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Advanced Warhead Design

Description:

OBJECTIVE: The objective of this effort is to design of warheads to defeat contact fuses on RAM targets using compression wave overpressure. The analysis shall include details and test results of compression wave overpressure by advanced explosives and size/weight of warheads as a function of compression wave overpressure. Computational fluid dynamics (CFD) calculations will be required to predict the effects of closing velocity between munitions and target on the effectiveness of the warhead. DESCRIPTION: The Counter Rockets, Artillery, and Mortar (C-RAM) program office is developing advanced systems to sense, warn, and engage rockets, artillery, and mortars (RAM). Gun and missile systems are currently being used to engage these threats. The warheads on these targets are made of relatively thick steel; therefore are difficult to defeat except for direct hits on the fuse. The probability of hitting the fuse with gun bullets or missile warhead fragments is very small; therefore usually not an option. U.S. Army Space and Missile Defense Command (SMDC) and U.S. Army Engineer Research and Development Center (ERDC) demonstrated the potential for compression wave overpressure initiation of typical foreign mortar contact fuses. Experiments were conducted on three fuse types: 1) point detonating fuse used on 60mm, 81mm, and 82mm mortars from Country A [1]; 2) point detonating fuse used on 60mm, 81mm, and 82mm mortars from Country B [1]; and 3) point detonating with optional delay typically used on 120mm mortars, see reference [1] for detailed description of these types of fuses. The fuses were tested at various standoff ranges from C-4 charges; see reference [2] for detailed experimental design. The fuses were inerted and instrumented to detect plunger movement that indicated go/no-go on initiation. Instrumentation included fuse tip pressure measurements on simulated fuses placed at the same standoff range and orientation to the explosion as the fuses under test. Conditions of the test: 1) one fuse orientation (nose on-axis to the explosive) was used; 2) tests were static (no inclusion of closing velocity effects on fuse tip overpressure); 3) atmospheric effects were not considered; and 4) fuses were inerted to instrument the firing system. ERDC developed a structural response model of fuse firing pin system to calculate overpressures required for fuse initiation. This model was used in the experiment design and to calculate Iso-Response curves in Pressure-Impulse space for combinations of pressure and impulse that cause initiation of the fuse firing mechanism. The computer code ConWep based on weapons effects algorithms described in reference [3] was used to predict pressure and impulse as a function of range for the C-4 explosives as part of the experimental design. These predictions were in agreement with the pressures and impulses measured in the tests. Tests results showed that fuse initiation occurred at ranges of 1.5 meters from 5-lb of C-4 explosive with the two 60mm, 81mm, and 82mm mortar fuses and 0.75 meters from 10- lb of C-4 explosive with the 120mm mortar fuse. As a follow on to the tests, Computational Fluid Dynamics (CFD) code Gemini [4] was used to predict the effect of closing velocity between a missile and its target on the pressure and impulse experienced by fuses. Calculations were performed for closing velocity of 1000 meters per second between warheads (explosive) and fuse. The predicted impulse was 3 times the impulse in the static measurements. The results of these tests and analyses demonstrated that blast pressure initiation of RAM fuses is a promising defeat mechanism worthy of further phenomenology research. The objective of this effort is to extend the work performed by ERDC and SMDC leading to the design of warheads to defeat contact fuses on RAM targets using compression wave overpressure. The analysis shall include details and test results of compression wave overpressure by advanced explosives and size/weight of warheads as a function of compression wave overpressure. Computational fluid dynamics (CFD) calculations will be required to predict the effects of closing velocity between munitions and target on the effectiveness of the warhead. PHASE I: The offeror shall perform studies on explosives that have maximum wave front compression ratios. The offeror shall design a warhead using the selected explosives and perform preliminary analysis on the designs. The offeror shall develop an experimental concept validation and data for development of a CFD model for fuse overpressure kill phenomenon. PHASE II: The offeror shall develop a detailed simulation of the proposed warhead designs and missile/warhead engagement geometries. The simulation shall include CFD simulation of the effect of closing velocity on the compression wave overpressure. The offeror shall perform a detailed analysis of blast overpressures achieved in different engagement scenarios with the warhead against a variety of RAM targets. The offeror shall determine the type of explosive and amount of explosive (weight) required to defeat the fuses on these warheads. The offeror shall, in corporation with ERDC, develop a plan to develop and test the warhead design. The offeror shall perform preliminary warhead testing at ERDC facilities to validate simulations. These tests shall include dynamic rocket-sled experimentation that include closing rate effects for full fuse/blast field interaction. The offeror shall document the warhead designs and simulation test results in a final report. PHASE III: The offeror shall develop and test warheads in corporation with ERDC. The final design will be marketed to the C-RAM program office and other related services. The resulting compression wave overpressure models can be marketed to commercial companies designing and building structures to withstand warhead blasts. REFERENCES: 1. Gauder,T. and C. Cutshaw, ed. 2000. Jane"s Ammunition Handbook 2000-2001. 9th ed., Alexander, VA: Jane"s Information Group. 2. Thomas E,. McGill, Toney K. Cumins, Nicholas R. Boone, Michael J. Roth, Thomas R. Slawson, Bartley P. Durst, and Pamela G. Kinnebrew, Investigation into the Effectiveness of Airblast Initiation of Point-Detonating Mortar Fuzes, U. S. Army Engineer Research and Development Center, Vicksburg, MS 2010. 3. Department of the Army, Fundamentals of Protective Design of Conventional Weapons, Technical Manual 5-855-1, 1986. 4. Gemini user manual, release 4.30, U.S. Naval Surface Warfare Center, Indian Head, MD , 2005.
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