Patent Application
20050211827
1) Field of the Invention
The present invention relates to missiles and, more particularly, to a high speed missile including an oblique missile wing, as well as an associated system and method.
2) Description of Related Art
It is well known that wing design plays an instrumental role in increasing the lift to drag ratio (L/D) during flight. Wing design becomes especially important depending on whether the wing is subjected to subsonic, transonic, or supersonic speeds. Subsonic speeds generally occur at speeds of about less than about Mach 0.8, transonic speeds occur generally at speeds of about Mach 0.8 to 1.2, and supersonic speeds occur at speeds of about Mach 1.2 to 5.0. Thus, wings subjected to transonic speeds may experience speeds just below the speed of sound, but also experience flow fields having regions of locally subsonic and supersonic velocities. As a result, a critical velocity is reached during transonic speed when the air flowing over the wing has reached the speed of sound (Mach 1.0) at some point along the airfoil. At transonic and supersonic speeds there is a substantial increase in drag due to changes in pressure distribution, but once the speed increases past transonic, the drag decreases, and less thrust is required to fly at supersonic speed than at transonic speed.
Decreasing drag involves balancing several different parameters, including, for example, wing geometry, overall wing dimensions, and the profile of the airfoil. High speed missiles have typically used swept back wings to achieve acceptable drag at transonic speeds. This may result in a mechanically complex design, however, since most missile applications require that the wings be folded when the vehicle is to be carried by a military aircraft. A conventional swept wing design requires that both the left and right wings be separately folded back, each with its own pivot and locking mechanism.
Furthermore, although a conventional swept wing does reduce drag at transonic speeds, it is not the shape that provides the least drag. If a missile were to be designed to cruise continuously at transonic speeds, the conventional swept wing would not provide the lowest fuel consumption or the smallest size engine.
Aeronautical research efforts have shown through wind tunnel tests that an oblique wing provides lower drag at transonic speeds than conventional swept wings. Therefore, oblique wings have provided an alternative to conventionally swept wings for high-speed applications. An oblique wing can be made as a single-piece component that can be deployed with one centrally mounted wing pivot connected to the fuselage of an aircraft or missile. Typically, the wing extends at a sweep angle greater than zero and about 30 to 45 degrees during transonic or supersonic speeds. Thus, one end of the wing extends generally in the direction of flight, while the other end trails behind. A missile design employing an oblique wing generally includes a mechanism to pivot the oblique wing from an unswept position before launch to a pivoted oblique position at high speeds.
U.S. Pat. No. 3,971,535 to Jones illustrates an oblique wing utilized in an aircraft design. Missiles and aircraft experience similar lift and drag issues. U.S. Pat. No. 5,154,370 to Cox et al. (“Cox”) discloses a wing mounted on a missile that may pivot from either a stored or unswept position to an oblique position at higher speeds. Cox also discloses that the wing could be stored in a position such that the wing is aligned with the fuselage while the missile is being stowed. A wing actuator unit rotates the wing. The wing actuator unit is a motor-driven pivotal mount. Additionally, Cox discloses that the wing has a very high aspect ratio, such as 22.5 in one embodiment. Thus, Cox teaches a wing design that will preferably remain below critical velocity at speeds of 400 knots (about Mach 0.6) or lower in an unswept position and at speeds of 550 knots (about Mach 0.83) or lower at a sweep angle of 45 degrees in order to avoid unstable eddy flow and flight instability.
It would therefore be advantageous to provide a missile that can maintain transonic speeds. Also, it would be advantageous to provide a missile wing that has a reduced drag coefficient at transonic speeds, as well as reduced fuel consumption and engine size. Finally, it would be advantageous to provide a missile wing that may be easily deployed from a captive carry position to a released position.
The invention addresses the above needs and achieves other advantages by providing a missile capable of traveling at transonic speeds, as well as an oblique wing that may be oriented to a swept position to reduce drag. The missile wing may be pivoted to various sweep angles, and preferably to a predetermined angle such that drag is reduced for a specified speed and altitude.
In one embodiment, the missile includes a fuselage member, and an engine mounted to the fuselage member and capable of thrusting the missile to transonic speed during flight. In this regard, the missile is capable of thrusting to and maintaining transonic speeds. In variations of the present invention, the missile thrusts to transonic speeds of at least about Mach 0.9, and also maintains these speeds for at least 30 minutes. A wing actuator is carried by the fuselage member, and a wing member may be pivotally moved by the wing actuator. Advantageously, the wing member may pivot from a fore-aft position aligned along the fuselage member to various sweep angles, and the wing actuator is capable of pivoting the wing member to a predetermined sweep angle. The wing actuator may be a wound, spring-loaded actuator or an electronic actuator that may cause the wing to pivot to vary the sweep angles during flight.
The wing member may be pivotally mounted to either a lower or an upper surface of the fuselage member. The wing member may pivot to a sweep angle of approximately 30 to 40 degrees such that one end of the wing extends generally in the direction of flight, while an opposite end generally trails behind. The wing member may pivot about a midpoint or a quarter chord of the wing member. Preferably, the wing member has a low aspect ratio, such as, below 7.0.
The present invention includes further variations, such as a restraint attached to the fuselage and positioned proximate to one or both ends of the wing member to keep the wing member substantially free from vibration when positioned in a fore-aft position. Also, an antenna could be positioned within, and substantially along, an entire length of the wing member. Additionally, the missile may also include fins pivotally attached and proximate to a trailing end of the fuselage member.
In another embodiment of the present invention, an aircraft includes a missile releasably attached to the aircraft. As before, the missile further includes a fuselage member, and an engine mounted to the fuselage member and capable of thrusting the missile to transonic speed during flight. A wing actuator is carried by the fuselage member, and a wing member is capable of being pivotally moved by the wing actuator. The wing member may pivot from a fore-aft position aligned along the fuselage member to various sweep angles, and the wing actuator is capable of pivoting the wing member to a predetermined sweep angle.
The present invention further provides a method of launching a missile. The method includes releasably attaching a missile having a fuselage member to an aircraft. The method also includes releasing the missile from the aircraft, wherein the missile further comprises a wing member aligned in a fore-aft position along the fuselage member and operably connected to a wing actuator. The missile is thrust to transonic speed, such as speeds of at least Mach 0.9 that may be maintained for at least 30 minutes. In addition, the method includes pivoting the wing member to a swept position such that the wing member has a swept position during at least a portion of travel of the missile at transonic speed. In this regard, the method may also include releasing restraining pins such that fins pivotally attached and proximate to an aft portion of the fuselage are free to pivot during flight.
Optionally, the method includes pivoting the wing member to a sweep angle of approximately 30 to 40 degrees such that one end of the wing extends generally in the direction of flight and an opposite end generally trails behind. In further variations of the present invention, the method includes providing a signal from an antenna positioned within, and substantially along, an entire length of the wing member. The antenna could be used to transmit or receive a low band radio signal.
The present invention therefore provides a missile wing that reduces drag at high speeds. Advantageously, the missile includes a wing that may be deployed from a captive carry position to a swept position during flight to reduce drag at transonic speeds. The wing may be rotated to various swept positions following release, which allows the wing to be adjusted to accommodate various missiles or to achieve various drag coefficients. Also, the combination of high speeds and reduced drag permits the missile to utilize a smaller jet engine and consume less fuel than if a traditional swept wing were implemented, and the missile does not require afterburners. The missile is further capable of cruising at transonic speeds for extended periods of time and, thus, over extended distances.
Having thus described the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:
The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the invention are shown. Indeed, this invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout.
Referring now to the drawings and, in particular to
In one embodiment of the present invention shown in
The engine 16 is capable of thrusting and maintaining the missile 10 at transonic speeds. In one embodiment, the engine 16 provides about 100 lbs of force, but this can vary depending upon the size and weight of the missile 10 and the desired flight characteristics. The engine 16 of one advantageous embodiment maintains transonic speeds for at least thirty minutes and up to, and even greater than, one hour. Thus, the engine 16 can maintain the missile 10 at transonic speeds for a substantial period of time, which equates to hundreds of nautical miles. However, because the missile 10 is configured to reduce drag at transonic speed, the engine 16 could be any engine suitable to thrust or maintain transonic speeds, for any amount of time, no matter how short in duration.
The missile 10 of the present invention preferably includes a number of additional features, although any number and combination of features could be included. For example, the missile 10 includes a payload located in the fore portion of the missile. Because the missile 10 is preferably guided, the missile 10 also includes a guidance system, which comprises a mission computer, power supply, global positioning system (GPS), selective availability anti-spoofing module (SAASM) receiver (e.g., NavStrike II SAASM GPS Receiver, Rockwell Collins Gov't Systems), and an inertial measurement unit (IMU) (e.g., HG 1700 IMU, Honeywell International, Inc.). Additional features may include a fuel tank, GPS antennas, low and high band antennas, a flight termination system, beacon, and telemetry, as known to those skilled in the art.
A radio frequency antenna 28 may be embedded or attached to the wing 14, such as the underside of the wing, and generally extends the entire length of the wing, as shown in
The missile 10 of the present invention may include each of the following optional features in alternative embodiments to improve the flight characteristics of the missile 10. As shown in
Referring now to
It should be noted that the aforementioned features of the exemplary embodiment of the missile 10 vary as they depend on many factors. For example, the fuselage 12 could be various cross sections, such as elliptical, rectangular, or triangular. In addition, although the aspect ratio of the wing 14 is shown as being about 6.5, the aspect ratio could be even smaller for achieving higher speeds, or larger for achieving slower speeds. However, because the missile 10 preferably travels at transonic speeds, having an aspect ratio that is too large will result in a substantial increase in drag and should be avoided. Thus, an aspect ratio of 7.0 or less is generally preferred. Additionally, the profile of the airfoil could be any suitable airfoil, symmetric or asymmetric, having any number of chord lengths, leading edge radii, trailing edge angles, and thicknesses depending on the drag and lift properties desired as known to those skilled in the art.
The actuator 15 of one embodiment of the present invention is illustrated in
Because the missile 10 could be used weeks, months, or even years after it is assembled, a spring 24 that is tightly wound or compressed may undergo creep or stress relaxation. Therefore, the spring material is advantageously selected to ensure that the actuator 15 and its components will function properly when the missile 10 is ultimately used. An example of a suitable material for the spring 24 is a coiled spring that is 0.562 inches in diameter and a 3AL-8V-6CR-4MO-4ZR titanium rod, i.e., BETA C material, RMI Titanium Company. However, it is understood that various materials for the spring 24 and actuator 15 could be incorporated to ensure that creep and stress relaxation are minimized.
Although the illustrated embodiment shown in
The wing 14 is advantageously a one-piece oblique wing. The wing 14 is aligned in a fore-aft direction along the fuselage, such as on the lower surface of the fuselage 12 such that the wing is substantially aligned with the fuselage 12 during captive carry and until the missile 10 is released and the solenoid 26 activated. The wing 14 is oriented to a sweep angle α of about 30 to 40 degrees by the actuator 15 operating under the control of the mission computer or other device when the solenoid pin 26 is retracted. The wing 14 is preferably connected to the actuator 15 at its midpoint. One end of the wing 14 points generally in the direction of flight, while the opposite end trails behind so that the leading edge of the airfoil is positioned generally fore and the trailing edge of the airfoil is positioned generally aft.
As discussed above, the dimensions of the wing 14 and airfoil profile may be varied depending on the desired L/D ratio and drag coefficient. For example, an aspect ratio of 7.0 or less is generally preferred. Additionally, the wing 14 could be any suitable material, such as aluminum or lightweight composite. If an antenna 28 is to be embedded in the wing 14, a material that is transparent to radio waves is preferable, such as a glass/epoxy composite. Although, it is preferred that the wing 14 assumes a sweep angle α of about 30 to 40 degrees, it is understood that any specified angle could be employed with the missile 10 of the present invention to achieve a desired drag coefficient. It is also understood that the wing 14 could be connected to the actuator 15 at its quarter chord, or any other desired location along the span of the wing. In addition, although the wing 14 is shown in
As shown in
In flight, the wing 14 is oriented to a sweep angle α, which is known to produce lower drag at transonic speeds than would a swept or unswept wing. Testing has indicated that the missile 10 of the present invention may obtain L/D ratios exceeding 4 at an angle of attack of about 4 degrees and Mach 0.9, and a drag coefficient of less than 0.005 at Mach 0.9. Because drag is reduced, a smaller engine is required and less fuel is consumed for higher speeds than would a swept wing under the same conditions.
Many modifications and other embodiments of the invention set forth herein will come to mind to one skilled in the art to which this invention pertains having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the invention is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.
