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at course_ne > Test 5 - Ballistics > Flashcards

Test 5 - Ballistics Flashcards

1
Q

What are the goals of Internal Ballistics?

A
  • Launch the projectile safely (crew and weapon)
  • Consistent performance between shots
  • Achieve the highest possible muzzle velocity.
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2
Q

What is ballistics?

A
  • The scientific study of the motion of projectiles
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3
Q

Define internal Ballistics?

A

The scientific study of the operating process within the gun from the moment that the propellant is ignited until the projectile leaves the barrel

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4
Q

Define Piobert’s Law?

A
  • The burning of a solid state propellants.

- The surface of deflagration propellants will recede layer by layer in a direction normal to the surface.

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5
Q

What happens to the rate of burning of propellant if pressure is increased?

A

As pressure increases, the rate of burning increases

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6
Q

How can the round to round regularity of muzzle velocity be improved?

A

If the All Burnt point occurs while the shell is still well back in the bore

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7
Q

What are the 6 areas of distribution of energy when the gun is fired?

A
  • Projectile (translational & rotational) = 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 lost to the gun = 20%
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8
Q

What is the effect of an increase in charge weight? (4)

A
  • Pressure increases
  • ABP moves back
  • MV increases
  • Regularity in fall of shot improves.
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9
Q

For the same weight of charge, what is the effect of increasing the propellant size?

A
  • Total initial burning surface of the propellant decreases.
  • Pressure is lower at first
  • ABP moves forward in the bore
  • MV decreases
  • Regularity in fall of shot decreases.
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10
Q

What is the effect of using a multi-tubular propellant on internal ballistics?

A

Peak pressure is decreased however the projectile still receives good energy levels.

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11
Q

What is the effect on internal ballistics of using a projectile of normal weight but shorter and a larger diameter?

A

Same muzzle velocity but less pressure everywhere compared with standard shot

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12
Q

Define intermediate ballistics

A
  • The study of the TRANSITION from internal to external ballistics that occurs in the vicinity of the muzzle
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13
Q

What are 3 methods/types which can be used to suppress flash?

A
  • Conical tube
  • slotted Tube
  • bar type.
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14
Q

How do most flash suppression devices reduce flash?

A

Break up the barrel Shock, Mach disc

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15
Q

What two elements make up bottle Shock?

A

Barrel Shock and Mach Disc

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16
Q

What are 3 main ways to minimise muzzle flash?

A
  • Muzzle Devices
  • Choice of Propellant
  • Propellant Additives
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17
Q

What can you use to reduce blast in small calibre weapons?

A

Silencers

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18
Q

What are the 5 different types of flash?

A
  • Pre-flash
  • Primary Flash
  • Muzzle Glow
  • Intermediate Flash
  • Secondary Flash
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19
Q

For a projectile fired in Vacuo, what angle of projection gives you maximum range?

A

45 degrees

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20
Q

What is meant by base drag acting on a projectile in flight?

A

A turbulent, low pressure region immediately behind the base of the projectile in flight.

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21
Q

What are the four types of drag?

A
  • Skin Friction
  • Pressure/Base Drag
  • Forebody Drag (shock waves)
  • Excrescence Drag
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22
Q

What two methods reduce base drag?

A
  • Boattailing

- Base Bleed

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23
Q

What is meant by ballistic Co-efficient?

A

A scientific measure of a projectile’s carrying ability.

24
Q

What are two major aerodynamic forces acting on the projectile, depending on Yaw?

A
  • Crosswind

- Drag

25
Q

What are the two common means of Stabilisation?

A
  • Spin stabilisation

- Fin Stabilisaiton

26
Q

Define Trajectory

A

The path taken by the centre of Gravity of a projectile

27
Q

Name two effects of muzzle gas on a projectile.

A

Slight acceleration and Yaw

28
Q

What does Cd (Drag coefficient) comprise of?

A
  • Skin Friction

- Form Drag

29
Q

4 Properties of the Projectile:

A
  • Mass
  • Calibre
  • Nose Shape
  • Spin Rate
30
Q

Define External Ballistics?

A

Transition from intermediate to terminal ballistics

31
Q

Define External Ballistics?

A

Transition from intermediate to terminal ballistics

32
Q

4 Phases of Internal Ballistics:

A

1 - Charge Ignition
2 - Combustion prior to proj motion
3 - Combustion up to the all burnt point
4 - Gas flow and proj motion after all burnt point to muzzle.

33
Q

7 Effects of Variation to Internal Ballistics

A 
B - Bore Area
I - Ignition Temperature
C - Charge Weight
C - Chamber Capacity
S - Shot Start
P - Propellant Size
M - Multiple Variations
34
Q

What are the 4 Ballistic Abnormalities?

A

B - Ballistic Hump
O - Occasion-to-occasion Effect
O - Order of Fire
C - Cold Gun Effect

35
Q

Why does Fallback occur? (4)

A
  • Mis-Match
  • Dirt or fouling
  • Insufficient Ramming force
  • Misaligned Projectile
36
Q

What are the consequences of Fallback? (4)

A
  • Round falls well short
  • Round breaks up on exit
  • In bore detonation
  • Blackened round
37
Q

Explain the Firing Sequence? (11)

A
  • 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
38
Q

What are the Burning Rate characteristics and sub categories

A
  • Propellant Composition
    • Burning Rate
    • Pressure Index
    • Force Constant
    • Co Volume
  • Propellant Granule
    • The Ballistic Size
    • The Form Function
39
Q

How can you reduce forebody drag?

A
  • Sub-sonically, forebody drag can be significantly reduced by any suitable smooth nose shape.
  • Avoid Sharp edges
40
Q

What is Yaw/Angle of Attack?

A

the angle between the axis of the longitudinal projectile and that of the velocity vector/trajectory

41
Q

12 Common terms in Internal Ballistics:

A
  • All Burnt Point (propellant has been consumed)
  • Peak Pressure (MPa) (max pressure reached)
  • Shot Start (projectile begins to move)
  • Shot exit (projectile exits the muzzle)
  • Ignition Temp (C) (temp required to ignite propellant)
  • Explosion Heat (Qex) (amount of heat liberated in the combustion of 1kg of propellant)
  • Flame Temp (C) (peak chamber temp upon combustion of propellant)
  • Chamber Press (MPa) (Pressure at the case mouth)
  • Specific gas vol (L/kg) (gas produced from 1kg propellant)
  • Muzzle Press (MPa) (peak pressure at the muzzle upon breakage of the projectile-bore seal)
  • Solid Residues (%) (w/w% of solid matter remaining after combustion)
  • muzzle velocity (m/s) (proj speed at exit from barrel)
42
Q

In cartridge cased ammunition, the primer must:

A
  • Provide rearward obturation to pressure loss (primer leakage)
  • Withstand initiation forces (pierced primer)
43
Q

What do variations in Shot Start Pressure result in an increase in?

A
  • Peak pressures are greater when a greater shot start pressure is required.
  • Burn Rate
  • Temperature
  • All burnt point moves rearward
  • Increase in MV
    (Eg squeeze bore)
44
Q

Explain Order of Fire Abnormality?

A
  • Multi charge gun systems
    • Barrel temperature deviation
      • High Charges followed by low charges
      • MV several m/s less
    • Period of inactivity
      • First round on a low charge
        • Series average MV several m/s less
      • High charge followed by low charge
        • Low charge should be unaffected.
45
Q

Explain Occasion-to-Occasion Effect?

A
  • All guns experience MV variation
  • Day-to-day variation currently unpredictable
    • Up to 5m/s
  • Lot-to-lot change of charge/proj
    • May enhance or diminish effect
46
Q

Explain the “Cold Gun” Effect?

A
  • AKA ‘Warmer Effect’
  • Initial round has greater range
  • Can occur between fire missions
    • As low as several minutes of cooling.
  • Once warmed, can achieve greater consistency
47
Q

Explain Ballistic Hump Abnormality?

A
  • MV of a new barrel rises rapidly
  • Continues over a number of rounds
  • Peaks at point undetermined
  • Returns to MV comparable with state of wear
48
Q

2 Phases of Gas flow field?

A
  • Precursor: proceeds the projectile exit from muzzle

- Main Blast field: follows as high pressure prop gases ejected into air

49
Q

Parts of the Precursor Field?

A
  • Blast Shock
  • Bottle Shock
    • Barrel Shock
    • Mach Disc
50
Q

What are the three main reasons we use muzzle devices for?

A
  • Reduce recoil
  • Suppress flash
  • Decrease report
51
Q

What are the three ways in which a silencer reduces blast?

A
  • Blast Absorption
  • Blast Dissipation
  • Blast containment and controlled release
52
Q

Parts/components of Projectile?

A

Picture:

  • Forebody
    • Ogive
  • Midbody
    • Cannelure
    • CG and CP (static Margin)
  • Afterbody
    • Base
    • Boattail
53
Q

Explain Skin Friction?

A

The air closest to the projectile is dragged with it the further you move away from the projectile the air starts to move in the opposite direction

54
Q

Explain Excrescence Drag?

A
  • Resistance that arises from protuberances from the shell

- Normally only the driving band is unavoidable and this must be carefully designed

55
Q

2 Parts that make up Drift?

A
  • Drift due to equilibrium yaw - for spun projectiles

- Drift due to rotation of the earth

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