US20140312160A1

US20140312160A1 - Flight vehicles including scribed frangible seals and methods for the manufacture thereof

Info

Publication number: US20140312160A1
Application number: US13/154,614
Authority: US
Inventors: Alexandra L. Blake; W. Howard Poisl; Thomas E. Fetsko; Timothy B. Mellor
Original assignee: Raytheon Co
Current assignee: Raytheon Co
Priority date: 2011-06-07
Filing date: 2011-06-07
Publication date: 2014-10-23
Also published as: EP2718658A1; WO2012170659A1

Abstract

Embodiments of a flight vehicle including a scribed frangible seal are provided, as are embodiments of a scribed frangible seal and a method for equipping a flight vehicle with a scribed frangible seal. In one embodiment, the flight vehicle includes a vehicle body having a deployment opening therein, and a deployable element residing in a stowed position within the vehicle body and movable into a deployed position. At least a potion of the deployable element passes through the deployment 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.

Description

TECHNICAL FIELD

The following disclosure relates generally to flight vehicles and, more particularly, to embodiments of guided munitions and other flight vehicles including scribed frangible seals.

BACKGROUND

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.

BRIEF SUMMARY

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.

BRIEF DESCRIPTION OF THE DRAWINGS

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:

FIG. 1 is an isometric view of a plurality of guided munitions carried by an exemplary multi-tube launcher;

FIG. 2 is an isometric view of an exemplary guided munition after launch from the multi-tube launcher shown in FIG. 1 and equipped with a plurality of canards, which deploy through a plurality of canard slots formed in the munition body;

FIG. 3 is an isometric view illustrating a canard in a stowed position and a scribed frangible seal suitable for creating an environmental seal over one of the canard slots shown in FIG. 2 and illustrated in accordance with an exemplary embodiment of the present invention;

FIGS. 4 and 5 are top-down and cross-sectional views, respectively, illustrating a portion of a laser scribe line formed in the substrate of the scribed frangible seal shown in FIG. 3;

FIGS. 6 and 7 are isometric views of a portion of the munition body shown in FIG. 2 prior to and after, respectively, the installation of plurality of scribed frangible seals over the canard slots provided in the munition body;

FIG. 8 is a cross-sectional view of a canard in a stowed position and the scribed frangible seal shown in FIG. 3 illustrating a first exemplary manner in which the scribed frangible seal may be adhesively attached to the munition body utilizing a flexible edge bond;

FIG. 9 is a cross-sectional view of the canard and scribed frangible seal shown in FIG. 8 during deployment of canard through the scribed frangible seal and the fracture of the scribed frangible seal into two longitudinally-extending pieces, which rotate outward from the munition body about the flexible edge bond to permit passage of the canard;

FIG. 10 is a cross-sectional view of a canard in a stowed position and the scribed frangible seal shown in FIG. 3 illustrating a second exemplary manner in which the scribed frangible seal may be adhesively attached to the munition body utilizing a face bond; and

FIG. 11 is a flowchart illustrating an exemplary method for equipping a guided munition or other flight vehicle with a scribed frangible seal.

DETAILED DESCRIPTION

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.
FIG. 1 is an isometric view of an exemplary multi-tube launcher 12 carried by an arm 14 of a rotary-wing aircraft 16. Multi-tube launcher 12 includes a plurality of launch tube openings 18 into which a number of guided munitions 20 are loaded such that a forward end of each munition 20 extends beyond the leading face or bulkhead of launcher 12. Guided munitions 20 are sequentially launched or fired from multi-tube launcher 12 on an as-needed basis. To launch a particular guided munition 20 from launcher 12, an ignition charge is triggered to initiate controlled combustion of a solid propellant held within the munition's rocket motor section and thereby generate exhaust gases, which flow through the munition's rocket motor nozzle to produce forward thrust. As the aft end of the munition clears the mouth of its launch tube opening, the hot combustive gases exhausted by the munition impinge upon the bulkhead of multi-tube launcher 12, spread radially outward, and flow over the exposed forward ends of the munitions remaining within launcher 12. The exposed forward ends of the munitions remaining within multi-tube launcher 12 are thus enveloped in a plume of rocket motor exhaust each time a neighboring munition is launched from launcher 12. A given munition carrier by launcher 12 can consequently be subjected to highly elevated temperatures and localized pressures several times before the guided munition is, itself, launched; e.g., in the illustrated embodiment wherein launcher 12 assumes the form of a nineteen-tube launcher, the forward end of the last-launched munition may be enveloped in rocket motor exhaust eighteen times prior to usage and excluding reloading of launcher 12.
FIG. 2 is an isometric view of a guided munition 20 after launch from multi-tube launcher 12 (FIG. 1) and illustrated in accordance with an exemplary embodiment of the present invention. In this particular example, guided munition 20 assumes the form of a laser-guided rocket having a rocket motor section 22, a warhead section 24, and a guidance section 26. Rocket motor section 22 includes a tubular casing 28 containing a solid propellant or grain (not shown), a rocket motor nozzle 30 mounted to the aft end of casing 28, and a plurality of tail fins 32 circumferentially spaced about the aft end of casing 28 proximate nozzle 30. Warhead section 24 includes a tubular shell 34 containing one or more warheads (also not shown). Guidance section 26 includes a tubular shell 36, a seeker 38 mounted to the forward end of shell 36, and a plurality of forward-mounted wings or canards 40. Canards 40 are hingedly mounted to a mid-section of shell 36 such that each canard 40 is movable from a stowed position to the deployed position shown in FIG. 2 at a desired time of deployment. Collectively, casing 28 of rocket motor section 22, shell 34 of warhead section 24, and shell 36 of guidance section 26 form the body of guided munition 20. Although hidden from view in FIG. 2, guidance section 26 further includes at least one fuse; a control actuation system for inflight manipulation of canards 40; and an onboard navigational computer operably coupled to the fuse, the control actuation system, and seeker 38. During flight, seeker 38 provides the onboard navigational computer with signals indicative of target location based upon, for example, registered laser pulse energy reflected from a designated target and emitted from a laser designator. Navigational computer then determines from these signals the manner in which the rotational position canards 40 should be manipulated by the control actuation system to guide munition 20 to its designated target in a highly accurate manner.
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 (FIG. 1) or a similar launch platform. As indicated in FIG. 2 by arrows 44, canards 40 rotate outward from the body of munition 20, through canard slots 42, and into their deployed positions at the desired time of deployment, which will typically be during launch or during the early stages of munition flight. When fully deployed, canards 40 project radially outward from guidance section shell 36 to provide aerodynamic guidance during munition flight, as previously described. The outward rotation of canards 40 is driven by specialized springs housed within guided munition 20 (not shown) in combination with centrifugal forces, which act on canards 40 as guided munition 20 spins or rolls rapidly during flight.
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 FIG. 1) wherein any externally-exposed structure located at the munition's forward end, including any environmental seals positioned over slots 42, may be directly and repeatedly contacted by rocket motor exhaust during the launch of neighboring munitions (note that canards slots 42 and any environmental seals covering slots 42 are not shown in FIG. 1 for clarity). The following describes several exemplary embodiments of a scribed frangible seals useful for forming an environmental seal over a canard slot (or other deployment opening) provided in the body of a guided munition (or other flight vehicle) that is relatively compact, that does require the provision of a dedicated seal actuator, and that is capable of maintaining sealing properties through repeated exposure to highly elevated thermal and pressure loading conditions.
FIG. 3 is an isometric view of a canard 40 and a scribed frangible seal 46 suitable for sealing or enclosing one of canard slots 42 formed in shell 36 of guided munition 20 (shown in FIG. 2) in accordance with an exemplary embodiment of the present invention. Scribed frangible seal 46 includes a rigid substrate 48 having a plurality of scribe lines 56 formed therein. Rigid substrate 48 is preferably fabricated as a single or unitary piece, although the possibility that rigid substrate 48 may be fabricated from multiple pieces or components is by no means excluded. As shown in FIG. 3, rigid substrate 48 will typically assume the form of a relatively thin, plate-like body; however, it will be understood that the particular geometry and dimensions of substrate 48 will vary in further embodiments depending upon the particular shape and size of the munition opening sealed by scribed frangible seal 46. In the illustrated example wherein scribed frangible seal 46 is utilized to sealingly enclose an elongated canard slot, rigid substrate 48 is fabricated to have an elongated, generally rectangular geometry suitable for covering the entirety of slot 42 when substrate 48 is bonded or otherwise attached to guidance section shell 36, as described more fully below in conjunction with FIGS. 6-9. The thickness of rigid substrate 48 will generally be determined by space constraints and the desired rupture strength of scribed frangible seal 46; however, by way of non-limiting example, substrate 48 may have a thickness between approximately 0.010 and 0.030 inch.
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, FIGS. 4 and 5 are top-down and cross-sectional views, respectively, illustrating a segment of a laser scribe line 56(a) formed in a portion of substrate 48. As can be seen in FIGS. 4 and 5, laser scribe line 56(a) is generally defined by a series of blind holes 58, which are formed in outer face 50 of substrate 48 and which extend toward, but do not penetrate, inner face 60 of substrate 48. Notably, the laser scribing process parameters (e.g., laser pulse intensity, duration, sweep, etc.) can be manipulated, as appropriate, to adjust the average pitch or spacing (identified as “S” in FIG. 5), width, (identified as “W” in FIG. 5), and depth (identified as “D” in FIG. 5) of blind holes 58 and thereby impart rigid substrate 48 with a targeted rupture strength in a highly controllable manner. Laser scribing can also be utilized in combination with mechanical breaking to separate substrate 48 from a larger ceramic sheet, as described more fully below in conjunction with FIG. 11.
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 FIG. 5, a preferred failure mode can be reliably achieved wherein substrate 48 fractures (and thus energy propagates) along a single, substantially linear, longitudinally-extending fault line, which extends the length of rigid substrate 48. In the illustrated example, scribe lines 56 extend across the entire length of rigid substrate 48 and, thus, from the forward edge of substrate 48 to the aft edge thereof. In further embodiments, scribe lines 56 may terminate prior to reaching the outermost edges of substrate 48. In still further embodiments, and by way of example only, scribe lines 56 may converge to notches or cut-outs formed in opposing ends of rigid substrate 48 to further promote fracture of substrate 48 along a substantially linear, longitudinally-extending fault line.
FIGS. 6 and 7 are isometric views of guidance section shell 36 prior to and after the installation of scribed frangible seals 46 over canard slots 42, respectively. As shown most clearly in FIG. 6, longitudinal depressions 53 are formed in the external surface of shell 36 around canard slots 42 such that each canard slot 42 is surrounded or circumscribed by an individual depression 53. Scribed frangible seals 46 are matingly installed within depressions 53. Depressions 53 may each have a length and width slightly greater than the length and width of seals 46, providing that a circumferential clearance is provided around each seal 46 for the application of a high temperature adhesive. The depth of depressions 53 is preferably equivalent to or slightly greater than the thickness of seals 46. When installed within depressions 53, scribed frangible seals 46 cooperate with guidance section shell 36 to form an aerodynamically streamlined structure having a substantially uninterrupted outer annular surface. Furthermore, when installed within depressions 53, the outer surfaces or faces of seals 46 may be substantially flush with or slightly recessed with respect to the outer surface of guidance section shell 36.
FIG. 8 is a cross-sectional view taken through a scribed frangible seal 46 and a portion of guidance section shell 36 illustrating one manner in which seal 46 may be adhesively bonded to shell 36 and, specifically, to the surfaces of shell 36 defining depression 53. It can be seen in FIG. 8 that a central longitudinal portion of inner face 60 of rigid substrate 48 is exposed through canard slot 42, while the outer longitudinal portions of inner face 60 are supported by the floor 62 of depression 53. Such a supportive arrangement further decreases the likelihood of the inadvertent or premature fracture of seal 46 due to externally-applied forces. It can also be seen in FIG. 8 that scribe lines 56 are formed in the outer face 50 substantially opposite canard 40 and, in particular, substantially opposite the location at which canard 40 will contact rigid substrate 48 during deployment. A high temperature adhesive 64 is applied around seal 46 such that the outer circumferential edge 52 of substrate 48 is bonded to the inner sidewalls of depression 53. The chosen adhesive is preferably able to remain flexible for an extended time period over the operational temperature range of guided munition 20 (FIG. 2). In addition, the chosen adhesive preferably has sufficient flexibility (e.g., compressibility and/or elasticity) to accommodate relative movement between the outer edges of rigid substrate 48 and the inner circumferential surfaces of shell 36 defining depression 53 that may occur during heating due to differences in coefficients of thermal expansion. In one embodiment, a high temperature silicone adhesive is utilized, such as RTV88 silicone adhesive commercially available from Momentive Performance Materials, Incorporated, currently headquartered in Columbus, Ohio. While abutting floor 62 of depression 53 when seal 46 is positioned therein, inner face 60 of substrate 48 is preferably not bonded to guidance section shell 36 such that, when seal 46 fractures into at least two pieces, the two pieces can readily rotate or hinge outward to permit the passage of canard 40, as described below in conjunction with FIG. 9.
FIG. 9 is a cross-sectional view illustrating scribed frangible seal 46 during deployment of a canard 40. As indicated in FIG. 9 by arrow 66, canard 40 has contacted and exerted sufficient force on substrate 48 to cause seal 46 fracture along a longitudinal fault line 68 into two opposing sections or pieces 46(a) and 46(b). As further indicated in FIG. 9 by arrows 70, the inner edges of seal pieces 46(a) and 46(b) rotate outward from guided munition shell 36 about the locations at which pieces 46(a) and 46(b) are flexibly bonded to shell 36, respectively, to accommodate the passage of canard 40. As this occurs, any flexible adhesive present at the opposing aft and forward ends of rigid substrate 48 tears to allow the outward divergent rotation of seal pieces 46(a) and 46(b). Such a flexible edge bond provides a relatively long moment arm to assists with centerline fracture of rigid substrate 48 along longitudinally-extending scribe lines 56. In so doing, the flexible edge bond allows canard penetration through seal 46 in response to a relatively modest force applied to inner face 60 of substrate 48 substantially opposite scribe lines 56 as may be provided by a relatively weak spring force (e.g., a spring force less than approximately 18 pound-force, as applied to substrate 48) and, therefore, without provision of a dedicated seal actuator (e.g., an electromechanical or pyrotechnic device) of the type utilized to jettison or displace conventionally-known environmental seals. Furthermore, as seal pieces 46(a) and 46(b) remain attached to the munition body, little to no debris is produced by deployment of canard 40 through scribed frangible seal 46.
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 FIG. 10 at 72. In general, when a face bond is utilized in addition to or in lieu of a flexible edge bond, substrate 48 will fracture along multiple scribe lines and require a greater deploy force to initiate substrate fracture and allow the passage of a canard or other deployable element therethrough. However, while requiring the application of a larger deployment force, a face bond provides several advantages. For example, a face bond will tend to produce a more robust environmental seal between substrate 48 and guidance section shell 36. In addition, the lateral stand-off provided by a face bond assists with positioning substrate 48 and facilitates bonding during the assembly process. Thus, in embodiments wherein seal 46 is utilized in conjunction with larger form factor munitions capable of accommodating larger deploy springs, a face bond may be utilized, possibly in conjunction with scribe lines formed in opposing faces of substrate 48.
FIG. 11 is a flowchart illustrating an exemplary method 80 for equipping a guided munition with a scribed frangible seal, such as seal 46 described above in conjunction with FIGS. 3-10. Exemplary method 80 commences with the provision of a substrate, such as substrate 48 shown in FIGS. 3-10 (STEP 82). To commence method 80, a ceramic sheet may first be laser scribed and then broken, either mechanically or manually, into a plurality of individual substrates (STEPS 82(b) and 82(b)). The ceramic sheet may itself be produced utilizing fabrication by roll-compaction and sintering of a slurry containing ceramic particles. Scribes lines are then formed in at least one surface of the substrate utilizing, for example, a laser scribing process (STEP 82(c)). More specifically, as described above in conjunction with FIG. 3, a plurality of substantially parallel laser scribe lines may be formed in the outer surface of substrate such that each scribe line extends in a substantially longitudinal direction from an aft portion of the substrate to a forward portion thereof. The outer face of the substrate may or may not be polished or lapped after laser scribing. Next (STEP 84), the laser scribed seal is positioned over a deployment opening (e.g., a canard slot) provided in the body of a flight vehicle (e.g., a guided munition) such that at least one scribed surface of the seal resides substantially opposite the location at which a canard or other deployable element is housed within the flight vehicle body. As described above in conjunction with FIGS. 6 and 7, the laser scribed seal may be matingly positioned within a depression or recess provided in the munition shell. To complete method 80, the laser scribed seal may then be adhesively bonded to the flight vehicle body (e.g., the munition shell) utilizing a suitable bonding agent, such a high temperature silicone adhesive of the type described above (STEP 86). One or more cleaning agents or priming agents may also be applied prior to application of the selected bonding agent. A flexible edge bond of the type described above in conjunction with FIGS. 8 and 9 is advantageously employed to attach the substrate to the vehicle body. To minimize required human touch during the installation process, application of the bonding agent and primer, if utilized, may advantageously be performed utilizing an automated robot. After application of the bonding agent, a curing process may then be performed according to a pre-established curing scheduled to set the bonding agent and thereby form a robust environmental seal (e.g., a near-hermetic seal) between the substrate and the munition body. Lastly, to ensure adequate sealing of the deployment opening, inspection may be performed either visually or utilizing a suitable inspection tool or technique, such as a pressure test.
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.

Claims

What is claimed is:

1. A flight vehicle, comprising:

a vehicle body having a deployment opening therein;

a deployable element residing in a stowed position within the vehicle body and movable into a deployed position, at least a portion of the deployable element passing through the deployment opening when moving from the stowed position into the deployed position; and

a scribed frangible seal sealingly disposed over the deployment opening and positioned so as to be contacted by the deployable element during deployment thereof, the scribed frangible seal fracturing 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.

2. A flight vehicle according to claim 1 wherein the scribed frangible seal comprises a rigid substrate bonded to the vehicle body.

3. A flight vehicle according to claim 2 wherein the scribed frangible seal further comprises a plurality of scribe lines formed in at least one surface of the rigid substrate.

4. A flight vehicle according to claim 3 wherein the plurality of scribe lines comprises a plurality of scribe lines formed in an outer face of the rigid substrate substantially opposite the location at which the deployable element contacts the rigid substrate during deployment.

5. A flight vehicle according to claim 3 wherein the plurality of scribe lines extends in a substantially longitudinal direction from a forward portion of the rigid substrate to an aft portion thereof.

6. A flight vehicle according to claim 5 wherein the plurality of scribe lines comprises a plurality of substantially parallel scribe lines each extending in a direction substantially parallel with the longitudinal axis of the flight vehicle.

7. A flight vehicle according to claim 3 wherein the plurality of scribe lines comprises a plurality of laser scribe lines formed in an outer face of the rigid substrate.

8. A flight vehicle according to claim 7 wherein each of the plurality of laser scribe lines comprises a series of blind holes formed in the outer face of the rigid substrate.

9. A flight vehicle according to claim 7 wherein the rigid substrate is fabricated from a ceramic.

10. A flight vehicle according to claim 9 wherein the rigid substrate is fabricated from alumina.

11. A flight vehicle according to claim 3 further comprising a depression formed in the vehicle body and at least partially surrounding the deployment opening, at least a portion of the rigid substrate disposed within the depression.

12. A flight vehicle according to claim 11 wherein the depression is formed in an external surface of the vehicle body, and wherein the rigid substrate is matingly received within the depression in its substantial entirety.

13. A flight vehicle according to claim 11 further comprising a flexible edge bond joining at least a portion of the circumferential edge of the rigid substrate to at least one surface of the vehicle body defining the depression.

14. A flight vehicle according to claim 13 wherein the rigid body fractures into at least two longitudinally-extending pieces when contacted by the deployable during deployment thereof, and wherein the two longitudinally-extending pieces each rotate about the flexible edge bond to permit movement of the deployable element from the stowed position to the deployed position.

15. A flight vehicle according to claim 1 wherein the flight vehicle comprises a guided munition, wherein the vehicle body comprises a munition body, wherein the deployable element comprises a canard, and wherein the deployment opening comprises a canard slot.

16. A scribed frangible seal for sealing a deployment opening through which a deployable element deploys, the scribed frangible seal comprising:

a ceramic substrate; and

at least one laser scribe line formed in a surface of the ceramic substrate and imparting the ceramic substrate with a predetermined rupture strength, the ceramic substrate fracturing along the at least one laser scribe line during deployment of the deployable element.

17. A scribed frangible seal according to claim 16 wherein at least one laser scribe line comprises a plurality of laser scribe lines formed in a surface of the ceramic substrate, the plurality of laser scribe lines defining at least one longitudinally-extending fault line along which the ceramic substrate fractures when contacted by the deployable element during deployment thereof.

18. A scribed frangible seal according to claim 16 wherein the deployment opening is formed through a structure, and wherein the scribed frangible seal further comprises a flexible edge bond adhesively coupling a circumferential portion of the ceramic substrate to the structure.

19. A method for equipping a flight vehicle with a scribed frangible seal, the flight vehicle including a vehicle body configured to house a deployable element when in a stowed position, the vehicle body having 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, the method comprising:

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.

20. A method according to claim 19 wherein the step of obtaining a scribed frangible seal comprises:

laser-scribing a ceramic sheet to define a plurality of rigid substrates;

breaking the ceramic sheet to separate at least one rigid substrate from the plurality of rigid substrates; and

laser-scribing an outer face of the rigid substrate to yield the scribed frangible seal.