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A Chameleon Suit to Liberate Human Exploration of Space
Environments
Ed HodgsonHSSSI
October 30, 2001
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Concept Summary
• Enabling Waste Heat Rejection From Full Suit Surface Area
• Controlled Suit Heat Transfer– Matches metabolic load and
environment– Layer contact and distance
(conduction changes)– Layer emissivity
• Eliminate Expendables• Simpler, Lighter Life Support
Sun HeatedSurfaces Insulated
Metabolic Heat Rejected ThroughTransmissive Surfaces With Low
Sink Temperature
MaximumInsulation Value
MaximumTransmissivity
MinimumEmissivity
MaximumLoft
Q Q
IntimateContact
MaximumEmissivity
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Mission Needs Addressed
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Performance - Feasibility Assessment
Maximum Radiated Heat LoadFrom PLSS Area
0
100
200
300
400
500
600
700
800
40 80 120 160 200 240 280 320
Outer Surface Temperature of Suit (K)
Heat
Rej
ectio
n (W
atts
)
50 K150 K250 K
Sink Temp.
Maximum Sustained Work Rate
Minimum Resting Metabolic Rate
Skin Comfort Conditions
Average EVA Work Rate
Maximum Radiated Heat LoadFrom Whole Suit Area
0
100
200
300
400
500
600
700
800
40 80 120 160 200 240 280 320
Outer Surface Temperature of Suit (K)
Heat
Rej
ectio
n (W
atts
)50 K150 K250 K
Sink Temp.
Maximum Sustained Work Rate
Minimum Resting Metabolic Rate
Skin Comfort Conditions
Average EVA Work Rate
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Performance - Mission Environments & Interactions
Heat Rejection Vs Sun Angle to Surface Normal
0
50
100
150
200
250
300
0 20 40 60 80 100
Sun Angle to Surface (degrees)
Heat
Rej
ectio
n (W
atts
/Sq.
M)
225 F
255 F
285 F
Sink Temp.
Heat Rejection Capability With and Without Directional Shading
0
100
200
300
400
500
600
700
800
900
0 15 30 45 60 75 90
Solar Elevation Angle (degrees)
Max
imum
Sus
tain
able
Met
abol
ic R
ate
(Wat
ts) No Directional Shading
Directional Shading
Average EVAMetabolic Rate
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Performance - System Elements Requirements Derivation
Skin Surface...DeepSpace
Outer Suit Inner Suit
Conducting Layers with De-Activated Spacers
Suit Material Layers
SkinSurface...
Martian Night
Outer Suit Inner Suit
Insulating Suit Layerswith Activated Spacers
Suit Material Layers
Hot and Warm Environments • Max Metabolic Rate → 600 W• Emissivity → 0.85• Conductivity → 300 W/m2-°C• 6-layer Conductivity→ 50 W/m2-°C
Cold Environment (Mars Night)• Min Metabolic Rate → 100 W• Outer Layer Emissivity → 0.85• Conductivity → 0.96 W/m2-°C• 6-layer Conductivity→ 0.16 W/m2-°C
Radiation transport can be limited to acceptable loss for resting conditions in cold environment
Thermal resistance can be minimized to increase radiation transport for hot environment
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Concept Evolution, Refinement and Growth Potential
• Conductive Velvet Interlayer Contact– Reduced temperature drop to
outer surface
• MEMS Directional Shading Louvers– Radiative heat rejection in
“impossible” environments
• Supplemental Heat Transport• Micro-Heat Pump Technology Rotating Reflective
Louvers
Incident IR From HotSurfaces - Totally Reflected
Higher Angle IR -Partially Reflected
Emitted IR From SuitSurface
Corner Reflectors -Retroreflective Surface
Plane ReflectiveSurface
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EAP Layer Spacing Control Actuators
Thermally ConductiveFiber Felt
Insulating PolymerIsolation LayerPolymer Infra-redElectrochromic(2 active layers + SP electrolyte)
Positive Voltage Supply(conductive polymer?)Negative Voltage Supply(conductive polymer?)
IR Transparent Conductive Control Electrode(& temperature sensor)
Chameleon Suit Layer Structure
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System Sensing & Control Basics
ComputerControl
text
PowerSupply
UserMetabolic
Rate
Local Temperature &Heat Flow
Layer SpacingControl
EmissivityControl
Active ProtectiveGarment
• Local Temperature & Centralized Metabolic Rate
• Local Temperature is Key– Outside surface sets feasibility
of heat rejection– Inside surface controls
comfort– Layer delta T gives heat flux
• Metabolic Rate– Sets comfort temperature– Sets total heat flux
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System Sensing & Control• System Control Needs
– Maintain Thermal Comfort– Avoid Hot & Cold Touch
Temperatures
• Environmental Factors– Hot & Cold Extremes– Rapid Variation– Directional Sources
• Sun, Hot Surfaces
• Crew Motion– Contact Pressure
• Suit Control Zones
Effect of Sensing & Control Zone Angular Size
0
10
20
30
40
50
60
0 50 100 150 200Zone Angular Width (Degrees)
Tem
pera
ture
Err
or (C
)0
0.2
0.4
0.6
0.8
1
1.2
Rel
ativ
e H
eat R
ejec
tion
Temp Error, Tsink=-18Temp Error, Tsink=10Q relative, Tsink=-18Q relative, Tsink=10
TmaxT1
Control & Sensing Zones Inactive Zones
Head 11 GlovesTorso 32 ElbowsUpper Arm 24 KneesLower Arm 24 BootsUpper Leg 24Lower Leg 24Shoulders 7
Total 146
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Sensing & Control Integration Options
• Driving Factors– Robust Control
• Simple signal and power interfaces
• Minimize harnesses • Redundancy
– Minimize Heat Leak– Minimize Power/Weight/Volume
of Control Electronics
• Control Basis– Total Heat Rejection– Skin Comfort temperature– Comfort Indicators
• Architecture Options– Centralized– Distributed
• Signal Transfer– Analog/Sensor inputs– Data Bus, Wireless– Effector Drivers– Power Distribution
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Control And Feedback
• ~150 Zones, 5 layers => High I/O Count
• Centralized Control Requires Complex Data Transfer, High Data Rates
• Optimal Approaches in Dealing With High I/O Counts Are Based on a Distributed Processing Concept
• Distributed Control Zones for Segments of the Suit Simplify the I/O Requirements
ZONES
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• Central Processor– Determines metabolic rate– Transmits inner wall T targets– Receives zone status & wall T
• Networked dedicated zone controllers– Receive T targets & local T’s– Locally send actuator control signals– Transmit inner wall T & status
• Signal transmission– Wireless IEEE 802.11B protocol– Alternate - signals on power lines
Zone Controllers
Control And FeedbackPreferred Implementation
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Power Distribution• Current Technology Harnesses
– Weight, Reliability, Mobility Impacts
• “Smart” Garment Technology– Integrated Power and Signal
Distribution• Conductors woven in cloth
layers• Conducting polymer layers
– Integrated Sensing, Data Terminal, Actuator Control Elements on Chip
• Wireless Data Transmission, Local Control Components
– Only Power Physically Connects Layers (Thermal Short)
– Minimum Number of Connections
Fabric Effector Control
and Input Power Layers
Effectors
Embedded
Control
Power
Sensor
Wireless
Comm
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Technology Base Assessment -Development Needs Key Areas
• Variable Geometry Insulation– Light weight, flexible biomimetic polymer actuators.– Durable and effective felt thermal contact material.
• Controlled Thermal Radiation– Effective thermal IR electrochromic polymers with high
contrast ratios– “Soft” MEMS directional louver implementations.
• “Smart” Garment Sensing and Control Integration• Cost Effective Integrated Garment Manufacturing
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Variable Geometry Insulation Actuators
• Elongating polymers (MIT)– Conductive polymers (PPy, PAN)– liquid, gel or solid electrolytes– 2% linear , 6% volumetric at ~ 1V
• Bending polymers (UNM)– Ionic polymer-metal composites (Nafion-Pt)– need to prevent water leakage (encapsulation, better Pt
dispersion)– complete loop with <3V
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Interlayer Thermal Contact
• Low Thermal Resistance Is Required – High Metabolic Rates– Warm Environments– Vacuum Conditions– Low Contact Pressure
• Carbon Fiber Felts Show Good Performance
• Durability in Application Requires Development
Carbon Felt Contact Conductance Vs. Compression
0100200300400500600700800
0 0.2 0.4 0.6 0.8 1
Compression (mm)
Con
duct
ance
(W/S
q.M
)
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Electro-emissive Technologies
• Most Broadband Infra-red Research Has Been With Inorganic EC Materials (WO3)
• Contrast Ratios > 2:1 in the Thermal IR Shown
• Polymer EC Materials are Under Study by Numerous Investigators
• Much Further Development is Needed
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Directional Shading Louvers• MEMS Louver Technology is Under Development
for Satellite Applications– Shown to Provide Effective Emissivity Modulation– Options Under Study Include Pivoting Louvers Required
for Chameleon Suit Directional Shading
• Louver Size for IR Corner Reflectors is Compatible With Application (~.03 mm deep)
• Major Development Challenges– Integration in Flexible Garment– Removable Louver Layers
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Sensing & Control Integration
• Systems Embodying the Required Functions Are Being Developed for Many Uses
• Key Challenges Will Be:– Space Environment Compatibility– Limiting Weight & Maintaining Flexibility With Many Layers
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Mission Benefits Assessment• Substantial Launch Mass
Savings– Savings For All Missions– EVA Intensive 1000 Day
Class Missions Benefit Most
• ~ 3.5 Kg Reduction in EVA Carry Mass
• Capability for Non-Venting Operations in Most Environments– Science & Servicing
Flexibility
Chameleon Suit Launch Mass Savings
1
10
100
1000
10000
1 10 100 1000Number of 2 Person EVA's / Mission
Laun
ch M
ass
Savi
ngs
(Kg)
3820
Units Launched
NASA Mars Design Reference Mission
Lagrange Point Assembly & LunarVisit Missions
ISS Operations
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Summary & Conclusions
• Studying the Chameleon Suit Reveals Many New Challenges– None Have Yet Proved Insoluble
• Many Required Technology Advances are Pursued Elsewhere– Specific Development and
Adaptation Work is Required
• Potential Benefits to NASA are Substantial and Real– Further Study Should be Pursued