It's already used (minus the diamond casing), e.g. in the Curiosity mars rover, or the Voyager probes https://en.wikipedia.org/wiki/Curiosity_(rover)#Specifica

It's already used (minus the diamond casing), e.g. in the Curiosity mars rover, or the Voyager probes https://en.wikipedia.org/wiki/Curiosity_(rover)#Specifications https://en.wikipedia.org/wiki/Curiosity_(rover)#Specificatio... https://en.wikipedia.org/wiki/Radioisotope_thermoelectric_generator https://en.wikipedia.org/wiki/Radioisotope_thermoelectric_ge...