By John Keller
U.S. military researchers are kicking off a project to develop an unmanned aerial vehicle (UAV) called the nano air vehicle (NAV), which is roughly the size of a dragonfly, to perform covert surveillance and reconnaissance missions in important and dangerous areas.
Among the most pressing technological challenges of the NAV program are choosing between conventional stationary wings, flapping or vibrating wings, or rotors; how to propel and power the future NAV; choosing the right kinds of avionics, navigation, communications, actuators, and sensors; as well as manufacturing and systems integration approaches.
These key enabling technologies are to enable the NAV to fly as far as one kilometer, hover for as long as one minute, operate reliably in 5-knot wind gusts, fly at speeds as fast as 23 miles per hour, and blend into its operating environment to make the tiny UAV nearly impossible to detect.
The NAV program sponsor, the Defense Advanced Research Project Agency (DARPA) in Arlington, Va., at presstime was imminently set to award the first contracts for the project. Makers of small UAVs such as Aerovironment Inc. of Monrovia, Calif., and Millennial Vision of Canton, Ga., are expected to be among the bidders.
Chief among the aims of the NAV program is the timely collection of detailed intelligence information on the ground in urban areas-particularly from unobtrusive unattended sensors emplaced in locations that are not readily accessible, such as buildings, walls, windows, bridges, caves, tunnels, towers, rocks, and other steep surfaces, DARPA officials say.
It is the placing of these covert imaging, audio, chemical-detecting, and other kinds of sensors that will be the primary mission of the NAV.
This tiny UAV, which DARPA officials say will be no longer than three inches and weigh less than one-third of an ounce, and carry a sensor payload lighter than one-tenth of an ounce, may provide an effective means for precision delivery and emplacement of small, multi-element sensor packages to locations of interest, DARPA officials point out.
The NAV program will push the limits of aerodynamic and power-conversion efficiency, endurance, and maneuverability for very small air vehicle systems, and will explore novel, bio-inspired, conventional, and unconventional configurations, DARPA officials say.
In addition, the program will promote technologies-such as nanotechnology gyros-that will enable collision-avoidance and navigation systems for indoor and outdoor areas where the tiny aircraft cannot acquire signals from the satellite-based Global Positioning System (GPS).
Although DARPA Program Manager Dr. Darryll Pines leaves it up to industry bidders to decide on conventional or nonconventional flight approaches, the agency’s solicitation strongly points to insects and hummingbirds as potential inspiration for the kind of tiny aircraft the NAV program will produce.
Concerning the key technological areas of the NAV program, DARPA expects the designers to use computational aerodynamic modeling and wing design-and-manufacture tools to help them build efficient airfoils for wings or rotors.
Computational models will help designers simulate the performance of efficient lifting surfaces on an extremely small scale. DARPA also wants designers to lay out a clear process for manufacturing these wings or rotors, and integrating them into other subsystems.
When it comes to propulsion and power, DARPA wants a reliable power source with sufficient energy and power to carry the NAV on all of its planned missions. The propulsion system must demonstrate efficient conversion of stored energy to propel the NAV in hover and forward flight.
Efficient transduction actuators will be key to the NAV’s propulsion and power systems, DARPA officials say. Actuators may include servos, integrated smart material elements, or nanoscale or MEMS-engineered actuators to provide power not only to the propulsion system, but also to the communication and navigation subsystems over a range of one kilometer for about 20 minutes.
For the NAV’s navigation, guidance, communications, and flight control, DARPA expects the NAV designer to build gyros, accelerometers, optics, or other kinds of sensors small enough for the tiny aircraft, as well as actuators, electronics, software algorithms, communication systems, and ground-control elements to guide the NAV to and from its target in the presence of 5-knot wind gusts in urban areas.
DARPA officials say they prefer autonomous operation for the NAV, but point out that they would accept line-of-sight and non-line-of-sight teleoperation that achieves minimal on-board processing.
The NAV system also must include all necessary ground line-of-sight command-and-control electronics and software for communicating with the NAV, as well as for launching and retrieving the vehicles.
DARPA officials caution that the NAV project so far is for research and technology demonstration, and may not actually yield a dragonfly-size UAV capable of performing the kinds of missions that DARPA experts envision.
Although the NAV program is expected to yield useful technologies for potential applications to future tiny UAVs, experts in the field admit that a usable UAV the size of an insect most likely is quite a ways off.