Gert Scholtes
44th annual Gun and Missile system conference
Novel techniques for improved munitions development
April 2009Gert Scholtes2
Overview
• Introduction
• I Propellants and • II Ignition of LOVA propellants• III Multi-mode warheads and • IV EFI systems
• Summary
April 2009Gert Scholtes3
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
April 2009Gert Scholtes4
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
April 2009Gert Scholtes5
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!)
April 2009Gert Scholtes6
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
0
50
100
150
200
250
300
350
0 0.005 0.01 0.015
Time [s]
P [M
Pa]
0
200
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600
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1200
V(pr
ojec
tile)
[m/s
]P conv. P co-layer T conv. T co-layer
pressure
projectilevelocity
0
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350
0 0.005 0.01 0.015
Time [s]
P [M
Pa]
1000
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3500
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4500
T(ga
s) [K
]
P conv. P co-layer T conv. T co-layer
pressure
gas temperature
Barrel lifetime increase ≈ factor 2
April 2009Gert Scholtes7
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-extrudedLOVA propellant
Co-extruded DB propellant
April 2009Gert Scholtes8
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
April 2009Gert Scholtes9
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)
April 2009Gert Scholtes10
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
April 2009Gert Scholtes12
Ignition delays and improved igniter composition
-40°C20°C
20°C
-40°C
LOVA / Alternative Igniter Propellant
Single Base Prop +BP
LOVA +BP
April 2009Gert Scholtes13
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
April 2009Gert Scholtes14
III Multi-mode warheads• Solutions:
• Programmable fuzes• Warhead design• Complex ignition systems
• The MEDEA programmable fuze is intended for useagainst (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-ROLEHOB
FPB
LAND TARGET
SEASKIMMER
DIVER / AIRCRAFT
SURFACE TARGET
B-ROLEHOB
FPB
LAND TARGET
SEASKIMMER
DIVER / AIRCRAFT
SURFACE TARGET
B-ROLEHOB
FPB
LAND TARGET
April 2009Gert Scholtes15
Multi-mode warheads: e.g. EFP
• Changing location of ignition• EFP mode• Streched EFP• Fragments• Aimable warhead
50 30 10080
180190
30
80
10
0
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
April 2009Gert Scholtes17
Aimable warheads: 2-Point initiation vs single
Vmax= 2000 m/s
Vmax= 2700 m/s
Fragment velocity
April 2009Gert Scholtes18
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
of 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-off -> large diameter
• Timing of igniter• But timing is crucial; Solution:
50 30 10080
180190
30
80
10
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0,001
0,002
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0 2 4 6 8 10 12
Standoff
Jet d
iam
[m]
81 mm SCd
EFI Igniter
April 2009Gert Scholtes19
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
April 2009Gert Scholtes20
Exploding Foil Initiator Research
• Exploding foil• Electrical circuit• Velocity of the flyer• Driver Explosive • Secondary flyer• Acceptor explosive
T
S
C insulation Copper foilKapton foil
Driver Explosive
Acceptor Explosive
Barrel
Secondary flyer
Kapton
coppercurrent
Bridge
April 2009Gert Scholtes21
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 RDXwith several types of flyer materials
• Combining the EFI with the ESAD with Micro Chiptechnology can make a small and cost effective unit
• Solution for complex ignition system(multi-mode warheads)
April 2009Gert Scholtes22
Summary
• Modern Military operations puthigh 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
April 2009Gert Scholtes23
•TNO Defence, Security and Safety
•The NetherlandsGert Scholtes
Tel: +31 15 284 3619
Email: [email protected]
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