July–December 2006 25

The CB Battlefield Legacy:Understanding the Potential

Problem of Clustered CB WeaponsBy Mr. Reid Kirby

The millions of pieces ofunexploded ordnance (UXO) litteringformer battlefields are a lingeringlegacy of World War I. In the Verdun,French démineurs dispose of about30 tons of chemical ordnance eachyear; they have been doing so since1945. China, too, has a chemicalbattlefield legacy, with more than 120tons of abandoned Japanesechemical weapons from World WarII. The removal of these weapons iscostly and time-consuming, requiringspecialized administrative programsthat often operate for decades.

The safety measures, includingthe temporary evacuation ofinhabitants, during removal operationsconducted at these weapons sites hasresulted in underrating the perceivedlethality potential of a contemporarychemical-biological (CB) battlefield.The chemical weapons of WorldWars I and II were composedprincipally of unexploded artilleryshells, and they contained agents thatwere less toxic than the nerve agentsof today.

The remnants of a contemporaryCB battlefield will include air- andmissile-delivered submunitions.Unlike the fragmentation and high-explosive remnants of the Kosovoand Laos conflicts, an accidentinvolving contemporary UXO mayaffect people far from the immediatevicinity of the accident. A comparisonof fragmentation and CB-clusteredweapons is important in understandingthis potential problem.

Bombs and Warheads

Aerial chemical bombs did notbecome a part of military inventoriesuntil after World War I. The pivotalyear for aerial chemical armamentswas 1928. In that year, an airpowerdemonstration conducted by the U.S.Army Air Forces started with an aerialmustard gas spray attack, and theChemical Warfare Service experi-mented with 30- and 50-pound aerialbombs. The Italian invasion ofEthiopia in 1935 involved the firstlarge-scale use of aerial chemicalweapons, followed by the Japanesein China.

While aerial spray munitions werean important development, the ArmyAir Corps was biased against usingthem during World War II. TheGermans discovered that chemicalcluster bombs were three times moreeffective than a single, massivechemical bomb. The United Statesalso made this discovery, and chemicalcluster bombs—which later includedbiological cluster bombs—were theaccepted standard for CB airarmament by the end of the war.

The first air-delivered nerve-agentweapon in the U.S. arsenal was the1,000-pound M34A1 cluster bomb(originally developed as the E101R3).The M34A1 contained 76 cylindrical,10-pound M125 (E54R6) chemicalbomblets. It had a fill efficiency (ratioof agent weight to weapon weight)of only 17 percent and was, therefore,not an optimum delivery system. It

was designed for delivery by medium-size bombers like the B-47, withbombing runs between 15,000 and35,000 feet above the target. Usingan M152E3 mechanical time fuze, theM29 cluster adapter opened at 5,000feet and was capable of saturating a170-meter-diameter target withbomblets. The weapon was added tothe U.S. chemical inventory as aninterim item for an immediatecapability, but was retained asaugmentation for a period of timefollowing the introduction of moreeffective sarin (GB) weapons.

Before the advent of ballisticmissiles, subsonic cruise missiles werean important part of the U.S. strategicand operational strike capability. TheChemical Corps developed CBwarheads for these cruise missiles,incorporating the M125 and M114bomblets into warheads for the Matador,Rascal, Snark, and Navajo.1 With theintroduction of tactical ballistic missiles,the Chemical Corps began thedevelopment of CB warheads for theMajor and Hermes; however, theseprojects were not significant.

Developmental CB warheads forthe Corporal missile and aninterchangeable warhead for theHonest John free-flight rocket markeda turning point in CB warhead design.Using variations of the M34A1 aswarheads, field trials with theCorporal and numerous trials with theHonest John quickly demonstratedproblems with traditional clustering.A Chemical Corps review of CB

Army Chemical Review26

bomblets in 1954 found that theexisting bomblets were unsuitable forcoverage requirements (areas greaterthan 900 feet in diameter), the clusteradapter was redundant, and releasesat supersonic speeds resulted inbomblet damage.

The 762-millimeter M190 HonestJohn GB warhead is an example of aCB warhead used for theater ballistic

missiles and large-caliber rockets.Developed as the E19R2, it carried356 115-millimeter M134 (E130R1)spherical bomblets.2 The overall fillefficiency of the M190 was 37percent. It had a range of 8.5 to 33.8kilometers and released its bombletsat 5,000 feet above its target using aT2075 mechanical time fuze to cut thewarhead skin and saturate a targetgreater than 1,000 meters in diameterwith bomblets. The M139 (E130R2)had replaced the M134 by the timethe warhead entered production. TheM139 had superior coverage, with aglide angle of 22 degrees fromvertical.3

Probability

The probability of neutralizing atarget with CB weapons in a givensituation (P

S) is equal to the product

of probabilities for the chain of eventsencountered by almost any weaponssystem. That is—

KRLADS PPPPPP ××××=

Where—

PD

= probability of detecting thetarget

PA

= probability of acquiring thetarget

PL

= probability of launching theCB weapon at the target

PR

= probability of the weaponreaching the target

PK

= probability of a CB casualtyeffect.4

Though generic, the importanceof the overall probability cannot beunderestimated. The equation specifiesthe steps for defeating a CB capabilityand indicates the likely success of CBemployment. The concealment of ourforces and the destruction of enemyintelligence assets lower theprobability of detection. Our counter-intelligence and mobility alter thetargeting process and lower the

probability that an enemy will be ableto acquire a target. The destructionof enemy communications networksand/or launchers lowers theprobability of launching. Our jammingand intercepting capabilities lower theprobability of CB weapons reachingtargets. Our detectors, alarms, andCB protective means lower theprobability of a casualty effect.

The CB casualty effect is relatedto the dosage delivered to the target.It depends on the functional qualitiesof the CB weapon (agent, delivery,dissemination), the protective actionof the target, and the environmentalconditions (terrain, weather). Dosagerefers to an amount of agent receivedwhen inhaled or absorbed through theskin; it is associated with a cumulativeprobability of casualty production. Forchemical agents and toxins, which relyon combined effects, the doseresponse is estimated by a probitanalysis. The dose response ofbiological organisms capable ofreproduction is estimated byintroducing an exponential probabilityof infection. Lowering the dosagedelivered (masking) lowers theprobability of casualties. Likewise,vaccination and prophylactictherapeutics increase the mediancasualty dosage, thereby also loweringthe probability of casualties.

M139 Bomblet

M190 Honest John GB warhead

July–December 2006 27

Coverage

The mean area effect (MAE) ofa weapon is the area expected tosuffer 50 percent casualties ordamage.5 The MAE is a useful toolfor comparing different weaponssystems. If the dosage over a targetis uniform, the MAE is the areacovered by the median casualtydosage.6

For comparison, during periods ofneutral atmospheric stability(Pasquill-Gifford stability Class D)over open, level terrain or on an urbantarget, the MAE for a 500-poundcluster bomb containing 200fragmentation bomblets is about halfa hectare. Under similar conditions,but with a biological variant in whicheach bomblet delivers 1 x 108 medianinfective doses for an agent with anaerobiological decay rate of 5 percentper minute, the MAE is about 11.4square kilometers. The MAE for theM34A1 is about 3 hectares and forthe M190, approximately 0.9 squarekilometer.

The elasticity of CB weapons toterrain and meteorological conditionsis what distinguishes the MAE of aCB cluster weapon from that of afragmentation cluster bomb. Over ajungle, a biological cluster bomb mayhave an MAE of 4.8 squarekilometers, while the same bomb mayhave an MAE of 38.8 squarekilometers over open terrain understable atmospheric conditions. Thecoverage area of a fragmentationcluster bomb is relatively unaltered,regardless of these factors.7

In the early 1950s, a medium-sizebomber was capable of attacking 30square miles with a biological clusterbomb. By the late 1950s, with theintroduction of self-dispersingbomblets, the area had increased to100 square miles. These sphericalbomblets, subject to the Magnus lifteffect, spread laterally from the point

of release to cover significantly largerareas than did traditional cylindricalbomblets, such as the M125. Thegreater the glide angle of the bomblet,the greater the area covered. By the1960s, with the Flettner rotarbiological bomblet (which has a glideangle of about 44 degrees), it waspossible for a single B-52 bomber, withits Hayes dispenser, to cover an areaapproaching 20,000 square kilometersin size.

Duds and Blinds

In the United States, a munitionthat fails to function (explode) is calleda “dud;” and in Europe, it is called a“blind.” There is a difference betweenthe engineered failure rate forweapons and the actual number ofduds or blinds experienced on thebattlefield. Rough terrain, vegetation,soft soil, mud, and snow contribute tothe number of failures experienced.In addition, a bomblet that strikes theground at an incorrect angle may alsofail to detonate.

Different weapons pose differentfailure rates. In general, 2 percent ofartillery rounds and 5 percent ofbomblets fail to function. However,experience in the Vietnam and GulfWars indicated an actual failure rateof 20 to 30 percent. For example, theMK20 Rockeye, used in the GulfWars, had a poor reputation, with 30to 40 percent of its submunitionsfailing.8 In addition, though the statedfunctional efficiency of the M34A1was 90 percent and the M190 was95 percent, in actual testing over level,arid terrain, the rates dropped to 75and 90 percent, respectively.

If a target in a future conflict issubjected to a strike by a weapon witha failure rate similar to the M34A1,about 19 unexploded GB bombletscould hypothetically be expected overa 2.3-hectare area. If the failure rateof the warhead used is similar to theM190, 35 unexploded bomblets could

be expected over an 80-hectare area.About half of these unexplodedweapons would be armed.Consequently, there is significantpotential for a future incident involvingUXO.

Given that a fragmentationbomblet is lethal over a 30-meterradius, the area at risk upon accidentaldetonation is 0.3 hectare per bomblet.9

Under neutral atmospheric stability,the area covered by more than a 5milligram-minute/cubic meter (mg-min/m3) dosage (negligible risk) ofagent GB is about 0.5 hectare for eachbomblet. Under stable atmosphericconditions, the area increases toaround 1.5 hectares.10 In other words,GB bomblets have up to five timesthe casualty potential of fragmentationbomblets.

Risks

The probability that a personcrossing an area previously struck bya clustered weapon will encounter anunexploded bomblet (P

E) is—

B

E A

dLP ⎟

⎠⎞

⎜⎝⎛ ×−−= 11

The distance traversed (L) into thearea (A) containing a randomlydistributed number of blinds (B) isinfluenced by the diameter of thepotential impact (d).11 When crossingstraight through the center of anM34A1 or M190 impact area, aperson has a 1 to 3 percent chance ofcoming in contact with UXO. Half ofthese bomblets may function oncontact, leading to a fratricide event,with agent GB extending 0.5 to 1.5hectares downwind.

From an epidemiological approach,the individual risk from UXO (K) is:

BP

ACK

××=

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Dividing the number of casualties perincident (C) and the area affected (A)by the product of the population (P)and amount of UXO (B) yields therate of casualties per month perpopulation density and incident.

Only recently have statistics beenused to measure the risks associatedwith UXO—the best examples ofwhich are from Kosovo and Laos.These statistics reflect the problemand assist in the global managementof the issue but are not of use prior toa conflict.12

The application of individual riskto unexploded CB weapons isproblematic. Explosive ordnance isgenerally accompanied by a circulararea of risk with a decided fractionof casualties and fatalities. CBweapons, however, are accompaniedby areas of risk that are irregularlyshaped—extending windward fromthe point of impact. The difference inthe number of casualties and fatalitiesdepends on dosage, which withatmospheric diffusion and dosageresponse variables, normally results ina greater number of casualties thanfatalities. Many CB agents (such asBZ) are not lethal and do not result indebilitating wounds.

Mitigation

The storage stability of some ofthe agents present in unexploded CBweapons is high. Unstabilized nerveagents and binary agents have decayrates as high as 5 to 8 percent permonth, greatly reducing the potentialfor loss of life with time. Manychemical agents are stable fordecades—if not centuries. Underambient conditions, anthrax has a half-life of 3 to 5 years. Vegetativebiological agents have half-livesmeasured in weeks. This stability wasillustrated on 29 November 1995,when a construction crew unearthedM114 bomblets at Wright-PattersonAir Force Base, Ohio. These

bomblets were the remnants of early1950s operational testing for animmediate biological capability withbrucellosis (agents AB and US).Following years of abandonment,the agent had been completelyinactivated, and there was no majorhuman health concern.13

Deliberately lowering the riskassociated with unexploded CBweapons starts with weapon design.One approach is the use of self-destructing fuzes. This concept wasincorporated into the delayed actiondissemination technique (DADT)fuzing of the Flettner rotor bomblettoward the end of the U.S. biologicalprogram. The internal fuze initiatedthe gas expulsion system of thebomblet in the event that tamperingor a specific temperature, humidity, orlighting condition was detected. Thefuze also self-destructed at a specifictime (under three days) through theuse of a variable delay battery relay.A problem with such fuzing is theincreased cost. For example, theM223 fuzes on many fragmentationbomblets are priced at 27 cents each.Replacing these fuzes with self-destructing ones increases the cost to$2.31 each. The decision to includeself-destructing design features willdepend largely on the possibility offuture enemy occupation.

Programs for the clearance oftraditional UXO may have rates ofremoval on the order of 200 to 300ordnance pieces per month, at a costof $1,500 per item. With the presenceof CB weapons, removal managementbecomes more complicated; therefore,the rate of removal can be expectedto drop significantly. An incident thatclearly demonstrates this pointrecently occurred at Rocky MountainArsenal. When an M139 bomblet wasdiscovered in a scrap yard, officialsplanned to destroy it in place using 5pounds of high explosives. Theexplosives were not only to destroy

the bomblet, but also to incinerate theGB agent content. The entire effortwas to take two weeks and cost$25,000. Instead, after eight months,disposal experts finally built aprotective enclosure around thebomblet and removed it for detonationin a containment vessel at a cost of$8.5 million. If this is the level of effortthat will be needed to clear future CBbattlefields, then such battlefields willlikely remain uninhabited, without anyattempt to reclaim the land.14 Endnotes:

1The M114 was the biological bombletused in the M33 cluster bomb, an improvedversion of the 4-pound World War II bombletthe British developed for use with anthrax.The M33 was an interim item providingbiological capability with agents AB and US.

2The M79 (E19R1) preceded the M190.This earlier warhead was developed for theM31A1C version of the Honest John, whichwas phased out for the XM50 version. TheHonest John never entered production.

3Sherman L. Davis, GB Warheads forArmy Ballistic Missiles: 1950–1966, HistoricalMonograph AMC 51M, U.S. Army MaterielCommand, Edgewood Arsenal, Maryland,July 1968.

4There are various probability modelswith regard to an attack. This version wasderived by the author after considering theapproaches of Lieutenant Colonel William T.McLarty, Jr. (“Technology Implications: TheNeed for Change,” Military Review, January1983, pp. 47–57) and James N. Constant(Fundamentals of Strategic Weapons: Offenseand Defense Systems, 1981).

5John H. Arnold, Air Armament Planningand Design Through Systems Analysis,AFATL-TR-72-28, Air Force ArmamentLaboratory, Eglin Air Force Base, Florida,February 1972 [AD894091]. A problem withthis approach is the lack of consistency in theconditional parameter, which provides a roughestimate, at best, when compared to field trialdata.

6Using a Newton-Cotes type integrationon data from various field trials in which halfthe area has been covered by the mediancasualty dosage for agent GB demonstratesthat this is a reasonable estimate, plus or minus10 percent.

7The MAEs for this hypotheticalbiological cluster bomb are derived from figuresin Field Manual (FM) 3-10, Chemical andBiological Weapons Employment (nowobsolete), 1962.

July–December 2006 29

8Lieutenant Colonel Gary W. Wright, “Scatterable Munitions=Unexploded Ordnance (UXO)=Fratricide,” U.S. Army War College,Carlisle Barracks, Pennsylvania, March 1993 [ADA264233].

9General Sir Hugh Beach, “Cluster Bombs: The Case for NewControls,” Briefing Paper Number 25, International Security InformationService, Brussels, Belgium, May 2001.

10Estimates for the M34A1 and M190 were made from field trialdata contained in Joint CB Technical Data Source Book, Volume III,Sub-Volume 3 (Appendices, G Nerve Agents, Part 2: Agent GB), U.S.Army Dugway Proving Ground, Utah, December 1976 [ADB019437L].

11Naval Operations Analysis, U.S. Naval Academy, 1968, p. 208.12“Explosive Remnants of War (ERW)—A Threat Analysis,”

Geneva International Centre for Humanitarian Demining, Geneva,Switzerland, 2002.

13“Bomblets Contain Brucella Bacteria,” United Press International,8 December 1995.

14Albert J. Mauroni, Chemical Demilitarization: Public PolicyAspects, Praeger Publishers, April 2003.

Mr. Kirby is a project manager for Strategic Staffing Solutions(S3). He holds a bachelor’s degree in valuation science fromLindenwood College, with a minor in biology and specialstudies in behavioral toxicology and biotechnology.

The 86th Chemical Mortar Battalion willhold its 2007 reunion at Fort Leonard Wood,Missouri, 11–15 April. For additionalinformation, contact George Murray bytelephone at (256) 820-4415, or look for detailsin the next Lobster newsletter.

Chemical School Receives FullAccreditation

By Mr. Robert Johnson

Like a schoolboy waiting for his report card, the U.S. Army Chemical School breathed a sigh of relief as itreceived full accreditation from the U.S. Army Training and Doctrine Command (TRADOC) on 29 March 2006. TheU.S. Army Military Police School, also located at Fort Leonard Wood, Missouri, received full accreditation as well.

According to Bob Wilhelm, an evaluator at the Maneuver Support Center (MANSCEN) Quality Assurance Office,standards in training, training support, and proponent functions were measured during the accreditation process. “Thisis a really big deal for both schools and, yes, it is like a report card,” Wilhelm said. “Both schools had to achieve an 80percent or better [score] across all 24 standards to receive the full accreditation standing. If the schools had met everystandard at 100 percent, they would have been listed as an Institute of Excellence, but nobody in TRADOC is going tosee that level this year. There are too many issues, such as funding, that are beyond the gates of Fort Leonard Woodthat would influence that level of rating. In today’s tight budgets, full accreditation is a high achievement,” Wilhelmsaid. “The process starts with a self-assessment, which is a serious look at yourself and how you are training, thenTRADOC provides an assistance visit to help the school meet areas where there are shortfalls or deficiencies . . . .”Wilhelm said.

The Chemical and Military Police Schools join the U.S. Army Engineer School (USAES) and the MANSCENNoncommissioned Officer Academy (NCOA) (both based at Fort Leonard Wood) in their accreditation award status.The USAES and the NCOA received their ratings in July 2004.

Mr. Johnson is the managing editor for the Fort Leonard Wood Guidon.