Single Rotor Blade Helicopter Based on Maple Seed (Samara)
A Samara is a winged fruit from a wide variety of trees that use this method of spreading seed. Notably the elm, ash, and maple (likely the one most people are familiar with) use this method of spreading fruit (and the seed contained within) farther from the tree.
A samara then is a winged fruit which autorotates to the ground when the fruit falls from the tree. Note the image below of a collection of samara on a maple tree.
The University of Maryland has been conduction experiments with this natural design in the form of a single rotor miniature helicopter that can autorotate to the ground should it lose power. These designs incorporate a number of motive engines to power the craft, but all use the same basic maple samara design or a single rotor to provide both lift and a soft landing.
University of Maryland Studies
Students at the University of Maryland began attaching motive power sources to a single wing shaped much like the samara. This led to material science experiments, partial computer control, and robotics for autonomous flight.
The main thrust of the design is for development of small spying devices which will autorotate to the ground when they run out of power. This will make the devices highly reusable.
The natural autorotate abilities of this design mean that the device can also be airdropped and autorotate to a particular altitude before being powered up and put to use. Of course, once any surveillance has been carried out the device can be powered down again and allowed to "float" to the ground where it can be recovered and reused.
Samara Autorotate Demonstration
Three and a Half Years of Research
Though Lockheed/Martin had a similar design, U of M, has extended what was learned from that project far into the realm of useful design.
Perhaps the most attractive thing about these autonomous samara are their cost. At about five hundred ($500) each they are considerably cheaper than similar designs from some years ago. Best of all that five hundred dollar price tag is for a development model; not a far more cheaply mass-produced version.
Of course one of the problems with such a design is controlled lift and controlled steering.
Apparently the University of Maryland graduate students solved both these problems (I suspect with a similar approach to both), but aren't explaining exactly how they did it. Two patents have been applied for. The new design also incorporates a structure that the wing is attached to that provides a platform for power (battery) and a propeller.
The designs include open propeller and ducted fans.
Clearly there is some sort of microprocessor control that tilts the rotor at opportune times to cause the device to move in any direction the operator desires. There are even models that are completely autonomous.
The Samara device was designed, built and tested by the graduate students of the University of Maryland Aerospace Engineering Autonomous Vehicle Laboratory and Alfred Gessow Rotorcraft Center.