At Marshall Space Flight Center in Alabama, engineers have completed the first significant testing of flight scale nuclear reactor hardware since the 1960s. Nuclear propulsion heats propellant using a reactor rather than combustion, achieving much higher exhaust velocities and dramatically better efficiency. For robotic missions to the outer Solar System, nuclear propulsion could enable entirely new categories of science that simply aren't feasible with current technology. "We're doing more than proving a new technology, the test series generated extraordinarily detailed flow response data for a flight like space reactor design” - Jason Turpin from NASA's Space Nuclear Propulsion Office. Source : NASA Testing Advances Space Nuclear Propulsion Capabilities