Patent Application
20140312160
The following disclosure relates generally to flight vehicles and, more particularly, to embodiments of guided munitions and other flight vehicles including scribed frangible seals.
Certain guided munitions are equipped with a plurality of forward-mounted wings or canards, which are hingedly mounted to a forward section of the munition body (e.g., the guidance section shell) for inflight movement from a stowed position to a deployed position. In the stowed position, the canards are recessed within the munition body to impart the guided munition with a streamlined envelope well-suited for loading into a launch tube or similar enclosure. During deployment, the canards rotate about a hinge pin, through longitudinal slots provided in the munition body, and into a deployed position wherein the canards project radially outward from the munition body to provide aerodynamic guidance during flight. The outward rotation of the canards is typically driven by specialized springs housed within the munition body in combination with centrifugal forces, which act on the rolling munition during flight. Canards are, of course, only one example of deployable elements that may be carried by a guided munition and deployed during flight. Examples of other deployable elements include, but are not limited to, other types of flight guidance structures, air turbines, and seeker heads.
If not adequately sealed, canard slots and other deployment openings in the munition body may permit the ingress of environmental contaminants, such as water droplets, ice, dirt, sand, and other debris. If permitted to accumulate within the guided munition, such contaminants can potentially interfere with the operation of the munition's internal components, such as the control actuation system utilized to manipulate the canards during flight. Environmental seals have been developed that can seal canard slots and other openings in the munition fuselage to prevent or minimize the ingress of contaminants. Conventional environmental seals are, however, limited in several regards. Conventional environmental seals are typically incapable of maintaining sealing properties when repeatedly exposed to extreme thermal and pressure loading conditions. As a result, conventionally-known environmental seals are typically unsuitable for usage in conjunction with guided munitions carried by multi-tube launchers and repeatedly exposed to rocket motor exhaust during the launch of neighboring munitions. Similarly, conventionally-known environmental seals may be unsuitable for usage with guided munitions exposed high thermal loads due to aerodynamic heating during supersonic flight. As a further limitation, conventionally-known environmental seals typically require dedicated actuators (e.g., electromechanical or pyrotechnic devices) to jettison or otherwise displace the seals immediately prior to canard deployment. Such dedicated seal actuators add undesired cost, weight, and bulk to guided munition. In addition, the usage of such dedicated seal actuators may be precluded by spatial limitations in the case of laser-guided rockets and other small form factor munitions.
There thus exists an ongoing need to provide embodiments of an environmental seal suitable for sealing a deployment opening in the body of a guided munition or other flight vehicle that overcomes many, if not all, of the above-noted limitations. In particular, it would be desirable to provide an environmental seal through which a deployable element (e.g., a canard) may deploy in a reliable and lower energy manner without requiring a dedicated seal actuator. Ideally, embodiments of such an environmental seal would be capable of maintaining structural integrity and sealing properties through repeated exposure to relatively harsh thermal and pressure loading conditions. It would also be desirable for such an environmental seal to be relatively inexpensive to produce, to be amenable to automated manufacture, to be compact and lightweight, to have a relatively low water vapor permeability, and to produce little to no sizable debris upon deployment. Lastly, it would be desirable to provide embodiments of a flight vehicle equipped with one or more environmental seals of the type described above, and to provide methods for equipping flight vehicles with environmental seals. Other desirable features and characteristics of the present invention will become apparent from the subsequent Detailed Description and the appended Claims, taken in conjunction with the accompanying Drawings and this Background.
Embodiments of a flight vehicle are provided. In one embodiment, the flight vehicle includes a vehicle body having an opening therein; a deployable element, which resides in a stowed position within the vehicle body and which is movable into a deployed position; and a scribed frangible seal. At least a potion of the deployable element passes through the opening when moving from the stowed position into the deployed position. The flight vehicle further includes a scribed frangible seal, which is sealingly disposed over the deployment opening and which is positioned so as to be contacted by the deployable element during deployment thereof. The scribed frangible seal fractures along at least one scribe line when contacted by the deployable element to permit movement of the deployable element from the stowed position to the deployed position.
Embodiments of a scribed frangible seal are further provided for sealing a deployment opening through which a deployable element deploys. In one embodiment, the scribed frangible seal includes a ceramic substrate and at least one laser scribe line, which is formed in a surface of the ceramic substrate and which impart the ceramic substrate with a predetermined rupture strength. The ceramic substrate fractures along the at least one laser scribe lines when contacted by the deployable element during deployment thereof.
Embodiments of a method for equipping a flight vehicle with a scribed frangible seal are still further provided. The flight vehicle includes a vehicle body configured to house a deployable element when in a stowed position. The vehicle body has a deployment opening therein through which at least a portion of the deployable element passes when moving from the stowed position into a deployed position. In one embodiment, the method includes the steps of obtaining a scribed frangible seal, positioning the scribed frangible seal over the deployment opening in the vehicle body at a location at which the scribed frangible seal will be contacted by the deployable element during deployment thereof, and bonding the scribed frangible seal to the vehicle body to seal the deployment opening.
At least one example of the present invention will hereinafter be described in conjunction with the following figures, wherein like numerals denote like elements, and:
The following Detailed Description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any theory presented in the preceding Background or the following Detailed Description. As appearing herein, the term “flight vehicle” is defined to encompass munitions, sub-munitions, munition-mountable devices (e.g., precision guidance kits), Unmanned Aerial Vehicles, exoatmospheric vehicles, spacecraft, and other airborne and space-borne platforms of type which carry at least one deployable device or structure. As further appearing herein, the term “scribe line” is utilized to denote an area of reduced thickness formed in a frangible, rigid substrate to promote fracture of the substrate when contacted by a deployable element, such as a deployable flight control surface, during deployment thereof. Unless otherwise specified, the area of reduced thickness is not limited to any particular shape or pattern and may assume the form of, for example, a continuous (unbroken) line or discontinuous (broken, dashed, or dotted) line, whether having a linear (straight) or non-linear geometry.
The following describes several exemplary embodiments of a scribed frangible seal, such as a laser scribed ceramic seal, that provides multiple advantages over conventionally-known environmental seals. Amongst other advantages, embodiments of the scribed frangible seal described herein are able maintain structural integrity and sealing properties through repeated exposure to highly elevated thermal and pressure loading conditions. In addition, embodiments of the scribed frangible seal are compact, lightweight, and enable reliable deployment of a deployable element (e.g., a canard) at a desired time of deployment without the assistance of a dedicated seal actuator. For these reasons, embodiments of the scribed frangible seal are especially well-suited for usage in conjunction with small form factor guided munitions and/or munitions repeatedly exposed to high thermal and pressure loading conditions prior to munition launch. To further emphasize this point, the following describes embodiments of the scribed frangible seal in conjunction with a particular type of guided munition carried by a particular type of launch platform, namely, a laser-guided rocket carried by a multi-tube launcher. This notwithstanding, it is emphasized that embodiments of the scribed frangible seal can be deployed onboard other guided munitions and launch platforms including, for example, a guided munition carried by the wing of a supersonic aircraft. Additionally, embodiments of the scribed frangible seal described herein can be utilized to seal openings in the bodies or fuselages of flight vehicles other than guided munitions including, but are not limited to, satellite, exoatmospheric vehicles, and Unmanned Aerial Vehicles. Similarly, embodiments of the scribed frangible seal described herein can be utilized to seal deployment openings in munition systems generally, such as an opening provided through a launch canister or other launch enclosure through which a guided munition is launched. Lastly, while described below in conjunction with a particular type of deployment opening (i.e., a plurality of canard slots) through which a particular type of flight guidance structure (i.e., a plurality of canards) deploys, it is further emphasized that embodiments of the scribed frangible seal can be utilized to sealingly enclose any opening provided in the body or fuselage of a flight vehicle through which a deployable element (e.g., a flight guidance structure, an air turbine, a seeker head, or the like) deploys.
A plurality of longitudinal openings or slots 42 is provided through guidance section shell 36 adjacent the location at which canards 40 are hingedly coupled to shell 36. As are canards 40, slots 42 are circumferentially spaced around a mid-section of guidance section shell 36. Canard slots 42 each assume the form of an elongated opening or aperture formed through the annular sidewall of guidance section shell 36 and extend in a direction substantially parallel with the longitudinal axis of guided munition 20. In the stowed position, canards 40 reside within shell 36 to provide physical protection and to impart munition 20 with a streamlined profile well-suited for loading into multi-tube launcher 12 (
It is desirable to seal canard slots 42 to prevent the ingress of environmental contaminants (e.g., water droplets, ice, dirt, sand, and other debris) that could potentially interfere with the internal operation of guided munition 20 and decrease munition reliability. While environmental seals have been developed for usage in conjunction with certain guided munitions, conventionally-known environmental seals are generally unsuitable for usage in conjunction with guided munition 20 and similar guided munitions for at least two reasons. First, guided munition 20 has a relatively compact form factor, when viewed along its longitudinal axis in a fore-aft direction; e.g., the maximum outer diameter of the body of munition 20 may be approximately 70 millimeters (2.75 inches). Insufficient space may consequently be provided to accommodate the dedicated actuators (e.g., electromechanical or pyrotechnic devices) typically required to jettison or other remove conventionally-known environmental seals prior to canard deployment. Second, conventionally-known environmental seals are generally unable to maintain adequate sealing properties through repeated exposure to harsh thermal and pressure loading conditions. As a result, conventionally-known environmental seals are typically unsuitable for usage in conjunction with a multi-tube launcher (e.g., launcher 12 shown in
Substrate 48 may be fabricated from various different materials, depending upon desired rupture strength, temperature tolerances, and similar considerations. Candidate materials include, but are not limited to, plastics, glasses, ceramics, and silicon-containing materials. These examples notwithstanding, substrate 48 is preferably fabricated from a ceramic material. As appearing herein, a “ceramic material” or a “ceramic” is defined as an inorganic and non-metallic material, whether crystalline or amorphous. Advantageously, and in contrast to organic materials, ceramics are able to withstand highly elevated temperatures with little to no structural degradation and are consequently well-suited for usage when seal 46 is subjected to extreme temperatures due to, for example, repeated exposure to rocket motor exhaust. Additionally, ceramics are relatively brittle when placed under tension and can thus be designed, by strategic positioning of scribe lines 56, to fracture when rigid substrate 48 is subjected to a relatively modest internal loading force, as will be described below. As a further advantage, ceramic materials also typically have relatively low water vapor transmission rates to support desiccant sizing of substrate 48. A non-exhaustive list of ceramics suitable for the fabrication of substrate 48 includes alumina, zirconia, silicon carbide, beryllium oxide, and aluminum nitride. Of the foregoing list, aluminum oxide or alumina (Al2O3) is generally preferred in view of its relatively low cost and widespread commercial availability.
Scribe lines 56 are advantageously formed in at least the outer face 50 of substrate 48; that is, the outer major surface of substrate 48 residing substantially opposite canard 40 (or other deployable element) when in the stowed position. Formation of scribe lines 56 in the outermost face 50 of substrate 48 is particularly advantageous in embodiments wherein substrate 48 is fabricated from a ceramic or other material prone to failure under tension; in such embodiments, application of a relatively modest force to the inner face of substrate 48 by canard 40 (or a like deployable element) will place scribed outer face 50 in tension and readily initiate fracture of substrate 48. Thus, by forming substrate 48 from a ceramic and by forming scribe lines 56 in outer face 50, scribed frangible seal 46 can be designed to fracture or fail with minimal internal loading and, therefore, with the aid of a low force/energy deployment spring acting on substrate 48 through canard 40. Externally-applied forces, by comparison, will tend to place scribed outer face 50 in compression and therefore be less likely to result in the inadvertent or premature fracture of substrate 48. The inner face of rigid substrate 54, which resides adjacent canard 40 in the stowed state, may be left unscribed to further decrease the likelihood of the inadvertent fracture of substrate 48 due to externally-applied forces. Alternatively, scribe lines may be formed in the inner face of substrate 48 in addition to outer face 50 to minimize the rupture threshold of scribed frangible seal 46.
Scribe lines 56 can be formed by any suitable mechanical process wherein material is removed from one or more surfaces of rigid substrate 48 utilizing a cutting tool, such as a diamond saw. Alternatively, scribe lines 56 can be formed by an additive process wherein substrate 48 is fabricated to inherently include regions of reduced thickness by, for example, a casting process, a molding process, or through the usage of a rapid prototyping technique, such as stereolithography (also commonly referred to as “three dimensional printing,” “photo-solidification,” or “optical printing”). These examples notwithstanding, scribes lines 56 are preferably formed utilizing a laser scribing process. The industrial viability and capabilities of laser scribing processes have been well-demonstrated within the semiconductor industry wherein such processes are utilized during singulation of wafers into individual die (commonly referred to as “dicing”). During laser scribing, a laser is controlled to impinge upon selected areas of substrate 48 and remove material therefrom. The laser energy may be pulsed as the laser passes over the outer surface of substrate 48 such that each scribe line 56 is formed as a series of perforations or blind holes. To further exemplify this point,
The dimensions, orientation, location, and pattern of scribe lines 56 may vary amongst different embodiments of frangible seal 46. In certain embodiments, scribe lines 56 may form a cross-hatched, grid, or lattice pattern across outer face 50 of rigid substrate 48. In preferred embodiments, scribe lines 56 extend from an aft portion of substrate 48 to a forward portion thereof in a generally longitudinal direction. In the exemplary embodiment illustrated in FIG. 3, specifically, five substantially parallel scribe lines 56 are formed in a central portion of outer face 50 and extend from an aft end portion of substrate 48 to the forward end portion thereof; stated differently, scribe lines 56 are formed proximate and are substantially parallel to the centerline of frangible seal 46. To optimize energy propagation during substrate fracture, scribe lines 56 are preferably each formed have a substantially linear or straight geometry; however, various other geometries are also possible. Regardless of the particular form assumed thereby, scribe lines 56 are preferably produced in a region of substrate 48 substantially opposite the location at which canard 40 impacts substrate 48 during deployment. The formation multiple scribe lines helps to ensure canard impact within close proximity of at least one scribe line and thus compensates for variation that may occur in impact location within acceptable manufacturing tolerances. By forming a plurality of substantially parallel scribe lines 56 across a central portion of rigid substrate 48 in the manner shown in
In further embodiments of scribed frangible seal 46, a face bond may be employed in addition to, or in lieu, of a flexible edge bond; that is, inner face 60 of substrate 48 may be bonded to floor 62 of depression 53, as shown in
The foregoing has thus provided multiple exemplary embodiments of an scribed frangible seal suitable for sealing a deployment opening in the body of a flight vehicle (e.g., a canard slot or other opening in the shell of a guided munition) through which a deployable element (e.g., a canard) can deploy without the usage of a dedicated seal actuator. Embodiments of the above-described environmental seal are able to remain structurally intact and to maintain adequate sealing properties through repeated exposure to extreme thermal and pressure loading conditions and are consequently well-suited for usage within guided munitions carried by multi-tube launchers and supersonic aircraft. Embodiments of the above-described scribed frangible seal are relatively inexpensive to produce, are amenable to automated manufacture, are compact and lightweight, produce no sizable debris upon deployment, have a relatively low water vapor permeability, and allow deployment in reliable and repeatable manner. The foregoing has also provided embodiments of a guided munition or other flight vehicle equipped with such a scribed frangible seal, as well as embodiments of a method for equipping a flight vehicle with such a scribed frangible seal.
While described above primarily in the context of a guided munition, embodiments of the scribed frangible seal disclosed herein can be utilized to seal deployment openings in munition systems generally including, for example, containerized munition systems. For example, embodiments of the scribed frangible seal can be utilized to seal a deployment opening provided through a launch canister or other launch enclosure from which a containerized guided munition is launched. In this case, the scribe frangible seal may assume the form of a lid, which is sealingly positioned over the launch canister's open end and which fractures when the guided munition is launched from the launch canister, due either to contact with the nose of the guided munition (the deployable element) during munition fly-out.
While at least one exemplary embodiment has been presented in the foregoing Detailed Description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing Detailed Description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment of the invention. It being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the invention as set-forth in the appended Claims.
