2008 Winter Seminar Hypervelocity Impact Analysis of Space Debris on Shield System using SPH method Dec. 9th 2008 Smart Structures and Composite Laboratory Aerospace Engineering, KAIST Bok-Won Lee

Space Shielding System Hyper Velocity Impact(HVI) Analysis CONTENTS 1 Introduction  Research Background  Space Debris 2 Space Shielding System  Introduction of Space Shielding System  SPH computational method 3 Hyper Velocity Impact(HVI) Analysis  Modeling Methodology  Hypervelocity Impact Analysis  Validation of the Computational Model 4 Concluding Remarks  Summary and Future Works

INTRODUCTION Research Background Space Debris Space debris in low-earth orbit(LEO) * NASA Orbital debris problem office Space debris in geosynchronous orbit (GEO) * GEO zone is from 35,786km from eartth * European Space Operations Centre Spatial density of space debris * ESA Master-2001(Telescope) Space debris  natural meteoroid fragments  man-made space waste : stuffs from ISS construction, various accidental discards, fragments from exploded spacecraft About 100 tons of fragments were generated during human being’s space exploring event US strategic command identified 13,000 objects to prevent misinterpretation as hostile missiles More than 600,000 objects larger than 1cm in LEO  Hypervelocity impact of debris could potentially lead to a disaster of the spacecraft

INTRODUCTION Research Background Spacecraft failed and damaged due to meteoroid or debris impact Space debris travels LEO at hypervelocity speeds up to a maximum of 16km/s. The size of the debris varies from micrometers to several meters. Most man-made debris is consisted of Al, Fe, Ti, Si, C. (fragment of space structure and electric components) Meteoroid travels in GEO at average 70km/s

INTRODUCTION Shielding System Space Shielding System Monolitic shield Kevlar and Nextel composite plate layer Sacrificial Al bumper Monolitic shield Whipple bumper shield Stuffed Whipple bumper shield Foam filled layers Multiple layers Kevlar fabric layers Mass module shield Multi-shock shield Beta cloth shield

HYPER VELOCITY IMPACT(HVI) Hyper Velocity Impact(HVI) Phenomenon Oblique HVI of generic multi-wall system Hyper Velocity Impact Phenomenon HVI testing setup (UDRI) Radiographs of debris cloud (UDRI)

INTRODUCTION Smooth Particle Hydrodynamics Smooth Particle Hydrodynamics(SPH) code in HVI problems Smooth Particle Hydrodynamics: Meshless method developed during 1980’(Gingold, Monaghm) in astrophsycis to study the collision of galaxies and the impact bodies on the planet Applications Astrophysical problems Hypervelocity impact of brittle solids bodies Chemical explosions Explosive forming Advantages Meshless method Efficient method for large deformation problems Does not suffer from the mesh based Lagrangian approach SPH particle approximation Limitations Computationally expensive Analytically lack of the supporting theories Inaccuracy in domain boundaries Governing Equations

SPH COMPUTATIONAL MODEL  HVI Computational model using SPH (CASE 1) Model Information Element 300 solid elements 18759 SPH nodes Mass of single SPH node : 0.825 μg Time step : 50 ns Unit system : cm, ms, Gpa, Mbar 80mm 9.53 mm (6.64km/s) 2.2 mm thick LS-DYNA keyword for SPH *SECTION_SPH: Defines parameters for every part of SPH particles *CONTROL_SPH: Defines general control parameters required for calculation *ELEMENT_SPH: Defines every particle, assigns part IDs and mass of the particle

HVI ANALYSIS Analysis Results  HVI Simulation HVI condition (Case I) Projectile: Al2017-T4(9.53mm) Plate: Al6061-T6(2.2mm) HVI velocity: 6.64km/s Computational time : 2h 32min (4 Core CPU, 4G Ram)

HVI ANALYSIS Analysis Results α β d1 d2 h  Comparison of the debris cloud (Case I) HVI condition (Case I) Projectile: Al2017-T4(9.53mm) Plate: Al6061-T6(2.2mm) HVI velocity: 6.64km/s α β d1 v3 v2 v1 d2 h Debris cloud shape*(Experiment at 6ms) Debris cloud shape (Numerical at 5.99ms) Parameter α β d1 d2 h v1 v2 v3 Experiment 77° 67° 23mm 34mm 36mm 6.1km/s 5.9km/s 3.5km/s HVI analysis 71° 70° 25mm 31mm 38mm 6.5km/s 5.8km/s 3.3km/s Ref. * : Andrew J. Piekutowski, “Dynamic model for the formation of debris cloud,” Int. J of Impact Engr. 1990, University of Dayton Research Institute.

HVI ANALYSIS Analysis Results α β d2 d1 h  Comparison of the debris cloud (Case II) HVI condition (Case II) Projectile: 304L Steel (5mm) Plate: Al6061-T6(2.85mm) HVI velocity: 5.53km/s α β d2 d1 v1 h Debris cloud shape*(Experiment at 10.4ms) Debris cloud shape (Numerical at 10.56ms) Parameter α β d1 d2 h v1 Experiment 78° 72° 1.8mm 31mm 46mm 6.1km/s HVI analysis 79° 74° 1.7mm 29mm 48mm 6.5km/s  SPH method is able to reproduce the global shape of the debris cloud within 10% difference. * needs to add more particles to enhance the accuracy.

HVI ANALYSIS Analysis Results  Comparison of Impact Pressure Analytic Calculation (Hugoniot Eqn*) PHt : pressure of the target PHp: pressure of the projectile ρ0t: densiyt of the target v1: velocity of the particle at the impact point V0: impact velocity of projectile C0: sound speed Ss: coefficient of the materials Parameter Target pressure Projectile pressure Analytic calculation 0.9 Mbar HVI analysis 0.89 Mbar 1.15Mbar  SPH method is promising numerical formulation for HVI problem of metallic structures. Ref. * : W. Herrmann, J.S. Wilbeck, “Review of Hypervelocity penetration theories,” 1987

Computational Analysis CONCLUDING REMARKS Future Works Projectiles Experiments Metallic impactor Hailstone Meteoroids Hypervelocity impact (1km~12km/s) Radiograph imaging Highly protective facilities Shielding System Space Environment Metallic multilayer shields Composite shields Hybrid shields Test in vacuum chamber Degradation of HVI resistance for LEO environment aged composite HVI debris impact problems Computational Analysis Meshless analysis technique Semi-empirical model to predict debris cloud Applicability for composite materials Enhancement of prediction accuracy Stochastic analysis  There are many remained fields to be investigated for HVI research area.

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