Remote-controlled drones are already a controversial part of US military strategy, but an experimental Navy aircraft that pilots itself could make the ethical issues they raise seem downright pedestrian. The Northrop Grumman X-47B is a robotic plane designed to be able to refuel, make difficult takeoffs and landings, and follow a flight plan without outside direction. After making its first flight last February, the plane has undergone more testing and development — it's set to make its first landing on an aircraft carrier in 2013, and to demonstrate refueling by 2014.

As astonishing as a self-flying plane is, however, the idea of a self-directed, weaponized plane doesn't sit will with many people. Although the Navy says it has no plans to arm the X-47B, and deployment could be over a decade away, the plane has a weapons bay capable of carrying 4,500 pounds, and further iterations would very likely end up being used in combat. Robotics expert Noel Sharky says that it would be extremely difficult to determine a clear chain of accountability with a robotic weapon, and the International Committee of the Red Cross is already looking into how autonomous weapons might be able to comply with humanitarian law. For now, the rest of us will be sticking with our distinctly non-weaponized self-driving cars.