A Comparative Evaluation of Personnel In Cap a Citation Methodologies

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19th International Symposium of Ballistics, 7–11 May 2001, Interlaken, Switzerland

A COMPARATIVE EVALUATION OF PERSONNEL INCAPACITATION METHODOLOGIES

G.E. Romanczuk1, E.G. Davis2 , E.W. Crow1 and D.N. Neades2

1 U.S. Army Aviation & Missile Command, AMSAM-RD-SS-AA, Redstone Arsenal, AL 35899, USA

2 U.S. Army Research Laboratory, AMSRL-SL-BE, Aberdeen Proving Ground, MD 21005, USA

INTRODUCTION

Throughout the history of man, there has been a continuing struggle to understand andharness or retard the ability of ballistic objects to cause harm, kill, or incapacitate. Anyitem having sufficient kinetic energy can cause insult or injury to a person. This paper willfocus on injury that is caused by ballistic objects or fragment that perforate or penetrateinto a person. This paper will not look at injuries caused by large objects moving slowlyor other blunt traumas, however, new tools to add these effects into the calculation of in-capacitation will be discussed. As late as the early 1980’s, a common criterion was refe-renced in regard to the definition of a “hazardous fragment”. The definition included a le-vel of kinetic energy that the fragment must possess in order to be “hazardous”. This limitwas set at 58 foot-pounds and attributed to H. Rohne.[1] This estimate of the amount ofkinetic energy required to make a fragment hazardous or lethal neglects to link the energy

Currently, there is a renewed interest in calculating Probability of Incapacita-tion, Pi, for use in combat soldier vulnerability/lethality (V/L) studies. P(I/H)or more correctly E(I/H), expected value of incapacitation, has been computedhistorically utilizing a wide variety of methods This paper will present an over-view of several currently used and newly developed methodologies utilized toestimate soldier probability of incapacitation level (given a hit) resulting from aballistic projectile penetrating injury. Incapacitation modeling methods pres-ented include the Sperrazza-Kokinakis approach, the Ballistic Dose Model, theComputerMan Model, and the newly developed Operational Requirement-ba-sed Casualty Assessment (ORCA) Model. Methodologies and approaches willbe compared and contrasted, as appropriate, and model user’s inputs and out-puts will be illustrated. Additionally, IncapMan, a newly developed analysistool, that outputs estimates from several Incapacitation methods is presented.IncapMan will serve as a point of departure for the current discussions of whichmethodology should be utilized to analyze and evaluate Military Operations inUrban Terrain (MOUT) environments and which methodology should be utili-zed and incorporated into current component level vulnerability tools.

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to a specific impact point on the body. Neades and Rudolph trace the early works ofRohne and latter works of Sterne and Dziemian [2] and conclude, “Indeed, penetratinginjury research shows that lethal injuries can occur at impact kinetic energy levels signifi-cantly less than 58 ft-lbs. Without giving additional consideration to other parameterssuch as missile shape, size, mass, and possibly impact location, energy based hazard as-sessments can be misleading.” This statement is also true for weapons systems antiper-sonnel effects analysis.

The model methodologies described inthis paper, while representing different ap-proaches, often have their underpinningson the same, or nearly the same, underlyinglarge set of experimental data. Figure 1, il-lustrates the use of 20% (NATO standard)ordinance gelatin in a long block as simu-lant for human tissue in small arms ballistictesting. It is important to understand the as-sumptions and definitions in each model.Over the years, casual reference has caused an obfuscation of the underlying limitationsand definitions inherent in these engineering models. Indeed, the reader should be awareof exactly how each model arrives at a “Probability”. Contemporary U.S. vulnerabilityanalysts prefer E(I/H) to specifically acknowledge that the values computed are expectedvalues and not statistical probabilities.

The following sections will describe the incapacitation modeling methods of interest,specifically the Sperrazza-Kokinakis approach, the Ballistic Dose Model, the Computer-Man Model, and the newly developed ORCA Model. It is not intended to criticize or dis-credit any of the particular methods, but to assist in furthering understanding of themodels, all in one paper. It is important for vulnerability and survivability analysts tounderstand the basic assumptions of each model to assure reasonable or appropriate ap-plications of these models.

INCAPACITATION METHODOLOGIES

Sperrazza-Kokinakis – MV3/2 Model

In 1965, William Kokinakis and Joseph Sperrazza published U.S. Army Ballistic Re-search Laboratory Report Number BRL-1269, which describes their methodology forestimating soldier incapacitation. [4] The Kokinakis and Sperrazza methodology has beenthe most commonly used method in past works and it is often cited as the personnel inca-pacitation method source. This report, as well as other documents that are superseded byBRL Report No. 1269, establish the coefficients, and the model by which an estimate of“probability of incapacitation, Pi/h or Phk” can be calculated. This term and the definitionof incapacitation that is established in BRL 1269 is an important element in the next mo-del, Ballistic Dose, and will be visited in the discussion in the next section.

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Vulnerability Modeling & Wound Ballistics

Figure 1 – Wound track in simulated tissue[3].

(1)

The dependence of Phk, (Pi/h) established in BRL Report 1269, on weight (m) andstriking velocity (Vo) for steel fragments was fitted by equation. (1) The coefficients fora, b, and n were derived for four combat tactical roles (i.e., assault, defense, reserve, andsupply) and six post wounding times (e.g., 30 sec., 5 min., 30 min., 12 hrs., 24 hrs., and 5days). The application of these roles can be somewhat arbitrary and, in general, assault isutilized.

Also, included were tables that transformed the data from a nude soldier to a soldierwith helmet and winter type clothing. This is an important fact in regards to implementa-tion of this methodology in V/L codes, the a,b,& n’s should be checked to determine ifthey are from the nude soldier or the velocity retarded winter clothing coefficients. Also,unpublished modifications that expand the mathematical coefficients use beyond thoselisted in BRL Report 1269 have been found coded have been developed and coded intocommon V/L tools. While the methodology is the same, the Phk value computed mayvary. In fact, the 3/2 exponent is originally introduced as a value β which is set to 3/2 fromthe analysis of the whole body and assumed to be correct for each body part.

Figure 2 shows a typical plot of the data for one role and post wounding time. Variousvalues of Pi have been calculated for a range of velocities and a variety of masses. Thesecurves show the general form that the Sperrazza-Kokinakis method will produce.

In developing the relationship and cor-relations found above, Sperrazza and Ko-kinakis related specific wound class infor-mation to task performance of the soldier,which in this case was “arbitrarily relatedto behavior of the limbs.” [4] In order to li-mit errors induced by the subjective medi-cal evaluation terminology only the anato-mical component which yields the highestincapacitation potential was utilized.

Kokinakis and Sperrazza acknowled-ged that the value computed, Phk, is in factan average level of incapacitation and not atrue probability. Also, they assumed that

the equation, which fit the data for the body as a whole, could be utilized to analyze themajor body regions described in the methodology (i.e., entire body, head&neck, thorax,abdomen, pelvis, arms, and legs).

Ballistic Dose

The concept of Ballistic Dose and its complete theoretical foundation can be found ina current Army Research Laboratory report. [5] This intriguing work attempts to providea methodology which can provide an incapacitation or survival probability for situations

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A Comparative Evaluation of Personnel Incapacitation Methodologies

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Figure 2 – Sample S-K data.

when precise anatomical impact location is not known or is not relevant. In essence, themethodology utilizes the ComputerMan wound ballistics model, described in the nextsection, as a virtual experiment. If you assume the correctness of the answers from Com-puterMan and it’s methodology, then repeated “tests” can be performed against differentbody sections. After the “tests” are completed an equation can be formulated based uponthe variables thought to influence Pi/h. Using this concept and multiple regression it ispossible to create a formula for a “ballistic dose” that is dependent on mass velocity, andthe number of impacts. Equation 2 shows the general form of the overall relation andEquation 3 show the formulation for the ballistic dose as a function of mass, velocity andnumber of impacts.

(2)

(3)

Figures 3 and 4 illustrate a typical set of curves from the ballistic dose methodology.Figure 3 is a plot of a single hit of the masses and velocity indicated on the abdomen. Fi-gure 4 illustrates the change when the number of hits is incremented by one. Similar to theSperrazza-Kokinakis generalized methodology, the Ballistic Dose Model is a generalizedapproach that summarizes the results obtained from the discreet event ComputerManwound ballistics model.

Figure 3 – B. Dose for one impact. Figure 4 – B. Dose for two impacts.

ComputerMan

ComputerMan, originally developed byV. R. Clare and colleagues [6] of the“Wound Ballistics” Division, U.S. ArmyChemical Systems Laboratory, is an auto-mated “wound ballistics” methodology topredict biomechanical degradation to per-sonnel who suffer penetrating injuries dueto fragment impacts. Single or multiple

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Figure 5 – The ComputerMan GUI.

fragments of different mass, velocity, shape factor, and density can cause injuries. De-gradation in ComputerMan is determined along wound paths by computing depth of pe-netration and hole size created and estimating its effect on limb (arms and legs) dysfunction.

A major feature of the ComputerMan methodology is the computerized whole bodyAnatomy of a standing man. This data is represented in 5 mm x 5 mm cells and 12 mmand 26 mm cross sections. The Anatomy data was primarily based upon Eycleshymer andSchoemaker [7] 1911 cross sectional anatomy. In 1994, numerous computer-coding en-hancements were incorporated into the ComputerMan Model by Saucier and Kash. [7]Expanding the ComputerMan anatomical description to 290 different tissue types wasjust one of the numerous enhancements. In contrast to the two previous methodologies,ComputerMan is intended to be a high-resolution simulation of the results of a particularwounding event. Wounding events can then be evaluated to determine incapacitation orbiomechanical degradation or predict survival probability. Evaluations can be obtainedusing the code or developed with additional tools that are included in the ComputerMansystem. Figure 5 shows the main GUI for ComputerMan. The crouching man body pos-ture is shown. User inputs for mass, velocity, shape factor, and density are required to de-fine the fragment. The analyst/user defines the projectile trajectory wound path via leftand right mouse input on the graphical figure. Figure 6, shows output for a typical Com-puterMan test case. This output shows that for the theoreti-cal combat assault role this particular wound does not havean effect until after 5 minutes after the wound. Therefore,the incapacitation level would be set at 0 for the five-mi-nute assault role. This value is set using the concept of limbdysfunction. There are three potential states for each limbin this method. N is no effect on limb, F is Loss of Fine mus-cular coordination or weakness, and T is Total loss of limbfunction. These states are used to determine 81 possiblecombinations for the four limbs. This value ranges between0 and 100 by multiples of 25 and it is a mathematical com-bination value that is output by the ComputerMan model asa level of incapacitation.

PiMan

Mr. Chris Pitts and the primary author, while working atthe Research Institute at the University of Alabama inHuntsville, created the PiMan tool. It was a first attempt tocalculate the methodologies being discussed in one code.PiMan was coded for SGI’s & Windows PC’s with the Win-dows versions using the MFC class libraries. PiMan worksmuch the same way as the ComputerMan GUI versionbased on a single shotline derived from user interaction. Itwas found during it’s use that to compare all three metho-dologies, a multiple impact pattern was required so that

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Figure 6 – ComputerManoutput.

Figure 6 – PiMan output di-alog.

averages over random fragment paths could be used and give a true comparison. [8] Fi-gure 7 shows the PiMan interface.

IncapMan

This tool builds on the PiMan work andwill serve as the basis for integration of allmethods into the 3DPimms personnel inca-pacitation suite. It is coded in Python anduses the Prospect toolkit from Envisage,Inc. In support of the Integrated CasualtyEstimation Methodology (ICEM) new re-presentations of men in several postures were created from the bounding box informationin ComputerMan. The new models use Truncated General Cones (TGC’s) to enclose theAnatomy information described above. It is this information and model that is critical totie into ComputerMan or Orca and get the correct Incapacitation value. These new TGCmen allow an obliquity calculation for fabric armor models to be conducted. IncapManwill serve as a method to explore multiple hits on multiple people in vehicles hit by spallor on open terrain from bursting munitions. Figure 8 shows the user interface with acrouching TGC man.

The Operational Requirement-based Casualty Assessment (ORCA)Model

To address known limitations, shortfalls, and lack of a comprehensive stand-ardized operational casualty assessmentmethodology, a new methodology has beendeveloped for tri-service use that allowsthe assessment of soldier performance fol-lowing weapon induced injury. This newmethodology is embodied in the Operatio-nal Requirement-based Casualty Assess-ment (ORCA) Model. [9] ORCA develop-ment was initiated in 1993 and was jointlysponsored by the U.S. Army Research La-boratory, the Joint Technical Coordinating

Group for Munitions Effectiveness and Aircraft Survivability (JTCG/ME&AS), and theU.S. Office of Secretary of Defense (OSD). Presently, the ORCA Model is undergoingvalidation and verification (V&V) for use in various systems vulnerability modeling en-vironments.

The ORCA Model permits casualty assessments in a consistent manner across virtu-ally all types of military platforms, jobs, and weapon-induced threats. That is, unlike

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Figure 8 – The IncapMan environment.

Figure 9 – ORCA overview.

Sperrazza-Kokinakis, Ballistic-Dose, andthe ComputerMan Models, which are limi-ted to casualty assessments related to frag-ments only, the ORCA Model permits ca-sualty assessment across the spectrum ofpotential battlefield threats, including frag-ments, bullets, flechettes, blast, burn/ther-mal, toxic gases, and laser insults. Includedin the ORCA Modeling Methodology, in-sults to injuries are characterized, as are in-juries to impairments, and finally impair-ments to soldier operational performancedegradation, referred to as operational ca-sualties. Figures 9 & 10 show an overview and the evolution of the ORCA methodology,respectively.

Unlike the ComputerMan Model which estimates military task performance degrada-tion based on non-specifically defined limb requirements, ORCA characterizes the inju-rious effect on 24 explicitly defined elemental capabilities related to vision, auditory,mental/cognitive, vocal, physical, and endurance functioning. Analysis can be conductedfor one or more simultaneous or sequential occurring events, and for one or more battle-field threat types. Service member jobs are characterized into tasks and sub-tasks, whichin turn have been explicitly characterized by using the same 24 elemental capability vec-tors, which are used for characterizing the initial injuries. Additionally, ORCA providesestimates of soldier survivability via two Abbreviated Injury Scale-based[10] injury seve-rity summary scores, namely the Injury Severity Score (ISS) [11] and the Anatomic Pro-file (AP) [12]. ORCA or ORCA modules/functions/libraries are presently being evaluatedand incorporated into larger Army vulnerability and survivability assessment computercodes.

3DPIMMS AND FUTURE PERSONNEL TOOLS

A methodology has been written aboutin previous publications [13] that creates asimulation to evaluate MOUT weaponswith a call to ComputerMan for determina-tion of incapacitation. This methodology(3DPimms) is currently approved for eva-luations of Multi-Purpose Individual Mu-nition/Short Range Assault Weapon(MPIM/SRAW) versus bunkers androoms. Additional, current AMCOM workinvolves implementing a process to create

the inputs for battlefield blast insults that will allow a link to the ORCA blastmodules/functions. Also, in the future, it is planned that the ORCA functions/libraries for

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Figure 11 – 3DPimms methodology.

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Figure 10 – Evolution to ORCA.

fragmenting injury calculations will replace the ComputerMan functions when these be-come available. With the same approach and using available raytrace methods inside ofVirtual Reality toolkits, personnel lethality and survivability can be extended to all man-ner of virtual prototypes. This includes studies for up armoring or designing new body ar-mor, or dismounted infantry distributed simulation environments. Figure 11, shows a vi-sualization of a faceted man with impact points established inside one such package. TheProspectV2 environment from Envisage, Inc. (Huntsville, AL) has a suitable raytrace tooland is designed for real-time visual simulation. Currently, a ray or rays can impact repre-sentations of soldiers modeled in the ComputerMan coordinate system. These impactpoints can be used as input to a casualty analysis directly using ComputerMan or ORCAlibraries. This ability and updated geometry should lead to new capabilities for futurecombat casualty codes as they transition to this type of detailed wound ballistics integra-ted approach.

CONCLUSIONS

This paper has explored the various methodologies that are available to estimate andcompute soldier incapacitation from penetrating injuries. The traditional generalized ap-proach; Sperrazza-Kokinakis has been examined and compared to the more recent metho-dology that yields an incapacitation metric average per anatomical body region. Both ofthese methodologies have been examined with regard to the discreet event approaches,namely the ComputerMan and ORCA Models. ORCA extends the ComputerMan ap-proach for penetrating injuries to look at the total effect of the wound on the elementalcapability vector of a person attempting to perform a combat operational function insteadof four body limbs. Hopefully, as new requirements are written for weapons systems thatrequire lethality against personnel, the requirements will utilize the expanded definitionsand detail inherent in the ORCA method. This includes incapacitation due to blast andthermal effects. This paper also indicates that viable computational options to the entren-ched method, Sperrazza-Kokinakis, are available in codes utilizing ORCA/Computer-Man links when detailed information about the specific injury locations is known.

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REFERENCES1. Neades, D.N. and R. R. Rudolph, “An Examination of Injury Criteria for Potential Applications to Explo-

sive Safety Studies, ADP004 883/XAG, August 1984.2. Sterne, T.E. and A.J. Dziemian, “Provisional Probabilities of Incapacitation by a Caliber 0.30 Rifle-Bullet,

Ball M-2”, BRL-MR 949, U.S. Army Ballistic Research Laboratory, APG, MD, December 1955.3. U.S. Army ARL Web Page, http://web.arl.mil/services/SL-Exprmnt.html, Courtesy of DERA, U.K.4. W. Kokinakis and J. Sperrazza, “Criteria for Incapacitating Soldiers with Fragments and Flechettes.” BRL

Report No. 1269, January 1965.5. R. Saucier and Ada W.D. Gilman, “The Concept of Ballistic Dose and Its Use as a Predictor of Personnel In-

capacitation and Survivability”, ARL-TR-1242, December 1996.6. Clare, V.R., Ashman, W., Broome, P., Jameson, J., Lewis, J., Merkler, J., Mickiewicz, A., Sacco, W., Sturdi-

van, L., Lamb, D., Sylvanus, F., “The ARRADCOM ComputerMan: An Automated Approach to WoundBallistics.” ARCSL-TR-80021, U.S. Army Chemical Systems Laboratory, Aberdeen Proving Ground, MD,November 1980.

7. Saucier, R., Kash, H.M., III, “ComputerMan Model Description”, U.S. Army Research Laboratory Techni-cal Report Number ARL-TR-500. U.S. Army Research Laboratory, APG, MD, August 1994.

8. Romanczuk, G. and C.Pitts, “A Comparative Analysis of the Calculation of Probability of IncapacitationFound in Sperrazza-Kokinakis, Ballistic Dose, and ComputerMan/ORCA”, Advanced Simulation Techno-logies Conference,Washington, D.C., April 16–20, 2000.

9. Neades, D.N., Klopcic, J.T., Davis, E.G., “New Methodology for the Assessment of Battlefield Insults andInjuries on the Performance of Army, Navy, and Air Force Military Tasks”, In Proceedings of the North At-lantic Treaty Organization Research and Technology Organization (NATO/RTO), Specialist’s Meeting ofthe RTO Human Factors and Medicine Panel, “Models for Aircrew Safety Assessment: Uses, Limitations,and Requirements – Held at Wright-Patterson Air Force Base, Ohio, USA, 26–28 October 1998”, August1999.

10. Association for the Advancement of Automotive Medicine (AAAM), “The Abbreviated Injury Scale 1985 –Revision (AIS-85)”, Committee on Injury Scaling, Des Plaines, IL, 1985.

11. Baker, S.P., O’Neill, B., Haddon, W., Long, W.B., “The Injury Severity Score: A Method for Describing Pa-tients With Multiple Injuries and Evaluating Emergency Care”, Journal of Trauma, 14(3), pp. 187–196,1974.

12. Copes, W.S., Champion, H.R., Sacco, W.J., Lawnick, M.M., “Progress in Characterizing AnatomicTrauma”, Journal of Trauma, 30(1), pp. 1200–1207, 1990.

13. Romanczuk, G. et. al., “3DPIMMS – High Detail Effectiveness Calculation From Collected Three-Dimen-sional Fragment Dispersion Data”, First Biennial National Forum on Weapon System Effectiveness, EglinAir Force Base, April 6–8, 1999.

** The Army Research Laboratory created ComputerMan, ORCA, Ballistic Dose, and BRL-CAD

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Documents

A Comparative Evaluation of Personnel In Cap a Citation Methodologies