DARPA is short for Defense Advanced Research Projects Agency. It is the research and development agency of the U.S. Department of Defense (DoD), whose job it is to develop new technologies for the U.S. military.
Its DSO (Defense Sciences Office) takes new scientific and engineering concepts and develops them into new technologies for use within the DoD.
One of its latest projects is a miniature spy it calls NAV, short for Nano Air Vehicle. The program manager for NAV is Dr. Todd Hylton, a physicist (Ph.D. from Stanford University) and inventor (with nineteen patents).
According to the July 3, 2009 Gizmodo article Pentagon's Robot Hummingbird Christened "Nano Air Vehicle Hylton is attempting to build “… an approximately 10-gram aircraft that can hover for extended periods, can fly at forward speeds up to 10 meters per second, can withstand 2.5-meter-per-second wind gusts."
Hylton has not accomplished that goal, yet, but he is well on his way. Check out the video of the very small experimental hummingbird craft at the Gizmodo web site.
A real hummingbird is a bird in the family Trochilidae. They are some of the smallest species of birds.
Besides being able to fly backwards and hover in mid-air by rapidly flapping their wings, they can also fly at speeds exceeding 34 miles per hour (15 meters per second). Hummingbirds, also, flap their wings at 12 to 90 times per second.
Page two continues.
Actually, DARPA is contracting out much of the developmental work to AeroVironment (AV).
According to the AV website, the company “… develops and produces Unmanned Aircraft Systems and Efficent Electric Energy Technologies that enable our customers to rewrite the rules - of engagement, productivity, efficiency and safety - to their advantage. AV is relentlessly committed to delivering and supporting innovations that help our customers succeed.”
Additional information about the hummingbird spy bird is found on the DSO web site called “Nano Air Vehicle.”
It states, “The Nano Air Vehicle (NAV) Program will develop and demonstrate an extremely small (less than 7.5 cm), ultra-lightweight (less than 10 grams) air vehicle system with the potential to perform indoor and outdoor military missions. The program will explore novel, bio-inspired, conventional and unconventional configurations to provide the warfighter with unprecedented capability for urban mission operations.”
The article comes on to say, “Key objectives include the development of conformal, multifunctional structural hardware and strong, light, aerodynamic lifting surfaces/rotors for efficient flight at low Reynolds number (<15,000).”
The Reynolds number provides the ratio of inertial forces (resistance-of-mass forces, or dynamic pressure) to viscous forces (resistance of a fluid to deformational forces producing shear stress or extensional stress), which is used in the fields of fluid mechanics and heat transfer. Or, it is also stated briefly as the dimensionless ratio of: dynamic pressure / shearing stress.
And, “The program will advance technologies that enable collision avoidance and navigation systems for use in GPS-denied [global positioning system-denied] indoor and outdoor environments and develop efficient methods for hovering flight and deployment or emplacement of sensors."
More information about the hummingbird craft is found on the AV website “UAS Advanced Development: Nano Air Vehicle.”