> In the year 2000, 23 years after production, the radioactive material inside the RTG had decreased in power by 16.6%, i.e. providing 83.4% of its initial output; starting with a capacity of 470 W, after this length of time it would have a capacity of only 392 W. A related loss of power in the Voyager RTGs is the degrading properties of the bi-metallic thermocouples used to convert thermal energy into electrical energy; the RTGs were working at about 67% of their total original capacity instead of the expected 83.4%. By the beginning of 2001, the power generated by the Voyager RTGs had dropped to 315 W for Voyager 1.
There's also a nice picture of one deployed on the moon. The dust on the moon's surface looks spectacular in that picture.
https://en.wikipedia.org/wiki/Radioisotope_thermoelectric_ge...
That was also one of the many issues that cropped up during Apollo 13. They too had an RTG on board that was supposed to stay on the moon[1].
According to the book "Lost Moon" by Lovell and Kluger, a potential explosion of the Saturn V during launch was accounted/planned for, but the RTG "coming home" together with the LEM wasn't.
IMO the book was a bit hazy on how that situation was addressed exactly, but according to Wikipedia that RTG is currently resting somewhere deep in the Pacific[2].
Also an interesting read on that topic is the SNAP program itself that developed the technology in the first place, even shot entire mini-nuclear-reactors into earth orbit[3] and resulted in some stereotypical 1960s nuclear safety shenanigans/mishaps during testing[4][5].
[1] https://en.wikipedia.org/wiki/Apollo_13#Experiments_and_scie...
[2] https://en.wikipedia.org/wiki/Apollo_13#Reentry_and_splashdo...
[3] https://en.wikipedia.org/wiki/Systems_for_Nuclear_Auxiliary_...
[4] https://en.wikipedia.org/wiki/SNAP-10A#Safety
[5] https://en.wikipedia.org/wiki/Systems_for_Nuclear_Auxiliary_...
Given that radioisotopes decay with a halflife pattern, I would expect that you'd see a 16.6% drop in capacity every 23 years. So something like:
1977: 100% (470 W)
2000: 83.4% (392 W)
2023: 69.6% (327 W)
1977: 100% isotope * 100% coupling efficiency -> 470 W (100% of capacity)
2000: 83.4% isotope * 80% coupling efficiency -> 314 W (67% of capacity)
2023: 69.6% isotope * 60% coupling efficiency -> 196 W (41% of capacity)
– how far Voyager 1 has already traveled ~150 AU or ~0.002 ly [1]
– how much farther it could go in 40,000 years ~1,000,000 AU or ~17 ly [2] [3]
– the visible diameter of our Milky Way ~6,000,000,000 AU or ~100,000 ly [4]
[1]: https://voyager.jpl.nasa.gov/mission/status/
[2]: https://voyager.jpl.nasa.gov/mission/interstellar-mission/
I think we should have a new mission, send out huge amounts of tiny crafts in all directions at the same time, to get a sort of Google street view of our solar system and interstellar space. I bet we could create crafts with modern tech that where tiny and much less expensive that the original pioneer and voyager crafts.
It's harder than you'd expect. At that distance solar panels are essentially useless, so you do need nuclear power, and you're continuously exposed to cosmic rays, so you need radiation-hardened electronics. Both of these drive up the cost. The Voyagers also had the the outer planets in alignment to give it a gravity assist, so if you want to get there on the same time scales you'll need a more powerful rocket as well.
Anyway if they used the same technology, but sent spacecraft out into space from locations all around the Earth at the same time, then we could gather data as this fleet headed into deep space.
Like one of those big planet explosions in science fiction movies, but instead of an explosion, just tiny space crafts.
That’s why we need a way to create gravity artificially if we are going to do any space exploration. It would be a bit crap if we could only move in 2 dimensions.
silly question: can CRs be harnessed for power?
Has anyone ever updated Commodore's Visible Solar System? Very inspiring.
https://www.lemon64.com/?mainurl=https%3A//www.lemon64.com/g...
But it is a sort of map, ok probably Google maps rather than street view :)
"Oh, it's all black here too" ;)
More at https://www.nature.com/news/2008/080702/full/454024a.html
Lithium batteries do get ever so slightly heavier when charged, but it's basically undetectable.
The mass associated with those chemical bonds is miniscule compared to the protons, electrons, and neutrons, but it is not zero.
Ah, but it is. E=mc^2 is always true in the reference frame where the object is stationary. (We assume that we are co-moving with the windup car.) A spring under torsion is heavier than an unwound spring.
Does it have more (invariant) mass?
100% of the mass difference is converted into energy.
I agree, if you're deploying 1 kg of fissile material, only 0.1% of that will be converted to energy. We should talk about energy per mass of fissile material, not energy per mass of "mass difference".
Nuclear batteries are extremely reliable though, as they are fully solid state. A Pu-238 battery can emit useful amounts of power for upwards of a century, and there is virtually nothing to break.
Through (according to Wikipedia) the party might end in just a few years: https://en.wikipedia.org/wiki/Voyager_1:
> Voyager 1's extended mission is expected to continue until about 2025, when its radioisotope thermoelectric generators (RTGs) will no longer supply enough electric power to operate its scientific instruments.
Sun’s gravity well is so immense that escaping it requires a very, very large amount of energy. I am not sure if it could be done with conventional rockets with current technology, without multiple gravity assists.
Edit: As the child comment says, it seems to be possible with current technology. It is very exciting!
Yes, it can. New Horizons is escaping the solar system only a little bit slower than the Voyager probes, and it was already on an escape trajectory before its single Jupiter gravity assist.
The Voyagers didn't have an extrasolar target either, they were meant to visit the outer planets. If we're looking at probes that leave the solar system after their original mission, we launched New Horizons in 2006 to Pluto, and it's currently in the Kuiper Belt on its way to leave the solar system.
Meanwhile, there are actual interstellar probes being planned, in addition to several missions to the outer solar system (and which could end up in interstellar space afterwards).
And there's a ton of missions planned for the inner regions of the Solar system -- space exploration is still a thing and there's a lot of exciting things happening.
Theoretical is still theoretical. We have no functioning propulsion that can exceed what the probes are currently travelling at.
Or course combining technologies in a new way comes with lots of engineering challenges, but it's a smaller leap in technology than e.g. the first moon landing.
Also really interesting is the Voyager FAQ, even from the first question (about whether the cameras could be turned back on). "Mission managers removed the software from both spacecraft that controls the camera. The computers on the ground that understand the software and analyze the images do not exist anymore."
We are in one of the very few professions where the speed of light is considered annoyingly slow. Just three days ago there was a thread of people lamenting that the closest Hetzner datacenter is about 50 light-milliseconds away
> 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
[0] https://space.stackexchange.com/questions/3520/when-will-new...
> Provided Voyager 1 does not collide with anything and is not retrieved, the New Horizons space probe will never pass it, despite being launched from Earth at a higher speed than either Voyager spacecraft. The Voyager spacecraft benefited from multiple planetary flybys to increase their heliocentric velocities, whereas New Horizons received only a single such boost, from its Jupiter flyby. As of 2018, New Horizons is traveling at about 14 km/s, 3 km/s slower than Voyager 1, and is still slowing down.
"…and far from home, untouched by these remote events, the Voyagers, bearing the memories of a world that is no more, will fly on."—C. Sagan
22Tm.
Or, 22 terametres from Terra.
It makes more sense, generally, to send probes to where things (planets, moons, dwarf planets, asteroids, comets) are, that we can reach in reasonable time (years, possibly a decade or more for outer targets).
"Every direction" just takes you to deep space. And that's not going to be particularly illuminating, though a few such probes (say, a high- or low-solar plane one) might be interesting.
Spraying random probes in all directions makes lttle sense.
Voyager 1 won't reach the Oort Cloud, if it in fact exists, for another three centuries.
At least, according to ESA [1].
Though this is well outside my area of expertise.
[1] https://mars.nasa.gov/internal_resources/788/