Small Effective Air-to-Surface Munitions for Unmanned Tactical Aircraft Applications

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Small Effective Air-to-Surface Munitions for UnmannedTactical Aircraft ApplicationsD. R. BrubakerWright Laboratory Armament DirectorateMunitions Assessment Division

Technology Assessment Branch (WIJMNSA)101 West Eglin Blvd, Suite 326Eglin AFE , Florida, 32542-6810USA

1.0 SUMMARYThis paper describes two emerging munitiontechnologies beneficial to Unmanned TacticalAircraft (UTA) and attempts to define anecessaryweapon load capability. Todetermine a weapon/loadout combination thatmaximized the lethal effectiveness of an UTAwhile minimizing the payload weight required,a mission level analysis was conducted andconcludes that a minimum of lOOO-lb (454 kg)of payload provides an UTA a viable air-to-ground combat mission capability. A 2000~lb(908 kg) payload provides an increasedeffectiveness but must be contrasted with theassociated ncrease in UTA cost, size, weightand propulsion needed to employ theadditional payload weight.2.0 INTRODUCTIONAs the name implies, an Unmanned TacticalAircraft (UTA), has a mission requirement toprovide a combat capability as opposed to onlya non-combat mission role, such as providingreconnaissance,surveillance, or assessmentofbattle damage to enemy targets. Currently, toprovide a combat capability against fixed-soft,fixed-hardened and stationary ground targets,the UTA must be capable of carriage anddeployment of air-to-surface munitions.Unfortunately, a payload capability equivalent

to only one 2000 pound (908 kg) classmunition may require the UTA design toincrease in size beyond what is acceptable withrespect to cost and/or logistic goals. Smaller,high precision, autonomous munitions havebeen envisioned to provide the UTA with adesired level of combat capability. Enablingtechnologies being developed anddemonstrated in US Air Force laboratories arebeginning to provide new small weaponsystems well suited to an UTA role. It is clearthat a selection of munition options for UTAoperations is critical to maximizing the utilityand mission. Additionally, a systemengineering approach is necessary o ensurethat the munitions be incorporated into theUTA design early in the development phaseespecially since the munitions play such a keyrole in providing the basis for the desiredcombat capability.3.0 MUNITIONS3.1 Low Cost Autonomous Attack System(LOCAAS)LOCAAS has successfully merged three newlydeveloped technologies into a weapon thatcould change the nature of air-to-surface anti-materiel warfare. When the compact airframedesign is fitted with a state-of-the-art

Paper presented at the AGARD MSP Symposium on System Design Considerations for Unmanned TacticalAircraft (UTAJ. held in Athens, Greece, 7-9 October 1997, and published in CP-594.


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sensor/seeker,and an adaptable warheadsystem the results are a highly capable weaponsystem that puts all fixed-soft, mobile andrelocatable targets at risk. LOCAAS offersnumerous benefits to the battle managers.Launch platforms will be held out of harmsway due to the standoff capability. Platformscarrying twelve LOCAAS units have the lethalcapability of 6 platforms each carrying twoMaverick missiles. The increase in sortieeffectiveness should increase the tempo of theconflict as well.LOCAAS houses a Laser Detection andRanging (LADAR) seeker developed toaccurately and autonomously acquire, classify,and track targets during the attack. With thiscapability, LOCAAS scans he battlefield,finds potential targets, and then switches into atrack mode to differentiate between tanks,trucks, missile launchers and radar sites. Oncethe LADAR unit determines a valid target thecomputer selects the appropriate killmechanism to maximize the lethaleffectiveness. The multi-mode, shaped-chargewarhead can selectively fire an armorpenetrating long-rod if the target is heavilyarmored, such as a battle tank. If the target islightly armored or protected by reactive armorthe warhead can select a penetrating aero-stable slug. Finally, if the target is soft orthin-skinned like a surface-to-air missilelauncher, radar site, or theater ballistic missile,the warhead can operate in a fragmentationmode to distribute lethal fragments over alarge area. This unique warhead achieves thethree modes of operation by selectivelydetonating high explosive behind a copperplate. One mode forms the plate into a longrod. The second mode forms the aero-stableslug and the third mode causes he plate tobreak into multiple fragments.The LOCAAS, shown in Figure 1, is 30 inches(76.2 cm) long and weighs approximately 100-

lbs (45.4 kg). A miniature turbo-jet engineprovides 100 nautical miles (185.2 km) rangeand the ability to search over large areas, Thesmall size provides the ability to packagenumerous LOCASS units in current and futuredelivery platforms.Warhead tests have been completedsuccessfully. Seeker testing is ongoing. Ashort non-powered flight test has demonstratedthe autonomous search, acquisition, target-classification and attack modes. All-up flighttests will occur within the next couple of years.Completion of the LOCAAS development willprovide the war-righter a very effectivemunition to defeat advancing mechanizedtroops as well as perform missions to suppressenemy air defenses during the early phases of aconflict and open the paths for air-to-surfacemunitions like the small smart bomb describednext.

Figure 1. Full Scale Model of LOCAAS3.2 X0-lb (113.5 kg) PenetratorAt the time of this writing, the operationalcapability of a 250-lb (113.5 kg) Small SmartBomb (SSB) concept had recently beendemonstrated under the Miniaturized MunitionTechnology Demonstration Programconducted at Wright Laboratory ArmamentDirectorate (WI/MN), Eglin Air Force Base,Florida. The Miniaturized MunitionTechnology Demonstration (MMTD) program
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27-3had the objective of developing a ZO-lb While these benefits are evolutionary in(113.5 kg) class munition that is effective nature, a truly revolutionary benefit can occuragainst many of the fixed soft and hardened when aircraft designers take advantage of thetargets previously vulnerable to only 2 ,000-lb smaller munitions and reduce the size of(908 kg) class munitions. Figure 2 compares aircraft weapons bays, in turn reducing the sizethe size of the MMTD test vehicle to a 2000-lb and cost of future aircraft like the UTA.(908 kg) class general-purpose munition.

The MMTD goal was to baseline small bombtechnology and demonstrate the operationalutility of a 250-lb (113.5 kg) class precision-guided munition. The MMTD munition useda Differential GPSlINS system to achieve aprecision guidance accuracy of less than 9.8feet (3-meters) CEP against a surveyed target.The weapon size requirements [6 inchdiameter, 72 inch length, (182.9 cm) and 250-lb (113 kg) total weight] meant that thewarhead design spacewas relatively small. Toachieve the reinforced concrete penetrationgoal of 6 feet (1.8 meters) with a small,lightweight weapon, the warhead was designedFigure 2. Full Scale Models of MMTD[upper] and 20004b (908 kg) [lower]

There are many benefits to smaller bombs, thegreatest of which is an increased oadoutcapability for fighter and bomber aircraft.With each bomb independently targeted andautonomously guided, the number of targetskilled by a single fighter or bomber sortie canbe tripled or even quadrupled. Besides thecapability to increase sortie effectiveness andthe number of kills per pass, the smallervolume and weight of 250-lb (113 kg)munitions versus the more typical 2000~lb(908 kg) munition means 3 to 4 times as manybombs can be transported with current airliftcapability; allowing a much more rapiddeployment of warfighting capability to theregion of conflict. Another benefit is that thebombs accuracy and lower explosive yieldwill focus the lethality on the target whilereducing the potential for collateral damage onfriendly forces and noncombatants alike.

with a biconic nose shape. The ArmamentDirectorate-developed Hard Target Smart Fuze(HTSF) has been incorporated into thewarhead for determining the optimumdetonation point, This fuze has the ability todiscriminate between media (concrete, soil, air,etc.) and determine when it has entered a void(room) in a target and then detonates the mainexplosive charge. The goal of carrying 50-lbs(22,7 kg) of explosive had to be traded offwith penetration/survivability goals. Thecurrent design allows 42-lbs (19.1 kg) of high-explosive to be packaged n the warhead. Thefirst phase of the MMTD began in September1995 and was an 1g-month effort concludingin March 1997. Ground tests consisted ofcannon and sled track testing for penetrationperformance and arena testing for determiningwarhead lethality. Five flight tests wereconducted culminating in a live drop against arealistic aircraft shelter.On 25 June 1996, the first penetration andsurvivability tests of the final warhead designwere conducted. The initial test fired the
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warhead into a 6 foot (1.8 meter) block ofconcrete reinforced with 1 inch (2.54 cm)rebar. W ith an impact velocity ofapproximately 1200 feet per second, (365.8meters per second) the warhead successfullypenetrated the target and exited cleanly on theother side (Figure 4). After recovery andinspection of the warhead, the only noticeablechange was that the paint was stripped off.Since that test, the warhead has been shown topenetrate over 6 feet (1.83 meters) ofreinforced concrete and still be survivable atimpact velocities above 1400 feet per second,(426.8 meters per second) impact angels of 70degrees, and angles of attack up to 2 degrees.Additional tests in January 1997 successfullydemonstrated the end-to-end function of thewarhead with a live Hard Target Smart Fuze(HTSF) and Jive explosive fill against a 6 foot(1.83 meter) reinforced concrete target.A series of captive flight test were conductedprior to the five free-flight tests, which began23 December 1997. The first three MMTDswere released from altitudes of 30000 (9.14km), 25000 (7.62 km), 40000 feet (12.2 km)and at varying distances down-range and cross-range from the reinforced concrete target slabs.The target slabs, measured 20 feet (6.1 m) by20 feet (6.1 m) and 3 feet (.914 m) thick restedhorizontally on the ground. The bombs allimpacted within a 9.8 foot (3 meter) radiusfrom the aimpoint. Impact velocities greaterthan 1100 feet per second (335.4 meters persecond) were achieved with impact angles ofapproximately 83 degrees from the horizontaland less than a 1 degree angle-of-attack, TheMMTD penetrated the 3 foot (.9 14 m) concreteslab and attempts to locate the warhead fromthe first tests ended after probing 40 feet (12.2meters) deep in the soil.The fmal flight test was conducted todemonstrate the operational utility of the smallbomb concept. Two weapons were dropped

one second apart on a single pass against twoindividual targets separated by roughly 300feet (91.4 meters). Each weapon successfullyguided to their intended target after beingreleased from 40000 feet (12.2 km) altitude.The MMTDs were released over 10 nauticalmiles (18.52 km) down range and off-axisfrom the target requiring the weapons tomaneuver to impact. The warheads enteredovercast weather from 30000 feet (9.14 km) to2000 (0.6 1 km) feet thereby demonstrating theall weather capability. After release the pilotturned away from the target and althoughegressing subsonic, was over 20 nautical miles(37 km) from the target location at weaponimpact.

Figure 3a. Pre Test Results

Figure 3b. Post Test Results
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One inert weapon demonstrated the folding finmechanism and successfully guided to itstarget, which was a dummy aircraft shelter.The second weapon carried 42lbs (19.1 kg) oftritonal and a live fuze. The aircraft sheltertarget for this second weapon was covered byroughly 6 feet (1.8 meter) of soil and a layer ofconcrete. Additionally, a retired A-7 aircraftwas parked inside the shelter and the shelterdoors were left open for camera coverage ofthe test. The live warhead guided to thetarget, penetrated the shelter and detonated atthe desired location determined by the hardtarget smart fuze. Figure 3 reveals thecatastrophic damage to the aircraft from theMMTD detonation.The successof the MMTD program hasdemonstrated that the technology necessary odevelop a small smart bomb is currentlyavailable and that the weapon concept canprovide a multiple kills-per-pass capability. Asecond phase of MMTD tests is planned forFY99-02 and may include the integration of aterminal seeker, wing-kit for increasedstandoff, and anti-jam GPS technology into thebaseline weapon. Additional futureopportunities to demonstrate the capability ofthe small smart bomb could include integrationof the munition on an uninhabited aerialvehicle (UAV) in the newly formed UAVbattle lab at Eglin AFB.4.0 ANALYSIS4.1 MunitionsAlthough small autonomous munitions forboth fixed and mobile targets are beingdeveloped at Eglin that are applicable for anUTA role this analysis involved onlymunitions for fixed and relocatable targets.The decision was based on the fact thatmunitions for fixed targets require greaterpayload capacity therefore they would drivethe UTA weapon carriage requirements. An

UTA with a fixed target capability would thenalso have the ability to carry smaller mobiletarget munitions, i.e. LOCAAS, described inthis report. Three fixed and relocatable targetweapons were used in this study, a lOOO-lb(454 kg) general purpose, lOOO-lb (454 kg)penetrator and a 250-lb (113 kg) penetrator.All munition effectiveness numbers werebased on 26 foot (8 meter) and 10 foot (3meter) Circular Error Probable (CEP) accuracyestimates. The 26 foot (8 meter) accuracy isobtained from an Inertial Navigation System /Global Positioning System (INWGPS)guidance scheme. A terminal seeker isassumedbe required to achieve the 10 foot (3meter) accuracy.4.2 Target ListIt is important here to define the terminologythat will be used to describe targets in thisreport. Target types include fixed soft, fixedhard, stationary and mobile. Fixed targetsinclude buildings, underground bunkers,aircraft shelters, etc. Each of these fixedtargets could be soft or hard. Thedistinction although somewhat subjective, inthis paper refers to whether constructionmethods are employed specifically to protectthe target from damage due to blast, fragmentand/or penetration. A stationary target isunderstood to represent a target that can bemoved, but which requires time anddismantling prior to transportation. As anexample, a Transporter, Erector, Launcher(TEL) would be considered a stationary targetsince the launcher requires dismanthng andstowage before it can be moved. Mobiletargets include trucks, battle-tanks, armoredpersonnel carriers, etc.A target type also can consist of unitary ormultiple elements. A unitary target type wouldbe a single building, for example, while amultiple element target type could be aPetroleum, Oils, and Lubrication (POL) field


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containing numerous POL storage tanks.Thus, a POL target with 10 POL tanks wouldbe a single target type with 10 targetelements. A kill of this POL target wouldresult in up to10 target elements killed. Atheater can contain many target types andmultiples of each type with each type havingone or more elements.The targets selected for this analysis contained61 different target types resulting in 3720 totaltargets and 34930 total elements. Table Igives a breakdown of these targets by type andquantity. No personnel or mobile targets wereincluded in this target set.

Target Number TotalType of Types Number ofElements

Hard, Fixed 22 1458Soft, Fixed 32 19828Relocatable 7 522Table 1. Target List by Type andQuantity

4.3 LoadoutVarious loadout configurations were usedwith each of the appropriate weapons in thisstudy+Loadouts of 1 and 2 were used for thelOOO-lb 454 kg) munition while a for the SSBthe loadouts were varied between 2,4, and 8.By varying the loadout options it was possibleto investigate the effect of loadout and todetermine an optimum loadout quantity. 2000-lb (908 kg) munitions were not used.4.4 MethodologyAnalysis was accomplished using acceptedprocedures as defined by the Joint TechnicalCoordinating Group for MunitionsEffectiveness (Air-to-Surface), Standard JointMunitions Effectiveness Manuals and the

Open-End Methods (Reference 2) were usedthroughout.5.0 RESULTSPrior to reviewing the results of the analysis itis important to understand the figure of meritused to draw conclusions. The term ExpectedKills per Sortie (EKS) represents the ability ofa delivery platform to defeat multiple targetson a single sortie and is indicative of thenumber of weapons that can be carried anddeployed by that platform. The average EKSis simply the total number of elements in thetarget set divided by the total number of sortiesneeded to kill all the elements in that sametarget set. It should be remembered that somemunitions will be more efficient at defeatingsome target type/elements , and much lessefficient at others. Computing an average willresult in a loss of this fidelity, however anaverage is an indication of the pervasiveness ofa munitions effectiveness across all targetsThe following figures will provide insight as tothe UTA loadouts necessary o achieve adesired level of effectiveness against thecomplete target set.

Figure 4. Expected Kills/Sortie for UTAFrom Figure 4, we see hat to achieve theeffectiveness of two 454 kg GP munitionswould require a minimum of four SSBs with
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an &meter CEP accuracy or two SSBs with 3-meter accuracyPERCENT OF TARGETS WHERE SSB HAS BEST EKS

56 Target types, 34867 target elements I100 & LOAOOUT, 1 1

SSB (8m CEP) SW (3m CEP) I

Figure 5. Percent of Target Set WhereSSB has the Best EKS

Figure 5 shows the percentage of the 34867targets where the SSB expected-kill-per-sortievalue is higher than the loadout of two 454 kgmunitions. We see hat a loadout of four SSBsand &meter accuracy achieves a best EKSvalue for slightly less than 50% of the targetset. The two 454kg munitions achieve the bestEKS for the remaining 50% of the targets.However, a loadout of four SSBs with 3-meteraccuracy provides the best effectiveness foralmost 80 percent of the targets. By the time aloadout of 8 SSBs is reached, the SSB is themost effective weapon for 75 % of aI1 hetargets at either the 8 or 3-meter accuracy. Wecan make a couple of statements rom thisobservation: 1) There are some targets that arebest attacked with 454 kg class munitions, thusa UTA should be able to carry at least a 454 kgclass GP bomb, 2) Somewhere between 4 and8 SSBs with 8-meter accuracy there is asignificant number of additional targets whereSSB obtains the best EKS. Up to now therehas been no indication how much better theEKS value is for the SSB than the 454 kgmunition. Figure 6 helps answer this questionsince the target set is restricted to those targets

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where the SSB has been shown to have thebest EKS. Recall that this restricted set stillrepresents over 75% of the total origina l setused in this study. For this set of targets we seethat even a loadout of two SSBs is as effectiveas two 454 kg munitions and that four SSBsand 3-meter accuracy provide an average oftwo targets killed per sortie. When 4 SSBs,which represents 1000-lb (454 kg) in totalweight, is compared to a single 454 kgmunition of equal weight we can see hat onaverage, the four SSBs (8 meter accuracy)have over 3 times the EKS as the 454 kgweapon. At 3-meter accuracy 4 SSBs havealmost 9 times the EKS and has the equivalentweight of a single 454 kg munition.

EXPECTED KILLS PER SORTIEfor targets where SSB has best EKS

SSB IBm CEPI SSB 13m CEPl

Figure 6. Expected Kills Per Sortie(Targets where SSB has the Best EKS)This would allow the required number ofsorties to be reduced by 300% for an 8-meterSSB and by almost an order of magnitude for a3-meter accuracy munition. In addition toincreasing the conflict tempo, by attackingmultiple targets per sortie, a reduction in thetotal number of sorties required would alsoreduce attrition, sortie cost, and possiblyconflict duration. If these advantages could berealized the additional cost of a terminal seekerto provide a 3-meter accuracy might certainlybe justified+
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Reviewing figures 4 to 6 with an UTAperspective, a conclusion can be drawnpertinent for the UTA developers. Theconclusion is that significant missionflexibility occurs with a minimum payload of1000 pounds (454 kg). This would allowcarriage and deployment of one lOOO-lb (454kg) munitions, two 500-lb (227 kg) munitions,or 4 SSBs. This mix of munitions covers allbut the very hardest fixed ground targets.Maximum mission flexibility would occurwith a 2000 pound (908 kg) payload capabilityallowing the loadouts described above todouble and provides additional lethaleffectiveness.6.0CONCLUSIONSThe conclusion of this study is that a smallmunition concept like the SSB, currently beingdemonstrated at WUMN provides excellenteffectiveness for all aircraft platformsincluding an UTA concept. The previous trendfor USAF munitions was to increase size,weight, and explosive load, but thecorresponding reduction in loadout using alarge, heavy munition can reduced the overalleffectiveness of each sortie. The high loadoutsfurnished by the SSB and LOCAAS conceptshave increased the sortie effectivenesssubstantially. Even though multiple SSBs mayneed to be used against a target, the SSBloadouts possible more than make up for thisdeficit. Additionally, the increased numbers ofmunitions on-target can provide an increasedstatistical probability of destroying a criticalnode of the target over a single large munition.The SSB, in its current configuration, is aneffective and viable UTA munition. The smallsize and weight provides the UTA platform adesirable combat capability for a large numberof targets. The study suggests hat an UTAwith 2000-lb (908 kg) of payload is optimumfor a combat capability. With 2000-lb (908kg) of payload the UTA could carry two 1OOO-lb (454 kg), 8 SSBs, or 16 LOCAAS. With

this flexibility all but the hardest targets are atrisk, The soft targets are best defeated withLOCAAS. Large area targets, are mostsusceptible to large blastffiag, general purposemunitions like the lOOO-lb (454 kg). The UTAcould carry the 1000-lb (454 kg) munitionsside-by-side or 4 SSBs on each side ofcenterline. The next best payload for the UTAis lOOO-lb (454 kg) and results in a singlelOOO-lb (454 kg), 4 SSBs or 8 LGCAAS.While this is less effective than 2000-lbs (908kg) of payload, it does allow a smaller UTAdesign and reduce the propulsion requirements.This payload allows a centerline weapons bayinstead of the side-by-side bay mentionedearlier. From figures 4 to 6 it is seen that adrop in UTA payload to 500~lbs (227 kg) onlyallows two SSBs to be carried with the drasticreduction in effectiveness. With only a 500-lb(227 kg) loadout, more sorties would need tobe conducted putting the UTA at risk andincreasing cost and conflict duration. In short,the UTA should maintain a ION?-lb (454 kg)minimum payload if it is to be signfxantlyeflective against the target set of interest.Not addressed n this study are the aircraftintegration and weapon interface issuespertinent to high loadout munitions like theSSB. For current manned aircraft the Mil-Std-1760 capability is required since data must bepassed o each munition. In addition to having1760 capability, the aircraft Operational FlightProfile (OFP) software would need to bedeveloped to correctly initialize, arm,sequence,etc. the multiple munitions. ForUTA utilization, similar integration issues arefound. While the concept of operations for theSSB would likely provide for loading the GPStarget coordinates via mission planning cockpitdata cartridge and 1760 interface prior toflight, future real-time targeting would requirethe capability to pass this information fromplatform to SSB during flight. The OFPsoftware for an UTA may be even more


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complex than for a manned aircraft since alarge amount of data that is currently handledby a pilot, may need to be passed romonboard sensors o a manned ground-stationsupport facility. For an UTA combat missionwhere a target needs to be identified andclassified prior to authorizing weapon release,the data may be even more critical especially ifthe UTA is used in a close-air-support role.Finally, early UTA design criteria shouldinclude the requirement for a munitiondispenser to maintain the ability to packageand release multiple munitions. Dispensertechnology is critical to achieve high loadoutsin a small volume like an UTA. The dispensertechnology must provide the capability torelease unitary munitions or multiplemunitions. on a target to provide the mosteffective sortie. Most current dispensers hathave been demonstrated are dropped as a unitand the dispensing of submunitions occur later.Since the SS?s and LOCAAS need to bedropped as unitary or multiples to achieve thebest effectiveness, the dispenser would mostlikely be a captive dispenser. It would seemprudent to develop dispenser technology thatwould be adaptable to both manned aircraftand UTA concepts, but this dispenser conceptwould obviously impact the UTA design andshould be integrated early in the design phase.7.0 REFERENCES1. Brubaker, D, A Mission LevelEffectiveness Study of a 250-lb Class Air-to-Surface Munition Concept (U), WL-TR- 1997-7002, January 19972. Personal Computer Users Manual forJMEM/AS Open-End Methods, JointTechnical Coordinating Group forMunitions Effectiveness (Air-to-Surface)6 1 JTCG/ME-3- 16, October 1993

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Small Effective Air-to-Surface Munitions for Unmanned Tactical Aircraft Applications