Explosions - Detonation

Question 1

What is the difference between high explosives and low explosives?

Answer 1

• High explosives detonate in their designed use
• Low explosives deflagrate in their designed use

The method of initiation gives the desired effect.

Question 2

How are explosives classified?

Answer 2

Primary explosive: Sensitive to initiation

Secondary Explosive: Insensitive to initiation

Propellant: to create moment (propel)

Pyrotechnic: to create a special effect (light, heat, colour)

Question 3

What is the Burn Rate Equation?

Answer 3

r (burn rate) = beta x P^alpha

r = burn rate

beta = burn rate coefficient (constant)

P = pressure

alpha = pressure index.

Question 4

How is the velocity of a bomb increased?

Answer 4

Bulk explosive (propellant) = 5 mm/s

Increased surface area (gunpowder) 500 mm/s

Confining the explosive (flashpowder) = 50,000 mm/s

Question 5

What is detonation?

Answer 5

Detonation is a process of supersonic combustion in which a shock-wave is propagated forward due to energy release in a reaction zone behind it.

Question 6

What dictates the velocity of detonation, D?

Answer 6

D = velocity of detonation

n = number of gaseous products from 1 gram of explosive

Td = temperature of detonation

Delta = charge density

nTd depends on explosive under consideration, but the same explosive at different charge densities will have different D values.

Question 7

What equation defines the pressure of detonation?

Answer 7

p = 2.5 * delta * D² x10^-6

Where:

p = detonation pressure (kbar)

Delta = charge density (gcm^-3)

D = detonation velocity (ms^-1)

Question 8

What is the critical diameter?

Answer 8

Critical diameter: The minimum diameter of an explosive charge at which stable detonation can still take place.

• As the charge diameter gets smaller, the degree of confinement has a greater effect.
• The greater the confinement, the higher the velocity of detonation.