Patent Application
20210055085
Aerial rockets and missiles which include folded, deployable guidance wings, have been in use for many years. Some examples include the Hydra 70 family of WAFAR (Wrap-Around Fin Aerial Rocket) and APKWS® laser guided missile. For many such weapons, the guidance wings are folded in a stowed configuration within the main fuselage until the weapon is launched, at which point the wings deploy outward through slots provided in the fuselage.
In one such example, the APKWS precision guidance kit is added to a 2.75″ (70 mm) diameter rocket such as the Hydra-70 (MK66). The APKWS has wings that start in a stowed position thus allowing the munition to fit inside existing launching tubes. When the rocket is fired it begins to spin to improve stability. Firing of the rocket awakens the APKWS system. Once the control system is initiated and operational, the four control surfaces, known as flaperons, are commanded to rotate to the zero position, thus unlatching them from their stow latch. Once unlatched, the centrifugal force of the spinning rocket causes the wings/control surfaces to pivot about a fixed point near their root and deploy outwards to approximately a 30° angle from the munition centerline.
In some cases, the wing slots are covered by frangible seals which protect the interior of the missile from moisture and debris during storage, transport, and handling. For example, the APKWS has environmental seals covering the four wing slots to protect the internal components. Examples of wing slot seals disposed on an APKWS are disclosed in U.S. Pat. No. 8,895,908, assigned to the same assignee as the present application, the entire disclosure of which is hereby incorporated by reference. In these cases the guidance wings must be deployed with sufficient initial force to enable them to penetrate the seals.
However, there is a practical limit to how rapidly a missile can be spun. In one example, the average centrifugal force on the tip of a guidance wing at the beginning of deployment is only approximately 7.7 pounds at the minimum spin rate. This amount of centripetal energy may not be sufficient by itself to enable the wings to burst through the frangible slot covers. As a result, some weapons that include deployable folded guidance wings and frangible wing slot covers have demonstrated a tendency for the guidance system to fail due to a lack of proper guidance wing deployment.
One approach to address this problem is the addition of a wing deployment force initiator, which assists the deployment of the guidance wings by providing an initial burst of energy to help the wings break through the frangible covers. In one such design, the wing deployment initiator uses explosives to push the wings through the frangible covers. However, this approach can be undesirable due to the violent forces produced by the explosives and due to concerns about the safety and the long-term chemical stability of the explosives during storage of the weapon.
Another approach is to provide a torsion spring wing deployment initiator which provides additional force to push the wings outward a small amount. One such torsion spring wing deployment initiator is described in U.S. Pat. No. 8,868,329 assigned to the same assignee as the present application, the entire disclosure of which is hereby incorporated by reference. This approach avoids the problems of using explosives. An alternative approach is a compression spring wing deployment initiator. One such compression spring wing deployment initiator is described in U.S. Pat. No. 8,754,352, assigned to the same assignee as the present application, the entire disclosure of which is hereby incorporated by reference.
However, there is only very limited space available for a wing deployment initiator to occupy. Also, for some applications, the weight of the deployment initiator should be as low as possible. Therefore, it is desirable to provide a mechanical wing deployment initiator which can provide sufficient force to enable the guidance wings to break through the frangible covers while also fitting within the available space and remaining sufficiently light in weight.
For certain applications, a more compact and less complex solution would be desirable, since the reduced complexity would lower the cost of production and would decrease the likelihood of failure if the mechanism did not perform as intended.
In one embodiment, an aerial projectile, such as a missile or rocket, is disclosed having a fuselage, at least one wing slot formed in the fuselage and a wing slot seal covering each of the at least one wing slot. A guidance wing in a stowed position within each of the at least one wing slot prior to deployment of the wing, includes a puncturing feature formed on a leading edge of the wing. The puncturing feature is configured to break through the wing slot seal during deployment of the wing from the stowed position. In a further embodiment a precision guidance kit is an assembly that is configured to couple to a rocket, such as the Hydra rocket, and comprises wings, slot seal, and related components.
In one embodiment, the puncturing feature is a small sharp region on the leading edge near the wing tip that first contacts the wing slot seal. In one embodiment, the small sharp feature is formed by a sharp point.
In one embodiment, the puncturing feature is a sharp edge extended along the leading edge of the wing to provide a cutting action as the wing passes through the wing slot seal. In one embodiment, the extended sharp edge puncturing feature has serrations to increase the cutting action.
Further features as well as the structure and operation of various embodiments are described in detail below with reference to the accompanying drawings. In the drawings, like reference numbers indicate identical or functionally similar elements.
In one embodiment a puncturing feature is provided on the wing of the rocket to facilitate breaking through the wing slot seal. In one embodiment, the puncturing feature is small sharp region on the leading edge near the wing tip. This is the region of the wing that first contacts the wing slot seal. In one embodiment, the small sharp feature has a sharp point that will puncture the wing slot seal just like a bird's egg tooth.
In one embodiment, the puncturing feature is a sharp edge extended along the leading edge of the wing to provide a cutting action as the wing passes through the wing slot seal. In one embodiment the additional length of the sharp edge would slice the wing slot seal as the wing passes through just like a knife blade. In one embodiment, the extended sharp edge puncturing feature has serrations to increase the cutting action.
The puncturing feature is an improvement over the prior art deployment initiators by reducing the amount of force required by the wing to puncture the wing slot seal and improve wing deployment reliability. In one embodiment, the puncturing feature reduces the deployment force enough where the wings can deploy reliably without the need for an additional mechanical deployment initiator, thereby avoiding the increased weight and cost of the prior art solutions.
The puncturing feature could be a machined feature of the wing or it could be a separate part that is then attached to the wing. The puncturing feature may to be made from a material with structural hardening such as steel, stainless steel and tungsten carbide. In one example, metal hardness may be specified by ASTM E18, which is a standard that defines the Rockwell hardness test method for metallic materials. In one embodiment, a metallic material that has a Rockwell C-scale hardness of 35 or greater may be specified. In one embodiment, the puncturing feature may be made with fine grain properties that it can be sharpened to a keen edge, such as those meeting the test detailed in ASTM standard E112. However, other materials such as hard plastic, ceramic or glass could serve as the puncture and/or cutting feature.
According to one embodiment, the wings 12, wing slots 16, and frangible cover seals 18 along with guidance and navigation electronics are integrated into a precision guidance kit 25. The precision guidance kit 25 in one example is contained within a section of the fuselage 27 with connectors (not shown) such that the precision guidance kit 25 is secured between the rocket section and the warhead section. In one example the precision guidance kit 25 is screwed onto the rocket and the warhead. The precision guidance kit 25 is coupled to a rocket in order to convert the rocket into a precision guided projectile. One example of this is the APKWS precision guidance kit.
In one embodiment, the wing slot seal provides a frangible barrier against exposure of internal components of a rocket or missile to external contaminants, while enabling deployment of a wing stored within the rocket or missile simply by bursting of the wing through the frangible seal. The seal is strong enough to resist rupture or dislodgement from the exterior due to normal transport and handling of the missile, while at the same time presenting minimum resistance to penetration from the interior when the guidance wings are deployed by bursting through the seal.
In one embodiment, the wing slot seal is a thin, flexible sheet which can be adhered to a surface of the fuselage of the rocket or missile so as to cover a wing slot. In embodiments, the seal is sufficiently thin so as not to exceed the diameter of “bore riders” of the missile which define the maximum diameter of the missile, and which support the missile when resting within a cylindrical launching or transporting tube.
In one embodiment, the thin, flexible sheet includes an outer layer and an inner layer. Both of the layers may be made of a nickel alloy, and in some of these embodiments one layer is made of half-hard nickel sulfamate, while the other layer is made of fully hard nickel sulfamate. The inner layer includes at least one burst seam which assists the wing in breaking through the seal for deployment. The flexible sheet may be curved according to the cylindrical shape of the rocket or missile, and the two layers are stiff, although flexible, so that inward deformation due to pressure applied from outside the rocket or missile tends to force the edges of the burst seam together, thereby resisting the applied force, while outward deformation caused by the wing pressing against the seal from within the rocket or missile tends to force the edges of the burst seam apart, so that the wing passes through the cut or cuts in the inner layer and is only required to break through the outer layer.
In one embodiment, the flexible sheet is resilient or “springy,” so that once the wing is deployed, portions of the flexible sheet which lie against the deployed wing remain substantially flush against the wing, while portions of the flexible sheet which are not adjacent to the deployed wing tend to spring back into place and close the opening made in the frangible seal. The effect of the frangible seal on the aerodynamics of the rocket or missile is thereby minimized.
While the present invention has been particularly shown and described with respect to preferred embodiments thereof, it will be understood by those skilled in the art that the foregoing and other changes in forms and details may be made without departing from the spirit and scope of the present invention. It is therefore intended that the present invention not be limited to the exact forms and details described and illustrated, but fall within the scope of the appended claims.
