Transcript 7051c-Booster HTK Debris Cloud Analysis

UNCLASSIFIED
– FROMBMD
INITIALS
TO FULL&SIGNATURE
st Annual IsraelDEBRIS
1INTERCEPTION
Multinational
Conference
Exhibition
INTERCEPTION DEBRIS –
FROM INITIALS TO FULL SIGNATURE
Presented By:
Mr. J. Yifat
WALES, Ltd., Israel
WALES, Ltd.
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INTERCEPTION DEBRIS – FROM INITIALS TO FULL SIGNATURE
PRESENTATION TOPICS
• Introduction
• Debris Model Overview
• Calculation of Debris Parameters Distributions
• Example of Debris Model Result
• Summary
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INTERCEPTION DEBRIS – FROM INITIALS TO FULL SIGNATURE
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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INTERCEPTION DEBRIS – FROM INITIALS TO FULL SIGNATURE
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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Interception Debris- from Initials to Full Signature-
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INTERCEPTION DEBRIS – FROM INITIALS TO FULL SIGNATURE
DEBRIS MODEL OVERVIEW (Cont.)
• 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
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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INTERCEPTION DEBRIS – FROM INITIALS TO FULL SIGNATURE
DEBRIS DISTRIBUTIONS CALCULATION
Collision
Diameter
Distribution
Area to Mass
Distribution
Mass
Distribution
Explosion
N LC   S  LC
N LC   C  LC

diameterequal or larger than LC
 i , i ,  i are functionsof LC ,
i
n
DA / M   i  N i ,  i , f  A / M 
and differentfor RV / Boosterdebris
N  Normaldistribution
EVOLVE Model
i 1
M
N LC   Number of fragmentswith
FASTT Model

LC
DA / M
Mott Equations
Gurney Equations
RCS Model
Δ Velocity
Distribution
Dv  N , , f v
 ,  are functionsof A / M ,
and differentfor RV / Boosterdebris
Ballistic Coefficient
Distribution
RCS Signature
WALES, Ltd.
DBC  N , , f BC
 ,  are functionsof m
N  Normaldistribution
DRCS  SwerlingRCSMed  f AAvg 
All distributions
fit available
empirical data
AAvg  AverageProjectedArea
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INTERCEPTION DEBRIS – FROM INITIALS TO FULL SIGNATURE
EXPLOSION DEBRIS MASS DISTRIBUTION CALCULATION
• 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:
N m   C
M

e
m
  



t 

  G  t  D 1  
 D


f (m)
Mott
EVOLVE
EVOLVE - Calibrated
Where :
N m   T ot alnumber of fragment swit h mass great er t han m
M  T ot alcase mass
B  Explosiveconst ant
D  Explosivediamet er
t  met alt hickness
m
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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:

VPeak,Cyl
M 1
 2E    
 C 2
• NASA’s empirical model is used for the remaining fragments
• A transition function is used to integrate both models
Gurney
HE
EVOLVE
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DEBRIS Δ VELOCITY DISTRIBUTION CALCULATION (Cont.)
• 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
Center of Mass Velocity
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INTERCEPTION DEBRIS – FROM INITIALS TO FULL SIGNATURE
RCS DISTRIBUTION CALCULATION
• 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
Radar A
WALES, Ltd.
Radar B
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INTERCEPTION DEBRIS – FROM INITIALS TO FULL SIGNATURE
EXAMPLE OF MODEL RESULT – DEBRIS CLOUD SIMULATION
BASED ON GENERIC TARGET AND INTERCEPTOR
Generic HE RV, HTK Interception
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INTERCEPTION DEBRIS – FROM INITIALS TO FULL SIGNATURE
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
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MAY 2010
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