I assume that when we send a spacecraft to Pluto or beyond we give it a big push at launch and use large planets to propel it into the outer reaches of the solar system. I also assume that they use either solar or nuclear power to charge the batteries that run the communications systems and computers. The further away from the Sun they get the less solar power is available, and decaying nuclear material doesn’t last forever and will eventually become exhausted.
So how long can these long range spacecrafts go based on the power sources they use? 10, 20, 50 years or longer?
These are the widgets that have been furiously decried by various anti-nuke/green entities, partly through misunderstanding (no, we’re not “launching nukes into space”) and partly because there’s a real danger of radioactive contamination if there’s a launch failure. I think some of the long-term craft have had several kilos of uranium oxide or another highly radioactive compound, and there have been measurable releases when satellites revisit earth.
But… ad astra per the smallest oopses we can manage, I believe.
The Voyager probes are expecting to generate sufficient power for operations until about 2025, or roughly 50 years after they were launched. The Pioneer probes only lasted about 30 years.
In theory, radioisotopes can provide essentially unlimited energy if you use something with a long-enough half-life. Use something with a half-life of 4 billion years, and it’ll have power long after the Earth is toast. But the longer the half-life, the less power (as in energy-per-second) you get out of each unit of weight. A tiny satellite strapped to an asteroid of uranium is going to have its own limitations.
How long they last also depends on what performance levels you can tolerate. Like, the Voyagers are still operating, but they’re not getting nearly as much power as they were at their prime, and now are sending back only dribs and drabs of data, for which they have to spend considerably more time charging up their batteries than actually making the transmission, and even those carefully-hoarded transmissions require the full Deep Space Network of dishes to pick up. They’re almost dead, but mostly dead is still slightly alive.
By the way, the thermoelectric generator part of that (minus the radioisotope part) is also known as a Peltier Device. As far as electricity generators go, they suck. They are horribly inefficient. But they can be made small and they have no moving parts.
The way they work is that you make one side hotter than the other, and they generate electricity. They also work in reverse. If you pump electricity into them, one side gets hot and the other side gets cool. They also generate a lot of waste heat (because again, from a thermodynamics point of view, they kinda suck) so if you don’t draw the waste heat away from them they’ll overheat and self destruct.
They used to be so ungodly expensive that only folks like NASA could afford them. Now they are dirt cheap and you see them all over the place. They are the active device in active CPU coolers in your desktop PC and they are also used for those portable picnic coolers that plug into your car’s cigarette lighter plug. They are also used in certain types of cameras and in other sensitive electronic devices where they are used as spot coolers to get rid of the thermal electrical noise in electronics.