Comment by HenryBemis | Hacker News Reader

Comment by HenryBemis | Hacker News Reader

(thinking aloud/voice in my head) If 'those things' are recharged by sunlight, I wonder how will they get the energy to continue transmitting (assuming they have whatever source AND solar panels - for when the fuel runs out and they can't catch any sunlight?)

my dialogue with ChatGPT:

  Voyager 1 and Voyager 2 are powered by \*Radioisotope Thermoelectric Generators (RTGs)\*. These RTGs use the natural decay of \*plutonium-238\* to generate heat, which is then converted into electricity using thermoelectric materials.

  Here’s how the process works:

  1. \*Radioactive Decay\*: Plutonium-238, a radioactive isotope, decays over time, releasing a consistent amount of heat.
  2. \*Thermoelectric Conversion\*: Thermocouples in the RTGs convert this heat directly into electricity.
  3. \*Power Supply\*: This generated electricity powers the instruments, computers, and communication systems on each spacecraft.

  Each year, the power output of the RTGs decreases slightly as the plutonium decays, so the Voyager missions have had to shut down non-essential systems over time to conserve power. Despite this, both Voyager 1 and Voyager 2 have enough energy to continue transmitting until at least the late 2020s, when their power levels will likely drop below the minimum required for communication.

That's the problem, they won't have enough energy to transmit anymore.

The Voyager probes are powered entirely from their RTGs, they have no solar panels nor batteries[1]. So if the power output from the RTGs drops below the level needed to power the transmitter, Voyager can't talk to us anymore. There's no batteries that can be recharged and no solar panels it ever drew power from.

The exciting part from this discovery is the potential to keep talking to Voyager longer than we thought. If the S-band transmitter uses less power and we're still able to detect that signal, we may be able to communicate with the probes with lower RTG outputs than we initially thought. Though at that point, if the radio is the only thing still running and there's no instruments operating, the usefulness is probably pretty low at that point.

[1] https://en.wikipedia.org/wiki/Voyager_1#Power, https://en.wikipedia.org/wiki/Voyager_2#Power

I wonder how long we could make an RTG last today

wiki has the answer, ballpark is around twice as long, and they're using this new design for an upcoming probe

Fundamentally there isn't any change in the underlying physics. You're limited by the half life of the isotope, so you either choose a longer-lived isotope (which actually may be even harder post Cold War as much of the ideal isotopes were byproducts of nuclear weapons manufacturing) or launch a bigger RTG than you need so you have enough power later on in the mission.

yep i think the newer ones use a different fuel that is longer lived, and advances in tech around it make it more viable than it was decades ago

I think the more interesting thing is its suddenly become so much cheaper to put things in orbit, we could simply put a larger satellite with a larger nuclear battery out there.

On such a distance solar panels won't make any difference. Sun looks like just a very bright star from that far.

RTGs are so cool. They're thermocouples in reverse!

Reply on news.ycombinator.com