Long-range reconnaissance pod

Abstract

The long-range reconnaissance pod comprises a cylindrical fuselage and a hollow enclosure forward of the fuselage, the hollow enclosure housing an optical sensor configured to image an area of ​​interest during a long-range reconnaissance mission; a casing of the forward hollow enclosure comprising a target-facing section and a target-facing section, both extending to the leading edge of the pod; an optical window adapted to protect the optical sensor from external flows, fixed to the target-facing section; and both sections configured with an external aerodynamic design that renders the optical window substantially optically distortion-free. TIFF2025542225000002.tif102128

Description

[Technical Field]

[0001] FIELD OF THE INVENTION The present invention relates to the field of aerial reconnaissance systems, and more particularly to long-range reconnaissance pods. [Background technology]

[0002] Background of the Invention Reconnaissance missions carried out by aircraft for short-term intelligence gathering, such as observation of specific structures and areas and enemy troop movements, are of great military importance and help troops avoid being surprised by unfavourable terrain conditions or by unexpected enemy forces.

[0003] To reduce risk to the aircraft carrying the reconnaissance system's optics for acquiring images of the desired area of ​​interest, the aircraft should preferably be located at an altitude of at least 15 km and a distance of at least 300 km from the target, and fly at a maximum speed of Mach 1.4. For such long-range photography, the optics must have a sufficiently high resolution, e.g., 1 arc second, to accurately distinguish the target from its surrounding environment.

[0004] Many reconnaissance systems are housed in pods attached to the underside of aircraft wings. These pods contain one or more optical windows through which optical elements can acquire images of targets. However, at the transonic speeds typical of reconnaissance aircraft, shock waves, separated turbulent shear layers, or thick turbulent boundary layers occur. These flow structures obstruct the passage of the optical radiation needed for the optical elements, thereby significantly reducing the resolution of the acquired image.

[0005] The objective of the present invention is to ensure high resolution of images acquired by long-range reconnaissance pods by reducing losses induced by turbulence and shock wave related phenomena when the coupled aircraft are flying at transonic or supersonic speeds.

[0006] Other objects and advantages of the present invention will become apparent as the description proceeds. Summary of the Invention

[0007] The long-range reconnaissance pod comprises a cylindrical fuselage and a hollow enclosure forward of the fuselage housing an optical sensor configured to image an area of ​​interest during a long-range reconnaissance mission, the casing of the forward hollow enclosure having two sides, a first side being a target-facing section and a second side being an away-from-target section, both extending to a leading edge of the pod. As used herein, the terms target-facing and away-from-target refer to sections that can be oriented toward a target and have a side facing toward the target and a side facing away from the target, i.e., the target-facing section and the away-from-target section.

[0008] The hollow enclosure further comprises an optical window fitted in the target-facing section and adapted to protect the optical sensor from external flows, both sections being designed and constructed with an external aerodynamic design that leaves the optical window substantially optically distortion-free.

[0009] The aerodynamic design of the pod either prevents the appearance of flow structures that create optical distortions, such as shock waves, separated shear layers, and thick turbulent boundary layers, especially at its leading edge, or restricts them to regions away from the line of sight of the operational envelope. Flow-induced optical distortions are accordingly avoided or at least minimized to an acceptable level.

[0010] The external aerodynamic design, which defines the section facing away from the target, ensures that flow separation is avoided and also ensures smooth flight characteristics of the pod in the presence of shock waves and compressible effects, which are desired during reconnaissance operations to enable the optical sensors housed within the pod's hollow enclosure to take high-quality photographs.

[0011] In one aspect, the target-facing section and the anti-target-facing section are integrally formed together into a non-cylindrical casing portion, and such an integral casing can be manufactured by methods known in the art, such as, but not limited to, injection molding, pressing, 3D printing, or casting.

[0012] In one aspect, the optical window is planar, the section facing the target includes a window perimeter plate that supports and is coplanar with the optical window, and the section facing away from the target includes a surface that is inclined relative to the window perimeter plate at an angle small enough to prevent flow separation or ensure that shock waves do not localize to the optical window.

[0013] The optical window is located far enough from the leading edge of the turret that any shock waves that may occur will occur in front of the optical window (not across the window). The upstream forward portion of the optical window must be at least 0.6D from the pod leading edge, where D is the pod diameter.

[0014] In one aspect, the hollow enclosure is a hollow turret rotatable about the cylindrical body.

[0015] In one aspect, the radius of curvature of the leading edge is less than or equal to the diameter of the cylindrical fuselage multiplied by a factor of 0.09. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a perspective view of a long-range reconnaissance pod according to one embodiment shown in a position suitable for imaging. [Figure 2] 2 is another perspective view of the pod of FIG. 1 showing the section facing away from the target. [Figure 3] 2 is another perspective view of the pod of FIG. 1 showing the target-facing section. [Figure 4] 2 is a high-fidelity simulation of a cross-section of a portion of the pod of FIG. 1 including an optical window, illustrating the distortion-free area in front of the optical window. [Figure 5] FIG. 2 is a side view of the pod of FIG. 1. [Figure 6] FIG. 2 is a bottom view of the pod of FIG. 1. [Figure 7] 7A-7C show side views of the pod of FIG. 1 with the turret shown in cutaway, showing the optical sensor respectively set at three different angular positions. DETAILED DESCRIPTION OF THE INVENTION

[0017] Detailed Description of the Invention Target imaging performed using an aerial reconnaissance pod requires long-range photography to minimize risk to the aircraft on which the pod is mounted, so accurate observation of the target is contingent on high-resolution imaging. As referred to herein, the term "target" is interchangeable with "area of ​​interest."

[0018] The present invention is directed to reconnaissance missions using Long Range Oblique Photography (LOROP) cameras, which employ long focal length optics to capture high-resolution oblique images of distant objects despite atmospheric attenuation. Targets to be imaged are located at large angles to the sides of the aircraft, ensuring safe standoff flight. The LOROP camera is configured to be mounted within a pod. Optical windows that protect the camera from flow interaction are typically planar and mounted on one side of the pod. As referred to herein, "long range" refers to distances greater than 50 km from the area of ​​interest, necessitating a camera with high resolution requirements.

[0019] LOROP reconnaissance missions differ from invasive missions, during which the aircraft carrying the cameras fly at relatively low altitudes and are therefore at risk of being attacked. Because the altitudes of invasive missions are relatively low, the cameras often take relatively low-resolution images, and the optical windows of the pods on which cameras for invasive missions are mounted are often large and narrow.

[0020] Applicant desires to place an optical window at the forward end of the LOROP camera mounting pod to minimize flow-induced aberrations as much as possible, thereby avoiding the creation of a thick turbulent boundary layer over the window. While forward-looking observations result in negligible shockwave-induced aberrations, this practice is not suitable for LOROP reporting, where observations are made transverse to the direction of flight. The forward-facing window is immune to boundary layer-related aberrations due to the stagnation region. Side windows, on the other hand, experience turbulent boundary layers, which create optical aberrations unless properly handled.

[0021] Despite the potential benefits of forward optical windows, such windows are subject to atmospheric optical aberrations due to their proximity to the airflow over the pod. One source of optical aberrations is turbulence in the boundary and shear layers of the airflow over the optical window. The light beam captured by the camera passes through the turbulence and is diffused, resulting in blurred images. Flow separation occurring in front of or above the optical window creates highly turbulent shear layers that exacerbate the effects of blurring due to optical aberrations. Shock waves and supersonic flow pockets over the optical window can induce beam deflections, often known as pointing errors.

[0022] It has been found that these optical aberrations can be mitigated or completely eliminated by properly configuring the pod so that the optical window is optically undistorted or nearly undistorted by minimizing the disruptive effects of flow on the window.

[0023] FIG. 1 illustrates a long-range reconnaissance pod 10 according to one embodiment. The pod 10 has a stationary cylindrical fuselage 5 configured with a plurality of mounting elements 4 used to attach the cylindrical fuselage 5 to an aircraft fuselage or wing, so that the longitudinal pod axis is parallel to the aircraft axis. Rotatably mounted to the forward end of the cylindrical fuselage 5 is a turret 7 having a hollow interior within which an optical sensor, such as a LOROP camera for use in long-range reconnaissance missions, is housed, along with electronic and electromechanical components necessary for its proper operation. The hollow interior is lined with an optical window 8 made of a material optically transparent to the wavelength of radiation to be detected by the optical sensor, such as zinc sulfide, zinc selenide, sapphire, or spinel. Turret 7 is rotatably driven about the pod axis by a rotary drive assembly (not shown) mounted within fuselage 5, which allows angular displacement of up to 360 degrees in either direction of rotation, so that optical window 8 can be set to one of two possible target-facing positions, illustratively allowing targets located on one of the aircraft's lateral faces to be imaged by the sideward target-facing optical sensor, thereby facilitating the use of a LOROP camera. Mounting element 4 is attached to a suitable aircraft area that ensures turret 7 can project forward therefrom and rotate without interference.

[0024] Other views of the pod 10 are illustrated in FIGS.

[0025] As shown in FIGS. 2 and 5, the turret 7 is comprised of an aft cylindrical casing section 11 and a forward non-cylindrical casing section 13. The aft cylindrical casing section 11 has an outer diameter slightly larger than that of the cylindrical fuselage 5, allowing the turret 7 to rotate around the fuselage 5. The forward casing component 13 is designed to minimize aerodynamic disturbances while maintaining an internal volume large enough to accommodate the necessary optical, imaging, and supporting mechanical devices. As described below, the non-cylindrical casing section 13 is comprised of two distinct sections: a first section, a "target-facing section," which contains optical windows generally positioned appropriately to acquire images of a selected target; and a second section, a "non-target-facing section," i.e., facing away from the target. These two sections are part of a rotatable turret 7 and their relative positions are expected to change constantly, but the target-facing section and the target-facing section represent the relative positions that the corresponding sections are intended to occupy when a selected target is being imaged.

[0026] The target-facing section 20 is shown in FIG. 3, with the optical window removed for clarity to illustrate the hollow interior 28 of the turret 7 and the various components housed therein. The target-facing section 20 is comprised of a planar optical window and a window perimeter plate 17 that is flush with and provides support for the optical window. While the boundary 19 of the opening for the optical window is shown as elliptical, other shapes are within the scope of the invention as long as its surface area is large enough to provide an uninterrupted field of view throughout the entire range of travel of the optical sensor 22. To prevent obstruction of the field of view of the optical sensor 22, recessed areas 9a-c, contiguous with the boundary 19, are formed in the cylindrical wall of the casing portion 11.

[0027] The window surround plate 17 is flush with the leading edge 16 of the turret 7 and flush with the optical window to prevent the generation of shock waves or localized flow separation, minimizing localized acceleration and subsequent shock wave generation under transonic flight conditions and avoiding localized flow separation. The transition region between the leading edge 16 and the plate 17 is formed with a fillet 27 or other type of rounded edge. The fillet 27 extends from the leading edge 14 to a thinned portion 18 of the cylindrical turret section 11 that projects obliquely from the leading edge 14 to provide a smooth transition. The leading edge 16 also extends to the intersection between the leading edge 14 and the oblique portion 18.

[0028] 2, 4 and 5, the section 25 facing away from the target is comprised of a curved surface 12 which extends forward from the forward edge 14 of the cylindrical portion 11 to the laterally rounded leading edge 16 of the turret, the latter extending circumferentially between diametrically opposed regions of the cylindrical portion 11. Surface 12 is shown in FIG. 2 as being divided into two portions merely as a schematic means of illustrating its curved profile.

[0029] The slope and curvature of surface 12 relative to window surround plate 17 are carefully designed to minimize flow separation and shock wave generation over the optical window throughout the operational envelope defined by angle of attack, Mach number, and flight altitude. For example, at Mach numbers of 0.8, altitudes of 30,000 feet, and angles of attack of 5 degrees or less, flow-induced disturbances over the optical window are negligible.

[0030] The presence of the curved surface 12 also reduces shock wave generation, ensuring that shock waves do not localize at the optical window. The inventors have discovered that a distance of at least 0.6D aft from the leading edge 16 of the turret 7, where D is the diameter of the fuselage 5, ensures that the optical window is free from shock waves, where D is referred to as the geometric scale. The 0.6D distance was found empirically and is not universal; it is highly dependent on the configuration and flight envelope. This distance ensures that leading edge acceleration-related supersonic pockets and shock waves are located only forward of the optical window and therefore do not induce optical aberrations.

[0031] The rounded leading edge 16 configuration also aids in shock wave conditioning by ensuring a stable shock wave when the radius of curvature of the leading edge 16 is less than or equal to 0.18*D / 2, where D is the diameter of the fuselage 5. A larger radius of curvature induces a larger acceleration, which in turn induces a larger supersonic pocket on the optical window and a stronger shock wave. Again, D is used only as a geometric scale. The radius of curvature limit was found empirically and is not universal, being highly dependent on the configuration and flight envelope.

[0032] Figure 4 illustrates the simulated expansion contours appearing in a cross section of the flow field across the optical window 8. The expansion is a good measure for illustrating flow compressibility. The refractive index is linearly dependent on the flow density, and therefore significant variations in flow compressibility across the optical window induce optical aberrations. These results were obtained numerically at transonic speeds, e.g., Mach number 0.8. When a shock wave 42 is generated forward relative to the leading edge 16, the optical window 8 is shown to be undistorted with respect to flow separation and shock wave formation.

[0033] 3, 6 and 7, turret interior 28 is defined by a turret casing having a rear cylindrical casing portion and a front non-cylindrical casing portion, a wall 31 located at one longitudinal end in a mid-region of cylindrical casing portion 11, and a wall 34 at the other longitudinal end extending laterally between inclined surface 12 and window surround plate 17 in a region relatively close to leading edge 16. An end of a rotary drive assembly for controlling turret rotation may be connected to wall 31.

[0034] A gimbaled frame 37, which may be a rectangular, open-centered frame, is connected to the interior of the turret casing, and the disk 39 is pivotally supported on the gimbaled frame 37 by two diametrically opposed bearings 33a and 33b that define a pivot axis. The optical sensor 22 protruding from the gimbaled disk 39 faces the optical window and is very slightly spaced from the optical window in all angular positions of the disk shown in Figures 7A-7C to ensure good optical performance when covering the optical window opening.

[0035] Although the description is in terms of a single optical sensor, it will be understood that multiple optical sensors, whether identical or different, may similarly protrude from the disk 39. The multiple optical sensors may operate independently or in unison.

[0036] A pin (not shown) that passes through and is connected to disk 39 is rotatably mounted in bearings 33a and 33b. A motor attached to gimbal frame 37 controllably drives the pin so that optical sensor 22 is oriented as desired to increase its field of view. Disk 39 may also be pivotally mounted in other ways to define additional pivot axes, such as being pivotally mounted to an inner gimbal frame that is movably connected to outer frame 37 so that the disk is provided with three degrees of freedom.

[0037] Control circuitry for controllably repositioning disk 39 may be mounted on gimbal frame 37, and interconnecting wiring may be incorporated into one or more of its surfaces. The control circuitry may also be operable to controllably operate optical sensor 22 and controllably rotate turret 7.

[0038] The reconnaissance system, including the control circuitry, may be configured to operate in either automatic mode or manual mode, or a combination of automatic and manual modes during the same mission. In automatic mode, the reconnaissance system is configured to command the optical sensor 22 to automatically acquire images of pre-planned targets. Based on the mission plan, the reconnaissance system in automatic mode automatically activates one or more selected sensors as the aircraft approaches the target, rotates the turret according to the aircraft's instantaneous orientation, controls the relative orientation of the selected sensors, and begins or ends the recording and transmission of image data. Missions may be pre-planned at a ground station and then uploaded to the reconnaissance system processor before the mission. Alternatively, the mission plan may be automatically changed while the aircraft is in flight in response to the transmitted data. In manual mode, the operator can manually change the mission plan during flight. The operator may also interrupt automatic operation and manually perform reconnaissance functions.

[0039] It will be appreciated that if the pod is configured with a section facing the same target and a section facing away from the target, but without a rotatable turret and the section facing away from the target is set into the airflow, the optical window can also be optically distortion-free or nearly distortion-free.

[0040] While several aspects of the invention have been described by way of example, it will be apparent that the invention can be practiced with many modifications, variations and adaptations, as well as with numerous equivalents or alternative solutions that are within the scope of those skilled in the art, without going beyond the scope of the claims.

Claims

1. 1. A long-range reconnaissance pod comprising: a cylindrical fuselage; and a hollow enclosure forward of the fuselage containing an optical sensor configured to image an area of ​​interest during a long-range reconnaissance mission, the front hollow enclosure casing comprising: a target-facing section and an anti-target-facing section, both of which extend to the leading edge of the pod; Equipped with an optical window adapted to protect the optical sensor from external flows is fixed to the section facing the target, and both sections are configured with an external aerodynamic design that renders the optical window substantially optically distortion-free; Long-range reconnaissance pod.

2. The pod of claim 1 , wherein the external aerodynamic design, whereby the section facing away from the target is configured, ensures that flow separation is avoided.

3. 10. The pod of claim 1, wherein the external aerodynamic design, whereby the section facing away from the target is defined, ensures smooth flight characteristics of the pod in the presence of shock waves and compressible effects.

4. 10. The pod of claim 1, wherein the target-facing section and the anti-target-facing section are integrally formed together in a non-cylindrical casing portion.

5. the optical window is planar; the target-facing section a window perimeter plate that supports the optical window and is flush with the optical window; The pod of claim 1 , comprising:

6. a section facing away from the target, a surface inclined relative to the window perimeter plate at an angle small enough to prevent flow separation or ensure that shock waves are not localized at the optical window; 6. The pod of claim 5, comprising:

7. 7. The pod of claim 6, wherein the optical window is guaranteed not to be exposed to shock waves when it is at least a distance aft of the leading edge equal to the product of the diameter of the cylindrical body and a factor of 0.

6.

8. The pod of claim 1 , wherein the hollow enclosure is a hollow turret rotatable about the cylindrical body.

9. The pod of claim 1 , wherein the radius of curvature of the leading edge is less than or equal to 0.18*D / 2, where D is the diameter of the cylindrical body.

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