Why does an artillery shell rotate when fired?

In summary, when an artillery shell is fired at a 45 degree angle, it will rise to a maximum height and then fall back to earth while rotating considerably to strike the ground with the nose forward. This rotation is caused by the shape of the shell and the forces of air resistance and longitudinal spin. Rifling grooves are used to prevent tumbling of bullets or shells, while the lack of rifling in mortars does not affect their ability to hit nose first.
  • #1
Frank Peters
28
2
An artillery shell is fired at, let's say, a 45 degree angle. The shell will rise to a maximun height and then fall back to earth, but the shell will also rotate considerably so that it strikes the ground with the nose forward.

What accounts for the rotation? It would seem that the center of gravity would tend to orient the shell somewhat vertically even with the aerodynamic forces acting on the body. Also, the shell is spinning about its longitudinal axis and this would prevent any rotation.
 
Physics news on Phys.org
  • #2
Frank Peters said:
An artillery shell is fired at, let's say, a 45 degree angle. The shell will rise to a maximun height and then fall back to earth, but the shell will also rotate considerably so that it strikes the ground with the nose forward.

What accounts for the rotation? It would seem that the center of gravity would tend to orient the shell somewhat vertically even with the aerodynamic forces acting on the body. Also, the shell is spinning about its longitudinal axis and this would prevent any rotation.
The rotation you're asking about (not the rotation about the longitudinal axis of the projectile) is due to the shape of the shell, being pointed on the forward end. The natural tendency of the shell would be to maintain the same angle with respect to the horizontal, but as the shell rises, its center of mass follows a roughly parabolic arc, so I would imagine that air resistance plus its longitudinal spin force the shell to be oriented tangent to the curve it's following.
One way to think about this is with the elevators on an airplane's rear wing. If both elevators are in the lowered position, the plane's nose drops. I think something like this happens as the shell starts to drop. The rear of the shell is hanging down, relative to motion through the air, which exerts an upward force on the rear of the shell, and causing the front of the shell to drop.
 
Last edited:
  • #3
It is drag from aerodynamic forces. A spherical cannonball will behave differently.

Somettimes bullets or artillery shells tumble through the air. Trying to prevent that is the purpose of the spin put on be rifling grooves.
 
  • Like
Likes sophiecentaur
  • #4
See "tractability."
 
  • #5
anorlunda said:
It is drag from aerodynamic forces. A spherical cannonball will behave differently.

Somettimes bullets or artillery shells tumble through the air. Trying to prevent that is the purpose of the spin put on be rifling grooves.
Most mortars are not rifled, but still hit nose first, the rifling makes a difference in range - at least for the US 120mm mortar. The only bullets I know that tumble are ones that strike something first (this was common with the 5.56 M16 round. If it hit a twig it would tumble.
 

Related to Why does an artillery shell rotate when fired?

1. What is artillery shell rotation?

Artillery shell rotation refers to the spinning motion of an artillery shell as it travels through the air. This rotation is caused by rifling within the barrel of the artillery gun, which imparts a spin on the shell as it is fired.

2. Why is rotation important for artillery shells?

Rotation is important for artillery shells because it helps to stabilize the shell in flight. This makes it more accurate and allows it to travel further distances with greater precision.

3. How does rotation affect the trajectory of an artillery shell?

Rotation affects the trajectory of an artillery shell by providing a gyroscopic effect, which helps to counteract the forces of drag and gravity. This results in a more predictable and consistent path for the shell to travel.

4. Can the rotation of an artillery shell be controlled?

Yes, the rotation of an artillery shell can be controlled through the use of different rifling techniques and barrel lengths. Additionally, modern artillery systems may have technology that allows for adjustable spin rates on the shells.

5. What happens if an artillery shell does not rotate?

If an artillery shell does not rotate, it will be much less accurate and have a shorter range. The lack of rotation can also cause the shell to tumble in flight, which can greatly reduce its effectiveness upon impact.

Similar threads

Replies
15
Views
2K
  • Aerospace Engineering
2
Replies
35
Views
4K
Replies
3
Views
975
  • Special and General Relativity
Replies
14
Views
2K
  • Mechanics
Replies
20
Views
2K
Replies
23
Views
1K
  • Classical Physics
Replies
10
Views
1K
  • Mechanics
Replies
9
Views
6K
Replies
18
Views
2K
Replies
4
Views
2K
Back
Top