McNutt told the AIAA symposium the situation isn't getting better fast, even though Congress has allocated some funds for NASA to restart production. NASA has been forced to “go it alone,” without funding help from the Energy Department or other agencies, as it is behind the pace to get things started again by 5-7 years. Once production restarts, the U.S. space agency believes it can produce “a couple of kilos in a year,” but that isn't going to cover the demand laid out in the National Research Council's decadal survey of exploration priorities: Uranus, the methane lakes of Titan and the water geysers of Enceladus. The shortfall would be compounded if human exploration begins drawing on the supply for long-duration missions beyond solar-power range.

“It is the sine qua non for doing solar system exploration,” McNutt says of Pu-238, a scarcer resource than money, even in these cash-strapped times.