A Chameleon Suit to Liberate Human Exploration of Space

Environments

Ed HodgsonHSSSI

October 30, 2001

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 HeatedSurfaces Insulated

Metabolic Heat Rejected ThroughTransmissive Surfaces With Low

Sink Temperature

MaximumInsulation Value

MaximumTransmissivity

MinimumEmissivity

MaximumLoft

Q Q

IntimateContact

MaximumEmissivity

3

Mission Needs Addressed

4

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

5

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

6

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

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

• 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

8

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

9

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

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

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

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

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

• 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

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

Power

Sensor

Wireless

Comm

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

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

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

)

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

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

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

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

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