1. A Chameleon Suit to Liberate
Human Exploration of Space
Environments
Ed Hodgson
HSSSI
October 30, 2001
2. 2
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 Heated
Surfaces Insulated
Intimate
Contact
Metabolic Heat Rejected Through
Transmissive Surfaces With Low
Sink Temperature
Maximum
Insulation Value
Maximum
Transmissivity
Minimum
Emissivity
Maximum
Loft
Q Q
Maximum
Emissivity
4. Performance - Feasibility Assessment
4
Maximum Radiated Heat Load
From PLSS Area
800
700
600
500
400
300
200
100
0
Maximum Sustained Work Rate
Sink Temp.
40 80 120 160 200 240 280 320
Outer Surface Temperature of Suit (K)
Heat Rejection (Watts)
50 K
150 K
250 K
Minimum Resting Metabolic Rate
Skin Comfort
Conditions
Average EVA Work Rate
Maximum Radiated Heat Load
From Whole Suit Area
800
700
600
500
400
300
200
100
0
Maximum Sustained Work Rate
Sink Temp.
Skin Comfort
Conditions
Average EVA Work Rate
40 80 120 160 200 240 280 320
Outer Surface Temperature of Suit (K)
Heat Rejection (Watts)
50 K
150 K
250 K
Minimum Resting Metabolic Rate
5. 5
Performance - Mission
Environments & Interactions
Heat Rejection Vs Sun Angle to Surface Normal
300
250
200
150
100
50
0
Sink Temp.
0 20 40 60 80 100
Sun Angle to Surface (degrees)
Heat Rejection (Watts/Sq.M)
225 F
255 F
285 F
Heat Rejection Capability With and Without
Directional Shading
900
800
700
600
500
400
300
200
100
0
0 15 30 45 60 75 90
Solar Elevation Angle (degrees)
Maximum Sustainable
Metabolic Rate (Watts)
No Directional Shading
Directional Shading
Average EVA
Metabolic Rate
6. 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
6
Performance - System Elements
Requirements Derivation
Suit Material Layers
... Surface Martian
Insulating Suit Layers
with Activated Spacers
Suit Material Layers
Deep
Skin Surface Space
... Conducting Layers
with De-Activated Spacers
Outer Suit Inner Suit
Skin
Night
Outer Suit Inner Suit
Hot and Warm Environments
• Max Metabolic Rate →600 W
• Emissivity →0.85
• Conductivity → 300 W/m2-°C
• 6-layer Conductivity→50 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
7. 7
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
Plane Reflective
• Supplemental Heat Transport
• Micro-Heat Pump Technology Rotating Reflective
Louvers
Emitted IR From Suit
Surface
Higher Angle IR -
Partially Reflected
Incident IR From Hot
Surfaces - Totally Reflected
Corner Reflectors -
Retroreflective Surface
Surface
8. 8
Chameleon Suit Layer Structure
EAP Layer Spacing Control Actuators
Thermally Conductive
Fiber Felt
Insulating Polymer
Isolation Layer
Polymer Infra-red
Electrochromic
(2 active layers + SP electrolyte)
Positive Voltage Supply
(conductive polymer?)
Negative Voltage Supply
(conductive polymer?)
IR Transparent Conductive Control Electrode
(& temperature sensor)
9. System Sensing & Control Basics
9
Computer
Control
Power
Supply
text
User
Metabolic
Rate
Local Temperature &
Heat Flow
Emissivity
Control
Layer Spacing
Control
Active Protective
Garment
• 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
10. 1.2
1
Temperature Error (C) 0
0.8
0.6
0.4
10
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
60
50
40
30
20
10
0
0 50 100 150 200
Zone Angular Width (Degrees)
0.2
Relative Heat Rejection
Temp Error, Tsink=-18
Temp Error, Tsink=10
Q relative, Tsink=-18
Q relative, Tsink=10
Tmax
T1
Control & Sensing Zones Inactive Zones
Head 11 Gloves
Torso 32 Elbows
Upper Arm 24 Knees
Lower Arm 24 Boots
Upper Leg 24
Lower Leg 24
Shoulders 7
Total 146
11. 11
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
12. 12
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
13. 13
Control And Feedback
Preferred Implementation
• 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
14. 14
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
Sensor
Power
Wireless
Comm
15. 15
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
16. 16
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
17. 17
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
800
700
600
500
400
300
200
100
0
0 0.2 0.4 0.6 0.8 1
Compression (mm)
Conductance (W/Sq.M)
18. 18
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
19. 19
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
20. 20
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
21. 21
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
10000
1000
100
10
1
Units
Launched
ISS Operations
1 10 100 1000
Number of 2 Person EVA's / Mission
Launch Mass Savings (Kg)
3
8
20
NASA Mars
Design Reference Mission
Lagrange Point
Assembly & Lunar
Visit Missions
22. 22
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
