I have been fascinated by radioisotope thermal generators (RTGs), aka nuclear batteries, ever since I saw a display at the Maryland Science Center in Baltimore’s Inner Harbor sometime in the early 1990s.

In that energy exhibit, there was a tiny RTG that was designed to power a cardiac pacemaker. What impressed me the most was the fact that the battery could produce continuous power for an incredible period of time – after 10 years it would still be producing 89% of the current that it produced when new. After 87 years of continuous output, the battery would still produce 50% of the current of a new battery.

These long-life nuclear batteries are not only energy dense, but they are also power dense – the current output per unit mass is comparable to that of a lithium ion battery, but they last far longer. I can just imagine what it would be like to have a laptop whose battery never needed to be recharged.

Similar technology is what enabled the Voyager spacecraft to head out into the solar system to take pictures and send them back to Earth. Even in a place where the sun is a distant dot that produces virtually no power and where journeys are measured in decades, engineers had a reliable power source available – the heat produced by radioactive decay of a relatively long lived isotope like plutonium 238.
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