Voyager 1 has traveled through space for over 46 years using nuclear batteries fueled by Plutonium-238.

Launched by NASA on September 5, 1977, Voyager 1 is equipped with three Multi-Hundred Watt Radioisotope Thermoelectric Generators (MHW-RTGs). These generators utilize the natural radioactive decay of Plutonium-238, which has a half-life of 87.7 years. As the plutonium decays, it releases significant thermal energy that is captured and converted into electricity.The conversion process relies on the Seebeck effect, where a temperature difference between two different electrical conductors produces a voltage. Thermocouples made of silicon-germanium alloys are used to facilitate this transition from heat to power. At launch, the RTGs provided approximately 470 watts of power, but this output decreases by about 4 watts every year due to fuel decay and thermocouple degradation.As of 2024, Voyager 1 is over 15 billion miles away from Earth, making it the most distant human-made object in existence. To conserve the remaining power, NASA engineers have systematically turned off non-essential heaters and scientific instruments over the last two decades. This careful management allows the spacecraft to continue transmitting data from interstellar space, far beyond the reach of the Sun's solar wind.The longevity of the MHW-RTGs has exceeded all original expectations for the mission, which was initially only intended to last five years. Current projections suggest that Voyager 1 will have enough power to operate at least one science instrument until 2025. After that, the spacecraft will continue its silent journey through the Milky Way, carrying the Golden Record as a message to any future civilizations.