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Armour-piercing fin-stabilized discarding sabot
Armour-piercing fin-stabilized discarding sabot (APFSDS), long dart penetrator, or simply dart ammunition is a type of kinetic energy penetrator ammunition used to attack modern vehicle armour. As an armament for main battle tanks, it succeeds armour-piercing discarding sabot (APDS) ammunition, which is still used in small or medium caliber weapon systems.
Improvements in automotive propulsion and suspension systems after World War II allowed modern main battle tanks to incorporate progressively thicker and heavier armor without unduly sacrificing maneuverability and speed. As a result, achieving deep armour penetration with gun-fired ammunition required even longer anti-armour projectiles fired at even higher muzzle velocity than could be achieved with stubbier APDS projectiles.
Armour-piercing discarding sabot (APDS) was initially the main design of the kinetic energy (KE) penetrator. The logical progression was to make the shot longer and thinner to increase its sectional density, thus concentrating the kinetic energy in a smaller area. However, a long, thin rod is aerodynamically unstable; it tends to tumble in flight and is less accurate. Traditionally, rounds were given gyroscopic stability in flight from the rifling of the gun barrel, which imparts a spin to the round. Up to a certain limit, this is effective, but once the projectile's length is more than six or seven times its diameter, the gyroscopic effect imparted by barrel rifling becomes less effective. Adding fins to the base of the round like the fletching of an arrow instead gives the round its stability in flight.
The spin from standard rifling decreases the performance of these rounds (rifling adds friction and converts some of the linear kinetic energy to rotational kinetic energy, thus decreasing the round's velocity, range and impact energy). A very high rotation on a fin-stabilized projectile can also increase aerodynamic drag, further reducing impact velocity. For these reasons APFSDS projectiles are generally fired from smoothbore guns, a practice that has been taken up for tank guns by western and eastern blocs. Nevertheless, in the early development of APFSDS ammunition, existing rifled barrel cannons were used, (and are still in use), such as the 105 mm M68/M68E1 cannon mounted on the M60/A1/A3 main battle tank or the British 120 mm Royal Ordnance L30 of the Challenger 2 tank. To reduce the spin rate when using a rifled barrel, a "slip obturator" is incorporated that allows the high-pressure propellant gases to seal, yet not transfer the total spin rate of the rifling into the projectile. The projectile still exits the barrel with some residual spinning, but at an acceptably low rate. In addition, some spin rate is beneficial to a fin-stabilized projectile, averaging out aerodynamic imbalances and improving accuracy. Even smooth-bore fired APFSDS projectiles incorporate fins that are slightly canted to provide some spin during flight; and very-low-twist rifled barrels have also been developed to fire APFSDS ammunition.[citation needed]
KE penetrators for modern tanks are commonly 2–3 cm (0.787–1.18 in) in diameter, and can approach 80 cm (31.5 in) long. As more structurally efficient penetrator-sabot designs are developed, their length tends to increase to defeat greater line-of-sight armour depth.
The concept of armour defeat using a long rod penetrator is a practical application of the phenomenon of hydro-dynamic penetration.
Practical penetrator and target materials are not fluids before impact, but at sufficiently high impact velocity even crystalline materials begin to behave in a highly plastic fluid-like manner.
Long rod projectiles penetrate a fluid in the literal sense, based simply on the density of the target armour and the density and length of the penetrator. The penetrator will continue to displace the target to a depth of the penetrator length times the square root of the penetrator to target densities. One observes immediately that longer, denser penetrators will penetrate to deeper depths, and this forms the basis for the development of long-rod anti-armour projectiles.
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Armour-piercing fin-stabilized discarding sabot AI simulator
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Armour-piercing fin-stabilized discarding sabot
Armour-piercing fin-stabilized discarding sabot (APFSDS), long dart penetrator, or simply dart ammunition is a type of kinetic energy penetrator ammunition used to attack modern vehicle armour. As an armament for main battle tanks, it succeeds armour-piercing discarding sabot (APDS) ammunition, which is still used in small or medium caliber weapon systems.
Improvements in automotive propulsion and suspension systems after World War II allowed modern main battle tanks to incorporate progressively thicker and heavier armor without unduly sacrificing maneuverability and speed. As a result, achieving deep armour penetration with gun-fired ammunition required even longer anti-armour projectiles fired at even higher muzzle velocity than could be achieved with stubbier APDS projectiles.
Armour-piercing discarding sabot (APDS) was initially the main design of the kinetic energy (KE) penetrator. The logical progression was to make the shot longer and thinner to increase its sectional density, thus concentrating the kinetic energy in a smaller area. However, a long, thin rod is aerodynamically unstable; it tends to tumble in flight and is less accurate. Traditionally, rounds were given gyroscopic stability in flight from the rifling of the gun barrel, which imparts a spin to the round. Up to a certain limit, this is effective, but once the projectile's length is more than six or seven times its diameter, the gyroscopic effect imparted by barrel rifling becomes less effective. Adding fins to the base of the round like the fletching of an arrow instead gives the round its stability in flight.
The spin from standard rifling decreases the performance of these rounds (rifling adds friction and converts some of the linear kinetic energy to rotational kinetic energy, thus decreasing the round's velocity, range and impact energy). A very high rotation on a fin-stabilized projectile can also increase aerodynamic drag, further reducing impact velocity. For these reasons APFSDS projectiles are generally fired from smoothbore guns, a practice that has been taken up for tank guns by western and eastern blocs. Nevertheless, in the early development of APFSDS ammunition, existing rifled barrel cannons were used, (and are still in use), such as the 105 mm M68/M68E1 cannon mounted on the M60/A1/A3 main battle tank or the British 120 mm Royal Ordnance L30 of the Challenger 2 tank. To reduce the spin rate when using a rifled barrel, a "slip obturator" is incorporated that allows the high-pressure propellant gases to seal, yet not transfer the total spin rate of the rifling into the projectile. The projectile still exits the barrel with some residual spinning, but at an acceptably low rate. In addition, some spin rate is beneficial to a fin-stabilized projectile, averaging out aerodynamic imbalances and improving accuracy. Even smooth-bore fired APFSDS projectiles incorporate fins that are slightly canted to provide some spin during flight; and very-low-twist rifled barrels have also been developed to fire APFSDS ammunition.[citation needed]
KE penetrators for modern tanks are commonly 2–3 cm (0.787–1.18 in) in diameter, and can approach 80 cm (31.5 in) long. As more structurally efficient penetrator-sabot designs are developed, their length tends to increase to defeat greater line-of-sight armour depth.
The concept of armour defeat using a long rod penetrator is a practical application of the phenomenon of hydro-dynamic penetration.
Practical penetrator and target materials are not fluids before impact, but at sufficiently high impact velocity even crystalline materials begin to behave in a highly plastic fluid-like manner.
Long rod projectiles penetrate a fluid in the literal sense, based simply on the density of the target armour and the density and length of the penetrator. The penetrator will continue to displace the target to a depth of the penetrator length times the square root of the penetrator to target densities. One observes immediately that longer, denser penetrators will penetrate to deeper depths, and this forms the basis for the development of long-rod anti-armour projectiles.