A Chameleon Suit to Liberate Human Exploration of Space Environments
Ed Hodgson HSSSI October 30, 2001
Concept Summary Maximum Loft
Minimum Emissivity Intimate Contact
Q
Maximum Emissivity
Q Maximum Insulation Value
Maximum Transmissivity
Sun Heated Surfaces Insulated
• 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 Metabolic Heat Rejected Through Transmissive Surfaces With Low Sink Temperature
2
Mission Needs Addressed
3
Performance - Feasibility Assessment
Maximum Radiated Heat Load From PLSS Area
Maximum Radiated Heat Load From Whole Suit Area
800
800 700
Maximum Sustained Work Rate
Heat Rejection (Watts)
Heat Rejection (Watts)
700 600 500
Sink Temp.
400
50 K 150 K 250 K
300
Skin Comfort Conditions
Average EVA Work Rate 200
Sink Temp.
500
Skin Comfort Conditions
50 K 150 K 250 K
400 300
Average EVA Work Rate 200 Minimum Resting Metabolic Rate
Minimum Resting Metabolic Rate 100
Maximum Sustained Work Rate
600
100
0
0
40
80
120
160
200
240
Outer Surface Temperature of Suit (K)
280
320
40
80
120
160
200
240
Outer Surface Temperature of Suit (K)
280
320
4
Performance - Mission Environments & Interactions Heat Rejection Vs Sun Angle to Surface Normal He a t Re je c tion (W a tts /S q.M )
300 250
Sink Temp.
200
225 F
150
255 F
100
285 F
50 0 0
20
40
60
80
100
Sun Angle to Surface (degrees)
Heat Rejection Capability With and Without Directional Shading 900
Maximum Sustainable Metabolic Rate (Watts)
800 No Directional Shading
700
Directional Shading
600 500 400 300 Average EVA Metabolic Rate
200 100 0 0
15
30
45
60
Solar Elevation Angle (degrees)
75
90
5
Performance - System Elements Requirements Derivation Cold Environment (Mars Night)
Suit Material Layers
Martian Night
Skin Surface
...
Outer Suit
Insulating Suit Layers with Activated Spacers
Inner Suit
• • • •
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
Hot and Warm Environments
Suit Material Layers
Deep Space
Outer Suit
Skin Surface
...
Conducting Layers with De-Activated Spacers
Inner Suit
Thermal resistance can be minimized to increase radiation transport for hot environment
• • • •
Max Metabolic Rate → 600 W Emissivity → 0.85 Conductivity → 300 W/m2-°C 6-layer Conductivity→ 50 W/m2-°C 6
Concept Evolution, Refinement and Growth Potential • Conductive Velvet Interlayer Contact
Emitted IR From Suit Surface
– Reduced temperature drop to outer surface
Higher Angle IR Partially Reflected
• MEMS Directional Shading Louvers – Radiative heat rejection in “impossible” environments
• Supplemental Heat Transport • Micro-Heat Pump Technology
Incident IR From Hot Surfaces - Totally Reflected
Plane Reflective Surface Corner Reflectors Retroreflective Surface Rotating Reflective Louvers
7
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)
8
System Sensing & Control Basics User Metabolic Rate
Power Supply
Local Temperature & Heat Flow Computer Control Emissivity Control text
• 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 Layer Spacing Control
Active Protective Garment
– Sets comfort temperature – Sets total heat flux 9
System Sensing & Control Effect of Sensing & Control Zone Angular Size
• Environmental Factors – Hot & Cold Extremes – Rapid Variation – Directional Sources • Sun, Hot Surfaces
• Crew Motion – Contact Pressure
• Suit Control Zones
Temperature Error (C)
– Maintain Thermal Comfort – Avoid Hot & Cold Touch Temperatures
60
1.2 Tmax T1
50
1
40
0.8 Temp Error, Tsink=-18 Temp Error, Tsink=10 Q relative, Tsink=-18 Q relative, Tsink=10
30 20
0.6 0.4
10
0.2
0
0 0
50
100
150
200
Zone Angular Width (Degrees)
Control & Sensing Zones
Inactive Zones
Head Torso Upper Arm Lower Arm Upper Leg Lower Leg Shoulders
Gloves Elbows Knees Boots
11 32 24 24 24 24 7
10 Total
146
Relative Heat Rejection
• System Control Needs
Sensing & Control Integration Options • Driving Factors – Robust Control • Simple signal and power interfaces • Minimize harnesses • Redundancy
• Control Basis – Total Heat Rejection – Skin Comfort temperature – Comfort Indicators
• Architecture Options – Centralized – Distributed
– Minimize Heat Leak – Minimize Power/Weight/Volume • Signal Transfer of Control Electronics – Analog/Sensor inputs – Data Bus, Wireless – Effector Drivers – Power Distribution 11
Control And Feedback • ~150 Zones, 5 layers => High I/O Count • Centralized Control Requires Complex Data Transfer, High Data ZONES 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 12
Control And Feedback Preferred Implementation •
Central Processor – Determines metabolic rate – Transmits inner wall T targets – Receives zone status & wall T
•
Networked dedicated zone controllers
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
13
Power Distribution • Current Technology Harnesses –
Weight, Reliability, Mobility Impacts
• “Smart” Garment Technology – Integrated Power and Signal Distribution
• Wireless Data Transmission, Local Control Components – Only Power Physically Connects Layers (Thermal Short) – Minimum Number of Connections
• Conductors woven in cloth layers • Conducting polymer layers
Wireless Comm Sensor
– Integrated Sensing, Data Terminal, Actuator Control Elements on Chip
Embedded Control Effectors
Fabric Effector Control and Input Power Layers
Power 14
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 15
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 16
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 Conductance (W/Sq.M)
– – – –
800 700 600 500 400 300 200 100 0 0
0.2
0.4
0.6
0.8
1
Compression (mm)
17
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 18
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 19
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 20
Mission Benefits Assessment • Substantial Launch Mass Savings
• ~ 3.5 Kg Reduction in EVA Carry Mass • Capability for Non-Venting Operations in Most Environments
Chameleon Suit Launch Mass Savings 10000 Launch Mass Savings (Kg)
– Savings For All Missions – EVA Intensive 1000 Day Class Missions Benefit Most
NASA Mars Design Reference Mission
1000 Units Launched
100
3 8 20
ISS Operations Lagrange Point Assembly & Lunar Visit Missions
10
1 1
10
100
1000
Number of 2 Person EVA's / Mission
– Science & Servicing Flexibility 21
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 22