Abstract:
The apparatus of the present invention utilizes the heat energy of a weapon propulsion system to produce a vapor explosion. It includes an outer shell with a nozzle port and a body being made from a metal. The body surrounds a propulsion device and captures its waste heat to heat metal within the body. An explosive device is embedded in the body and can explode on transmission of a signal whereby the heated metal within the body produces a vapor explosion that significantly enhances the effectiveness and lethality of the weapon. The apparatus also discloses a second metal in the body and a heat shield for further enhancing effectiveness.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is a divisional of U.S. patent application Ser. No. 10/901,312, filed Jul. 22, 2004 now U.S. Pat. No. 7,067,732. 

   STATEMENT OF GOVERNMENT INTEREST 
   The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention generally relates to an apparatus that uses waste heat generated by a weapon propulsion system to produce a vapor explosion. 
   2. Description of the Related Art 
   Prior art rocket powered torpedoes are generally configured as shown in  FIG. 1 . Torpedo  10  travels through ambient fluid (e.g. ocean water)  12  in the direction indicated by arrow  14 . Rocket casing  16  houses a rocket (not shown) and is in direct contact with ambient fluid  12  at the aft of torpedo  10 . Thrust is produced by expelling gas through nozzle  18 . The rocket produces waste heat that is dissipated by forced convection over the rocket casing  16  and the discharge of the exhaust into the ambient fluid  12 . The remaining portion of torpedo  10  is constructed in sections and has a homing array (not shown) located in nose section  20 , electronics section  22 , warhead section  24  and exercise section  26 . These sections are typically separated by bulkheads  28 ,  30 ,  32  and  34 . Torpedo  10  also has an outer shell  30  which does not extend over rocket casing  16  in order to facilitate heat transfer of heat generated by the rocket to ambient fluid  12 . In other configurations, a heat shield (not shown) is added to bulkhead  34  in order to prevent overheating of the forward sections of torpedo  10 . Warhead section  24  contains high explosives that are detonated at the end of the torpedo&#39;s run (i.e. mission termination) in order to produce an explosion of which the most destructive effects are a shock wave and a vapor bubble. The amount of waste heat generated by the rocket is a considerable portion of the total energy contained in the rocket fuel. What is needed is an apparatus and method for utilizing the waste heat generated by the weapon&#39;s propulsion system to enhance the lethality of the weapon. 
   The prior art discloses several weapon propulsion systems and devices in Jenkins, U.S. Pat. No. 4,406,863; Short, U.S. Pat. No. 4,680,934; Hartman et al., U.S. Pat. No. 5,070,786; Duva, U.S. Pat. No. 5,253,473; Buzzett et al., U.S. Pat. No. 5,728,968; Woodall et al., U.S. Pat. No. 6,308,607; and Longardner, U.S. Pat. No. 6,400,896. However, such prior art systems do not utilize waste heat generated by the weapon propulsion system to enhance the lethality of the weapon. 
   SUMMARY OF THE INVENTION 
   It is therefore an object of the present invention to provide an apparatus can be integrated into a weapon and which significantly enhances the lethality of the weapon. 
   It is another object of the present invention to provide an apparatus that is integrated into a weapon and utilizes the heat from the weapon&#39;s propulsion system to produce a secondary explosion upon termination of the weapon&#39;s mission. 
   Other objects and advantages of the present invention will be apparent from the ensuing description. 
   Thus, the present invention is directed to an apparatus for utilizing waste heat from a weapon&#39;s propulsion system to increase the lethality of the weapon. Specifically, the present invention stores waste heat and coverts such waste heat into kinetic energy at the termination of the weapon&#39;s travel. The apparatus of the present invention effects storage of heat instead of exchanging the heat with ambient fluid as is done with prior art weapon propulsion systems. The stored heat is then used to melt and ultimately superheat metal. The detonation of the weapon warhead will scatter the molten metal in the presence of ambient fluid thereby resulting in a secondary vapor explosion. The secondary vapor explosion enhances the effectiveness and lethality of the weapon. 
   In one aspect, the present invention is directed to an apparatus for utilizing the waste heat energy of a weapon propulsion system to produce a vapor explosion. The apparatus comprises a metal structure having a body portion fabricated from a first metal having a first predetermined melting temperature, and a plurality of layers fabricated from a second metal embedded within the body portion and spaced apart from each other. The second metal has a second predetermined melting temperature that is less than the first predetermined melting temperature such that the second metal melts and attains superheat before the first metal. The body portion has a space sized to receive a propulsion device such that the body portion envelopes a substantial portion of the propulsion device. The space in the body portion has an opening from which an exhaust nozzle of the propulsion device can extend. The apparatus further includes an explosive device embedded in the body portion, and an electrical link connected to the explosive device to detonate the explosive device. The electrical link extends from the body portion. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing features of the present invention will become more readily apparent and may be understood by referring to the following detailed description of an illustrative embodiment of the present invention, taken in conjunction with the accompanying drawings, in which: 
       FIG. 1  is a side-elevational view, partially in cross-section, of a prior art torpedo; 
       FIG. 2  is a cross-sectional view of the apparatus of the present invention; and 
       FIG. 3  is a side-elevational view of a weapon containing therein the apparatus of the present invention, the view showing an outer portion of the weapon being cut away to facilitate viewing of a ventilation system and weapon control module inside the weapon. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring to  FIG. 2 , there is shown a partial view of a weapon  40  that utilizes apparatus  42  of the present invention. Weapon  40  can be a torpedo or similar weapon that travels through a liquid medium such as ocean water. Weapon  40  has bulkhead  43  that separates apparatus  42  from the other sections of the weapon. Apparatus  42  comprises outer shell  44  that cooperates with bulkhead  43  to form a chamber or compartment  45 . Chamber  45  has a port  46  through which a propulsion exhaust device, such as a rocket nozzle  66 , can extend. This feature is further described in the ensuing description. Outer shell  44  has seams  50 ,  52 ,  54  and  56  that will easily rupture when exposed to an internal explosion. Apparatus  42  comprises metal structure  60  that envelopes a substantial portion of a propulsion device of weapon  40 . Metal structure  60  is described in detail in the ensuing description. The propulsion device includes rocket casing  62  and rocket  64  which is housed within rocket casing  62 . Rocket  64  includes nozzle  66 . In order to enhance the effectiveness and efficiency of apparatus  42 , rocket casing  62  is preferably fabricated from a metal that has an extremely high melting point and good thermal conductivity to maximize radiation of waste heat therefrom. Suitable metals for fabricating rocket casing  62  include titanium; however, other suitable metals having the desired melting temperature and thermal conductivity can be used as well. Although weapon  40  is described as utilizing a rocket-type propulsion system, it is to be understood that apparatus  42  can be used with other types of weapon propulsion systems. 
   Referring to  FIG. 2 , in accordance with the invention, apparatus  42  further includes heat shield  70  that is positioned between metal structure  60  and outer shell  44 . Heat shield  70  extends over aft bulkhead  43 . Heat shield  70  may be fabricated form a variety of ceramic and evacuated layers. Heat shield  70  holds the waste heat generated from rocket  64  within compartment  45 . Thus, heat shield  70  effects an increase in temperature in compartment  45  which enhances the effectiveness and efficiency of apparatus  42  as will be explained in the ensuing description. 
   Referring to  FIG. 2 , metal structure  60  comprises body portion  80  that is fabricated from a first metal that does not react with water (i.e. non-reactive), and a plurality of layers  82  formed of a second metal that does react with water (i.e. reactive). This two metal structure  60  gives some benefit during a short weapon run while maintaining structural integrity. After a longer run more of the body portion  80  will become molten. Layers  82  are embedded in body portion  80  and are spaced apart. In one embodiment, layers  82  are generally parallel to one another or concentric. Body portion  80  is configured to envelope rocket casing  62 . In a preferred embodiment, some of layers  82  are embedded in body portion  80  in such a manner these layers  82  contact rocket casing  62 . Metal structure  60  can be configured to have any type of shape, square, circular, etc. In a preferred embodiment, metal structure  60  occupies substantially all the available space within the confines of heat shield  70 . Layers  82  can be arranged and positioned within body portion  80  in any one of a variety of geometrical arrangements. In one embodiment, layers  82  are arranged so as to generally form a matrix. The number of layers  82  can be varied depending upon the particular application and the desired magnitude of the vapor explosion. As shown in  FIG. 2 , metal structure  60  has explosive device  90  embedded therein. Electrical link  92  is connected to explosive device  90 . Electrical link  92  can be a wire or cable that is capable of carrying electrical voltage signals. Electrical link  92  extends from metal structure  60 , heat shield  70  and bulkhead  43  through appropriate sized bores, channels or openings (not shown). Electrical link  92  is electrically connected to weapon control module  100  (see  FIG. 3 ). Upon mission termination, weapon control module  100  emits an electrical signal that detonates explosive device  90 . In a preferred embodiment, heat shield  94  is positioned between explosive device  90  and metal structure  60  in order to thermally isolate explosive device  90 . 
   Referring to  FIG. 2 , in accordance with the invention, the melting temperatures of the metals forming body portion  80  and layers  82  are significantly less than the melting temperature of the metal used to fabricate rocket casing  62 . In accordance with the invention, the melting temperature of the metal forming body portion  80  is greater than the metal temperature of the metal that forms each of layers  82 . Thus, the metal forming layers  82  will melt and reach superheat before the metal forming body portion  80 . Suitable metals for layers  82  include lithium, magnesium, sodium, potassium, and lead. Such suitable metals include metals that will physically react with water by causing flash boiling, and metals that will cause an explosive chemical reaction upon contact with water; however, other suitable metals can be used as well. Suitable non-reactive metals for body portion  80  include aluminum and steel alloys. However, other suitable non-reactive metals can be used as well. At ambient temperature and at weapon launch, the metals used to form body portion  80  and layers  82  are in the solid state. 
   Referring to  FIG. 2 , the manner in which apparatus  42  is kept inert depends upon the type of metals used to fabricate body portion  80  and layers  82 . For example, if the metal used to form body portion  80  is aluminum and the metal used to form layers  82  is magnesium, then apparatus  42  can be kept in inert if apparatus  42  is kept cool. In another example, if the metal used to form body portion  80  is aluminum and the metal used to form layers  82  is lithium, then apparatus  42  can be kept inert if apparatus  42  is kept dry. 
   Referring to  FIGS. 2 and 3 , during operation of weapon  40 , rocket  64  is fired to provide weapon thrust. Weapon  40  typically includes weapon control module  100 , deployable cavitator  102 , and ventilation system  104 . Weapon control module  100  outputs an electrical signal over electrical link  92  to detonate explosive charge  90  upon termination of the mission. The configuration of weapon  40 , as shown in  FIG. 3 , allows weapon  40  to operate in ventilated cavity  106 . Ventilated cavity  106  has a cavity closure point  108  that is located downstream of exhaust plume  110 . As weapon  40  travels though a liquid medium (e.g. ocean water), the waste heat generated by rocket  64  and transferred by rocket casing  62  causes the temperature of metal structure  60  to increase. Heat shield  70  facilitates increase of the temperature of metal structure  60 . Operation of weapon  40  in ventilated cavity  106  facilitates further increase in temperature of metal structure  60 . As a result, the temperature of the metals forming body portion  80  and layers  82  quickly increase and approach superheat as the weapon mission time (e.g. torpedo run-time) increases. Since the melting temperature of the metal forming layers  82  is less than the metal forming body portion  80 , layers  82  melt first and become a superheated liquid or molten metal. This superheated liquid or molten metal is extremely volatile. For example, if the metal forming body portion  80  is aluminum and the metal forming layers  82  is lithium, even a relatively short weapon mission time would cause complete melting of the lithium layers  82  due to the relatively low melting temperature of lithium, 179 degrees Celsius. However, if the weapon mission time is relatively long, melting and superheating of both the lithium and aluminum would occur. At termination of the weapon&#39;s mission, weapon control module  100  generates an electrical signal on electrical link  92  that detonates explosive charge  90 . The explosion of explosive charge  90  explodes metal structure  60  and ruptures seams  50 ,  52 ,  54  and  56  of outer shell  44  thereby causing a rapid introduction of the liquid or molten metal into the liquid medium (e.g. ocean). The interaction of the liquid or molten metal with the liquid medium produces several vapor explosions and chemical reactions that produce shock waves, vapor bubbles, and molten metal shrapnel. These vapor explosions are in addition to the main explosion caused by the warhead carried by the weapon. 
   Although a particular embodiment of the invention has been described, it is to be understood that modifications and other embodiments are possible. For example, the details of metal structure  60  can be varied. Instead of having layers  82 , body portion  80  can be made from a single metal. The metals used in metal structure  60  can be varied depending upon the thermal properties of rocket  64  and the expected time for completion of the weapons&#39; mission. Non-reactive metals such as steel alloys can be used to maximize effectiveness of the weapon when impact with a relatively large surface target is required. Apparatus  42  can be used with or without a conventional warhead. Thus, apparatus  42  can be operated without a conventional warhead, thereby relying only on the impact of the weapon on the target and the vapor explosion so as to control or minimize the amount of damage done to a target. Metal structure  60  can be configured to be used with a conventional non-rocket powered weapon. Apparatus  42  can be configured to have a protective sub-compartment that envelopes metal structure  60  to prevent contact of the liquid or molten metal with heat shield  70 . 
   Thus, apparatus  42  of the present invention provides many advantages. Specifically, apparatus  42  significantly enhances the lethality of the weapon with which it used. The vapor explosion created by apparatus  42  at mission termination significantly enhances the effectiveness of the weapon against large surface targets (e.g. ships or other vessels) as well as multi-hulled vessels. Explosive charge  90  does not require any special arming device or arming procedure and simply relies on an electrical signal from weapon control module for detonation. 
   The principles, preferred embodiments and modes of operation of the present invention have been described in the foregoing specification. The invention which is intended to be protected herein should not, however, be construed as limited to the particular forms disclosed, as these are to be regarded as illustrative rather than restrictive. Variations in changes may be made by those skilled in the art without departing from the spirit of the invention. Accordingly, the foregoing detailed description should be considered exemplary in nature and not limited to the scope and spirit of the invention as set forth in the attached claims.