FDK Ammo Basic
4.2 High and Low Explosives
4.2 High and Low Explosives
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Kategorie | Englisch |
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Erstellt / Aktualisiert | 20.04.2015 / 07.04.2017 |
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The 3 basic types of chemical explosive reactions:
- Burning/Combustion (Warmth, Light, Smoke; slow to fast 1m/s)
Deflagration (Heat, Flash, Smoke, Pressure; Subsonic velocity 100m/s)
- A fuel rich explosion that produces intense heat in form of a fast moving fireball with explosive force;
- It does not produce a shock wave.The main effects are caused by the fumes and overpressure.
Detonation (Heat, Flash, Smoke, Pressure, Shock Wave; Supersonic velocity 1000m/s)
- The propagation of a self-sustaining shock wave , which moves through explosive material at a velocity greater than the speed of sound.
The Difference between HighExplosives and Low Explosives
Not connected to its chemical structure, but describes the physical characteristics of the material during its intended chemical reaction: its related to the Velocity of Detonation (VD)
High Explosives
- capable of detonating when properly initiated;
- Even when improperly initiated, high explosives can undergo a Deflagration to Detonation Transition DDT
Low Explosives
- does not detonate;
- slower than the speed of sound;
- may burn;
- explode when defined
- generally associated with propellants
The difference between Primary and Secondary High Explosives:
Primary High Explosives
Only Explosives which decompose rapidly by low thermal or mechanical energy and can cause secondary explosives to detonate.
- Very sensitive
- less poerful than seconary explosives
- first chemical element of the explosive train
- easily initiated by heat, shock friction ESD
- Lead Azide most common primary explosive in military fuzing and TATP
Secondary High Explosives
- much more safe to handle
- Often used as active/main Charges for projectiles, bombs and mines
- Relatively insensitive, lower impact and friction sensitivity, need more activation energy
- Have much higher energy content and work capacity
- Depense of the amount of energy, if it will combust, deflagrate or detonate
The most common Main Charge/Secondary Explosives:
Picric Acid / Trinitrophenol (7350 m/s)
- Yellow cristals, very toxic
- Main danger comes from acidity (picric acid rects with metals and forms exremely sensitive picrate salts
TNT / Trinitrotoluol / Trotyl (6900 m/s)
- oldest and most used explosive worldwide
- pretty insensitive to shock and friction, very good stability
- starts to melt above 80°C
Tetryl / Trinitrophenymethylnitramine (7850 m/s)
- yellow
- significantly more power than TNT, but also significantly more sensitive
- most used as booster charge
PETN / Penta / Nitropenta (8400 m/s)
- TNT equivalent of 1.7
- most sensitive secondary explosive in use - used in det cord
- in mixed form with plastic, it becomes mouldable (Plastit)
RDX / Hexogen (8750 m/s)
- highest VD available for military use
- often mixed, then less sensitive
- HEAT warheads and shaped charge liner
HMX / Octogen (High Velocity Military Explosive 9100 m/s)
- often mixed with TNT = OCTOL
- RUS = OKFOL (5% wax)
A detonation can be initiated by two different processes:
Deflagration to Detonation Transition (DDT)
- is starting the chemical reaction because of an external energy source (spark, flamemechanical influence)
- The increasing gas pressure accelerate the combustion velocity - deflagration - pressure waves
- if pressure waves still rises - velocity of the waves will reach speed of sound - shockwave with stable detonation velocity
Shock to Detonation Transition (SDT)
- induced by an intense external shock wave
- intense mechanical inpact = punctual exeedance of the specific impact sensitivity
(penetration by a high velocity projectile) - Detonation of an adjoining explosive charge = direct contact shock wave propagation
(blasting cap..) - Detonation of an explosive charge nearby = across-gap shock wave propagation
(ammunition storage facility)
Sympathetic Detonation ist the transition of the detonation impulse from one charge to another
The Difference between High Order and Low Order Reaction:
High Order
- Filler functions as designed, producing a full detonation with maximm potential and shockwave
- Frags with razor sharp edges
Low Order
- With inadequate initiation, the filler does not reach its maximum energetic potential, resultin in a full or partial deflagration
- Frags with dull edges