Selectable lightweight attack munition
FIELD OF THE INVENTION 
     This invention relates to portable munitions such as hand grenades, pocket mines, and similar munitions. 
     REFERENCE TO RELATED APPLICATIONS 
     This application is related to the following commonly assigned applications filed concurrently herewith: 
     
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Title                   Ser. No.                                          
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Self-Sterilizing Safe-Arm                                                 
                        07/256,445                                        
Device with Arm/Fire Feature                                              
Safety Locking Pull Ring                                                  
                        07/256,444                                        
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     BACKGROUND OF THE INVENTION 
     This invention is an overall portable munition system having an electronic control portion, mechanics for activation and providing either safing or arm/firing and a warhead. This munition provides for multiple modes of operation utilizing selectable inputs to obtain any of a plurality of outputs. 
     SUMMARY OF THE INVENTION 
     A compact portable explosive munition utilizes electronics for performing computations, timing, selecting inputs and outputs utilizing digital logic contained on a gate array along with additional electrical components to provide input and output signals matched to the gate array along with tests and switching functions not achievable by gate circuitry. A multistep arm fire procedure, a safing or self-sterilizing procedure, a comprehensive self-test procedure, and multiple operating modes, mine, tripline, or time delay, are provided. The modes are switch selected. 
     This apparatus also provides boresight and off boresight aiming capability, a stowed tripline for tripline firing, and an alternate mode of firing the munition using a blasting cap before or after the munition has been self-sterilized. 
     A captive ring must be freed and used to rotate a bar to free one end of a safety wire and to energize a battery to power the electronics as first steps in firing the munition. The ring and associated parts were the subject of a commonly assigned copending application discussed earlier. 
     A rotor which can be either translated or rotated by explosive piston actuators which are fired by electrical currents controlled by the electronic computation, provides additional safety features for either arming and firing or in safing the munition. This rotor was also the subject of a separately commonly assigned copending application and discussed earlier. 
     A main charge explosive is used to form and hurl a warhead projectile. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1: Electronics block diagram 
     FIG. 2: Functional block diagram 
     FIG. 3: Munition perspective showing external features 
     FIG. 4: Munition perspective showing blasting cap receptacle 
     FIG. 5: Bottom view of munition 
     FIG. 6: Exploded view of munition 
     FIG. 7: Electronic Data Flow/Computation Block Diagram 
     FIG. 8: Indicator Circuit 
     FIG. 9: Firing Circuit 
     FIG. 10: Tripline and switch schematic 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Overview of Munition Operation: 
     An electronics block diagram of the munition is shown in FIG. 1. Battery 42 provides power for the entire system. The system mode of operation is determined by selector switch 248 and whether a tripline is deployed to activate switch 258 or not. Inputs vehicle detection 266 and anti-disturbance switch 254 are selected by the mode of operation. Control electronics 200 uses a custom gate array to provide timing functions, logic functions, and all other control requirements. Firing circuits 244 fire the explosive pistons to operate the munition. Indicator light 47 indicates a functional and safe condition to the operator. 
     In FIG. 2 a functional block diagram utilizing these and other electronic elements along with mechanical elements of the overall munition are shown. This diagram includes elements from two other copending applications referred to earlier. Reference numbers of identical parts or elements of these applications have the same reference numbers here. The process of unlatching ring 12, then using the ring to pull and rotate activation bar 16 to energize battery 42, the observation of indicator light 47 to determine whether to secure the end of safety wire 36 with clip 21 or remove the wire are covered in a copending patent application on a safety locking pull ring. 
     Prior to energizing indicator light 47, control electronics 200 must perform a successful self-check routine and only after successful completion of the self-check routine is the indicator light energized. Control electronics 200 also reads the status of selector switch 248, tripline switch 258, monitors motion of munition itself with antidisturbance switch 254, monitors vehicle presence with vehicle detection block 266 and tests for low voltage. As mentioned, the operating mode of the system is determined by the states of selector switch 248 and tripline switch 258 which states are used by control electronics 200 to select the proper input signals, set the mode of operation, and set the timed event. When control electronics 200 determines that it is time to enable it sends an electrical signal to piston actuator 110 which unlocks the rotor and enables the arm/fire mechanism. When control electronics 200 determines that self-sterilization is required it sends an electrical signal to piston actuator 114 which fires the detonator to translate the rotor and extend post 102. When control electronics 200 determines that main charge 66 should be fired, an electrical signal is sent to piston actuator 112 to rotate the rotor, which fires the detonator which fires transfer lead 64, which in turn fires main charge 66, also shown in FIGS. 3, 4, 5, and 6. The operation of safe and arm/fire mechanism 60, shown in dashed outline, is covered in a copending application on self-sterilizing safe arm device with arm/fire feature. 
     This overview describes the mechanical and electrical interrelationship between the two copending patents and this apparatus which cooperate to provide the complete sequence of operations for the munition. 
     In FIG. 3, two boresight holes 310 are shown, both of which extend completely through munition 10, to permit aiming main charge 66 by sighting through either of these holes. Reflecting surface 312 is set at a 45 degree angle with respect to the warhead 66 axis of projection and with respect to hole 314. This arrangement permits using hole 314 to aim warhead 66 by looking through hole 314 when the munition is mounted with holes 310 not accessible for sighting. A tripline mounted within housing 316 in munition 10 is used in a tripline mode of operation to be discussed later. Selector switch 248 has an exposed selector knob to allow the operator to set in the various system parameters. Switch 248 and the tripline condition are used by the operator to program munition 10 prior to use. 
     Selector switch 248 is a rotary switch which has eight labeled settings. These settings are 4, 10, 24, 15, 30, 45, 60, and `S.` When either 4, 10, or 24 is set this provides a self-sterilize time delay of that many hours. These numbers are color coated light green on a white background. When either 15, 30, 45, or 60 is set this provides a firing time delay of that many minutes. These numbers are color coded red on a white background. The `S` is a safe setting and is white on a green background. The safe setting is provided to prevent compete activation of the electronics and is processed as a self-check failure. Tripline switch 258 is a single pole double throw switch wired before deployment with one contact open and one contact closed which is reversed when the tripline is deployed. Control electronics 200 reads this change as an indication that tripline 316 is activated. A pull on a tripline 318 of FIG. 10 after this deployment results in the switch being tripped to the state before deployment which is interpreted as a fire command in the tripline mode discussed later. In the following Table 1 the three modes of operation of the munition, namely, mine mode, tripline mode, and time delay mode are shown corresponding to the setting of selector switch 248 and the deployment of tripline switch 258. Logic in control electronics 200 interprets these switch settings and sets up the corresponding operational mode. 
     
                       TABLE 1                                                     
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FUNCTIONAL MATRIX                                                         
Operational Mode                                                          
            Trip Line Mode  Time                                          
                                      Delay                               
Conditions                                                                
        Mine Mode Self Sterilize                                          
                             Fire     Mode                                
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Selector                                                                  
        4, 10 or  4, 10 or   15, 30, 45 or                                
                                      15, 30, 45                          
Switch 248                                                                
        24 hours  24 hours   60 minutes                                   
                                      or 60                               
Setting                               minutes                             
Tripline                                                                  
        Inactive  Active     Active   Inactive                            
Switch 258                                                                
Setting                                                                   
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     The systems inputs and response for the operational modes specified by the switch settings are shown in Table 2. The system first becomes activated by the battery and is enabled approximately 60 second after activation. The system&#39;s inputs and operation for the various modes follow. 
     Mine Mode Operation, Self-Sterilize Time Out--4, 10, or 24 Hours 
     Vehicle detection block 266, shown in FIG. 2, has a magnetic pick-up, analog amplification, and logic elements to determine the passing of a vehicle. The output from vehicle detection block 266 is simply a binary one or zero. This is read by control electronics 200 only when in the mine mode. When the system is enabled a passing vehicle will fire the munition. 
     A change in state of tripline switch 258 will fire the munition in the mine mode after the system is enabled. This occurs because even though the primary mine mode input signal is vehicle detection block 266, a change in tripline switch 258 is interpreted as an attempt to tamper with the munition which causes the munition to fire regardless of the mode of operation. This is shown in Table 2 opposite the tamper input. 
     The munition will self-sterilize 4, 10, or 24 hours after activation, whichever time was set on selector switch 248 provided the vehicle detection 266 signal was not received within that length of time after the system was enabled. The munition will self-sterilize at any time after battery activation if a low voltage or timer error have occurred. 
     The munition will fire if tampering is detected by a change in selector switch 248 after the system is enabled as discussed earlier. 
     The munition will also fire if the munition is disturbed as indicated by antidisturbance switch 254 after the system is enabled. 
     
                                           TABLE 2                                 
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         Operational Mode                                                 
               Trip Line Mode Time                                        
System Inputs                                                             
         Mine Mode                                                        
               Self Sterilize                                             
                      Fire    Delay Mode                                  
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Vehicle  Fire  No Effect                                                  
                      No Effect                                           
                              No Effect                                   
Detection 266*                                                            
Tripline Inputs*                                                          
         Fire  Fire   Fire    Fire                                        
(Switch 258                                                               
Change)                                                                   
TIme Set Self  Self   Fire    Fire                                        
Expired  Sterilize                                                        
               Sterilize                                                  
Low Voltage                                                               
         Self  Self   Before 15 min.                                      
                              Before 15 min.                              
Detection                                                                 
         Sterilize                                                        
               Sterilize                                                  
                      Self Sterilize;                                     
                              Self Sterilize;                             
                      After 15 min.                                       
                              After 15 min.                               
                      Fire    Fire                                        
Timer Error                                                               
         Self  Self   Self    Self                                        
         Sterilize                                                        
               Sterilize                                                  
                      Sterilize                                           
                              Sterilize                                   
Tamper Input*                                                             
         Fire  Fire   Fire    Fire                                        
(Switch 248 or                                                            
258 Change)                                                               
Anti-Disturbance                                                          
         Fire  Fire   Fire    Fire                                        
Switch 254*                                                               
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 *Input read only after control electronics 200 has enabled system.       
 
    
     Antidisturbance switch 254 is a switch arranged to momentarily close whenever the munition is moved and provides a binary input which can be read by control electronics 200. This will be described further later. 
     Tripline Mode, Self-Sterilize Time-Out--4, 10, or 24 Hours 
     Vehicle detection block 266 is not read by control electronics 200 in this mode. Tripline switch 258 is the primary input and will fire the munition if a change in state of the tripline switch occurs. This change is interpreted as both the primary system input and also as a tamper input. 
     Control electronics 200 will self-sterilize the munition after the time set in switch 248, 4, 10, or 24 hours, has expired. The munition will also self-sterilize if a low voltage condition or timer error is detected. 
     Control electronics 200 will fire the munition if a tamper input, described earlier, or antidisturbance switch 254 signal occurs after system enable. 
     Tripline Mode, Fire Time-Out--15, 30, 45, or 60 Minutes 
     Vehicle detection block 266 is not read by control electronics 200 in this mode. A change in state of tripline switch 258 will fire the munition and be interpreted both as the primary system input and as a tamper input as in the self-sterilize tripline mode. 
     Control electronics 200 will fire the munition after the time set in switch 248, 15, 30, 45, or 60 mintues has expired. A low voltage condition will result in self-sterilization if the condition occurs before 15 minutes have elapsed and after 15 minutes have elapsed will result in the munition being fired. A timer error will result in the self-sterilization of the munition at any time. 
     A tamper input detection or antidisturbance switch 254 input will cause the munition to fire any time afer enable. 
     Time Delay Mode, Fire Time-Out--15, 30, 45 or 60 Minutes 
     Vehicle detection block 266 is not read by control electronics 200 in this mode. The antidisturbance switch 254 is not read by control electronics 200 in this mode. A change in state of tripline switch 258 will cause the munition to fire as a tamper input. The primary system input is a timing signal generated in control electronics 200 with the interval selected by the selector switch 248 setting. When the time set on selector switch 248, 15, 30, 45, or 60 minutes has expired the munition will fire. 
     A low voltage condition before 15 minutes have elapsed after activation will cause the munition to be self-sterilized and after 15 minutes will cause the munition to be fired. A time error at any time will cause the munition to be self-sterilized. 
     A tamper error after enable will cause the unit to fire. 
     Command Detonate Mode 
     A separate mode of operation is also available which does not utilize any of the previously described fuze portion of the system. This mode is available at any time before the munition is fired, including after the munition has self-sterilized, because the regular munition detonator is not used. This mode utilizes either a standard military electric or nonelectric blasting cap which fits within hole 250 and is seated within recess 230, shown in FIGS. 3, 4, and 6, and is secured in place by a flexible rubber collet 252 which fits within the hole. The recess 230 is adjacent to the transfer lead 64. When a blasting cap is set off in recess 230, whether electric or nonelectric, the transfer lead will fire which, in turn, will set off the main charge. 
     Control Electronics Inputs 
     In FIG. 7 control electronics block 200 along with the associated input and output circuits are shown. Oscillator 202 drives counter 204 and oscillator 206 drives counter 208. A fast check block 210 and slow check block 212 receive inputs from both of these counters and the results of these checks are fed to self-check block 214. Input processor block 216 receives inputs from selector switch 248 and tripline switch 258 and has outputs to fire/safe block 218. Antidisturbance switch 254 and vehicle detection 266 also have outputs to fire/safe block 218. Control electronics 200 provides logic to select the interconnections and functions shown in Table 2, described earlier, from the switch setting information shown in Table 1. 
     Oscillator 202 is reference for the clock of control electronics 200 while oscillator 206 provides a comparison check on the accuracy of oscillator 202. Both oscillators are quartz controlled oscillators with the same nominal frequency. This comparison will be covered in the self-check description. 
     Input processor 216 provides two general functions. It latches the state of the selector switch 248 and tripline switch 258 shortly after the system is energized to permit detecting any changes in the state of the input switches that may occur after the munition is enabled. In addition, a comparison is made of the input switches latched data to the input signals themselves immediately after these signals are latched. Any changes in these input switch states will generate the tamper signal, discussed earlier, which is sent to the fire/safe block 218. If this comparison indicates identical settings this shows that the inputs were successfully latched and constitutes one of the system self-checks. These switch conditions are binary coded signals from the selector switch which are decoded into discrete enable signals and sent to the fire control section. In this manner, all the information provided by the input switches is converted to the form used by other logic blocks. 
     Antidisturbance switch 254 utilizes timing and logic in block 218 which sends a fire signal whenever a disturbance is detected. 
     Vehicle detection 266 utilizes a coil 232, shown in FIG. 6, sensitive to magnetic field changes along with logic to accurately determine when a vehicle is passing by. A binary signal is sent to fire/safe block 218 whenever a vehicle is detected. 
     Control Electronics Functions 
     Counter 204 and counter 208 consist of a number of counter blocks with each block having six stages of ripple counters. Each block has six binary outputs with each successive output stage changing at one half the frequency of the previous output. A number of these blocks are connected together consecutively to provide all of the timing functions previously discussed. Any given time interval required by the system is obtained by monitoring the appropriate block and stage of counter 204 to obtain the time interval which is based upon the known oscillator 202 frequency. 
     Fast check 210 compares the frequency of signals from the oscillator 202 time base counter 204 to the frequency of signals from the oscillator 206 time base counter 208. This is done by comparing counts from each counter taken over the same time interval. If the difference between the frequencies is such that oscillator 202 is more than 10 percent faster than that of the oscillator 206 a signal is sent to the self-check block 214 and the fire/safe block 218. If this failure occurs immediately following system initialization the test will indicate a self-check failure. If this failure occurs after enable, the fire control section will indicate a timer error as in Table 2. 
     Slow check 212 is similar to the fast check block excepting that here if oscillator 202 is 10 percent slower than oscillator 206 a failure is indicated. This failure output also goes to both the self-check and fire control sections, and is treated the same as a fast check failure. 
     Self-check 214 performs the following self-checks as soon as the system is energized: 
     Oscillator 202 and oscillator 206 are tested to determine if they differ from each other by less than 10 percent. This process is performed by fast check 210 and slow check 212 as described. 
     Tests are performed to determine if the battery voltage is above 3 volts. A conventional voltage comparator determines this. A voltage which is equal to or less than 3 volts constitutes self-check failure. 
     The explosive piston actuator circuits are tested for missing or open circuited actuators. A test pulse is sent to the piston actuators through resistors to limit the current to a value which will not fire the actuators. The amount of voltage drop across the resistors in the circuits from control electronics 200 to each piston actuator is monitored by voltage comparators to determine if any piston actuator is missing or is open circuited. Either missing or open constitutes a self-check failure. 
     Tripline switch 258 contacts are checked to insure that one contact is closed and one contact is open. If both contacts are of the same state an error condition exists which constitutes a self-check failure. This utilizes the fact that tripline switch 258 has one pole and two contacts and the contacts should always have opposite states. 
     Selector switch 248 is read to determine whether or not it is set to safe. If the switch is set to safe a self-check failure is indicated and a signal is sent to discontinue the enable sequence. 
     The voltage across capacitors 272, FIG. 9, which provide energy for firing each piston actuator is tested to determine if the voltage is less than 0.6 volt using a voltage comparator. If the voltage across the capacitors exceeds 0.6 volt an error exists which constitutes a self-check failure. The significance of this voltage level will be discussed later in the fire circuit explanation. 
     The outputs to the fire and self-sterilize circuits are tested to determine if either is activated. If either is activated a self-check failure is indicated. 
     The status of selector switch 248 and tripline 258 are tested and compared with the latched value obtained at power up. Any differences in these readings indicate a self-check failure condition. 
     Control electronics 200 automatically enters the self-test routine once battery 42 has been energized. This self-check routine is completed in approximately 5 seconds. If all tests check out successfully, then indicator light 47 is turned on for 50 seconds at the end of which time the light is flashed on and off for 10 seconds after which time the light is turned off to indicate to the operator that the munition is enabled and in a condition to fire. A flashing indicator light is used to indicate to the operator that the munition will arm within ten seconds which allows him time to obtain a safe distance. If the self-check routine detects a failure then light 47 is never turned on and a resistor is connected across the battery to discharge it and terminate all electronics functions permanently. A fail safe design uses a lack of indication for a failure condition rather than an indicator output which prevents any failure in an indicator light or circuit itself from falsely indicating a safe condition. Only after indicator light 47 is turned on is safety wire 36 removed by the operator to commit the munition to either a self-sterilize or a firing mode of operation. This is normally done soon after light 47 comes on and within the 50 second interval but before it begins to flash. 
     Control Electronics Circuitry 
     A custom gate array logic chip is used in control electronics 200 to perform all the decoding and timing functions required as shown in Table 2 and described for FIG. 7. The outputs from control electronics 200 drive piston actuator firing circuitry and an indicator light circuit as shown in FIG. 2. These output circuits and certain other elements described earlier use electronic elements which are not provided by the gate array logic chip. These other elements have been described functionally and are readily available. On the gate array logic chip logic trees provide the selected input and output signals for the various modes as specified in Table 2. The binary count down chains described earlier are readily achievable on this size logic chip and provide all of the timing elements. All electronics elements are mounted on a printed circuit board 201 shown in FIG. 6. 
     Indicating light 47 circuit is shown in FIG. 8. Line 260 is connected to battery 42. Line 262 is connected to control electronics 200 as shown in FIG. 2 and 7. The resistors in this circuit and transistor 264 are selected to permit driving the light emitting diode as indicator light 47. 
     A firing circuit used in each of the three explosive piston actuators is shown in FIG. 9 with resistor 274 and firing capacitors 272 being common to the three circuits. Three of these circuits are provided between control electronics 200 and each piston actuator 110, 112, and 114 and are controlled by lines 278A, 278B, and 278C respectively and powered by line 273 as shown in FIGS. 2 and 7. These lines are represented by line 278 and line 273 in FIG. 9 as representative of all three circuits. Resistor 274 has a value which will permit charging capacitors 272 with line 273 when driven by a gate in control electronics 200 to provide the current source. While the current provided by a logic gate output is only on the order of a few milliamps, capacitors 272 integrate this energy to the level necessary to fire a piston actuator. Resistor 276 represents the electrical resistance of a bridge wire in each respective piston actuator used to fire the actuator. Fire output 278 represents the output control lines from three separate gates in control electronics 200 to each firing circuit 278A, 278B, and 278C for the piston actuators. 
     The resistors associated with transistor 268 and 270 are selected such that a gate output in control electronics 200 can drive the impedance between the emitter and collector of transistor 270 to a low value. When control electronics 200 determines that any given piston actuator should be fired the respective gate driving one of three lines 278A, 278B, or 278C is changed in state such that the selected transistor 270 has a low impedance from collector to emitter to permit capacitors 272 to discharge through resistor 276 and cause that respective piston actuator to fire. 
     During self-check no voltage is applied to line 273 from the gate in control electronics 200 and the voltage on charge output line 273 should be lower than 0.6 volt, which is the self-check test voltage, if the circuit elements are correct. 
     Tripline switch 258 is contained in a housing 316 shown in FIGS. 3 and 4. A schematic of tripline switch 258 is shown in FIG. 10. When cord 318 is unwound from bobbin 320 and the cord extended, the state of both contacts of tripline switch 258 is changed. One contact changes from closed to open and the other contact changes from open to closed. This is interpreted by the control electronics as tripline deployment as explained earlier. Cord 318 can be deployed alone or attached to another line for greater range. After tripline deployment a pull on cord 318 will change the state of tripline switch 258 back to the original state which is interpreted by the control electronics 200 as either a fire or a tamper input. 
     Main charge 66, shown in FIG. 6, and warhead liner 240 have matching concave cross-sections. Warhead liner 240 is made of metal. The concave shape of main charge 66 forms and hurls warhead liner 240 along the concave axis. A foam cover 242 provides a protective surface for the warhead liner 240. As discussed earlier, boresight holes 310 are used to align the axis of warhead liner 240 along a desired target path which is followed quite accurately by the warhead liner. 
     The automatic features provided by the built in control electronics block greatly simplify the operation of the munition mechanical interlocking arming procedures and provide fail safe tests, permit manual selection of a number of operating modes, and select the corresponding input and output circuits based only upon the selected states of two switches. 
     The use of a single indicator light to indicate successful self-testing, a flashing condition of the light to indicate imminent electronics enabling, the use of no indicating light illumination to indicate a failure condition, the use of an indicator light such that when it subsequently stays off indicates an enabled condition provides all necessary information using only a single indicator with no possibility of a circuit failure in that indicator circuit giving a false safe condition. 
     All the combined elements of the three applications making up this munition provide a sophisticated system which not only provides a number of electronically controlled modes of operation with resultant flexibility and accuracy but also provides a completely separate external mode of operation. This external mode is available even after the self-sterilization step which not only fires the detonator but provides a positive indication of this fact to permit personnel to safely approach the munition. 
     The electronics used is state of the art with conventional circuitry for input and output functions and a custom gate array for all other functions. The apparatus is compact and complete. 
     While this invention has been described with reference to an illustrative embodiment, this description is not intended to be construed in a limiting sense. Various modifications of the illustrative embodiment, as well as other embodiments of the invention, will be apparent to persons skilled in the art upon reference to this description. It is therefore contemplated that the appended claims will cover any such modifications or embodiments as fall within the true scope of the invention.