Abstract:
A compact, aerodynamic wing assembly constructed and arranged so as to withstand a force due to acceleration in at least one direction includes at least two wing segments, each of the wing segments having a span-wise axis, and a airfoil cross section normal to the span axis. The wing segments are preferably disposed mutually adjacent and end to end. For each pair of wing segments, the wing further includes a pivot assembly fixedly attached to the wing segments at an end of each of the wing segments along the span-wise axis. The pivot assembly forms an articulation axis for relative movement between each the pair of wing segments, such that the wing assembly converts, upon a predetermined stimulus, from a stowed configuration characterized by nested wing segments, to a deployed configuration characterized by a substantially uninterrupted aerodynamic surface. The wing assembly is preferably constructed and arranged to withstand forces due to acceleration in at least two directions, including 15,000 g&#39;s forward and 4,000 g&#39;s rebound accelerations. The invention further comprises a flying structure constructed and arranged so as to withstand an acceleration force directed along a main axis. The flying structure includes a body disposed about the main axis, and at least one wing assembly pivotally mounted to the body. The wing assembly is constructed and arranged so as to convert, upon a predetermined stimulus, from a stowed configuration characterized by nested wing segments, to a deployed configuration characterized by a substantially uninterrupted aerodynamic surface.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Not Applicable 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH 
     Not Applicable 
     REFERENCE TO MICROFICHE APPENDIX 
     Not Applicable 
     BACKGROUND OF THE INVENTION 
     The present invention relates to flying structures that derive lift from associated aerodynamic surfaces, and more particularly, to such flying structures constructed and arranged so as to be deployed from a compact, stowed payload state, and withstand ballistic g-forces while in such a stowed payload state. 
     Reconnaissance and surveillance are universally recognized as key components of typical investigatory operations; this is especially true for military operations. Such observation tools may be used to identify and evaluate potential targets, provide targeting information to weapons platforms, and battle damage assessment following a sortie. The three general classes of observation tools currently used for reconnaissance/surveillance missions in military operation, as shown in FIG. 1, include 1) satellites, 2) high altitude/long endurance systems (e.g., JSTARS, Tier II+, U-2, etc.), and 3) tactical UAVs (e.g., Outrider, Pioneer, Hunter II, etc.). Satellites provide global coverage and high resolution information, but are typically the most expensive options and exhibit the longest response time. High altitude/long endurance systems are typically less expensive and exhibit faster response times than satellites, but provide reduce coverage (i.e., theater level rather than global). Tactical UAVs are the least expensive class of observation tools and provide the fastest response times, but provide only battlefield coverage. The cost of the observation tool is directly related to the level of command to which the tool is available. In many scenarios, it is advantageous to make an observation tool available to the lowest level of command possible. Making such tools available to lower levels of command increases battle efficiency by reducing the amount of time necessary make targeting decisions. Thus, a disadvantage to such prior art observation tools is that they are not directly available to the levels of command that could most efficiently utilize them. 
     Another disadvantage to such prior art observation tools is the risk involved in transporting the observation tools to a location that will provide the most valuable observation information. Because such tools often travel at sub-sonic speeds, there is a significant probability that the tool will be detected, intercepted and/or destroyed by hostile forces. One possible solution to such risk is to ballistically launch the observation tool to the desired location. However, prior art observation tools are not typically constructed to survive the high g-forces that develop during a ballistic launch. Observation tools that include aerodynamic surfaces for sustained flight are particularly vulnerable, due to the inherently fragile nature of such surfaces. 
     It is an object of the present invention to substantially overcome the above-identified disadvantages and drawbacks of the prior art. 
     SUMMARY OF THE INVENTION 
     The foregoing and other objects are achieved by the invention which in one aspect comprises a multi-state, aerodynamic wing assembly constructed and arranged to have a first state which is compact and adapted to withstand a substantial force due to acceleration in at least one direction, and a second state adapted for flying. The wing includes at least two airfoil sections, each of the airfoil sections having a span-wise axis, and a airfoil cross section normal to the span axis. The airfoil sections are preferably disposed mutually adjacent and end to end. The wing further includes a pivot assembly fixedly attached to each pair of adjacent ones of the airfoil sections at an end of each of the adjacent airfoil sections along said span-wise axis. The pivot assembly forms an articulation axis for angular translation of each the pair of airfoil sections, such that the wing assembly converts, upon a predetermined stimulus, from a stowed configuration characterized by nested airfoil sections, to a deployed configuration characterized by a substantially uninterrupted aerodynamic surface. 
     In another embodiment of the invention, the pivot assembly includes at least one hinge assembly. 
     In another embodiment of the invention, the pivot assembly includes at least one flex joint assembly. 
     In another embodiment of the invention, the pivot assembly further includes at least one actuator for forcing each pair of the airfoil sections to translate with respect to one another about the articulation axis, such that the wing assembly converts from the stowed configuration to the deployed configuration. 
     In another embodiment of the invention, the actuator includes a spring assembly; in particular, the spring assembly may further include a torsion spring assembly. 
     In another embodiment of the invention, the relative movement between each the pair of airfoil sections includes approximately 180 degrees of relative movement about the articulation axis, from the stowed configuration to the deployed configuration. 
     In another embodiment of the invention, at least one aerodynamic force converts the wing assembly from a stowed configuration to a deployed configuration. 
     In another embodiment, a combination of at least one aerodynamic force and at least one torsion spring converts the wing assembly from a stowed configuration to a deployed configuration. 
     In another embodiment of the invention, the wing assembly further includes at least one locking mechanism for locking the wing segments in the deployed configuration. 
     In another embodiment of the invention, the at least two airfoil sections includes N airfoil sections, joined by N−1 pivot assemblies and forming N−1 articulation axes, where N is an integer greater than or equal to two. 
     In another embodiment of the invention, the N airfoil sections includes six airfoil sections, joined by five pivot assemblies and forming five airfoil sections. 
     In another embodiment of the invention, the N−1 articulation axes are substantially parallel. 
     In another embodiment of the invention, the N−1 articulation axes are non-parallel, such that the deployed configuration includes a spiral wing. 
     In another embodiment of the invention, the pivot assembly further includes nesting supports, constructed and arranged such that predetermined pairs of the nesting supports are adjacent while in the stowed configuration, so as to provide structural support along the span-wise axis. 
     In another embodiment of the invention, the at least one direction of acceleration includes the span-wise axis. 
     In another embodiment of the invention, each the airfoil cross section includes a modified T16 airfoil section. 
     In another embodiment of the invention, each of the airfoil sections includes 7075 aluminum. 
     In another embodiment of the invention, each of the airfoil sections and corresponding pivot assemblies are machined from a unitary body of 7075 aluminum. 
     In another embodiment of the invention, each of the airfoil sections includes a composite material. 
     In another embodiment of the invention, each of the airfoil sections is constructed via a fabrication technique selected from the group consisting of molding, injection molding, casting, stamping and extrusion. 
     In another embodiment of the invention, the wing assembly is constructed and arranged so as to withstand at least one acceleration force in at least one direction. 
     In another embodiment of the invention, the wing assembly is constructed and arranged so as to withstand a 15,000 g forward acceleration force, and a 4,000 g rebound acceleration force. 
     In another aspect, the invention comprises a flying structure constructed and arranged so as to withstand an acceleration force directed along a main axis. The flying structure includes a body disposed about the main axis, and at least one wing assembly pivotally mounted to the body. The wing assembly is constructed and arranged so as to convert, upon a predetermined stimulus, from a stowed configuration characterized by nested airfoil sections, to a deployed configuration characterized by a substantially uninterrupted aerodynamic surface. 
     Another embodiment of the invention further includes a propulsion module disposed along the main axis adjacent to a first end of the flying structure body. 
     In another embodiment of the invention, the propulsion module further includes a propeller assembly, an engine assembly rotatably coupled to the propeller assembly, and a cone assembly for covering the engine assembly. 
     In another embodiment of the invention, the propeller assembly is constructed and arranged so as to convert, upon a predetermined stimulus, from a stowed configuration characterized by a retracted propeller, to a deployed configuration characterized by an extended propeller operative to provide thrust along the main axis upon rotation. 
     Another embodiment of the invention, further includes a tail module having at least one aerodynamic surface. 
     In another embodiment of the invention, the at least one aerodynamic surface is constructed and arranged so as to convert, upon a predetermined stimulus, from a stowed configuration characterized by a retracted aerodynamic surface, to a deployed configuration characterized by an extended aerodynamic surface. 
     In yet another aspect, the invention comprises a wing assembly having at least two airfoil sections, each of which extend along a span axis and between end portions thereof. Each of the airfoil sections has an airfoil cross-section normal to the span axis, and the airfoil sections are serially disposed end portion to end portion, whereby end portions of adjacent airfoil sections are mutually adjacent. The wing assembly further includes at least one pivot assembly. Each of the pivot assemblies couples the mutually adjacent end portions of a pair of the adjacent airfoil sections and defines an articulation axis about which the pair of adjacent airfoil sections are rotatable. The wing assembly is configurable in a stowed configuration state wherein the series of airfoil sections are nested with the span axes of the airfoil sections being substantially parallel. The wing assembly is further configurable in a deployed state wherein the series of airfoil sections are arranged to form a substantially uninterrupted aerodynamic surface. 
     In another embodiment, the span axes are substantially co-linear. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     The foregoing and other objects of this invention, the various features thereof, as well as the invention itself, may be more fully understood from the following description, when read together with the accompanying drawings in which: 
     FIG. 1 shows a perspective view of three general classes of observation tools currently used for reconnaissance/surveillance missions; 
     FIG. 2A shows a perspective view of one preferred embodiment of a high-g, compact folding wing assembly; 
     FIG. 2B shows an exploded view of the folding wing assembly of FIG. 2A; 
     FIG. 3 lists, in tabular form, exemplary dimensions for the preferred embodiment of the wing segments of FIG. 2A; 
     FIG. 4A illustrates a top view of a wing having three wing segments with non-parallel root edges and tip edges; 
     FIG. 4B illustrates a leading edge view of a wing having three wing segments with non-parallel root edges and tip edges; 
     FIG. 4C illustrates a root end view of a wing having three wing segments with non-parallel root edges and tip edges; 
     FIG. 5 shows the results of a two dimensional viscous analysis of a modified T16 airfoil section; 
     FIG. 6 shows the folding wing of FIG. 2A used in conjunction with a flying structure; 
     FIG. 7 shows an exploded view of the propulsion module from the flying structure of FIG. 6; 
     FIG. 8A shows a top view of the wing module from the flying structure of FIG. 6; 
     FIG. 8B shows a front perspective view of the wing arm, the back wing support and the root wing segment of a wing assembly from the wing module of FIG. 8A; 
     FIG. 8C shows a rear perspective view of the wing arm, the back wing support and the root wing segment of a wing assembly from the wing module of FIG. 8A; and 
     FIG. 9 illustrates an exploded view of the tail module from the flying structure of FIG.  8 A. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 2A shows a perspective view of one preferred embodiment of a high-g, compact folding wing assembly  100  according to the present invention, and FIG. 2B shows an exploded view of the folding wing assembly  100  of FIG.  2 A. In a preferred embodiment, the folding wing  100  includes six wing segments (also referred to as airfoil sections)  102   a  through  102   f . The root wing segment  102   a  is the largest segment and is the segment that attaches to the body of an associated flying structure. The tip wing segment  102   f  is the smallest segment and forms the distal end of the wing  100 . Exemplary dimensions for the preferred embodiment of the wing segments are listed in tabular form in FIG.  3 . Each root chord length describes the linear distance from the leading edge  104  to the trailing edge  106  of the corresponding wing segment, at the root of that wing segment (i.e., the end of the wing segment closest to the wing arm  108 ). Each tip chord length describes the linear distance from the leading edge  104  to the trailing edge  106  of the corresponding wing segment, at the tip of that wing segment (i.e., the end of the wing segment closest to the wing tip  110 ). The wing arm  108  attaches to the root of the root wing segment  102   a , and provides a support structure for attaching the wing  100  to the body of an associated flying structure. In a preferred embodiment, the root edges and tip edges of all wing segments are all parallel and normal to the span-wise axis  109 , although in other embodiments non-parallel root edges and tip edges may be used to provide alternate wing shapes. For example, FIGS. 4A (top view),  4 B (leading edge view) and  4 C (root end view) illustrate a wing  200  having three wing segments  202   a  through  202   c  with non-parallel root edges and tip edges. This particular configuration gives rise to a spiral wing shape (i.e., a twist in the wing via sweeping of the edges), although other wing shapes may be formed by implementing different relative orientations of the root/tip edges. 
     A wing segment pivot assembly is included at the junction of each pair of wing segments. In the exemplary embodiment shown in FIGS. 2A and 2B, each wing segment pivot assembly is implemented by a pair of hinges. Other embodiments of the wing  100  may employ other pivot assembly means known to those in the art. For example, one embodiment may utilize a flex joint between each pair of wing segments. In the embodiment of FIGS. 2A and 2B, hinges  112  and  114  join wing segments  102   a  and  102   b , hinges  116  and  118  join wing segments  102   b  and  102   c , hinges  120  and  122  join wing segments  102   c  and  102   d , hinges  124  and  126  join wing segments  102   d  and  102   e , and hinges  128  and  130  join wing segments  102   e  and  102   f . As is more clearly described in FIG. 2B, each hinge includes an outside hinge block and an inside hinge block. Each pair of hinges includes a hinge pin and a torsion spring. In particular, hinge  112  includes outside hinge block  132  and inside hinge block  134 . Hinge  114  includes outside hinge block  136  and inside hinge block  138 . Torsion spring  140  is situated between hinge  112  and  114 , and hinge pin  142  passes through hinge blocks  132  and  134  (to form hinge  112 ), through torsion spring  140 , and through hinge blocks  136  and  138  (to form hinge  114 ). 
     Hinge  116  includes outside hinge block  144  and inside hinge block  146 . Hinge  118  includes outside hinge block  148  and inside hinge block  150 . Torsion spring  152  is situated between hinge  116  and  118 , and hinge pin  154  passes through hinge blocks  144  and  146  (to form hinge  116 ), through torsion spring  152 , and through hinge blocks  148  and  150  (to form hinge  118 ). 
     Hinge  120  includes outside hinge block  156  and inside hinge block  158 . Hinge  122  includes outside hinge block  160  and inside hinge block  162 . Torsion spring  164  is situated between hinge  120  and  122 , and hinge pin  166  passes through hinge blocks  156  and  158  (to form hinge  120 ), through torsion spring  164 , and through hinge blocks  160  and  162  (to form hinge  122 ). 
     Hinge  124  includes outside hinge block  168  and inside hinge block  170 . Hinge  126  includes outside hinge block  172  and inside hinge block  174 . Torsion spring  176  is situated between hinge  124  and  126 , and hinge pin  178  passes through hinge blocks  168  and  170  (to form hinge  124 ), through torsion spring  176 , and through hinge blocks  172  and  174  (to form hinge  126 ). 
     Hinge  128  includes outside hinge block  180  and inside hinge block  182 . Hinge  130  includes outside hinge block  184  and inside hinge block  186 . Torsion spring  188  is situated between hinge  128  and  130 , and hinge pin  190  passes through hinge blocks  180  and  182  (to form hinge  128 ), through torsion spring  188 , and through hinge blocks  184  and  186  (to form hinge  130 ). 
     The hinges, hinge pins and torsion springs are all located on the wing intrados. The hinges allow approximately 180 degrees of rotation between the corresponding two wing segments about an articulation axis preferably collinear with the hinge pins. The motion that the hinge allows ranges from a deployed position to a stowed position, and vice versa. In the deployed position, the airfoil cross sections of the two segments are substantially parallel and are oriented in the same direction, such that the segments&#39; extrados form a substantially continuous surface. In the stowed position, the airfoil cross sections are substantially parallel but are oriented in the opposite direction, such that the segments&#39; intrados face one another. The embodiment of the wing  100  illustrated by FIGS. 2A and 2B employs the torsion springs  140  as actuators for converting the wing  100  from the stowed configuration to the deployed configuration. The torsion springs  140  are constructed and arranged so as to provide a torque sufficient to cause each pair of adjacent wing segments to translate with respect to one another about said articulation axis, from the stowed configuration to the deployed configuration. This torque is sufficient to maintain the wing  100  in the deployed configuration. Alternate embodiments of the invention may include other actuating mechanisms known to those in the art for converting the wing  100  from the stowed configuration to the deployed configuration, such as hydraulic actuators, pneumatic actuators, and electro-mechanical actuators, among others. Other embodiments of the present invention may not include actuators for deploying the wing, and may thus rely upon external forces to convert the wing from the stowed configuration to the deployed configuration, such as aerodynamic forces, gravity, centrifugal forces, etc. For example, one such embodiment may insert a partially deployed wing into the external air flow, and rely upon the resultant aerodynamic forces on the wing to complete the deployment and thereafter maintain the wing in the deployed configuration. Other embodiments of the invention may rely upon combinations of the various forces described herein to deploy the wing. For example, one embodiment of the invention may incorporate smaller torsion springs  140  that alone may not effect wing deployment, but rely on aerodynamic forces and/or gravity to complete deployment. An advantage to such an embodiment would be a reduction in the size of the torsion springs  140  necessary for wing deployment. Alternate embodiments of the invention may include locking mechanisms for locking the wing segments in the deployed configuration. Such locking mechanisms may be advantageous in that they also may facilitate a reduction in the size of the torsion springs (or other actuating mechanisms) necessary for deployment and maintaining the deployed configuration. 
     In a preferred embodiment, the airfoil cross section of the wing  100  is a modified version of the T16 airfoil (a typical airfoil utilized for endurance-type aircraft), although other embodiments may employ similar airfoils known to those in the art. In a preferred embodiment, the original T16 airfoil is modified by thickening the trailing edge of the airfoil to prevent buckling under acceleration along the span-wise axis  109 . The results of a two dimensional viscous analysis of the modified T16 airfoil section are shown in FIG.  5 . This analysis provides a graphical illustration of the pressure distributions on the modified T-16 airfoil for various angles of attack, in the flight regime expected for the wing  100 . The Reynolds number used for this illustration is 158,000, derived from the mean wing average chord of 0.0647 m, a cruise flight velocity of 38.6 m/s, and a kinematic viscosity value corresponding to an altitude of 1000 m. 
     In a preferred embodiment of the invention, each individual wing segment  102   a  through  102   f , including the hinge blocks, is machined from a separate body of aerospace grade aluminum (i.e., 7075 aluminum). In alternate forms of the invention, other grades of aluminum, as well as other materials suitable for aerospace applications known to those in the art, may also be used. For example, in another embodiment, the individual wing segments may consist of a composite material. Further, the individual wing segments may be fabricated by methods other than machining; for example, the wing segments may be fabricated by molding, injection molding, casting, stamping, extrusion, or combinations thereof, or by other methods known to those in the art. In other embodiments, the hinge blocks may not be integral to the wing segment as in the exemplary embodiment described herein. In another embodiment, the hinge blocks may be fabricated separately of any of the materials and via any of the fabricating methods described herein, and attached to the corresponding wing segment by means for attaching such as screws, bolts, rivets, press fit, glueing, welding, soldering, brazing, or by other means for attaching known to those skilled in the art. 
     In a preferred embodiment of the invention, the wing  100  may be used in conjunction with a flying structure  300  as shown in FIG.  6 . In the exemplary embodiment, the flying structure  300  includes a propulsion module  302 , a wing module  304  and a tail module  306 . In other embodiments, the flying structure may include one or more wings  100  attached to a central body. In these embodiments, the central body may further include a tail module, a propulsion module, various aerodynamic control surfaces, control systems, guidance systems, surveillance systems, or combinations thereof, or other aircraft components known to those in the art. 
     The propulsion module  302  is shown in an exploded view in FIG. 7, the wing module  304  is shown in a top view in FIG. 8A, and the tail module  306  is shown in an exploded view in FIG.  9 . The wing module  304  includes two wing assemblies l 00   a  and  100   b , although only the left wing assembly  100   a  is shown deployed in FIG.  8 A. Each wing assembly is attached to a wing module body  308  via awing arm  108  and a back wing support  310 . The wing module body  308  is preferably disposed about a central axis CA. The flying structure  300  is subjected to high-g forces during launch along this central axis CA. A front perspective view of the wing arm  108 , the back wing support  310  and the root wing segment  102   a  of the right wing assembly  100   b  is shown in FIG. 8B. A rear perspective view of the wing arm  108 , the back wing support  310  and the root wing segment  102   a  of the right wing assembly  100   b  are shown in FIG.  8 C. When stowed, the wing assemblies  100   a  and  100   b  reside in the wing module cavities  312   a  and  312   b , respectively. In order to free a wing from its respective wing module cavity during wing deployment, the wings execute a 90 degree rotation about a pivot point. After the 90 degree rotation, the leading edge of the wing  100  faces the flow of air. 
     The wings  100  pivot with respect to the wing module body  308  when the wings  100  convert from the stowed configuration (e.g., wing  100   b  in FIG. 8A) to the deployed configuration (e.g., wing assembly  100   a  in FIG.  8 A). The wings  100  are more likely to survive high-g forces applied along the central axis CA due to acceleration if the span-wise axis  109  is substantially parallel to the central axis CA. Failure of the wing  100  along the span-wise axis  109  is a case of ‘curved shell’ buckling. Because the modified T16 airfoil section has a relatively short radius of curvature, the wing segments  102  exhibit significant resistance to buckling. The buckling characteristics of a wing stowed with the airfoil chord parallel to the central axis CA are such that the wing would not consistently survive the expected acceleration forces along the central axis CA. Acceleration loads applied parallel to the airfoil chord are transmitted through the wing configuration as a plate/column with an initial imperfection. Moreover, with the wing stowed with the airfoil chord parallel to the central axis CA the loads being applied through the thin trailing edge will create high local stresses. Thus, the wing stowed as described for the present invention (i.e., with the span-wise axis  109  substantially parallel to the central axis CA) has superior buckling characteristics with respect to a wing stowed with the airfoil chord parallel to the central axis CA. 
     The wing arm  108  is the junction between a pivot shaft on the back wing support  310  and the wing  100 . The wing arm  108  allows the wing  100  to pivot 90 degrees with respect to the central axis CA out of the wing cavity  312 . The back wing support  310  anchors the pivot shaft and is fastened at the rear end of the wing cavity  312  to the wing module  304 . The acceleration loads along the central axis CA are transmitted from the wing  100 , through the wing arm  108 , and through the back wing support to the flyer. A torsion spring located on the pivot shaft applies torsional force to the wing arm  108  with respect to the back wing support  310 . Thus, when the wing is free from any external forces, the torsion spring forces the wing  100  into the deployed configuration. 
     The propulsion module  302  shown in FIG. 7 includes a propeller assembly  330 , an engine assembly  332 , and a casing assembly  334  that covers the engine assembly and provides a low drag, uniform surface for the forward facing portion of the flying structure  300 . The propulsion module further includes an engine support plate  336  for mounting the engine assembly  332  to the flying structure  300 , an engine starting system  338  for initiating engine operation, a servo motor  340  for throttle control of the engine assembly  332 , an extended drive shaft  342  and a universal joint  344  for rotatably connecting the engine assembly  332  to the propeller assembly  330 . The propeller assembly  330  includes propeller blades, the number, shape and material of which are well known to those in the art, and a cone for aerodynamically streamlining the propeller assembly  330 . The propeller blades are constructed and arranged so as to be convertible from a stowed configuration to a deployed configuration upon an external stimulus. When in the stowed configuration, the propeller blades fold back toward the axis of rotation and withdraw into cavities on the sides of the casing assembly  334 . In one embodiment, the propeller blades are spring-loaded, such that the external stimulus is merely the lack of an external force maintaining the blades in the stowed position, although other means for converting the propeller blades from a stowed configuration to a deployed configuration may also be used. 
     The tail module  306 , shown in an exploded view in FIG. 9, includes two tails  360  (only one of which is observable in FIG.  9 ), and two corresponding servo motors  362  for controlling the position of the tails  360 . The visible tail in FIG. 9 is in its stowed configuration. Both tails may be observed in the deployed configuration in FIG.  6 . The tail module  306  further includes the guidance, navigation, communication and control equipment necessary for the flying structure  300  to carry out its required mission. The tail module  306  includes slots in the tail module body  364  into which the tails  360  retract in the stowed configuration. When the tails  360  convert from the stowed configuration to the deployed configuration upon some predetermined stimulus, the tails  360  rotate 90 degrees about a tail pivot  366 . In one preferred embodiment, the tail module  306  includes actuators that provide the torsional force necessary to deploy the tails  360 ; the actuators preferably include torsion springs located at the tail pivot  366 . In other embodiments, the actuators may include other means for providing rotational motion known to those in the art. The predetermined stimulus may be merely the removal of an external force maintaining the tails in the stowed position. 
     In a preferred embodiment, the present invention is constructed and arranged so as to be compatible with and adapted for launch from a five-inch Navy gun, and to withstand launch forces associated with such a gun. Such launch forces typically include 15,000 g set back acceleration force and a 4,000 g set forward acceleration force, although the invention may also experience and survive other force values. Alternate embodiments of the invention may be constructed and arranged for compatibility with other launch devices and corresponding launch forces known to those in the art. As used herein, to ‘withstand’ the acceleration forces means to survive without degradation beyond that which would allow the invention to complete a predetermined intended mission. 
     The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of the equivalency of the claims are thus intended to be embraced therein.