1. 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

2. 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

3. 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

4. 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

5. 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

6. 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)

7. 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

8. SPH COMPUTATIONAL MODEL
 HVI Computational model using SPH (CASE 1)
Model Information
Element solid elements SPH nodes
Mass of single SPH node : 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

9. 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)

10. 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.

11. 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.

12. 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

13. 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.

14. Thank You