The early history of the catapult and the crossbow in Greece are closely intertwined. Primitive catapults were essentially “the product of relatively straightforward attempts to increase the range and penetrating power of missiles by strengthening the bow which propelled them” Castles and fortified walled cities were common during Medieval times - and catapults were used as a key siege weapon against them. As well as attempting to breach the walls, incendiary missiles could be thrown inside—or early biological warfare attempted with diseased carcasses or putrid garbage catapulted over the walls.
Defensive techniques in the Middle Ages progressed to a point that rendered catapults ineffective for the most part. The Viking siege of Paris (885–6 A.D.) “saw the employment by both sides of virtually every instrument of siege craft known to the classical world, including a variety of catapults,” to little effect, resulting in failure.
The most widely used catapults throughout the Middle Ages were as follows:
Ballistas were similar to giant crossbows and were designed to work through torsion. The ammunition used were basically giant arrows or darts made from wood with an iron tip. These arrows were then shot “along a flat trajectory” at a target. Ballistas are notable for their high degree of accuracy, but also their lack of firepower compared to that of a Mangonel or Trebuchet. Because of their immobility, most Ballistas were constructed on site following a siege assessment by the commanding military officer.
The springald's design is similar to that of the Ballista's, in that it was effectively a crossbow propelled by tension. The Springald's frame was more compact, allowing for use inside tighter confines, such as the inside of a castle or tower. This compromised the firepower though, making it an anti-personnel weapon at best.
These machines were designed to throw heavy projectiles from a “bowl-shaped bucket at the end of its arm”. Mangonels were mostly used for “firing various missiles at fortresses, castles, and cities,” with a range of up to 1300 feet. These missiles included anything from stones to excrement to rotting carcasses. Mangonels were relatively simple to construct, and eventually wheels were added to increase mobility.
Mangonels are also sometimes referred to as Onagers. Onager catapults initially launched projectiles from a sling, which was later changed to a “bowl-shaped bucket”. The word 'Onager' is derived from the Greek word 'onagros' for wild ass, referring to the “kicking motion and force”] that were recreated in the Mangonel's design. In terms of historical records, there's not much to go on. The most detailed account of Mangonel use is from “Eric Marsden's translation of a text written by Ammianus Marcellius in the 4th Century AD” describing its construction and combat usage.
Trebuchets were probably the most powerful catapult employed in the Middle Ages. The most commonly used ammunition were stones, but “darts and sharp wooden poles” could be substituted if necessary. The most effective kind of ammunition though involved fire, such as “firebrands, and deadly Greek Fire”. Trebuchets came in two different designs: Traction, which were powered by people, or Counterpoise, where the people were replaced with “a weight on the short end”.The most famous historical account of trebuchet use dates back to the siege of Stirling Castle in 1304, when the army of Edward I constructed a giant trebuchet known as “Warwolf”, which then proceeded to “level a section of [castle] wall, successfully concluding the siege.”
A simplified trebuchet, where the trebuchet's single counterweight is split, swinging on either side of a central support post.
Leonardo da Vinci sought to improve the efficiency and range of earlier designs. His design incorporated used a large wooden leaf spring as an accumulator to power the catapults. Both ends of the bow are connected by a rope, similar to the design of a bow and arrow. The leaf spring was not used to pull the catapult armature directly, rather the rope was wound around a drum. The catapult armature was attached to this drum which would be turned until enough potential energy was stored in the deformation of the spring. The drum would then be disengaged from the winding mechanism, and the catapult arm would snap around.Though no records exist of this design being built during Leonardo's lifetime, contemporary enthusiasts have reconstructed it. The last large scale military use of catapults was during the trench warfare of World War I. During the early stages of the war, catapults were used to throw hand grenades across no man's land into enemy trenches. (These were eventually replaced by small mortars).
Special variants called aircraft catapults are used to launch planes from land bases and sea carriers when the takeoff runway is too short for a powered takeoff or simply impractical to extend. Ships also use them to launch torpedoes and deploy bombs against submarines. Small catapults, referred to as traps, are still widely used to launch Clay targets into the air in the sport of Clay pigeon shooting.
Until recently, catapults were used by thrill-seekers to experience being catapulted through the air. The practice has been discontinued due to fatalities, when the participants failed to land onto the safety net.
Pumpkin Chunking is another widely popularized use, in which people compete to see who can launch a pumpkin the farthest by mechanical means (although the world record is held by a pneumatic air cannon).
In January 2011, popsci.com, the news blog version of Popular Science magazine reported a group of smugglers used a homemade catapult to deliver marijuana into the United States of America from Mexico. The machine was found 20 feet from the border fence with 4.4 pounds (2.0 kg) bales of marijuana ready to launch