External Ballistics

Question 1

What are the properties of the projectile?

Answer 1

• Mass
• Calibre
• Spin rate
• Nose shape

Question 2

What are the properties of the atmosphere?

Answer 2

• Air density
• Temperature
• Pressure
• Viscosity (thickness)

Question 3

What are two common means of stabilisation?

Answer 3

• Spin

- Fin

Question 4

What is trajectory?

Answer 4

-The path taken by the centre of gravity of the projectile

Question 5

What is the drag co-efficient?

Answer 5

A scientific measure of a projectile’s carrying ability

Question 6

What is the measure of carrying a projectile?

Answer 6

Co = M / (σ χ d2)

Question 7

What are the 4 drag forces, explain each?

Answer 7

Skin friction
-Each successive layer from the projectile is moving slightly slower

Base drag
-The turbulence created behind the projectile

Forebody drag
-It is the displacement of the air infront of the projectile which causes a drain on the kinetic energy of the projectile

Excrescence drag
-Drag causes by items protruding from the projectile, eg. driving band

Question 8

What are two ways to reduce base drag?

Answer 8

• Boatailing

- Base bleed

Question 9

What is the magnus effect?

Answer 9

As an object spins it will carry some air around with it which will cause it to yaw

Question 10

What are the two major aerodynamic forces acting on a projectile?

Answer 10

• Crosswind

- Drag