Pickett s Charge. George McAllister, Principle Manager Asymmetric Threat Technologies. June 11-14, 2007

Transcription

1 Pickett s Charge George McAllister, Principle Manager Asymmetric Threat Technologies June 11-14, 2007

2 IED Problems IED Problems A prominent feature of IEDs currently used by enemy forces against U.S. forces in Afghanistan and Iraq is their roadside application in attacking vehicle convoys. Terrorists continue to build devices that have destroyed our most powerful conventional warfare systems Abrams tanks and Bradley fighting vehicles for a very small investment in time and materials. Over 50% of the casualties in OPERATION IRAQI FREEDOM are a result of IED attacks. While much has been done to provide our warfighters with improved body armor, up armored HMMWVs, and CREW systems, the problem of concussion injury and damage remains. Reference: The Asymmetric Warfare Group: Closing the Capability Gaps, Lt. Gen. James J. Lovelace Jr. & Brig. Gen. Joseph L.Votel, Army Magazine, March 2004

3 Concussion Injuries Concussion Injuries Almost 18,000 troops have been wounded according the Department of Defense. The VA doctors say that twothirds of them have been injured by IED blasts and twothirds of those exposed to blasts suffer some brain injury -- ranging from a mild concussion to permanent damage. Brain injuries - thousands of them - could be the legacy of this war just as much as post-traumatic stress and problems from exposure to Agent Orange persisted among many of the troops who served in Vietnam*. As early as 2004, when Army doctors examined soldiers wounded in Iraq, they found 62% also had undiagnosed concussion injuries. * Reference: Center for Brain Injury Recovery

4 What is Pickett s Charge? What is Pickett s Charge? Pickett's Charge is a counter-concussion active protection system. Pickett s Charge is not intended to replace existing defensive counter-measures, such as armor. Rather, it is meant to supplement existing defensive systems allowing them to work more efficiently, saving lives and reducing vehicle damage.

5 Phenomenology Exploited Phenomenology Exploited Basic physics Wave interference is the phenomenon which occurs when two waves meet while traveling along the same medium. Can intentional concussion waves be used to interfere or counter the effects of IED blast, concussion and fragmentation Using directional explosive charge employed on a moving vehicle to deflect, degrade, and/or counter the effects of blast and fragmentation hazards produced by an exploding enemy roadside IED? The theory is sound and the physics does work.

6 How Does Pickett s Charge Work? How Does Pickett s Charge Work? Pickett s Charge operates in the time interval between IED initiation (no matter how the device is initiated) and the time that the destructive force reaches the targeted vehicle or personnel. Although this time interval is short, it is sufficient for operation of a countermeasure consisting of ultra-responsive pressure transducers, high speed initiation systems, and shaped charges.

7 Detonation Pressures Detonation Pressures High-order explosives detonate quickly, generate heat and fill the space with high pressure gases in 1/1000 th of a second producing a supersonic overpressurization shock wave that expands from the point of detonation which moves outward in a pressure pulse. This "blast wave" (positive wave) moves in all directions, exerting pressure of up to 700 tons. At the point of detonation, this overpressurization causes the surrounding displaced air to form a small pressure spike. The displaced air then compresses and forms a vacuum returning to the point of detonation (negative wave).

8 Blast Waves Blast Waves The small pressure spike of compresseddisplaced air moving out in front of the main overpressure is the secret to Pickett s Charge. Peak Pressure Main Blast Wave Overpressure Negative Pressure Wave Compressed Displaced Air Pulse Duration

9 Basic System Description Basic System Description A fast-reacting sensor, capable of sensing/detecting the front of an oncoming pressure wave from an IED detonation, is mounted on the outside of a vehicle. Upon sensing this pressure wave, a directional counter charge is fired within microseconds (theoretically, nanoseconds). This directional counter charge, operating similar to the Explosive Reactive Armor, serves two distinct functions: 1. The counter charge s outgoing pressure wave would theoretically intersect, offset, and deflect the oncoming pressure wave thus reducing the impact of shock waves on the vehicle and personnel. 2. The counter charge could also theoretically propel a mass at a velocity greater than the roadside IED detonation velocity that would significantly intercept, deflect, and/or reduce the Translational Kinetic Energy of fragmentation from the oncoming IED, (including EFPs) resulting in reduced blast pressure and lower kinetic energy fragmentation.

10 Pickett s Charge Design Pickett s Charge Design Pickett s Charge is designed to provide a controlled directional counterforce to enemy IED attacks. It is designed to be small and easily installed. Once the mounting hardware and wiring is in place, replacement of an expended Pickett s Charge can be accomplished by the vehicle operator as a snap-in replacement.

11 Pickett s Charge Design Pickett s Charge Design Damping is designed and built into the charge mounts, which remain permanently affixed to the vehicle and can be swapped out in the field. The charge itself is designed to be a snap in unit so that it can be installed quickly when needed for convoy operations or other missions. This maintains simplicity in field maintenance by removing the need to accomplish vehicle alterations each time the charge is installed.

12 Pickett s Charge Technical Analysis We analyzed the timing of a typical IED in theater versus the timing of Pickett s Charge. Pressure transducer response time on the order of microseconds Detonator will fire with several microsecond responses Recommend the use of high speed discrete logic to reduce latency time Included in the analysis were the parameters at which pressure waves can be detected. Pickett s Charge is feasible and can react in sufficient time to intercept IED blasts.

13 T-0 Start of IED detonation Timing Feasibility Graphic Timing Feasibility Graphic 200 us = Typical time an M6 blasting cap bridgewire can heat up to 300ºC the point when the solid bridgewire turns to a molten gas 0 sec 200 us Blast & Frag moving from IED towards Target Vehicle 50.8 us per foot with Enemy HME 100 us = Typical time for a bridgewire electric detonator to completely function and initiate the primary explosives 2 us = Typical time for the blast overpressure to reach peak pressure 300 us 302 us Point of detection/start of the firing of Pickett s Charge PC pressure wave moving from vehicle towards IED T-0 Start of Pickett s Charge detonation 0 sec 2 us for the electronics slope detector.2 us = Pressure sensor rise reaction time 2 us 33.8 us per foot with HMX PC 2.2 us 1 us = Capacitor discharge time to fire EFI 3.2 us 1.06 us = Complete function time of RP-97 EFI 4.26 us 2 us = Typical time for the blast overpressure to reach peak pressure 6.26 us *all times are in Microseconds

14 Comparison of Components and Time Factors Typical IED Components and Time Factors 200 us = Typical time an M6 Blasting cap bridgewire can heat up to 300ºC with a 12volt power supply. *300ºC is the point when the solid bridgewire turns to a molten gas 100 us = Typical time for a bridgewire electric detonator to completely function and initiate the primary explosives with <50 VDC 2 us = Typical time for the blast overpressure to reach peak pressure 50.8 us per foot for HME detonation velocity and pressure wave velocity (6000 m/sec) Pickett s Charge Components and Time Factors.2 us = Pressure sensor rise reaction time using PCB Piezotronics Model 134A pressure sensor 2 us = Electronic time for slope detector to determine not only that a threshold value has been reached but that it has been reached in a certain time period to minimize false triggering of Pickett s Charge 1 us = Capacitor discharge time for firing EFI detonator 1.06 us = Complete function time of RISI RP-97 Explosive Foil Initiator 2 us = Typical time it takes for the blast overpressure to reach peak pressure 33.8 us per foot for HMX detonation velocity and pressure wave velocity (9110 m/sec)

15 Burdens Weight Weight of the permanently affixed hardware is estimated to be approximately 20 lbs or less, depending on the material of the springs. Weight of shaped charge and packaging should be less than 2 lbs. Power Requirements Will be powered from vehicle power system. Detection electronics will draw minimal power (milliamps). Detonation circuit will utilize pre-charged capacitor.

16 Fratricide Considerations Fratricide Considerations Considerations Vehicles equipped with Pickett s Charge would have to operate with the same considerations as existing vehicles equipped with reactive armor. Issues Pressure measurement sensitivity must be optimized to avoid inadvertent initiation. Can incorporate secondary blast detection techniques such as rate of temperature change. Safeties to prevent fratricide An automatic safety system tied to vehicle movement Control panel within the vehicle compartment to allow disabling of the system in friendly areas Use of energetic material such as C4 assures material stability

17 Safety and Certification Issues Safety and Certification Issues System should be HERO tested to ensure safe operation in the presence of communications equipment and other RF emitters Should have a minimum of double (triple preferred) fault tolerance to prevent against inadvertent detonations Charge with detonator should be certified to withstand static discharge Should be tested using the following specifications as guidance: MIL-STD-237C, Electromagnetic Environmental Effects and Spectrum Certification Guidance for the Acquisition Process MIL-STD-461E, DOD Interface Standard Requirements for the Control of Electromagnetic Interference Characteristics of Subsystems and Equipment

18 Technical/Risk Issues and Planned Engineering Solutions How does Pickett s Charge address inadvertent firing? The threshold of the pressure sensor is set to kilobars, much higher than normal pressure anomalies. Will also utilize pressure change rate determination and potential temperature rate of change. How does Pickett s Charge address possible firing towards friendly vehicles? Through a selectable control panel mounted in the vehicle the operator can check continuity and arm or disarm the desired or undesired mounted charges, as well as use a command detonated feature to breech roadblocks. How does Pickett s Charge address the possible firing in the event the vehicle is not in tactical convoy mode? Either through the control panel if vehicle is running, or through disengagement of sensors and firing circuit when the vehicle is shut off.

19 Technical/Risk Issues and Planned Engineering Solutions What is the recommended tactical employment of Pickett s Charge? The lead vehicle should have the front-mounted and both flank mounted charges armed. Every third vehicle beyond that should have the two flanked charges armed. The last vehicle should have both flank charges armed and a rear-mounted charge armed. Charges should be replaced after counter charge employment. How does Pickett s Charge address the recoil and back blast of the counter charge? Through innovative recoil dampening and armor protection. How does Pickett s Charge get mounted / remounted? Mounting will be in a quick disconnect fashion. The armor shield will be permanently affixed to the vehicle, with the actual counter charge and sensors attachable. Connect the counter charge and connect the electrical connection, start the vehicle, clear the area and test continuity. For replacement, disconnect the spent counter charge electrical connection, remove spent counter charge housing, replace new counter charge assembly, connect the electrical connection, start the vehicle, clear the area and test continuity through control panel.

20 Performance Metrics Performance Metrics Should be able to counter an IED explosive blast over 50 kilobars at 2 inches or greater distance. Response time of Pickett s Charge should be less than 5 microseconds (theoretically nanoseconds), including detonation.

21 Conclusions Pickett s Charge physics support the concept. Within 4.26 us after a pressure wave is detected, Pickett s Charge can be deployed. As long as Pickett s Charge can detect the pressure wave within a conservatively sufficient ~ 2 inches away from the vehicle, Pickett s Charge can be fired and intercept the IED blast wave. (For HME the distance required for pressure detection is 1 inch to allow sufficient time to fire Pickett s Charge.)

22 Questions???

23 Back-up slides Back-up slides

24 Threats Addressed Threats Addressed Pickett s Charge is a directional counter charge intended to interact against multiple IEDs simultaneously. With a counter charge effect working against the oncoming effects of the IED, the existing protective measures of the vehicle and personnel armor would have improved survivability characteristics against: Blast Concussion Fragmentation As we ve improved our armor, the enemy s improved his IED s - Major Simmons, Army National Guard

25 RISI RP-97 EFI Detonator RISI RP-97 EFI Detonator RP-97 Sealed EFI Detonator P/N The RP-97 Exploding Foil Initiator (EFI) is a medium cost detonator designed for applications where an EBW detonator is not acceptable. RP-97 FIRING PARAMETERS Threshold Voltage: Approx volts with 0.25 µfd Capacitor Threshold Voltage Std. Deviation: 50 volts maximum Function Time: Approx µsec

26 PCB Piezotronics PCB Piezotronics Model 134A Tourmaline pressure bar, 10k psi, 0.12 pc/psi, charge output, 0.2 µs rise time (reflected shock wave) Measurement Range: psi (68950 kpa) Sensitivity: (±15%) pc/psi (0.018 pc/kpa) Temperature Range: (Operating) -32 to +120 F (-36 to +49 C) Electrical Connector: Coaxial Jack Weight: 0.98 oz (28 gm)

27 Explosive Detonation Velocities Explosive Detonation Velocities EXPLOSIVE DETONATION DENSITY SENSITIVITY VELOCITY PRESSURE m/sec kilobars/psi HMX / /pressed Moderate LX /pressed Moderate LX /pressed Moderate PBX /pressed Moderate RDX /pressed Moderate PETN /pressed High Cyclotol /cast Low Comp B 63/ /cast Low TATB /pressed Very Low PBX /pressed Very Low DATB /pressed Low HNS / /pressed Low TNT / /cast Low *HME cast Low Baratol 76/ /cast Moderate Boracitol 60/ /cast Low Plumbatol 70/ /cast Moderate *HME= Home made Explosives (used by insurgents in Iraq) reference JIEDDTF ** Table referenced from LANL

28 Los Alamos National Laboratory Peak Overpressure Experimental pressure from 3.63-kg Pentolite cylinders at m height of burst vs. experimental time at a test-scale depth of 0.3 m and test-scale range of 0 m is 2 microseconds.