Catapult
A catapult is a mechanical device that uses torsion to launch projectiles at high speeds. Historically, catapults served as crucial siege weapons in ancient and medieval warfare, designed to breach fortified cities by hurling large stones or other projectiles over walls or at enemy troops. Unlike other siege engines such as ballistae and trebuchets, catapults are categorized as indirect-fire weapons, meaning they launch projectiles in an arc rather than directly at a target. The Roman onager is one of the earliest examples of a recognizable catapult, featuring a spoon-like arm used to fling rocks.
Over time, catapults evolved to include various enhancements, like winches for easier loading and triggers for safer operation. In addition to warfare, modern applications of catapults include recreational uses, such as slingshots for target practice, as well as sophisticated systems on aircraft carriers that launch jets using torsion power, allowing efficient use of space and resources. Today, the term "catapult" encompasses a wide range of devices that utilize similar principles of mechanics to propel objects swiftly.
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Catapult
The catapult is a simple engine that uses torsion to greatly accelerate an object. In ancient times, catapults were used as siege weapons to throw large rocks at city walls, breaking them and allowing soldiers to enter a city. They could also be used to throw rocks at tightly packed masses of soldiers. They were distinctly different from the two other common types of ancient siege engines, the ballista and the trebuchet.
Modern catapults are used for a variety of other purposes. Some small catapults, such as slingshots, are used recreationally for target practice. Other catapults, such as the large, steam-powered accelerators found on aircraft carriers, are used to quickly accelerate airplanes to flight speed.
Background
During ancient and medieval warfare, armies often attempted to avoid direct conflict. When two armies met in an open battle, the casualties were enormous. Additionally, equipping and paying soldiers for repeated large, open battles was prohibitively expensive. Instead, commanders often engaged in siege warfare. During siege warfare, one side attacked a city or other fortified position, while the other side defended it. If the attackers managed to break into the fortified position, the battle was often lost. However, if they could not, they would be unable to conquer the defending city.
Commanders attacking a city had two ways of breaking into it. The first tactic involved tunneling under the city's walls. This weakened the walls' foundation, making them likely to collapse. The other involved the use of siege engines.
Siege engines were large machines designed to assault or defend fortified positions. Some siege engines, such as the siege tower, were designed to safely transport soldiers over enemy walls. However, most launched heavy projectiles at high speeds. These can be divided into three categories: direct-fire engines, counterpoise engines, and indirect-fire engines.
Direct-fire engines were pioneered by the Romans. They are best represented by the ballista. The ballista was a siege engine that functioned like a very large crossbow. It used a rope to pull back two large, wooden arms, which created many pounds of tension. A locking mechanism held the arms in place until a long, pointed bolt could be placed into the machine. When the locking mechanism was released, the bolt was launched along a fixed track, through the air, and toward a target. During the Middle Ages, the ballista was improved into the stationary or carriage-mounted arbalete a tour. In its later days, the ballista was also modified to fire large rocks.
Counterpoise engines use either human-generated traction or a counterweight to launch projectiles. The earliest-known counterpoise engine was the pierriere. Developed in China, the pierriere was first used as an anti-infantry weapon. Because it was mobile and entirely man-powered, the pierriere was highly effective for its time. Over time, a counterweight was added, allowing the weapon to be armed and loaded with much less physical exertion. This design evolved over hundreds of years, eventually developing into the iconic trebuchet.
Overview
Indirect-fire siege weapons throw a projectile in an arc toward a large target. Because they could fling extremely large projectiles but lacked precision, indirect-fire siege engines were often used to break down large walls. Their high firing arc was also used to shoot at invading armies from behind the safety of a city's walls.
The most famous indirect-siege engine is the catapult. The earliest recognizable catapult is the Roman onager. The onager featured a long arm shaped like a spoon with a divot bored into it to hold a rock. Coiled leather straps, conditioned to stretch, attached the firing arm to a frame. Some form of tension was then used to pull the firing arm back, increasing the tension on the arm. Once a projectile was placed in the divot, the firing arm could be released, launching the projectile into the air.
Because the onager's frame was so light, the force released by freeing the firing arm lifted part of the machine into the air. Because of this flaw, the onager had to be moved back into position after it was fired. Over time, many adjustments were made to catapults. Some were outfitted with large winches, making it easier for soldiers to load the weapon. Some were given simple, rope-based triggers so that soldiers could fire the weapon while standing at a distance. This kept the soldiers safe if the weapon malfunctioned or misfired.
Some catapults were used to fire a substance called Greek fire. This flammable substance was stored in jars that could easily be launched by catapults. It produced a flame that was extremely difficult to extinguish and has been compared to modern napalm. Catapults were also affixed to the decks of ships, allowing them to fire at other ships from far away.
In some sieges, catapults were used to inspire fear in the populace of a defending city. Their firing arc allowed them to fire objects over a city's walls and into the city itself. While it would not weaken the army defending the walls, launching boulders over the walls damaged homes and other important buildings in the city. Invading armies also fired disease-carrying projectiles and Greek fire over the walls to encourage the population to surrender.
In the modern world, catapults are used for a variety of purposes. The term has come to refer to any machine that uses torsion power to fling an object at a high speed. While catapults are no longer used as siege engines, they are still used by the world's militaries. Aircraft carriers with short flight decks often used torsion-generated accelerators called catapults to launch jets off the deck of the carrier. This uses less space and resources than elongating the flight deck.
Bibliography
Bahjat, Andrew. "Catapult." University of Colorado at Boulder, 2001, http://autocww.colorado.edu/~toldy2/E64ContentFiles/MilitaryWeapons/Catapult.html. Accessed 1 Mar. 2017.
"Catapult Physics." Real World Physics Problems, 2017, http://www.real-world-physics-problems.com/catapult-physics.html. Accessed 1 Mar. 2017.
Johnson, Steve. "Modern Uses of a Catapult." Sciencing, 2017, http://sciencing.com/modern-uses-catapult-8597229.html. Accessed 1 Mar. 2017.
"Siege Warfare." University of Alaska Fairbanks, http://ffden-2.phys.uaf.edu/211.fall2000.web.projects/J%20Mann%20and%20J%20James/info.html. Accessed 1 Mar. 2017.
"Siege Weapons." Medieval Life and Times, 2017, http://www.medieval-life-and-times.info/medieval-weapons/siege-weapons.htm. Accessed 1 Mar. 2017.
"The Catapult." MedievalLifestyle, 2012, http://medievallifestyle.com/siege-engines/catapult.html. Accessed 1 Mar. 2017.
"The History of the Catapult." Kalif Publishing, 2016, http://www.stormthecastle.com/catapult/the-history-of-the-catapult.htm. Accessed 1 Mar. 2017.
Wilford, John Noble. "How Catapults Married Science, Politics, and War." TheNew York Times, 24 Feb. 2004. http://www.nytimes.com/2004/02/24/science/how-catapults-married-science-politics-and-war.html. Accessed 1 Mar. 2017.