TBMD ANALYSES

T

Theater Ballistic Missile Defense Analyses

Wayne J. Pavalko, Kanaya R. Chevli, and Michael F. Monius

he U.S. Department of Defense is funding the development of Army, Navy, andAir Force systems to defend against Theater Ballistic Missiles (TBMs) as part of a JointTheater Ballistic Missile Defense (TBMD) architecture. The performance of thesesystems against TBMs is being assessed in operationally realistic situations throughoutall phases of development. This article describes a portion of APL’s role in the analysisof Navy and TBMD systems over the past several years. The results of the Laboratory’sefforts have added to our understanding of the operational requirements and per-formance of these emerging TBMD systems. (Keywords: EADSIM, Modeling, Navy,Simulations, TBMD.)

BACKGROUNDSince the early 1990s, DoD has funded the devel-

opment of Army, Navy, and Air Force systems todefend against Theater Ballistic Missiles (TBMs). Sev-eral APL departments have been an integral part ofthe engineering team analyzing the Navy’s TheaterBallistic Missile Defense (TBMD) systems currentlyunder development. Over the past several years, theJoint Mission Analysis Group (JMA) of the Labora-tory’s Joint Warfare Analysis Department has providedforce-level and operational analysis of these emergingTBMD systems.

TBMs are guided rockets with conventional war-heads or weapons of mass destruction that arelaunched at the enemy from long range. The GermanV-2 rockets that terrorized Londoners during WorldWar II were the earliest examples. More recently, how-ever, Iraq fired Scud missiles at Iran during the Iran/Iraq war, and at Israel and Saudi Arabia during Op-eration Desert Storm. The impact of a single Scud

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missile into the U.S. Army barracks in Dhahran, SaudiArabia, caused the largest loss of life of coalition forces.The relative inaccuracy of most TBMs renders themineffective for attacking specific military targets. How-ever, their use as weapons of terror against cities andas vehicles for delivering weapons of mass destructionmakes defense against them a high priority for the U.S.military.

TBMs typically have two phases of flight: boost andpostboost. In the boost phase, the TBM is powered byburning solid or liquid fuel. The TBM guidance systemmaintains a trajectory so that the warhead will hit thedesired location. After the fuel is depleted, the TBMtransitions to the unpowered postboost phase, duringwhich it flies ballistically (under the influence of gravityalone) toward the target. With some types of TBMs, theportion containing the warhead splits and flies separate-ly toward the target. In this case, the warhead portionis called the reentry vehicle. The portion of flight before

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apogee or maximum altitude is the ascent phase, andthe portion after apogee is the descent phase. Reentrystarts when the TBM experiences significant effects ofaerodynamic drag caused by the Earth’s atmosphere.Some TBMs correct for guidance errors by modifyingthe trajectory of reentry during flight. Other TBMs,mainly short-range missiles, guide themselves to thetarget after reentry by homing in on radar signalsemitted by the intended target. Figure 1 shows a typicalTBM trajectory and the phases of flight.

All TBMD systems must perform three main func-tions: detection and tracking, threat assessment andengagement scheduling, and engagement. Detectionand tracking involves creating a track or position es-timate of the TBM via RF or IR sensors. Threat assess-ment and engagement scheduling entails analyzing thecharacteristics of a track to determine if it representsa threat and, if so, scheduling an engagement of thethreat and managing the resources needed to supportthe engagement. In the final function, the TBM isengaged to prevent it from completing its intendedmission (also called threat negation).

Surveillance systems assist TBMD systems in thedetection and tracking function. These systems may besurface-based, airborne, or spaceborne. They contributeto Joint TBMD by providing early warning of TBMlaunches and, in some cases, estimates of the positionsof the TBMs. Data from these surveillance systems areforwarded to TBMD units in the field to assist in per-forming the TBMD mission. The following subsectionsdescribe various ways in which the performance ofNavy TBMD systems are analyzed.

Reentry vehicleseparation(separating

threats)Boost

Launch

Endo-atmosphere

Apogee

Reentry

Impact

Exo-atmosphere

Figure 1. TBM trajectory.

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One-on-One Analysis

One-on-one analysis assesses the performance of asingle shipboard TBMD system against one TBM for aspecific launch, impact, and ship geometry. This assess-ment can be done at a high or low level of detail,depending on the intended use of results. A high-detailassessment requires six-degree-of-freedom (6-DoF)threat models that generate position and body orien-tation information for the TBM’s components duringflight. IR and radar RF signatures of the TBM’s com-ponents must be available for this kind of analysis.Detection and tracking of the threat is modeled viadetailed simulations of sensors and the specific searchdoctrine used. The threat assessment and engagementscheduling function must be represented sufficiently toallow engagement of a single TBM. The missile portionof the engagement function is represented using 3- or6-DoF engineering models. To determine whether anengagement results in negation of the threat, the typeof TBM warhead and the expected damage to thewarhead must be considered. Expected damage is as-sessed using detailed models of the impact of the de-fending missile and the TBM warhead for hit-to-killsystems or, in the case of blast fragmentation systems,impact of fragments on the TBM warhead.

Again, the result of one-on-one analysis demonstratesthe performance of the system against a single TBM.When one-on-one analysis is run in Monte Carlo fash-ion, performance is given as a probability of threat ne-gation. If the results for a fixed TBMD ship position andmultiple TBM launch and impact locations are overlaid,

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the resulting display of defendablepoints is known as a defended area.If the results for multiple ship posi-tions for fixed launch and impactlocations are overlaid, the resultingarea for which a ship can successful-ly engage the TBM is called an op-erating area. In general, defendedareas display the region on theground that can be defended from athreat launch region for a fixedTBMD system position. Similarly,operating areas display the region inwhich a TBMD system can operateor maneuver and still protect a re-gion on the ground from a threatlaunch region. Figure 2 displaysexamples of defended and operatingareas.

The results are also used tocharacterize the performance of aTBMD system concept and caninfluence the design of future sys-tems. An example of one-on-one

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TBMD ANALYSES

Launcharea

Launcharea

Fixed TBMDsystem location

TBMD systemoperating area

Area to bedefended

Defended area

Figure 2. TBMD defended and operating areas.

analysis is the determination of the maximum three-dimensional engagement volume of a defending missileand the resulting defended area of the system. Thecombat system’s engagement scheduling function usesthis information to determine which threats can beengaged with a high probability of negation. Whensystem performance is characterized in a simple way,e.g., using a defended area, the characterization is oftenemployed in operational planning.

Many-on-One AnalysisMany-on-one analysis determines the effects of mul-

tiple targets that are closely spaced in time and spaceon all aspects of the TBMD system. The description ofa TBM raid is usually in terms of x TBMs launchingor impacting within y seconds. The simplest case iswhen TBMs impact the same location from the samelaunch point; the more complicated cases occur whenTBMs hit a defended region from a threat launch re-gion. Unlike engaging a single threat, engaging a raidmay result in

• Reduction in the performance of sensors to detect andtrack each member of a group of closely spaced targets

• Degradation of defending missile performance whenengaging a group of closely spaced targets

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• The need for the combat systemto schedule multiple, nearly si-multaneous engagements

A detailed many-on-one analy-sis often uses the same tools as adetailed one-on-one analysis, withthe addition of better engagementscheduling functions that accountfor multiple targets and the inclu-sion of multiple targets in the sen-sor models and 6-DoF missilemodels. The increased complexityof the many-on-one analysis alsomakes the presentation of resultsmore difficult than the one-on-one analysis. Many-on-one analy-sis is usually presented for a specif-ic threat raid and the systemgeometry based on the specificsystem’s requirement documents.Results can be presented for a sin-gle raid size but are more oftenpresented for a spectrum of raidsizes and timings.

Typical measures of effective-ness (MOEs) for many-on-oneanalysis are average number of tar-gets negated, distribution of thenumber of targets negated, proba-

bility of negating all targets, average number of targetsnot negated, average number of targets unengaged,total inventory expended, and inventory expended pertarget. To compute these averages, many-on-one casesare typically run in Monte Carlo fashion, with enoughiterations to reduce uncertainty in the outcome to anacceptable level.

The results of many-on-one analysis are also used tocharacterize the performance of a system concept andto influence the design of a future combat system. Anexample of many-on-one analysis is determination ofthe maximum number of engagements that can be pro-cessed simultaneously. The combat system may use thisnumber during engagement scheduling to ensure thatresources are available for all future engagements.When system performance in a multiple threat envi-ronment can be characterized simply, the characteriza-tion is often used to perform the many-on-many anal-ysis described next.

Force-on-Force AnalysisMany-on-many or force-on-force analysis considers

multiple TBMD systems against multiple threats. Thecomplexity and scope of the problem increase signifi-cantly in force-on-force analysis because of interactionsamong defensive systems. Simple cases are analyzed

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using the detailed methods described for one-on-oneand many-on-one analyses; however, complex casestypically require less detailed system models to reducethe time required for analysis. Although in one-on-oneanalysis the defending missile is modeled using a 3- or6-DoF model, force-on-force analysis typically uses anapproximation from time-of-flight tables, which specifythe time required for a defending missile to fly to a pointin space. Probability of single-shot engagement kill(PSSEK) tables are used to represent the geometric de-pendency of the defending missile’s performance.

Detection and tracking performance is also simpli-fied for force-on-force analysis by taking results fromhigher-detail radar models and scaling detection rangesbased on standard equations for radar propagation. Thecurrent force-on-force analysis approach used in JMAdoes not model radar resources or the dynamic re-allocation of radar resources. Instead, the performanceof TBMD systems is represented by limiting the radarresources for search and detection. Future analysis mayrequire that limited radar resources and dynamic radarresource allocation be modeled explicitly.

The interaction among multiple TBMD systems iswhere force-on-force analysis differs most from the one-on-one and many-on-one analyses described earlier.These systems interact through specific communica-tions paths such as data links among TBMD and sur-veillance systems that provide launch warnings andposition estimates for TBMs (cues), data links amongvarious TBMD systems (e.g., Link 11, Link 16, Coop-erative Engagement Capability), and voice links amongTBMD systems. Links to surveillance systems providecues that may allow earlier detection of TBMs byTBMD systems if the cues are precise enough for localsensors to acquire the target. Links among the variousTBMD systems also provide cues that may allow earlierdetection. In cases where initial detection would bemade too late or not at all by a ship’s own systemsensors, cues can substantially increase a system’s per-formance. These links also facilitate engagement coor-dination among the TBMD systems. Coordination canrange from simply notifying other units that a track hasbeen engaged to exchanging detailed engagement in-formation to support complex engagement coordina-tion. (Voice links can also be used to exchange generaloperational information, but are not envisioned as theprimary method to coordinate TBM engagements.)

The addition of other units in the analysis requiresrepresenting their systems, links among systems, andmethods by which the units use the linked data. If theother units are TBMD systems, they are representedsimilarly as in one-on-one and many-on-one analyses.If they are strictly surveillance units, their sensor per-formance must be considered. In some cases, surveil-lance units are represented explicitly by modeling theRF or IR detection process of their sensors. In other

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cases, they are represented by assuming detection rang-es and average delay times for receipt of the databy other units. The representations for links amongsystems vary from instantaneous communications toconstant delays to detailed link modeling that includesthroughput limitations. The way units use link data canalso vary greatly. In the case of cues, the search processcan be modeled explicitly or represented simply byassuming that cues are either not used by the receivingunit or that cues result in acquisition of the threat bythe receiving unit after some time delay. The use ofengagement coordination data varies greatly as well.

The simplest form of force-on-force analysis extendsone-on-one or many-on-one by adding surveillanceunits that provide surveillance information. The resultsof this analysis show the effects of surveillance assetson one-on-one and many-on-one MOEs. These resultsare given as a function of relative positions of surveil-lance units and TBMD systems.

A more complex form of force-on-force analysis addsmultiple engaging units and either single or multiplethreats. This analysis is utilized to assess force-levelperformance and engagement coordination methodsusing multiple, identical systems or multiple systems ofdifferent types. For single threats, this approach showsthe performance of multiple units against a singlethreat. For multiple threats, it shows the performanceof multiple units against multiple threats and is used toevaluate multi-unit raid rate requirements and engage-ment coordination concepts. In addition to many-on-one MOEs, other measures are computed to determinethe efficiency of engagement coordination methods.

A primary tool for force-on-force analysis at APL isthe Extended Air Defense Simulation (EADSIM),which was developed by Teledyne Brown Engineeringfor the Ballistic Missile Defense Organization(BMDO). APL has employed EADSIM since 1992 andis now one of its main users within the Navy. JMA hasdeveloped methods to input 3- and 6-DoF data intoEADSIM and maintains an extensive database of per-formance data for use in TBMD analyses. EADSIMprovides generic system representations that can betailored via input data to model several TBMD systems.

Operational AnalysisOperational analysis applies one-on-one, many-on-

one, and force-on-force analyses to operationally real-istic situations. It involves examining specific TBMtrajectories and specific unit locations that are tied togeographic areas. Operational analysis usually does notrequire major changes in analysis methodologies. How-ever, the rotation of the Earth can affect the trajecto-ries of long- and medium-range TBMs. In addition,the terrain blocking the line of sight between sensorand threat can affect the detection performance of

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TBMs. These problems are amplified when consideringlow-altitude airborne targets. For some systems, thepresence of rain or clouds in an operational situationcan greatly influence system performance.

Several sources of data in the DoD community de-scribe potential operational situations where TBMDsystems may be deployed. For example, BMDO publishesoperational scenarios that describe campaigns and specif-ic operational situations. For some Navy TBMD systems,Design Reference Missions (DRMs) are used for analysis.These DRMs are typically tailored to the acquisitioncommunity and stress specific system requirements. BothBMDO and DRM products provide descriptions of theoperational situation, friendly assets that require defense,friendly forces available in theater, and hostile forces andtheir attacks on friendly assets and forces.

One-on-one analysis results are often used to deter-mine TBMD system performance in operational situa-tions. In the simplest example, defended or operatingareas are overlaid on a map of the region correspondingto the operational situation. In some cases, performancethat appears significant in one-on-one or many-on-oneanalysis can be less significant when considered oper-ationally. An example is a large ship operating area thatis mostly over land, or as shown in Fig. 3, a largedefended area that contains only a portion over land.

Force-on-force analysis is the primary user of oper-ational situations. Many examples of TBMD force-on-force operational analysis exist. The BMDO CapstoneCost and Operational Effectiveness Analyses (COEA)Phases I and II and the Navy TBMD COEAs Phases

Figure 3. One-on-one defended areas applied to an operational situation.

Area defendable byship from entire

launch area

Defended arearelevant to operational

situation

Ship operating restrictions,e.g., water depth

Launcharea

AssetsAssets

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I and II both made significant use of force-on-forceoperational analysis. APL participated in Navy TBMDCOEAs by providing one-on-one, many-on-one, andforce-on-force operational analysis support. BMDO andthe Joint Theater and Missile Defense communitiescontinue to perform operational analyses of JointTBMD systems.

APL’s ROLE IN TBMD ANALYSISThe following discussion describes specific TBMD

analyses performed by APL to support the developmentand interoperability of Navy and Joint TBMD systems.

Navy Area Defense Operational AnalysisThe Navy Area Defense (NAD) TBMD system is

designed to defend inland and coastal assets fromTBMs. One requirement of the system is to defend aspecified distance inland from the coast. To evaluatethe inland coverage of the NAD system, the resultsof one-on-one and NAD system performance datawere input into EADSIM. Of primary interest herewas determining which inland assets in each of severaloperational situations could potentially be defendedby a NAD system. Since the extent of the defendedarea depends on the direction and range of the threat,threats from multiple azimuths and ranges were con-sidered. The analysis included the water depth oper-ating restrictions of NAD ships, which affect theirplacement. In many areas, especially those away from

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ports and channels, water depthoperating restrictions require aship to remain some distance fromthe coastline. To determine if aninland asset was defendable from aspecific threat azimuth, the assetwas targeted by a TBM from thatazimuth. EADSIM, using a repre-sentation of threats that the NADsystem could engage, determinedif a ship in any of the allowableship positions could defend thatasset.

The result of this analysis yield-ed an estimate of potential inlandcoverage of the NAD system andindicated which assets might bedefendable by the NAD systemfrom different threat azimuths.These results can be used to evalu-ate the NAD inland coverage per-formance relative to requirementsand to help planners determine theallocation of TBMD systems (e.g.,see Fig. 4).

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Ship operating restrictions,e.g., water depth

Inland areasdefendable from all

launch areas bythese three ships

Launcharea

Launcharea

Launcharea

Assets

Ships

Figure 4. Notional inland coverage of a Navy Air Defense TBMD system.

Joint Force-on-Force AnalysisAPL has participated in the analysis of NAD and

Patriot PAC-3 interoperability. Both systems will bedeployed early in this decade; their defensive capabil-ities may have overlapping TBMD coverage. Not sur-prisingly, interoperability between NAD and Patriotunits is of significant interest.

JMA analyzed the capabilities of NAD and Patriotsystems in situations where their TBMD coverageoverlapped. Their representationsin EADSIM were used to generateJoint defended areas. The analysiswas performed with and withoutcoordination between the two sys-tems. The results quantified the in-dividual and Joint capability of thePAC-3 system with a NAD systemoperating in several locations rel-ative to the PAC-3 firing unit. Inaddition, detection and launchtimes of each unit were deter-mined, and these data assisted inthe analysis of Joint engagementcoordination methodologies.

Navy Theater-WideOperational Analysis

Although most one-on-one anal-yses are performed for single threatsto generate defended or operatingareas, single threat operating areas

A

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can be combined to generate oper-ating areas for multiple threats.In support of Navy Theater-Wide (NTW) analysis, JMA usedEADSIM and system performancedata from the APL Air DefenseSystems Department to representthe NTW Block I system. SeveralDRM operational situations wereanalyzed, and the operating areasfor multiple threats were computedby using a large grid of ship posi-tions and determining the numberof threats that could be defendedagainst from each position.

This analysis methodology wasalso applied to more general launchregions and defended regions asopposed to operational situations.In this case, threats could belaunched from anywhere inside adefined launch region and hit any-where inside a defined defendedregion. A grid of ship positions was

used to determine the operating areas from which anNTW ship could defend the entire defended regionagainst such threats. The results showed the operation-al capabilities of the NTW Block I system design andcan be used to compare operational areas for multiplesystem concepts. Notional results from the NTW BlockI operating area analysis are shown in Fig. 5. Theshaded region is the operating area in which an NTWBlock I ship can operate and defend all inland assets

Figure 5. Notional NTW operating area.

Launcharea

Launcharea

Launcharea

Ship operating area todefend all assets from

launch areas

ssets

Ship operating restrictions,e.g., water depth

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TBMD ANALYSES

from all three launch areas. Normally, more inlandassets or more launch areas will decrease the effectiveoperating area of the system.

APL also played a key part in producing the SystemRequirements Document (SRD) for the NTW Block Isystem. For example, one area of investigation was theBattle Management Command, Control, Communica-tions, Computers, and Intelligence (BMC4I) engage-ment coordination trade study. The goal here was todetermine BMC4I requirements for the NTW Block ISRD. JMA participated in the study by analyzing en-gagement coordination options in an NTW DRM op-erational situation.

The NTW Block I system was represented in EAD-SIM as was the operational situation employed in theanalysis. A simplified communications link model thatassumed constant message delay times was used. Sen-sitivity analysis on the delay time was performed todetermine the effects on the performance of multiplesystems. Engagement coordination options consideredwere (1) no coordination, and (2) two proposed coor-dination options (coordination Methods A and B inFig. 6b). Each option used the engagement coordina-tion method in EADSIM, which provides only anapproximation to the actual candidate options. Eachoption was run with at least six different message delaytimes and six different values of an important combatsystem parameter, i.e., the maximum number of targetsengageable simultaneously by a ship. Scenarios wererun with 100 Monte Carlo iterations. The analysis

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included the ability of the platforms to accept link dataand use cues to acquire targets earlier than each couldusing only ownship sensors. The results showed thebenefits of coordinating engagements when TBMD re-sources were limited. A depiction of the type of oper-ational situation and the notional results from theNTW Block I engagement coordination analysis areshown in Fig. 6. The results showed that performanceincreases as each ship can engage more targets simul-taneously. In addition, either of the two proposed typesof coordination provided significant increases in perfor-mance over the no coordination option. This increaseoccurs because when a single ship has a limited numberof simultaneous engagements, over-engagement of tar-gets by one or more ships may result in unengagedtargets.

CONCLUSIONAnalysis of TBMD systems at APL is supporting the

development of a Joint TBMD architecture that willprovide robust and effective protection against TBMsinto the future. The Joint Warfare Analysis Departmentcontributes to Navy and Joint TBMD efforts with op-erational analyses of current and emerging Joint TBMDsystems. There are many challenges ahead in JointTBMD, especially in the area of interoperability. Force-on-force operational analysis will continue to play amajor part in defining the requirements and evaluatingthe operational performance of these Joint systems.

Figure 6. The NTW Block I engagement coordination analysis: (a) simplified scenario and (b) notional results.

Communicationand coordination

Num

ber

of T

BM

s en

gage

able

by th

e fo

rce

No coordinationCoordination Method ACoordination Method B

Number of TBMs engageablesimultaneously by a single ship

Launcharea

Launcharea

Launcharea

Assets

(b)(a)

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W. J. PAVALKO, K. R. CHEVLI, AND M. F. MONIUS

THE AUTHORS

WAYNE J. PAVALKO received B.A. and M.S. degrees in mathematics fromHiram College in 1991 and Purdue University in 1993, respectively. Sincejoining APL in 1994, he has been an analyst in the Joint Mission Analysis Groupof the Joint Warfare Analysis Department. Mr. Pavalko has expertise in NavyTBMD force-on-force and operational analysis as well as modeling andsimulation. In addition to working at APL, he is also a part-time instructor inmathematics at Howard Community College. He is a member of the MilitaryOperations Research Society. His e-mail address is wayne.pavalko@jhuapl.edu.

KANAYA R. CHEVLI received a B.S. degree in mathematics with a secondmajor in physics from the University of North Texas in 1992 and an M.S. degreein physics from the University of Alabama at Huntsville in 1995. He worked asan Operations Research Analyst at the U.S. Army Missile Command until 1997and then joined APL as an analyst in the Joint Mission Analysis Group of theJoint Warfare Analysis Department. Mr. Chevli has expertise in Navy TBMDanalysis and modeling and simulation. He is a member of the Military OperationsResearch Society. His e-mail address is kanaya.chevli@jhuapl.edu.

MICHAEL F. MONIUS earned a B.S. degree in mathematical sciences fromLoyola College of Maryland in 1995 and an M.S.E. degree in mathematicalsciences from The Johns Hopkins University in 1997. His principal areas of studywere discrete mathematics and algorithm design and analysis. He joined the JointMission Analysis Group of the Joint Warfare Analysis Department in June 1997,where he is now an analyst. Mr. Monius has expertise in TBMD modeling andsimulation, and operational analysis and force effectiveness. His e-mail address ismichael.monius@jhuapl.edu.

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