U.S. government researchers are experimenting with what could be the key to ultra-quiet unmanned aircraft for a wide variety of uses ranging from covert military surveillance and reconnaissance to package deliveries that don't annoy the neighbors.
Researchers at the National Aeronautics and Space Administration (NASA) have developed a scale model of what they call distributed electric propulsion, and now are moving to general aviation-scale prototype aircraft with this ultra-quiet UAV propulsion technology.
The testbed for distributed electric propulsion is called the GL-10 -- short for Greased Lightning -- a 10-motor small unmanned aerial vehicle (UAV) with low-speed 18-inch propellers that developers say is inaudible to human ears when operating at altitudes as low as 100 feet above the ground.
To read more, click here.