The Army is undertaking a transformation to better meet small-scale contingencies without compromising major theater war capability.

A03-196 TITLE: Explosive Pulsed Power

TECHNOLOGY AREAS: Weapons

ACQUISITION PROGRAM: PEO-Air & Missile Defense

OBJECTIVE: The objectives of this effort are to develop explosive pulsed power systems that can be used to produce small to medium caliber munitions (40-mm to 155-mm) capable of producing effects in addition to blast and fragmentation.

DESCRIPTION: The radius of damage and the destructive power of conventional munitions is limited to that of the blast and fragments. The objectives of this effort are to extend the lethal range of munitions, increase the scope of the target set, and enhance destruction capability. A directed energy component, such as high power microwave or ultra wideband signals, can attack sensitive electronics and may have longer lethal ranges than blast waves and fragments. Activated materials, such as aerosols, can enhance conventional munitions by adding a component that can provide new sensor blinding and power system disruption mechanisms to enhance lethal damage to targets. One of the critical technologies that will enable the development of multi-functional munitions by providing sufficient electrical power from a very compact and rugged package is explosive driven pulsed power. Current capacitive and inductive energy storage technologies do not provide sufficient energy or meet the severe mass and volume requirements imposed by the munitions being considered for development.

PHASE I: Identify potential explosive driven pulsed power systems and their associated power conditioning and analyze, design, and conduct proof-of-principle demonstrations to: 1) verify that outputs are predictable and are consistent with predictions, and 2) to assess their suitability for use in a variety of munitions to include packaging and ruggedization.

PHASE II: Design, build, and test enhanced prototype explosive pulsed power systems and/or their critical components and verify their capabilities. Design production process for mass production.

PHASE III DUAL USE APPLICATIONS: Explosive pulsed power systems are being considered for oil and mineral exploration, propulsion systems and electromagnetic launchers, rapid charging of capacitors, magnetized target fusion, and destruction of chemical and biological agents.

REFERENCES:
1) J. Benford and J. Swegle, High Power Microwaves, Artech House, Boston (1992).
2) L. Altgilbers, M. Brown, I. Grishnaev, B. Novac, S. Tkach, Y. Tkach, Magnetocumulative Generators, Springer-Verlag, New York (1999).
3) L. Altgilbers, et al, “Compact Explosive Driven Sources of Microwaves: Test Results”, Megagauss 98 Proceedings, to be published.
4) A. B. Prishchepenko, V. V. Kiseljov, and I. S. Kudimov, “Radio Frequency Weapon at the Future Battlefield”, EUROEM, in Proceedings of EUROEM 94, Bordeaux (1994).
5) A. B. Prishchepenko and V. P. Zhitnikov. “Microwave Ammunitions: SUMM CRIQUE”, in Proceedings of AMREM 96, Albuquerque (1996).
6) A. B. Prishchepenko, “Devices Built Around Permanent Magnets for Generating an Initial Current in Helical Explosive Magnetic Generators”, Instruments and Experimentation Techniques, 38(4), Part 2, pp. 515 – 520 (1995).
[7) A. B. Prishchepenko and M. V. Shchelkachev, “Operating Regime of an Explosive Magnetic Field Compression Generator with a Capacitive Load with a Consideration of Magnetic Flux Losses”, Journal of Applied Mechanics and Technical Physics, 32(6), pp. 848 – 854 (1991).
8) A. A. Barmin and A.B. Prishchepenko, “Compression of a Magnetic Field in a Single Cyrstal by a Strong Converging Ionizing Shock Wave”, in Megagauss Magnetic Field Generation and Pulsed Power Applications (eds. M. Cowan and R. B. Spielman), Nova Science Publ., New York, pp. 35 – 40 (1994).
9) A. B. Prishchepenko, D. V. Tretjakov, and M. V. Shchelkachev. “Energy Balance by Explosive Piezoelectric Generator of Frequency Work”, Electrical Technology, No. 1, pp. 141 - 145 (1997).
10) A. B. Prishchepenko, Electromagnetic Munitions, 96UM0427 Moscow Soldat Udachi, No. 3, pp. 45 – 46 (1996).

KEYWORDS: Pulsed Power, Marx Generators, Magnetocumulative Generators, Magnetic Flux Compression Generators, Ferroelectric Generators, Piezoelectric Generators, Ferromagnetic Generators, Switches, Transformers, and Power Conditioning.

Project METC Summary Report

The chief difference in METC unit (Multiple Explosives Transitional Container) design over traditional explosive devices moves away from a densely packed explosive core towards a large volume of highly explosive but low-density mass in the form of a gaseous cloud. In the normal bomb all explosive energy comes from a tightly packed core and must drive outward against air pressure and objects it encounters. It rapidly bleeds off energy at the square of the distance as it accumulates a wall of pressure resistance and a mass of heavy debris, which it must continually regather and push along.

The new design starts as a small device but transforms itself through simple means from a dense-core technology to a much larger gaseous-cloud state. Igniting the explosive cloud at any peripheral or central point creates a chain-reaction-like and progressively growing explosive force. As the force of the explosion moves outward, it continues to ignite fresh explosive materials as encountered and gains momentum rather than loosing it. Further, because the gaseous cloud is efficiently mixed explosive materials combined with abundant free-air oxygen, ignition is far more complete and productive - leaving little or no chemical residue or traditional flash evidence (other than a burn signature, which any investigator would presume to be from ordinary fire)on immediately encountered objects. The net result is as if a significantly larger central core device had been detonated, with the complete and even combustion making difficult any aftermath analysis as to the true nature of the explosives used. Finally, the shape of the cloud and the ignition point within the cloud, if properly controlled, provides an extremely easy means to create shaped charge effects despite a relatively free-form original cloud shape.

Termed an electro-hydrodynamic gaseous fuel device (fn1), it produces a three-stage explosion through a process described as a highly focused, a-neutronic (fn2) energy transfer. The first detonation would be a small, low-volume explosion provided by just a few ounces of PETN explosive (fn3). This is placed within a relatively small central core shaft suspended from the top of the bomb container such that it is surrounded by a liquid compound of aqueous ammonium nitrate. The core shaft containing the explosive is itself made up of a compressed and hardened compound of aluminum silicate and N2O4, which starts as a slurry prior to application of a high-pressure baking process. Except for the explosive charge protected from external forces within, these items are all safe from accidental detonation as relatively safe-to-handle materials.

The first explosion's sole function is something akin to shaking a warm soda bottle violently with only a thumb to cover the opening. The relatively small explosion providing three key effects: reduction of the inner core shaft to a micro fine powder; mixture of the resulting powder and aqueous solution under violently induced pressure in order to cause complete chemical absorption; and force- opening the container to support eruption of contents into a gaseous state. The cylindrical bomb casing, which has precut scores or weak points to insure it ruptures in a sawtooth pattern about its middle, splits into two flowered halves which blossom outward from the pressure. The upper half shoots upward as if shot from a cannon, while the lower portion remains cannon-like and in place on its base.

Milliseconds later, a second explosion of a larger quantity of more powerful PDTN (fn4) material is set off at the bottom of the container. Timing is critical in milliseconds as too-long a delay would allow the flash of the explosion to prematurely ignite the gaseous cloud. This detonation must take place before the cloud has been adequately oxygenated and so expanded as to be reactant to the flash, but delayed to the optimum point for final blast effects.

The ideal detonator would likely be some form of barometric sensing device looking for the changes in pressure as the explosion's forced evacuation begins to drop back towards normal levels. Simple electronic timing devices could work adequately but would not allow optimum performance in field application, as the variables of bomb placement relative to large objects/structures and open/confined spaces can impact on timing needs in incalculable ways.

This secondary explosive is housed within its own shaped charge container formed into the bottom of the lower bomb casing. The shape and higher force of the second blast forces the bottom of the casing to separate from its base and fly upward. In this action, it will burst open even wider into its own flower petal shape, providing additional turbulent mixing of the forming cloud with free air. The violent turbulence, in turn, causes portions of the cloud to become highly charged electro statically as it continues to form a huge and turbulent mushroom immediately over ground zero. Explosive potential has now been reached, though optimal performance is dictated by cloud size, shape, and density -- which are again variables effected by the bombs placement and surroundings.

The cloud is made up of a mixture of the Aqueous Ammonium Nitrate with the pulverized aluminum Silicate and N2O4 compound. Once mixed with each other and free-air oxygen under force of the first two detonations, the resulting cloud is extremely explosive in nature, electro statically charged, decidedly cold, and awaiting only an opportunity to detonate. The shape of the cloud itself, due to the nature of the cannonade-like upward flight of the upper casing, and the blunter and delayed action of the lower casing, is somewhat tear shaped - though designs can be made to produce other shapes by nature of the original container's design. This can be a key factor in fixing the shape and focus of the blast effect.

In air burst explosions provided by conventional weapons, the blast effect is minimal due to a rapid bleed of energy in all directions as blast radius increases, with only those items beneath ground zero being subjected to blast exposure. Ground explosions, however, provide a means of deflecting otherwise wasted energy into a more desired radial blast effect. In nuclear technology, the reverse is true. A ground blast wastes energy in vaporizing and throwing up of tremendous quantities of ground materials where an air blast expands to maximum heat and blast effect forces before coming into contact with ground objects -- forming a broader circle of maximum impact. An air burst shock wave travels in air, a light medium, whereas the ground burst starts with solid matter thrown up by the blast - a heavier medium. An angular shock wave in a light medium tends to reflect when striking a solid, immovable plane such as the earth. This re-radiates the energy outward and back upward (fn5), further enhancing the shock wave effects against any encountered ground structures.

If the resulting METC unit cloud can be triggered from the top down, energy transfer drives the explosion downward and takes advantage of the tear-shape cloud. To repeat, as the force of the explosion moves outward from the ignition point, it continues to ignite fresh explosive materials as encountered and the blast gains momentum rather than loosing. By controlling the original ignition point, the blast effect can become highly focused and magnified. Yet, as an air blast, the outermost zone of actual blast damage is somewhat lessened, limiting collateral damage to a given, focused blast perimeter. This is because the focused energy deflects upward instead of radiating away from ground zero parallel to the ground. Only the secondary shock wave effects would have impact on surrounding or secondary structures or objects -- such as blowing out windows, a peculiar trademark of the device (fn5) which may dictate or limit applications should the nature of the device become public and covert application be required without revealing the type of explosives used. In the case of nuclear technology, the secondary shock wave damage is much more significant due to the massive scale of the original explosive force, and so, the effective radius of the bomb is increased dramatically. METC, unless constructed on a much larger scale, need not be so described.

Where traditional military explosives provide detonation velocities of 7,000-8,100 feet per second at the blast point. These bleed off at the square of the distance from the center of ground zero. The METC unit device, in ideal applications, is capable of much higher performance in the [REDACTED] range over a larger ground zero area equal to cloud diameter -- though destructive forces immediately beneath ground zero are notably less than at the edge of the cloud and beyond (fn6). Final velocities can be conceivably higher with optimal environmental placements, bomb design, and timing. These higher velocities provide several magnitudes greater damage potential as destructive capacity can be said to increase at the square of the force applied.

This weapon would be best applied to specific hard targets (fn7) where maximum localized damage was considered more important than broad-based damaged to broader concentrations of soft targets (fn8). Its unique nature defeats normal aftermath analysis and can therefore be applied in covert actions freely, though some effort to misdirect investigations may be required in order to insure that no undue attention is placed on the unique blast characteristics or the absence of traditional flash evidence and chemical residues.

The third and final explosion, which to an observer would be seen as a second explosion due to the mere milliseconds of delay between the first two, is timed to coincide with maximum effectiveness of the expanding cloud. The cloud's expansion rate falls off at the square of the distance from the explosion (fn9). For a devices relatively small in size, a proper cloud of suitable destructive capability could be achieved in a relatively few seconds initial expansion.

Anything within the targeted blast area, is pulverized by the highly focused nature of what would otherwise be viewed as a relatively small blast. The damage effect is not dissimilar to the visual of an explosion under water, where a violent and rapid expansion takes place and then collapses inward on itself. In this case, however, as are no great hydraulic pressures to contend with, the greatest destruction takes place within a focused perimeter, as a normalized shock wave continues on. The collapse and shock waves, relative to the size of the large-volume gaseous bomb - is a remarkably lesser pressure more in keeping with the size of the original compact device.

Timing is provided by a barometric device (fn10) which senses the normalization in pressures as the cloud thins at the base and air rushes back to fill the void - the point where expansion begins to falter against air seeking to rush back into the void created by the first explosions. Remember the under-water explosion visual. The final detonating device, along with timing controls and bomb activation and triggering mechanisms for the entire weapon, is housed in an bomb base which remains in tact on the ground after the first two explosions. Resting on legs of wood, plastic, or Teflon, it is electrically insulated, though there is a ground wire established for the final triggering circuit.

While it contains a battery to operate the initial timing and triggering circuits, it also contains a quartz-crystal-based piezoelectric device (fn10) capable of producing many thousands of volts of electricity when "flexed", a phenomenon which occurs naturally as a result of the downward force of the first and second explosion against the housing. This generates a large and very high-voltage charge which temporarily has no where to go, the crystal becoming its own capacitor. At a given point, the barometric timing device trips, and the charge runs up mono-filament wires attached to the bottom half of the outer casing. As the casing is thrown high into the air, the filaments are spiraled out from spools built into the base using technology and parts borrowed from wire-guided surface missiles. When the circuit is closed, these carry the charge to the cloud to produce the final, devastating explosion.

A design variant can apply the final voltage to bare filaments to create a flash-bulb effect which ignites the explosion simultaneously about a vertical column above ground zero. Alternatively, by use of heavier insulated wires stripped bare at a given point, the ignition can be caused to originate at any point between the base and the high-flying lower casing. Finally, the charge could also be applied either from the base itself for traditional blast effects, or from a peripheral position to the cloud (if calculations of cloud size and shape were adequate) for an unusual laterally-focused blast effect. However, this would be a tougher challenge to figure out and control ignition points and timing, especially since variables such as wind patterns and intensity, and air displacements from nearby structures, would need to be considered. Regardless of the focus method employed, because piezoelectric charges are only high in voltage, but not in amperage, the insulated wires do not fuse, and can carry the voltage in tact to its intended destination for ignition.

This bomb design can be subject to great miniaturization. It is possible to build a bomb the size of a soda pop can (with simplified design components, such as use of blasting caps) for use in any precise target application. It might conceivably even be made to look like an innocent pop can with the pull tab actually triggering the bomb, creating a number of interesting options for delivery and detonation. To bring down an aircraft, for instance, simply leave such a device in the magazine pouch of the seat back and exit the aircraft awaiting a passenger, at some point, to discover it and ask for some ice.

The fingerprint of a small-scale METC device applied in an aircraft or other enclosed environment like floors in a building would be minuscule traces of PDTN but no real traditional signature of explosives at all -- no flash damage, no normal residue levels. There would be mostly fire damage of mysterious origin, and since the blast origin point would be the full size of the cloud (most of the cabin or floor), there would seem no blast point or traditional bomb damage at all -- just as if the aircraft or building "went to pieces". Investigators would be hard pressed to conclude explosives as the means of destruction.

Likewise, the bomb could enjoy great economy of scale as a weapon of mass destruction, conceivably on a nuclear scale, but without traditional radiation problems. This would have significant strategic significance as targets could safely be occupied by troops immediately after attack. Separate studies are under way to deal with the impact of such technology on military planning and foreign policy (fn11).

At this time, construction techniques and quality control requirements remain highly sophisticated and at a level which would defy normal mass production. Unless willing to accept significant performance loss, it requires custom design and construction for any given application. As such, it lends itself to uses perhaps best appreciated by the intelligence apparatus. Therefore, its existence should not become general knowledge within other agencies such as DOD (fn12) unless further studies can find such a move advantageous. However, since the unique characteristics of the bomb could conceivably arouse great curiosity in aftermath investigations, its use as a covert tool should be undertaken with great restraint and reserved for highly selective application.