Ballistics Flashcards
What is internal ballistics?
The scientific study of the operating process within the gun from the moment that the propellant is ignited until the projectile leaves the barrel
What are the 4 phases of ballistics?
Interior
Intermediate
Exterior
Terminal
What are the 3 objectives of internal ballistics?
Launch the projectile safety
Consistent performance between shots
Achieve the highest possible muzzle velocity
What is muzzle press?
Peak over pressure at the muzzle upon breakage of the projectile bore seal
What are the 4 phases of internal ballistics?
Charge ignition
Combustion prior to projectile motion
Combustion up to the all burnt point
Gas flow and projectile motion after all burnt point to muzzle
Explain charge initiation?
- the propellant is usually initiated by either a percussion or electrical primer
- the primer releases hot gases and particles into the charge
- the hot gas flow causes the propellants surface temperature to increase
- this hot gas flow is like a blast wave through the chamber
- the gas flow also increases the pressure within the chamber
- the high temperature and pressure causes the propellant to initiate
The primer needs to ensure consistent and effective charge initiation or otherwise what will happen?
Irregular initiation will lead to misfires and variations between shots
What is primer leakage?
Pressure loss due to the primer in the cartridge case not providing obturation
The primer must what 2 things?
Provide obturation to avoid pressure loss
Withstand the initiation forces (firing pin impact), pierced primer
What does piobert’s law describe?
The surface of deflagrating propellants will recede layer by layer in a direction normal to the surface
Explain burning rate?
Is the rate at which a granule reduces in size as the burning of that granule occurs on all sides
What is pressure index?
Coefficient which relates to changes in burning rate to changes in pressure
What is burning characteristics of propellant composition?
Burning rate
Pressure index
Force constant
Co-volume
What is burning characteristics of propellant granule?
The ballistic size
The form function
What is co-volume?
The volume occupied by the molecules of a kg of propellant in a gaseous state
What is force constant?
A measure of the pressure which a unit mass of propellant produces in a fixed volume
Force constant = what?
Force constant = maximum pressure X effective volume of closed-vessel / mass of propellant
What is ballistic size?
Is the shortest distance between any two points on the surface of a propellant granule
What is form function?
How the surface area of a propellant grain of a particular shape changes during combustion
What type of propellant will effect the internal ballistic phase?
Single vs double
7 Characteristics of propellant?
Burning rate Pressure index Co volume Force constant Ballistic size Form function Single vs double
Single based propellant has a what burn which results in a what pressure for a what period?
Single
Higher
Short
Double based’s what burn results in what pressures for a what duration?
Double
Lower
Longer
(11)what is the firing sequence?
- Initiation of the primer
- Propellant combustion
- Increase in pressure & temp thereby increasing the burn rate
- Shot start
- Acceleration of the projectile
- Peak pressure
- increase in volume
- all burn point
- acceleration increases
- pressure is 1/16 of peak pressure when the projectile is at the muzzle
- entire process from initiation to muzzle exit less then 15 milliseconds
Areas of Distribution of energy when the gun is fired? (6)
Projectile-32% Residual heat of the gases-42% Recoil of the gun-0.2% Engraving the driving band/barrel friction-2.8% Unburnt charges and gases-3% Heat lose to the gun-20%
What are the effects of variations? (7)
Charge weight Propellant size Chamber capacity Ignition temperature Shot start Bore area Multiple variations
What are the four ballistic abnormalities?
Occasion to occasion effect
The warmer (cold gun) effect
Order of fire
Ballistic hump
How can the round to round regularity of muzzle velocity be improved?
If burning finishes while the shell is still well back in the bore
What is the effect of using a multi tubular propellant on internal ballistics?
The peak pressure is reduced but the projectile still gets good energy levels
What is the effect on internal ballistics of using a projectile of normal weight, but shorter and of larger diameter than normal?
The same muzzle velocity is achieved with a pressure which is everywhere less than with the standard shot
Definition of intermediate ballistics?
The study of the transition from internal to external ballistics that occurs in the vicinity of the muzzle
Two phases of gas flow field?
The precursor blast field that proceeds the projectile exit from the muzzle
The main blast field that follows as high pressure propellant gases are ejected into the air
Two parts of bottle shock?
Barrel shock-sides
Mach disc-front
2 main blast field effects?
As the propellant is travelling quicker than the projectile, it will catch up to the projectile and possibly impart a small amount of acceleration
The forces could also cause the projectile to yaw as the shock waves catch up with the projectile
5 Types of flash?
Pre flash Primary flash Muzzle glow Intermediate flash Secondary flash
3 Flash reduction methods?
Muzzle devices (flash suppressors)
Type of propellant
Propellant additives
3 reasons for muzzle devices?
Reduce recoil
Suppress flash
Decrease report - silencer
2 reasons for flash suppression?
Reduce signature
Reduces possibility of temp blindness
3 types of muzzle suppressors?
Conical tube
Slotted tube
Bar type
What does a flash suppressor do?
Breaks up the bottle to remove the heat from the secondary flash
2 flash reduction methods?
Choice of propellant-Triple based propellant
Propellant additives-potassium and sodium salts inhibit the formation and burning of hydrogen gases however do create more smoke
Muzzle devices
Two main muzzle blast sources?
Blast shock wave
Flash blast
3 types of silencers?
Blast absorption
Blast dissipation
Blast containment and controlled release
What is recoil?
Recoil is the rearward motion of the gun in reaction to the forward motion imparted by the projectile and propellant gases
2 ways to counter recoil?
Braking system
Muzzle breaks - can do 50% but causes gunner damage
- normally 25%
How many projectile lengths in intermediate?
7
How do most flash suppression devices reduce flash?
Break up the barrel shock
Mach disc
4 properties of the projectile?
Mass
Calibre
Nose shape
Spin
3 properties of the atmosphere?
Air density
Temperature
Pressure
What is trajectory?
The trajectory is the path taken by the centre of gravity of the projectile
Air resistance- 4 drag forces?
Skin friction
Pressure drag
Forebody drag
Excrescence
The atmosphere up to an altitude of 20km is basically composed of?
78% nitrogen
21% oxygen
1% comprising of water, carbon dioxide, hydrogen and other gases
Viscosity and what 3 all vary with altitude?
Pressure
Temperature
Density
