Abstract:
A system to launch and recover an Unmanned Aerial Vehicle (UAV) aircraft has a pole member attached to a deck of a ship. An arm member is attached to the pole member and extends away from the pole member in an approximately horizontal direction. The arm member is able to move rotationally and vertically on the pole member. An attachment mechanism is attached to a distal end of the arm member for holding and capturing the UAV aircraft. Momentum of the UAV aircraft causes the arm member to move rotationally around and vertically on the pole member when the UAV aircraft is coupled to the attachment mechanism.

Description:
BACKGROUND 
       [0001]    Embodiments of this disclosure relate generally to an unmanned aerial vehicle (UAV) aircraft, and more particularly, to a system and method for shipboard launch and recovery of a UAV aircraft that does not require a flight deck/runway. 
         [0002]    Presently, in order to launch and land a UAV aircraft from a ship, a flight deck is required. The flight deck is generally considered the upper level of an aircraft carrier where the aircraft take off and land. Alternatively, on smaller ships which do not have aviation as a primary mission, the landing area for helicopters and Vertical Take Off and Landing (VTOL) aircraft is also referred to as the flight deck. Thus, all UAV aircraft requires some type of flight deck for launch and recovery from a ship. 
         [0003]    For non high lift UAV aircraft, an aircraft catapult is needed to launch the UAV aircraft from the ship. An aircraft catapult consists of a track built into the flight deck. A shuttle device is attached to the track and to the UAV aircraft to be launched. In general, the shuttle is attached to the nose of the UAV aircraft. When the UAV is set to launch, a release bar holds the UAV aircraft in place as steam pressure builds up to a predetermined level. At this point, the release bar is unlatched freeing the shuttle to pull the UAV aircraft along the deck at high speed. The shuttle will pull the UAV aircraft in order to obtain sufficient velocity for takeoff. The aircraft catapult and flight deck results in added weight, less equipment space on the deck, and increased support cost of the ship. 
         [0004]    When landing a non high lift UAV aircraft on a ship, an arresting gear is generally used to decelerate the UAL aircraft as it lands. The arresting gear is generally used to decelerate the UAL aircraft as it lands. The arresting gear generally comprises a set of cables strung across the flight. The cables are attached to hydraulic cylinders. The hydraulic cylinders are connected to a pressure vessel via a special valve. When the UAV aircraft lands, the tailhook catches into one of the cable and pulls on the cable. The tension cased by the tailhook pulling on the cable compresses the hydraulic cylinders and pulls the UAV aircraft to a stop. For light weight UAV aircraft, a wire snare mounted on poles is generally used to catch the tailhook of the UAV aircraft. The arresting gear further adds weight and increases support cost of the ship. 
         [0005]    For all UAV aircraft, a landing gear and retraction system are required. Furthermore, for high lift UAV aircraft, high lift devices are required for launch and landing. Additional structure is needed on the UAV to allow for the high structural loads that occur due to catapult acceleration loads for launch and for high impact vertical and longitudinal forces on landing and the hook arrestment deceleration. The landing gear and retraction system, the high load structure for catapult and landing arrestment, and the high lift devices increase the cost and weight of the UAV aircraft. Furthermore, the landing gear and retraction system and the high lift devices require high strength flight deck structure for launch loads and deck impact on landing. This results in added weight and increased support cost of the ship. 
         [0006]    Therefore, it would be desirable to provide a system and method that overcomes the above problems. The system and method would allow for shipboard launch and recovery of a UAV aircraft without the use of flight deck/runway. 
       SUMMARY 
       [0007]    A system to launch and recover an Unmanned Aerial Vehicle (UAV) aircraft has a pole member attached to a deck of a ship. An arm member is attached to the pole member and extends away from the pole member in an approximately horizontal direction. The arm member is able to move rotationally and vertically on the pole member. An attachment mechanism is attached to a distal end of the arm member for holding and capturing the UAV aircraft. Momentum of the UAV aircraft causes the arm member to move rotationally around and vertically on the pole member when the UAV aircraft is coupled to the attachment mechanism. 
         [0008]    A method for launching an Unmanned Aerial Vehicle (UAV) aircraft comprises: attaching the UAV aircraft to an approximately horizontal arm member, the approximately horizontal arm moveably coupled to an approximately vertical pole member; moving the horizontal arm in a spiral direction on the approximately vertical pole member; and releasing the UAV aircraft from the approximately horizontal arm member when the UAV aircraft reaches launch airspeed. 
         [0009]    A method of recovering an Unmanned Aerial Vehicle (UAV) aircraft comprising: rotating an arm member on an approximately vertical pole member to a positioned approximately 90 degrees from a centerline of a deck, and at a top section of the approximately vertical pole member; capturing the UAV aircraft at a distal end of the arm member; and descending the arm member in a circular spiral down the vertical pole to reduce airspeed of the UAV aircraft. 
         [0010]    The features, functions, and advantages can be achieved independently in various embodiments of the disclosure or may be combined in yet other embodiments. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    Embodiments of the disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein: 
           [0012]      FIG. 1  is an elevated perspective view of a system for shipboard launch and recovery of a UAV aircraft; 
           [0013]      FIG. 2  is a magnified view of the vertical boom and horizontal arm of the system depicted in  FIG. 1 ; 
           [0014]      FIG. 3  is a side view of the system for shipboard launch and recovery of a UAV aircraft depicted in  FIG. 1 ; 
           [0015]      FIG. 4  is a side view depicting launching of a UAV aircraft using the system of  FIG. 1 ; 
           [0016]      FIG. 5  is an elevated perspective view of a capture assembly used with the UAV aircraft using the system of  FIG. 1 ; and 
           [0017]      FIG. 6  is a side view depicting recover of a UAV aircraft using the system of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    With reference now to  FIGS. 1-3 , a system  100  for shipboard launch and recovery of a UAV aircraft  102  is shown. The system  100  provides a means for launch and recovery of the UAV aircraft  102  without the need for flight deck or runway. The system  100  further eliminates a high strength structure required to withstand launch loads and deck impact on landing thereby reducing the weight and support cost of a ship launching and recovering the UAV aircraft  102 . The system  100  further reduces the structural weight of the UAV aircraft  102  by eliminating the need for a landing gear, a landing gear retraction system, and high lift devices for the UAV aircraft  102 . The system  100  offers expanded capabilities for UAV aircraft  102  operations, especially fixed wing UAV aircraft  102 , providing safe and reliable control in low visibility weather, day or night operations, and control during very rough sea conditions that cause large motions of the ship  106  during recovery operations. 
         [0019]    The system  100  has a pole member  108  coupled to a main deck  104  of a ship  106 . The pole member  108  extends up and away from the main deck  104  in an approximately vertical direction. The pole member  108  may be positioned anywhere on the main deck  104 . In  FIG. 1 , the pole member  108  is shown to be located in the aft section of the ship  106 . However, the pole member  108  may be located in other areas of the main deck  104 . 
         [0020]    In accordance with one embodiment, the pole member  108  may be retractable. In this embodiment, a bottom section of the pole member  108  may be coupled to a lift device  110 . The lift device  110 , such as a hydraulic lift or the like, is positioned on a lower deck of the ship  106  below the main deck  104 . An opening in the main deck  104  allows the lift device  110  to raise and lower the height of the pole member  108  above the main deck  104 . Alternatively, in accordance with another embodiment, the pole member  108  may a telescoping pole. Thus, different sections of the pole member  108  may be extended or retracted to adjust the height of the pole member  108 . In this embodiment, the pole member  108  may be attached to the main deck  104 . Alternatively, the pole member  108  would be attached to a lower deck and an opening in the main deck  104  would allow the different sections of the pole member  108  to be extended or retracted to raise and lower the height of the pole member  108  above the main deck  104 . The above are given as examples, and other devices/mechanisms may be used to raise and lower the height of the pole member  108  above the main deck  104  without departing from the spirit and scope. 
         [0021]    An arm member  112  is coupled to the pole member  108 . The arm member  112  will extend away from the pole member  108  in an approximately horizontal direction. The arm member  112  is coupled to the pole member  108  to allow the arm member  112  to rotate about the pole member  108  using the pole member  108  as a rotational axis as well as to allow the arm member  112  to move vertically up and down the pole member  108 . 
         [0022]    In accordance with one embodiment, in order to move the arm member  112  rotationally and vertically on the pole member  108 , a sleeve member  114  is inserted onto the pole member  108 . The sleeve member  114  is slidably and rotatably connected to the pole member  108 . The arm member  112  is attached to the sleeve member  114  and extends away from the sleeve member  114  in an approximately horizontal direction. The sleeve member  114  allows the arm member  112  to rotate around and move vertically up and down the pole member  108 . 
         [0023]    In accordance with another embodiment, a track  116  may be formed in the pole member  108  to aid the arm member  112  in moving rotationally and vertically on the pole member  108 . The track  116  will run spirally from a top section of the pole member  108  to a bottom section of the pole member  108 . The track  116  may be used in an embodiment where just the arm member  112  is coupled to the track  116  or alternatively in the embodiment having the sleeve member  114  wherein the sleeve member  114  is attached to the track  116 . In either embodiment, a roller device  118  may be used to move the arm member  112  or alternatively the sleeve member  114  along the track  116 . 
         [0024]    Attached to a distal end  112 A of the arm member  112  is an attachment device  120 . The attachment device  120  is used to secure the UAV aircraft  102  to the arm member  112  during takeoff of the UAV aircraft  102  and aid in capturing the UAV aircraft  102  during recovery of the UAV aircraft  102 . The attachment device  120  may be a clamping mechanism, a hook device, or the like. The listing of the different attachment devices  120  is given as examples and should not be seen in a limiting scope. 
         [0025]    Referring to  FIG. 5 , an elevated perspective view of UAV aircraft  102  is shown. The UAV aircraft  102  has a capture assembly  122 . The capture assembly  122  is used to secure the UAV aircraft  102  to the attachment device  120  so the main structure of the UAV aircraft  102  will not be damaged and further to aid in the attachment device  120  capturing the UAV aircraft  102  during recovery. The capture assembly  122  is generally located near the center of gravity of the aircraft. This provides for a more stability during launching and recovery of the UAV aircraft  102 . The capture assembly  122  is generally a retractable device which can be raised and lowered on the UAV aircraft  102 . In general, the capture assembly  122  is lowered when the UAV aircraft  102  is in flight to allow the UAV aircraft  102  to be more aerodynamic. 
         [0026]    In operation, because of the relationship between the arm member  112  and the pole member  108 , the pole member  108  should be located in an area of the main deck  104  where there is sufficient room to allow arm member  112  to rotate about pole member  108  as well as to move vertically along the pole member  108  in an unobstructed manner. In accordance with one embodiment, the pole member  108  is generally located along a centerline that runs from the bow to the stern of the ship. 
         [0027]    Referring to  FIG. 4 , launching of the UAV aircraft  102  using the system  100  will be described. Flight control of the UAV aircraft  102  such as adjusting the flight control surfaces and adjusting airspeed during the launch and flight of the UAV aircraft  102  may be accomplished remotely or programmed into the control system of the UAV aircraft  102 . 
         [0028]    Prior to launching the UAV aircraft  102 , the UAV aircraft  102  is moved to a location on the main deck  104  that is 90 degrees to the centerline of the main deck  104  and is perpendicular to the arm member  112  of the system  100 . The UAV aircraft  102  is attached to the arm member  112  by securing the attachment device  120  of the arm member  112  to the capture assembly  122  on the UAV aircraft  102 . The propulsion system of the UAV aircraft  102  is activated and maximum power is commanded. 
         [0029]    Upon launch, the horizontal arm member  112  is free to move about the pole member  108 . The horizontal arm member  112  will generally move in an upward spiral direction on the pole member  108 . As stated before, a track  116  may be formed in the pole member  108  to aid the arm member  112  in moving spirally on the pole member  108 . 
         [0030]    The UAV aircraft  102  accelerates along the circular spiral path, ascending upward while tethered to the attachment device  120  of the arm member  112  via the capture assembly  122  on the UAV aircraft  102 . By adjusting the flight control surfaces of the UAV aircraft  102 , the attitude of the UAV aircraft  102  is changed such that the load at the capture assembly  122  is normal to the plane containing the wing axis and the fuselage axis (i.e. the x-y plane), and the load on the arm member  112  is primarily along the axis of the arm. This is done by maintaining the bank angle of the UAV aircraft  102  to the required schedule pattern using the control surfaces of the UAV aircraft  102 . The angle of attack of the UAV aircraft  102  is maintained at a value needed for minimum drag during the spiral ascent. The angle of attack then is commanded to change to sustain the launch airspeed at release from the arm member  112 . The release point will be parallel to the forward velocity track of the ship  106 , thus taking advantage of the relative higher airspeed at the release point. After reaching the launch airspeed (approximately 130 kts) and the capture assembly  122  on the UAV aircraft  102  is releases from the attachment device  120  of the arm member  112 . The UAV aircraft  102  is commanded to roll to wings level, and to maintain 1 g level flight or a desired climb-out flight path. 
         [0031]    Referring to  FIG. 6 , recovery of the UAV aircraft  102  using the system  100  will be described. Again, flight control of the UAV aircraft  102  such as adjusting the flight control surfaces and adjusting airspeed during the recovery of the UAV aircraft  102  may be accomplished remotely or programmed into the control system of the UAV aircraft  102 . 
         [0032]    When returning to the ship  106 , the UAV aircraft  102  is commanded to fly a special landing approach trajectory behind the ship  106 . The flight path is designed to remove energy from the UAV aircraft  102  prior to the landing so as to permit a pickup by the arm member  112  of the system  100 . Prior to the landing, the arm member  112  is positioned 90 degrees from the centerline of the main deck  104 , and at the top of the pole member  108 . The attachment device  120  of the arm member  112  is set to capture the capture assembly  122  on the UAV aircraft  102 . 
         [0033]    To reduce the energy of the UAV aircraft  102  for landing, the UAV aircraft  102  is slowed to airspeed well below cruise airspeed at the hook capture point. This is accomplished by commanding the UAV aircraft  102  to fly an approach path of approximately a negative 3 degrees glide slope behind the ship  106 , reaching a minimum altitude of 25 feet, and then commanding a sharp flare pull-up while commanding idle thrust. This will give a climb with a rapid decrease in airspeed, but still with sufficient airspeed for precision flight path control. The flight path of the UAV aircraft  102  is positioned to intersect the target for capture by the arm member  112  at airspeed between 40 kts to 30 kts. Since the ship  106  is also moving at approximately 30 knots, there will be a reasonable capture window. Motion of the arm member  112  and pole member  108  can occur during the landing approach due to ship motion heave and sway. This motion is compensated by flight path corrections from the control system of the UAV aircraft  102 , resulting in synchronous motion of the flight path with the attachment device  120  of the arm member  112  during the final portion of the approach. 
         [0034]    As the UAV aircraft  102  nears the arm member  112 , a visual sensor  124  on the UAV aircraft  102  is activated to monitor and update the relative position of the capture assembly  122  to the attachment device  120  of the arm member  112 . The capture assembly  122  on the UAV aircraft  102  is extended upward on a pivot boom  122 A so that any contact of the pivot boom  122 A by the attachment device  120  of the arm member  112  will result in capture of the UAV aircraft  102 . This allows for a greater capture. The capture area is the target area that is required to be met by the UAV flight path control. The target area is within the flight path guidance capability of the UAV aircraft  102  using either shipboard radar to measure the position and velocity of the UAV aircraft  102 , and with data link steering commands sent back to the UAV aircraft  102 . Another method is to use Differential GPS positioning and velocity data obtained from the sensors on the UAV aircraft  102  and on the ship  106 . 
         [0035]    The arm member  112  is free to pivot after the hook capture, resulting in a descending circular spiral with the control surfaces extended combined with braking action from the arm member  112  to reduce airspeed to acceptable levels as the UAV aircraft  102  descends to a stop at the main deck  104 . The attachment device  120  of the arm member has a damper device to absorb the capture loads. The damper device is adjustable for the size or gross weight of the UAV aircraft  102 . 
         [0036]    The system  100  offers expanded capabilities for UAV aircraft  102  operations, especially fixed wing UAV aircraft  102 , providing safe and reliable control in low visibility weather, day or night operations, and control during very rough sea conditions that cause large motions of the ship  106  during recovery operations. With the system  100 , shipboard launch and recovery operations can be equivalent to current CVA operations of manned aircraft. The system  100  replaces the large landing deck surface and the shipboard operator that would send guidance commands to the UAV aircraft  102  during the final approach, a task that is extremely difficult in landings in high seas and in low visibility conditions. Moreover, using the system  100  eliminates the need for landing gear, flaps, and other high lift devices on the UAV. Use of low speed airborne capture reduces the structure required for landing deck impact and eliminates the large horizontal loads for catapult launch and for hook capture of a deck cable upon landing. These factors will significantly reduce the weight and cost, and increase reliability and mission capability of the UAV aircraft  102 . 
         [0037]    While embodiments of the disclosure have been described in terms of various specific embodiments, those skilled in the art will recognize that the embodiments of the disclosure can be practiced with modifications within the spirit and scope of the claims.