Multi-Hundred-Watt radioisotope thermoelectric generator

technology

The power source that has kept both Voyagers alive for forty-nine years. Each spacecraft carries three Multi-Hundred-Watt units on a boom; each unit holds spheres of plutonium-238 dioxide whose radioactive decay produces heat, and a bank of silicon-germanium thermocouples turns part of that heat directly into electricity with no moving parts. Together they supplied about 470 watts at launch. Output has fallen ever since, by roughly four watts a year, for two compounding reasons: the plutonium decays with an 87.7-year half-life, and the thermocouples themselves degrade. That decline is the whole operational story of the mission after 1989. It cannot be repaired, it cannot be paused, and it is predictable to the watt — which is why the flight team can plan instrument shutdowns years ahead and argue about them in terms of watts rather than science priorities alone. Not a place.

A technology is not a place. Drawing it on a map would assert something about the world that no stored fact supports.