Voyager 1 has gone far enough probing the interstellar spaces outside the Solar System, after its Radioisotope Thermoelectric Generators would completely decay the radioactive material inside, the Voyager would then have no option but to shut down, how is the space-craft going to end up in the future when it will run out of its electric supply. Are there any plans to safely dispose off the probe when it will reach its end like the Cassini spacecraft or will they allow it to bump freely into anything?
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1$\begingroup$ There is no way to generate electricity if the RTGs are down. There are no plans to dispose Voayger into a gas giant. The golden record mounted to Voyager would not make sense if Voyager is disposed. $\endgroup$– UweCommented Aug 15, 2017 at 17:26
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$\begingroup$ Why would we need to 'dispose' of it. Just because it doesn't have power doesn't mean it is garbage. There are relics and audio recordings from Earth that would be a treasure for any intelligent life that may come across it. $\endgroup$– 0tyranny0povertyCommented Aug 19, 2017 at 21:35
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$\begingroup$ but then it can be a big mistake to send our data as treasure to the intelligent life, perhaps they might misuse this treasure and things can go bad. $\endgroup$– Ajinkya NaikCommented Aug 20, 2017 at 15:16
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$\begingroup$ @AjinkyaNaik Any intelligent life with the technology to not only capture one of the Voyagers undamaged, then read the record and understand it will not gain any advantage they did not already have other than they now have our coordinates. If they can do all of the above and have hostile intentions, the record will not help them nor would they need any help. $\endgroup$– honeste_vivereCommented Aug 21, 2017 at 15:19
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$\begingroup$ @honeste_vivere makes sense though. $\endgroup$– Ajinkya NaikCommented Aug 21, 2017 at 16:20
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NASA currently expects that the RTG on Voyager 2 will no longer provide enough power to run a single instrument by 2025. Voyager 1 might last a bit longer. That will be the end of the mission.
Both Voyagers are in a very empty part of space. There is nowhere to crash into, and not enough fuel to change the trajectory noticeably.
Both Voyagers will pass stars at a distance of 1.6-1.7 light years in 40,000 years, and calculations have been made to much longer timescales with no collisions predicted. I don't know specifically if this was deliberate choice, or if it was a happy coincidence of the trajectories chosen for the planetary encounters, but that seems to be 'safe disposal' to me.
Should the Voyagers run into anything, the RTGs were built to survive reentry on Earth, they're pretty robust.
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$\begingroup$ Of course if they hit something a half million years or more from today, then the majority of the RTG material left will be non-radioactive through decay. $\endgroup$ Commented Aug 15, 2017 at 19:25
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1$\begingroup$ No. Pu-238 quickly decays to U-234, which has a half-life of 245,000 years. Then you get various shorter-lived isotopes which end up with lead. So it takes a very long time for the RTG to go inert. $\endgroup$– HobbesCommented Aug 15, 2017 at 20:26
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$\begingroup$ True for a half million, but most of it will be gone, and by those time scales it could be millions of years, at which point my original comment stands $\endgroup$ Commented Aug 15, 2017 at 20:31
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1$\begingroup$ In seven half-lifes, there is only 1/128 of the original U-234, so 1.715 million years will reduce it to less than one percent and ten half-lifes (2.45 million years) to less than 1/1000. $\endgroup$– UweCommented Aug 16, 2017 at 16:02
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3$\begingroup$ The shorter half-life the more radioactive the isotope (number of decays per second is higher). That means the radioactivity of U-234 will be minuscule comparing to radioactivity of the plutonium - about 2800 times weaker. (these "faster-decaying" products will icrease it somewhat, but their amount is limited by rate of decay of uranium, so it's still a pretty safe level.) $\endgroup$– SF.Commented Aug 17, 2017 at 0:46