Military Plans Hummingbird-Sized Spies in the Sky

Soldiers fighting future battles in crowded urban areas will be able to launch hummingbird-sized unmanned nano aerial vehicles —  or NAVs – capable of carrying sophisticated sensors and flying through open windows in buildings to report back on enemy positions.

A new project partly funded by the Defense Advanced Research Projects Agency (DARPA) called the Nano Aerial Vehicle (NAV) program aims to develop an extremely small, ultra-lightweight aerial vehicle for urban military missions that can fly both indoors and outdoors and that is capable of climbing and descending vertically as well as flying sideways left and right.

DARPA says the NAV program pushes the limits of aerodynamic and power conversion efficiency, endurance and maneuverability for very small air vehicle systems.

The design the agency green lighted for further development actually will look and fly much like a hummingbird. The winning concept, developed by AeroVironment, is called Nano Scout (Nano Sensor Covert Observer in Urban Terrain). It is a remote-controlled, battery powered NAV with two flapping wings that weighs about two grams (about as heavy as two nickels) and is just slightly longer than three inches.

Lots of competition

The Scout is designed to fly forward at speeds of up to 20 mph, slow down to one mph for precision navigation inside buildings, withstand five mph wind gusts, operate inside buildings and have a range of over one-half mile.

The Nano Scout was selected over competing concepts submitted by Lockheed Martin, MicroPropulsion Inc., and Draper Laboratory at the end of the program’s first phase last year.

An early prototype tested by the company has already reached a technical milestone by achieving a hovering flight equal to that of a two-wing flapping wing aircraft while carrying its own energy source and using only the flapping wings for propulsion. A working prototype, scheduled for demonstration to DARPA when the second phase of the NAV program ends this summer, will have a flight endurance of 11 to 20 minutes.

But DARPA and AeroVironment aren’t the only players with a wing in the NAV game.  Though its monocoptor design that is shaped like a maple leaf was passed over for the second phase of the DARPA program, Lockheed Martin Skunk Works’ Advanced Development Programs is continuing its exploration of NAVs on its own dime with the Samurai program.

The company has built two larger mono-wing vehicles as part of the program, a 30-inch flyer and a 12-inch version that is small enough to fit into a backpack and fly through an open window to enter a building.  The Samurai design, says Kingsley Fregene, principal investigator for the program, is inherently stable and has few moving parts, which makes it a robust, aerodynamically clean airframe. Unlike more conventional designs, the entire aircraft rotates.

Nano-sized pack mules

Most of the excitement has been about the platform and getting devices in the air and keeping them there.  But the payoff for NAVs is in the payload.  "A lot of people can build aircraft that fly," Neil Adams told TechNewsDaily. "Making them work is the critical element."

Adams is director of tactical systems programs for Draper Laboratory, one of the participants in the first round of DARPA’s NAV program.

Draper is a systems integrator that develops the mission management, vehicle management and communications and ground control systems that make NAVs smart. "What we do is the 'missionization' of these vehicles," Adams said. In creating the payload for one of these tiny devices, he said, "weight is always the issue. The size of payloads has to be designed with plenty of margin."

Because the normal operating environment for NAVS is congested urban areas with little or no GPS signal availability, navigation is also a critical element, said Adam. Much of Draper’s work focuses on vision-based sensors and systems. "If you don’t have GPS or you have only intermittent GPS, most of these things will fall out of the sky in a few seconds," he said.

The enemies of success in the NAV world are size, weight and power (SWaP), said Sean Humbert, a professor in the Aerospace Engineering department at the University of Maryland who specializes in Nano Air Vehicles.

Insect inspiration

SWaP places great limitations on the intelligence that can be built into NAVs to let them operate autonomously. Researchers are looking at insects and their nerve physiology for clues about how to design better nervous systems for NAVs. "Little bugs don’t carry around a Pentium processor," Humbert said. And yet they’re remarkably good at doing what they need to do. Perhaps, he said, if we learn what’s going on in their brains we can follow their lead.

Humbert’s department is studying bio-inspired microsystem technologies as the principal member of the U.S. Army Research Laboratory’s Micro Autonomous Science and Technology (MAST) Collaborative Technology Alliance (CTA) Center.

"A lot of structures in insects are multifunctional," he said. "Biologically, they’re multitasking."

The research is still in its early stages. "A lot of seminal research needs to be done," Adams said, adding that the missionization of NAVs, though, is not that far away.

"Within 10 to 15 years, autonomous microsystems will be on the battlefield."