Abstract:
A system is provided for directing a flow of gas, including a launching mechanism, a plenum, a layer of meltable material, and an open-ended uptake component. The launching mechanism is adapted to expel rocket exhaust gas. The plenum includes an upper portion having at least one fire resistant breachable plug. The upper portion is adjacent to the launching mechanism. The layer of meltable material is disposed on the upper portion. The heat generated by the gas melts the layer of meltable material. The open-ended uptake component operatively connects to the plenum. The plug moves onto a lower portion of the plenum due to force generated by the gas onto the plug, and the gas flows through the plenum and the uptake component to vent said gas in a controlled manner.

Description:
STATEMENT OF GOVERNMENT INTEREST 
     The invention described was made in the performance of official duties by one or more employees of the Department of the Navy, and thus, the invention herein may be manufactured, used or licensed by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor. 
    
    
     BACKGROUND 
     1. Technical Field 
     The embodiments herein generally relate to weapons systems, and, more particularly, to equipment used for protection against the exhaust gases of missile launching systems. 
     2. Description of the Related Art 
     A vertical launching system (VLS) consists of a number of cells for holding and firing missiles on surface ships and submarines used by many navies around the world. Typically, each cell can hold a number of different types of missiles, enabling the ship flexibility to load an appropriate set for a given mission and to enable replacement of earlier missiles with upgrades without expensive rework. When the command is given, the missile flies straight up long enough to clear the cell and the ship, and then turns on course. The most popular VLS system in the world is the MK 41, being used by eleven navies around the world. The United States Navy will employ the MK 57 VLS on the U.S.S. Zumwalt class destroyers. 
     Both MK 41 and MK 57 VLS missile launchers primarily are configured as a plenum and uptake type gas management system. A plenum is a pressurized chamber holding fluids, and the uptake refers to the general upwards/vertical venting of pressurized gas from the plenum. These systems manage gases during a normal missile launch and also during retrained firing. However, a typical plenum and uptake approach results in substantial structural wear caused by normal missile launches, which decreases the ability to withstand a restrained firing, thus, limiting the number of missiles that can be launched prior to gas management system refurbishment. 
     The MK 41 and MK 57 VLS gas management system plenums protect their plenum floors with ablative material. Additional protection is provided underneath the rocket motor by using a bi-layer ablative material stack. The material on top of the stack is exposed to the rocket motor plume during normal missile fly outs, and the material on the bottom of the stack is exposed only during a missile restrained firing. However, the material is generally inadequate to prevent burn-through when exposed to plume jetting and long burn times because the ablative material, which tends to be expensive, typically do not have sufficient mechanical strength to resist the forces produced by the plume impingement. 
     The Mk 41 VLS gas management system also uses an aft closure, grid, and sill. The aft closure is a square multi-material, multilayer plate that has diagonal scores that allow it to “blow open” during a rocket motor firing. The sill keeps the aft closure from opening too far and the grid prevents the adjacent aft closures from opening in the opposite direction. However, this type of system requires a substantial number of components, the aft closure layup uses many different materials and a very process-intensive assembly, and the sill and grid are relatively difficult to manufacture and assemble. Moreover, this system is not readily adaptable for use on a general plenum box assemblies because it requires more space above the top of the plenum and more intrusion into the inside of the plenum. 
     SUMMARY 
     Therefore, it is desirable to develop an improved gas management system that utilizes the plenum and uptake configuration and is readily adaptable in current weapon systems at reduced cost and complexity. In view of the foregoing, an embodiment herein provides a system for directing a flow of gas, including a launching mechanism, a plenum, a layer of meltable material, and an open-ended uptake component. In various exemplary embodiments, the launching mechanism is adapted to expel rocket exhaust gas. 
     In various exemplary embodiments, the plenum includes an upper portion having at least one fire resistant breachable plug. The upper portion is adjacent to the launching mechanism. The layer of meltable material is disposed on the upper portion. The heat generated by the gas melts the layer of meltable material. The open-ended uptake component operatively connects to the plenum. The plug moves onto a lower portion of the plenum due to force generated by the gas onto the plug, and the gas flows through the plenum and the uptake component to vent said gas in a controlled manner. 
     These and other aspects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following descriptions, while indicating preferred embodiments and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the embodiments herein without departing from the spirit thereof, and the embodiments herein include all such modifications. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The embodiments herein will be better understood from the following detailed description with reference to the drawings, in which: 
         FIG. 1  illustrates a schematic diagram of a gas management system; 
         FIG. 2  illustrates a schematic diagram of a missile launcher attached to a gas management system; 
         FIG. 3  illustrates a schematic diagram of a gas blast protector; 
         FIG. 4  illustrates a cross-sectional diagram of the gas blast protector of  FIG. 3  attached to a plenum of a gas management system; 
         FIG. 5A  illustrates a cross-sectional diagram of a breachable plenum plug gas management system in a closed state of operation; 
         FIG. 5B  illustrates a magnified cross-sectional view of the encircled area ‘A’ of the breachable plenum plug gas management system of  FIG. 5A ; 
         FIG. 5C  illustrates a cross-sectional diagram of a breachable plenum plug gas management system in an open state of operation; and 
         FIG. 6  is a flow diagram illustrating a method according to an embodiment herein. 
     
    
    
     DETAILED DESCRIPTION 
     The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein. 
     The embodiments herein provide a gas management system that utilizes the plenum and uptake configuration to provide protection from the deleterious effects of a rocket plume. Referring now to the drawings, and more particularly to  FIGS. 1 through 6 , where similar reference characters denote corresponding features consistently throughout the figures, there are shown preferred embodiments. 
       FIG. 1  illustrates a schematic diagram of a gas management system  10 , which includes a plenum  15  connected to an uptake component  20  having an open end  25  to permit venting of gas that travels through the plenum  15  and then up through the uptake component  20 . The gas management system  10  protects surrounding personnel and equipment from the harmful effects of a restrained firing for missile launcher systems that are ordinarily not specifically designed to withstand or protect against the effects of hot missile exhaust gases. Positioned inside the plenum  15  is a gas blast protector mechanism  30 , which is described in further detail below with reference to  FIG. 3 . The view illustrated in  FIG. 1  is a cut through view of the plenum  15  in order to illustrate the positioning of the gas blast protector mechanism  30 . However, the plenum  15  is generally configured as a box-type configuration with walls extending around all sides to prevent the inadvertent discharge of gas in an uncontrolled manner. 
       FIG. 2 , with reference to  FIG. 1 , illustrates a schematic diagram of a missile launcher  35  adjacent to a gas management system  10 . As shown, the missile launcher  35 , which houses or otherwise connects with a rocket/missile (e.g., rocket/missile  43  shown in  FIG. 4 ) is connected to both the plenum  15  and uptake component  20  through a plurality of connecting mechanisms  40 , and the embodiments herein are not restricted to any particular type of connecting mechanism or configuration. The missile launcher  35  is in close proximity to the plenum  15 , which causes the exhaust gas from the launched rocket/missile to be directed upon the plenum  15  at elevated temperatures. 
       FIG. 3 , with reference to  FIGS. 1 and 2 , illustrates a schematic diagram of a gas blast protector mechanism  30  comprising a plate  31  and a plurality of raised bumps  32  extending from the plate  31 . The plate  31  and bumps  32  may be made from a variety of mechanically strong materials including ceramics. As described below, the gas blast protector mechanism  30  may or may not be utilized with respect to the embodiments herein. As shown in  FIG. 4 , with reference to  FIGS. 1 through 3 , the plate  31  is placed on the lower portion (i.e., floor)  16  of the plenum  15 . 
     In  FIG. 4 , the various block arrows depict the flow of gas as a result of a rocket/missile  43  being launched. The initial exhaust gas  45  purges the upper portion  17  (i.e., ceiling) of the plenum  15  and then extends downward through the inner chamber  18  of the plenum  15 . Thereafter, upon contacting the gas blast protector  30 , the gas is diverted in a substantially horizontal direction in relation to the plenum  15  such that the diverted gas  50  flows through the chamber  18  and then through the connecting uptake component  20  (not shown in  FIG. 4 ) to be vented in a controlled manner. The gas blast protector  30  assists in reducing the mechanical and thermal impact of the gas  45  on the floor  16  of the plenum  15 , thereby aiding in the maintenance of the structural integrity of the floor  16  of the plenum  15 . In other words, the gas blast protector  30  protects the floor  16  of the plenum  15  from burning through when exposed to the direct impingement of hot missile exhaust gas  45 . As mentioned above, the gas blast protector  30  is an optional component of the embodiments herein. 
       FIGS. 5A through 5C , with reference to  FIGS. 1 through 4 , illustrate various cross-sectional diagrams of a breachable plenum plug gas management system  10   a .  FIG. 5A  illustrates the system  10   a  in a closed state of operation while  FIG. 5C  illustrates the system  10   a  in an open state of operation.  FIG. 5B  illustrates a magnified cross-sectional view of the encircled area ‘A’ of the breachable plenum plug gas management system  10   a  of  FIG. 5A . 
     As illustrated, the gas management system  10   a  includes a plenum  15  having an upper portion  17  with a plurality of breachable (i.e., movable) plugs  55   a ,  55   b ; a lower portion  16 ; and a chamber  18  separating the upper portion  17  from the lower portion  16 . The system  10   a  also includes an uptake component  20  operatively connected to the plenum  15 . In an optional embodiment, at least one gas blast protection component  30  (not shown in  FIGS. 5A through 5C ) may be positioned over the lower portion  16  of the plenum  15 . The plurality of breachable (i.e., movable) plugs  55   a ,  55   b  move in a direction from the upper portion  17  towards the lower portion  16  upon impact of rocket motor exhaust gas  45  directed thereon. 
     As shown in  FIG. 5B , the plugs  55   a ,  55   b  may incorporate a tapered shape or alternatively may comprise a stepped shape (not shown). While these two shapes/configurations are described with respect to the plugs  55   a ,  55   b , the embodiments herein are not restricted to a particular geometric configuration of the plugs  55   a ,  55   b , as any type of configuration that permits breach of the plugs  55   a ,  55   b  is permitted. Additionally, the system  10   a  further includes a layer of meltable material  60  over the upper portion  17  of the plenum  15 , and a layer of fire resistant material  65  under the layer of meltable material  60 . In one embodiment, the material used for the layer of fire resistant material  65  is the same material used for the plugs  55   a ,  55   b . Thus, the plugs  55   a ,  55   b  are fire resistant, and the release of the plug  55   a  is dictated by the force of the exhaust gas  45  rather than the heat generated by the gas  45 . 
     The layer of fire resistant material  65  may be configured to be substantially aligned with the plugs  55   a ,  55   b . Due to the fire resistant qualities of the plugs  55   a ,  55   b , the floor  16  of the plenum  15  is protected from the deleterious effects of the gas  45  without the need of a gas blast protector  30 . Additionally, once the plug  55   a  hits the lower portion  16  of the plenum  15 , the plug  55   a  provides the same gas diversion quality as the raised bumps  32  of a gas blast protector  30 . However, should additional protection of the floor  16  of the plenum  15  be desired, then the embodiments herein may incorporate a gas blast protector  30  in the plenum  15 . The uptake component  20  comprises a first open end  21  connected to the plenum  15  and a second open end  25  to permit controlled venting of the gas  50 . 
     The plugs  55   a ,  55   b  move in substantially one direction only (i.e., generally in the direction from the upper portion  17  to the lower portion  16  of the plenum  15 ). The discharged plug  55   a  caused by the hot missile exhaust gas  45  creates an opening  19  in the upper portion  17  of the plenum  15  located directly underneath the exhausting rocket motor (e.g., rocket/missile  43  of  FIG. 4 ). However, non-discharged plug  55   b  as well as the layer of fire resistant material  65  prevents exhaust gas  45 ,  50  from leaking back underneath adjacent non-exhausting rocket motors (not shown). When the plug  55   a  underneath the exhausting rocket motor functions (i.e., is released), the rocket motor exhaust gas  45  flows into the inner chamber  18  of the plenum  15  and is ducted away to a safe location (e.g., through the uptake component  20 ). However, the non-exhausting rocket motors (not shown) are protected from the hot gases, due to the non-breached adjacent plug  55   b  preventing sympathetic rocket motor ignition. 
     Accordingly, since the non-exhausting rocket motors do not direct hot gas  50  onto plug  55   b , then the plug  55   b  remains in place in the upper portion  17  of the plenum  15  without breaching. Therefore, only plug  55   a  is breached because a rocket is launched directly above this location of the upper portion  17  of the plenum  15 . The gas  45  directed onto the plenum  15  first strikes the layer of meltable material  60  over the upper portion  17  of the plenum  15 . 
     The heat capacity of the meltable material  60  is less than the temperature of the gas  45  thereby causing the material  60  to melt, which then allows the gas  45  to strike the plug  55   a  at a force sufficient to cause the plug  55   a  to dislodge from the upper portion  17  of the plenum and down towards the lower portion  16  of the plenum  15 . The layer of fire resistant material  65  restrains the gas  45  from causing the breach of adjacent plug  55   b  and to maintain the structural integrity of the remaining areas of the upper portion  17  of the plenum  15 . The meltable material  60  and the fire resistant material  65  of the plugs  55   a ,  55   b  are not restricted to particular materials and need only be dictated by the thermal environment. 
     The system  10   a  protects a launcher  35  and surrounding equipment from the effects of a restrained firing even though the launcher  35  was not necessarily designed to mitigate a restrained firing. Due to the use of the fire resistant material  65 , the gas management system  10   a  does not wear out due to the number of missile firings occurring. 
     By utilizing the plugs  55   a ,  55   b  and multi-layered  60 ,  65  upper portion  17  of the plenum  15 , the embodiments herein achieve higher mechanical strength by combining the meltable material  60  and the heat resistant material  65 . This is because meltable materials are plentiful and can be selected for higher strength, whereas heat-resistant materials are more specialized and typically weaker mechanically. Furthermore, the plugs  55   a ,  55   b  are relatively easy to machine due to the materials that they constitute, which reduces manufacturing costs. 
     The embodiments herein also permit the redirection of the exhaust gases  45 ,  50  such that their detrimental effects on structural components (i.e., plenum  15 ) are mitigated. The embodiments herein require fewer components and fewer materials than conventional gas management systems because the system  10   a  utilizes a less complex configuration by requiring less room above and inside the plenum  15  (e.g., the embodiments herein do not require an additional gas blast protector  30 ). This is because, the system  10   a  does not use a grid, and since a sill is also not required, there are no required extraneous flow inhibiting items protruding into the plenum  15 . 
     While various material descriptions are described herein, the gas management system  10   a  may be made from a number of materials for the structural as well as the heat resistant aspects of the design. The materials used for the system  10   a  can be chosen based on mechanical strength under high heating rates and long burn time, ease of machining, ease of availability, and cost. 
       FIG. 6 , with reference to  FIGS. 1 through 5C , is an exemplary flow diagram  70  illustrating a method according to an embodiment herein. At step  71 , exhaust gas  45  from a missile&#39;s rocket motor  43  is directed to an upper portion  17  of the plenum  15  having fire-resistant breachable plugs  55   a ,  55   b . At step  72 , an upper layer of meltable material  60  melts in response to heat generated by the gas  45  in conjunction with step  73  of disposing a fire-resistant material  65  under the meltable material  60 . At step  74 , the plugs  55   a ,  55   b  are aligned with the fire-resistant material  65 . At step  75 , the plugs  55   a ,  55   b  are pushed down by the exhaust gas  50  being positioned directly above. At step  76 , the gas  50  is directed through the plenum  15  towards an uptake component  20  for venting. 
     The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the appended claims.