The probes get their power from the decay of a plutonium isotope. The question is why can't we find applications for this technology on earth, for example to power your house or something?
RTGs are basically just a thermocouple stuck to a chunk of radioactive material, which gets hot. They are dramatically less efficient than a nuclear power plant, so it really doesn't make sense to use them in situations where a nuclear power plant is an option.
That limits them to relatively small things (because your submarine or ship or whatever can have a proper power plant), that can't be connected to a power grid (because you could just have your power plant elsewhere), even periodically (because you could just use batteries), that can't harness more easily available sources of power like the sun or wind, and can carry the shielding necessary to make them safe.
Ultimately, that narrows down their applicability greatly.
https://en.wikipedia.org/wiki/Radioisotope_thermoelectric_ge...
Plutonium is nasty & expensive stuff, however. That puts some pretty severe limitations on its usefulness for domestic purposes.
Yes, for the next 10000 years. Plutonium's half life is annoyingly long.
238Pu is pretty common, because it produces just alpha decay and has a half life of 87 years. Within 1000 years, the main remaining activity is 234U with a half life of 240,000 years: still an alpha emitter but much, much less active.
I recall a discussion on HN about securing radioactive waste sites so that future, possibly illiterate, generations would understand the danger and keep off.
Reading this I'm starting to doubt it's possible. I mean, no snow and steaming ground? Clearly suspicious. And this was the 21st century - these people must have been at least vaguely aware that nuclear power exists.
In space they make sense because as you go far enough away from the sun, solar power is negligible. Since it costs a lot to launch, the cost of the RTG itself isn't such a big deal. And you only have to worry about safety for a little while.
Relying on the thermoelectric effect, they're horribly inefficient. Here on earth we have other options that are more efficient, cost less and is way safer.
Even for space missions, the tradeoff of just using solar panels (which have a ton of problems in space) is often worth it. It's not easy to get an RTG approved for your multi-billion dollar space mission.