DARPA is an unending source of high-tech, secret projects, and it seems to have focused quite a lot in recent years on those that have to do with aviation. The latest such effort we got wind of: the XRQ-73 SHEPARD.
 
SHEPARD is, of course, an acronym, and it stands for Series Hybrid Electric Propulsion AiRcraft Demonstration. It's a program meant to deliver in the hands of the U.S. military an uncrewed aircraft capable of flying through the sky as quietly as possible, and it builds on another initiative, one called Great Horned Owl (GHO) and overseen by the Air Force Research Laboratory (AFRL).

GHO started out in a bid to develop an intelligence, surveillance, and reconnaissance (ISR) drone capable of sneaking close to enemy lines without said enemy being able to detect it. In a nutshell that would mean a solution that has a very low acoustic signature, but is not battery-powered, because those drones have serious limitations when it comes to range and payload.

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