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Thread: Rifling of long range projectile weapons.

  1. #1
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    Rifling of long range projectile weapons.

    I was just thinking about the rifling of long range guns and their spinning projectiles.

    Say if they are fired at 45 degrees, when they come down on anything at ground level, they should be pointing perpendicular to their flightpath, or at an even steeper angle(backwards), due to air resistance.

    Is this a problem for armies?

    I suppose if the projectile is weighted more heavily at the front, this might compensate for this?
    Formerly Frog march.

  2. #2
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    On that trajectory in a vacuum they would certainly come down sideways, which would be bad news for an armor piercing round. In air, it is my educated guess that an optimum spin speed can be used to make the projectile nose over as desired from the aerodynamic action of the air. A spiraling football does just that on a long pass. I would be interested in seeing what artillery and naval gunnery experts have to say on this.

  3. #3
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    Quote Originally Posted by WaxRubiks View Post
    I was just thinking about the rifling of long range guns and their spinning projectiles.

    Say if they are fired at 45 degrees, when they come down on anything at ground level, they should be pointing perpendicular to their flightpath, or at an even steeper angle(backwards), due to air resistance.

    Is this a problem for armies?

    I suppose if the projectile is weighted more heavily at the front, this might compensate for this?
    First the aero side forces act at different centres, further back when supersonic, so the design of the bullet is compromised. Side force away from the inertial centre cause couples and they cause gyroscopic precession eventually leading to toppling in flight. As you guessed.
    Last edited by profloater; 2019-Jan-28 at 03:39 PM. Reason: Back
    sicut vis videre esto
    When we realize that patterns don't exist in the universe, they are a template that we hold to the universe to make sense of it, it all makes a lot more sense.
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    I think what you seek is in this article about external ballistics:

    Stabilizing non-spherical projectiles during flight
    Two methods can be employed to stabilize non-spherical projectiles during flight:

    Projectiles like arrows or arrow like sabots such as the M829 Armor-Piercing, Fin-Stabilized, Discarding Sabot (APFSDS) achieve stability by forcing their center of pressure (CP) behind their center of Mass (CM) with tail surfaces. The CP behind the CM condition yields stable projectile flight, meaning the projectile will not overturn during flight through the atmosphere due to aerodynamic forces.

    Projectiles like small arms bullets and artillery shells must deal with their CP being in front of their CM, which destabilizes these projectiles during flight. To stabilize such projectiles the projectile is spun around its longitudinal (leading to trailing) axis. The spinning mass creates gyroscopic forces that keep the bullet's length axis resistant to the destabilizing overturning torque of the CP being in front of the CM.
    On the Moon, however....
    Last edited by schlaugh; 2019-Jan-28 at 04:06 PM.

  5. #5
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    Quote Originally Posted by schlaugh View Post
    On the Moon, however....
    Think Needler:
    https://assets.documentcloud.org/doc...-Mind-When.pdf

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