2.1.3(2) Flashcards
Define Explosion
An explosion is the RAPID DECOMPOSITION of energetic material to produce energy (heat) and gas which will lead to violent pressure rupturing of any confining structure
Define Deflagration
Is a technical term describing subsonic combustion that usually propagates through thermal conductivity (hot burning material heats below colder layer)
Define Detonation
Involves a supersonic exothermic front accelerating through a medium that drives a shock front propagating directly in front of it.
What is Velocity of Detonation? VOD
The rate, in metres per second, at which the wave of detonation passes through an EXPLOSIVE SUBSTANCE
VODs
ANFO 4800 m/s TNT 6950 m/s CE 7160 m/s PETN 8300 m/s RDX 8400 m/s
Factors Affecting VOD
Density of charge
Charge diameter
Degree of confinement
Strength of detonator
Burning To Detonation
Occurs when there is a abrupt acceleration of the flame front, until it becomes a shock wave and the transformation to a detonation is complete
eg. Explosives confined in a tube, where gases cannot escape
Even unconfined explosives, if in sufficient bulk, may generate sufficient pressure to enable the remaining explosives to detonate
Probability Rule
Prob Kill = P Hit x P Reliability x P Lethality
Energy sources available for Ammunition Design
KINETIC energy
CHEMICAL energy
What is a Physical explosion
The catastrophic rupture of a pressurized gas/vapor-filled vessel by means other than reaction
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Problems with KE and CE-combined ammunition?
The problem of initiating the CE source behind armour due to the shock on impact onto any initiating mechanism
Personnel - frag velocity is controlled by what factors? (3)
Amount of explosive behind wall
Charge density and VOD
Density of wall material
What are the types of Ballistic requirements for KE?
Internal ballistics
External ballistics
Terminal ballistics
How does a HESH round work?
Detonate HE in contact with armour
Shock wave travels through plate and reflects back
causes a tension wave
The tension wave meet the primary shock wave, resulting in a scab detaching from the rear of the plate
Scab size?
1.25 to 1.5 times size of weapon’s diameter
What is Reverse Impact Detonation for HESH?
If detonation occurs before the fuze can produce detonation of the filling, the shock wave will be travelling in the wrong direction
Describe how APFSDS works?
Shot fired from weapon
Slipping driving bands reduce spin
sabot is discarded through aerodynamic forces
Hits and penetrates through KE
(KE)
What are the 2 forms of stabilisation?
What are the ideal length:diameter ratios of a projectile applying to forms of stabilisation? (x:x)
Length:diameter
7:1 spin 15:1 fin(might be angles instead?)
How do Shaped Charges work, IOT defeat armour?
- Achieved by hollowing out the front face of a slab of HE IOT give a conical shape.
- The energy from the detonation is directed inward and forward as a GASEOUS JET.
- A metal liner will travel forward with it
- At an extremely high velocity.
Types of Explosions?
Physical (or mechanical)
Chemical
Nuclear
What are Primary Explosives?
Name 3 examples
A primary explosive is an explosive substance which is extremely sensitive to stimuli such as heat, friction and/or shock and which requires special care in handling.
Mecury fulminate, Lead Azide, Lead Styphnate
What are Secondary Explosives?
Name 2 examples
A secondary explosive is an explosive substance which is relatively insensitive to stimuli such as heat, friction and/or shock. (eDEOP)
RDX, TNT
Requirements for Military Explosives (6)
- Performance
- Sensitivity
- Stability & behaviour in storage
- Water Resistance
- Consistency
- Thermal behaviour
Chemical Explosion
An extremely RAPID REACTION of a chemical system to produce heat and gas
The sudden expansion of gases into a volume much greater than the initial one, accompanied by noise and violent movement
Nuclear Explosion
Sudden release of enormous quantities of heat by fission or fusion processes
Define Blast
Phases?
- Violent disruptive effect caused by an explosion.
- From the explosion there is an evolution of heat and gases and a shock front which emanates from the centre of the explosion.
- Shock Front
- Positive Pressure Phase
- Negative Pressure Phase
Dynamic Pressure
Incident Pressure
Dynamic Pressure
Results from the high wind velocity & increased density of the air behind the shock front
Incident Pressure
Pressure exerted at right angles to the direction of travel of the shock front
Quasi Static Pressure
Reflected Pressure
Quasi Static Pressure
-Results when an explosion occurs within a
structure creating overpressure; eventually settles to a slow decaying level
Reflected Pressure
-Instantaneous build up of pressure occurring
when a shock front strikes a rigid surface in
it’s line of travel
2 types of waves created when contacting a surface (2)
What is Mach Stem
Reflection
Diffraction
Mach Stem- reflected wave impacts original
Fuel Air Explosives (FAE) - Basic Principle?
The basic principle consists of:
creating an aerosol cloud of fuel air mixture, by a bursting charge, which is then detonated to achieve an explosive effect.
The blast wave formed inside the cloud and proceeds unabated to the edge of the cloud
The overpressure is therefore very high when the wave is an appreciable distance from the point of initiation
FAE - Types of Fuel (6)
- acetylene
- butane
- ethylene oxide
- kerosene
- propylene oxide
- aluminium
Advantages of FAE (2+)
Disadvantage
ADV
-FAE provides larger overpressures at greater distances than HE would provide
-Requires little or no oxygen in the molecular structure therefore making a FAE explosion 3 to 5 times hotter than HE
DIS-ADV
-Strong winds would prevent the development
of the optimal shape from the initial burst
Types of Targets for FAE (7)
Structures Concentrations of AFV and SP Guns Parked aircraft Minefield clearance Ships Bunkers / trenches Concentrations of troops in the open
Key Target types for target analysis? (3)
People
Attack on Armour
Aircraft in Flight
Types of Aircraft targets? (3)
Fast Moving
Slow moving
Helicopters
Standard Damage Criteria for A/C (6)
Alternate (3)
KK-Kill immediate K 10sec A 5 mins B 5 hours C (mission abort) E complete msn, needs repair
F(t) permanently unable to fly
C(t) Unable to continue
E(t) needs to be grounded for repairs
Areas of Aircraft Vulnerability (8)
Airframe Aircrew Fuel cells Engines Power transmission systems Flight controls Avionics Payload
Reduction of Vulnerable Areas for A/C (6)
Armouring Burying sensitive components Concentrating sensitive components Duplicating components Separating Components Self sealing fuel tanks
Types of Warheads against aircraft? (7)
Blast
Fragmentation (Inefficient --80% Wasted)80% Wasted)
Fragmentation plus blast
Special kinetic energy
-Discrete rod
-Continuous rod
Shaped charges
Sub--projectiles
ClusterEffects of Altitude (4)
Density
Attenuation (weakening of shock wave)
Miss Distance
Altitude increase = Warhead increase
Fragmenting Warheads - How much is wasted?
How to make more efficient?
> 80% wasted, 50% in wrong direction
Preferential Frag warhead direct the frag in a given direction
Pers - Most efficient mode of attack? (3)
- High probability of a hit
- Rapid transfer of energy
- No unecessary overkill
A WOUND is caused by the transfer of energy from fragment to body. The type of wound is dependent on what? (3)
- Amount of energy transferred
- The rate of transfer
- Tumbling/yawing of fragment
List the 3 Fragment producers (Frag design)
- Generic HE projectiles.
- Pre notched containers.
- Pre formed fragments.
Control of the fragments SIZE is ACHIEVED by: (4)
- Case material and its mechanical properties
- Thickness of the wall
- Quantity of explosive and its position in relation to
the fragmenting case - VOD of the explosive.
What is Fragment VELOCITY controlled by?
- Amount of explosive behind the fragment wall
- Charge density and velocity of detonation
- Density of the wall material
What are the factors affecting performance of fragmentation? (4)
Describe.
DOHA
- DISTRIBUTION of frag:
- Spin rate will influence but not pattern
- Usually symmetrical on longitudinal axis
- Angle of arrival - Orientation of projectile
- Effective distribution when angle is vertical
- Increasing amount of frag is projected into the air or
ground as the angle changes - Height of burst
- 2-4 metres is best
- achieved by fuzes - Average area of exposed target
- Target posture
- Terrain
- PPE
Factors affecting RATE of transfer? (4)
Mass
Velocity
Cross sectional area
Stability of the fragment
- Types of Armour Construction (7)
RSPFECS
Rolled homogenous armour Spaced homogenous Ply Face hardened Explosive reactive armour (ERA) Composite (Chobham) Slat (bar)
Tank Damage Assessment Criteria
M -Mobility kill
F -Firepower kill (incl. main armament, ammo, pers)
K -Completely destroyed
APC & MICV (IFV) assessment criteria
F - firepower kill
P - payload kill (Pers in the back)
- List the 3 basic modes / methods of attack to defeat armoured vehicles and fortifications
KCC
- Kinetic energy
- Chemical energy
- A combination of both
Explain Shot Failure - Barrelling
Direct compression failure in the shot material. The
shot bellies at about its mid point
Increase in cross sectional area and the shot fails to
push through.
Explain Shot Failure - Shattering
Raising the hardness of a steel shot, whilst increasing
its compressive strength, makes the shot brittle
On impact severe tensile hoop stresses are set up in the nose of the shot (small cross sectional area)
At high striking velocities, the shot nose can fail under these stresses and longitudinal cracks are formed
Explain Shot Failure - Lateral bending
At high angles of attack the shot is subjected to severe lateral stresses, both particularly towards its rear end.
The effects of these stresses can be reduced by increasing the toughness of the shot towards its rear end and by fitting a toughened steel sheath over the rear end of the shot.
What are ways to Increase Penetration? (5)
- Lengthening of the BARREL
- Lengthening the PROJECTILE
- Rocket Assistance (RA)
- Improve STEADINESS of shot
- Use of segments long rod penetrators
HEAT - Factors affecting Shape Charges (5)
- Cone diameter
- Shape of liner
- Liner material
- Stand-off distance
- Rate of spin
Chemical Energy - Plate Charges
HEAT versus Plate Charge (EFP / SFF / Miznay Schardin) o Manufacture Tolerances o Greater Stand Off o Rate of Spin o Penetration o Lethality
Behind Armour Effects
BAE contribute to lethality of attack
Effects may be physical, psychological or physiological
What are BAE Effect types? (4)
SHOL
Spalling
Heat/fires
Overpressure
Luminescence
Methods of weapons/Delivery of shaped Charges (5)
GGMAM
- Guns
- Grenades
- Mines
- Aircraft bombs
- Missiles
Factors taken into consideration in the defeat of armour (3)
- Accuracy
- Reliability
- Lethality
Description of Kinetic Energy
In the form of a solid missile/projectile, which dissipates it’s energy on impact and requires no triggering device to control the energy release.
Description of Chemical Energy
In the form of a substance, with a considerable potential energy, relative to it’s mass, which can liberate that energy when suitably initiated. Such materials are familiar as HE and the initiation mechanism as the fuze.
General Principles of HESH?
When the rebounding tension wave meets further primary shock waves this exceeds the strength of the plate, and a large scab is detached from the rear surface
HESH Scab size in reference to its diameter?
generally 1.25 to 1.5 times its own diameter
Velocity of scab 30 - 130 metres pers sec
What is Reverse Impact Detonation (RID)?
Detonation occurs before the fuze can produce detonation of the filling,
the shock wave will be travelling in the wrong direction
Secondary Effects from HESH? (2)
Anti -personnel
Damage to sensitive equipment
Types of armour that defeat HESH (4)
Spaced armour
Skirting plates
Grooved
Reactive armour
HESH has good performance against what other targets?
- Emplacements
- Pill boxes
- Concrete Structures
Factors affecting Performance of HESH? (3)
- Calibre
- Angle of Attack
- Striking Velocity
Requirements for:
Internal Ballistics
External Ballistics (4)
Terminal Ballistics (4)
High Velocity = a wide base for the propellant to work against and a low mass to overcome
External
- Small cross sectional area
- High Mass
- High Velocity
- Aerodynamic design
TERMINAL Small cross sectional area High mass High velocity Hard material
Stabilisation Length:diameter ratios for Spin/Fin?
Length:Diameter ratio
Spin - 7:1
Fin 15:1
What does the following mean?
APCR
APCNR
APFSDS
- Armour Piercing Composite Rigid (APCR)
- Armour Piercing Composite Non Rigid (APCNR)
- Armour Piercing Fin Stabilised Discarding Sabot (APFSDS)
Parts of a APFSDS (see picture!) (5)
- Centring Band
- Slipping Driving Band
- Obturator
- Sabot
- Screw Thread
What are the two types of discarding sabots?
Petal
Pot
Developments for KE Projectiles
Move to DU
- Self sharpening
- Pyrophoric effect
Energetic propellants
Higher diameter: length ratios
Higher calibre (up to 140 mm)
Electromagnetic - hypervelocity projectilesWhat is a Shape Charge?
A charge shaped so as to concentrate its explosive force in a particular direction
Parts of a HEAT Round (6) (look at picture!)
- PIBD Fuzing
- Ballistic Cover
- Empty Space and Shape Assist
- Conical Liner
- Detonator
- Explosive
With a shaped charge the residual energy after penetration lies within what materials? (2)
- Unconsumed part of the jet
- Fragments of metal (spalling)
How do shaped charges achieve their effect?
Intense concentration of kinetic energy
What is the Secondary effect of Shaped Charges?
Anti-personnel effects from the fragmentation of the external casing
What are the FACTORS affecting the performance of shaped charges? (5)
- Cone diameter
- Shape of liner
- Liner material
- Stand-off distance
- Rate of spin
What are the ideal stand-off distances for shape charges? (2)
2 CD - little degradation
5 CD - peak performance
Spin Compensation
Slipping driving bands
Fluted liners
Spin compensated liners
Plate Charges. What are they also known as?
- Miznay-Schardin Effect
- Plate charge
- EFP
- Self forging fragment
Initiation methods of Explosives
Direct heat/flame Percussion and stabbing Electrical Shock Waves Electromagnetic Fields Laser Chemical Reaction
