Plutonium-238 has been used as a fuel source by NASA for a number of missions, including the 2020 Mars missions with the Perseverance rover, the Apollo flights (1969–1972), the Viking 1 and 2 Mars landers (1976–1982), the 1977 launch of the Voyager 1 and 2 space probes, and the 2006 launch of the New Horizons mission to Pluto and planetary systems
Oh, great! I’ve been using this stuff to control weeds in the garden for years, but if NASA increases the demand for it, I may have to switch to something else.
Any Plutonium isotope should do the job, really.