5. Ballistics Flashcards
(57 cards)
What is Ballistics?
The scientific study of the MOTION OF PROJECTILES
Define Internal Ballistics
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OPERATING PROCESS within the gun
from propellant ignition
until projectile leaves the barrel
Goals/Objectives of Internal Ballistics (3)
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Launch the projectile SAFELY
CONSISTENT performance between shots
Achieve the HIGHEST possible muzzle velocity
Define Piobert’s Law
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The surface of a deflagrating (burning) propellant recedes layer by layer in a direction normal to the surface.
Common Terms (cont’d)
- All burnt point
- Peak Pressure (MPa)
- Shot Start
- Shot exit
- Ignition Temp (oC)
- Explosion Heat (Q ex)
- Flame Temp (oC)
- Chamber Pressure (MPa)
- Specific Gas Volume (L/1kg)
- Muzzle Pressure (MPa)
- Solid Residues (%)
- All propellant has been burnt
- maximum pressure is reached
- The point when the shot initially moves
- Shot exits the muzzle
- Temperature required to ignite the propellant
- amount of heat liberated in the combustion of 1kg of propellant
- PEAK chamber temperature upon combustion of propellant
- Pressure at the case mouth
- Amount of gas produced 1kg propellant
- peak overpressure at the muzzle upon breakage of the projectile-bore seal
- % of solid matter remaining after combustion
4 Phases of Internal Ballistics
- Charge ignition (by the primer)
- Combustion prior to projectile motion
- Combustion up to ALL BURNT POINT
- Gas flow and projectile motion after all burnt point to muzzle
Burning Characteristics of Propellant Composition (4)
..of a propellant granule? (2)
COMPOSITION - Burning rate - Pressure index - Force Constant - Co-volume GRANULE - Ballistic size -The Form Function
Pressure Index
Co-efficient which relates to changes in burning rate to changes in pressure
(Burning increases pressure, which in turn, increases burn rate)
Co-Volume (vol/1kg)
The volume occupied by the molecules of a kilogram of propellant in a gaseous state
CV =
Force Constant
A measure of the pressure which a unit mass of propellant produces in a fixed volume
= Max pressure x effective volume of closed-vessel / Mass of propellant
Single vs Double Based Propellant
Single based propellant has a single burn which results in a higher pressure for a short
period.
Double based’s double burn results in lower pressures for a longer duration, but reaches that quicker
Firing Sequence (11)
- Initiation of the primer
- Propellant combustion
- Increase in Pressure and Temperature thereby increasing the Burn Rate
- Shot Start
- Acceleration of the projectile
- Peak pressure
- 1/10 of the Barrel length - Increase in volume
- Decrease in pressure
- All burnt point
- Acceleration increases slightly
- Pressure is 1/6 of peak pressure when the projectile is at the muzzle
- Entire process from initiation to muzzle exit takes less than 15 milliseconds
Distribution of (propellant) Energy by % (6)
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Projectile - 32% Residual Heat of the gases - 42% Recoil of the gun - 0.2% Engraving the driving band - 2.8% Unburnt charges & gases - 3% Heat lost to the gun - 20%
What are the types Effects of Variations on Propellant and explain their effect
- Charge Weight
- Propellant size
- Propellant Shape
- Chamber Capacity
- Ignition Temperature
- Shot start
- Bore Area
- Multiple Variations
What are the differences to
Peak Pressure, Temp,
Velocity, ABP,
and results due to Effects of Variations on Propellant
-Charge Weight -Propellant size -Propellant shape(standard is degressive.) Chamber Capacity -Ignition Temperature -Shot start pressure -Bore Area -Multiple Variations
-Pressure Temp Velocity ABP
+Charge Weight: more, more, increase, Sooner
- more consistency and accuracy to fall of shot
+Propellant size: less, decrease, decrease, later
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(Neutral) Propellant Shape: less, decrease, slight increase, sooner
+Chamber (gas)Capacity: less, decrease
Ignition Temperature: increased all, sooner ABP
Shot start Pressure: increased all, sooner ABP
Bore Area (short, fatter): decrease, decrease, increased Vel, late ABP
Multiple Variations:
How can the round-to-round regularity of muzzle velocity be improved?
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An all burnt point where the shell is still well back in the bore
What is Fall Back?
When does it occur (4)
Consequences(4)
Occurs when the shell fails to remain in it's 'seating' on loading 1. Mismatched driving band to forcing cone 2. Dirt or fouling 3. insufficient ramming force 4. misaligned project goal A. Round fall well short B. Round breaks up on exit C. In bore detonation D. Blackened round
Ballistic Abnormalities
Occasion-to-occasion effect
The Warmer (Cold gun effect)
Order of fire
Ballistic hump ( re: new barrel)
What happens to the rate of burning of propellant if the pressure is increased?
It increases the burn rate
Extra q for int bal.
If bung finll wek ie
re.
What are the six (6) areas of distribution of
energy when the gun is fired?
Projectile, translational and rotational Heat in the gas Gun recoil Driving band engraving and overcoming friction of the bore. Unburnt charge and gases Heat in the gun
What is the effect of an increase in charge
weight?
Pressure increases, ABP moves back, muzzle velocity
increases, regularity in fall of shot improves.
For the same weight of charge, what is the
effect of increasing the propellant size? (5)
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- Total initial burning surface of the propellant decreases,
- Pressure is lower at first,
- ABP moves forward in the bore,
- muzzle velocity decreases,
- regularity in fall of shot decreases.
What are the effects of using a multi tubular
propellant on internal ballistics?
The peak pressure is reduced but the projectile still gets good energy levels.
