TARGET SIZE MODELING METHODSESTCP Project Number: 2005 – MM – 07

Model Overview (Figs. 1 through 3)• Impact Dispersion Model – models locations of impacts around given target point for indirect-fire weapons (Fig. 1)

• Fragmentation Model –Predictsdistributionofnumber,mass,andinitialvelocityoffragmentsresultingfromdetonationof

singleround –Predictshorizontalfragmentrangebasedonmass,initialvelocityandinitialangleoffragments(Fig.2) –Randomlydistributesfragmentstomodelfragmentation“footprint”ofthedetonationofasingleround

• Geophysical Model –Modelscapabilityofgeophysicalsensorstodetectsizesanddensitiesoffragmentationpredictedby

fragmentationmodel –Sensorcapabilitiesaffectedbygeophysicalsensortype,platform,andsite-specificbackgroundconditions(geology,

vegetation,etc.) –Sizeandshapeoftargetareatobeusedasinputtosurveydesignwillvarydependingongeophysical

sensorcapability

• Target Sizing Model – combines the three components –Overlaysfragmentationfootprintforsingledetonationonpredictedlocationsofimpacts(Fig.3) –Boundariesofdetectableareasofthetargetdeterminedbycapabilitiesofgeophysicalsystem

BACKGROUND

Target Size Model Objectives• Develop robust, flexible model to predict size and shape of detectable fragmentation distributions from

indirect fire weapons systems

• Provide input to determination of search patterns and transect spacing for preliminary investigations

• Aid in footprint reduction at suspected munitions response sites

Past Year’s Progress• Progressed in the development of the Geophysical Capabilities Component

• Analysis to assess the sensitivity of the model results to key inputs

• Validation of model against first site in progress

GEOPHYSICAL CAPABILITIES COMPONENT

Background• Target Sizing Model predicts size and densities of fragments throughout target area; the model predicts some very small fragments and very low

densities

• Fragment size prediction considerably smaller than UXO or nose/tail pieces that are typically searched for

• Real world application of model requires fragments be detected by common geophysical instruments

• Ultimate size and shape of target area to be used as input to survey design will depend on geophysical capability

Analysis• Literature review and analysis of past studies and experiments (speed and noise evaluations, height tests) to establish baseline understanding of

capability (in progress)

• Detailed analysis of fragments and dig results from 60mm target at Former Camp Wheeler Non-Time Critical Removal Action (completed)

• Field experiments McKinley Range, Redstone Arsenal, Huntsville, AL to collect data over fragment concentrations and transects based on model output (data collection and preliminary analysis complete)

• Compare site-specific data against model outputs simulating sites

Field Experiments (Figs. 4 through 7)• Fragments from 60mm M49A2 mortars from Former Camp Wheeler used

• Preliminary analysis completed (Figs. 4 through 7)

• Results: –“Detectable”numberoffragmentsdependentonindividualfragmentmasses –Lessthan5grams–increaseinnoise –5to20grams–minimumof~30fragments/m2 –20to50grams–minimumof~5fragments/m2 –50to80grams–minimumof~2fragments/m2 –Greaterthan80grams–minimumof~1fragment/m2

MODEL VALIDATIONFormer Camp Wheeler near Macon, GA

Brief History• Formerly Used Defense Site near Macon, GA

• Established in 1917 as training camp for National Guard units (closed in 1919)

• Re-established in late 1940 as an Infantry Replacement Training Center (closed in 1946)

• Approximately 14,000 acres

• 17,000 trainees and 3,000 cadres at height of use

• Contained over 30 ranges, for munitions ranging from 30 cal rifles, machine guns, grenades to 60mm and 81mm mortars

Validation Site at Former Camp Wheeler (Fig 14)• Range R-30, a live 60mm mortar range

• Approx. 340 unexploded 60mm M49A2 and M49A1 recovered during recent removal action

• Recovery depths from surface to 30 inches

• Small number of grenade fuzes also recovered

• Nearly 16,000 lbs of “OE Scrap” (fragments) also recovered

• Weight of recovered fragments recorded for each 50m x 50m work gridValidation Approach• Model the apparent multiple targets based on the locations of the UXO; base number

of rounds on assumed dud rates

• Sum predicted fragment masses over same 50m x 50m grids

• Compare predictions to removal results

SENSITIVITY ANALYSIS

Objectives• Explore the effect of key variables on the Target Sizing

Model

• Determine whether simplifying assumptions can be made for some of the variables

• Determine whether default values can be used for some of the variables

Shape Factor (Fig. 13) (i.e., drag on fragments)• Specifies the area of fragment facing perpendicular

to the direction of flight

• Fragment range increases as shape factor increases; size of target area increases and fragment density decreases (Fig. 13)

• Shape factor of 0.333 is commonly assumed for fragments

• Little data is available on actual fragment shapes or drag coefficients

• Validation of model with actual field data will be used to determine appropriate shape factor

Mark/Mod of Munition (Fig. 8)• Differences in case dimensions can affect size and number of fragments

• Differences in filler type and amount can affect size, number and range of fragments

• Ideally, these effects will be small enough that same size munitions can be grouped together

• Rounds with similar case weights and filler weights could be grouped together

• Filler type of secondary importance

Number of Rounds (Fig. 9)• Analysis integrated with geophysical analysis results

• Ideally, use of this information will allow specification of “Lightly” and “Heavily” used sites

• Tentative identification of three levels of site use: –Lightlyusedsite:onlypartoftargetboxisdetectable. –Moderatelyusedsite:targetboxandmoredistantfragmentsaredetectable,butagapbetweentwoareas –Heavilyusedsite:Continuousdetectablearea

• Effects of VSP “probability of detecting” calculation will have a bearing on final determination of site use levels

Probable Error of Impact (PE) and Angle of Fall of Munition(Figs. 10 through 12)• Variables specified in firing table for a given charge level and range; each weapon system type has multiple

firing tables, one for each charge level; each charge level has PEs and angles of fall for multiple weapon ranges

• Goal of sensitivity analysis of Angle of Fall and Probable Error is to reduce amount of firing table informa-tion required as input to model

• Increased probable errors increase impact dispersion leading to larger, less dense target footprint (Fig. 10)

• Fragment range increases as angle of fall increases, up to ~68º-70º; then range decreases as angle of fall increases (Fig. 11)

• As fragment range increases, target footprint becomes larger and less dense (Fig. 12)

• Variability in figure 12 indicates that it may not be possible to develop a single default for these variables

–Someentryoffiringtabledatawillbenecessary –Researchingchargelevelsrecommendedforeachrangeoffireandonly

enteringrecommendedrangesforeachchargelevelmayprovideawaytolimittherequirednumberofentries

Project Completion Plan• Complete model validation against site data

• Incorporate aerial bombing targets into model (dependent on obtaining impact dispersion data for older aerial bombing systems)

• Complete incorporation of sensitivity analysis and geophysical capability model into the Target Sizing Model

• Document model and model software

Sensitivity Variables• Mark/Mod of Munition

• Number of Rounds

• Angle of Fall of Munition

• Probable Error of Impact (range and deflection)

• Shape Factor (i.e., drag on fragments)

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