INTERCEPTION DEBRIS – FROM INITIALS TO FULL SIGNATURE

WALES, Ltd. MAY 2010

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UNCLASSIFIED Interception Debris- from Initials to Full Signature- 1/16

INTERCEPTION DEBRIS – FROM INITIALS TO FULL SIGNATURE

Approved for Public Release 10-MDA-5452 (30 APR 10)

INTERCEPTION DEBRIS –

FROM INITIALS TO FULL SIGNATURE

Presented By:

Mr. J. Yifat

WALES, Ltd., Israel

1st Annual Israel Multinational BMD Conference & Exhibition


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PRESENTATION TOPICS

• Introduction

• Debris Model Overview

• Calculation of Debris Parameters Distributions

• Example of Debris Model Result

• Summary


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INTRODUCTION

• Pre and post intercept debris are becoming an issue of main concern since they might have severe impact on multiple aspects of BMD

• Debris clouds are generated in various events


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INTRODUCTION (Cont.)• In order to assess the impact of debris on BMD elements and

analyze possible solutions, a thorough understanding of debris cloud characteristics is required:

– Debris physical parameters distributions according to the specific debris generating event

– Debris cloud dynamics

– Sensor sky picture in presence of the debris• Debris physics is very complex with many uncertainties and is

usually referred to as an “order of magnitude” problem


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INTRODUCTION (Cont.)

• The goal of this study was to develop an integrated debris model that simulates debris clouds for various debris generating events and scenarios

• A new, comprehensive debris model was developed, based on data from open literature

• The model provides order of magnitude estimations of debris cloud characteristics and distributions that fit open source empirical data and hydrocode simulations


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DEBRIS MODEL OVERVIEW

• The model currently incorporates the following sub-models (each of these models or combination of them is used in its relevant debris generating event):– NASA’s EVOLVE model: based on various empirical data of

satellites breakups, interceptions, explosions and hypervelocity impact experiments (Solwind, SOCIT, etc.)

– NASA’s FASTT model: based on physical conservation equations and empirical data of satellite breakups

– Mott & Gurney equations for distributions of explosion debris– WALES Debris RCS Signature model– Physical Conservation Equations (mass & momentum)


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• The Integrated Debris Model:– Enables quick generation of random realizations of debris

clouds for many debris generating events– Can be updated according to future empirical data (i.e. TBM

interception tests)– Can be used in sensor and architecture studies in order to fully

understand the impact of debris on the various BMD elements and come up with possible algorithms and solutions to the debris problem

DEBRIS MODEL OVERVIEW (Cont.)

HE


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DEBRIS MODEL OVERVIEW (Cont.)

• The new debris model is relevant for most debris generating events

• The model calculates the following physical properties for the entire debris cloud (later used in dynamic simulation):– Mass– Diameter (defined as fragment’s longest dimension)– Δ Velocity– Ballistic Coefficient– RCS Distribution


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CC LCLN

n

iiiiMA MAfND

1/ /,,

CC LSLN Diameter

Distribution

Collision Explosion

Area to MassDistribution

MassDistribution

Δ VelocityDistribution vfND v ,,

Ballistic CoefficientDistribution

BCfNDBC ,,

C

C

LLN

n larger thaor equaldiameter with fragments ofNumber

ondistributi NormaldebrisBooster / RVfor different and

, of functions are ,,

N

LiCiii

debrisBooster / RVfor different and

,/ of functions are , MA

ondistributi Normal of functions are ,

Nm

Mott Equations

EVOLVE Model

Gurney Equations

FASTT Model

RCS Model

RCS Signature Area Projected Average Avg A

All distributionsfit available

empirical data

AvgMedRCS AfRCSSwerlingD

MA

C

DLM

/

DEBRIS DISTRIBUTIONS CALCULATION


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• In case of debris caused by explosion (HE initiation), the fragments mass distribution is calibrated such that the number of small fragments (belongs mostly to the metal surrounding the HE) would agree with Mott equations, which are verified according to numerous HE terrestrial experiments:

EXPLOSION DEBRIS MASS DISTRIBUTION CALCULATION

m

eMCmN

DtDtG 1

thicknessmetaldiameter Explosiveconstant Explosivemass case Total

an greater th mass with fragments ofnumber Total:

tDBM

mmNWhere

m

f (m) MottEVOLVE

EVOLVE - Calibrated


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DEBRIS Δ VELOCITY DISTRIBUTION CALCULATION

• In the cases of explosions, the velocities of fragments from the areas surrounding the HE (most of the small fragments) are derived from the Gurney equations for explosion fragmentations:

• NASA’s empirical model is used for the remaining fragments• A transition function is used to integrate both models

EVOLVE

Gurney

HE

212, C

MEV CylPeak


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DEBRIS Δ VELOCITY DISTRIBUTION CALCULATION (Cont.)

Center of Mass Velocity

• Velocities created by the model (stochastic) are added to the center of mass velocity (target and interceptor)

• On average, smaller fragments receive higher added velocities and show much wider spread than larger and heavier fragments

• To guarantee conservation of momentum, a random unified distribution over a spherical surface (Isotropic) was used for velocities directions


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• RCS assessment of debris was performed using a set of representative debris shapes and sizes

• Swerling distribution fitted for each examined shape and size• Average projected area defines RCS distribution parameters for

each fragment in integrated debris model

RCS DISTRIBUTION CALCULATION

Radar A Radar B


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EXAMPLE OF MODEL RESULT – DEBRIS CLOUD SIMULATION BASED ON GENERIC TARGET AND INTERCEPTOR

Generic HE RV, HTK Interception


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INSIGHTS FROM MODEL RESULTS

• Fragments Mass, Length and Velocity show spread up to an order of magnitude - fits empirical findings

• A few large and heavy fragments are produced

• Interceptions that involve HE explosions produce less debris, since part of RV mass is HE which is converted to energy and gas

• Hypervelocity collisions (HTK) produce fragments with higher velocities than explosions (confirmed in ground experiments)


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SUMMARY

• Various debris models, based on numerous empirical findings and physical equations were updated, calibrated and gathered under one integrated debris model

• The model can be used to produce reasonable realizations of debris clouds from various debris generating scenarios

• Debris distributions produced by the model agree with empirical data, hydrocode simulations and classic fragmentation models

• An example of debris cloud realization for a generic interception event was presented

• Debris model shows great potential for contributing to BMD system level analyses

INTERCEPTION DEBRIS – FROM INITIALS TO FULL SIGNATURE

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