They are the best of us.
Absolutely. What’s also notable, the journalists who wrote about the Voyager missions back then did behave, were respuctful.
Even though it was clear to them that the articles about space things wouldn’t make them headlines.
They understood how important the Voyager missions were.
This kind of insight wasn’t taken for granted, I think.
Don’t anthropomorphize machines!
They hate that.
WH40k also taught me that you should never fully paint them, that you should always leave a little bare metal… To appease the machine-soul
I see what you did there, lol.
We also still have New Horizons operational after 18 years:
https://science.nasa.gov/mission/new-horizons/
Correction, 19 years.
There’s the new horizon spacecraft, could have been designed to take the place of Voyager, it’s past Pluto now….
And whether or not you can actually communicate with it to do extra stuff as a secondary mission
It’s been mentioned here before, but worth a repost: A documentary of sorts on the Voyager team,
“It’s Quieter in the Twilight” film.
Despite the rather Hollywood-esque tagline:
In an unremarkable office space, a select group of aging engineers find themselves at the leading edge of discovery. Fighting outdated technology and time, Voyager’s flight-team pursues humankind’s greatest exploration.
It’s actually good: https://www.itsquieterfilm.com/
Some wise sage please explain how powering off science instruments will extend the lifetime of remaining hardware. The RTG’s decay plutonium at a constant rate, correct ? Thermoelectic generators would then be producing usable energy at a constant rate. Someone correct this if incorrect.
Alternator in the car, always running when engine on.
It doesn’t really give a crap if the high beams or the radio is on or off, it’s
still producing energy – albeit to perhaps keep charge on the battery.
So turning off the radio isn’t going to do jack to how long I can run
the high beams – unless the engine runs out of gas ( plutonium on the
RTG).
So what’s the drawback of keeping all instruments powered on ?
The RTG’s are still producing usable power (it’s not throttable to extend
it’s life time – unless they are ??? – in which case, it would make sense
to reduce load demands).
The power output of an RTG drops over time. Therefore, to keep the draw of all active systems less than the output available, we turn off some systems.
Radioactive decay is logarithmic and electricity is produced from the decay. Plutonium-238 has a half life of 83 years, so if it was producing 100% of its maximum power at launch then after 83 years it would be producing 50% and after 166 years it would be producing 25%. As the power output slowly declines, instruments and other electronics need to be shut down one at a time to keep the power demand lower than the decay energy.
The power output from the RTG is constantly decreasing (article says by 4 W/year). Part of this is due to nuclear decay and part due to the thermocouples wearing out.
The instruments are useless after the radio stops operating. By turning off some instruments, you leave more electricity available to transmit the data from the remaining instruments.
The main problem isn’t even the isotope so much, but the “battery” itself.
It’s dissolving, so to say, in layman’s language.
Too bad the Voyager can’t turn cosmic radiation into energy,
like a crystal radio could when it receives an AM station.
That would be enough to power an Arduino Uno, perhaps, and a low power transmitter.
A morse signal or a carrier-based beacon with exact intervals could be used here.
The doppler effect could be measured that way,
which maybe would give information about time dilatation effects and gravitational changes.
Which will happen first our ability to communicate with them due to distance and TX power available or all their all their instruments turned off and nothing data to transmit.
Their mere existence is data to transmit.
Much of what we have learned about the gravitational affects out there has been from studying the doppler effect from the carrier wave of their transmitter(s).
Good point. I wished there was one space probe that had nothing else, except for a star tracker for Canopus to keep antennas pointed to earth.
No computer, no modern digital technology (just basic TTL), just a floating beacon with a big, oversized “battery” (RTG).
The advantage would be that future generation would require no in-depth knowledge about obscure data formats.
There would much that could break, either.
It could use nuvistors, special electron tubes or rugged transistors that last forever.
An interstellar Sputnik, so to say.
Maybe with an atomic clock on-board and an auxiliary transmitter,
so it could send exactly timed pulses like a pulsar.
Having one such single-purpose probe would be nice, even if only being sent out once a hundred years!
“nothing else, except for a star tracker for Canopus to keep antennas pointed to earth.”
Star trackers tell you where you’re pointing. They don’t magically point you there. In order to point, you need thrusters. And fuel. And heaters. And something that can calculate and adjust.
You don’t get longevity by avoiding things that can break. You get longevity by redundancy. And a ton of luck – both Voyagers are full of broken stuff, and it’s a friggin’ miracle that the failures have been in such perfectly combined ways that both of them still work.
Agreed on the luck and small miracles and hard work on Earth that kept the Voyagers going. But, funny, the most complex systems ever launched are single-string redundant: If anything goes wrong, the mission ends (or is seriously curtailed), no backup, no second try. Like James Webb’s deployment or Curiosity’s sky crane and the Seven Minutes of Terror. Put the effort into designing things that are robust and reliable, instead of doing less than 100% on engineering the thing in the first place by squandering resources on redundant parts.
Hi, my bad, I thought of the star tracker and the attitude/articulation/trajectory control system as working together as one system.
I wasn’t going into detail here, my bad. Maybe I should have had.
I guess I think I kept it simply because I wasn’t sure if spin-stabilized satellites and probes are still in fashion or if there are other concepts by now.
Deep space probes can’t maintain orientation without active maintenance. Perturbations would just add up.
Nothing data to transmit. The actual distance/TX power limit is quite a lot farther, especially considering the fact that the DSN antennas have gotten more sensitive. The Voyager Telecoms paper didn’t even list a year limit for the 70 meter antennas because effectively never.
…or nobody here to receive.
No! Bad! No immanentizing the eschaton!
No creating the Torment Nexus either, I suppose?
As a non techie I read a similar article recently and a few things struck me. OK so 45 y/o satellite is having some scientific stuff I’ll never understand shut down to conserve power, makes sense. Read an article a while back about NASA having to move code to run on some other chipset to reduce power, amazing , this thing is 45 years old.
In an AI / Robotic revolution, hardly huge news.
Then I realised why all this is all really mind-blowing…
It’s 13 Billion miles away
“In an AI / Robotic revolution, hardly huge news.”
Is there? Real neural nets had been experimented with in the lates 70s and 80s.
What we have now are LLM, large language models. Sisters of Eliza, chat bots.
They seem smart, but so did Eliza in the 60s.
If you ask them about their private life they will happily tell you,
even how much they enjoy swimming and making barbecue with friends.
The main difference to Eliza, however, is a gigantic source of “input” (to use Johnny 5’s terminolgy).
Also, the impeding danger is something that many don’t see:
What happens ifbthe human made “input” is finally being replaced by the output of other LLMs?
Especially if it’s false information? The illusion of a wonderful world of AI that knows answers to everything may fall apart.
“Then I realised why all this is all really mind-blowing…
It’s 13 Billion miles away”
I’d also be mind blown to hear about a washing machine on earth that runs for 50 years.. :)
My ex wife has one. It’s a Maytag model A207 I bought her in 1974. I’ve done minimal maintenance on it in all those years, a drive belt, timer and rebuilt the water inlet valve. Ditto the DE606 dryer i bought at the same time. It’s had a heating element and drum bearing replaced is all. Both still working fine today.
The Deacon’s Masterpiece
or, the Wonderful “One-hoss Shay”:
A Logical Story
by Oliver Wendell Holmes (1809-1894)
http://holyjoe.org/poetry/holmes1.htm
No matter what or how long the probes will never leave our solar system
Incorrect. Both spacecraft left our Sun’s heliosphere and are travelling in interstellar space. Voyager 1 left in 2012, and Voyager 2 in 2018. They each travel about 1,000,000 miles a day.
And in 300 years they will reach the oort cloud (still in the solar system) and then take roughly 30,000 years to pass through it, finally exiting the solar system.
V’Ger!
To those being sad about the Voyager missions final end:
Don’t be sad, be glad that it happened and that the mission can soon rest in peace and dignity.
It’s a memento to an era in which NASA had still been respected internationally as a capable, science-oriented space agency that was open to the public.
Who knows what the future brings and if NASA can survive.
The current news aren’t so flattering, lots of populism and money issues.
In the end, NASA might shut doors shortly before the Voyagers run out of power.
https://arstechnica.com/space/2025/03/white-house-may-seek-to-slash-nasas-science-budget-by-50-percent/