Novel techniques for improved munitions development 44 th annual Gun and Missile system conference Gert Scholtes
Overview • Introduction • I Propellants and • II Ignition of LOVA propellants • III Multi-mode warheads and • IV EFI systems • Summary 2 Gert Scholtes April 2009
Introduction • Modern Military operations put high requirements on Munitions • IM requirements (comparable performance ) • be inexpensive, • Better performance (e.g. extended range munitions), • decreased barrel erosion, • temperature independent performance, • Multi-mode or scalable functionality for MOUT intervention • reliable (# UXO’s) and • have a long lifetime 3 Gert Scholtes April 2009
I Propellants • Less Sensitive, • more performance, • decreased barrel erosion and • temperature independent • Solution: Co-layered propellants • Advantage: improvement of gun performance by enlargement of the impulse on the projectile • Manufacture: • Disadvantage: • Difficult • Time-consuming • TNO’s approach: co-extrusion 4 Gert Scholtes April 2009
Co-layered propellants Ritter, ICT 2007 (some) Advantages (note: not multi-perforated grains!) • Increased performance • Decreased erosivity of high energy propellants • Increased ignition behaviour (e.g. LOVA propellants) • A wide variation in geometries-> implying a larger number of possible applications 5 Gert Scholtes April 2009
Performance: Co-layer vs. Conventional • Examples of simulated performance effects 2 propellants: 7-perf; T f (core) = 3515 K; T f (layer) = 2900 K factor burning rates = 2 350 4500 350 1200 pressure pressure 300 4000 300 1000 gas temperature V(projectile) [m/s] 250 3500 250 800 T(gas) [K] P [MPa] 200 3000 P [MPa] 200 600 150 2500 150 400 100 2000 100 projectile 50 1500 200 50 velocity 0 1000 0 0 0 0.005 0.01 0.015 0 0.005 0.01 0.015 Time [s] Time [s] P conv. P co-layer T conv. T co-layer P conv. P co-layer T conv. T co-layer � T max = 3040 K Barrel lifetime = 3385 K without ‘cool’ outer layer increase ≈ factor 2 6 Gert Scholtes April 2009
Results of Co-extrusion of co-layered propellants at TNO • Improved die-design using special simulation software in 2007 (applying available knowledge from polymer processing) • Die is very important for this process Co-extruded LOVA propellant Co-extruded DB propellant 7 Gert Scholtes April 2009
Results of Co-extrusion of co-layered propellants at TNO Bond integrity at high pressures: � Closed vessel tests with DB single-perforated co-extruded grains • Manufacturing: • Excellent distribution of both layers • Excellent bonding • Also at high pressure (260 MPa) 6.8 mm 8 Gert Scholtes April 2009
Future developments • Double ram press Alternative ram extrusion set-up • Well controllable process • Inner and outer layer can be variable (i.e. composition and size) • No dramatic change of facilities • Continuous co-extrusion (twins-screw extruder) 9 Gert Scholtes April 2009
II Less vulnerable: LOVA propellant-> ignition problem • LOw Vulnerability propellants • Burning behaviour (Vieille’s law): r = β × P α α ≈ 0.6 – 1.0 • Conventional (NC-based) α ≈ 1.0 – 1.4 • ‘LOVA’ (RDX-based) r • Two-step ignition process: • Endothermic pyrolysis of binder • Exothermic combustion Pressure � ignition phase LOVA’s: low pressure � low burning rate � lengthy and variable ignition delays 10 Gert Scholtes April 2009
Test results – mis-fires • Mis-fire: insufficient igniter output for ignition of the propellant • Grain surface melts initially, recovered grains stick together • Tiny droplets of igniter (BP) combustion products on grain surface 11 Gert Scholtes April 2009
Ignition delays and improved igniter composition Single Base Prop +BP LOVA +BP 20°C -40°C 20°C -40°C LOVA / Alternative Igniter Propellant 12 Gert Scholtes April 2009
Propellants: Testing facilities • Closed Vessels • Erosivity & burning interruption tests • Gun simulator • Laboratory Guns Closed VesselsV’s • Plasma ignition (25 – 700cc) 45 mm twin-screw Vented HPCV and catch tank extruder 13 Gert Scholtes April 2009 Plasma ignition
III Multi-mode warheads • Solutions: • Programmable fuzes • Warhead design • Complex ignition systems • The MEDEA programmable fuze is intended for use against (see Figure): • Fast patrol boats FIAC • High diver missiles • Sea skimming missiles • Fixed wing aircraft • Rotary wing aircraft DIVER / DIVER / DIVER / AIRCRAFT AIRCRAFT AIRCRAFT HOB HOB HOB • Surface vessels B-ROLE B-ROLE B-ROLE SURFACE SURFACE SURFACE LAND TARGET LAND TARGET LAND TARGET TARGET TARGET TARGET FPB FPB FPB SEASKIMMER SEASKIMMER SEASKIMMER 14 Gert Scholtes April 2009
Multi-mode warheads: e.g. EFP 190 180 80 50 30 100 1 • Changing location of ignition • EFP mode 100 30 80 4 2 • Streched EFP • Fragments 3 • Aimable warhead 1 V frag =high 15 Gert Scholtes April 2009
Forming of warhead (aimable) • 3 mm plastic explosive, buffer: 1 layer rubber (PBXN-109) • After forming: ignition Fragments 16 Gert Scholtes April 2009
Aimable warheads: 2-Point initiation vs single V max = 2700 m/s Fragment velocity V max = 2000 m/s 17 Gert Scholtes April 2009
190 180 80 50 30 100 Multi-mode warheads: e.g. SC 1 • Shaped Charge or • EOD Shaped Charge 100 30 80 4 2 • Initiation of Explosives 3 • v 2 d=constant [Held criteria] 81 mm SC • V= velocity of tip and d = diameter 0,009 0,008 d of jet (V in km/s and d in mm) 0,007 0,006 Jet diam [m] 0,005 0,004 • PBXN109: 49 BSDT 0,003 0,002 • I-PBXN109: 92 BSDT 0,001 0 0 2 4 6 8 1 0 1 2 Standoff • For penetration: long jet -> small diameter • For EOD: v 2 d max. so short stand- off -> large diameter • Timing of igniter EFI Igniter • But timing is crucial; Solution: 18 Gert Scholtes April 2009
IV Why an EFI system • An EFI is intrinsically safer than standard initiators (no primary explosive) • More reliable (So, no UXO’s) • Works much faster < microseconds (µs) • Can be smaller (near future) • Is compliant with new STANAG (4560) regulations • New opportunities (tandem charges, aim able warheads etc.) • Disadvantage : More expensive (at the moment) • Future: Micro Chip EFI (McEFI) � inexpensive 5 x 5 mm pellet 19 Gert Scholtes April 2009
Bridge Exploding Foil Initiator Research copper • Exploding foil current • Electrical circuit • Velocity of the flyer Kapton • Driver Explosive Acceptor • Secondary flyer Explosive • Acceptor explosive Secondary flyer Driver Explosive Barrel T S insulation Copper foil C Kapton foil 20 Gert Scholtes April 2009
Conclusions mini EFI and Mc EFI development platform • A very efficient electrical circuit ( η = 50 � 90% ) • Mini-EFI Works at Voltage < 1300 Volt (Solid state switch) • With “of the shelf components” small IM compliant EFI-detonators can be built (~8cm 3 including High Voltage-supply) • Secondary flyers makes the detonation train more reliable (in case of set-back) • Successful initiation of TATB and RDX with several types of flyer materials • Combining the EFI with the ESAD with Micro Chip technology can make a small and cost effective unit • Solution for complex ignition system (multi-mode warheads) 21 Gert Scholtes April 2009
Summary • Modern Military operations put high requirements on Munitions • Innovation in munitions' development can give the answer, examples: • Co-layer propellants (co-extrusion) • Ignition of LOVA propellant • Multi-mode warheads and programmable Fuzes • Technical solutions can help to address the challenges for your future munition developments 22 Gert Scholtes April 2009
•TNO Defence, Security and Safety •The Netherlands Gert Scholtes Tel: +31 15 284 3619 Email: gert.scholtes@tno.nl 23 Gert Scholtes April 2009
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