Abstract:
An unmanned aerial system (UAS) is described that is operable on or in water, in addition to being able to fly in the air. The UAS can float in a body of water, or submerge itself underneath the water, and then later launch from the water without human intervention to perform a flying mission. The UAS can then return back to the water. The UAS incorporates an electric ducted fan acting as the propulsion engine for the UAS in the water as well as in the air.

Description:
FIELD 
     This disclosure relates an unmanned aerial system (UAS) that is operable in both air and in water. 
     BACKGROUND 
     In recent years, monitoring of global waterways has become increasingly important. Vehicles that are less conspicuous are often times useful for such monitoring. For example, some small unmanned aerial vehicles (UAVs) are useful for intelligence gathering, surveillance and reconnaissance roles in certain waterways. Conventional UAV&#39;s fly in the air and can contain various sensors that perform sensing operations. However, the endurance of UAV&#39;s is typically limited, which limits the use of UAV&#39;s on global waterways where the distances to be covered are immense, unless a tending ship from which the UAV is launched is present or the UAV is monitoring a waterway close to land. 
     SUMMARY 
     An unmanned aerial system (UAS) is described that is operable on or in water, in addition to being able to fly in the air. The UAS can float in a body of water, or submerge itself underneath the water, and then later launch from the water without human intervention to perform a flying mission. Upon completion of the mission, the UAS can then return to the water. 
     Submerging the UAS under the water allows the UAS to be hidden from view while waiting to perform its mission. When the UAS returns to the water, the UAS can recharge its power, for example using solar panels mounted on the aircraft, or if sufficient power remains, relaunch to perform another mission. Alternatively, the UAS can be allowed to sink to the bottom, essentially making the UAS disposable. 
     The UAS uses an engine that works effectively in both air and water, as well as in other fluids. For example, the engine can be an electric ducted fan. When disposed in water, the electric ducted fan engine will intake and expel water like a pump, driving the UAS through the water. To launch into the air, the UAS broaches the water&#39;s surface a sufficient distance to allow time for the engine to empty of water and speed up to allow rapid passage of air, thereby creating sufficient thrust for airborne flight. 
     In one embodiment, a method of operating an unmanned aerial system includes providing an unmanned aircraft with a fuselage, wings, and a ducted fan engine for propulsion. The unmanned aircraft, which can either float or be designed to sink, is disposed in water and the ducted fan engine is used to propel the unmanned aircraft in the water. The unmanned aircraft is then launched from the water and the ducted fan engine is used to propel the unmanned aircraft to fly through the air. 
    
    
     
       DRAWINGS 
         FIG. 1  is a perspective view of the submersible UAS. 
         FIG. 2  is a front view of the submersible UAS. 
         FIG. 3  is a rear view of the submersible UAS. 
         FIG. 4  is a schematic depiction of the submersible UAS submerged beneath the water, floating on the water, and launching from the water for flight in the air. 
     
    
    
     DETAILED DESCRIPTION 
     With reference to  FIG. 1 , a UAS  10  is illustrated as including a fuselage  12  and wings  14   a ,  14   b . The fuselage  12  and wings  14   a ,  14   b  can be made of any materials used for UAV-type vehicles, including composite materials, for example carbon fiber composite, with a water-proof coating applied to the fuselage and wings if necessary to enable the materials to withstand exposure to water including salt water. Polyaramid can be added to certain areas for abrasion resistance and impact resistance or in the event of a crack in the composite structure to prevent catastrophic failure. These elements can be woven into a single cloth and then covered with a thin layer of E-glass yarn and matrix to prevent wicking of water into the substrate. Alternatively, a silicon conformal coating could be applied over the entire water exposed surfaces of the UAS. 
     The UAS  10  can be constructed so that it is buoyant and floats on the surface of the water, or constructed to submerge itself underneath the water. 
     The fuselage  12  is generally cylindrical in shape, with the diameter of the fuselage at a fluid intake end  20  being smaller than the diameter of the fuselage at a fluid discharge end  22 . The UAS  10  generally resembles a MiG-15 jet fighter or a MiG-17 jet fighter in construction. 
     With reference to  FIGS. 1-2 , the wings  14   a ,  14   b  are attached to the fuselage  12  at root ends  24   a ,  24   b . As shown in  FIG. 2 , the wings  14   a ,  14   b  in the illustrated embodiment have negative dihedral or anhedral. The wings also have a slight washout or twist from the root to the tip. 
     The wings  14   a ,  14   b  include leading edges  26   a ,  26   b , trailing edges  28   a ,  28   b , top surfaces  30   a ,  30   b , and bottom surfaces  32   a ,  32   b , respectively. In the illustrated embodiment, the wings also include wing fences  34 , flaps  36 , or any other control surfaces to facilitate water launching, water landing, steering in water, and flight attributes of the UAS  10 . A T-tail  38  extends upwardly from the fuselage  12  near the rear thereof, which includes a vertical stabilizer portion  39   a  and a pair of horizontal stabilizer portions  39   b  extending from the vertical stabilizer portion  39   a . If desired, the T-tail  38  can be provided with flaps  25  (illustrated in dashed lines) on either or both of the vertical stabilizer portion  39   a  and the horizontal stabilizer portions  39   b  to assist in directional control of the UAS  10  in the water and during flight. 
     Mounted in the fuselage  12  is a propulsion engine in the form of an electric ducted fan engine  40 . The engine  40  is mounted axially in the fuselage  12  with the intake end at the fluid intake end  20  of the fuselage and discharges fluid toward and out the discharge end  22  at the rear of the fuselage. 
     The engine  40  includes an axial duct through which fluid flows, an impeller  42  or fan at the front end of the duct for drawing fluid into the duct and discharging the fluid toward the rear of the duct. Guide vanes  44  (visible in  FIG. 3 ) disposed adjacent the rear of the duct de-swirl the fluid into a smoother axial flow before the fluid is discharged through the discharge end  22 . The ducted fan engine  40  is driven by an electric motor (not shown) powered by one or more sources of electricity, such as a battery mounted in the UAS. A generally similar electric ducted fan engine is sold under the name Flurry 100™ available from Xcelaero Corporation of San Luis Obispo, Calif., or described in US 2008/0219836. 
     The UAS  10  also has a communication component  50  that is configured to provide communications to and from the UAS. In the illustrated embodiment the component  50  is mounted in the fuselage  12 . However, the communication component  50  can be mounted at any location on or in the UAS  10 , for example on or within the fuselage  12  or wings, to protect it from water. The communication component may be any device for transmitting and/or receiving data, for example, a transceiver, a transmitter, a transponder, etc. The communication component can be designed for wireless communication, such as infrared or radio frequency, including satellite communications. The communication component  50  can permit the UAS  10  to communicate with any remote location, for example a ship, another aircraft, or a land based location. 
     The UAS  10  also has a sensing system  60  for collecting data pertaining to its surroundings. In the illustrated embodiment, the sensing system  60  is mounted under a clear canopy  62  at the top of the fuselage  12  which protects the sensing system  60  from exposure to water and environmental conditions, while allowing the sensing system to sense outside of the UAS  10 . However, the sensing system  60  can be disposed at any location(s) enabling the sensing system to perform it sensing function(s). The sensing system  60  can include one or more devices for detecting signals, sounds, light, acoustic contacts, etc., identifying location, measuring altitude, speed, bearing, damage, etc. and/or taking sound, chemical etc. samples of the surroundings. The sensing system  60  can also include one or more cameras for taking images. The sensing system  60  is connected to the communication component  50  so that the data gathered by the sensing system may be transmitted externally of the UAS. The UAS  10  can also include data storage capability so that the UAS stores gathered data which can be transmitted by the communication component or physically retrieved from the UAS. 
     The UAS  10  can include a location-determining device, for example a global positioning system (GPS), so that the UAS can relay its location via the communication component. 
     The UAS  10  also includes a control unit with a processor and memory storage. The memory storage can include programmable instructions for a monitoring mission of the UAS and control programs for controlling the operation of the UAS. 
     To protect components, for example the communication component and the sensing system, from water damage, the components can be encased in a suitable material, for example silicon elastomer. 
     In one exemplary use of the UAS  10  illustrated in  FIG. 4 , the UAS  10  flies to a waterway  100  and lands on the water. The UAS  10  then either floats or, for increased stealth, submerges itself in the water. The control surfaces of the UAS, for example the flaps  36 , can be used to help achieve submersion as well as provide directional control in the water. Alternatively, the weight of the UAS  10  can be such that the UAS automatically submerges, at which point the UAS sinks to the bottom or remains submerged under the water using the propulsion from the engine  40  together with directional control (up, down, left and right) provided by the control surfaces. 
     While in the water, the UAS  10  can remain stationary to conserve power, or the electric ducted fan engine can be operated to propel the unmanned aircraft in the water. When the engine  40  is operated, water is drawn by the impeller  42  through the intake end  20  and discharged toward the rear and out through the discharge end  22 . The discharge of the water propels the UAS  10  through the water. 
     When it is desired to launch the UAS  10  into the air, the UAS is accelerated underwater, and then directed generally straight up to eject the UAS clear of the water a sufficient distance to clear the engine of water and allow the engine rpm increase that will produce adequate thrust to propel the UAS and produce lift. The UAS can be provided with means to break water surface tension and at the same time reduce drag. 
     Once the water is expelled from the engine, the engine will speed up to an appropriate air-throughput since it is acting on the lower viscosity air, thereby creating thrust for flight. The engine will then act as the propulsion unit for achieving and maintaining flight. While flying, the UAS  10  can perform a sensing function, and communicate sensed information to a remote location and/or store sensed information internally. 
     When the mission is complete, the UAS  10  then returns back to the water where it floats or submerges itself. The UAS can recharge its power, for example using solar panels mounted on the wings and/or the fuselage or by other suitable electrical generation means, or if sufficient power remains, perform another mission. Alternatively, if the UAS is no longer needed, the UAS can be allowed to sink to the bottom, essentially making the UAS disposable. 
     The embodiments disclosed in this application are to be considered in all respects as illustrative and not limitative. The scope of the invention is indicated by the appended claims rather than by the foregoing description; and all changes which come within the meaning and range of equivalency of the claims are intended to be embraced therein.