Sci am special online issue 2002.no01 - the science of war - weapons

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    ScientificAmerican.comspecial online issue no. 1THE SCIENCE OF WARWEAPONS

    The art of war, according to Sun Tzu's 2,000-year-old text of the same name, is largely amatter of strategy, but the science of war begins squarely with weapons. Physics andengineeringand more often today, chemistry and biologydrive the creation of newmilitary tools, from smart bombs and stealth aircraft to nerve gases and plastic explo-sives. Thus it is with a collection of articles about weapons that we are launching online aspecial anthology of Scientific American's recent coverage on war.

    In this issue, scientists share their expertise on one terror of the ancient battlefield, thetrebuchet, as well as several modern-day scourges, including land mines, third world sub-marines and biological arms. Additional articles feature in-depth research by staff editorson more futuristic threatsin the form of swift subsea systems and so-called non-lethalweapons. The complete table of contents appears below.

    ANCIENT WEAPONS The TrebuchetBY PAUL E. CHEVEDDEN, LES EIGENBROD, VERNARD FOLEY AND WERNER SOEDEL; SCIENTIFIC AMERICAN, JULY 1995Recent reconstructions and computer simulations reveal the operating principles of the most powerful weapon of its time.

    BLACK MARKET WEAPONS Third World SubmarinesBY DANIEL J. REVELLE AND LARA LUMPE; SCIENTIFIC AMERICAN, AUGUST 1994The proliferation of submarines may be a threat to established navies and regional stability, but to arms manufacturers it is a market opportunity.

    HIDDEN WEAPONS The Horror of Land MinesBY GINO STRADA; SCIENTIFIC AMERICAN, MAY 1996Land mines kill or maim more than 15,000 people each year. Most victims are innocent civilians. Many are children. Still, mines are planted by the thousands every day.

    BIOLOGICAL WEAPONS The Specter of Biological WeaponsBY LEONARD A. COLE; SCIENTIFIC AMERICAN, DECEMBER 1996States and terrorists alike have shown a growing interest in germ warfare. More stringent arms-control efforts are needed to discourage attacks.

    NON-LETHAL WEAPONS Fighting Future WarsBY GARY STIX; SCIENTIFIC AMERICAN, DECEMBER 1995U.S. military planners hope to rely on improved versions of the technologies tested in the Gulf War to help fight the next Saddam Hussein. They may be preparing for the wrong conflict.

    SWIFT SUBSEA WEAPONS Warp Drive UnderwaterBY STEVEN ASHLEY; SCIENTIFIC AMERICAN, MAY 2001Traveling inside drag-cutting bubbles, secret torpedoes and other subsea naval systems can move hundreds of miles per hour.

    1 SCIENTIFIC AMERICAN SPECIAL ONLINE ISSUE FEBRUARY 2002Copyright 2002 Scientific American, Inc.

  • Centuries before the development ofeffective cannons, huge artillerypieces were demolishing castle wallswith projectiles the weight of an uprightpiano. The trebuchet, invented in Chinabetween the fifth and third centuriesB.C.E., reached the Mediterranean bythe sixth century C.E. It displaced otherforms of artillery and held its own untilwell after the coming of gunpowder.The trebuchet was instrumental in therapid expansion of both the Islamic andthe Mongol empires. It also played apart in the transmission of the BlackDeath, the epidemic of plague thatswept Eurasia and North Africa duringthe 14th century. Along the way itseems to have influenced both the devel-opment of clockwork and theoreticalanalyses of motion.

    The trebuchet succeeded the catapult,which in turn was a mechanization ofthe bow [see Ancient Catapults, byWerner Soedel and Vernard Foley; SCI-ENTIFIC AMERICAN, March 1979].Catapults drew their energy from theelastic deformation of twisted ropes orsinews, whereas trebuchets relied ongravity or direct human power, whichproved vastly more effective.

    Recovering Lost Knowledge

    The average catapult launched a mis-sile weighing between 13 and 18kilograms, and the most commonlyused heavy catapults had a capacity of27 kilograms. According to Philo of By-zantium, however, even these machinescould not inflict much damage on wallsat a distance of 160 meters. The mostpowerful trebuchets, in contrast, couldlaunch missiles weighing a ton or more.Furthermore, their maximum range

    could exceed that of ancient artillery.We have only recently begun to re-

    construct the history and operatingprinciples of the trebuchet. Scholars asyet have made no comprehensive effortto examine all the available evidence. Inparticular, Islamic technical literaturehas been neglected. The most importantsurviving technical treatise on these ma-chines is Kitab aniq fi al-manajaniq (AnElegant Book on Trebuchets), written in1462 C.E. by Yusuf ibn Urunbugha al-Zaradkash. One of the most profuselyillustrated Arabic manuscripts ever pro-duced, it provides detailed constructionand operating information. These writ-ings are particularly significant becausethey offer a unique insight into the ap-plied mechanics of premodern societies.

    We have made scale models and com-puter simulations that have taught us agreat deal about the trebuchets opera-tion. As a result, we believe we have un-covered design principles essentially lostsince the Middle Ages. In addition, wehave found historical materials thatpush back the date of the trebuchetsspread and reveal its crucial role in me-dieval warfare.

    Historians had previously assumedthat the diffusion of trebuchets west-ward from China occurred too late toaffect the initial phase of the Islamicconquests, from 624 to 656. Recentwork by one of us (Chevedden), how-ever, shows that trebuchets reached theeastern Mediterranean by the late 500s,were known in Arabia and were usedwith great effect by Islamic armies. Thetechnological sophistication for whichIslam later became known was alreadymanifest.

    The Mongol conquests, the largest inhuman history, also owed something to

    this weapon. As a cavalry nation, theMongols employed Chinese and Mus-lim engineers to build and operate treb-uchets for their sieges. At the investmentof Kaffa in the Crimea in 1345 46, the trebuchets contribution to bio-logical warfare had perhaps its mostdevastating impact. As Mongol forcesbesieged this Genoese outpost on theCrimean peninsula, the Black Deathswept through their ranks. Diseasedcorpses were then hurled into the city,and from Kaffa the Black Death spreadto the Mediterranean ports of Europevia Genoese merchants.

    The trebuchet came to shape defen-sive as well as offensive tactics. Engi-neers thickened walls to withstand thenew artillery and redesigned fortifica-tions to employ trebuchets against at-tackers. Architects working under al-Adil (11961218), Saladins brother andsuccessor, introduced a defensive systemthat used gravity-powered trebuchetsmounted on the platforms of towers toprevent enemy artillery from comingwithin effective range. These towers, de-signed primarily as artillery emplace-ments, took on enormous proportionsto accommodate the larger trebuchets,and castles were transformed fromwalled enclosures with a few small tow-ers into clusters of large towers joinedby short stretches of curtain walls. Thetowers on the citadels of Damascus,Cairo and Bosra are massive structures,as large as 30 meters square.

    Simple but Devastating

    The principle of the trebuchet wasstraightforward. The weapon con-sisted of a beam that pivoted around anaxle that divided the beam into a long

    The TrebuchetRecent reconstructions and computer simulations reveal

    the operating principles of the most powerful weapon of its time

    by Paul E. Chevedden, Les Eigenbrod, Vernard Foley and Werner Soedel


    Originally Published in theJuly 1995 Issue

    Copyright 2002 Scientific American, Inc.


    and short arm. The longer arm ter-minated in a cup or sling for hurling themissile, and the shorter one in an at-tachment for pulling ropes or a counter-weight. When the device was positionedfor launch, the short arm was aloft;when the beam was released, the longend swung upward, hurling the missilefrom the sling.

    Three major forms developed: trac-tion machines, powered by crews pull-ing on ropes; counterweight machines,activated by the fall of large masses; andhybrid forms that employed both gravi-ty and human power. When tractionmachines first appeared in the Mediter-ranean world at the end of the sixthcentury, their capabilities were so far su-perior to those of earlier artillery thatthey were said to hurl mountains andhills. The most powerful hybrid ma-chines could launch shot about three tosix times as heavy as that of the mostcommonly used large catapults. In addi-tion, they could discharge significantlymore missiles in a given time.

    Counterweight machines went muchfurther. The box for the weight mightbe the size of a peasants hut and con-tain tens of thousands of kilograms. Theprojectile on the other end of the armmight weigh between 200 and 300 kilo-grams, and a few trebuchets reportedlythrew stones weighing between 900 and1,360 kilograms. With such increasedcapability, even dead horses or bundledhumans could be flung. A modern re-construction made in England hastossed a compact car (476 kilogramswithout its engine) 80 meters using a30-ton counterweight.

    During their heyday, trebuchets re-ceived much attention from engineersindeed, the very word engineering isintimately related to them. In Latin andthe European vernaculars, a commonterm for trebuchet was engine (fromingenium, an ingenious contrivance),and those who designed, made and usedthem were called ingeniators.

    Engineers modified the early designsto increase range by extracting the mostpossible energy from the falling coun-terweight and to increase accuracy byminimizing recoil. The first