Patent Abstract:
Embodiments of the present invention provide improvements to UAV launching systems. The disclosed launching system eliminates the use of hydraulic fluid and compressed nitrogen or air by providing an electric motor-driven tape that causes movement of a shuttle along a launcher rail.

Full Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application Ser. No. 61/870,281, filed Aug. 27, 2013, titled “Electric UAV Launcher,” the entire contents of which are hereby incorporated by reference. 
    
    
     FIELD OF THE DISCLOSURE 
     Embodiments of the present disclosure relate generally to an electrically powered launcher system designed to launch an unmanned aerial vehicle (UAV). The embodiments of this electrically powered launch system provided are generally more lightweight than current hydraulic-pneumatic launching systems. They also do not use hydraulic fluids and fuel for an engine for the launching process. This renders the system environmentally sound because fumes and spills may be eliminated. Through the use of feedback-based controls tied into a drive motor, the launch acceleration profile can be programmed and potential g-load spikes mitigated. 
     BACKGROUND 
     Launching systems for unmanned aerial vehicles (UAV) are designed to create enough force and speed that the UAV can be ejected into the air. The general concept behind a UAV launching system is to take a vehicle from rest to the desired flight velocity in a minimum distance, without imparting destructive forces to the vehicle. UAV launcher systems for vehicles weighing thirty pounds or more typically use a pneumatic or pneumatic/hydraulic system as the prime propulsion system. 
     The traditional approach to take-off for many UAVs (including taxi, accelerate, lift-off, and climb) often requires a distance of 200 feet or more. This traditional take-off minimizes the acceleration (g-load) on the vehicle because it is accelerated over a longer distance. However, there is a desire to design systems that can obtain the desired launch velocity in less than 50 feet in some instances. For example, on shipboard applications and other instances, space may be limited. In addition, the landing gear associated with runway take-off and landing operations adds weight and thus requires more power and fuel to sustain flight operations. 
     However, the use of a launcher that allows shorter distance to achieve flight (because the acceleration is faster) generally means higher g-loads. There are often expensive electronics on-board the UAV that cannot withstand such high g-loads. Other limitations to launch parameters include a minimum launch velocity or a maximum space to launch. The design and optimization of the launcher then becomes a balance of launch stroke length, vehicle acceleration, vehicle weight to be launched, and launch angle. 
     The power source for the UAV launchers designed to date has typically been a self-contained power source in the form of a closed loop hydraulic/pneumatic system, which stores energy when dry nitrogen is compressed in an accumulator by pumping in hydraulic fluid. The hydraulic pump is usually driven by either an electric motor, a gasoline engine, or by a multi-fuel engine. 
     Historically, closed loop hydraulic-pneumatic systems have proven to be the most reliable and repeatable under the widest range of environmental conditions. To prevent condensation at extreme temperatures, dry nitrogen (GN 2 ) is used, instead of air, to fill the “pneumatic” side of a piston accumulator. The nitrogen is pre-charged to a pre-determined pressure. A hydraulic pump then pressurizes the hydraulic side of the accumulator piston, which compresses the nitrogen and raises the launch pressure. Once the optimal launch pressure is reached, the system holds the pressure via check valves until launch is initiated. Upon launch initiation, the valve opens, the nitrogen expands, pushing the fluid out of the accumulator and into the cylinder. This accelerates the cylinder piston, the reeving cable, shuttle and vehicle. 
     However, there are some limitations and problems associated with pneumatic launchers. For example, there is typically an accumulator associated with the system that must be pre-charged to a specific pressure to achieve the desired launch velocity for a given UAV weight. If a different speed is required or if the weight of the UAV varies (due to fuel load or ordinance), the pre-charge pressure must be adjusted accordingly. This generally requires that gas (typically air or dry nitrogen) either be bled from or added to the system via a separate gas bottle. The need to vary the pressure adds to system complexity and potentially increases the overall system weight (e.g., if a gas bottle positioned on-board the launcher is used). 
     With a pneumatic launcher, it can be also difficult to control the g-load imparted to the UAV when the pressure is released into the mechanical drive components at the initiation of the launch cycle. These spikes in the g-load at the beginning of the launch cycle can have potentially disastrous impacts on the UAV and the on-board electronics and other systems. These initial g-load spikes can be mitigated through control valves that release the hydraulic fluid from the accumulator into the drive cylinder in a controlled fashion. However, these valves are often expensive and add weight to the overall system. 
     Additionally, many UAV launchers are used in an expeditionary mode, where they need to be mobile and capable of being transported to a location for deployment. In some cases, they may be mounted to the back of a truck. In other cases, they may be trailer mounted and either towed into position or slung from the underside of a helicopter and air lifted into position. In most cases, the overall size and weight of the launcher system must be minimized to ensure that it can fit within certain aircraft or transport containers. The main drive components of a hydraulic/pneumatic launcher (accumulator, pump, launch cylinder, gas bottle, reservoir, etc.) add substantial weight to the system, and weight is a primary limitation to mobility of the system. 
     With any hydraulic/pneumatic system, leaks are always a concern. Loss of gas pressure or a hydraulic leak could potentially shut down operations. Once fielded, it is unlikely that there will be access to gas cylinders to address leaks in the system. 
     Launch timing can also be an issue with a hydraulic/pneumatic system. Depending on the differential between the pre-pressure and final launch pressure, the size of the pump and amount of hydraulic fluid to be moved, it can take up to several minutes to bring the system up to launch pressure. The UAV is typically mounted on the launcher, and its engine is running during this pressurization time, making it susceptible to overheating. 
     Reset can be another challenge presented by a hydraulic/pneumatic system. Resetting a hydraulic/pneumatic launcher after completion of a launch requires that the shuttle be pulled back into the launch position. This may take several minutes because, as the shuttle is pulled back, the hydraulic fluid needs to be pushed out of the cylinder and back into the reservoir. The time required to reposition the shuttle negatively impacts the overall cycle time. 
     One launcher design that does not use a hydraulic system is described in U.S. Pat. No. 4,678,143. The launcher described by this patent uses a flywheel that provides the energy required for the launch sequence. The flywheel is spun up by a small electric motor that is powered by a generator, and an electric clutch engages the flywheel when the launch cycle is initiated. The flywheel drives a cable drum that wraps cable around the drum during the launch sequence. One of the disadvantages with this launcher is that the flywheel may take several minutes to come up to launch speed. Another disadvantage is the requirement of a generator as a power source, which can add a great deal of weight to the system. 
     BRIEF SUMMARY 
     Improvements to UAV launching systems are thus desirable. In particular, improvements that eliminate the use of hydraulic fluid and compressed nitrogen or air are desirable. Improvements that eliminate the use of a flywheel to provide energy fix a launch sequence are desirable. Systems that are lighter, more reliable, allow more control of g-load, that do not threaten leaks, that do not take several minutes to launch, and that do not take several minutes to reset are desirable. 
     Embodiments described herein thus provide a launching system for an unmanned aerial vehicle that uses a launcher rail, a shuttle configured to travel along the launcher rail, and a drive mechanism for moving the shuttle along the launcher rail. The drive mechanism can include a length of tape secured to the shuttle, an electric drive motor that drives movement of the tape, and a drive reel to which one end of the tape is secured and around which the tape is wound during launch. The tape may be nylon, a nylon blend, or some other material. The electric motor may be a DC motor or some other motor that comports with the weight and size requirements for the particular system. The electric motor may be battery powered. In a specific design, the electric motor is powered by a Lithium Ion battery. 
     This disclosure provides a UAV launching system that provides launch using completely electric launch components, including the braking and control system. There are no hydraulic systems on board that could present environmental issues in the event of a leak. The launch system described may be mounted to a base or pallet that can in turn be mounted to a trailer, dolly type wheel base, a flat bed truck, train flat car, ship deck, or any other appropriate launching location or surface. The modularity of the components used also allows scalability for higher energy UAV launches. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a side plan schematic view of one embodiment of a launching system, using an electric motor-driven power reel and a payout reel to move a shuttle along a tape. 
         FIG. 2  shows a perspective view of a launcher rail at an angle, without a shuttle in place. 
         FIGS. 3A-C  show a launch series with a UAV being released from a shuttle. 
         FIG. 4  shows a side plan schematic view of the launching system of  FIG. 1 , with the shuttle being detached from the tape. 
         FIG. 5  shows a side plan schematic view of a launching system that uses end sheaves for controlling winding of the tape. 
         FIG. 6  shows a side plan schematic view of a launching system with a shuttle that remains secured to the tape. 
         FIG. 7  shows a side plan schematic view of a launching system that uses a power reel, without a payout reel. 
         FIG. 8  shows a side perspective view of a launching system that uses a cable wrapped around a drum, driven by the motor, and pulleys on the shuttle. 
         FIG. 9  shows a free body diagram of the embodiment of  FIG. 8 . 
         FIG. 10  shows a side view of a launching system with panels that can be used to help raise the tape for folding of the rail. 
         FIG. 11  shows a side plan schematic view of a launching system that uses a conveyor belt. 
         FIG. 12  shows a side view of an alternate conveyor belt system. 
         FIG. 13  shows a side view of a launching system using a steel cable wound around a drum and driven by an electric motor. 
         FIG. 14A  shows one embodiment of a braking system that may be used for a launching system. 
         FIG. 14B  shows a schematic view of the braking system of  FIG. 14A . 
         FIG. 15  shows a side plan schematic view of a launching system in use. 
         FIG. 16  shows a schematic illustration of a mechanism that may be used to secure a shuttle to a cable. 
     
    
    
     DETAILED DESCRIPTION 
     UAV launchers may be offered with fixed or mobile installation, various rail options (telescoping rails or elongated fixed rails), manual or automated operation, and designed for a variety of UAV configurations and designs based on desired performance and cycle times. The systems described herein may be used on any of the various types of launching systems. In one embodiment, the launching system described may be mounted on a motor vehicle that can transport the launching system to the desired location for launch. The launch may occur while the system is on the vehicle, or the system may be removed from the vehicle for launch. In another embodiment, the launching system described may be installed at a fixed location. 
     As shown in  FIG. 1 , in one embodiment, there is provided a launching system  10  that uses a motor-driven belt or tape mechanism  12  that is attached to a shuttle assembly  14 . The shuttle  14  is the carrier that transfers the energy required for launch to the UAV. As shown in  FIG. 2 , the shuttle  14  may travel along a length of a launcher rail  16 . The launcher rail  16  is typically inclined. This incline may be achieved by struts  18  that rest on a surface or are secured to a surface. Struts may be secured to a base or pallet that may be mounted to a trailer, wheel base, flat bed truck, train flat car, ship deck, or any other surface or vehicle designed for launching. Alternatively, the struts may rest on a ground surface. The launcher rail  16  may be a fixed track of fixed length or it may have an extendable boom that elongates the rail. For example, the extendable boom may be hinged, such that it could be folded and the length would not be obtrusive to typical transport methods. In another embodiment, the extendable boom may be driven out from a retracted position, or may be extended in any other appropriate manner to elongate the launcher rail  16  into an extended track if needed. The launcher rail  16  length is typically contingent on the distance required to achieve the desired final launch velocity, without exceeding a pre-defined g-load threshold of the UAV, as well as the distance required to stop or arrest the shuttle.  FIG. 2  also shows that one or more batteries  64  may be positioned on a base  66 , along with one or more motor control components  68 . 
     The launcher rail  16  may be used to guide the shuttle  14  along the drive length  20  of the rail  16 , in the direction of launch, illustrated by the arrow in  FIG. 1 . (For ease of review,  FIG. 1  does not show a launcher rail or an incline, although both would generally be incorporated into a final launch system.) As the shuttle  14  travels along the rail  16 , the motion of the shuttle  14  transfers the launch velocity to the UAV. ( FIG. 1  does not show a UAV secured to the shuttle  14 .  FIGS. 3A-C  show a potential launch sequence.) 
     Rather than securing a cable to the front of the shuttle, which is how most current launching systems work, the shuttle  14  is secured to a tape  12  that runs the length of the launcher rail  16 . More specifically, a belt or tape  12  is used to cause movement of the shuttle  14  along the launcher rail  16 . The shuttle  14  is generally secured to the tape  12  at a shuttle to tape interface  22 . This interface  22  may be any appropriate connection. In one embodiment, the shuttle to tape interface  22  may be provided as a pin  24  attached to the tape that cooperates with a corresponding structure on the shuttle  14 . This embodiment is shown in  FIGS. 3A-C  and  15 . For example, the undercarriage of the shuttle may have a hook  26  or some other detachable connection feature attached thereto that cooperates with the pin  24 . In another embodiment, the interface  22  may be formed from any type of upward protrusion  28  on the tape  12  that is shaped to cooperate with a lower protrusion or hook on the shuttle. In another embodiment, the interface  22  may be an non-detachable connection between the shuttle and the tape. In another embodiment, the interface may be formed as a clamp, where the shuttle secures two ends of the tape to one another at a location on the shuttle. Other connections are possible and within the scope of this disclosure. 
     In use, a UAV is secured to an upper surface of the shuttle  14  as shown in  FIGS. 3A-C . The attachment of the UAV to the shuttle  14  may be via any appropriate connection currently in use or as may be developed, including any of the above described options. An abrupt stoppage of the shuttle  14  causes the UAV to launch off of the shuttle  14 . 
     The tape  12  may run along the drive length  20  of the launcher rail  16 . In one embodiment, its ends are generally secured to one or more of a payout reel  36  and/or a power reel  30 , as shown in  FIGS. 1, 4-6, and 15 . In another embodiment, one end of the tape  12  may be detachably secured to the shuttle and one end is secured to a power reel, as shown in  FIG. 7 . In another embodiment, a cable is used, and the cable is wrapped around a drum, driven by the motor, as shown in  FIGS. 8-9 . In another embodiment, the tape  12  is a continuous tape that runs as a conveyor belt along the launcher rail, as shown in  FIGS. 11-12 . In another embodiment, a steel cable or rope may be wound around a pair of drums  90 , as shown in  FIG. 13 . In another embodiment, an alternate braking system may be provided, as shown in  FIGS. 14A-B . Each of these embodiments is described in further detail below. 
     The tape  12  may be formed of a material that has more elasticity or stretch than cables used in typical launching systems. For example, the tape  12  may be formed from nylon, a nylon blend, or another synthetic material. In some embodiments, the tape may be formed of a material that has an amount of inherent stretch. The stretch inherent in the material used can help mitigate the g-force during the initial application of launch load. However, the stretch of the material is not required. In other embodiments, tapes or belts containing metallic reinforcing fibers may be used. The electronic control system in conjunction with the electric motor can be used to tightly control the acceleration profile of the launch cycle. 
     In the embodiment shown in  FIG. 1 , a tape  12  is attached at one end to a power reel  30 , which is mounted to a drive shaft  32  of an electric motor  34 . Details of the electric motor are described more below, but in one embodiment, the electric motor  26  may be a DC motor. The electric motor  34  is what drives movement of the tape  12 . In use, the electric motor  34  remains stationary with respect to the launcher rail  16  and the remainder of the shuttle guiding components. 
     The opposite end of the tape  12  may be attached to a payout reel  36 . As shown in  FIG. 1 , the payout reel  36  may generally be positioned near a battery position end  38 , and the power reel  30  is generally positioned near a launching point  40  of the launching system  10 . Once the electric motor  34  is energized, the motor rotates the power reel  30 , which winds in the tape  12  from the payout reel  36 . This winding of the tape  12  accelerates the shuttle  14 , which is attached to the tape  12  (and consequently accelerates the UAV, which is attached to the shuttle  14 ). The payout reel  36  contains at least a sufficient length of tape  12  that allows full travel of the shuttle  34  up the rail. 
     As shown in  FIG. 1 , the shuttle  14  may be connected to the tape  12  via a hook  26  (or some other detachable connection on the undercarriage of the shuttle  14 ) that attaches to an interface  22  on the tape. In the embodiment shown, the interface  22  is provided as a pin, protrusion  28 , or other raised structure that can interface with the shuffle hook. Actuation of the electric motor  34  causes movement of the shuttle  14  along the power zone  100 . The shuttle  14  accelerates to launch velocity over the entire length of the tape  12  in this zone  100 . It should be understood that the rail is not shown in  FIG. 1  and that there will be sufficient rail length beyond the shuttle to tape separation point  40  in order to bring the shuttle to an abrupt stop. 
       FIGS. 3A-C  show a sequential series illustrating a shuttle  14  with a UAV  70  positioned thereon, and its travel along the tape  12 . In  FIG. 3A , the shuttle  14  is shown traveling along the rail  16 . In  FIG. 3B , the shuttle  14  is shown engaging an arrestment strap  72 . The arrestment strap  72  functions to stop forward momentum of the shuttle  14 . In this figure, the shuttle  14  has just engaged the arrestment strap  72  and the UAV  70  is ready to depart the shuttle  14 . In  FIG. 3C , the arrestment strap  72  has stretched to absorb shuttle energy, and the UAV  70  has been released. 
     In some examples, when the shuttle  14  reaches a shuttle to tape separation point  40  or another launching point, the shuttle  14  may be released from the tape  12 . This release generally occurs once the interface  22  on the tape is wrapped around the end of the power reel  30 , as shown in  FIG. 4 . 
     In the embodiment of  FIG. 4 , the shuttle  14  is allowed to release from the tape  12 . A shuttle  14  that separates from the tape  12  can eliminate the need for precise timing because the tape does not have to stop at a particular point. Stopping the released shuttle  14  may be accomplished via an arrestment strap, a braking mechanism at the end of the rail, a braking system on-board the shuttle itself, or any other appropriate system. As shown in  FIG. 4  (and as also illustrated by the launch series of  FIGS. 3A-C ), an abrupt stop of the shuttle  14  in the shuttle braking zone  102  may release the UAV from the shuttle  14 . (This may be in addition to the shuttle  14  also releasing from the tape  12 .) 
     In the embodiment shown in  FIG. 5 , end sheaves or pulleys that provide a path for the tape may be mounted on or below or otherwise with respect to the launcher rail  16 . A first sheave  46  may be mounted at the battery position end  38 . A second sheave  48  may be mounted at or near the launching end  40 . In another embodiment, the second sheave  48  may be mounted at some length before the launching end  40  of the rail  16  in order to allow distance for the shuttle  14  to be arrested at the end of the power stroke. In use, the first sheave  46  routes the tape  12  from the payout reel  36  over the upper horizontal surface  50  of the launcher rail  16  to the second sheave  48 . The tape  12  may then be routed over the second sheave  48  down to the power reel  30 . The power reel  30  and the payout reel  36  may be mounted to the underside of the launcher rail  16 , as shown in  FIG. 5 . In an alternate embodiment, the power reel  30  and the payout reel  36  may be mounted to a base on which the launcher rail  16  may be mounted. 
     Use of first and second sheaves  46 ,  48  can lend advantages to the system  10 . For example, the increase in the diameter of the power reel  30  due to the tape  12  being wrapped onto it during the power stroke could lead to interference with the shuffle  14 . Routing the tape  12  over an end sheave  48  and positioning the power reel  30  underneath the launcher rail can lessen the chance that the increase in the tape  12  stack could impact movement of the shuttle  14 . Likewise, the same condition exists at the payout reel  36  end, but the diameter of the tape  12  on the payout reel  36  decreases during the power stroke, due to the tape  12  being pulled from the payout reel  36 . This could also lead to the tape  12  interfering with the launcher rail  16 . Positioning the payout reel  36  under the launcher rail  16  also provides space at the battery position end  38  of the rail, where the UAV is to be loaded onto the shuttle carriage  14 . Additionally, the added distance between the power reel end sheave  48  and the power reel  30  itself can allow the power stroke to be shut down prior to when the shuttle/tape interface  22  would be wrapped onto the power reel  30 . Wrapping tape  12  over this interface  22  could potentially deteriorate the tape. 
     In another embodiment shown in  FIG. 6 , the shuttle  14  may be non-removeably secured to the tape  12 . For example, the undercarriage of the shuttle  14  may feature a connection that completely captures the shuttle to tape interface  22 , which may be a pin or other component secured to the tape  12 . The tape  12  may be manufactured from a continuous strip of material. In another example, the tape  12  may be manufactured from a non-continuous strip of material. For example, if the tape  12  is not fabricated from a single continuous strip, two sections can be used and connected to the tape interface  22 . Using two tape sections may be advantageous in that the section connected to the braking reel could be fabricated from a different and potentially higher strength material to help aid in braking the weight of the shuttle. This interface  22  generally prevents the shuttle  14  from disengaging from the tape  12 . As shown, the shuttle  14  stops in a braking zone  102  before the end of the rail. The UAV is released from the shuttle  14  in this braking zone  102 . The tape  12  may be used to arrest the shuttle  14  via a braking system  54  contained on the payout reel  36 . In one embodiment, electrically actuated brakes may be used to prohibit the use of hydraulic fluids or pneumatic brakes. An optional arrestor strap or secondary braking system (as described previously) may also be used to supplement the shuttle  14  arrestment. 
     In another embodiment, the payout reel  36  could be eliminated, as shown in  FIG. 7 . In this embodiment, the power reel  30  is used to accelerate the shuttle  14  and the tape  12 . The power reel  30  may be associated with the electric motor  34  as described above. After the shuttle  14  disengages, the tape, including the interface/pin  22 , would wrap completely around the power reel  30 . The shuttle  14  arrestment may be through an arrestment strap, a rail based brake, or an on-board shuttle brake. 
     Another embodiment may use a cable  78  that is wrapped around a drum  82 , driven by the motor  84 . One example of which is shown in  FIGS. 8 and 9 . In this embodiment, the shuttle  14  has two pulleys  74 ,  76  located on its lower surface. One pulley  74  may serve as the launch guide for the cable  78 . The other pulley  76  may serve as an arresting guide. A braking drum  80  may act as an anchor point for launch. A winding drum  82  reels in the cable  78  to propel the shuttle  14  down the rail  16 . Two fixed pulley assemblies  120 ,  122  may be located along the rail  16 , mounted to opposite sides of the rail  16 . Each fixed pulley assembly  120 ,  122  may actually comprise two or more pulleys, as shown. In the embodiment shown, the fixed pulley assemblies  120 ,  122  may be located on the rail  16 , at the location where the cables come in from the braking drum  80  and the winding drum  82 . The cable  78  pulls against pulley  76  (on the shuttle) until the shuttle  14  crosses the rail section where the cables come in from the braking drum  80  and the winding drum  82 . At that point, the cable  78  flips to pulley  74  on the shuttle for the braking action. This may be referred to as “flexing.” Accordingly, when the shuttle  14  crosses the point on the rail  16  where the two fixed pulley assemblies  120 ,  122  are located, the cable  78  transitions from the shuttle&#39;s launch pulley  76  to its arresting pulley  74 . The winding drum  82  may be stopped with a brake. The braking drum  80  may allow some pay-out of the cable  78  as it brings the shuttle  14  to a stop.  FIG. 8  also shows an arresting strap  72  in place along the rail  16 . The strap  72  extends along either side of the rail with a center strap portion  73  crossing over the rail. 
     In a specific example, a synthetic rope may be used as the cable  78 . This may help alleviate possible issues with flexing a steel cable around a small pulley and then reversing the direction of flex suddenly. 
     Many of the particular designs described herein have generally used a flat tape  12  that runs almost the entire length  20  of the launcher rail  16 . In some embodiments, the rail  16  may need to be folded for transport and the tape may lie perpendicular to the direction of the fold. In this case, it is possible to provide a set of “paddles”  86  that may be added to the rail sections  16  adjacent to hinges. One example of this is shown in  FIG. 10 . The paddles  86  may be provided in order to raise one edge of the tape  12  above the rail flanges  17 , such that the paddles  86  facilitate folding of the rail  16  through the thin section of the tape  12 . The paddles  86  may tilt the tape  12  at an angle to allow it to fold through its thin section. In another variation, the tape  12  could be mounted at about 90 degrees to this design such that the flat section would be in the plane that the hinge rotates. 
     In a further embodiment shown in  FIG. 11 , a conveyor configuration may be used. In this embodiment, one or more electric motors  34  drive a pulley that moves a continuous loop belt or chain  56 . The continuous loop belt or chain  56  can engage the shuttle  14  in any of the above-described ways. Once the shuttle  14  reaches the end of the power stroke, it disengages from the belt  56 . The shuttle  14  may be arrested via an arrestment strap or any other braking system. In another embodiment, the shuttle may be securely attached to interface  22  and the braking forces applied through the conveyor belt. 
       FIG. 12  shows a schematic of an alternate conveyor concept. This concept utilizes a shuttle  14  that is restrained to a drive belt  56  as the tape  12  that provides a continuous loop. The shuttle  14  may function as a clamp that holds the end of the belt together. A drive motor  34  may connect to an input shaft  104 . A drive pulley  106  may be connected via a sprocket and chain to the drive motor output shaft or it may be directly connected to the motor output shaft. Shuttle braking may be accomplished by variable electric braking, by an arresting strap variation, or by any other appropriate method. In this embodiment, the shuttle is connected directly to the belt to form the continuous loop. This implies that the shuttle must be stopped prior to reaching the end pulley  108  during a launch or the shuttle would attempt to wrap around  108 . Another embodiment may have the shuttle  14  disconnect from the drive belt prior to reaching pulley  108 . 
     An alternate launching embodiment is shown in  FIG. 13 . This concept may use a continuous steel rope  88  wound around a pair of drums  90  which have spring tension forcing them apart and applying force to increase friction between the steel rope  88  and the drums  90 . One of the drums may be coupled to the drive motor assembly  92  through a belt or chain. This allows the capstan drums  90  to be mounted to the rail for ease of rail tilting for adjustment of launch angle. The shuttle  14  may be attached to the rope  88  by a mechanism  126  similar to that used for a ski lift. At the end of the stroke, variation in the shuttle wheel guide space can allow a clamping mechanism to open, and the shuttle  14  can freewheel into an arresting strap. 
     In one example, as shown in  FIG. 16 , the clamping mechanism  126  may be attached to the bottom of a shuttle and may be used to secure the shuttle to the cable. In the clamped position, wheels  128  may ride within rail slots in order to constrain the clamp mechanism. Upper rail guides  134  may hold the cable gripping jaws  132  closed such that the gripping jaws  132  are clamped over cable  88 . In the released position, the jaws  132  release. This can be accomplished when the wheels  128 , which may be spring-loaded wheels, proceed beyond the upper rail guide  134 . In one embodiment, the upper rail guides are tapered along the length of the rail to allow transition from the open to the clamped position. 
     In another embodiment, an alternate braking mechanism may be provided. One example is shown in  FIGS. 14A  and B. This variation provides an arresting tape  97  that may be attached to the shuttle. For example, the back end of the shuttle  14  may be connected to an arresting tape  97  that trails behind the shuttle. The arresting tape  97  can be wound onto the tape reel  96  with a clutch, brake, and rewind motor. The launch tape  12  may be secured to the shuttle  14  using any of the options described herein. The launch tape may be driven by the drive motor assembly  94  for moving the shuttle  14  along the rail  16  as described herein. The drive reel  92  is shown directly to the right of the braking reel  96 , and a sprocketed drive reel  124  is shown just under the drive reel  92 . As shown, a sprocket  124  and chain may be used between the motor  94  and the drive reel  92 .  FIG. 14B  shows a schematic of this braking option. 
     The launch tape  12  and the arresting tape  97  may be of different materials to obtain different performance characteristics. Although this may add drag to the system, it allows for automatic rewind and can provide a “hands off” arrangement. This may provide a launching system that can be a self-deploying launcher. 
     For this braking embodiment, the timing of the launch to arrestment sequence may be critical. The shuttle  14  can be traveling up to about 140-145 feet per second when the transition from launch to arrestment takes place. The timing of the launch signal may be delivered from a Programmable Logic Controller (PLC) to a drive controller in order to shift the motor from powered launch to coast, while engaging the brake. A fast responding and repeatable brake may be provided to ensure success. This system may be provided with an electric brake to eliminate the need for hydraulic braking systems. However, a hydraulic brake may be used. The brake may be variable in order to adjust to different weights and speeds. 
       FIG. 15  shows one embodiment of a launcher system  10  with the launcher rail  16  inclined at an upward angle, and with the shuttle  14  positioned on the tape  12  on the rail  16 . This embodiment provides a battery position sensor  58 , which is activated when the shuttle  14  is in a battery, or pre-launch, position. When the shuttle  14  is pulled back to the battery position, it activates sensor  58 . Activation of the sensor  58  activates a brake on the payout reel  36  to keep the tape taught. (In some embodiments, for safety purposes, the launch sequence cannot be initiated unless the shuttle has been secured in the battery position.) When launch is activated, the electric motor  34  is energized and the brake on the payout reel  36  is disengaged. Disengaging the brake allows the shuttle  14  to move along the rail  16 . The motor  34  activates the power reel  30  to wind the tape, causing movement of the tape  12  and the attached shuttle  14 . A power reel shutdown sensor  60  may be positioned along the rail  16 , toward the launching end  40 . When the shuttle  14  reaches this sensor  60 , a signal is sent to the motor  34  to stop movement of the power reel  30  and/or to activate payout reel  36  brakes. The tension in the tape  12  created by the stopping and/or braking action abruptly stops the shuttle and causes release of the UAV. If the embodiment in which the shuttle releases from the tape  12  is used, then the shuttle may be stopped by an arrestment strap or other stopping features, which abruptly stops the shuttle and causes release of the UAV. 
     In many of the above embodiments, the electric motor  34  is shut down immediately prior to the arrestment of the shuttle  14  such that the motor does not continue to supply power and potentially damage the shuttle or drive mechanisms. The payout reel  36  may also be connected to a rewind motor that can retract the tape  12  into the battery (or launch) position such that another UAV could be quickly loaded and readied for launch. Applying the power stroke by reeling in tape  12  in this manner to achieve the launch velocity is not used on any other commercially available launchers. 
     In some embodiments, it has been found that a DC motor provides desirable driving features and speeds. The electric motor may be used in conjunction with a battery system to enhance portability. The battery may be a Lithium Ion battery system. The electric motor may also be used in conjunction with a Programmable Logic Controller (PLC). The PLC can allow the motor RPM (revolutions per minute) to be adjusted as required throughout the launch sequence to provide a controlled acceleration and thus mitigate the high initial G-spikes typical of a hydraulic/pneumatic system. Use of a PLC also allows the ability to dial in the launch loads, making it easy to adjust for weight or speed variances and eliminating the need for time consuming changes to the launch pre-pressure by adding or purging gas from the system. For example, the G force may be minimized by programming the shape of the G force curve in the controller. 
     The functions of the PLC could possibly be integrated into drive control functions and be combined into one unit. Alternatively, the PLC may be a separate component that can be optionally added to the system. 
     One specific embodiment of a motor that may be used with the electric launcher is a DC motor propulsion system and controller. This motor can be powered by a Lithium Ion battery. Other types of electric motors may be used. For example, an AC motor with a similar torque output may be used. However, it is believed that such an AC motor would be significantly larger and heavier than the DC motor. The DC motor was chosen for the initial application based on the ability of the batteries to supply a surge of current that is typically not available from AC power sources. Alternately, AC power with suitable transformers and discharge capability could be used to power the DC motor. 
     Additionally, more than one motor can be used to provide the load required for launch. Through modularization, it is possible to use multiple motors to scale up the system to accept UAV&#39;s with greater weight or where increased power is required for higher launch velocities. 
     Use of one or more electric motors means that the acceleration achieved can be tightly controlled along the entire length of the power stroke without the need for complicated control valves and manifolds required on hydraulic/pneumatic systems. In pneumatic and pneumatic/hydraulic systems, the maximum acceleration typically occurs at the beginning of the launch because this is where the system pressure is at its maximum. As gas expands into the cylinder, the pressure drops and the force applied to the shuttle decreases. By contrast, a constant acceleration can be provided over the entire launch stroke utilizing the electric motor-driven tape described herein, because the motor RPM can increased throughout the stroke. The use of the DC motor in conjunction with the PLC to accurately control the launch profile is a unique to many of the above-described problems with commercially available launch systems. 
     The use of the tape  12 , which may be fabricated from nylon or some other synthetic material, offers a degree of cushioning during the initial application of the launch load since there is an inherent amount of stretch associated with this type of material. Most hydraulic/pneumatic systems connect the drive cylinder to the shuttle via a steel cable that does not have as much compliance or stretch during the application of the load and can exacerbate the g-load spikes seen. Use of a tape that has some cushioning, flexibility, stretchability or other features that allow a slight elongation and retraction of the material can be beneficial in the launching systems disclosed. It should be noted, however, that the stretch in the synthetic tape or belt is not required. Tapes or belts containing steel reinforcing fibers that would lesson or eliminate stretch may also be used. The use of a shuttle to tape interface allows the ability to control the acceleration by programmatically increasing the launch speed. This can be a prime contributor to eliminating the g-load spikes that occur with other systems. 
     The use of the Lithium Ion battery power source and electric motor as the drive mechanism can greatly reduce the overall system weight when judged against a comparable system containing the required hydraulic/pneumatic components (accumulator, pump, launch cylinder, gas bottle, reservoir, weight of hydraulic fluid, and so forth). It also allows for greater flexibility in the layout of the system and the ability to potentially modularize some of the subsystems. The components used may be smaller and do not require large tubes or pipes to route the pressured hydraulic fluid or gas. Power cables or flexible bus bars containing connectors can be used to route DC current from the battery to the motor. This will allow rapid replacement of a discharged battery unit. 
     It should be understood, however, that the battery need not be Lithium ion. Any other battery system capable of providing the required load and discharge rates may be used. Lithium Ion was chosen for an initial application due to its low weight and rapid discharge characteristics. It is expected, however, that other battery types and systems may be used in connection with this disclosure. 
     Since there are no pressure vessels utilized in this disclosure, the problem of gas or hydraulic leaks has been eliminated and the overall safety of the system has been enhanced. In many of the hydraulic/pneumatic systems, the cylinder and possibly the accumulator are attached to the rail. The accumulator is often piped over to a large gas bottle that serves as a reserve vessel to store pressured GN 2 . Due to the piping between the various hydraulic and pneumatic components, it can be difficult to allow the rail to move relative to the base if an adjustable launch angle is desired. By contrast, the ability to mount the drive motor  34  and payout reel assembly  36  to a base plate or pallet under the launcher rail  16  allows the rail to be unencumbered by excess weight and complexity. Utilizing a tape path that routes around the two end sheaves  46 ,  48  on the rail can allow the rail to be pivotable about an axis  62  to provide an adjustable launch angle. In an alternate embodiment, the drive pulley may be driven by the motor via a sprocket and chain. One example of this is shown in  FIG. 14A . 
     In most operational specifications, the deployment and tear down time of the launching system are critical parameters. The time to set-up the system, bring it to ready mode, perform a launch, and then reset the system for subsequent launches is crucial. Because there is no time associated with a pressurization cycle or spinning up a flywheel when using this battery/motor/tape combination, the time to energize the system, which involves charging up a set of capacitors to achieve a ready signal following system set-up, is minimal. The batteries can be sized to achieve a number of launches before recharging is required. In a specific embodiment, the batteries can be sized to allow four launches to be achieved prior to recharging or before battery replacement is required. More or fewer launches may be provided per charge, depending upon the size of the battery selected, the weight of the UAV to be launched, and the speed of the motor required. Additional battery packs could be charged separately and swapped out to continue operation in the field without waiting for on-board batteries to recharge. In one embodiment, quick disconnects may be provided to speed the battery change over process. A greater number of launches may be possible with a larger battery configuration, but this would impact system weight. The weight to launch cycles can be optimized based on the customer requirements. 
     In addition to the faster time to launch, the reset time for the disclosed system is faster because retraction of the shuttle does not require the movement of hydraulic fluid back into the reservoir typical of hydraulic/pneumatic launchers. To further enhance the reset time, the payout reel  36  could be motorized to retract the shuttle  14  back into the battery position  38 . 
     In the systems described, in one example, the operator&#39;s station may be wired, but remote from the launcher. In another example, the operator&#39;s station may be made wireless. The systems may be designed so that once set up with a UAV, they may be remote controlled. 
     Changes and modifications, additions and deletions may be made to the structures and methods recited above and shown in the drawings without departing from the scope or spirit of the invention and the following claims.

Technology Classification (CPC): 1