Novel techniques for improved munitions development 44 th annual Gun - - PowerPoint PPT Presentation

Gert Scholtes

44th annual Gun and Missile system conference

Novel techniques for improved munitions development

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Overview

• Introduction
• I

Propellants and

• II

Ignition of LOVA propellants

• III

Multi-mode warheads and

• IV

EFI systems

• Summary

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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

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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

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Co-layered propellants

(some) Advantages

• 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

Ritter, ICT 2007 (note: not multi-perforated grains!)

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Performance: Co-layer vs. Conventional

• Examples of simulated performance effects

2 propellants: 7-perf; Tf(core) = 3515 K; Tf(layer) = 2900 K factor burning rates = 2

Tmax = 3040 K

= 3385 K without ‘cool’ outer layer

50 100 150 200 250 300 350 0.005 0.01 0.015 Time [s] P [MPa] 200 400 600 800 1000 1200 V(projectile) [m/s] P conv. P co-layer T conv. T co-layer pressure projectile velocity 50 100 150 200 250 300 350 0.005 0.01 0.015 Time [s] P [MPa] 1000 1500 2000 2500 3000 3500 4000 4500 T(gas) [K] P conv. P co-layer T conv. T co-layer pressure gas temperature

Barrel lifetime increase ≈ factor 2

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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

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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

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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)

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II Less vulnerable: LOVA propellant-> ignition problem

• LOw Vulnerability propellants
• Burning behaviour (Vieille’s law): r = β × Pα
• Conventional (NC-based)

α ≈ 0.6 – 1.0

• ‘LOVA’ (RDX-based)

α ≈ 1.0 – 1.4

• Two-step ignition process:
• Endothermic pyrolysis of binder
• Exothermic combustion

ignition phase LOVA’s: low pressure low burning rate lengthy and variable ignition delays Pressure r

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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

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Ignition delays and improved igniter composition

• 40°C

20°C

20°C

• 40°C

LOVA / Alternative Igniter Propellant Single Base Prop +BP LOVA +BP

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Propellants: Testing facilities

• Closed Vessels
• Erosivity & burning interruption tests
• Gun simulator
• Laboratory Guns
• Plasma ignition

Vented HPCV and catch tank

Closed VesselsV’s (25 – 700cc) 45 mm twin-screw extruder Plasma ignition

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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
• Surface vessels

SEASKIMMER DIVER / AIRCRAFT SURFACE TARGET B-ROLE HOB FPB LAND TARGET SEASKIMMER DIVER / AIRCRAFT SURFACE TARGET B-ROLE HOB FPB LAND TARGET SEASKIMMER DIVER / AIRCRAFT SURFACE TARGET B-ROLE HOB FPB LAND TARGET

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Multi-mode warheads: e.g. EFP

• Changing location of ignition
• EFP mode
• Streched EFP
• Fragments
• Aimable warhead

50 30 100 80 180 190 30 80 100 1 2 3 4

1

Vfrag =high

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Forming of warhead (aimable)

• 3 mm plastic explosive, buffer: 1 layer rubber (PBXN-109)
• After forming: ignition

Fragments

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Aimable warheads: 2-Point initiation vs single

Vmax= 2000 m/s Vmax= 2700 m/s Fragment velocity

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Multi-mode warheads: e.g. SC

• Shaped Charge or
• EOD Shaped Charge
• Initiation of Explosives
• v2d=constant [Held criteria]
• V= velocity of tip and d = diameter
• f jet (V in km/s and d in mm)
• PBXN109:

49 BSDT

• I-PBXN109:

92 BSDT

• For penetration: long jet -> small

diameter

• For EOD: v2d max. so short stand-
• ff -> large diameter
• Timing of igniter
• But timing is crucial; Solution:

50 30 100 80 180 190 30 80 100 1 2 3 4 0,001 0,002 0,003 0,004 0,005 0,006 0,007 0,008 0,009 2 4 6 8 1 1 2

Standoff Jet diam [m]

81 mm SC d

EFI Igniter

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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

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Exploding Foil Initiator Research

• Exploding foil
• Electrical circuit
• Velocity of the flyer
• Driver Explosive
• Secondary flyer
• Acceptor explosive

T S C insulation Copper foil Kapton foil

Driver Explosive Acceptor Explosive

Barrel Secondary flyer

Kapton copper current Bridge

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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 (~8cm3 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)

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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

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• TNO Defence, Security and Safety
• The Netherlands

Gert Scholtes Tel: +31 15 284 3619 Email: gert.scholtes@tno.nl