Patent Publication Number: US-9851188-B2

Title: Decoupling assembly for a plumbing network

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a division of U.S. application Ser. No. 12/545,494, filed Aug. 21, 2009, now U.S. Pat. No. 8,578,855. 
    
    
     TECHNICAL FIELD 
     The present embodiments relate generally to pressure vessels and, more particularly, to rocket motor tubes, having features that decouple to vent pressure when the vessel is subjected to excessive temperatures. 
     BACKGROUND 
     Some pressure vessels, including munitions, may be inherently dangerous. Due to those potential inherent dangers, and the grave effects an accident or unplanned incident involving munitions can have, the U.S. Government has promulgated insensitive munitions standards (“IM Standards”) to ensure that munitions operate safely and predictably. These standards require munitions—ammunition, rockets, missiles, explosives, or their shipping containers—to reliably fulfill performance, readiness, and operational requirements on demand, while minimizing the hazards of inadvertent initiation triggered by excessive temperature. Rockets are an example of munitions that must comply with U.S. Government IM standards. 
     A rocket motor is a pressure vessel that is propelled by a rearward discharge of gas generated by the combustion of propellant inside the motor. A rocket motor typically includes a casing or motor tube, frequently called a combustion chamber, partially filled with combustible material, and an exhaust nozzle. The combustible material at fuels the rocket is typically a single liquid or solid propellant, but can a combination of combustible materials and oxidizers. 
     When designed to comply with IM standards, rockets are expected to (1) enhance survivability by reducing the potential for collateral damage to logistic and tactical combat systems, (2) minimize accidental personnel injury, and (3) provide for more cost effective and efficient transport, storage and handling. IM standards set forth tests and test procedures to assess the safety and characteristics for all non-nuclear munitions, munitions subsystems, and explosive devices, including rockets. 
     Until now, efforts to design rockets that satisfy IM standards have had limited success. Some attempts involved designing a rocket motor that includes an insensitive munitions charge. For example, Solberg et al. in U.S. Pat. No. 6,619,029 disclose an insensitive munitions charge located inside of the motor casing to auto-ignite and release gas at a temperature below the primary propellant grain auto-ignition temperature. Other attempts have involved an ordnance venting system. For example, Kim et al. in U.S. Pat. No. 6,363,855 disclose a deflagrating composition with a high energy material that detonates during cook-off to rupture the ordnance housing to relieve pressure. Still other attempts have involved a thermoplastic warhead adapter. For example, Kim et al. in U.S. Pat. No. 6,338,242 disclose a thermoplastic adapter that is fitted over a dome plug located in a vent hole of the motor casing that melts away at elevated temperatures to relieve pressure. 
     While these and other efforts to design munitions and rockets that satisfy mandated IM standards have been made, those efforts have not created munitions that fully satisfy the need for both reliable operation and cost effective production. There remains a need to provide munitions with improved features that potentially enhance safety or that reliably meet IM standards. 
     SUMMARY OF THE EMBODIMENTS 
     In a first exemplary embodiment, a decoupling assembly is provided. The decoupling assembly may be used in munitions. It may include a rocket motor tube having an open end, the motor tube containing a temperature-sensitive combustible material. The decoupling assembly may further include a mount incorporating a seat for a flexible seal to close and seal the open end of the motor tube, and a joint between the motor tube and the mount. The joint may be configured and dimensioned to allow the mount to decouple from the motor tube and comprises a material that softens when exposed to predetermined temperatures. 
     In another exemplary embodiment, a vessel is provided. The vessel may include a body defining an internal cavity, the cavity containing a temperature-sensitive material. The vessel may further include an insert and a material forming a joint between the body and the insert. The material may create a conditionally secure attachment, where the joint permits the insert to become displaced from the body when external temperatures cause the pressure inside the vessel to increase, thereby allowing the contents to escape in a controlled manner and the pressure to be reduced. 
     In another exemplary embodiment, a decoupling assembly is provided that may be installed in a plumbing network containing temperature sensitive material. The decoupling assembly may include a housing having an open end. The decoupling assembly may further include an insert closing the open end of the housing, the insert comprising a seat adapted to receive a seal, and a joint between the insert and the housing, the joint being configured and dimensioned to receive a material that softens at a predetermine temperature to allow the insert to decouple from the housing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Advantages of the exemplary embodiments will be apparent to those of ordinary skill in the art from the following detailed description and the accompanying drawings, in which like reference numerals are used to indicate like elements: 
         FIG. 1  is a cross-sectional side view of a rocket motor, according to one embodiment of the present disclosure. 
         FIG. 2  is a front end view of a motor tube, according to one embodiment of the present disclosure. 
         FIG. 3  is a perspective view of the cross-section of a portion of a rocket motor with safety features, according to one embodiment of the present disclosure. 
         FIG. 4  is a cross-sectional view of a seal between a motor tube and an insert, according to one embodiment of the present disclosure. 
         FIG. 5  is a side view of the cross-section of a portion of a motor tube, according to one embodiment of the present disclosure. 
         FIG. 6  is a portion of a side view of the cross-section of a portion of a motor tube, according to one embodiment of the present disclosure. 
         FIG. 7  is a perspective view of an insert for a motor tube, according to one embodiment of the present disclosure. 
         FIG. 8  is a cross-sectional view of a portion of the joint constructed in a motor tube, according to one embodiment of the present disclosure. 
     
    
    
     DESCRIPTION 
     The following description conveys an understanding of embodiments that relate generally to vessels, such as munitions, and more particularly to a rocket motor having features that relieve pressure when subjected to excessive temperature and/or a predetermined temperature. Numerous exemplary embodiments of vessels having features that comply with IM standards are described below. Rockets, and other munitions, described by the exemplary embodiments that meet IM standards are not limited to only those embodiments, however. For example, exemplary embodiments may be used for temperature dependent decoupling in devices, machines, or vehicles outside of the munitions industry. The exemplary embodiments may be sized or shaped differently, in any suitable manner, and may be adapted to add components not described, or to remove components. One possessing ordinary skill in the art will appreciate the exemplary embodiments use for purposes and benefits in alternative forms and industries, depending upon specific design needs and other considerations. It will also be understood that embodiments are not required to satisfy IM Standards and may be designed to satisfy alternative standards, or may be used in applications without required standards. 
     Terminology used in this description is for describing particular embodiments only and is not intended to limit the scope of an exemplary embodiment. As used throughout this disclosure, the singular forms “a,” “an,” and “the” include the plural, unless the context clearly dictates otherwise. Thus, for example, a reference to “a seal” includes a plurality of seals, or other equivalents or variations known to those skilled in the art. Furthermore, if in describing some embodiments or features permissive language (e.g., “may”) is used, that does not suggest that embodiments or features described using other language (e.g., “is,” “are”) are required. Unless defined otherwise, all terms have the same commonly understood meaning that one of ordinary skill in the art to which this invention belongs would expect them to have. 
     The accompanying figures and following description depict and describe exemplary embodiments of a vessel with features that decouple the structure of the vessel when subjected to excessive temperatures and/or a predetermined temperature. These features are believed sufficient to satisfy IM Standards, but such satisfaction is not a requirement of all exemplary embodiments. As used throughout this description, the term “rocket” or other like terms is meant to encompass any vessel designed with the features described herein. But, the exemplary embodiments may also be used in any munitions, devices, machines, or vehicles, regardless of whether they are specifically designed to comply with IM standards. The vessels are not limited to any specific embodiment or detail that is disclosed. 
     With regard to the exemplary embodiments of the rocket motor tube described below, any part that fastens, inserts, attaches, or connects any component to or from the rocket motor tube is not limited to any particular type and is instead intended to encompass all known and conventional fasteners, like screws, nut and bolt connectors, threaded connectors, snap rings, detent arrangements, clamps, rivets, toggles, and so on. Fastening may also be accomplished by other known fitments, like leak-tight seals or sealing devices. Components may also be connected by adhesives, polymers, copolymers, glues, welding, ultrasonic welding, and friction fitting or deformation. Any combination of these fitment systems can be used. 
     Unless otherwise specifically disclosed, materials for making components of the present invention may be selected from appropriate materials, such as metal, metal alloys, natural or manmade fibers, composites, vinyl, plastics, silicone, rubber, and so on. Any and all appropriate manufacturing or production methods, such as casting, pressing, extruding, molding, machining, may be used to construct the exemplary embodiments or their components. 
     When describing exemplary embodiments, any reference to relative position (front and back or rear, top and bottom, right and left, upper and lower, and so on) is intended to conveniently describe those embodiments only. Positional and spacial references do not limit the exemplary embodiments or its components to any specific position or orientation. 
     As shown in  FIG. 1 , an exemplary motor tube  100  for a rocket is depicted. Attached to the rear end of the motor tube  100  may be a nozzle  102 . As is known in the art, the nozzle  102  may have fins  104 , or any other directional stabilizing component, attached to it. In one embodiment, the nozzle  102  may be a converging-diverging nozzle and extend rearwardly from the motor tube  100 . The nozzle  102  may be a conical, ideal, or bell nozzle but is not limited to any particular shape, number of parts or components, or overall construction. The nozzle  102 , and its components, such as the fins  104 , may be made of a metallic material that is removably or permanently attached to the motor tube  100  by a lockwire or any other known or suitable means. The nozzle  102  may act as the primary means through which gas produced in the motor tube  100 , sometime referred to as a combustion chamber, is permitted to escape, generating thrust. Although a rocket&#39;s performance can be highly dependent on the particular design and shape of a nozzle, any rocket nozzle, such as the rocket nozzle  102  shown in  FIG. 1 , or a plurality of nozzles, may be used in other embodiments. 
     In the exemplary embodiment, the motor tube  100  may be an elongated, tubular body having a constant or varying diameter. The motor tube  100  may serve has a housing or body for containing a combustible material. The motor tube  100  may comprise a single, integral tube structure but can alternatively be formed from multiple pieces or components joined together. The motor tube  100  may be machined, formed, or otherwise constructed to meet particular specifications. For example, the motor tube  100  may have a specific length, outside diameter, wall thickness(es), inside diameter, straightness, or surface finish. In an exemplary embodiment, the motor tube  100  may have a length of about 37.25±0.25 in., an outside diameter of about 2.750 in., a wall thickness of about 072+0.004/−0.002 in., an inside diameter of about 2.6060±0.0060 in., a mean of the maximum and minimum diameters of about 2.6060±0.0045, and a minimum surface finish of about 125 μin. Of course, these dimensions can be substantially different depending of the type of munitions or rockets being manufactured. As mentioned above, the motor tube  100  may be constructed of multiple pieces or components, and in that embodiment, each piece or component may have identical or different measurements. 
     The tube  100  may be constructed from a metallic material. In one embodiment, the motor tube  100  may comprise a rigid tube of aluminum, specifically aluminum alloy 7075 (“Alloy 7075”). Alloy 7075 is one of the 7XXX series alloys frequently used in aircraft, aerospace, and munitions structures and components. Alloy 7075 is an Al—Zn—Mg—Cu high strength alloy having the beneficial effects of chromium to develop good stress-corrosion cracking resistance in sheet products. Alloy 7075 is available in bare and alclad sheet and plate product forms, and in the annealed state as well as several tempers of the T6, T73 and T76 types. 
     In the exemplary embodiments above, the motor tube  100  is described as being an aluminum alloy. This, however, is an exemplary embodiment only. The motor tube  100  may be made of any suitable material, including other aluminum alloys, or other high-strength and corrosion-resistant materials, like stainless steel, magnesium, titanium, composites, fiber reinforced composites, plastics, and so on. The motor tube  100  may further comprise one or more internal components  110  that are known in the art, such as a spring, heat shield, igniter assembly, and so on. 
     Referring to  FIGS. 1 and 2  the motor tube  100  has a front end  202  and a rear end (not shown). The rear end may provide an interface with which the nozzle  102 , as described above, is attached by any suitable means. The front end  202  may provide an interface within which an insert (described below) is attached. 
     Referring to  FIG. 3 , the front end  202  of the motor tube  100  may have an insert  300  attached thereto. The insert  300  may be inserted concentrically inside of the motor tube  100  so that the outside face of the insert  300  contacts the inside face of the motor tube  100 . The insert  300  may be generally cup-shaped with a front end  302  and a rear end. The insert  300  may further comprise a base  306  from which a sidewall  308  extends axially towards the front end  302 . The sidewall  308  may terminate in a common plane with the front end  202  of the motor tube  100 . Further, the sidewall  308  may have a tapered end  331  that mates with a corresponding seat  334  near the front end of the motor tube  100 . It should be understood, however, that either the sidewall  308  or the front end  202  may terminate in a more forward plane than the other. The sidewall  308  may be of any suitable thickness. In another embodiment, the insert  300  may be adapted to be received over the motor tube  100 . 
     The insert  300  may be adapted to receive a warhead (not shown). As different tactical requirements may demand different types of warhead. The insert  200  may be designed such that any suitable warhead may be attached to the motor tube  100 . The insert  300  may comprise a number of threads  314  formed on the inside surface of the sidewall  308  for receiving a warhead. Such constructions are well known in the art. Other constructions may be used, however, to attach a warhead to the insert  300 , such as screws, nut and bolt connectors, threaded connectors, snap rings, detent arrangements, clamps, rivets, toggles, seals or sealing devices. 
     In the exemplary embodiments, the insert  300  may be constructed of any suitable material. For example, the insert  300  may be the same material as the motor tube  100 , such as Alloy 7075, or it may be any other material, including material that is dissimilar from that used for the motor tube  100 . 
     As mentioned above, the insert  300  includes the base  306 . The base  306  may comprise a seal seat  310  formed on its bottom surface as an annular ring to receive a seal  312 . The seal  312  may sit inside or partially inside the seal seat  310 . Referring to  FIG. 4 , the seal  312 , in one, embodiment, may be a piston U-cup seal. The seal  312  has a u-shaped groove  320  formed in such a manner that a seal is made by inside and outside sealing lips  504 . The inside, and outside sealing lips  504  contact the inside sidewall of the seal seat  310  and the inside wall of the motor tube  100 , respectively. The seal  312  may be designed with differently shaped sealing lips  504 . For example, the U-cup seal may have a shorter, heavier outside sealing lip to achieve a higher initial sealing force on the motor tube  100 . The seal  312  is supported by the bottom surface of the seal seat  310 . In an exemplary embodiment, the seal  312  may be designed to withstand up to 5000 psi, but it is not so limited and the seal  312  may be designed to withstand any pressure depending on expected operating conditions. 
     The seal  312  may be produced using a variety of flexible materials, typically polymers or elastomers, made with a variety of geometries. For example, the seal  312  may be manufactured in a variety of geometries, in a range from 2″-8″ outside diameter, using fluorocarbon, polyacrylate, ethylene acrylic, or other polymers. The seal  312  may be manufactured using precision cutting processes, casting, molding, or other manufacturing methods well known in the art. Of course, the geometry and material used for the seal  312  may be varied to ensure an appropriate sealing contact. One skilled in the art can determine the appropriate type, design, and material needed for the seal  312  depending on the expected temperatures and pressures, and other operating conditions. Further, the seal  312  may be made with any suitable hardness and fluid compatibility. 
     In another embodiment, the seal seat  312  may be formed in and around the outer circumference of the base  306 , as opposed to being provided in the shown seal seat  310 . It should be noted, however, that any type of construction may be used to create a sealing mechanism or the base  306  itself may be constructed to create a suitable seal. The base  306  may be any suitable thickness. Moreover, the seal  312  may be substituted with any type of sealing mechanism, such as a lip seal, mechanical seal, o-ring, shaft seal, two-part seal, or any other suitable seal. Such seals are well known in the art. 
     Referring to  FIG. 6 , the motor tube  100  may include a joint  330 . The joint  330  provides a mechanism by which a vessel, such as a rocket motor tube, can decouple when the vessel is subjected to excessive temperatures and/or a predetermined temperature. In an exemplary embodiment, the joint  330  may soften to allow the insert  300  to decouple from the motor tube  100 . The joint  330  may be used in pressurized or non-pressurized vessels. In other words, the joint  300  may allow the insert  300  to decouple before or after a vessel becomes pressurized. Furthermore, the present embodiments may be used in normally pressurized vessels. 
     The joint  330  may be formed between the insert  300  and the motor tube  100  to securely retain the insert  300  in place. The motor tube  100  and the insert  300  may be constructed with one or more circumferential grooves or projections or reliefs in the form of annular rings  332  to receive a material, which serves to conditionally secure the insert  300  to the motor tube  100 . Alternatively, the motor tube  100  and the insert  300  may have a stub ACME thread form to engage the material into the joint  330 . The one or more annular rings  332  may be formed to provide a slot-like void for injecting the material. In one embodiment, the joint  330  may have eight annular rings. One of ordinary skill in the art can readily determine the number, width, and depth of annular rings needed to alter the shear area of the bonded joint as needed to provide the retention strength needed for a given application. 
     In another embodiment, as described above, the insert  300  may be adapted to be received over the motor tube  100 . In other words, the insert  300  may serve as a mount to the motor tube  100 . In that embodiment, the joint  330  may be inverted such that the joint  330  may be formed on the outside of the motor tube  100 . 
     To create the joint  330 , a material, including a wide range of natural and synthetic materials suitable, may be injected. In one embodiment, the material may be plastic or polymer, such as a high density polyethylene (HDPE) resin. This thermoplastic may have a variety of compositions, including additives or fillers. For example, the joint  330  may comprise a chemically coupled HDPE resin reinforced with glass fiber. 
     Table 1 shows an exemplary HDPE resin used in the joint  330 : 
     
       
         
           
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 HDPE resin 
               
               
                   
               
             
            
               
                 PROPERTIES &amp; AVERAGE VALUES OF 
               
               
                 INJECTION MOLDED SPECIMENS 
               
            
           
           
               
               
            
               
                   
                 ASTM 
               
            
           
           
               
               
               
               
            
               
                   
                 English 
                 SI Metric 
                 TEST 
               
               
                   
                   
               
            
           
           
               
            
               
                 PERMANENCE 
               
            
           
           
               
               
               
               
            
               
                 Primary Additive 
                 40% 
                 40% 
                   
               
               
                 Specific Gravity 
                 1.26 
                 1.26 
                 D 792 
               
            
           
           
               
               
               
               
               
               
            
               
                 Molding 
                   
                   
                   
                   
                   
               
               
                 Shrinkage 
               
            
           
           
               
               
               
               
               
            
               
                 ⅛ in (3.2 mm) 
                 0.0020-0.0030 
                 in/in 
                 0.20-0.30% 
                 D 955 
               
               
                 section 
               
            
           
           
               
            
               
                 MECHANICAL 
               
            
           
           
               
               
               
               
               
               
            
               
                 Impact Strength, 
                   
                   
                   
                   
                   
               
               
                 Izod 
               
               
                 notched ⅛ in 
                 3.0 
                 ft-lbs/in 
                 160 
                 J/m 
                 D 256 
               
               
                 (3.2 mm) section 
               
               
                 unnotched ⅛ in 
                 15.0 
                 ft-lbs/in 
                 801 
                 J/m 
                 D 4812 
               
               
                 (3.2 mm) section 
               
               
                 Tensile Strength 
                 9000 
                 psi 
                 62 
                 MPa 
                 D 638 
               
            
           
           
               
               
               
               
            
               
                 Tensile 
                 4.0-5.0% 
                 4.0-5.0% 
                 D 638 
               
               
                 Elongation 
               
            
           
           
               
               
               
               
               
               
            
               
                 Tensile Modulus 
                 1.25 × 10{circumflex over ( )}6 
                 psi 
                 8619 
                 MPa 
                 D 638 
               
               
                 Flexural Strength 
                 13500 
                 psi 
                 93 
                 MPa 
                 D 790 
               
               
                 Flexural Modulus 
                 1.00 × 10{circumflex over ( )}6 
                 psi 
                 6895 
                 MPa 
                 D 790 
               
            
           
           
               
            
               
                 THERMAL 
               
            
           
           
               
               
               
               
               
               
            
               
                 Ignition 
                   
                   
                   
                   
                   
               
               
                 Resistance* 
               
               
                 Flammability** 
                 HB @ 1/16 
                 in 
                 HB @ 1.5 
                 mm 
                 D 635 
               
               
                   
               
            
           
           
               
            
               
                 PROPERTY NOTES 
               
               
                 Data herein is typical and not to be construed as specifications. 
               
               
                 Unless otherwise specified, all data listed is for natural or black colored 
               
               
                 materials. Pigments can affect properties. 
               
               
                 *This rating is not intended to reflect hazards of this or any other material 
               
               
                 under actual fire conditions. 
               
               
                 **Values per RTP Company testing. 
               
            
           
           
               
            
               
                 GENERAL PROCCESSING FOR INJECTION MOLDING 
               
            
           
           
               
               
               
               
            
               
                   
                   
                 English 
                 SI Metric 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
            
               
                 Injection Pressure 
                 10000-15000 
                 psi 
                 69-103 
                 MPa 
               
               
                 Melt Temperature 
                 380-450° 
                 F. 
                 193-232° 
                 C. 
               
               
                 Mold Temperature 
                 70-150° 
                 F. 
                 21-66° 
                 C. 
               
               
                 Drying 
                 2 hrs @ 175° 
                 F. 
                 2 hrs @ 79° 
                 C. 
               
               
                   
               
            
           
         
       
     
     It should be understood that one of ordinary skill in the art can determine the crystallinity, molecular weight, and other chemical and physical properties depending on the maximum and minimum operating or exposure conditions of the motor tube  100 . Alternatively, the HDPE resin, or other plastic or material, may be reinforced with another substance, such as basalt fiber, carbon black, clay, talc, calcium carbonate, mica, silica, or silicate, or other suitable fillers. The material used in the joint may also comprise any suitable non-plastic material. 
     As described above, the motor tube  100  and insert  300  may be constructed with annular rings  332  to receive an injected material, such as an HDPE resin. In one embodiment, eight annular rings may be formed to distribute the load in the HDPE as the internal pressure of the motor tube  100  changes. This helps ensure that the insert remains securely in place during normal operation. 
     One or more injection ports  106  may be machined into the motor tube  100  at any suitable location so that material, such as HDPE, may be injected into the annular rings; for example, two injection ports  106  of about 0.1 inch diameter may be used and located 180° apart and about 1.5 in, from the front end  202  of the motor tube  100 . 
     Referring to  FIG. 5 or 6 , the annular rings  332  may be constructed, formed, machined, or molded along the outer surface of the insert  300  and/or the inner surface of the motor tube  100 . In one embodiment, the annular rings are aligned crest-to-crest, so that the roots align and fill with the largest possible amount of continuous material. In other words, the motor tube  100  and the insert  300  may comprise one or more reliefs projecting into a surface thereof. 
     Each of the annular rings  332 , formed as distinct elongated grooves, define a slot-like void between the insert  300  and the motor tube  100 . As noted above, the annular rings  332  provide a space for the injected material to flow into and solidify, thus establishing the joint  330  between the insert  300  and motor tube  100 . As shown for example in  FIG. 7 , the plurality of annular rings  332  may be formed as distinct elongated grooves spaced equi-distantly around the circumference of the insert  300 . The annular rings  332  may be arranged, however, as continuous grooves around the circumference of the insert  300 . The annular rings may further be formed with an angle on each ring cut, referred to as angled cuts  802 , as shown in  FIG. 8 . The angled cuts  802  help to ensure proper compression of the material injected between the motor tube  100  and the insert  300 . The angle cut  802  on each annular ring  332  may be configured to optimize joint performance. 
     In alternative embodiments, the shape, orientation, depth, and placement of the annular rings  300  may be varied. If necessary, symmetrically and asymmetrically spaced and shaped cavities, notches, pockets, grooves, and so on may be used. Alternatively, any other orientation, positional and spacial relationship can be used, such as a staggered arrangement in the radial or axial direction. The foregoing arrangement may be desirable to ensure that the injected material securely joins the insert  300  inside of the motor tube  100 . 
     In an exemplary embodiment, the annular rings  332  may be placed at a predetermined distance from one another, and a predetermined distance from the seal  312 . Referring back to  FIG. 5 , a length L t , as measured from the seal  312  to the nearest annular ring  332 , may be about 0.01 in. to about 1 in., more preferably about 0.79 in. Of course, these distances can be changed as certain designs may dictate. 
     Referring to  FIG. 5  and  FIG. 7 , the motor tube  100  and insert  300  may further comprise one or more axially aligned grooves  500 . The one or more axial grooves  500  serve as an anti-torque feature to help ensure that the insert  300  does not rotate and remains securely attached to the motor tube  100  as the warhead is being screwed in place or removed. The one or more grooves  500  may be designed to meet certain warhead installation and removal requirements. For example, the grooves  500  may be designed to meet a requirement to withstand about 55±20 ft-lb and may be designed to withstand repeated warhead installations and removals. The grooves  500 , however, can be designed to any specific requirement. In one embodiment, the motor tube  100  may have twelve axially aligned grooves  500 , or channels, machined between the distinct elongated grooves that comprise the annular rings  300 . In an exemplary embodiment, the grooves  500  length L g  measured of about 0.25 in. to about 1 in., more preferably about 0.53 in. These axial grooves  500  may also provide a fluid path between the annular rings  332  to help facilitate thorough implantation of the injected material. 
     A vessel, once fully assembled in accordance with the present embodiments, preferably has features that fulfill performance requirements but also can reduce the risk that the vessel explodes when it is subjected to excessive temperatures and/or a predetermined temperature. One objective of a rocket assembled according to the present embodiments is to relieve the vessel before the auto-ignition temperature of the propellant contained within the rocket is reached. This occurs as the joint  330 , as described above, reaches a predetermined temperature and softens prior to reaching the auto-ignition temperature of the propellant, causing the insert  300  to decouple from the motor tube  100 . While this function is preferred, it is not a necessary feature of all embodiments. The predetermined temperature or temperature range at which the joint softens may be varied depending on the material used in the joint  330  and/or the material used as the propellant. One skilled in the art can readily determine what temperature or temperature range at which the insert  300  will decouple from the motor tube  100 . 
     In certain circumstances, it may be important motor tubes to pass certain tests, such as a hydroburst test, static fire test, vibration test and slow cook-off test (e.g., a test at temperatures above 300° F.) to ensure compliance with different specifications. One or more of those tests or others may be necessary to comply with IM standards. As such, exemplary embodiments may satisfy one or more requirements in addition to decoupling the insert  300  before reaching the auto-ignition temperature. For example, it has been found that exemplary embodiments configured as a Mk66 motor have been able to satisfy the additional tests identified above by demonstrating that the Mk66 motor reduced the explosive results when the propellant reached slow cook-off temperatures above 300° F., while still meeting the performance requirements to function as a rocket motor. 
     This disclosure describes exemplary embodiments of vessels, including munitions and rocket motor tubes, that have features to relieve pressure when subjected to excessive temperatures and/or a predetermined temperature. Those embodiments may be used in a rocket system, such as a 2.75″ rocket motor and warhead system. However, it will be understood that the foregoing embodiments may be used in any rocket motor tube, warhead system, pressure vessel or in other devices, machines, or vehicles outside the munitions industry. Additionally, it will be understood that these and other embodiments are capable of use in various other combinations and environments and can be changed or modified without departing from the scope of the appended claims.