Note: Descriptions are shown in the official language in which they were submitted.
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RE~n~ DEI~NATION OF
EXPL061VE C~k~3ES
RACKGROUND OF ~ E INVENTICN
Ihis invention relates generally to devices and meth~ls for
remotely detonating one or more explosive charges.
More specifically this invention relates to the precisely timed,
remote detonation of explosive charges using electrical detonators in
environments having high levels of extraneous electricity including
stray ground currents, electromagnetic fields and radio frequency
energy.
It has become increasingly common for hostages to be taken during
criminal activity or in the co~mission of terrorist acts. Concern for
the safety of hostages has ordinarily inhibited or precluded the use
of force by the responsible authorities. When force is employed, it
is necessary to act with precise timing so as to prevent, or minimize,
any retaliatory action on the part of the terrorists toward the ~ -
hostages. -~
In many instances, any effective response by the authorities
requires the use of explosives, as for example, to breach a wall, to
sever the hinges or lock of a door, to create a diversion, to disperse
smoke or disabling gases, or for other analogous purposes. Ordinarily,
a number of different types or sizes of explosive devices situated at
different locations are desirably employed. Ihere are immense
practical difficulties involved in the physical placement of explosive -~
devices under such conditions and the time that might be required to
accomplish such placement is ordinarily difficult to predict. Also, ~ ~R
hostage-taking events often display rapidly changing circumstances.
Consequently, it is impractical and frequently undesirable to place an ~ - -
explbsive charge having a fixed, or preset, time of detonation. ! ~ :~ .- ~ :-:'
The remote detonation of explosive charges is, of course, well ;
known and commonly practiced in co~mercial and industrial blasting.
Explosive charges are most commonly detonated using electric blasting
caps as initiators. Non-electric blasting caps for use with safety
fuse and detonating cord are also routinely used e~plosive charge
initiators.
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None of these conventional techniques for detonating explosive
charges is satisfactory for use in terrorist situations. Most
terrorist acts and hostage-taking events occur in urban and highly
congested areas. Such areas normally contain high levels of extraneous
electricity, especially stray ground currents, eleotromagnetic fields
associated with transmission lines, and radio frequency energy from TV
and radio transmission and the like. Ihis background electrical energy
is ordinarily substantially increased by the high concentration of
communications and surveillance devices which converge on the area in
response to a terrorist act. It is well known that radio frequency
current induced in a blast wiring circuit can initiate electric
blasting caps. Consequently, safety considerations require that
electric blasting not be attempted in areas where extraneous currents
are greater than about 50 milli~nperes.
When extraneous currents exceed about 50 milliamperes, standard
safety precautions require use of a non-electric initiating system.
Those non-electric systems comprising blasting caps and safety fuse
are time consuming to rig and, after being rigged, are quite
inflexible. It is, for example, difficult to change the sequence of
detonation, to precisely control the timing of detonation, and to
change the time delay between individual charges. Also, there is a
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finite time delay between ignition of the fuse and detonation of the
corresponding explosive charge.
Because of the safety, environmental and timing requirements and
restraints placed upon explosives use in terrorist and hostage-taking
events, conventional blasting techniques are of little value. Yet,
the judicious use of explosives offers a very effective tool in
suppressing terrorist activities.
SUMM~KY OF IHE INVENrION
The remote detonation of explosive charges, especially in
- environments having high--levels of extraneous electricity, is
accomplished by providing an individual control unit for each explosive
charge. Each control unit is short-coupled to its respective charge
in a manner which prevents the generation of an induced current in the
~detonating circuit and is arranged to arm and to detonate the charge
only in response to a plurality of radio-transmitted coded com~ands in
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proper sequence and repeated with proper frequency. Ihe control units
are arranged so that each must be placed in an arned state by coded
co~mand before it will accept a co~mand to detonate the charge and
failure of a unit to continuously receive a command to arm prevents its ;~
acceptance of a command to detonate the charge.
Hence, it is an object of this invention to provide means and
techniques for the remote detonation of explosive charges especially
in areas exposed to high levels of extraneous electricity.
Other objects of this invention will be evident from the
following description of certain preferred embodiments of the
invention.
~IEF DESCRIPTIoN OF ~E DRAWINGS j~
The drawing illustrates certain preferred embodiments of the
invention in which:
15Figure 1 is a schemat;c diagram illustrating the major sub~
systems of the invention and their interaction; ;;
Figure 2 is a system functional diagram further illustrating its
operation;
Figure 3 illustrates the components of an individual control unit
processor;
Figure 4 shows one preferred format for the coded control
messages passed between the command unit and the individual control
ur.it when the latter are in a "ready" state; -
Figure 4-A shows a preferred format for the coded control
25 messages passed from the command unit causing individual control units - -
to arm and fire;
Figure 5 depicts in partial section an explosive charge
arrsngement advantageously used in the invention;
Figure 6 shows the arrangement of a detonation switch in the
30 deactivated position; and -
Figure 6-A shows the arrangement of the switch of Figure 6 in an
activated or "fire" position. --
DET~ILED DESCRIPTICN OF ~
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35The remotely controlled detonating system of this invention will
be- described in relation to its use in an urban area for law ~
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enforcement purposes. Referring first to Figure 1, there is shown a
generalized, functional diagram of the system of this invention
together with the major sub-systems and their intersction.
In a preferred embodiment, the detonating system of this
invention shown generally at 10, includes three major sub-systems.
One of the sub-systems is a command unit 11 which includes a c ~ and
console, radio transmitters and receivers and microprocessors. A
second sub-system comprises a translator unit 12 which is designed to
act as a relay point between the command unit and one or more
individual control units 13. Ihe functions of translator unit 12 can
be incorporsted into the command unit 11 but that arrangement is much
less preferred. Provision of a translator unit, as is illustrated,
ensures a very strong signal for the individual control units 13
independent of multi-path reflections, transmitter fading and other
radio propagation phenomena that may exist. It also allows
transmitters in the individual control units 13, used to feedback
status information to the com~and unit, to be low powered thus allowing
reduced size and complexity.
Each individual control unit 13 contains a radio receiver which
receives signals from the c ~ nd unit 11 relayed through the
translator 12. Individual control units also contain firing logic and
firing mechanisms for detonating an explosive charge 14. Charge 14 is
connected to its control unit bv means of signal transmitting means lS
which may be an electrical wire conductor or in certain embodiments,
may be an optical fiber. Wire 15 is made sufficiently long, typically
five to fifteen feet, so as to ensure that control units 13 survive the
blast of charge 14 without damage.
In a preferred mode, co ~ nd unit 11 is provided with antennas
` 16, for transmission of radio signal 17 for reception by antenna 18 of
translator 12, and 19 for the reception of radio signal 20 broadcast
by translator antenna 21. Translator 12 is also arranged to broadcast
signals 22, which may be a relay of signal 17, for reception by
individual control units 13 through antennas 23. In a similar fashion,
control units 13 ~re arranged to broadcast a signal 24, representative
3S of system status, by means of antennas 25.
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Figure 2 shows the components making up each sub-system in
greater detail. Referring now to that Figure, command unit 11 is shcwn
in dashed outline and includes a command console 31, a processor 32,
a radio transmitter 33 and radio receiver 34. Both transmitter 33 and
S receiver 34 are preferably FM. Console 31 is arranKed so as to allow
an operator to determine the status of any or all of the individual
control units and to command the arming, disarming or firing of any or
all of the explosive charges 14 either simultaneously or in any timed
sequence. The system is designed such that a disarm co~mand will
override all else.
There is also illustrated an optional sub-system 40, not shown
in Figure 1, comprising a closed circuit television camera 41 and an
associated transmitter 42. Camera 41 may be used to monitor the
locations of charges 14 and transmit that picture back to closed
circuit television receiver 35 via signal 43. Ihe picture may be
displayed on a video monitor incorporated in command console 31.
Translator sub-system 12 includes an FM radio receiver 51 which
is adapted to pick up signal 17 produced by command unit transmitter
33.
That signal is fed to PM transmitter 52 where it is re-broadcast
as signal 22 directed to individual control units 13. Sub-system 12
also includes an A~l radio receiver 53 to pick up signal 24 from
individual control units 13. m at signal is passed to encoding
- decoding processor 54 which produces a data stream re-broadcast as
signal 20 bv FM transmitter 55.
Each individual control unit 13 is provided with a co~mand
receiver 61 which is adapted to receive either the command unit signal
17 or the re-broadcast signal 22 from translator 12. m at radio signal
is passed to a processor-decoder means 62 which is shown in greater
detail in Figure 3. Processor-decoder 62 functions to arm and activate
firing mech~nism 63, upon proper co~mand, thus detonating explosive
charge. Means 62 also performs housekeeping functions including
reporting on the status of mechanism 63 and coding that status
information for transmission back to translator 12 via radio signal 24
broadcast by transmitter 64.
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Turning now to ~`igure 3, there is shown in diagrammatic block
form the components of a processor-decoder module 62 of an individual
control unit 13. Mbdule 62 is designed to accept and respond to
messages from the co~mand unit 11, including those relayed through
translator 12, to arm, disarm, or fire the explosive charge 14
associated with each individual control unit. All such messages
between the command unit and the individual control units must be
absolutely distinctive so that the chances of an individual control
unit responding to some random signal, or to a signal directed to
another individual control unit, is essentially zero. Consequently,
each individual control unit is provided with an identifying code
which, in a preferred embodiment, is a Mersenne prime number.
Figures 4 and 4-A provide examples of preferred formats of the
coded messages. Referring now to Figure's 3, 4 and 4-A, a message
includes a preamble and a designation code sequence as is diagrammed
in Figure 4. r~he preamble is processed by preamble decoder 71 and is
used for synchronization of clock 72 with that of the command unit and
to alert housekeeping module 73 to be ready to accept data. Follawing
the preamble is a designation code sequence consisting of a marker
identifying the beginning of a message and the designation itself. As
was set out previously, the designation preferably is a Mersenne prime
number. After the designation of a first individual control unit is
completed, the designation of a second control unit is transmitted and
so on until all desired individual control units have been alerted.
In one preferred e~bodiment, the preamble and designation
portions of the message are 15-bit binary words corresponding to a
Mcrsenne prime number. Redundancy is built into the system to further
reduce the possibility of the control units responding to a spurious
signal. Ihat is, la,ccomplishqd by the transmission of at least two
separate destination codes multiple times. A first designation decoder
74 and a second designation decoder 75 are provided to process the
separate message codes and each decoder must correctly receive its
transmitted code four out of five times in order for module 62 to
recognize a valid designation. Summarizing those requirements, an
individual control unit is placed on an alert status only after it has
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received two separate specific messages, each 15 bits long, in four out
of five transmissions.
To further illustrate operation of the system, presume that a
total of twenty explosive charges, each with its own individual control
unit, have been placed into position. Ihe responsible official in
charge of the operation and controlling the central comnand unit 11
determines from either external intelligence sources or from the closed
circuit visual observation system 40 which charges he desires to
detonate and in what order. He then enters that data into the system
using the command console 31 (Figure 2) of comnand unit 11. The
processor 32 of the comnand unit receives this information and
generates a coded message to be transmitted to translator 12 for relay
to the individual control units.
Presume further that the twenty charges and their control units
are numbered sequentialiy and that four of the charges, numbers 3, 11,
12 and 17, are designated for simultaneous detonation. Upon receiving
the message preamble, the clock 72 of each of the twenty individual
control units is synchronized with the clock of the command unit and
each control unit then watches to see if its designations are being
transmitted. The stream of digital data from the receiver 61 of each
individual control unit is fed to module 62. Each of the twenty
individual control units has a specific prime number for each decoder,
or two prime numbers per unit, which it is set to recognize. The sets
` of prime numbers corresponding to each of control units 3, 11, 12 and
17 are broadcast in the signal format illustrated in Figure 4. If both
decoders 74 and 75 recognize their respective prime numbers in at least
four of five transmissions, then the individual control unit is placed
on alert status where it can accept further instructions. At that
point, a signal isj sent to the housekeeping component 73 indicating
that its individual control unit has been designated by the comnand
unit. Cbmponent 73 then sends a message to transmitter 64, confirming
the decision, for broadcast back to translator 12. That infornation
i8 decoded, combined with similar info~nation from the other indi~idual
control units, and is transmitted back to the comnand unit.
When the message is received by the command unit, it is decoded
in processor 32 and displayed on the command console 31. That console
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preferably includes visual indication of the status of each individual
control unit. In this case, the console would sh~w by appropriate
indicia that control units 3, 11, 12 and 17 were in an alert status
while the remaining sixteen units were inactive.
As long as the four individual control units designated to be on
alert status remain so designated, encoded messsges are transmitted
continuously to the individual control units and those units
continuously transmit confirmations back to the comnand unit. Control
units under an alert status may be removed from that status by the
official in charge at will and other units can be designated.
Should the official decide that he may need to detonate the
explosive charges, he then causes the status of the four designated
control units to change~from an alert to an armed state. This is
accomplished by activating an arm switch on the command console which
causes the message being transmitted to the control units to change to
the format shown in Figure 4-A. The new message format includes a 20~
bit binary word which comnands the individual control unit to arm its
circuits. mis new message is received and processed in the arming
comnand decoder 76 which in turn transmits the coamand to the arm logic
discriminator 77.
Arm logic discriminator 77 perfonms two functions. First, it
monitors the status of the system to ensure that a disarm comnand has
not been issued. The official in control of the comnand console always
~ has the ability to transmit a disarm signal. mat signal is received
and processed in the diæarm com~and decoder 78 and the command is then
transmitted to the arm logic discriminator 77. Discriminator 77 is
arranged so as to give a disarm signal a higher priority than an arm
signal. A disarm comnand prevents discriminator 77 from passing the
comnand through to the arming logic circuit 79.
The second function of the arming logic discriminator 77 is to
keep track of how long it has been since the last anning command was
received. The system i~ de~igned so that it must receive a new arm
comnand periodically else it reverts back to the alert status.
Preferably, a new arm co~mand must be received once every three frame~
of data for the system to remain armed. If the arming logic
discriminator determines that the anning comnand is valid, that there
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has been no disarm cornnand and that the arming co~mand has occurred
frequently enough, it then passes positive confirmation of arming to
the arming logic circuit 79.
When the system is armed, the housekeeping component 73 of the
processor 62 monitors the arming logic circuit 79 ad determines that
the individual control unit is in the armed mode. It encodes this data
and sends it back to the cornn~nd unit where the command console 31
provides the responsible official with visual confirmation that the arm
signal has been received by the designated individual control unit.
The visual confirmation may, for example, take the form of a status
light provided for each individual control unit which will be
illuminated whenever the unit is in an armed status.
At this point, the only thing yet required to cause the
designated individual control units to detonate their respective
explosive charges is to transmit a firing command. If prior to issuing
a fire com~and the responsible official decides to disarm the
designated units, he may issue a disarm signal which causes the
designated units to come out of the arm position and revert back to an
alert status. Alternatively, the system allows for each or all of the
individual control units to be de-designated by appropriate command
thus providing redundancy in the disarming circuits.
The explosive charges associated with their respective individual
control units, in this example units 3, 11, 12 and 17, can now be
detonated at will by the activation of a fire switch located at the
command console 31. That will cause a fire command to be encoded on
the data stream in a format such as is diagra~,med in Figure 4-A. The
cornmand is transmitted to the individual control units where it is
detected and decoded by the fire cornnand decoder 80 of processor 62.
If decoder 80 recognizes the fire command as authentic, it transmits
a fine signal to firing logic rnodule 81. If, at the time the fire
signal is received by firing logic Imodule 81, there is a positive
output frorn the arming logic 79 and there is no disarm signal present
the firing logic will issue a firing cornnand. This fire conmand is
transmitted through electrical or optical conductors 15 to a mechanism
for detonating the charge.
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The firing mechanism itself is of conventional type and
preferably comprise a capacitor discharge blasting machine. S~1ch
devices are well known and comprise a capacitor which stores a quantity
of electricity. The capacitor is discharged into the firing circuit
S upon activation of a firing switch causing an electric blastin~ cap to ~
detonate the explosive charge. -~ ;
Turning now to Figure 5, there is shown one preferred arrangement
of explosive charge means 14 for use in this invention. The charge
means preferably comprises a shaped charge including a solid explosive
101 emplaced in back of conical liner 102 so as to direct the force of ;~
the explosion forwardly along the axis 103 of liner 102. An electric
blasting cap 104 is provided at the rear of charge 101 to detonate the
explosive. Cap 104 is connected to initiating switch 105 through
electrically conducting leg wires 106. Switch 105 is operably
connected to switch activator 107 through linkage means 108. Activator
107 is caused to operate and change the position of switch 105 upon
receiving a signal, which may be electrical or optical, from the
individual control unit associated with the charge by way of conductors ~ 2
15. Upon activation of switch 105, a surge of electric current is
supplied to the switch from capacitor dischsrge blasting machine 110
or similar device through conductor pair 111 and 112.
m e entire charge 14 is preferably contained within housing means
113 which functions to protect the charge from damage during transport ~-
and placement. It is preferred also that an electromagnetic shielding
means 114 be provided to completely surround the charge. Shielding
means 114 and housing means 113 may be combined together in a single
element.
High frequency radiation from radio transmitters, directional
radar antenna, and similar sources will induce a current in any
conductor within the radiation field. Such an induced current wilI
generate the same heat in the bridge wire of blasting cap 104 as will
a DC current of the same amperage. Because the magnitude of any
current induced in the leg wires 106 of cap 14 is dependent upon the
length of the leg wires, the length of those leg wires in the
embodiment of Figure 5 is maintained as short as possible. mis~
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coupled with electromagnetic shielding 114, essentially prevents any
induced current flow through and heating of the bridge wire of C8p 104.
The possibility of the accidental detonation of charge 14 by
extraneous electric or electromagnetic energy may be further reduced
through use of the switch arrangement diagra~matically illustrated in
Figures ~ and 6-A. Figure 6 shows the arrangement of initiating, or
detonating, switch 105 in the deactivated position while Figure 6-A
diagrams the same switch in a "fire" position.
Refarring to those two Figures in association also with Figure
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5 conductor 111, which is one of the two conductors connecting blasting
machine 110 with switch 105, branches to go to ground 121 and to a
switch terminal post 122. Another branch of conductor 111 forms one
of the leg wires (designated 106 in Figure 5) of blasting cap 104. The
other conductor 112 from blasting machine 110 is directed to switch
terminal post 123. The other leg wire 106 of blasting cap 104 branches
to form a pair of opposed switch terminal posts 124 and 125.
There is also provided switch contact bar 126 which is movable
by switch activator means 107 (Figure 5) between two positions. In
the first position, the deactivated position shown in Figure 6, contact
bar 126 connects switch terninals 122 and 124. As may be appreciated
from the diagram, this shorts out and grounds the two leg wires 106 of
cap 104 preventing any current flow through the bridge wire of cap 104.
In its second position, the "fire" position shown in Figure 6-A,
contact bar 126 connects terminals 123 and 125. This completes a
circuit of conductor 111 through blasting cap 104 and returning through
conductor 112 thus allowing blasting machine 110 to discharge causing
the detonation of cap 104 and explosive 101.
Although the explosive charge 14 was illustrated in Figure 5 to
be of shaped charge configuration, other types of charges may be
equally useful depending upon circumstances. A shaped charge, either
conical or linear, is most useful for gaining entrance into an
enclosure as, for example, detaching a door from its hinges and
latches. In other circumstances a charge might be configured to
maximize its blast effect to stun and confuse persons in proximity to
the charge. Likewise, detonating switches different from that one
illustrated in Figures 6 and 6-A may be used to advantage.
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Ihe conductors 15 connecting each individual control unit 13 with ,,
its charge 14 are kept as short as possible so as to minimize induced
currents while at the same time allowing the control units to survive ~ ;
the blast without damage. ;~
SOther details of design and construction may be modified without
departing from the invention set forth in the appended claims.
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