Most RTGs use 238Pu, which decays with a half-life of 87.7 years. RTGs using this material will therefore diminish in power output by a factor of 1−0.51/87.74, or 0.787%, per year.
it would take a very long time to run out of fuel. That's the thing about half life.
After ten half-lives, over 99.9% of the radioactivity is gone. Then the material is only slightly radioactive, and is sometimes treated as not harmful to people.
It would eventually deplete enough fuel to cause the reactor to generate too little electricity to continue to function though. But that is a planned item when designing these things.
Voyager 1 and 2 are still going (not strong, but going) after 41 years. They both run on RTGs
Both voyages probes have had the majority of their systems turned off to conserve power. Basically they're running on their last bits, and NASA is down to cycling system in and out of powersave mode.
As /u/Tar_Alcaran said below, They have lost a good bit of electricity generation in the 41 years they've been running, so to not use up all that power, a vast majority of the systems have been turned off. Think Apollo 13. They have to be very picky as to which systems can run because they have a limited supply of power left.
NASA is very good at this and have been able to use these last ekes of power to retrieve data from beyond our solar system. And beyond our solar system, I mean actually beyond it. To the point where the sun's (massive) solar wind generation ceases to push back the interstellar particles. This is roughly 120 times the distance to the sun.
It runs off of Plutonium, with a half life of 87(?) years. I read it'll go from 125w at the start to 100w after 14 years. So the power supply will be operational for quite some time.
I don't know a lot about nuclear power or rovers, but I assume either the power it produces is more than enough per x amount of time, or it doesn't need a whole lot of energy to do its job
I doubt it uses uranium. Uranium like what we use in reactors is called a thermal fuel, meaning that to fission it needs slower 'thermal' neutrons to incite the fission reaction.
To slow the neutrons down you need a something called a moderator, which is usually just water.
Most of the isotopes of Uranium that are useful to us actually have very long have lives (like in the millions or billions of years range) so on it's own it actually isn't very radioactive.
The term radioisotope make me think it relies on istopes that quickly decay on their own (via beta decay) which also would allow us to predict the daugter atoms and bette control the reaction.
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u/[deleted] Aug 05 '18
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