Running Out of Plutonium, NASA Turns to Navy Torpedo Tech to Power Spacecraft

NASA needs a new power source to replace its dwindling supply of plutonium-238.

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NASA has a problem. Its go-to energy source for planetary missions is plutonium-283, a radioactive isotope that is used to build nuclear batteries called radioisotope thermoelectric generators (RTGs). RTGs have been used to power space missions since 1969, but the Department of Energy ceased production of plutonium-283 from 1998 to 2013.

Although they are producing more now, and the U.S. does have a small amount stockpiled, there is barely enough plutonium-238 to power the next decade of planned missions to intriguing worlds like Jupiter's moon Europa and Saturn's moon Enceladus. So NASA is looking for a new power source from the best-funded innovators around—the military.

The Navy has been using Stored Chemical Energy Power Systems (SCEPS) since the 1980s. The first SCEPS were used to power torpedoes to track Soviet submarines. They work in a similar manner to epoxy resins: two substances are stored separately and mixed when the resulting chemical reaction is desired. In warheads, the most common reactants are a tank of gaseous sulfur hexafluoride and a solid block of lithium. The chemical reaction of these two substances produces enough heat to create thousands of kilowatts of power, according to Scientific American.

NASA has a slightly different system in mind, one that would draw from a planet's atmospheric gases to create a chemical reaction. The Innovative Advanced Concepts program recently gave $500,000 to Michael Paul, an engineer from Pennsylvania State University, to determine the efficiency of a carbon dioxide-lithium reaction. Paul's ultimate goal is to send a lander equipped with a lithium SCEPS to Venus, using the carbon dioxide in the atmosphere to create a chemical reaction that would drive an electrical generator and power the spacecraft.

This new technique could never replace the efficiency of RTGs for deep-space probes that must operate for years without sufficient solar power, such as the Voyagers and New Horizons. But SCEPS could be used for a number of other applications, such as shorter missions to closer destinations like the moon and Mars, or as a supplemental power source on longer-ranging spacecraft. Ralph McNutt of the Johns Hopkins Applied Physics Laboratory, the guy who wrote the report on the dwindling plutonium-238 supply, called the new technology "exciting stuff."

Source: Scientific American

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