First, the nuclear power source is a giant hunk of plutonium. It is expensive to get, dangerous to use, and due to concerns about further refinement, is restricted internationally.
Second, it is toxic inherently — the source is continuously radioactive at a hazardous level to humans, plutonium itself has acute and long-term toxic effects aside from the radioactivity, and if a launch fails, the rtg will disintegrate and poison hundreds of miles (see Kosmos 954, which disintegrated over Canada)
Third, it is HEAVY. They produce 40W per kilogram. Solar panels produce three times that much on Mars, and can be folded compact for launch.
Voyager used an RTG because its planned mission took it far beyond where sunlight can generate power, and it could do so because it had the budget of NASA and plutonium from the Department of Energy.
Solar panels are way cheaper, lighter, easier to procure, easier to launch, and tend not to cause international incidents.
Kosmos-954 didn't poison hundreds of miles, square or otherwise.
They could only find a dozen of radioactive bits, each only dangerous within a very small area around it, and not really leaching anything due to its ceramic nature. Most of the fuel dispersed and became harmless by dilution, probably never even reached the surface.
I wonder if you could do a hybrid approach, where the nuclear device is very small, but able to charge the battery over a longer duration to the point where the solar panels can be repositioned and utilized again.
Lots of missions use radioisotopic heaters, where you don't bother with the thermocouples and just have the material get warm and protect components which are vulnerable to low temperatures.
That's the main reason why spacecraft don't survive a temporary power outage: terrible environmentals.
But at this point, we don't have a lot of Pu-238, which is one of the only decent candidates.
First, the nuclear power source is a giant hunk of plutonium. It is expensive to get, dangerous to use, and due to concerns about further refinement, is restricted internationally.
Second, it is toxic inherently — the source is continuously radioactive at a hazardous level to humans, plutonium itself has acute and long-term toxic effects aside from the radioactivity, and if a launch fails, the rtg will disintegrate and poison hundreds of miles (see Kosmos 954, which disintegrated over Canada)
Third, it is HEAVY. They produce 40W per kilogram. Solar panels produce three times that much on Mars, and can be folded compact for launch.
Voyager used an RTG because its planned mission took it far beyond where sunlight can generate power, and it could do so because it had the budget of NASA and plutonium from the Department of Energy.
Solar panels are way cheaper, lighter, easier to procure, easier to launch, and tend not to cause international incidents.