Christiansen, Eric

Lear, Dana

NASA Technical Reports Server

1 
National Aeronautics and 
Space Administration 
Micrometeoroid and Orbital Debris Environment 
& 
Hypervelocity Shields 
Eric L. Christiansen 
Dana M. Lear 
 
NASA Johnson Space Center 
Mail Code KX 
Houston, TX 77058 
 
February 2012 
https://ntrs.nasa.gov/search.jsp?R=20120002584 2019-08-30T19:17:40+00:00Z
2 
National Aeronautics and 
Space Administration Purpose of this presentation 
• Provide background on micro-meteoroid & orbital debris 
(MMOD) shielding protection  
• MMOD environment 
• MMOD protection requirements 
• Shielding approaches 
 
 
3 
National Aeronautics and 
Space Administration MMOD Environment Models 
• Orbital Debris (OD) environment models 
• Orbital Debris environment (ORDEM2000): 1-17 km/s 
• Debris flux increases with increasing altitude up to about 1500km altitude 
• Debris is not a major factor above GEO altitude (35786km) 
• Debris environment subject to change (ORDEM 3.0 release pending) 
 
Orbital Debris in Earth Orbit 
0.4
0.5
0.6
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0.9
1.0
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1.4
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N
or
m
al
iz
ed
 O
rb
ita
l D
eb
ris
 F
lu
x 
(0
.3
cm
 &
 la
rg
er
)
Normalized Orbital Debris Flux by Year at ISS Altitude 
For Threat Particle Sizes > 0.3cm  
(Normalized to 2006 flux) 
 Note OD Risk is proportional to Flux 
4 
National Aeronautics and 
Space Administration MMOD Environment Models (cont.) 
• Meteoroid model (MEM) provided by MSFC 
• http://www.nasa.gov/offices/meo/home/index.html 
• Meteoroid environment (MEM): 11-72 km/s 
• Average 22-23 km/s 
• MM environment model is subject to change (new release of MEM is 
pending) 
• Orbital Debris is the predominate threat in low Earth orbit 
• For ISS, debris represents approximately 2/3rds of the MMOD risk 
• For missions to the Moon, L1, or elsewhere, OD risk will need to be 
assessed for time period spacecraft resides in LEO 
• Meteoroid risk is influenced by Earth focusing (gravitational) factor 
and Earth shadowing while in Earth orbit 
• Meteoroid risk far from Earth is typically less compared to meteoroid risk 
in LEO 
5 
National Aeronautics and 
Space Administration MMOD Damage to spacecraft 
• Several ISS and Shuttle MMOD damages 
appear to have been caused by >1mm 
diameter MMOD particles 
• FGB compressor damage due to 2mm-3mm 
diameter particle 
• P6 radiator damage due to 3mm-5mm particle 
• SM solar array damage due to >2mm particle 
• STS-118 radiator damage due to high density 
1mm particle 
 
• Good agreement between actual damage to 
predictions for ISS Pressurized Logistics 
Module and Shuttle (damage identified after 
return to ground) 
 
FGB damage (1” x 2”) likely due to 
2mm-3mm diameter MMOD particle 
P6 radiator damage noted during STS-118 (0.75” 
diameter) likely due to 3-5mm diameter x 1mm thick 
MMOD particle 
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National Aeronautics and 
Space Administration 
MMOD Shielding 
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National Aeronautics and 
Space Administration MMOD Protection Requirements 
• MMOD risk is a function of vehicle size, mission duration (time 
exposed to MMOD), failure criteria, shielding, flight trajectory 
 
• MMOD requirements are key aspect of providing adequate MMOD 
protection, crew safety and vehicle survivability 
 
• Typically MMOD protection requirements expressed in terms of 
maximum allowable failure risk over a time period, or a reliability 
level (probability of no failure) 
• For instance, Orion Lunar sortie (24 day mission) maximum allowable 
MMOD loss-of-crew (LOC) risk is 1 in 1000 (0.1% risk), and Lunar 
outpost (210 day mission) maximum allowable MMOD risk is 1 in 500 
(0.2% risk) 
• Note, that over many missions, the cumulative MMOD risk increases with the total 
duration of all missions 
 
8 
National Aeronautics and 
Space Administration Hypervelocity impact effects 
• At hypervelocity, small particles can cause a lot of damage 
• High velocity MMOD particles represent a substantial threat to spacecraft which 
typically are constructed with light-weight materials to save mass 
• Rule of thumb: at 7km/s, aluminum sphere can penetrate completely through an 
aluminum plate with thickness 4 times the sphere’s diameter 
• A multi-layer spaced shield provides more effective protection from 
hypervelocity impact than single layer (total shield thickness < projectile 
diameter) 
Monolithic target Two-layer Whipple shield 
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National Aeronautics and 
Space Administration ISS MMOD protection approach 
• Multi-faceted approach to mitigating MMOD 
Risk on ISS 
1. Robust shielding 
• ISS has best shielding ever flown:  US/ESA/Japan 
Nextel/Kevlar “stuffed” Whipple shields effective for 
1.3cm diameter debris impacting at typical impact 
conditions 
• Redundant & hardened external systems; e.g. US 
Radiators 
2. Collision avoidance 
• Maneuver to avoid ground trackable orbital debris 
(typically ≥ 10cm diameter) 
3. Sensors & crew response to leak if needed 
• Leak detection, isolation, repair 
2mm Al 
MLI 
6 Nextel AF62 
6 Kevlar 
4.8mm Al 
11
.4
 c
m
 
0.5” diameter hypervelocity 
projectile penetrates nearly 2” thick 
aluminum block, but is stopped by 
NASA stuffed Whipple shields 
which weigh far less (same as 3/8” 
thick aluminum) 
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National Aeronautics and 
Space Administration 
Shielding Design and Verification 
Methodology 
Probability of 
No Failure 
Environment Models 
- Debris & Meteoroid 
Spacecraft 
Geometry 
Ballistic Limit 
Equations 
MMOD Probability Analysis Code 
Failure Criteria 
HVI Test & 
Analysis 
Meet Requirements? 
Qualify 
Yes 
Iterate 
No 
S/C  
Operating 
Parameters 
• Identify vulnerable spacecraft components/subsystems 
• Assess HVI damage modes  
• Determine failure criteria 
• Perform HVI test/analysis to define “ballistic limits” 
• Conduct meteoroid/debris probability analysis 
• Compare MMOD analysis results with requirement 
• Updates to design, operations, analysis, test, or failure criteria 
• Update/Iterate as necessary to meet requirement 
Protection 
Requirement 
P 
R 
P > R 
P < R 
BUMPER 
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National Aeronautics and 
Space Administration 
ISS MMOD shielding 
finite element model for Bumper code MMOD risk 
assessments 
Each color represents a different MMOD shield configuration 
Earth 
Velocity 
direction 
FGB 
SM 
NASA 
JAXA 
ESA 
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National Aeronautics and 
Space Administration ISS “Stuffed Whipple” Shielding 
• US, JAXA and ESA employ “Stuffed Whipple” shielding on the areas of their 
modules exposed to greatest amount of orbital debris & meteoroids impacts 
• Nextel and Kevlar materials used in the intermediate bumper 
• shielding capable of defeating 1.3cm diameter aluminum sphere at 7 km/s, normal impact 
NASA configuration JAXA configuration ESA configuration 
2mm Al 
MLI 
6 Nextel AF62 
6 Kevlar fabric 
4.8mm Al 
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.4
 c
m
 
1.3mm Al 
MLI 
3 Nextel AF62 
4 Kevlar fabric  
4.8mm Al 
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.4
 c
m
 
2.5mm Al 
MLI 
4 Nextel AF62 
Kevlar-Epoxy 
4.8mm Al 
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  c
m
 
Al Mesh 
(Typical Configurations Illustrated) 
Typically, bumpers are Al 6061-T6, rear walls are Al 2219-T87 or Al 2219-T851 
Kevlar 29 style 710 or Kevlar KM2 style 705 fabric are typically used 
13 
National Aeronautics and 
Space Administration MMOD shielding background 
• MMOD shields typical composed of bumper(s), standoff, and rear 
wall (final protection layer) 
• Exclude multi-layer insulation (MLI) thermal blanket 
 
Shield 
bumper 
intermediate 
bumper 
rear wall 
S
ta
nd
of
f 
Purpose: Breakup MMOD particle, laterally 
disperse resulting debris 
Key material & physical parameters (V ≥ 7 km/s): 
density, thickness to projectile diameter ratio, 
thermal properties  
MMOD particle 
(projectile) 
Purpose: Further breakup debris from first impact, 
slow expansion of debris cloud 
Key material & physical parameters (V ≥ 7 km/s): 
combination of first bumper and rear wall properties 
Purpose: Stop debris from MMOD & bumper(s) 
Key material & physical parameters (V ≥ 7 km/s): 
strength, toughness, thickness 
14 
National Aeronautics and 
Space Administration 
15 
National Aeronautics and 
Space Administration Shielding assessments for inflatables 
• Hypervelocity impact tests have been performed for MMOD 
shielding of potential inflatable modules, for two damage modes: 
(1) Failure of shield protecting restraint layer 
(2) Failure of shield, restraint and bladder 
BEAM inflatable 
on Node 3 aft  
Deep Space 
Habitat  inflatable 
demonstrator on 
Node 2 nadir 
shield 
shield 
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National Aeronautics and 
Space Administration Summary 
• MMOD shielding capability influenced by both:  
1. Configuration – “standoff” (more is better),  number of bumper shield 
layers 
2. Material selection – ceramics/metals on exterior of shield, high-strength 
to weight ratio (fabrics & composites) on interior of shield 
 
• More information available: 
• NASA TP-2003-210788, Meteoroid/Debris Shielding 
• NASA TM-2009-214785, Handbook for Designing MMOD Protection 
• NASA TM-2003-212065, Integration of MMOD Impact Protection 
Strategies into Conceptual Spacecraft Design 
• NASA TM-2009-214789, MMOD Shield Ballistic Limit Analysis Program 
 
 
 
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National Aeronautics and 
Space Administration 
Backup Charts 
National Aeronautics and Space Administration 
Cataloged objects >10 cm diameter 
1960 
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National Aeronautics and Space Administration 
Cataloged objects >10 cm diameter 
1970 
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National Aeronautics and Space Administration 
Cataloged objects >10 cm diameter 
1980 
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National Aeronautics and Space Administration 
Cataloged objects >10 cm diameter 
1990 
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National Aeronautics and Space Administration 
Cataloged objects >10 cm diameter 
2000 
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National Aeronautics and Space Administration 
Cataloged objects >10 cm diameter 
August 2009 
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National Aeronautics and 
Space Administration 
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0 2 4 6 8 10 12 14
Velocity (km/s)
C
rit
ic
al
 A
l D
ia
m
et
er
 (c
m
Whipple dcrit @ 0 deg
monolithic dcrit @ 0 deg
Ballistic Regime 
Fragmentation & 
Partial Melt Regime Complete Melt Regime Velocity Range: 
State of Debris Cloud: 
(for Al on Al impacts) 
Few solid fragments 
Many (increasing 
with velocity) solid 
fragments & liquid 
droplets 
Fine droplets, few solid 
fragments, some vapor 
Ballistic Limit Improvement due 
to Shield Standoff 
∆ dCrit 
Expect “failure” above curves 
0.12cm Al bumper 
0.32cm Al6061T6 rear wall 
10cm
 
standoff 
WHIPPLE 
Ballistic Limits for Whipple Shield & equal mass Monolithic 
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National Aeronautics and 
Space Administration ISS MMOD shielding 
• Many different shield 
configurations protect 
ISS modules, external 
pressure vessels, 
gyros, and visiting 
vehicles from MMOD 
• High risk areas 
found by analysis 
• More capable 
shielding (i.e., 
stopping larger 
particles) placed 
where expect 
greatest amount of 
MMOD hits 
26 
National Aeronautics and 
Space Administration Shielding materials 
• Nextel (3M Inc. trade mark): fabric consisting of alumina-boria-silica 
ceramic fibers 
• Other ceramic and glass fabrics tested, and will provide adequate 
MMOD protection (substitute equal mass for Nextel) 
• Kevlar aramid fabric: highest hypervelocity protection performance 
found using Kevlar KM2 fabrics 
• Other high-strength to weight materials incorporated in MMOD shields 
include Spectra, Vectran, carbon fabric and carbon-composites 
 
27 
National Aeronautics and 
Space Administration FGB and Service Module (SM) 
Mesh & Multi-Shock MMOD Shields 
• Majority of FGB shields include 2 or more bumpers spaced in front of the 
module pressure shell or propellant tank wall (superior to single bumper shields) 
• Metal mesh layers provide additional protection in many FGB shields (a mesh causes greater spread to the debris 
cloud resulting from high velocity collision) 
• SM augmentation shields rely on multi-shock ceramic fabric layers 
• FGB shields & SM augmentation shields provide protection from 1-1.5cm 
diameter aluminum projectiles (typical).   
• Unaugmented SM shields protect from ~0.3cm aluminum projectiles (typical) 
FGB Zone 11c,d,f SM deployable shield/zone 6 
orientation of zone 8 not parallel to 4 augmentation bumpers  
0.3/10/1.5mm Al honeycomb 
MLI 
steel mesh (2) 
fabric (1) 
1.4mm Al 
pressure shell 
10
 c
m
 
MLI 
basalt 
fabric 
layers 
Original Zone 6 
1.0mm Al 
25
 c
m
 
0.3/10/1.0mm Al honeycomb 
1.6mm Al 
pressure shell 
5 
cm
 
va
ria
bl
e 
SM conformal shield/zone 8 
Original Zone 8 
MLI 
0.5/10/0.5mm graphite-
epoxy honeycomb 
2.3mm Al 
pressure shell 
2 
cm
 
1mm Al 
Corrugated 0.5mm Al 
Russian “Kevlar” fabric (6) 1
0 
cm
 
Fiberglass panel 
28 
National Aeronautics and 
Space Administration 
MMOD shields added to Service Module 
by extravehicular activity (EVA) 
Additional MMOD shield panels added by EVA 
(each consist of layers of aluminum, corrugated 
aluminum, fiberglass and Russian Kevlar) 


Micrometeoroid and Orbital Debris Environment and Hypervelocity Shields

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