Abstract:
A launchable device capable of autorotating flight. The device comprises a wing with two airfoils that induce this autorotating flight after launch and ascent.

Description:
BACKGROUND OF THE INVENTION 
     A samara is a simple dry fruit composed of a seed encased in an ovary wall that extends into a flattened wing or wings. The wings of samaras allow them to be carried by the wind when falling from their parent trees or plants. Maple seeds are a single-wing type of samara. 
     In aeronautical terms, a maple seed may be described as an “auto-rotating helicopter.” When a maple seed falls from the tree on which it developed, it picks up speed and starts to rotate around its center of mass. The shape of the wing causes the airflow around the samara (as it drops through the air) to induce a spinning motion. The maple seed is described as “auto-rotating” because its spinning helicopter-like motion arises automatically as it falls through the air. 
     This auto-rotation provides a slow gliding descent in the presence of wind, allowing the maple seed to be carried by the wind away from its parent tree. The same gust of wind that causes the seed to break free of the tree may then carry that seed away. The maple seed has a relatively high “glide ratio” (the distance covered horizontally over distance dropped vertically) in the presence of wind, and therefore stays in the air longer and can travel further away from the parent tree than a typical seed or nut dropped through the air, thus providing a greater chance for the dispersal and propagation of the species. 
     Maple seeds and other samaras have inspired inventors and designers ever since human-powered flight was proven to be possible. Engineers and researchers have explored the nature of maple seed flight in order to understand it and adapt it to various technological applications. For example, recent published research, led by David Lentink, an assistant professor at Wageningen, and Michael H. Dickinson, the Zarem Professor of Bioengineering at Caltech, revealed that, by swirling, maple seeds generate a tornado-like vortex that sits atop the front leading edge of the seed&#39;s wing as it spins slowly to the ground. This leading-edge high-turbulence vortex lowers the air pressure over the upper surface of the maple seed, effectively exerting pressure on the wing in the opposite direction that gravity is pulling it, thereby giving it some lift to counteract gravity&#39;s pull. This vortex provides the maple seed approximately twice the lift generated by non-swirling gliding seeds. See, e.g., http://www.popsci.com/military-aviation-amp-space/article/2009-06/inspired-spinningmaple-seeds-tested-robofly; http://www.youtube.com/watch?v=ce2HUKizMTw (confirmed 19 Dec. 2010). 
     Man-made versions of maple seeds and other samaras have demonstrated very limited use. For example, researchers at the University of Maryland are designing and building robotic fliers that mimic samaras. See, e.g., http://www.avl.umd.edu/projects/projll-robotic-samara.html (confirmed on 19 Dec. 2010). Ned Allen, an aeronautical engineer, is leading a team at Lockheed Martin&#39;s Advanced Technology Lab (ATL) in the development of a simple maple seed-type samara device (the “ATL device”) for use in military and surveillance applications. See, e.g., http://www.atl.lmco.com/news/techfeatures/TODAY0706/TODAY_Nano.pdf (confirmed on 19 Dec. 2010). However, these and other known devices provide simple samara-like auto-rotating helicopters with similar flight characteristics that are literally based on the natural seeds, that is, turbulence-based in their lift creation and utilizing a simple “plate” wing and, in the case of the ATL device, a device that does not have a designated top or bottom surface to its wing. Thus, a need exists for simple, functional, well designed single-wing samara-like auto-rotating devices that utilize more efficient lift-producing airfoil sections in the wing and chassis geometry in order to increase payload, efficiency, predictability, and operational flexibility. 
     BRIEF SUMMARY OF THE INVENTION 
     A launchable auto-rotating device with a single-wing configuration. The device comprises two airfoil shapes when viewed in section along its long and short axes. When launched vertically, the device will travel upwards in a smooth trajectory without rotating (similar to a rocket or ball) and then transition to an auto-rotating flight to glide back to the ground. The structure of the device, particularly the novel arrangement of airfoils and design of the wing, generates lift that slows its descent. In the presence of wind, the device will have a high glide ratio. 
     The device is capable of auto-rotating when dropped through a fluid, though particular embodiments are designed for flight through a gas (and more particularly, through the air). The device comprises a body and a wing that are formed together or coupled together. The body and wing define a junction where they are coupled together, or in the case of a unibody construction, the junction is considered to be the area where the body portion of the piece transitions to the wing portion of the piece. In some embodiments, the device&#39;s center of mass is located within the junction, while in alternative embodiments, the device&#39;s center of mass is located substantially adjacent to the junction. 
     The wing itself comprises a joint end or base (proximal to the body), a tip (distal to the body), a leading edge, and a trailing edge. The leading edge is defined according to the orientation of the wing during auto-rotating flight. 
     One particularly novel (but non-limiting) feature of the device is that the device comprises two airfoils: a first airfoil shape when sectioned along its width, and a second airfoil shape when sectioned along its length. 
     In particular embodiments of the device, the wing further comprises a reinforcing spar. Alternative embodiments also include a protruding hook that provides an anchor point for a launcher, such as a sling-shot. Additionally, some embodiments comprise a payload mounted on or coupled to the body in order to alter the flight characteristics of the device on ascent or descent. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         FIG. 1  is a top view of an exemplary embodiment of the auto-rotating device. 
         FIG. 2  is a side view from the leading edge of the device of  FIG. 1 . 
         FIG. 3  is a side view from the trailing edge of the device of  FIG. 1 . 
         FIG. 4  is an end view from the tip of the wing of the device of  FIG. 1 . 
         FIG. 5  is an end view from the nose of the body of the device of  FIG. 1 . 
         FIG. 6  is a bottom view of the device of  FIG. 1 . 
         FIGS. 7A through 7M  are latitudinal section views (simplified for clarity) of  FIG. 6  showing one of the two airfoil shapes of the device. 
         FIGS. 8A through 8F  are longitudinal section views of  FIG. 1  showing the other of the two airfoil shapes of the device. 
         FIG. 9  is a top view of another exemplary embodiment of the auto-rotating device which has inside it a spar assembly with a protruding hook. 
         FIG. 10  is a side view from the leading edge of the device of  FIG. 9 . 
         FIG. 11  is a bottom view of the device of  FIG. 9 . 
         FIG. 12  is a side view from the trailing edge of the device of  FIG. 1  during a vertical launch of the device. 
         FIG. 13  is a series consisting of a side view from the trailing edge, three perspective views, and another side view from the trailing edge, of the device of  FIG. 1  showing its transition from its position during vertical launch to its position during auto-rotating flight, and also showing the path of the tip of the device. 
         FIG. 14  is a perspective view the device of  FIG. 1  during auto-rotating flight showing the direction of rotation of the tip of the device. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     One exemplary, non-limiting embodiment of the auto-rotating device is depicted in  FIGS. 1 through 8 . The auto-rotating device, generally indicated as  10 , comprises a body  20  coupled to a wing  30  at junction  50 . The wing  30  extends away from the body  20 . The body  20  has a nose  21 . The device&#39;s center of mass  40  is located in the wing  30 , adjacent to the junction  50 . 
     The wing  30  comprises: a joint end  110  coupled to the body  20  at junction  50 ; a tip  134 ; a leading edge  120 ; and a trailing edge  122 . The joint end  110  of wing  30  can also be considered the base  110  of the wing  30 . In this particular embodiment, the trailing edge  122  of the wing  30  further comprises a rounded extension  114 . 
     The nose  21 , the leading edge  120 , the tip  134 , and the trailing edge  122 , together generally define the perimeter of the profile of the device  10  when it is viewed from the top or the bottom, as in  FIGS. 1 and 6 . 
     The device  10  has a top surface  140  and a bottom surface  142 . Specifically, during auto-rotating flight, the bottom surface  142  faces the direction in which gravity is acting (i.e., down, toward the center of the earth) and the top surface  140  faces the opposite direction (i.e., up, toward the sky). The top surface  140  comprises a substantially convex portion of the wing  30 , while the bottom surface  142  comprises a substantially concave portion of the wing  30 . This concavity and convexity is especially pronounced, but not solely present, in the rounded extension area  114 . 
       FIG. 6  shows the underside device  10 . The underside of the device is the side comprising the bottom surface of the wing, while the topside of the device is the side comprising the top surface of the wing.  FIGS. 7A through 7M  are cross-section views showing how the shape of the device  10  changes along its length, from the tip  134  to the nose  21 . Each section view is bounded: on the top by the top surface  140 ; on the left by the leading edge  120 , on the bottom by the bottom surface  142 , and on the right by the trailing edge  122 . 
     The section views in  FIGS. 7A through 7M  show one of the two cambered airfoil shapes manifested in the device  10 . In each section view, a chord line  200  connects the point of maximum curvature of the leading edge  120  to the point of maximum curvature of the trailing edge  122 . 
     The angle of attack of each section shown in  FIGS. 7A through 7M  is the angle between the chord line  200  and the direction in which the leading edge  120  of the device  10  is moving. The section views in  FIGS. 7A through 7M  show that the angle of attack of the airfoil shape of the device  10  increases along the wing  30  from the tip  134  to the joint end  110  of the wing  30  for a portion of the length of the wing  30 . In this particular, illustrated embodiment, the angle of attack is about one degree in the  FIG. 7A  section (adjacent to the tip  134  of wing  30 ) and increases to about one-and-one-half degrees in the  FIG. 7B  section. The increasing angle of attack is about two degrees in the  FIG. 7C  section, further increasing to about two-and-one-half degrees in the  FIG. 7D  section, further increasing to about three degrees in the  FIG. 7E  section, further increasing to about five degrees in the  FIG. 7F  section, and then further increasing to as much as about six degrees in the  FIG. 7G  section. The angle of attack then starts decreasing along the length of wing  30  to about four degrees in the  FIG. 7H  section, then decreasing to about two degrees in the  FIG. 7I  section adjacent to junction  50 . The angle of attack within the body  20  decreases further to about one-half of one degree in the  FIG. 7J  section, and finally further decreases to about zero degrees in the  FIGS. 7K and 7L  sections. 
       FIGS. 8A through 8F  are longitudinal section views showing how the shape of the device  10  changes along its width, from the leading edge  120  to the trailing edge  122 . Each section view is bounded on the left by the top surface  140 , and on the right by the bottom surface  142 . These section views show the other cambered airfoil shape manifested in the device  10 . 
     In some embodiments, the wing  30  and body  20  are of unibody construction (such as being co-molded or formed out of one piece of material together). In other embodiments, the wing  30  and body  20  separate parts that are coupled together. 
       FIGS. 9 through 11  depict another exemplary, non-limiting embodiment of the device, generally indicated as  15 . Like the device  10  of  FIGS. 1 through 6 , the device  15  of  FIGS. 9 through 11  has a body  20 , a nose  21 , a wing  30 , a joint end  110  of the wing  30 , a tip end of the wing  30 , a junction  50 , a leading edge  120 , a trailing edge  122 , a rounded extension  114 , a top surface  140 , a bottom surface  142 , and a center of mass  40 . 
     The chief distinction between the embodiment of  FIGS. 9 through 11  and the embodiment of  FIGS. 1 through 6  is the presence in  FIGS. 9 through 11  of an assembly  160  that comprises payload  161 , a spar  162 , and a hook  150 . The payload  161  allows adjustment of the device&#39;s center of mass  40 , which can alter the flight characteristics of the device during ascent and descent. In particular embodiments, payload  161  is a metal disk or washer, though alternative embodiments employ more sophisticated payloads, such as sensors, radio transceivers, or munitions. The spar  161  is an elongated member of rigid material, such as plastic, wood, or metal that provides reinforcing structural support to the wing  30 . Spar  161  includes a first end coupled to the body  20  and a second end located within the wing  30 . In this particular illustrated embodiment, the spar  162  also includes stiffening ribs  165  that extend from the spar  162  toward the top surface  140  of the device  15 . The spar  130  also comprises the area of the wing  30  between and including the leading edge  120  and the spar line  131 . In this embodiment, the spar  162  also comprises a hook  150  from protruding from the top surface  140  of the body  20  through a hole  163  in the body  20 . This hook provides an anchor point for an assistive device used to launch the device vertically, such as an elastic band or sling-shot. 
       FIG. 12  shows a vertical launch of the device  10 . During the vertical launch phase, the device  10  rotates around the vertical launch spinning axis  300 . This rotation is caused by the second airfoil shape of the device  10  that is shown in  FIGS. 8A through 8F . 
     Vertical launch can be accomplished in several ways. One way is to seat the hook  150  of the device  15  around a piece of elastic material (for example, elastic material configured as a slingshot), then pull the device  15  toward the ground by the tip  134 , and then release the device  15  such that the elastic material launches it skyward. 
       FIG. 13  shows how the device  10  transitions, at the apogee of its vertical launch, from a vertical launch orientation with the nose  21  pointing up and the device  10  rotating around the vertical launch spinning axis  300 , to a horizontal auto-rotating orientation with the top surface  140  pointing up and the device  10  rotating around the auto-rotating flight spinning axis  400 . Thus, the device  10  generates its own lift. The aerodynamic features of the device  10  cause it to shift to the proper orientation for auto-rotating flight once it nears apogee and enters a state of free-fall, and the auto-rotation generates the lift necessary to maintain flight, rather than merely falling back to earth as a static object. 
       FIG. 14  depicts the device  10  during its auto-rotating flight. When in flight, the device  10  exhibits an auto-rotating motion in which the wing  30  and the body  20  rotate around the auto-rotating flight spinning axis  400  at a point that substantially comprises the device&#39;s center of mass  40 . Thus, the mass and placement of a payload  161  can alter the flight characteristics of the device  10  by altering the position of the device&#39;s center of mass  140 .