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The Operational Requirement-based Casualty Assessment (ORCA) Model David N. Neades

US. Army Research Laboratay

ABSTRACT

New methodology is presented which allows the assessment of soldier performance following weapon- induced injury. This methodology, embodied in the ORCA model, represents the product of a major U.S. program to establish new, standardized procedures for assessing munition effectiveness and target vulnera- bility. The model is applicable to a wide range of battlefield insults which can impinge upon personnel in ground, air, and sea platforms.

1. Introduction

In 1%5, Kokinakis and Sperrazza published curves of probability of incapacitation, given a hit, or P o , correlated to fragment mass and striking velocity raised to the 3/2 power (M V 3n).1 In the years since, these cumes have been used to compute P(VH) as a common measure of weapon effectiveness throughout a wide segment of the operational research community. Although these data apply strictly to situations involving fragment impacts against infantry soldiers, they are often mis-applied to personnel in non-infantry roles as well, due to the lack of platform specific criteria. In other segments of the analysis community, the vulnerability of on-board crew personnel and their contribution to the vulnerability of the weapon system is not explicitly computed. In general, comparable methodology to deal with the effects of other damage mechanisms such as blast overpressure, thermal, etc.. on either land, air or sea platforms has been inadequate or lacking altogether. The lack of a standard, comprehensive methodology has prevented, among other things, direct comparisons of operational casualty estimates across service or threat mecha- nism lines.

2. Background

The present work has its origins in a series of casualty workshops? sponsored by the U.S. Office of the Secretary of Defense (OSD), which identified many of the limitations and shortfalls cited above, and the need for a comprehensive casualty assessment methodology. That need led eventually to the formation of the Crew Casualty Working Group (CCWG) which, in 1992. became part of the Joint Technical Coordinat- ing Group for Munition Effects (JTCGFIE). Shortly thereafter, the essential common interest of the JTCG/AS (Aircraft Survivability) in the Same crew casualty issues was recognized The CCWG at that point became a joint JTCG/ME and JTCG/AS working p u p .

2.1 The Crew Casualty Working Group

The CCWG is truly a ui-service organization and is headed by an executive committee consisting of a representative fiom each of the Army, Navy, Air Force, OSD, JTCG/ME and JTCG/AS. The executive committee is supported by technical inputs from throughout the personnel vulnerability and human factors community through representatives from the services. other govemment agencies, academia, and industrial groups/contractors.

The primary goals of the CCWG are as follows: a. To develop and publicize a comprehensive, Department of Defense-accredited

1. "Critcrir for Incapaciraling Soldiers Wlth Fragmcnu md Flcche~" . Ballistic Rcwrch Laboratory Report So. 1269. by W h Kdrinllds and JoKph, Spmzu dated January 1965. (UNCLASSIFIED)

"Prauedingr d the Live Fire Test C m Gsualty Assuuneru Workshop Held 18-19 Octobcr 1988 at the Naval Suhnrrine Buc, Gnon. Cocmecticut". s p w d by Dimor. Live Fin Testing. Office d Ihe Director. Dcfaue R e ~ u c h d

2.

Engineering.

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personnel vulnerabiity a s c s " t mabdobw

b ToeaaMishamnrislanwofwortingdednitiorrP

c. Tosupport key pro&& which am tri-scrviaappliibk and needed IO fill i&ntifid widq

d To pss(IIc thaI outpurr of c m casualty pmjecrr canpiuiile with thei l lsesbm

e. Toaiddissemination ofresulu. in panicular, lhmugh JTCG channels

f. whcn appropriate, IO transition IO a sub-group under one. of the permanent Jrrcl WarkingGroups

Ihe remaindex of lhis paper describes the status of work driven by the 6m goal.

3. Amroach

'Ibe foundation of the Operational Rquirement-based Casualty Assessment (ORCA) Model and the underlying CCWG muhodology is a nm laxonany f a the casualty awsnen~ process. The taxonomy has prom IO be most useful, not only for assuring axnplucness and codination of the technical tasks, but also fordeveloping an owall r"gmen1plsn f a tbe work oftheCCWG. As shown in Figure 1. the axonany divides logidly in10 Uuee pats: the determination dtbe injtny tedting f" an insul~, rhe re- sulting impairment of CCMin human elemental capabiities, and the effect of such mpairment on h e per- formance of military job.

ELEM. CAPABILITY REQUIREMENTS IMPAIRMENT

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OPERATIONAL CASUALTY

COMPARE \ _. . ._ . _. . . REWIREMENTS

I WMENTS E M to IMPAIRMENT

Figure 1. Taxonomy for the Casualty Assessment Recess

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The ultimate objective of the process, then, is to determine if an individual would be an Operational Casual- ty as a result of his/her exposure to the insult. An Operational Casualty is defined here as "An impaired in- dividual whose available elemental capabilities are less than those required for successful performance of a

It should be noted at this point, that the scope of the CCWG project is limited to evaluating the resid- ual performance of an individual after a potentially damaging environment has actually impinged upon himjlxr. Thus the degradation of a threat by protective mor, or other ex& factors which may influ- ence the characteristics of the threat prior to its reaching the individual must be taken into account before beginning the CCWG process. It should also be noted that no aaempt has been made to account for any ef- fect that variables such as motivation and fear might have on performance. We are auempting to simulate only the physical effects of injury in order to assess what an individual

specified militarypb".' I

do, not what he would do.

The basic steps involved in this crew casualty assessment process are as follows:

1. Assemble the parameters that quantify an Insult

2. Evaluate the anatomicaYphysiological Injury produced by that Insult

3. Relate that Injury to the attendant Impairment, expressed as a degradation of Elemental Capabilities.

4. Independently, establish the Requirements for satisfactory performance of , a military job, also in terms of Elemental Capabilities.

5 . Compare the mailable (degraded) Elemental Capabilities to the required Elemental Capabilities to determine if the specified injury constitutes an Operational Casualty for an individual in the specified military job.

4. The ORCA Computer Model

The computer code written to carry out these steps is referred to as the ORCA Model. The assess- ment of an operational casualty using the ORCA Model begins by specifying the potentially damaging mechanism, or Insuf t . The Insults which are being addressed in the ORCA model are:

. Blast Overpressure

. Penetration ,

Therm01

Directed Energy

Toxic Substance Inhlation/Contacr

Blunt Trauma

Acceleration'

Biological

4.1 Insult Specification

An Insult is quantified by a set of parameters, Pi which characterizes the damage mechanism in use- ful terms. As an example, for a blast overpressure event, that set might consist of a pressure-time curve and a body orientation with respect to the blast wave. In many cases. ORCA users will have the option of se- lecting from predefined insult characterizations (eg, a wave form, along with a peak pressure and A dura-

3. Other working definitions appear in the Glossary at the end of h i s p"pez

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tion in the case of blast overpressure) or providing their own data. When appropriate, the body can be artic- ulated cx placed into different postures relative to h e Insult For example, a soldier being subjected to frag- ment impacts can be positioned in a standing, seated, crouching, or prone position.

4.2 Injury characterization

ORCA contains state-of-the art algorithms and supporting data to calculate the anatomical damage done to a human body by the Insult In the ORCA code. all injuries are recorded in a standard form via a vector ( A vector) whose elements refer to the state of over 450 body parts that have been defined to consti- tute.& human body. Each element has an associated scale through which the severity of the damage is recorded. Again, with the blast overpressure example, the lungs and ears, being the main organs at risk, are the relevant elements of the A' vector. A numerical value ranging from 1 to 5 is used to indicate the severity of damage to the lung as a result of the blast Insult

The determination of medical casualties is not within the charter of the Crew Casualty Working Group. However, it is essential that, to the point that medical and operational casualty factors are common. ORCA must be consistent with the needs of the medical community. To this end, significant care has been taken to define and record injuries in such a way as to serve future medical analysis needs. In parucular. ORCA determines and keeps track of each injury's Abbreviated Injury Score (AIS), an injury characteriza- tion system common throughout the medical community. for this purpose!

4.3 Elemental Capability Impairment

Significant work has been devoted to correlating the various types and levels of Injury to the Impair- ment of an individual's capabilities. These capabilities are formally recorded via the Elemental Capability Vector. or "ECV" for short The elements of the ECV are representative of the capabilities that humans use to accomplish tasks. Figure 2. is a list of 24 such capabilities contained in the ORCA model.

visual Acuity Visual Color Discrimination visual Field of V i Visual Binocularism

Hearing Threshold -Low Freq Hearing Threshold - Mid Freq Hearing Threshold - High Freq

Somatic Senses Balance Head

Vocal Clarity Vocal Power

Leji Leg Function Right Leg Function Left Arm Function Right Ann Function Lefl Hand Function Righ Hand Function Torso Support Neck Movemen!

Cognitive Mental Processing Endurance (Aerobic) visual Mental Processing Auditory Mental Processing Psychomotor Mental Processing

Figure 2. Elemental Capability Vector.

Each of these elements is quantified by a set of parameters which permits us to consider various lev- els of capability. 'Ihe 24 elements can be grouped into the following general categories:

Visual - Xsion is critical for almost every imaginable task, including battlefield surveillance. driving a tank, or loading weapons.

4. "The Injwy Severity Scorr: A Mahod for DuaiLing Patimu wivith Multiple Injuria and Evaluating Emqcncy Cam." JOWMI ~ ~ T M W W vd 14, pp. 187-196.1974, by S.P. Baker ud B. O'Neill.

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Auctiiory - Hearing is measured in decibels for three threshold frequencies. Crew members likely to need hearing include communication personnel, foot soldiers, and pilots.

Menial - Cognitive, Visual, Auditory, and Psychomotor mental processing refers to the brain respons- es needed to interpret or understand the stimuli received by the senses. The ability to reason and make de- cisions is critical for many tasks in the field.

Vocal - Vocal capability is measured by the amount of vocal power needed and speech intelligibility. The ability to communicate can be important on the battlefield as well as in communication activities.

Physical - physical tasks are broken down by body segment Strength and movement capabilities of the legs, arms, hands, torso, and neck are measured in the ECV. Minor physical tasks such as pushing a button or tuning a knob can be modeled as well as major tasks such as walking, climbing, pushing or pulling. or swimming.

Enduronce - Other capabilities such as endurance, balance and a sense of touch are modeled in the ECV. Endurance will play an important role in determining casualties because many injuries can affect the blood or oxygen supply to the body.

In ORCA, the Elemental Capability vector serves two important functions. First as described above, the ECV is used to quanhfy the capabilities that a particular. possibly wounded individual possesses. In this application, the ECV is referred to by the symbol R. The same vector form is used to quantify the ca- pabilities required m perform specific military tasks or jobs. In this application, the ECV is referred to by the symbol 2. Therefore, it is a straightforward matter to determine whether a wounded individual is capa- ble of performing a particular task or job. ORCA compares his capabilities (x) with the task requirements

4.4 Time Dependence

In the ORCA formulism, an injury is characterized at the time it occurs. However, it is recognized that the effects of an injury may change over time. To capture this effect, ORCA calculates a number of vectors, one for each of six post-wounding times: 30 seconds. 5 minutes, 30 minutes. 1 hour, 24 hours, and 5 days. Each vector is in turn compared to the job requirements to determine job performance, or casualty status over time.

4.5 Task Requirements

As is now clear, an operational casualty is defined with respect to a particular task or job. (A "job" is a group of tasks). Thus, in addition to defining the insult, the task or job of an individual must be input us- ing Military Occupational Specialty (MOS), Navy Enlisted Code (NEC), or Air Force Specialty Code (AF- SC) job description information. These military jobs have been defined by a list of basic physical. cogni- tive and sensory tasks. Each basic task description such as running, carrying. or speaking is described us- ing the elemental capability vector. For instance, a pilot's job contains several tasks such as operating con- trols, reaching above, visual mental processing, communication, and hearing. Each task is described by the ECV and the job will consist of the summation of all the tasks needed by the pilot. ORCA contains a li- brary of tasks and jobs that have been quantified in terms of their elemental capability requirements. In ad- dition, ORCA contains a very friendly user interface to help an ORCA user to describe his own tasks and jobs through common terms and images.

It is recognized that job performance is usually not a "Go-No Go" proposition; rather, most jobs can be performed at various levels of effectiveness. ORCA models this by allowing different levels of require- ments to describe different levels of performance. Standard practice with ORCA is to specify requirements for full performance and the requirements for marginal performance. Again. the user interface helps the us- er specify different levels of effectiveness or select them from the ORCA library.

4.6 Individual Characterization

ORCA allows the user to characterize the individual being studied. Although a SO* percentile indi- vidual is the default condition. the user can specify the initial capabilities of the individual. or randomly se- lect initial capabilities via Monte Carlo draws from distributions of capabilities.

(2).

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5. Current Status of the ORCA Code

Currently, the ORCA code exists in an alpha version which contains the complete structure of the methodology. the blast Insult, portions of the Penetrating Insult, and the initial versions of the uset inter- faces. Recently, the Crew Casualty Worlring Group held workshops which defined the parameters, algo- rithms, and data for the Burn, Radiational Eye Damage, Toxic Gas, and Chemical Insults. Some of these plus the Blast and Penetrating Insults will be implemented into the Beta version of the code, which will be

The entire ORCA project, planned in 1992 as a five year program, is on schedule. Figure 3 is a sum- mary chart which illustrates the excellent progress to date and schedule of remaining activities. Beta vex- sions will be released throughout 1996 as the final Insults are implemented. Configuration management is- sues are also being addressed as are approaches for verification and validation of the entire methodology. For more information, contact the author a t

released in early M 96.

v I;;;' AcclBT Bio

U.S. Army Research Laboratory

Aberdeen Proving Ground, Maryland Al": AMSRL-SL-BS (Mr. Neade~)

2 lOO5-5068

or one of the other members of the Crew Casualty Executive Committee.

Workshops BOP

Interfaces = Linkages

Code

Task Analyses

v a n d v

Configuration Cnlrl

FY94

1 1 2 1 3 1 4

v v Pen ECV

BOP - Blast Overpressure DEW - Directed Energy (Laser) ECV - Elemental Capabilities

4 1 2 3 4

FY07

1 1 2 1 3 1 4

I Alpha Bcta

Acc - Accclcration BT - Blunt Trauma TG - Toxic G a x s

Bio - Biological Pcn - Pcnetration Bum - Thermal Injury

Figure 3. Tuneline for the CCWG Project

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GLOSSARY

1. Activity - An unquantified action, e.g. low lift, ground to a height of 15 inches, from a standing position using both hands.

2. Casualty (Joint Pub 1-02) - Any person who is lost to the organization by reason of having been de- c W dead, wounded, injured, deceased, interned. captured. re4ained. missing. missing in action, belea- guered, besieged or detained.

3. Elemental capability - One of a small number of physical or sensory capacities which enable one to per- form a task element. Currently, the set of elemental capabilities comprises the following: visual acuity, vi- sual color discrimination, visual field of view. visual binocularism, hearing lhreshold - low frequency, hear- ing threshold - mid frequency, hearing threshold - high frequency. somatic senses, balance, cognitive mental processing, visual mental processing, auditory mental processing, psychomotor mend processing, vocal clarity, vocal power, left leg function, right leg function, left arm function, right arm function, left hand function, right hand' function, torso support, headneck movement, endurance (aerobic). Elemental capabil- ities are further defined in physical terms which permit an assessment of the impact of a Standard injury. A standard injury may degrade one or more of an individual's elemental capabilities (eg. right arm func- tion ). If that elemental capability is required to perform some task elements, the individual will have expe- rienced an elemental task impairment.

4. Elemental task impairment - The reduced ability to perform at least some elements which comprise a military job. 5. Incapacitation - The inability to perform, at a level required for combat effectiveness. the physical or mental tasks required of a particular combat role.

6. Injury (Joint Pub 1-02) - A term comprising such conditions as fractures, wounds, sprains, strains, dislo- cations, concussions. and compressions. In addition, it includes conditions resulting from extremes of tem- perature or prolonged exposure. Acute poisonings. except those due to contaminated food, resulting from exposure to a toxic or poisonous substance are also classed as injuries.

7. Insult - The extemal, munition produced, physical agent capable of producing an injury (examples 1-g fragment, 50 kPa, 31caVcm2)

8. Job - The combination of all human performance required for operation and maintenance of one person- nel position in a system, e.g., driver.

9. Medical Casualty - An individual who has experienced an injury which requires evacuation from his/her unit so that medical treatment can be administered.

10. Operational Casualty - An impaired individual whose available Elemental Capabilities are less than those required for successful performance of a specified military job.

11. Physical condition vector, A - Quantified parameters representing human anatomicaVphysiological condition, such as the state of a limb,organ. body system (e.g. circulatory), or other physical entity, placed in a standard, fixed order.

12. Standard injury The anatomical damage and/or physiological response produced by an insult. Stan- dard injuries require a minimum insult dose (threshold) and may change in severity as a function of time af- ter insult. (examples: IO-mm hole in thorax muscle tissue and associated weakness, lung petechia. edema)

13. Task - The composite of related activities (perceptions, decisions. and responses) performed for an im- mediate purpose, e.g., Change a tire.

14. Task Element - The smallest logically and reasonably definable unit of behavior required in completing a task or subtask. e.g. apply counter clockwise torque to the lug nuts with a lug wrench.

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