Ballistics is the science of movement, flight and the impact of shells. It is divided into several disciplines. Internal and external ballistics deal with the movement and flight of shells. The transition between these two modes is called intermediate ballistics. Terminal ballistics refers to the impact of shells, a separate category covers the degree of destruction of the target. What does internal and external ballistics study?
Guns and rockets
Cannon and rocket engines are types of heat engine, partly with the conversion of chemical energy into apropellant (kinetic energy of the projectile). Propellants differ from conventional fuels in that their combustion does not require atmospheric oxygen. To a limited extent, the production of hot gases using combustible fuel causes an increase in pressure. Pressure propels the projectile and increases the burning rate. Hot gases tend to erosion of the pistol barrel or throat of the rocket. The internal and external ballistics of small arms studies the movement, flight and influence that the projectile exerts.
When the propellant charge in the gun chamber ignites, the combustion gases are held back by the shot, so the pressure rises. The projectile begins to move when pressure on it overcomes its resistance to movement. The pressure continues to rise for a while, and then drops, and the shot accelerates to high speed. Fast combustible rocket fuel was soon exhausted, and over time the shot was thrown out of the barrel: a shot speed of up to 15 kilometers per second was reached. Hinged cannons release gas through the back of the chamber to counteract recoil forces.
A ballistic missile is a missile that is guided during a relatively short initial active phase of flight, whose trajectory is subsequently governed by the laws of classical mechanics, unlike, for example, cruise missiles, which are guided aerodynamically in flight with a working engine.
Shot trajectory
In external and internal ballistics, the trajectory is the path of the shot, subject to gravity. Under the sole influence of gravity, the trajectory is parabolic. Dragging slows down the path. Below the speed of sound, resistance is approximately proportional to the square of the speed; shot tail rationalization is effective only at these speeds. At high speeds, the conical shock wave emanates from the nose of the shot. Traction, which depends heavily on the shape of the nose, is the smallest for small point impacts. Dragging can be reduced by releasing gases from the burner to the tail.
Tail ribs can be used to stabilize shells. Rear stabilization provided by slicing causes gyroscopic oscillation in response to aerodynamic drum forces. Insufficient spin allows you to fall and prevents too much immersion of the nose when it goes along the trajectory. Shot drift occurs due to elevation, meteorological conditions and the rotation of the Earth.
Impulse response
Rockets move in response to a gas outflow pulse. The engine is designed so that the pressures generated are almost constant during combustion. Radially stabilized rockets are sensitive to crosswinds, two or more engine nozzles, tilted from the flight line, can provide stabilization of the spin. The targets are usually solid and are called thick or thin depending on whether the impact of the shot affects the underlying material.
Penetration occurs when the intensity of the impact stress exceeds the yield strength of the target; it causes plastic and brittle fracture in thin targets and a hydrodynamic material flow in thick targets. An impact may fail. Penetration completely through the target is called perforation. Improved armored traps either detonate the compressed explosive against the target or explosively focus a stream of metal on its surface.
Degree of local damage
The internal and external ballistics of the shot are mainly related to the mechanisms and medical consequences of the injury caused by bullets and explosive fragments. Upon penetration, the impulse transmitted to the surrounding tissues generates a large temporary cavity. The degree of local damage is related to the size of this transition cavity. Evidence suggests that physical injury is proportional to the velocity of the cube of the projectile, its mass and cross-sectional area. Studies on the creation of body armor are aimed at preventing the penetration of shells and minimizing injuries.
External and internal ballistics is a field of mechanics that deals with the launch, flight, behavior and effects of shells, especially bullets, unguided bombs, missiles and the like. it’s a kind of science or even the art of designing and accelerating shells to achieve the desired performance. A ballistic body is a body with an impulse that can move freely, taking into account forces such as gas pressure in the gun, using rifling in the barrel, using gravity or by aerodynamic drag.
History and Background
The earliest known ballistic projectiles were sticks, stones, and spears. The oldest evidence of stone-tipped shells that can or may not be charged with a bow dates back to 64,000 years ago, which were found in Sibudu Cave, South Africa. The oldest evidence for the use of bows for shooting dates back to about 10,000 years ago.
Pine arrows were found in the Arensburg Valley north of Hamburg. They had small furrows on the underside, indicating that they were released from the onion. The oldest bow, which is still being restored, is about 8,000 years old; it was found in the Holmegard swamp in Denmark. Archery seems to have arrived in America with a tradition of arctic small tools about 4,500 years ago. The first devices identified as tools appeared in China around 1000 AD. e., and by the 12th century, technology had spread throughout Asia and Europe by the 13th century.
After a millennium of empirical development, the discipline of ballistics, external and internal, was originally studied and developed by the Italian mathematician Niccolo Tartaglia in 1531. Galileo established the principle of compound movement in 1638. General information from external and internal ballistics was put on a solid scientific and mathematical basis by Isaac Newton with the publication of Philosophia Naturalis Principia Mathematica in 1687. This gave the mathematical laws of motion and gravity, which for the first time made it possible to successfully predict trajectories. The word ballistics comes from Greek, which means throw.
Shells and launchers
Projectile - any object projected into space (empty or not) with the application of force. Although any object moving in space (such as a thrown ball) is a projectile, the term most often refers to ranged weapons. Mathematical equations of motion are used to analyze the trajectory of the projectile. Examples of shells include balls, arrows, bullets, artillery shells, rockets and so on.
A throw is a manual launch of a projectile. People are unusually good at throwing because of their high dexterity; this is a developed trait. Evidence of human throwing dates back to 2 million years. The throwing speed of 145 km per hour, found in many athletes, far exceeds the speed with which chimpanzees can throw objects, which is about 32 km per hour. This ability reflects the ability of the human shoulder muscles and tendons to maintain elasticity until it is needed to move the object.
Internal and external ballistics: briefly about types of weapons
One of the most ancient launchers was the usual slingshots, bow and arrows, catapult. Over time, guns, pistols, and rockets appeared. Information from internal and external ballistics includes information on various types of weapons.
- Spling is a weapon commonly used to throw blunt projectiles such as stone, clay, or a lead bullet. The slings have a small cradle (bag) in the middle of the connected two lengths of the cord. The stone is placed in the bag. The middle finger or thumb is placed through the loop at the end of one cord, and the tab at the end of the other cord is placed between the thumb and forefinger. The sling sways in an arc, and the tab is released at a certain point. This frees the projectile to fly towards the target.
- Bow and arrows. A bow is a flexible piece of material that shoots aerodynamic shells. The bowstring connects the two ends, and when it is pulled back, the ends of the stick are bent. When the string is released, the potential energy of the bent stick is converted to the speed of the arrow. Archery is an art or sport of archery.
- A catapult is a device used to launch a projectile over a long distance without the aid of explosive devices - especially various types of ancient and medieval siege engines. The catapult has been used since ancient times, as it turned out to be one of the most effective mechanisms during the war. The word "catapult" comes from Latin, which, in turn, comes from the Greek καταπέλτης, which means "throw, toss." Catapults were invented by the ancient Greeks.
- Pistol - a conventional tubular weapon or other device designed to release shells or other material. The projectile can be solid, liquid, gaseous or energetic and can be free, both with bullets and artillery shells, and with clamps, as with probes and whaling harpoons. The projection means varies according to the design, but is usually effected by the pressure of the gas created by quickly burning the propellant, or is compressed and stored by mechanical means working inside the tube with an open end in the form of a piston. Condensed gas accelerates the moving projectile along the length of the tube, giving sufficient speed to support the movement of the projectile when the gas stops at the end of the tube. Alternatively, you can use acceleration by generating an electromagnetic field, in which case you can abandon the tube and replace the guide.
- A rocket is a rocket, spaceship, plane or other vehicle that receives a blow from a rocket engine. The rocket engine exhaust is completely formed from the propellants carried in the rocket before use. Rocket engines operate by action and reaction. Rocket engines push rockets forward, simply throwing their exhaust backward very quickly. Although they are relatively ineffective for use at low speeds, rockets are relatively light and powerful, capable of generating high accelerations and achieving extremely high speeds with reasonable efficiency. Missiles are independent of the atmosphere and work perfectly in space. Chemical rockets are the most common type of high-performance rockets, and they usually create their exhaust fumes when burning rocket fuel. Chemical missiles store large amounts of energy in easily released form and can be very dangerous. However, careful design, testing, design, and use minimize risks.
Fundamentals of external and internal ballistics: main categories
Ballistics can be studied using high-speed photography or high-speed cameras. A shot photo taken with an ultra-high flash speed of the air gap helps to see the bullet without blurring the image. Ballistics often breaks down into the following four categories:
- Internal ballistics - the study of processes that initially accelerate shells.
- Transitional ballistics - the study of shells during the transition to cashless flight.
- External ballistics - studying the passage of a projectile (trajectory) in flight.
- Terminal ballistics - the study of the projectile and its consequences as it is completed
Internal ballistics is the study of motion in the form of a projectile. In guns, it covers the time from ignition of rocket fuel until the projectile comes out of the gun barrel. This is what internal ballistics studies. This is important for designers and users of all types of firearms, from rifles and pistols to high-tech artillery. Information from internal ballistics for missile shells covers the period during which the rocket engine provides traction.
Transitional ballistics, also known as intermediate ballistics, is a study of the behavior of a projectile from the moment it leaves the muzzle until the pressure behind the projectile is balanced, so it is between the concept of internal and external ballistics.
External ballistics studies the dynamics of atmospheric pressure around a bullet and is part of the science of ballistics, which deals with the behavior of a projectile without power in flight. This category is often associated with firearms and is associated with the unoccupied phase of the bullet’s free flight after it leaves the gun barrel and before it hits the target, therefore it is between the transition ballistics and terminal ballistics. However, external ballistics also applies to the free flight of rockets and other shells, such as balls, arrows, and so on.
Terminal ballistics is the study of the behavior and effects of a projectile when it reaches a target. This category is important both for small-caliber shells and for large-caliber shells (artillery firing). The study of extremely high speed impacts is still very new and is currently being applied mainly to the design of spacecraft.
Forensic Ballistics
Judicial ballistics includes an analysis of bullets and bullet impacts to determine information about use in court or in another part of the legal system. Apart from ballistics information, firearms and tool mark exams (“ballistic fingerprints”) examine evidence of firearms, ammunition and tools to determine if any firearms or tools were used in the commission of the crime.
Astrodynamics: Orbital Mechanics
Astrodynamics - the use of ballistics of weapons, external and internal, and orbital mechanics to the practical problems of the movement of rockets and other spacecraft. The movement of these objects, as a rule, is calculated from the laws of Newton's motion and the law of universal gravitation. This is the main discipline in the field of design and control of a space mission.
In-flight projectile travel
The basics of external and internal ballistics relate to the flight of a projectile in flight. A bullet’s flight path includes: moving down the barrel, air travel, and air travel. The basics of internal ballistics (or the original, inside the gun) vary according to the type of weapon. Bullets fired from a rifle will have more energy than similar bullets fired from a pistol. Even more powder can also be used in gun cartridges because bullet chambers can be designed to withstand more pressure.
Higher pressures require a larger gun with higher recoil, which loads more slowly and generates more heat, which leads to more metal wear. In practice, it is difficult to measure the forces inside the gun’s barrel, but one easily measurable parameter is the speed at which the bullet exits the barrel (initial velocity). The regulated expansion of gases from the burning powder creates pressure (force / area). Here is the base of the bullet (equivalent to the diameter of the barrel) and is constant. Therefore, the energy transferred to the pool (with a given mass) will depend on the mass time multiplied by the time interval over which the force is applied.
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From gun to target
External ballistics can briefly be called a journey from a cannon to a target. Bullets usually do not follow in a straight line to the target. Rotational forces act that keep the bullet from the straight axis of flight. The basics of external ballistics include such a thing as precession, which refers to the rotation of a bullet around a center of mass. Nutation is a small circular motion at the tip of a bullet. Acceleration and precession decrease as the distance from the bullet from the barrel increases.
One of the tasks of external ballistics is to create the perfect bullet. To reduce air resistance, an ideal bullet would be a long heavy needle, but such a projectile would go right through the target without dispersing most of its energy. Spheres will lag behind and release more energy, but may not even hit the target. A good aerodynamic compromise form of a bullet is a parabolic curve with a low frontal region and a branching shape.
The best bullet composition is lead, which is high in density and cheap to produce. Its disadvantages are the tendency to soften at a speed of> 1000 frames per second, which leads to the fact that it lubricates the barrel and reduces accuracy, and lead tends to completely melt. Doping lead (Pb) with a small amount of antimony (Sb) helps, but the real answer is to link the lead bullet to a hard steel barrel through another metal, soft enough to seal the bullet in the barrel, but with a high melting point. Copper (Cu) is best suited for this material as a “jacket” for lead.
Ballistics of the terminals (hit the target)
A short, high-speed bullet begins to growl sharply, turn and even spin when entering tissue. This leads to the fact that more tissue is displaced, resistance increases and gives most of the kinetic energy of the target. A longer, heavier bullet may have more energy over a wider range when it hits the target, but it can penetrate so well that it leaves the target with most of its energy. Even a low kinetics bullet can cause significant tissue damage. Bullets do tissue damage in three ways:
- Destruction and crushing. The diameter of damage during crushing in tissue is the diameter of a bullet or fragment, up to the length of the axis.
- Cavitation - a “permanent” cavity is caused by the trajectory (path) of the bullet itself with crushing tissue, while the “temporary” cavity is formed by radial stretching around the bullet path from the continuous acceleration of the medium (air or tissue) as a result of the bullet, causing the wound cavity to stretch outward. For shells moving at low speed, the permanent and temporary cavities are almost the same, but at high speed and with bullet yaw the temporary cavity becomes larger.
- Shock waves. Shock waves compress the medium and move in front of the bullet, as well as on the sides, but these waves last only a few microseconds and do not cause deep damage at low speed. At high speeds, the generated shock waves can reach up to 200 atmospheres of pressure. However, a bone fracture due to cavitation is an extremely rare event. A ballistic pressure wave from a long-range bullet strike can cause a person to shake, which causes acute neurological symptoms.
Experimental methods to demonstrate tissue damage used materials with characteristics similar to soft tissues and human skin.
Bullet design
Bullet design is important in injury potential. The Hague Convention of 1899 (and subsequently the Geneva Convention) prohibited the use of expanding, deformable bullets in wartime. Therefore, military bullets have metallic vestments around a lead core. Of course, the contract was less related to compliance than the fact that modern military assault rifles fire shells at high speed, and the bullets must be covered with a copper shell, since lead begins to melt due to heat generated at a speed of> 2000 frames per give me a sec.
The external and internal ballistics of the PM (Makarov pistol) are different from the ballistics of the so-called “destructible” bullets intended for destruction upon impact on a hard surface. Such bullets are usually made of metal other than lead, such as copper powder, compacted in the form of a bullet. The distance of the target from the muzzle plays a large role in the ability to be wounded, since most bullets fired from pistols lost significant kinetic energy (FE) at a distance of 100 yards, while high-speed military guns still have significant FE even at 500 yards. Thus, the external and internal ballistics of the PM and military and hunting rifles designed to deliver bullets with a large number of FEs over a greater distance will differ.
Designing a bullet to efficiently transfer energy to a specific target is not straightforward, since the goals are different. The concept of internal and external ballistics also includes the design of the projectile. To penetrate the thick skin and stiff bone of an elephant, the bullet must be small in diameter and strong enough to withstand disintegration. However, such a bullet penetrates most fabrics like a spear, causing a little more damage than a knife wound. A bullet designed to damage human tissues will require certain “brakes” so that the entire CE is transmitted to the target.
It's easier to design features that help slow down a large, slow moving bullet in tissues than a small, high-speed bullet. Such measures include shape modifications, such as round, flattened, or domed. Round nasal bullets provide the least inhibition, are usually sheathed and are useful mainly in low speed pistols. The flattened design provides the greatest braking only on the form, is not covered by the shell and is used in pistols at low speed (often for targeted practice). The dome design is intermediate between a circular and a cutting tool and is useful at medium speed.
The design of the bullet of hollow points facilitates the rotation of the bullet “inside out” and the alignment of the front, called “expansion”. Expansion reliably occurs only at speeds exceeding 1200 frames per second, therefore it is suitable only for pistols with maximum speed. Destructible bullet, consisting of a powder, is intended for disintegration upon impact, delivery of the entire FE, but without significant penetration, the size of the fragments should decrease as the speed of impact increases.
Potential injury
The type of tissue affects the potential for injury, as well as the depth of penetration. Specific gravity (density) and elasticity are the main tissue factors. The higher the specific gravity, the greater the damage. The greater the elasticity, the less damage. Thus, light tissue with low density and high elasticity is damaged less muscle with higher density, but with some elasticity.
The liver, spleen and brain do not have elasticity and are easily injured, as well as adipose tissue. Fluid-filled organs (bladder, heart, large vessels, intestines) can burst due to pressure waves. A bullet that infects a bone can lead to fragmentation of the bone and / or to the formation of numerous secondary missiles, each of which causes additional injury.
Pistol ballistics
These weapons are easy to hide, but hard to aim accurately, especially in crime scenes. Most small arms firing takes place at a distance of less than 7 yards, but even so, most bullets miss the intended target (only 11% of the attackers' bullets and 25% of the bullets fired by the police hit the target in one study). Typically, low-caliber weapons are used in crime because they are cheaper and easier to carry and easier to control during shooting.
Destruction of tissues can be increased by any caliber using a bullet with expanding hollow points. The two main variables in gun ballistics are the diameter of the bullet and the amount of gunpowder in the cartridge case. Older cartridges were limited by the pressures they could withstand, but advances in metallurgy doubled and triple the maximum pressure so that more kinetic energy can be generated.