Quite a few... The issue isn't so much on the nuclear side as it is the size of thermal energy recovery systems. Attempts to miniaturize turbines haven't worke

Quite a few... The issue isn't so much on the nuclear side as it is the size of thermal energy recovery systems. Attempts to miniaturize turbines haven't worked super well, though they have been made since a bottle of fuel has a much greater energy density than most batteries.