Introduction to Ballistics Energetic Materials Research and Testing Center Mike Stanley, EMRTC Introduction to Ballistics

What is Ballistics? Ballistics is the science of launching projectiles using propellant or gunpowder Includes both interior and exterior ballistics Interior ballistics includes everything that happens inside the gun barrel Exterior ballistics includes everything that happens outside the barrel Terminal Ballistics is what happens when the projectile hits the target

When did ballistics begin? Ballistics began with the invention of the first muzzle loading cannons in the 1200’s A.D. Ever since, people have been trying to maximize the velocity, accuracy, and rate of fire for guns The first handheld guns were muzzle loading rifles and were developed in the 1400’s The first cannons and rifles were smoothbores Rifling was introduced in the late 1600’s

Interior Ballistics Propelling charge design Projectile /Sabot design Barrel design Recoil system Wear

First Propellant, Black Powder Black powder, also known as gunpowder is a mixture of potassium nitrate, sulfur, and charcoal. It originated in China around the tenth century and was used in fireworks and signals. Black powder is the oldest form of a ballistic propellant and it was used with early muzzle-type firearms. Black powder was eventually replaced by cleaner burning smokeless powder.

Early cannon projectiles

Early Smokeless Powders In 1888, Albert Nobel invented a dense smokeless powder explosive called ballistite. In 1889, Sir James Dewar and Sir Frederick Abel invented another smokeless gunpowder called cordite. Cordite was made of of nitroglycerin, guncotton, and a petroleum substance gelatinized by addition of acetone.

Modern Propellants Modern propellants are nitrocellulose based Include nitroglycerine, nitro guanidine, and nitrocellulose Also include flash suppressants, deterrent layers, and layered burning Modern propellants also are configured into many shapes and sizes from ball propellant, to solid sticks

The first large bore howitzers were used in WWI and II

Caliber The caliber of the gun is usually the diameter of the bore Most guns are maximized for length, based on the velocity of the normal weight projectiles 120 calibers

Modern Large Bore Cannon Breech Bore Shoulder Projectile Charge Primer Muzzle Chamber

How does propellant work? where BR is Burn Rate β and α are found empirically ζ (zeta) is the burn augmentation factor that accounts for energy from grain fracture and inconsistent grain burning υ is the projectile velocity

Typical cannon propellant charge Ignitor Propellant Primer

Interior Ballistics Computer Codes

Breechless guns

Davis Gun 16-inch gun: 40’ long, 16” diameter barrel Portable: 40’ long x 10’ wide trailer Firing positions from horizontal to 2° beyond vertical Launch weights up to 2000 lbs.

Hypervelocity Gun Systems Hypervelocity is defined as velocities over 2 Km/s. The guns range in length from 80 to 100 calibers which provides a relatively “soft” launch platform Accelerations up to 200,000 g’s. State-of-the-art computer codes are used to analyze the interior ballistics to optimize the propellant loads and charge configurations, and the acceleration and subsequent stress loads within the projectile itself.

EMRTC Two-Stage Light Gas Gun The two stage light gas gun is propellant driven with an 8 inch diameter pump tube and can launch small fragments and projectiles up to 150 grams in weight Helium driven Velocities up to 22,000 fps 1.5 inch bore

Projectile Dynamics

ALGOR FINITE ELEMENT ANALYSIS Dynamic Projectile and Sabot Analysis

Sabot Sabot is French for wooden shoe Sabots were used in cannons to provide a gas seal so the cannon ball would have more velocity Sabots are used when the projectile is smaller than the bore Sabots allow you to fire larger bore guns with greater chamber capacity which means more velocity

Pressure Measurements Time (sec) Pressure (psi) Impulse Test 1 Breech Pressure and Impulse 0.005 0.01 0.015 0.02 0.025 8,000 80,000 16,000 160,000 24,000 240,000 32,000 320,000 40,000 400,000 48,000 480,000 56,000 560,000 Actual Breech Pressure IBHVG2 Preliminary Breech IBHVG2 Adjusted Breech Actual Impulse IBHVG2 Impulse

Test 1 Pressure Differential Time (sec) Pressure Difference (psi) Test 1 Pressure Differential 0.005 0.01 0.015 0.02 0.025 -6,000 -4,500 -3,000 -1,500 1,500 3,000 4,500 IBHVG2 Difference Actual Difference -ΔP “Reverse Differential Pressure”

Why pressure waves are bad

Breech Failure Analysis Causes Poor conditioning of propellant Major energy contribution thereby varying pressure differential Charge loading High loading density or non-uniform loading Choked gas flow Accelerated propellant grains Inconsistent flame fronts Poor ignition Center initiated or inconsistent initiated charges cause longitudinal pressure wave to form in the chamber Grain fracture

Exterior Ballistics Flight Dynamics Pitch and Yaw Fin Stabilized Spin Stabilized Trajectory Analysis

Projectile with discarding sabot

Sabot Dynamics

Image Motion Compensation Photography (Streak)

Flash X-Ray Diagnostic tool to look at projectile “in-flight” Can see pitch and yaw along with structural stability

Doppler Radar Analysis

Terminal Ballistics Impact Dynamics Fuzing Projectile Materials Penetration Depth Cratering Obliquities Fuzing Projectile Materials Target types

Projectile Penetration