A good defense

Current military propulsion programs range from the tried and true that no one thought possible 50 years ago, to those that some might not think possible 50 years from now.

It's been just over 100 years since the first flight of a powered aircraft, and it is also probably just a little over 100 years since someone on the ground had the idea to use the newly proven technology for military purposes. Today, while the skill of the person inside the plane has much to do with winning-and, possibly, avoiding-a battle, lives depend on the reliability of propulsion systems, which are not our grandfathers' propulsion systems.

One example of this involves researchers from NASA's Marshall Space Flight Center and Dryden Flight Research Center and the University of Alabama. Late last year the team developed and demonstrated an aircraft that can fly via propulsive power delivered solely by a ground-based laser. The laser tracks the aircraft in flight and directs its beam at specially designed photovoltaic cells carried onboard. The aircraft can stay in the air as long as the invisible laser light power source is uninterrupted.