Abstract:
A portable unmanned air vehicle and launcher system is provided that includes a foldable unmanned air vehicle having a pressure tube; a launch gas reservoir for holding launch gas; a launch tube operatively connected to the launch gas reservoir and having a free end that is positioned in the pressure tube of the air vehicle; a free piston positioned within the launch tube; and a free piston stop to prevent the free piston from leaving the launch tube. A first portion of the launch gas in the launch gas reservoir is released into the launch tube and forces the free piston from an initial position to an end position at which the free piston is stopped by the free piston stop.

Description:
[0001]     This application claims priority to U.S. Provisional Patent Application No. 60/448,472, filed Feb. 21, 2003. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     The present invention relates generally to lightweight air vehicles and launchers used for lightweight air vehicles, and more particularly to unmanned aerial vehicles and pneumatic launchers therefore.  
         [0003]     Lightweight unmanned air vehicles are becoming very popular for various uses including surveillance and package delivery in military and law enforcement situations. Methods for making these UAVs smaller and lighter are needed to improve system transportability. Methods for making them easier to use are needed to improve reliability. Methods for launching UAVs with minimal signature by making them quick and quiet to launch from a very limited space are needed to enable covert operation. There is a need, particularly in military applications, for a transportable, reliable and low signature UAV and launching system that can be carried by one person.  
       BRIEF SUMMARY OF THE INVENTION  
       [0004]     The invention provides a lightweight UAV and a system for launching the UAV that is compact and lightweight so that, for example, a soldier can easily carry the system as a backpack.  
         [0005]     The invention incorporates design features and approaches that are more transportable and reliable and are less detectable than conventional methods. Transportability is achieved by the small size and low weight of the design as well as a protective tube packaging approach. A lightweight materials and structural approach has been used to achieve the small size and low weight. A heavy and complicated launcher is not needed. The outer tube of the launcher is also used as a protective transport tube. This tube, which totally encloses the air vehicle, prevents damage to the light aircraft structures when transported along with other military equipment and supplies to and from the theater of operations.  
         [0006]     Reliability has been achieved by the invention by reducing the reliance on skilled and trained operators. Conventional small UAVs are transported in pieces and assembled when needed. The invention is transported fully assembled and does not suffer reliability problems associated with lost, broken or improperly assembled individual components. Conventional small UAV launcher methods involve procedures and technologies that personnel must perform correctly to achieve a successful launch. Often the launch is unsuccessful which can damage the air vehicle. The invention involves a launch method that can be performed correctly with significantly less training.  
         [0007]     Signature reduction is achieved by a packaging approach, tube launch design and pneumatic launch design features. The packaging approach eliminates the need for air vehicle assembly at the launch location. As a result, the activity of unpacking and assembling the air vehicle is not needed and, therefore, can not be detected. The tube launch design requires very little space to operate. Conventional small UAV launch techniques can require a small field for launching while the invention can launch the UAV from minimal space such as, for example, within the confines of a small bush. The noise reduction design features eliminate the loud popping sound associated with conventional pneumatic launch methods.  
         [0008]     In some embodiments, a hold back mechanism is used to retain the air vehicle on a launch tube when a launch gas reservoir and the launch tube are charged with pressurized gas. When the hold back mechanism is released, the air vehicle is propelled off of the launch tube by the pressurized gas. A free piston in the launch tube allows the air vehicle to be ejected while blocking the exhaust of remaining gas from the pressurized reservoir, thus greatly reducing the noise created during launch.  
         [0009]     Embodiments of the invention provide a launcher for launching a foldable unmanned air vehicle having a pressure tube, the pressure tube being open at a rear end and closed at a front end. The launcher including a launch gas reservoir for holding launch gas; a launch tube operatively connected to the launch gas reservoir and having a free end for inserting into the open end of the pressure tube of the air vehicle; a free piston positioned within the launch tube; and a free piston stop to prevent the free piston from leaving the launch tube. A first portion of the launch gas in the launch gas reservoir is released into the launch tube and forces the free piston from an initial position to an end position at which the free piston is stopped by the free piston stop. The movement of the free piston from the initial position toward the end position in the launch tube occurs as the air vehicle launches.  
         [0010]     Other embodiments of the invention provide a portable unmanned air vehicle and launcher system. The system including a foldable unmanned air vehicle having a pressure tube, the pressure tube being open at a rear end and closed at a front end; a launch gas reservoir for holding launch gas; a launch tube operatively connected to the launch gas reservoir and having a free end that is positioned in the pressure tube of the air vehicle; a free piston positioned within the launch tube; and a free piston stop to prevent the free piston from leaving the launch tube. A first portion of the launch gas in the launch gas reservoir is released into the launch tube and forces the free piston from an initial position to an end position at which the free piston is stopped by the free piston stop. The movement of the free piston from the initial position toward the end position in the launch tube occurs as the air vehicle launches.  
         [0011]     Other embodiments of the invention provide a foldable unmanned air vehicle including a fuselage having a pressure tube portion for receiving a launch tube of a pneumatic launcher; two wings, each wing being pivotably connected to the fuselage such that it pivots about a pivot point; a wing retention mechanism that holds the wings in a folded position; a foldable tail connected to the fuselage; a tail retention mechanism that holds the tail in a folded position; and a linkage that links the wing retention mechanism to the tail retention mechanism such that release of one of the tail retention mechanism and the wing retention mechanism releases the other of the tail retention mechanism and the wing retention mechanism.  
         [0012]     Further objectives and advantages, as well as the structure and function of preferred embodiments will become apparent from a consideration of the description, drawings, and examples. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]     The foregoing and other features and advantages of the invention will be apparent from the following, more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings wherein like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements.  
         [0014]      FIG. 1  is a schematic sectional view of an air vehicle and launcher in accordance with an embodiment of the invention;  
         [0015]      FIGS. 2-6  are schematic views of various stages of launching in accordance with an embodiment of the invention;  
         [0016]      FIG. 7  is a partial sectional view of a detail in accordance with the invention;  
         [0017]      FIG. 8  is a schematic side view of an air vehicle being launched in accordance with the invention;  
         [0018]      FIG. 9  is a perspective view of an example of an air vehicle in accordance with the invention;  
         [0019]      FIG. 10  is a side view of a wing deployment mechanism in accordance with the invention;  
         [0020]      FIG. 11  is a perspective view of the mechanism shown in  FIG. 10 ; and  
         [0021]      FIG. 12  is a partial view of an example of a tail deployment mechanism in accordance with the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0022]     Embodiments of the invention are discussed in detail below. In describing embodiments, specific terminology is employed for the sake of clarity. However, the invention is not intended to be limited to the specific terminology so selected. While specific exemplary embodiments are discussed, it should be understood that this is done for illustration purposes only. A person skilled in the relevant art will recognize that other components and configurations can be used without parting from the spirit and scope of the invention.  
         [0023]     The invention provides a lightweight, unmanned air vehicle and a launcher for the air vehicle that can be carried by a single person in, for example, a battlefield situation. The air vehicle and launcher form a compact, lightweight unit that is durable and easily deployed by a single person. The system launches the air vehicle with minimal noise, making the system particularly appropriate for stealth, covert operations. The extremely low noise levels generated by launching are achieved by containing most of the gas used to launch the vehicle within the system and, thereby, substantially eliminating the gas release noise common with pneumatic launch mechanisms.  
         [0024]      FIG. 1  shows an example of a system  10  in accordance with the invention. System  10  includes an air vehicle  100  and a launcher  200 . Air vehicle  100  has a pressure tube  110  that, in this example, forms a portion of a fuselage  120  of air vehicle  100 . Air vehicle  100  has, in this example, two wings  130  that are folded while air vehicle  100  is in launcher  200 . A tail  140  is also shown schematically at the rear end of air vehicle  100 . A folded propeller  150  is also provided in this example. In preferred embodiments, an quiet, electric motor is used to power the propeller.  
         [0025]     Pressure tube  110  has an open end  112  and a closed end  114 . Pressure tube  110  receives a launch tube (discussed below) of launcher  200  and is the interface of energy transfer between launcher  200  and air vehicle  100 .  
         [0026]     Launcher  200  has a tube  210  that provides an enclosure for the launcher components and air vehicle  100 . Launcher  200  has a launch gas reservoir  220  that stores a gas used to launch air vehicle  100 . Appropriate gases include, but are not limited to, air, nitrogen and helium. Attached to launch gas reservoir  220  is a launch tube  230  that extends into pressure tube  110  of air vehicle  100 . A free piston  240  is located inside launch tube  230  and is permitted to slide freely between an end stop  250  and a stop pin  260 . A valve  280  may be provided to allow an operator control over when gas is permitted to pass from launch gas reservoir  220  to launch tube  230 .  
         [0027]     A hold back mechanism  290  can be used to hold the air vehicle onto launch tube  230  when gas pressure is applied to launch tube  230 . A trigger release mechanism  291  can be provided to release hold back mechanism  290 .  
         [0028]     An example of a launch sequence is shown in  FIGS. 2-6 .  FIG. 2  is a simplified view of the system immediately prior to launch (similar to  FIG. 1 ). With hold back mechanism  290  engaged, pressurized gas filling launch gas reservoir  220  will be applied to launch tube  230  and free piston  240 .  FIG. 3  is a view of the system shortly after hold back mechanism  290  is activated and launch gas is allowed to transfer from launch gas reservoir  220  to launch tube  230 . In this view, air vehicle  100  (schematically represented by pressure tube  110 ) has moved relative to launch tube  230  under the force exerted on closed end  114  of pressure tube  110  by the launch gas that has moved from launch tube  230  into pressure tube  110 . The arrows in  FIG. 3  represent launch gas moving around free piston  240  through spaces between free piston  240  and the inside wall of launch tube  230 . The size and number of these spaces is important to properly regulate the amount of launch gas that passes by free piston  240  during the launch procedure. If the spaces allow too much launch gas to pass by free piston  240 , the result will be excessive gas loss which will result in an undesirable noise signature. In the extreme case, the entire volume of launch gas could be lost, creating the maximum noise signature. If the spaces are too restrictive and allow too little launch gas to pass by free piston  240 , free piston  240  could block the open end of launch tube  230  before air vehicle pressure tube  110  clears launch tube  230 . When this happens, the launch energy is isolated from air vehicle  100  and launch performance (velocity) is reduced.  
         [0029]      FIG. 4  shows free piston  240  at rest against end stop  250  of launch tube  230  and pressure tube  110  preceding further away from launch tube  230 . When free piston  240  is in this position, it is pressed against, and forms a seal with, end stop  250  to prevent any further launch gas from escaping from the system.  FIG. 5  shows pressure tube  100  clearing the end of launch tube  230 . At this point, air vehicle  100  will be clear of, or almost clear of, tube  210  of launcher  200 . After the launch is complete, free piston  240  has sealed most of the pressurized gas from escaping the system.  
         [0030]     To reuse the launcher, the operator has several options depending on the design features included in the launcher. In the simplest launcher design, the pressurized gas is vented to the atmosphere using a venting needle valve located, for example, between launch gas reservoir  220  and launch tube  230 . Once the gas is vented, free piston  240  releases from end stop  250  and an air vehicle can be installed and latched in position using hold back mechanism  290 . To execute another launch, the launcher may need to be charged by an external pressure source. If the launcher is equipped with a valve  280 , this can be closed off. Pressure inside launch tube  230  is vented to allow free piston  240  to fall to the pre-launch position. This venting can be accomplished by several methods, including: (1) a vent valve located between valve  280  and launch tube  230 ; (2) a slow leak like a pin hole in free piston  240  which would slowly vent the chamber; or (3) a vent valve located in free piston  240  that could be manually activated to vent the chamber. Once launch tube  230  is vented, another air vehicle can be mounted. A small boost charge from an external pressure source may be required. If the launcher is not equipped with valve  280  and venting is not desired (since it wastes pressurized gas), a vent valve located in free piston  240  and a small pin device located inside pressure tube  110  can be used. During engagement of hold back mechanism  290 , the pin could push the vent valve in free piston  240  allowing free piston  240  to unseal and fall to the pre-launch position. A small boost pressure charge from an external pressure source may be required to restore full launcher performance.  
         [0031]      FIG. 7  shows a larger scale view of free piston  240  forming a seal with end stop  250  as described above in reference to  FIG. 4 . An optional seal  292  is shown between end stop  250  and pressure tube  110 .  
         [0032]      FIG. 8  shows the air vehicle  100  after being launched from tube  210 . This embodiment is provided with two legs  270  positionable against tube  210  in a stored position and deployable to the position shown in  FIG. 8 . Legs  270  are preferably adjustable to compensate for different terrain at the launch site.  
         [0033]      FIG. 9  is a perspective view of an air vehicle  100 ′ in accordance with the invention. In this figure, air vehicle  100 ′ is shown in the flying, unfolded state. Wings  130  pivot about shaft  138  from the closed (storage and launch) position to the open (flight) position under the force of springs or other urging devices. Tail  140  also moves from a folded (storage and launch) position to a open (flight) position after leaving tube  210  of launcher  200 .  
         [0034]      FIGS. 10 and 11  show an example of a mechanism that links the opening of tail  140  and wings  130 . In this example, a linkage  136  connects a tail plug  148  to a slider  134  that is provided with a wing knife  132  that engages wings  130  in the closed position. Upon tail  140  opening, tail plug  148  slides relative to fuselage  120  and, through linkage  136 , moves slider  134  to fuselage  120 . As a result, wing knife  132  moves relative to wings  130  and disengages from wings  130  allowing wings  130  to open under the force of, for example, springs.  
         [0035]      FIG. 12  shows an example of a tail release mechanism. In  FIG. 12 , air vehicle  100  is being launched and pressure tube  110  is about to clear launch tube  230 . Tail  140  (two tail fins are shown in this view) is held in the closed position by at least one cam  144  that engage a lock recess  146  in at least one of the fins of tail  140 . A spring  142  attempts to push cam  144  into a cam recess  116  in the wall of pressure tube  110 . In the position shown in  FIG. 12 , the progress of cam  144  through cam recess  116  is prevented by the presence of launch tube  230 . As pressure tube  110  continues upward in  FIG. 12  as the launch progresses, pressure tube  110  clears launch tube  230  and launch tube  230  no longer prevents cams  144  from progressing through cam recesses  116  under the force of springs  142 . As cams  144  progress through cam recesses  116 , cams  144  disengage from lock recesses  148  and allow the fins of tail  140  to move to the open position under spring, or other, force.  
         [0036]     It is to be understood that even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size and arrangement of parts within the principles of the invention.  
         [0037]     The embodiments illustrated and discussed in this specification are intended only to teach those skilled in the art the best way known to the inventors to make and use the invention. Nothing in this specification should be considered as limiting the scope of the invention. All examples presented are representative and non-limiting. The above-described embodiments of the invention may be modified or varied, without departing from the invention, as appreciated by those skilled in the art in light of the above teachings. It is therefore to be understood that the invention may be practiced otherwise than as specifically described.