Abstract:
A fiber-optically-and-pneumatically-controlled firing set for explosive-bridgewire detonators. The firing set consists of a detonation-controlling module and a battery-operated firing module that are interconnected by fiber-optic signal conductors and a pneumatic conduit. The firing set provides high voltage isolation between the control module and the firing module while employing redundant safety features including fail-safe pneumatic crowbar shunting of the firing module output, frequency-selective fiber-optic signal communication, controlled battery life and explosive material detonation enablement and multiple, fail-safe serial switching to control the energy transfer sequence in the firing module. Both high voltage and low potential uses of the invention are included.

Description:
RIGHTS OF THE GOVERNMENT 
     The invention described herein may be manufactured and used by or for the Government of the United States for all governmental purposes without the payment of any royalty. 
     BACKGROUND OF THE INVENTION 
     In certain specialized situations there is need to employ an explosive charge device in a high voltage electrical environment. More precisely, in some instances it is desirable for an explosive charge device and its detonation/initiating apparatus to remain usable and safe from unintended detonation even though the device is arbitrarily and suddenly elevated in electrical potential from zero or ground potential to a potential of several hundred kilovolts or megavolts. The explosive charge device involved in this environment may be as small and as simple as an explosive bolt of the type often used in rocket and space applications or may be of a larger and more complex nature as needed for explosive disintegration of a larger apparatus or at least its key integration elements. The specialized situations needing this combination of explosive separation or disintegration may exist in certain military weapons environments, particularly in systems employing high-energy and/or high-voltage pulse forming networks or similar apparatus. Needs for this capability may also be found in the electrical utility field where it can be desirable to interrupt the connection between a high voltage source and its load in a simple, rapid, permanent and visible manner. Such disconnection may be appropriate between a transmission line and a transformer primary winding terminal for example. 
     To date, alternate arrangements having safe detonation/initiation functional capability in the presence of the dual hazards of high explosives and very high voltage are believed not to exist. Although standard explosive fuses, or chemical fuses, may be feasible for normal operation in these environmental conditions, such devices have irresolvable safety problems in an abort-or-misfire situation in, for example, a laboratory test requiring an experimental apparatus to be approached for repair or dismantling. 
     SUMMARY OF THE INVENTION 
     The present invention provides a safe and reliable apparatus and method for operating explosive-bridge-wire (EBW) detonators and associated explosive charges that are raised to electrical potentials of hundreds of thousands of volts or megavolts above a surrounding environment. The invention excludes metallic conductors in locations that could disturb electromagnetic fields or short-circuit electrical operating potentials. The invention method and apparatus also meet the safety requirements imposed in connection with explosive materials use in most test and operating environments and enables the safe handling of abort and explosive misfire situations. 
     It is therefore an object of the present invention to provide an explosive material detonation apparatus and method that are usable in a very high electrical voltage environment. 
     It is another object of the invention to provide an explosive material detonation arrangement that is also usable in ordinary low voltage or zero voltage environments. 
     It is another object of the invention to provide an explosive material detonation apparatus that is relatively simple in arrangement and operation. 
     It is another object of the invention to provide an explosive material detonation apparatus that is manually controlled while having automatic electrical and electronic supervision functions. 
     It is another object of the invention to provide an explosive material detonation controller allowing safe abortion of an embarked-upon detonation program from plural controller operating states. 
     It is another object of the invention to provide an explosive material detonation system combining fiber optic and pneumatic communication between two major system components. 
     It is another object of the invention to provide an explosive material detonation apparatus providing an armed and detonation-enabled period of finite and predictable duration. 
     It is another object of the invention to provide an explosive material detonation system having large stray electromagnetic signal immunity. 
     It is another object of the invention to provide an explosive material detonation arrangement that is inclusive of a plurality of safety operating features. 
     These and other objects of the invention are achieved by instantly segregable elevated electrical potential apparatus comprising the combination of: 
     an assembly joined together in an electrically insulated, local explosive material-detonation responsive manner; 
     a source of elevated electrical potential connected between said assembly and a surrounding environment electrical node; 
     an electrically initiateable charge of explosive material located adjacent portions of said elevated electrical potential assembly; 
     a quantity-limited depletable source of explosive material-detonation initiating electrical energy located adjacent said charge of explosive material, said quantity-limited source of explosive material-detonation initiating electrical energy being also disposed at said elevated electrical potential with respect to said surrounding environment; 
     a wired conductor path inclusive of a coded optical energy responsive electrical switching element connecting said quantity-limited source of explosive material-detonation initiating electrical energy with said electrically initiateable charge of explosive material; 
     said quantity-limited depletable source of explosive material-detonation initiating electrical energy, said wired conductor path, and said coded optical energy responsive electrical switching element comprising an explosive material firing module also disposed at said elevated electrical potential with respect to said surrounding environment; 
     a detonation controlling module coupled with said firing module by a multiple parallel path fiber optic optical energy signal transmission apparatus; 
     said multiple parallel path fiber optic optical energy signal transmission apparatus being also electrically non conducting with respect to said elevated electrical potential of said assembly; 
     said detonation controlling module including electrical circuit means defining a successive sequence plurality of detonation controlling module and firing module operating states including an initial off state, a final state initiating detonating of said electrically initiateable charge of explosive material and a plurality of intermediate operating states; 
     said detonation controlling module and said firing module including optical signal transmission and reception means for communicating optical signals indicative of existence of selected of said detonation controlling module operating states between said detonation controlling module and said firing module coded optical energy-responsive electrical switching element via said multiple parallel path fiber optic optical energy signal transmission apparatus; 
     said detonation controlling module and said firing module including optical signal transmission and reception means for communicating optical signals indicative of existence of selected of said firing module operating states between said firing module and said detonation controlling module via said multiple parallel path fiber optic optical energy signal transmission apparatus; 
     said detonation controlling module also including manually electable operating state termination inputs enabling premature, and non detonating of said explosive material, resetting termination of a selected plurality of said intermediate states in said detonation controlling module and said firing module; 
     said quantity-limited depletable source of explosive material initiation electrical energy enabling time duration predictions of detonation energy available possible detonating of said explosive material and ensuing commencement of a remainder, insufficient detonation energy available, safe explosive material handling time; 
     manual operating means for initiating detonation of said explosive material upon transition through a selected plurality of said detonation controlling module and firing module operating states. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings incorporated in and forming a part of the specification, illustrate several aspects of the present invention and together with the description serve to explain the principles of the invention. In the drawings: 
     FIG. 1 shows an unusual operating environment in which the present invention may be successfully used. 
     FIG. 2 shows additional overall details of an embodiment of the present invention. 
     FIG. 3 shows yet additional details of an embodiment of the present invention in closer perspective. 
     FIG. 4 shows schematic diagram details of a detonation-controlling module according to the present invention. 
     FIG. 5 includes portions FIG. 5 a  and FIG. 5 b  that together show schematic diagram details of an explosive firing module according to the present invention. 
     FIG. 6 shows a simplified schematic diagram of the FIG. 4 detonation-controlling module in one operating state. 
     FIG. 7 shows a simplified schematic diagram of the FIG. 4 detonation-controlling module in another operating state. 
     FIG. 8 shows a simplified schematic diagram of the FIG. 4 detonation-controlling module in another operating state. 
     FIG. 9 shows a simplified schematic diagram of the FIG. 4 detonation-controlling module in another operating state. 
     FIG. 10 shows a simplified schematic diagram of the FIG. 4 detonation-controlling module in another operating state. 
     FIG. 11 shows a simplified schematic diagram of the FIG. 4 detonation-controlling module in another operating state. 
     FIG. 12 shows a simplified schematic diagram of the FIG. 4 detonation-controlling module in another operating state. 
     FIG. 13 shows a simplified schematic diagram of the FIG. 4 detonation-controlling module in another operating state. 
     FIG. 14 shows a simplified schematic diagram of the FIG. 4 detonation-controlling module in another operating state. 
     FIG. 15 shows the performance of a nine-volt alkaline battery of the Duracell® or Energizer® types over an extended two hour operating interval of the present invention firing module. 
     FIG. 16 shows a plot of battery voltage and current versus time for a detonation countdown interval of some twelve seconds duration using the present invention. 
     FIG. 17 shows an enlarged view of a detonation-controlling module control panel usable with the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 in the drawings shows a representative environment in which the present invention may be successfully used. In FIG. 1 a high-voltage electrical apparatus  100  is shown to include a source of high-voltage electrical potential, represented by the source  102 , connected by an explosion-responsive connection  106  to a second high-voltage device such as a high energy, high-voltage pulse forming network  128  and then to some electrical load as is represented by the resistance  104 . The source of high-voltage electrical potential, represented by the source  102  may be of a direct current, alternating current or pulsating energy nature and can provide potentials in the range of zero volts to hundreds of kilovolts or megavolts for present purposes. For safety and other reason it assumed desirable to include an open and visible disconnection arrangement in the FIG. 1 apparatus. 
     Such an open and visible disconnection arrangement may be achieved by way of the pair of electrical disconnect switch elements  116  and  120  mounted on the high-voltage-insulators  114  and  122  in the FIG. 1 apparatus. The switch element  116  in the FIG. 1 drawing is pivoted at the point  119  in order to allow a gravity-induced dropping away of this element from the connection with element  120 , i.e., the connection represented at  126 , during a circuit interruption event. Such drop away interruption of the FIG. 1 high voltage circuit may be accomplished by a disintegration of the explosive bolt member  132  and initiated by apparatus according to the present invention. This present invention apparatus includes the firing module  108 , the firing module to explosive material or explosive-bridgewire wired connection at  130  the combination fiber optic and pneumatic communication link  112  and the detonation-controlling module  110 . The FIG. 1 apparatus is intended to be only representative of apparatus and situations in which the present invention may be used. 
     The combination of very high-voltage and explosive materials represented in the FIG. 1 drawing of course suggests the need for careful consideration and abundant safety precaution in arriving at for example the elements  108 ,  110 ,  112  and  130  in the present invention. The high-voltage present on the switch elements  116 ,  119  and  120  in FIG. 1 are readily capable of initiating detonation of the explosive material or an explosive-bridgewire device used in the bolt  132  if such careful consideration and abundant safety precaution are flawed. As appears in certain of the materials following herein the input of a test range safety committee and other safety considerations are important influences over the described embodiment of the present invention. 
     FIG. 2 in the drawings shows the explosive-bridgewire firing apparatus of FIG. 1 in a somewhat more focused, simplified and additional-details representation. The FIG. 2 drawing includes an indication of possible separation distances between portions of the FIG. 1 apparatus and provides general details of the control panel used with the detonation-controlling module of FIG.  1 . Also shown in the FIG. 2 drawing is a source of pressurized air  208  such as a small compressor and tank used with the detonation-controlling module to supply the pneumatic tube communication link of the present invention. The power connection for the detonation-controlling module also appears at  210  in FIG.  2 . 
     The fiber optic and pneumatic signal conductors connecting the detonation-controlling module and the firing module of the present invention are represented at  212  in the FIG. 2 drawing. The fiber optic conductors of this group may be made of plastic fiber optic material or alternately, for signal conduction over distances greater than the  25  meters indicated in FIG. 2, may be made of glass fiber optic material including suitable connector members. Additional information regarding the fiber optic signal conductors appears in the Hewlett Packard Company material described elsewhere herein. The coaxial cable  214  of the bridgewire device in FIG. 2 is limited in length by the energy and current rise time requirements of the explosive-bridgewire detonator device used. Manufacturers of these bridgewire detonator devices publish data sheets and application notes useful in relating cable lengths, detonating capacitor size and voltage, coaxial cable size and length and other parameters. In the present instance a type RP- 1  explosive-bridgewire device made by Reynolds Industries Systems, Incorporated (RISI) of Northern California (http://risi-usa.com) is found to be suitable. Note also the current magnitude and rise time details disclosed in Table  1  herein relating to the explosive-bridgewire device. Additional details of the detonation-controlling module control panel  202  appear in the FIG. 17 drawing herein. 
     FIG. 3 in the drawings shows yet additional details of the detonation-controlling module  110 ,  202 , and firing module  108 ,  204  of the present invention in an even closer view. Control panel labels although readable in the FIG. 3 drawing are best observed in the FIG. 17 drawing herein. FIG. 3 also shows the two conductors of the coaxial cable  214 , general details of the connector devices used for the fiber optic and pneumatic communication link  112 , the coiled sheathing material covering the fiber optic and pneumatic communication link  112  elements, and other details associated with the detonation-controlling module. 
     Reference is made to both the FIG.  4  and FIG. 5 drawings in connection with the following specific descriptive material. The FIG. 5 drawing moreover includes the two parts identified as FIG. 5 a  and FIG. 5 b . In the interest of brevity component identification numbers in the four hundred series and five hundred series are freely intermixed in the following discussion without drawing source figure identification, after the introductory paragraphs; the former of these numbers however appear in FIG. 4, the latter in one of the FIG. 5 drawings. The detonation-controlling module of FIG. 4 is connected with the firing module of FIG. 5 by way of six fiber optic signal paths and a parallel pneumatic tube all of which are of course non conducting with respect to the possible kilovolts of potential existing between these modules (i.e., between the modules  108  and  110  in FIG. 1) before, during and after a detonation event. While on the subject of communication links and operating potentials it may be helpful to appreciate that the connection represented at  130  in the FIG. 1 drawing is in fact a wired connection and that the firing module  108  is therefore operated at the possibly high-voltage potential of the switch elements  116  and  120 . Preferably a short length of coaxial cable is used at  130  in FIG. 1 in order to exclude unwanted electrical fields including transient fields from the firing signal conducted along this same path. 
     FIG. 5 in the drawings therefore shows an electrical schematic diagram of a preferred firing module arrangement for the present invention. FIG. 4 shows an electrical schematic diagram of a detonation-controlling module usable with the FIG. 5 firing module. By way of a pneumatic pressure signal, three incoming optical signals and three outgoing optical signals the sub systems of the FIG. 5 apparatus are functionally coupled with the controlling and indicating elements of the controlling module in the FIG. 4 schematic diagram. Generally the FIG. 5 firing module apparatus  500  is comprised of the eight subsystems indicated at  502 ,  504 ,  508 ,  510 ,  512 ,  514 ,  516 , and  518 . The FIG. 4 controlling module apparatus  400  is comprised of almost the same eight subsystems indicated at  402 ,  404 ,  406 ,  408 ,  410 ,  412 ,  414 , and  416 . These matched subsystems achieve an orderly, safe and precisely controllable electrical initiation of the explosive-bridgewire device shown at  580  in the FIG. 5 drawing. 
     The FIG. 5 subsystems include the battery related apparatus at  502 , the safe indicator light at  504 , the optical key related apparatus at  508 , the latch related apparatus at  510 , the arm related apparatus at  512 , the completed capacitor charge apparatus at  514 , the firing apparatus at  516 , and the high voltage storage capacitor at  518 . The FIG. 4 subsystems include the AC to DC power supply at  402 , the safe indicator light at  404 , the air control valve at  406 , the optical key related apparatus at  408 , the latch related apparatus at  410 , the arm related apparatus at  412 , the completed capacitor charge apparatus at  414 , and the firing apparatus at  416 . These subsystems are operated approximately in the sequence recited here during a normal explosive detonating event and are therefore described in this sequence in the paragraphs following. Components used in the FIG.  4  and FIG. 5 modules are partly identified in the following paragraphs and supplementally identified in Table  2  of the appendix to the present specification. The mixture of FIG.  4  and FIG. 5 elements in Table  2  is believed desirable in view of their functional relationships and the relative ease with which the following combined description of the FIG.  4  and FIG. 5 modules can be understood. 
     The battery related apparatus at  502  in FIG. 5 provides a controlled and limited duration supply of electrical energy for operating the FIG. 5 circuits and for initiating firing of the explosive-bridgewire device  580 . The preferably primary battery, a fresh nine-volt alkaline transistor radio battery  517 , used in this subsystem is characterized as to operating life, firing reliability and other present application characteristics in the FIG.  15  and FIG. 16 drawings herein and in the data of Table  1  in the appendix. The loading resistors at  519  in the FIG. 5 drawing serve to establish a steady supplemental load current flow of about  15  milliamperes from the battery  517  upon its installation in the firing module in preparation for a detonation event and thereby, in combination with the other FIG. 5 circuits, limit the duration of the explosive detonation-possible period in the manner described quantitatively in the FIG.  14  and FIG. 15 drawings herein. The electrolytic capacitors shown at  520  in the FIG. 5 drawing assure a low alternating current electrical impedance source is available from the battery subsystem for the remaining FIG. 5 circuitry. 
     Once a new battery has been installed at  517  in the FIG. 5 system, and power switch  418  in FIG. 4, i.e., switch  1701  in FIG. 17, is on and the “Air Key Switch”  430  in FIG. 4, i.e., switch  1702  in FIG. 17, is off, the firing module circuits remain in the quiescent state shown in the FIG. 5 drawing with the normally closed pneumatic air key switch contacts  524 , AK 1 ′ closed. In this state a “safe” signal is communicated along the first fiber optic signal path from the FIG. 5 firing module transmitting transducer  522  (TD 8  etc) back toward the detonation-controlling module receiving transducer  420  of FIG.  4  and the “safe” control panel green light emitting diode  422  is thus illuminated. Upon closure of the FIG. 4 air key control at  430 ,  1702  in FIG. 17, the AK 1 ′ contacts In FIG. 5 open removing this transducer  522  signal and its energy as received in the receiver transducer  420  of FIG. 4; this extinguishes the safe signal emitted by the FIG. 4 light emitting diode  422 . The transistors  424  and  426  provide amplification of the transducer  420  electrical signal up to a level sufficient to operate the light emitting diode  422 . 
     The transducers  420  and  522  and the similar other components discussed herein are preferably embodied as devices described in the Hewlett Packard Company “Isolation and Control Components Designer&#39;s Catalog” under the heading of “Versatile Link” “The Versatile Fiber Optic Connection”, a catalog identified with the numbers 5965-1657E. More precisely the family of devices identified as the HP “HFBR-0501 Series” of fiber optic components may be used for these present purposes. These devices operate in the 660-nanometer spectral range, over a plurality of selectable data rates, separation distances and fiber optic conductor types. Identification of specific transducers from the HFBR-0501 Series appears in Table  2  herein. This Hewlett Packard Company data is hereby incorporated by reference herein. 
     Manual operation of the control panel air key switch next closes the electrical contacts  430  in a detonation initiating sequence; this closure is achieved by way of air valve  428  accomplishing pneumatic pressurization of the plastic tubing member disposed in parallel with the fiber optic signal paths connecting the firing module  500  with the detonation controlling module  400 . In the FIG. 5 firing module, pneumatic pressurization causes position changes of both the normally closed and normally open air key switch contacts at  524  and  526  along with position change of the four crowbar and series AKS contacts ( 548 ,  572 ,  574 ,  576 ) shown in connection with the energy storage capacitor  544  and the explosive-bridgewire device  580  in the right-most portions of the FIG. 5 drawing. Closure of the air key switch contact  526  applies energy from the nine volt battery  517  to the optical key portion  508  of the FIG. 5 circuitry as well as causing an opening of the air key switch contacts  524  and removal of the safe fiber optic signal between transducers  522  and  420 . As may be appreciated from the functional discussion below, the air key switch actuated by the FIG. 4 valve  428  may be regarded as an overall safety feature of the present invention; regardless of other events including misuse of the control panel inputs, no detonation of the explosive-bridgewire device  580  is possible until the air key switch valve is operated. 
     Closure of the air key switch contact  430  also applies five volts direct current energy from the power supply  419  to other portions of the FIG. 4 circuitry including the optical key circuitry shown at  408 . The closure of the “Optical Key Switch” at  433  in FIG. 4 (switch  1703  in FIG.  17 ), results in the generation of a pulse modulated optical key switch signal at the OKS transducer  431 . This signal is received via a second of the fiber optic signal paths at the transducer  528  in FIG.  5  and initiates additional FIG. 5 circuitry, the optical key circuits identified at  508 . Pulse modulated signal are used between the circuits  408  and  508  in the interest of safety, it being considered unlikely that any interfering signal, electrical or optical, received in the circuitry  508  can duplicate the intended pulse frequency of 10 kHz and thus falsely continue a FIG. 5 “countdown” sequence. Pulse modulation of the signal emitted by transducer  431  is achieved by the type  832  integrated circuit device  434  and the associated discrete timing components all as indicated at  432 . These components include a control panel-mounted timing adjustment potentiometer  1707  as also appears in the components  432  in FIG.  4 . Decoding of the received pulsed optical signal is achieved by another type  832  integrated circuit  530  and its associated discrete timing components appearing in FIG.  5 . 
     Successful receipt and decoding of the transmitting transducer  431  optical signal results in closure of the K 2  relay  532  and battery  517  energizing of additional parts of the FIG. 5 circuits. These circuit including the “latch” transmitting transducer  534 , energized by way of the double K 2  contacts at  531  and  533 . The “latch” optical signal is received via the third fiber optic signal path at the receiver transducer  435  of latch circuits  410  and results in energization of the red “latched” light emitting diode  436  on the detonation-controlling module control panel. This energization occurs by way of a discrete transistor amplifier of the type described above in connection with the circuits  404 . 
     Once the FIG. 4 circuits are in this “latched” condition a manual closure of the next switch in the “countdown” sequence, the “arm” switch at  438 , switch  1705  in FIG. 17, causes emission of another optical signal along the fourth fiber optic signal path by the transmitting transducer  440  and reception of this signal at the transducer  536  in the FIG. 5 firing module circuits. In the detonation-controlling module, closure of the “arm” switch  438  also closes relay K 1  which latches in the closed condition by way of the K 1  contact at  449 . A second K 1  contact at  439  keeps the “arm” transducer  440  “on” while the K 1  relay is latched. A third K 1 ′ contact at  442  opens with this event thus removing the green light emitting diode  444  “high voltage off” signal from the control panel. Latching of the relay K 1  is terminated by either a manual depression of the normally closed control panel “charge off switch”,  445  (switch  1704  in FIG.  17 ), or by depression of the “fire” switch that has a normally closed contact at  447  (switch  1706  in FIG.  17 ). 
     Reception of the fiber optic “arm” signal at the transducer  536  closes relay K 3  in the FIG. 5 firing module circuits by way of another discrete two-transistor amplifier of the type used at  404  in FIG. 4, an amplifier including the transistor Q 8 . Closure of relay K 3  closes the K 3  contact at  538  and thereby applies battery  517  energy to the DC-to-DC converter circuit  540  and commences the kilovolt charging of detonation energy storage capacitor  544  by way of the current limiting resistance  546 . Resistance  546  limits the initial inrush current to capacitor  544  and also limits the short circuit current demand from DC to DC converter circuit  540  in the event of inadvertent failure to open (or intentional safe abort reapplication of the air key switch and the closed high-voltage crowbar contacts  548 . 
     In order to inform the system operator when the charging of energy storage capacitor  544  has reached a voltage level sufficient to assuredly detonate the explosive-bridgewire element  580  a voltage sensing circuit as indicated generally at  514  in FIG. 5 is provided. When the voltage at the junction of resistors  550  and  552  reaches the level of the Zener diode  554  the type  339  quad comparator circuit at  556  changes output state and sends a “charged” optical signal from the transmitting transducer  558  via the fifth fiber optic signal path to the detonation-controlling module receiver transducer  446  to illuminate the red light emitting diode  448 . A capacitor voltage level above  1640  volts has been found suitable for this detonation of the explosive-bridgewire device identified in the components table, Table 1, of the present specification. 
     The additional voltage divider circuit comprised of resistors  560  and  562  connected with capacitor  544  in the firing circuits at  516  is used to charge a small capacitor  568  from the energy applied to capacitor  544 . The energy from this capacitor  568  is applied through the step-up pulse transformer  570  to the spark gap switch  572  to thereby initiate an arc in the switch  572  and thus dump the capacitor  544  energy into the explosive-bridgewire device  580 . These actions occur upon receipt of a “fire” command from the FIG. 4 transmitting transducer  450 . The “fire” command is initiated by operator closure of the “fire” switch contact at  452  and is transmitted via the sixth fiber optic signal path between detonation-controlling module and firing module. The receiving transducer  566  and its transistor amplification circuit feed the trigger signal to the SCR  564  which discharges capacitor  568  through the pulse transformer  570  to spark gap switch  573 . Use of energy tapped from capacitor  544  to initiate the firing sequence is a further assurance of the capacitor  544  having reached a sufficient level of charge to be successful in firing the explosive-bridgewire  580  prior to an actual firing event. Table  1  and FIGS. 14 and 15 herein provide more specific data with respect to typical explosive-bridgewire device firing requirements. 
     With regard to additional safety features included in the FIG.  4  and FIG. 5 apparatus note that either one of a manual election to abort a previously counted-down explosive-bridgewire detonation event through opening the “charge off switch” contacts at  445  or a manual opening of the “fire” switch contacts at  447  with a firing event causes release of the latched condition of relay K 1  in the FIG. 4 detonation-controlling module diagram and return of the system to an unarmed state. Note also that a manual reclosure of the air key switch will not only open the air key switch serial contacts at  572  and  574  and close the high-voltage crowbar contact  576  (both in prevention of explosive-bridgewire firing) but also close the capacitor crowbar contact at  548  and thereby discharge the capacitors  544  and  568  to zero or below the SCR  564  trigger level (via the two hundred ohms of series resistance at  547 ), remove the “charged” signal transmitted by the transmitting transducer  558  and thus additionally preclude a firing event. 
     FIG.  6  through FIG. 14 in the drawings show simplified operational schematic versions of the FIG. 5 firing module circuit in which details appearing in the FIG. 5 drawing are omitted for clarification and ease of understanding. Each of these drawings relate to a different operating state of the FIG. 5 circuit as described above and therefore show the several switches, indicator lamps and other details of the FIG. 5 apparatus in the status they attain during the respective states of circuit operation. The legends appearing below each of the FIG.  6  through FIG. 14 drawings summarize on the left the status of the switches and other components shown in that drawing, and summarize on the right the detonation safety features operative in the illustrated state. By way of clarification of the FIG.  6  through FIG. 14 drawings the “safe”, “latched” and “charged” lights shown in these drawings may be regarded as representations of the fiber optic transmitters identified at  522 ,  534  and  558  in FIG. 5 in order to maintain the principle that these drawings represent only firing module circuits. If these lights are viewed as representing control panel lamps then theoretically the FIG.  6  through FIG. 14 drawings are simplified composite drawings representing portions of both the FIG.  4  and FIG. 5 schematic diagrams. Firing of the explosive-bridgewire  580  is represented in simplified schematic form in the FIG. 11 drawing. The later drawings in the FIG.  6  through FIG. 14 group, i.e., the drawings of FIG.  12  through FIG. 14 represent states of the FIG. 5 circuit apparatus occurring after a explosive-bridgewire firing event, i.e., states involved in the return of the circuit to one or more possible quiescent conditions. 
     OPERATION 
     As shown in the drawings of FIG.  4  through FIG.  14  and in FIG. 17 herein there are five detonation-controlling module or control module inputs that must be “on” or “activated” for the firing module to initiate an explosive-bridgewire device. First, of course, the control console&#39;s AC power must be turned on. This switch,  418  in FIG. 4, is nothing more than an interrupt of the control module&#39;s 120 Volt AC power line. This switch does not immediately affect the firing module in any way; it only initially allows the control module to begin interrogation (or sensing) of the “safe” status of the firing module. Thus, when the control module is “powered on,” the “safe” LED on the control module illuminates, having sensed this state of the firing module through positive-logic on one of the fiber-optic lines. This positive-logic “safe” feedback signal from the firing module indicates that battery power is available, but is disconnected from all other parts of the firing module circuitry through the “fail-safe” operation of the multi-pole air key switch or pneumatic switch in the firing set. The firing module is said to be in state  0 . 
     Subsequently, in state  1 , as shown in the FIG. 7 drawing herein an “enabling the pneumatic lock out,” by the operator turns on the air key switch. At this time sufficient pressure is applied to the pneumatic tube at the detonation-controlling module end. This pressure is transmitted through the pneumatic tube from the detonation-controlling module to the firing module. This pressure activates the spring-loaded (fail-safe) air key switch in the firing module. The air key switch performs several functions in the firing module. First, it removes the “safe” feedback signal (one of the three fiber-optic return lines) from the firing module to the control module; this turns off the “safe” LED on the control module and indicates power has been applied to the optical key sensing circuitry (and associated relay) in the firing module. Additionally, the pneumatic switch removes the short-circuits on the high-voltage capacitor&#39;s output and on the explosive-bridgewire input, and connects both leads of the explosive-bridgewire to the high-voltage energy storage capacitor  544  through the high voltage spark gap switch  573 . 
     In the next state, state  2 , as represented in the FIG. 8 drawing an “enabling the optic interlock” occurs. In this state the operator turns “on” the “optical key switch” on the control module. This sends an optical square-wave signal to the firing module at a selected frequency that can be adjusted through the “optical frequency adjust” potentiometer,  1707  in FIG. 17, on the face of the control module. When the frequency-selective detector circuit (energized in state  1 ) in the firing module senses this signal, it energizes a relay  532  that directly connects both poles of the battery power to additional firing module circuitry. This circuitry consists of the diagnostic and communication electronics needed in the charging state. (For example, high-voltage capacitor voltage level sensor circuitry, and high-voltage switch control circuitry.) The power to the DC-DC converter is not yet applied. At this time, the “latching” relay sends a fiber-optic signal back to the control module where the control module illuminates the “latched” LED. At this point also there is only one electrical connection (the arming relay) preventing the DC-to-DC converter from charging the high-voltage capacitor. 
     In the next detonation-controlling module state, state  3 , the operator presses the momentary-contact “ARM” button on the control module. Although this is a momentary switch, it latches closed by way of a K 1  relay contact and keeps the “ARM” line optically energized until it is interrupted by a “charge off” or “fire” command received at one of the normally closed switches  445  and  447 , respectively. The “HV Off” LED on the control module is turned “off” to show that the high-voltage circuitry on the firing module has been energized. At this point, in the firing module, the battery is finally connected through one switch,  526 , and three relay contacts  531 ,  533 , and  538  to the DC to DC converter. The high-voltage capacitor  544  used to fire the explosive-bridgewire is thereby caused to charge. Since the explosive-bridgewire has minimum current and rate-of-rise-of-current requirements, it is necessary to disallow firing of the explosive-bridgewire until the capacitor has charged to a sufficient level. It has been elected to provide feedback to the operator as to when the capacitor  544  is sufficiently charged as opposed to locking out the operator&#39;s command until sufficient charge is attained. 
     When the capacitor  544  charges to the minimum level, circuitry within the firing module senses this, and sends a “charged” fiber-optic signal back to the control module at which time the control module illuminates the “charged” LED. This is state  4 . The firing module is then ready to fire the explosive-bridgewire. (Notice that, so far, the “Charge Off” control button, just next to the “ARM” button has not used. This button is used only for detonation abort operations.) While the main high-voltage capacitor is charging, a smaller capacitor  568  in the firing module also charges. When the “fire” button is pressed, this smaller capacitor  568  is connected (through a silicon controlled rectifier and high-voltage pulse transformer) to the high-voltage gap switch  573  used to directly connect the high-voltage capacitor  544  to the explosive-bridgewire. 
     In state  5 , “Fire the EBW,” as described above, the small capacitor  568  is discharged through a pulse transformer  570  and SCR  564  to initiate the breakdown of a high-voltage gap switch  573  that directly connects the capacitor  544  to the explosive-bridgewire. When the “fire” button is pressed on the control module, the “ARM” signal is also removed and charging of the capacitor  544  ceases. This eliminates possible multiple firings of the explosive-bridgewire. With the removal of the arm signal, the firing module circuit is returned to state  2  thus disconnecting power from the step-up DC to DC converter  540 . 
     Next, the operator removes the optical key in the control module and this returns the firing module to state  1 . Finally, the operator removes the key from the air key switch and thereby returns the firing set to state  0  or the “safe” state. 
     While the apparatus and method herein described constitute a preferred embodiment of the invention, it is to be understood that the invention is not limited to this precise form of apparatus or method and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims.