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NASA CONTRACTOR REPORT 177411 

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ELECTROCHEMICAL CARBON DIOXIDE 

CONCENTRATOR SUBSYSTEM DEVELOPMENT 

E. P. Koszenski 

D. B. Heppner 

C. T. Bunnell 

(BASA-CE-1774 11) ELEClbOC€iEI!!ICAL CARBON IBS-163f3 

ClGXI(IDE COPCENTbdlOb ZCESYSSICI CEVELOPBEIT 

Pioal BeFOrt (life Systess) 92 p CSCL 05H 

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G3/54 01263S5 

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CONTRACT NAS2- 11783 

Fiarch 1986 

I 
NASA CONTRACTOR REPORT 1774'11 

ELECTROCHEMICAL CARBON DIOXIDE 

CONCENTRATOR SUBSYSTEM DEVELOPMENT 

E. P. Koszenski, D. B. Heppner and C. T. Bunnell 

Life Systems, Inc. 

Cleveland, OH 

Prepared For 

Ames Research Center 

under Contract NAS2-11783 

National Aeronautics and 

Space Administration 

Ames Research Center 

Moffetl Field, California 94035 
I- 

$ 

rc 

t 

TR-600-4 

ELECTROCHEMICAL CARBON DIOXIDE CONCENTRATOR 

SUBSYSTEM DEVELOPMENT 

Final Report 

E. P. Koszenski, D. B. Heppner and C. T. Bunnell 

March, 1986 

Distribution of this report is provided in the interest 

of information exchange. Responsibility for the contents 

resides in the authors or organization that prepared it. 

Prepared Under 

Contract NAS2-11783 

Life Systems, Inc. 

Cleveland, OH 44122 

for 

National Aeronautics and Space Administration 

Ames Research Center 
FOREWORD 

I 

. 

t 

The development work described herein was conducted by Life Systems, Inc. at 

Cleveland, Ohio under Contract NAS2-11783 during the period of January, 1984 

through March, 1986. The Program Manager was Dr. Dennis B. Heppner. The 

personnel contributing to the program and their responsibilities are outlined 

below: 

Per sonne 1 

Robert B. Boyda 

Charles T. Bunnell 

David N. Case 

Steve Czernec 

Roger B. Fell 

Steve P. Hendrix 

Dennis B. Heppner, 

John 0. Jessup 

James M. Khoury 

Eugene P. Koszenski 

Licia S. Kovach 

Joel B. Lantz, Ph.D. 

M. C. Lee, Ph.D. 

Ph.D. 

Dorothy A. Ruschak 

Marty Sudar 

Dan C. Walter 

Ed M. Zdankiewicz 

Area of Responsibility 

Supporting Technology Studies, System Analysis 

Program Testing, Data Reduction, Hardware 

Fabrication and Assembly 

Electronic Assembly and Checkout 

Mechanical Systems and Test Support Accessories 

Assembly 

Control/Monitor Instrumentation Hardware, 

Supporting Technology Studies 

Control/Monitor Instrumentation Software 

Program Manager, System Design and Analysis 

Electronic Assembly and Checkout 

Control/Monitor Instrumentation Hardware 

Project Management, Supporting Technology 

Studies, Quality Assurance 

Supporting Technology Studies 

Triple Redundant Relative Humidity Sensor 

Development 

Sabatier Reactor Subsystem Development, 

Supporting Technology Studies 

Contract Administration 

Program Testing and Data Reduction 

Design Engineering 

Supporting Technology Studies 

The contract's Technical Monitor is Dr. T. Wydeven, National Aeronautics and 

Space Administration, Ames Research Center, Moffett Field, CA. 
TABLE OF CONTENTS 

- PAGE 

LISTOFFIGURES ........................... iii 

LIST OF TABLES ............................ iv 

LIST OF ACRONYMS ........................... V 

SUMMARY ................................ 1 

PROGRAM ACCOMPLISHMENTS ........................ 2 

INTRODUCTION ............................. 3 

Background ............................ 3 

Program Objectives ........................ 4 

Report Organization ....................... 7 

THE ELECTROCHEMICAL CARBON DIOXIDE CONCENTRATOR SUBSYSTEM ....... 7 

General Description. ....................... 7 

Mechanical/Electrochemical Assembly ............... 7 

Electrochemical Carbon Dioxide Concentrator Module ..... 14 

Fluids Control Assembly ................... 14 

Coolant Control Assembly .................. 14 

Control/Monitor Instrumentation ................. 18 

General Description ...................... 18 

Hardware Description .................... 18 

Current Controller ..................... 22 

PROGRAM COMPONENT DEVELOPMENT ..................... 22 

Lightweight End Plates ...................... 24 

Air/Liquid Heat Exchanger Design ................. 24 

Coolant Control Assembly Diaphragm Modification ......... 31 

Subsystem Fail-safe Operation .................. 31 

Process Air Isolation Valves ................... 33 

Triple Redundant Reiative Humidity Sensor ............ 35 

Sabatier CO, Reduction Reactor .................. 44 

L 

t 

continuedi 
Table of Contents . cmtinued 

PROGRAM TEST ACTIVITIES ........................ 

One-Person CO Concentrator Subsystem Testing .......... 2 

49 

49 

Test Support Accessories .................. Endurance Testing ...................... CyclicTesting ....................... Conclusions of CS-1 Testing ................. 

49 

49 

55 

55 

Six-Cell EDCM Testing ...................... 55 

Testing ........................... Conclusions ......................... 55 

58 

Coolant Control Assembly Testing ................. 58 

Testing ........................... Conclusions ......................... 58 

58 

Fluid Control Assembly Testing .................. 58 

Testing ........................... Conclusions ......................... 62 

62 

Triple Redundant Relative Humidity Sensor Testing ........ 62 

Test Support Accessories .................. Testing ........................... Conclusions ......................... 

62 

66 

66 

Carbon Dioxide Reduction System Evaluation ............ 66 

Testing ........................... Conclusions ......................... 68 

68 

AIR REVITALIZATION SYSTEM INTEGRATION TECHNOLOGY STUDIES ....... 68 

Mechanical/Electrochemical Assembly Design ............ Control/Monitor Instrumentation Design .............. Impact of an Alternate CO Removal Subsystem ........... Evaluation to Minimize AR6 Blower Noise ............. Sizing and Characteristics Table for an ARS EDC ......... 

70 

70 

73 

75 .. 78 

CONCLUSIONS .............................. 80 

RECOMMENDATIONS ............................ 80 

REFERENCES .............................. 81 

ii 
LIST OF FIGURES 

FIGURE . 

PAGE 

1 

2 

3 

4 

5 

6 

7 

8 

9 

10 

11 

12 

13 

14 

15 

16 

17 

18 

19 

20 

21 

22 

23 

24 

25 

26 

27 

28 

29 

30 

31 

32 

33 

34 

35 

36 

37 

38 

39 

40 

EDC Single-cell Schematic .................. 5 

EDC Electrochemical Cell Functional Schematic With 

Reactions 6 

CS-1 Mechanical/Electrochemical Assembly .......... 8 

Model 220 C/M I (Front View) ................ 9 

CS-1 Process Block Diagram ................. 10 

CS-1 Mass and Energy Balance ................ 12 

CS-1 Mechanical Schematic .................. 13 

CS-1 Unitized Core and Composite Cell ............ 15 

Fluids Control Assembly ................... 16 

Coolant Control Assembly .................. 17 

CS-1 Modes and Allowable Mode Transitions .......... 19 

Model 220 C/M I (Internal Packaging) ............ 21 

CS-1 Current Controller ................... 23 

Mock-up of EDCM Lightweight Upper End Plate ........ 27 

EDC Air/Liquid Heat Exchanger Mechanical Design 

CS-1 Subsystem Fail-safe Operation Block Diagram ...... 34 

Isolation Valve Positive Closure Concepts .......... 36 

EDCM Isolation Valves .................... 38 

40 

Triple Redundant Relative Humidity Sensor 42 

45 

Sabatier CO Reduction Subsystem Concept .......... 46 

Sabatier CO Reduction Reactor ............... 47 

CS-1 TSA . Gas Sample Analysis ............... 51 

CS-1 Endurance Test Performance ............... 53 

Liquid-Cooled EDCM Test Stand ................ 56 

Six-Cell EDCM Long-Term Endurance Test ........... 57 

Coolant Control Assembly Test Stand ............. 59 

CCA Endurance Test Performance ............... 60 

Fluids Control Assembly Test Stand ............. 61 

FCA Endurance Test Performance ............... 63 

TRRHS Test Stand Mechanical Schematic ............ 64 

Triple Redundant Relative Humidity Sensor Test Stand .... 65 

Sabatier Reactor Test Scheme ................ 67 

With Sensors ........................ 71 

Steam Desorbed Amine CO Removal Process .......... 74 

.......................... 

Space Station Atmosphere Humidity Specification Ranges ... 28 

30 

CCA Accumulator Modification for Metal Bellows Diaphragm . . 32 

....... 

EDCM Isolation Valve Pressure Drop Versus Air Flow Rate ... 

Triple Redundant Relative Humidity Sensor and Monitor .... .......... 

2 

CS-1 TSA . ias/Coolant Supply ................ 50 

One-Person Air Revitaiization System Mechanical Schematic 

ARS-1 Mechanical Schemazic With Sensors . SDAS Substitution . 76 

iii 
TABLE 

LIST OF TABLES 

PAGE 

1 

2 

3 

4 

5 

6 

7 

8 

9 

10 

11 

12 

13 

CS-1 Design Specifications ................. 11 

CS-1 Mode Definitions .................... 20 

Characteristics ....................... 25 

Plates ........................... 26 

Isolation Valve Concept Characteristics ........... 37 

EDCM Isolation Valve Design Specifications ......... 39 

Triple Redundant Relative Humidity Sensor Design 

Specifications ....................... 43 

Sabatier Reactor Design Features .............. 48 

CS-1 Nominal Test Conditions ................ 52 

Sabatier Reactor Test Operating Conditions ......... 69 

ARS-1 Specification. Weight. Volume and Power Summary .... 72 

Lightweight End Plate Design Requirements/Desirable 

EDCM Lightweight End Plate Evaluation . Top/Bottom End 

ARS-1 SDAS-EDC Comparison .................. 77 

Component Sizing and Characteristics Summary for an ARS-1 

EDC ............................. 79 

iv 
LIST OF ACRONYMS 

li 

A/D 

ARS 

CCA 

C/M I 

CPU 

cs-1 

EDC 

EDCM 

EPROM 

FCA 

MfEA 

NASA 

ORU 

RAM 

RH 

S-CRR 

SDAS 

SFWE 

SFWES 

TRRH S 

TSA 

Analog/Digital 

Air Revitalization System 

Coolant Control Assembly 

Control/Monitor Instrumentation 

Central Processing Unit 

One-Person Carbon Dioxide Concentrator 

Subsystem 

Electrochemical Carbon Dioxide Concentrator 

EDC Module 

Erasable Programmable Read-only Memory 

Fluids Control Assembly 

Mechanical/Electrochemical Assembly 

National Aeronautics and Space Administration 

Orbital Replacement Unit 

Random Access Memory 

Relative Humidity 

Sabatier CO Reduction Reactor 

Steam Desorged Amine C02 Concentrator Subsystem 

Static Feed Water Electrolyzer 

Static Feed Water Electrolyzer Subsystem 

Triple Redundant Relative Humidity Sensor 

Test Support Accessories 

V 
SUMMARY 

Regenerative carbon dioxide removal techniques are needed to sustain man in 

space for extended periods of time. 

regenerative carbon dioxide removal system is the Electrochemical Carbon 

Dioxide Concentrator. This device allows for the continuous, efficient 

removal of carbon dioxide from the spacecraft cabin and delivery of the carbon 

dioxide premixed with hydrogen to a carbon dioxide reduction subsystem for 

subsequent oxygen recovery. 

The most promising concept for a 

The objectives of this program were to (1) advance the development of the 

Electrochemical Carbon Dioxide Concentrator Subsystem by developing related 

hardware components which improve overall performance and provide for ultimate 

flight application aboard the Space Station, (2) develop the Electrochemical 

Carbon Dioxide Concentrator Module, ancillary components and subsystem 

reliability data through extensive endurance testing, (3) establish a 

subsystem technology base for integration of the Electrochemical Carbon 

Dioxide Concentrator into an Air Revitalization System and (4) evaluate the 

impact of carbon dioxide and hydrogen flow from the Electrochemical Carbon 

Dioxide Concentrator Subsystem on a Sabatier Carbon Dioxide Reduction Reactor 

by fabricating a Sabatier Reactor and testing it with an Electrochemical 

Carbon Dioxide Concentrator Module. 

An extended test program was performed on previously developed hardware 

including the one-person Electrochemical Carbon Dioxide Concentrator Subsystem, the six-cell Electrochemical Carbon Dioxide Concentrator Module, a 

Coolant Control Assembly and a Fluids Control Assembly. A Triple Redundant 

Relative Humidity Sensor, a Sabatier Carbon Dioxide Reduction Reactor and 

Isolation Valves were fabricated, assembled and tested. A concept for 

subsystem fail-safe operation was also evaluated. 

The one-person Electrochemical Carbon Dioxide Concentrator Subsystem was both 

endurance tested and tested in a cyclic operating mode. Over 4,200 hours of 

endurance testing was achieved. The Subsystem carbon dioxide removal 

efficiency at a nominal carbon dioxide partial pressure of 400 Pa (3 mm Hg) 

averaged over 90% and cell voltages averaged 0.38 V during the course of the 

testing. A cyclic test program, simulating low-earth orbit operating conditions of 54 minutes "on" and 36 minutes "off," was performed. Approximately 

600 hours (400 cycles) were completed. The one-person Carbon Dioxide Concentrator Subsystem consistently demonstrated the capability of attaining carbon 

dioxide removal efficiencies of greater than 85% within six minutes of the 

transition from Standby operation ("off") to Normal operation ("on"). 

Endurance testing of the previously developed six-cell Electrochemical Carbon 

Dioxide Concentrator Module with unitized composite core construction 

continued during this program. Over 4,700 hours of additional operation were 

accumulated. After 5.5 years of combined operation and storage, the average 

carbon dioxide removal efficiency was typically 70% at nominal carbon dioxide 

partial pressures of 400 Pa (3 mm Hg) and cell voltages averaged 0.30 volts. 

Over 19,000 hours of endurance testing have been accumulated on this module. 

1 
A Fluids Control Assembly and its test stand completed over 9,000 additional 

hours of operation, which included over 13,000 test cycles. No failure of the 

Fluids Control Assembly was observed. 

at or above its design point levels for over 9,500 additional hours (over 

2,700 typical test cycles). 

The Coolant Control Assembly performed 

Satisfactory mechanical performance was achieved 

1 on both of these devices. 

A Triple Redundant Relative Humidity Sensor was designed, fabricated and 

program verified the design concept and accuracy of the sensor to within +3X 

over the range of 20 to 90% relative humidity. 

tested, along with a characterization and endurance test stand. The test 

A Carbon Dioxide Reduction Reactor based upon the Sabatier reaction was 

fabricated and integrated with the one-person Carbon Dioxide Concentrator 

Subsystem. The Sabatier Reactor was tested for 1,296 hours at nominal 

operating conditions of a carbon dioxide inlet rate of 1.04 kg/day 

(2.30 lb/day), a hydrogen inlet rate of 0.18 kg/day (0.40 lb/day) and a gas 

inlet temperature of 700 to 727 K (800 to 850 F). No decrease in reactor 

conversion efficiency was noted after 1,296 hours of operation with the 

hydrogen-to-carbon dioxide mole ratio maintained in the range of 3.36 to 4.05. 

A concept for implementing fail-safe operation of the Carbon Dioxide 

Concentrator Subsystem was designed, installed and effectively demonstrated. 

Isolation Valves were designed, fabricated and tested. The valves met the 

design requirement of (1) no leakage across the valve when closed and (2) a 

pressure drop across the valve of less than 124 Pa differential pressure 

(0.5 in water) when open. 

A series of Air Revitalization System integration reports were prepared. 

objectives of these studies were to define the requirements to integrate 

Electrochemical Carbon Dioxide Concentrator technology into an overall, 

integrated Air Revitalization System for Space Station application and 

identify areas of technology improvement which are required to meet flight 

qualified hardware status. These objectives were met. Additionally, design 

concepts were prepared for a new lightweight end plate and a versatile 

airlliquid heat exchanger. 

The 

All primary objectives of the program were successfully met. 

PROGRAM ACCOMPLISHMENTS 

The key program accomplishments were as follows: 

0 Completed over 4,200 hours of testing of the one-person capacity 

Carbon Dioxide (CO ) Concentrator Subsystem (CS-1) with C02 removal 

efficiencies averaging between 90 and 100%. Total test time on the 

CS-1 is now 6,035 hours. 

2 

2 
0 Completed over 9,000 hours of endurance testing of the Fluids Control 

Assembly (FCA), which integrates 11 gas handling components required 

by the CS-1 into a single unit. The total test time accumulated on 

the Fluids Control Assembly is now 18,500 hours. 

0 Completed over 9,500 hours of endurance testing of a Coolant Control 

Assembly (CCA), which integrates a coolant pump, diverter valve and a 

liquid accumulator into a single unit. The total test time 

accumulated on the CCA is now 18,925 hours. 

0 Completed an additional 4,700 hours of endurance testing on the first 

six-cell Electrochemical Carbon Dioxide Concentrator Module (EDCM) 

using unitized cores. The total test time accumulated on this module 

is now 19,375 hours. 

0 Completed design, fabrication and testing of a Triple Redundant 

Relative Humidity Sensor (TRRHS) and a characterization/endurance test 

stand. 

0 Completed design, fabrication and testing of EDCM Isolation Valves. 

0 Completed a series of short technology studies designed to evaluate 

the requirements for integrating an Electrochemical Carbon Dioxide 

Concentrator (EDC) subsystem into the Space Station integrated Air 

Revitalization System (ARS). 

2 0 Completed fabrication and integrated testing of a Sabatier CO 

Reduction Reactor (S-CRR). 

0 Completed design of an improved air/liquid heat exchanger. 

0 Completed an analysis for the development of lightweight end plates 

for the EDCM. 

INTRODUCTION 

Regenerative processes for revitalization of spacecraft atmospheres are 

essential for making long-term manned space missions a reality. An important 

air revitalization step is the collection and concentration of metabolically 

produced C02 for subsequent oxygen recovery. This report discusses advancement of an electrochemically-based subsystem which performs that function and 

development of ancillary components and related technology which enhance the 

performance of the subsystem. 

Background 

The EDC technique is the most promising technique for concentrating low level 

CO from the air without incurring large weight and volume penalties. The EDC 

removes CO continuously from low CO partial pressure in a flowing air 

stream. 

reduction subsystem for recovery of the oxygen (0 ) from the CO or vented, as 

2 

2 

2 Tie CO exhaust, premixed with hydrogen (H ), can be sent to a CO 2 2 

2 2 

3 
required. The EDC also generates electrical power which can be used in other 

life support processes (e.g., 0, generation by water electrolysis) if that is 

desired. L 

The CO removal process takes place in a module consisting of a series of 

electrochemical cells. Each cell consists of two electrodes separated by a 

matrix containing an aqueous carbonate electrolyte solution. Plates adjacent 

to the electrodes provide passageways for distribution of gases and electrical 

current. Figure 1 shows the functional schematic of the EDC cell. Figure 2 

details the specific electrochemical and chemical reactions which occur at the 

electrodes. As shown in Figure 2, the overall reaction is 

2 

O2 + 2C02 + 2H2 = 2C02 + 2H 0 + Electrical Energy + Heat (1) 2 

A theoretical maximum of two moles of CO can be transferred for one mole of 

0 consumed. The observed ratio of CO gransferred to 0 consumed represents 

tge removal process efficiency. A defined removal process efficiency of 100% 

occurs when 2.75 kg (6.05 lb) of C02 is removed for each kilogram (2.20 lb) of 

0 consumed. 

The EDC concept utilizing alkaline metal carbonate electrolytes has evolved at 

Life Systems, Inc. (Life Systems) under the National Aeronautics and Space 

Administration (NASA) sponsorship thr g ontracts NAS2-6118, NAS2-6478, 

NAS2-8666, NAS2-10204 and NAS2-11129. The concept has progressed from 

operation of single EDC cells to fabrication and testing of one-, three-, 

four- and six-person self-contained subsystems. These previous research and 

development activities resulted in demonstrated performance improvements in 

the electrodes, the electrolyte and the electrolyte-retaining matrix. These 

programs also included development of unique peripheral components and 

advancement of technology relating to EDC subsystem integration with other 

spacecraft air revitalization subsystems. 

2 2 

2 

PY-Pl F 

Program Objectives 

The objectives of this program were to: 

1. Endurance test the EDC subsystem and ancillary components to improve 

the subsystem and component reliability data. 

2. Develop new components and improve existing components to enhance 

overall subsystem performance. 

3. Identify the requirements for integrating the EDC into an Air 

Revitalization System for Space Station application. 

4. Expand the EDC technology base through the preparation of a series 

of short technology studies. 

The objectives of the program were met. 

(1-11) References cited at the end of this report. 

4 
n 

Process Air , I 1 

Inlet 

H, + CO, 

Outlet 

- Anode 

/ 

Electrolyte/ 

Matrix 

Liquid ~ ) Coolant 

Outlet 

Process Air 

Outlet 

H2 

Inlet 

FIGURE 1 EDC SINGLE-CELL SCHEMATIC 

5 
StartlStop Switch 

4- 

4ei 

2c0, 

/ 

2H,O / 

'> 

YH20 

Load Control 

/ 4H207 

2H,O 

2H,O 

2C03= 

-------- 

---- Carbonate - - - - 

- - - - Electrolyte - - - 

t 

4e4- 2H2 

\ 2c0, 

Cathode Anode 

Cathode Reactions: 

0, + 2H20 + 4e- = 40H40H-+ 2C02 = 2H20 + 2C03 = 

Anode Reactions: 

Overall Reaction: 

0, + 2C0, + 2H, = 2C0, + 2H,O + Electrical Energy + Heat 

FIGURE 2 EDC ELECTROCHEMICAL CELL FUNCTIONAL SCHEMATIC WITH REACTIONS 

6 
Report Organization 

This Final Report covers the work performed during the period January, 1984 

through March, 1986. The following major sections of this report present the 

technical results grouped according to: 

0 The Electrochemical Carbon Dioxide Concentrator Subsystem 

0 Program Component Development 

0 Program Test Activities 

0 Air Revitalization System Integration Technology Studies 

These sections are followed by conclusions and recommendations based upon the 

work performed and by the references cited in the text. 

THE ELECTROCHEMICAL CARBON DIOXIDE CONCENTRATOR SUBSYSTEM 

This section describes the design of the CS-1 subsystem. Testing is covered 

in a subsequent section. This section includes a general subsystem 

description including specifications and a schematic, a description of the 

Mechanical/Electrochemical Assembly (M/EA) and a description of the Control 

and Monitor Instrumentation (C/M I). 

General Description 

. The CS-1 Subsystem was fabricated, TTyembled and initially tested under a 

previous NASA Contract, NAS2-11129. The subsystem consists of a M/EA, 

shown in Figure 3 and a C/M I package, shown in Figure 4. 

The overall CO removal process and control scheme is shown in Figure 5. The 

M/EA includes a six-cell EDCM and all components required to sense and control 

gaseous and liquid fluid flows to and from the module. 

overall subsystem operation through the sensors and actuators located on the 

M/EA. The C/M I also monitors and interprets subsystem operational parameters 

and, through the use of a communication link, can display values on a separate 

video monitor. The C/M I can, through the communication link, provide for 

appropriate changes in operational modes in response to operator inputs or 

subsystem malfunctions. The general design specifications for the CS-1 

Subsystem, which include a capability for two operating modes ("Central," or 

Space Station operation and "Shuttle," or Shuttle Orbiter operation), are 

listed in Table 1. The overall fluid, electrical and thermal inputs and 

outputs for the CS-1 are illustrated in Figure 6. 

2 

The C/M I controls 

Mechanical/Electrochemical Assembly 

The M/EA is illustrated schematically in Figure 7. 

components are: 

The three primary 

0 The ECCM, which is the C02 concentration element; 

7 
L 

Six Cell EDCM 

FIGURE 3 cs-1 MECHANICAL/ELECTROCHEMICAL ASSEMBLY 

8 
H 

3 

c \ 

U 
@ 

ControllMonitor 

Instrumentation 

Input Power - - - - - - - 

Signals 

Cooling Air 

External SID - - -I- I - - 

I 

I 

-b ------ I 

--- -T-z I 

I 

I 

Data (for Display) 

External SID Signals 

Cooling Air 

I 

I 1 

I I I ,x- I I Sensor 

I 

I 

I 

Coolant 

H, Supply 

N, Supply (Purge On1 

Air Supply 

Coolant 

H,ICO, and N, Purge 

(Overboard Vent) 

cs-1 

Mechanicall 

Electrochemical 

Assembly 

I 

1 

Y ): 

-m Air Outlet I- - 

I 

I 

I I I 

- - - - - - - - -- 1 

CS-1 Subsystem Interface 

FIGURE 5 CS-1 PROCESS BLOCK DIAGRAM 

10 
TABLE 1 CS-1 DESIGN SPECIFICATIONS 

. 

Application 

Crew Size 

C02 Removal Rate, kgld (Ibld) 

Cabin pC02, Pa (mm Hg) 

Daily Average 

Maximum 

Cabin p02, kPa (psia) 

Cabin Temperature, K (F) 

Cabin Dew Point, K (F) 

Cabin Pressure, kPa (psia) 

Process Air Humidity Range, % 

Liquid Coolant 

Temperature (max), K (F) 

Flow Rate, kglh (Iblh) 

Flow Rate, kglh (Iblh) 

H2 Supply 

Pressure, kPa (psia) 

Relative Humidity, 'YO 

Purge Gas 

Type 

Pressure, kPa (psia) 

VAC 

VDC 

Electrical Power 

Gravity 

Noise Criteria, db 

Central 

1 

1 .o (2.2) 

400 (3.0) 

667 (5.0) 

22.1 (3.2) 

286 to 297 

(60 to 75) 

277 to 286 

(40 to 60) 

101 (1 4.7) 

See Figure 15 

280 (45) 

432 (950) 

0.007 (0.01 4) 

2.9 Stoichiometric 

(at 9.9 A) 

173 (25) 

0 to 75 

N2 

173 (25) 

115,400 Hz, 10 

28 

Otol 

55 

Shuttle 

1 

1 .o (2.2) 

667 (5.0) 

1.01 3 (7.6) 

22.1 (3.2) 

291 to 302 

(65 to 84) 

277 to 289 

(39 to 61) 

101 (1 4.7) 

20-80 

275 to 295 (35 to 71) 

432 (950) 

0.0024 (0.0053) 

1.2 Stoichiometric 

(at 9.0 A) 

173 (25) 

0 to 5 

N2 

173 (25) 

115,400 Hz, 10 

28 

0 to 1 

55 

. 

11 
C 

C 

- 

3 

ii 

z 

L 

c 

C 

0 

8 

4- 

c 

8 

i 

c 

a 

8 

e 

C 

- m 

0 

I F I" 

I T 

0 

I I 

I i, I 

I i 1 

12 
I 

I 

I 

I 

I 

Lr--- -- ----- 

I 

i 

ILL I 

N 

z- I 

c 

13 
2 0 An FCA, which regulates EDCM back pressure and Nitrogen (N ) and H 2 flows; and 

0 The CCA, which in conjunction with the liquidlliquid heat exchanger 

permits temperature regulation of the EDCM. 

In addition to the primary components the subsystem includes: (a) two 

filter/isolation valves (inlet and outlet), (b) two dry bulb temperature 

sensors, (c) two dew point temperature sensors (which when combined with the 

dry bulb temperature sensors are used to measure inlet and outlet relative 

humidity (RH)) and (d) a liquid/liquid heat exchanger. 

Electrochemical Carbon Dioxide Concentrator Module 

The primary component of the CS-1 is the advanced Carbon Dioxide Concentrator 

Module, the EDCM. The advanced EDCM is designed as a liquid-cooled module, 

composed of six unitized core composite cells which provide superior 

performance and differential pressure capabilities. Each composite cell 

consists of two electrodes (anode and cathode), a gas separator matrix, 

support screens, cell frames and coolant cavity covers. These items are 

illustrated in Figure 8. The selected number of cells, six, was based on the 

one-person CO removal rate of 1.0 kg/day (2.2 lb/day) and a current density 

of 21.3 mA/cm (19.8 ASF). The module has additional CO removal capacity if 

operated at higher current densities. This advanced design features integral 

process air manifolds which simplify interfacing with the process air. 

2 

2 

The principal M/EA components, besides the EDCM, are the FCA and the CCA. 

Each of these components is discussed in the following sections. 

Fluids Control Assembly 

The CS-1 EDCM requires monitoring and control of H flow, H /CO back pressure 

and N purge gas flow. These functions, which were previously performed by 

11 discrete components, have been integrated into a single, lightweight, 

low-volume FCA, shown in Figure 9. The FCA consists of a backpressure 

regulator mounted on a valve with a multiple function spool, a valve housing 

with built-in orifices to limit H and N flow rates, sensors for monitoring 2 2 upstream and downstream module pressures and sensors to monitor flow rates to 

and from the module. The FCA also has a manual override capability and a 

positive valve position indicator for use with the control electronics. 

2 22 

2 

Coolant Control Assembly 

Three elements are essential for temperature control of the liquid-cooled 

EDCM: a circulation pump, a diverter valve to regulate the proportions of 

module coolant flowing through and around the liquid/liquid heat exchanger 

(connected to a central coolant source) and a liquid/gas accumulator to 

accommodate coolant expansion/contraction. 

components have been incorporated into a single integrated assembly, the CCA, 

shown in Figure 10. The CCA performs the functions of maintaining a constant 

coolant flow rate to the EDCM and varying the coolant temperature. 

These previously discrete 

14 
w 

p: 

0 

V 

15 
b 

c 

m 

3 

0 

a, 

- 

a 

i 

0 

V 

16 
L.- Accumulator 

FIGURE 10 COOLANT CONTROL ASSEMBLY 

17 
Control/Monitor Instrumentation 

The function of the CS-1 C/M I is to provide for automatic mode and mode 

transition control, automatic shutdown for self-protection, monitoring of 

subsystem parameters and interface to ground Test Support Accessories (TSA) 

and data acquisition facilities. 

previously shown in Figure 4, represents a major reduction in weight, volume 

and power consumption from prior instrumentation. 

provides the CS-1 subsystem with four operating modes, as shown in Figure 11, 

and has separate normal modes corresponding to the operating conditions of 

either Shuttle Orbiter or Central (i.e., Space Station) application. The 

Shutdown Mode and the four operating modes are defined in Table 2. 

The CS-1 C/M I, termed the Model 220 and 

The Model 220 C/M I 

Gene ral D esc r ip t ion 

The CS-1 C/M I receives signals from and transmits signals to the M/EA sensors 

and actuators. Through these it controls and monitors subsystem pressures, 

flow rates, temperatures, cell voltages, current and valve positions in each 

operating mode. It implements each mode, whether initiated automatically or 

manually, and provides fail-safe operational changes to protect the CS-1 if 

malfunctions occur. 

the C/M I so that the operator need only press the mode enable and the desired 

mode buttons to initiate transition sequences. This control includes 

selection of different unit processes, selection of valve positions, 

sequencing of valve positions, sequencing of actuators and checking of 

parametric conditions as a transition (e.g., Shutdown to Normal Central) 

proceeds. 

The process operating mode control is fully automated by 

The C/M I uses erasable programmable read-only memory (EPROM) for its 

program storage. It also uses some random access memory (RAM) for data 

storage. This permits the access of the real-time data by an external monitor 

through a standard communications link, 

Hardware Description 

The 220 C/M I packaging is shown in Figure 12. 

assemblies : 

It contains five major 

1. 

2. 

3. 

4. 

A computer card cage containing the microprocessor's central 

processing unit (CPU) along with support cards (memory, 

analog/digital conversion (A/D), digital input and output, etc.); 

A power supply module for supplying 2 15 volts and + 5 volts from 

the input power of + 28 volts; 

A signal conditioning card cage and 11 signal conditioning cards for 

conditioning the sensor outputs and providing actuator drive 

signals; 

A power assembly for supplying those sensors and actuators which 

require drive current for their operation (dew point, flow and motor 

actuation) ; and 

18 
. Normal 

Shuttle 

(A) 

From All Modes 

Unpowered 

(D) 

- 

5Modes 

4 Operating Modes 

13 Mode Transitions 

9 Programmable, Allowed 

Mode Transitions 

4 Normal 

Shutdown Central 

( B) - (F) 

FIGURE 11 CS-1 MODES AND ALLOWABLE MODE TRANSITIONS 

A 

19 
TABLE 2 CS-1 MODE DEFINITIONS 

Mode (Code) 

Shutdown (B) The EDCM is not removingC02. Modulecurrent iszero, theCCApump isoff andallvalvesare closed. 

The system is powered and all sensors are working. The Shutdown Mode is called for by: 

Manual actuation 

Low EDCM individual cell voltage 

Low H2 pressure 

High H2 pressure 

Low outlet process air RH 

High outlet process air RH 

Second failure of triple redundant sensors for pressure, relative humidity, temperature and 

combustible gas concentration (capability only) 

Power on reset (POR) from Unpowered Mode D 

Mode transition from Shutdown Mode (B) to Normal Shuttle (A), Normal Central (F), or Purge (C) 

was not successful. All transitions to the Shutdown Mode except POR and Purge include a 

timed purge sequence as part of the mode transition sequence. 

Normal Shuttle (A) The EDCM is operating at the constant current density of 19.4 mAlcm2 (1 8.0 ASF) sized to perform 

the C02 removal function for one-person assuming an inlet pC02 level of 667 Pa (5.0 mm Hg). The 

Normal Shuttle Mode is called for by: 

Manual actuation 

Normal Central (F) The EDCM isoperating at a constant current densityof 21.3 mA/cm2(19.8ASF)sized to perform the 

C02 removal function for one-person assuming an inlet pC02 level of 400 Pa (3.0 mm Hg). The 

Normal Central Mode is called for by: 

Manual actuation 

Purge (C) The EDC is being purged with N2 through all H2 lines, H2 carrying module cavities and out through the 

vent line. Module current and the CCA pump are off. This is a continuous purge until a new mode is 

called for. The Purge Mode is called for by: 

Manual actuation 

Unpowered (D) No electrical power is applied to the EDC. Actuator positions can only be verified visually. Process air 

flow is stopped. There is no N2 or H2 flow. The Unpowered Mode is called for by: 

Manual actuation (circuit breaker) 

Electrical power failure 

CIM I failure as detected by the Built-in Diagnostic (B1D)circuit and supply power to theCIM I is 

interrupted 

20 
Power 

rssembly 

Com pu ter 

Assembly 

FIGURE 12 MODEL 220 C/M I (INTERNAL PACKAGING) 

21 
5. A front panel assembly with status indication and mode transition 

selection buttons. 

Current Controller 

The current controller, shown in Figure 13, provides a regulated current sink 

for the power generated by the EDCM and is packaged as a separate device. It 

is designed to be liquid cooled and located with the CS-1 M/EA. 

coolant source, which Jnterfaces with the CCA, also removes the waste heat 

from the current controller. Placement of the current controller near the 

EDCM reduces the length of electrical leads between the module and the current 

controller and thereby minimizes voltage drops. 

over prior EDC current controllers, not only in size reduction but also in the 

method and efficiency of controlling current and dissipating the EDCM-produced 

power. 

The central 

This unit is an improvement 

PROGRAM COMPONENT DEVELOPMENT 

A series of analyses, studies and developments of EDC-related hardware 

components were completed. The goal was enhancement of overall subsystem 

performance and reliability. 

advance the use or application of the EDC to the proposed Space Station, as 

opposed to defining components which permit demonstration of EDC technology 

feasibility, which has already been accomplished. The activities included 

preparing evaluations and conceptual designs for: 

These studies and developments were intended to 

1. Lightweight EDCM end plates; and 

2. An air/liquid heat exchanger; 

evaluation and demonstration of subsystem operational improvements including: 

1. A CCA using an improved gas/liquid separator diaphragm; and 

2. CS-1 Subsystem fail-safe operation; 

and design, fabrication and testing of: 

1. A new process air isolation valve; and 

2. A new TRRHS. 

Additionally, a S-CRR was fabricated for use in EDC testing and evaluation. 

Each of these developments is discussed in the following sections. 

22 
FIGURE 13 CS-1 CURRENT CONTROLLER 

23 
Lightweight End Plates 

Improvements which can reduce the weight of individual components and, 

subsequently, the overall subsystem are continually being evaluated. With 

respect to the EDCM, the module end plates are currently fabricated from 

stainless steel. They weigh approximately 36.3 kg (80.2 lb), about 80% of the 

total CS-1 weight. Use of lightweight metals, a metal honeycomb structure or 

nonmetallic materials could substantially reduce this weight and, consequently, the total subsystem weight. An analysis was performed on alternative 

end plate materials to determine comparative sizes and weights as well as 

practicality of fabrication and costs for end plates of adequate strength. 

The design requirements and desirable characteristics for lightweight end 

plates are listed in Table 3. The analysis included (1) investigation of 

suitable alternate materials, (2) calculation of mechanical characteristics 

and (3) configurational design. Four approaches were taken to select the 

candidate alternative materials for evaluation: (1) optimization of the 

present end plate weight, (2) use of lighter weight metals in place of 

stainless steel, (3) use of high strength nonmetallic composite materials and 

(4) use of honeycomb structures. 

The results of the analysis are summarized in Table 4. The 30% glass-filled 

polysulfone (Item No. 5 of Table 4) is the recommended material because (1) it 

has been previously used with success at Life Systems, (2) separate insulation 

plates are not required and (3) it has a cost effective approach. The 

lightweight end plates would be designed to incorporate the EDC subsystem's 

gas/liquid heat exchanger directly into the manifold ports or ducts. 

ducts would be bonded directly to the manifold ports and the interface 

plumbing for the FCA and CCA of the subsystem would be integral to the top end 

of the plate. The projected configuration of the upper end plate with its 

integrated heat exchanger, ducts and interface fittings is illustrated in the 

mock-up shown in Figure 14. The estimated weight savings of using the 30% 

glass-filled polysulfone over stainless steel are approximately 28.8 kg 

(63.6 lb). 

The 

Air/Liquid Heat Exchanger Design 

A key design feature of EDC technology is the use of a heat exchanger to 

precondition the inlet atmosphere before it is processed through the module 

cells. The preconditioning adjusts the KH of the inlet atmosphere to allow 

application of EDC technology over the full range of projected Space Station 

atmosphere conditions. 

air inlet air/liquid heat exchanger to be compatible with EDCs sized up to an 

eight-person capacity. 

An analysis and design was performed for a new process 

The range of inlet atmosphere conditions specified for the Space Station 

program is shown in Figure 15. For optimum EDC operation, an RH of 

approximately 55% is desired for atmosphere entering the module cells. To 

achieve this condition, the heat exchanger must efficiently adjust the 

temperature of the inlet atmosphere to approach the desired dew point, As 

shown in Figure 15, the worst-case condition occurs with inlet atmospheres 

24 
TABLE 3 LIGHTWEIGHT END PLATE DESIGN REQUIREMENTS/ 

DESIRABLE CHARACTERISTICS 

Requirements 

1. Lighter in weight than present stainless steel end plate design with no loss of 

2. Overall size, porting and interfaces compatible with current EDC cell frames 

3. End plate materials compatible with EDC electrolyte. 

4. No more than 0.015 mm (0.00s in) deflection at center of an end plate under 

5. End plate stress under pressurization less than 66% of allowable maximum 

6. Flight qualifiable material. 

7. Material bondablelsealable at interface ports. 

functionality. 

and insulation plates. 

cell pressurization forces. 

for the material used (>150% safety factor). 

Desirable C harac tens t ics 

1. Material amenable to established end plate fabrication procedures, such as 

machining, to minimize cost of these operations. 

2. Material has history of successful end plate application. 

3. Low raw materials cost. 

4. Eliminate separate insulation plate in the EDCM. 

5. Provides for integration of fluid components. 

25 
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26 
Coolant 

Control 

Assembly 

Fluids 

Control 

Assembly 

Air Inlet Duct with 

Integral GaslLiquid 

Heat Exchanger 

GI ass- Fi I led 

Air 

Outlet 

Duct 

' Polysulfone End Plate 

With Integral 

Interface Plumbing 

FIGURE 14 MOCK-UP C)F EDCM LIGHTWEIGHT UPPER END PLATE 

27 
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28 
which are hot and dry (lower right-hand corner of the specified range in 

Figure 15). Inlet atmosphere with a dry bulb temperature of 305 K (90 F) and 

a dew point temperature of 283 K (50 F) must be cooled to approximately 292 K 

(66 F) to achieve the desired KH. In comparison, an inlet atmosphere with a 

temperature of 305 K (90 F) and a dew point of 291 K (65 F) needs to be cooled 

to only 301 K (82 F). 

(0.85 l/sec (1.8 cfm)) and the cooling area large (465 cm (72 in ) per cell), 

the atmosphere will quickly adjust to the desired condition. Therefore, the 

job of the process air inlet air/liquid heat exchanger becomes one of 

minimizing the temperature adjustment required within the cell. 

Because the atmosphere flow throug3 each c 11 is small Fi 

Coolant flow through the EDC is controlled by the CCA. Coolant from the CCA 

returns to the module where it flows through the air-to-liquid heat exchanger 

and then in-parallel through each electrochemical cell. Since the temperature 

of the module will closely approach the temperature of the coolant and since 

all coolant flows through the heat exchanger, extremes in coolant temperature 

must be avoided. Therefore, the heat exchanger size cannot be reduced by the 

use of very cold coolant. 

therefore, be provided to achieve desired temperatures. Additionally, the 

circulating pump of the CCA is a major subsystem user of electrical power. It 

is desirable, therefore, to minimize the pressure drop of the circulating 

coolant through the module and thereby reduce the power requirement of the CCA 

and overall subsystem. 

Sufficient heat exchanger surface area must, 

The design developed under this contract is illustrated in Figure 16. Process 

atmosphere flows down through the heat exchanger across four rows of coolant 

tubes. Side walls along the length of the exchanger prevent process 

atmosphere from short-circuiting around the cooling surface. Coolant flows 

through the exchanger in two passes. In the first pass, coolant flows in 

parallel through the top five tubes, and in the second pass, in parallel 

through the bottom five tubes. The use of a parallel, two-pass flow minimizes 

the pressure drop of the coolant, in contrast to a single flow of coolant 

through each tube in series. A pressure drop savings of greater than 50% 

is anticipated. The exchanger illustrated in Figure 16 is designed to operate 

at a minimum capacity of three persons for a subsystem operating at worst-case 

conditions. The upper limit capacity of the unit can only be defined by a 

comprehensive test program. However, if testing were to demonstrate a need 

for additional heat exchanger capacity, the exchanger design could be readily 

adapted by adding a second cooling core above the one presently defined. 

The air/liquid heat exchanger designed and developed in response to the 

requirement provides a means of adjusting the inlet atmosphere conditions to 

those required for reliable EDC subsystem operation over the full range of 

specified Space Station atmosphere conditions. The design minimizes the 

pressure drop of the circulating coolant and reduces the power requirement of 

an EDC subsystem. In addition, the heat exchanger design can be expanded in a 

modular fashion for applications requiring added capacity. 

29 
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30 
Coolant Control Assembly Diaphragm Modification 

I’ 

In some applications of the CCA, particularly at high pressures, build-up of 

gas in the coolant loop of the CCA had been noted. Evaluations indicated this 

build-up of gas was due to diffusion of the gas across the diaphragm in the 

CCA accumulator. An effort was initiated to identify alternative diaphragm 

materials and diaphragm sealing approaches which would effectively retain the 

gas/liquid separation in the accumulator and prevent diffusion of gas across 

the diaphragm into the coolant loop. IA variety of polymeric materials were evaluated with respect to their 

permeability to gases at different pressures, elasticity and elastic memory, 

sealing characteristics, durability and maintainability. Polymeric materials 

compatible with CCA operating conditions and environment demonstrated some 

permeability over time to oxygen and other gases. Metallic-coated polymers 

did not exhibit expansion and sealing characteristics required over a wide 

range of CCA operating conditions. The ideal characteristic would combine the 

elasticity of polymeric diaphragms with the resistance to diffusion and 

permeability afforded by metallic diaphragms. These characteristics are 

afforded in stainless steel bellows-type diaphragms. The stainless steel 

diaphragm provides excellent operating environment compatibility, weldability, 

flexibility and is engineered for pressurized and vacuum applications. 

The accumulator of a CCA was redesigned to accommodate a commercially 

available stainless steel bellows diaphragm. To ensure leak-tight integrity, 

welding the stainless steel diaphragm into the accumulator was favored over a 

compression seal. 

illustrated in Figure 17. The CCA using the stainless steel bellows diaphragm 

was tested. The CCA cavity was pressurized and the coolant loop of the CCA 

was examined for gas build-up. No gas build-up was detected and no loss of 

coolant fluid was noted, verifying the sealing capability and nonpermeability 

of the stainless steel bellows diaphragm for the CCA. 

The original and modified accumulator designs are 

Subsystem Fail-safe Operation 

A hardware requirement, particularly at the subsystem and system levels, for 

application to the Space Station will be the capability to effectively 

configure the hardware into a fail-safe operating or shutdown mode in the 

event of a malfunction or failure (e.g., loss of main system power, loss of 

operating fluids, loss of system computer control, etc.). The objective of 

configuring hardware into a fail-safe mode is to prevent operation of the 

hardware under conditions which could result in damage to the hardware, 

ancillary components or adjacent equipment or injury to personnel. A task was 

included in the program activities to establish and incorporate fail-safe 

operation into the CS-1 Subsystem. Consideration for assuring fail-safe 

operation of the FCA and provisions for shutting off the H and purging the 

CS-1 with N were included. 

successfully demonstrated. 

A fail-safe technique was implemented and 2 

31 
A. Original CCA Accumulator Design - Scale: Full Size 

Pleated Metal 

Bellows Diaphragm 

I ////////////A 

B. Modified CCA Accumulator Design - Scale: Full Size 

FIGURE 17 CCA ACCUMULATOR MODIFICATION FOR METAL BELLOWS DIAPHRAGM 

32 
The approach to this activity included (1) defining the requirements for 

subsystem fail-safe operation, (2) defining the hardware and software needed 

to demonstrate the fail-safe operation, (3) defining the requirements to 

integrate the hardware and software with the CS-1 subsystem and (4) implementing and demonstrating the fail-safe technique. The principal failure modes 

requiring fail-safe subsystem shutdown were identified as (1) loss of system 

power (main power failure), (2) loss of computer control functions (C/M I 

failure) and (3) detection of out-of-tolerance operating conditions. In the 

case of a main power failure, a secondary power source would be required to 

configure the subsystem into a fail-safe operating mode. In the case of a 

C/M I failure where main power is still available, a secondary power source is 

not required but an independent, supplementary shutdown control is needed. 

For a failure or malfunction involving the module or component hardware, the 

C/M I monitors subsystem operating interfaces and is is designed to initiate a 

controlled transition to shutdown when an out-of-tolerance operating condition 

is detected. 

The fail-safe demonstration concept is illustrated in the block diagram of 

Figure 18. The principal component of the fail-safe mechanism is 

supplementary shutdown circuit, which continually monitors the subsystem for a 

"C/M I alive" signal. In the event of main system power failure, the C/M I 

alive signal from the C/M I to the supplementary shutdown circuit is lost. 

The supplementary shutdown circuit, using power supplied by the secondary 

power source, will (1) move the FCA from H2 flow to N permitting nitrogen 

purge of the module and (2) shut off current to the module. For the failure 

mode where main system power is temporarily lost, the supplementary shutdown 

circuit will function in the same manner. However, upon the resumption of 

supplied power, the subsystem's C/M I will take over and begin a normal 

transition to shutdown. For the case where a C/M I failure occurs but main 

power is maintained, the C/M I alive signal to the supplementary shutdown 

circuit will be lost and the supplementary shutdown circuit will move the FCA 

to N purge and shut off subsystem current as previously described. 

An electronic circuit designed to accomplish this function was fabricated and 

installed in the CS-1 Subsystem. The failure modes previously described were 

manually initiated. In each case, the supplementary shutdown circuit 

successfully moved the FCA to the nitrogen purge position and shut off 

subsystem current. The time required to move the FCA to the nitrogen purge 

position was approximately 1.5 seconds following initiation of the failure 

mode. 

2 

2 

Process Air Isolation Valves 

The EDC technology advancement activities include an on-going effort to 

improve the overall characteristics and reliability of the EDC subsystem. One 

improvement would be to provide hermetic sealing of the EDCM in the presence 

of a vacuum, as could occur during cabin decompression. 

isolating the EDCM air inlet and outlet manifolds from the cabin environment. 

The filter/isolation valves presently used in the CS-1 subsystem provide gross 

This requires 

particulate filtering 

provide total sealing 

design, fabricate and 

and limited isolated via manual actuation but do no; 

against a vacuum. The objective of this effort was to 

evaluate a valve that incorporates this capability. 

33 
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34 
The primary objectives were to size a valve orifice large enough that the 

pressure drop through to the valve did not exceed 124 Pa differential ressure 

(0.5 inc es of water) at a nominal four-person air flow rate of 1.22 m /min 

(43.2 ft /min) and a sealing capability whjch would limit she leakage rate 

across the valve to not more than 0.010 cm /day (0.0006 in /day). Several 

concepts for a suitable valve were investigated and evaluated. These are 

illustrated in Figure 19 and compared in Table 5. As can be seen from 

Table 5, an isolation valve employing a butterfly valve offered the best 

compromise between performance (sealing against vacuum), simplicity, 

manufacturability and adaptation to motorized actuation. 

3 9 

Design of an isolation valve using the butterfly valve approach was completed. 

Two isolation valves were fabricated per this design and are shown in 

Figure 20. The design specifications for the isolation valve are given in 

Table 6. 

The fabricated isolation valves were tested to evaluate their pressure drop 

and sealing characteristics. The pressure drop across the valves met the 

design require ents and is i lustrated in Figure 21. At a process air flow 

rate of 1.23 m /min (43.2 ft /min), the pressure drop across the valve was 

only 107 Pa differential pressure (0.43 in water). The sealing 

characteristics of the isolation valves were evaluated by isolating a 

differential pressure across the butterfly valve. With a differential 

pressure of 103 kPa (15 psid) across the valve, no leakage or pressure decay 

was noted. The isolation valves demonstrated the capability to provide a 

positive seal and zero leakage from internal to external and are sized to 

permit air flows from a nominal one-person up to four-person capacity EDC 

subsystems, although there are no design limitations in the valve to prevent 

usage for larger person-level systems (e.g., up to eight-person subsystems). 

The filter/isolation valve will provide for isolation of the EDCM inlet and 

outlet both during normal operation and periods where the ambient environment 

may be reduced to zero absolute pressure. 

7 3 

Triple Redundant Relative Humidity Sensor 

A requirement for manned spacecraft is monitoring and control of the humidity 

content of the crew quarters and work areas. A variety of standard techniques 

for monitoring RH include (1) direct measurement of the RH and (2) measurement 

of the dew point and dry bulb temperatures and subsequent calculation of the 

RH. However, hardware available to perform the RH monitor function, either by 

direct sensing of the RH or by dew point and dry bulb temperature comparisons, 

tends to be large, inaccurate, unreliable or requires support equipment. 

Improved measurement of RH is, therefore, a needed technology goal for the 

Space Station. Additionally, the EDC subsystem requires monitoring of RH in 

order to control its operation. A task was performed to develop an improved 

RH sensor which would meet Space Station application requirements as well as 

be incorporated into EDC Subsystems. 

35 
1. Globe Valve 

6-3 

fl 

fl 

2. Gatevalve 

3. Butterfly Valve 

p7 

5. Pinch Valve 

4. Ball Valve 

6. Diaphragm Valve 

FIGURE 19 ISOLATION VALVE POSITIVE CLOSURE CONCEPTS 

36 
TABLE 5 ISOLATION VALVE CONCEPT CHARACTERISTICS 

Valve Sealing@) Difficulty 

- NO. Style Ability Complexity@) Actuation@) of Manufacture SizdQ cost 

1 Globe High High Rotation and High High High 

2 Gate Medium Low Transl at ion Mzdium Medium High 

3 Butterfly High Low Rotat ion Low Medium Medium 

4 Bal I High Low Rotation Medium High Medium 

5 Pinch Low Medium Translation High High High 

6 Di ap hrag m Medium Medium Rotation and High High High 

Transl at ion 

Translation 

(a) Medium = Leakage rate of 0.01 cm3 (O.OOO6 in3) airlday at 103 kPa (15 psi) differential pressure. 

(b) Based on number of seals, moving parts, sealing surfaces and total number of discrete parts. 

(c) Of final mechanism to effect seal. 

(d) Medium = 737 cm3 (45 in3) based on 7.6 cm (3 in) inletloutlet ports, 10.2 cm (4 in) length and motor of 279 cm3 (17 in3) 

37 
FIGURE 20 EDCM ISOLATION VALVES 

38 
TABLE 6 EDCM ISOLATION VALVE DESIGN SPECIFICATIONS 

OPERATING INTERFACES 

The data shown below are for a nominal four-person subsystem. The nominal range covers from zero 

to an eight-person subsystem. 

Nominal Range 

Air flow, at standard temperature and 1,223 0 to 2,447 

Pressure drop, Pa (in of H20) 124 0 to 249 

Air leaka e in closed position, 0.01 0 to 0.03 

cm31d (in 9 Id) (0.ooOs) (0 to 0.0018) 

Pressure Differential, kPa (psid) 

Temperature, K (F) 

PERFORMANCE CHARACTERISTICS 

Working Fluids 

Power, W 10 (momentary) 

Time to open and close, sec 

Particulate Removal Capability 

Min. particulate size, cm (in) 

equiv. screen mesh size 6.0 

Gravity Environment, g 

pressure, llmin (cfm) (43.2) (0 to 86.4) 

(0.5) (0 to 1 .O) 

Open 0.069 (0.01) 0 to 0.206 (0 to 0.03) 

Closed 6.9 (1 .O) 0 to 103 (0 to 15) 

294 (70) 278 to 305 (40 to 90) 

Air (N2,02, COP, water vapor) 

1 .o 

0.31 8 (0.1 25) 

0 to 1 

RELIABILITY: 

Failure Rate 

Failure per three years 

MTBF, years 

Installed redundancy 

Service Life, years 

1 

10 

None 

10 

Safety 

The EDCM isolation valve shall not present a hazard to service or operating personnel. 

PHYSICAL CHARACTERISTICS 

Weight, kg (Ib) 

Volume, cm3 (in31 

Dimensions, cm (in) 

Appearance 

MATERIALS 

Metal I ic 

Nonmetal1 ic 

ELECTRICAL CHARACTERISTICS 

1.4 (3.0) 

81 9 (50) 

8.6 x 5.3 x 15.2 (3.4 x 2.1 x 6.0) 

Compact and Aesthetic 

Aluminum, stainless steel, 

bronze 

Viton, ethylene-propylene, teflon 

Motor Voltage, VDC 

Maximum Current, A 

Valve Position Indicator 

24 

0.4 (momentary) 

Relay Contacts 

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40 
The objective of this effort was to fabricate a TRRHS having triply redundant 

sensor elements to improve reliability, repeatability and accuracy. Direct 

measurement of RH was desired, allowing the sensor's output to be more 

compatible with the hardware that is used to control the RH, particularly in 

the EDC. Overall size, configuration and performance were considered to be 

the significant improvements desired over existing techniques. The initial 

specifications used to compare and evaluate candidate sensor techniques were 

generated based on the Space Station application projected for the TRRHS, also 

noting that a TRRHS which met the Space Station specifications would also meet 

EDC applications. 

An evaluation of the most critical component of the TRRHS, the relative 

humidity sensing element, was completed. 

factors in selection of a sensing element: 

The following criteria were key 

0 Resistance to extremes in RH 

0 Resistance to contaminants 

0 Overall small size of the sensor element 

0 Ability to recover from exposure to 100% RH 

0 Fast response time 

0 Reliability, repeatability and accuracy 

0 Wide temperature range compatibility 

0 Low hysteresis 

Three types of sensor elements were evaluated. 

impedance to measure RH; a second type used electrical resistance to measure 

RH and the third type used electrical capacitance to measure RH. Of the three 

candidate sensor elements evaluated, the sensor which determined RH by 

electrical capacitance was selected since it most closely met the design 

criteria. 

One type used electrical 

A TRRHS using the capacitance-type element was fabricated and assembled and is 

shown in Figure 22. The TRRHS consists of a main housing which has the three 

sensing elements mounted in one end and a commercially available electrical 

connector mounted at the opposite end. A sensor element cover, which is 

slotted to allow passage of the atmosphere sample stream over the sensor 

elements, attaches to the sensor housing and protects the sensor elements from 

contact damage. When completely assembled, the TRRHS is approximately 12 cm 

(4.7 in) long (including the electrical connector) and approximately 1.8 cm 

(0.7 in) in diameter. The design specifications for the TRRHS are presented 

in Table 7. 

41 
FIGURE 22 TRIPLE REDUNDANT RELATIVE HUYIDITY SENSOR 

42 
TABLE 7 TRIPLE REDUNDANT RELATIVE HUMIDITY SENSOR 

DESIGN SPECIFICATIONS 

Operational Characteristics 

RH Range, YO 

Dew Point Temperature Range, K (F) 

Temperature Range, K (F) 

Pressure, kPa (psia) 

Accuracy, YO RH 

Stability (at 50% RH) 

Repeatability, O/O RH 

Reproducibility, O/O RH(a) 

Linearity, Max., O/O RH Deviation from a straight 

line over range Response Time, sec 

Step Increase (63% FS) Step Decrease (90O/0 FS) 

Hysteresis, from 540% RH, o/o 

Display Resolution, O/O RH 

Temperature Sensitivity, O/O RHlF 

Air Velocity Sensitivity%RHlmlsec (ftlsec) 

Air Pressure Sensitivity, O/O RHlpsia Shelf Life, yr 

Operating Life, yr 

Re1 iabili t y (MTBF), hr 

Sensor Orientation Sensitivity, O/O RH 

Electrical Characteristics 

Short-term, O/O RH changelmo Long-term, YO RH changelyr 

Power (total), W 

Power Supply Voltage, VAC 

Power Supply Frequency, Hz 

Front Panel Controls 

Display(s) 

Indicators 

Control Adjustments 

Calibration Set 

Sensor Cable 

Physical Characteristics 

Weight, kg (Ib) 

Volume, cm3 (in3) 

Dimensions, cm (in) 

Mounting 

Electronic Package 

Weight, kg (Ib) 

Volume, cm3 (in3) 

Dimensions, cm (in) Mounting 

Environmental Limits 

Air Velocity, mlsec (ftlsec) 

Air Pressure, kPa (psia) Ambient Temperature, K (F) 

Sensor 

Electronics Package Gravity, g 

Maintainability 

Line Replaceable Components 

Replacement Time, hr 

Sensor 

Electronic Package Special Tools 

Rear Panel 

Sensor 

20-90 

253321 (-4-1 18) 

263-343 (1 4-1 58) 

34-1 38 (5-20) + 3 over range 

23 

+ 10 

+2 

*3 

+5 

<1 

<2 

+1 

0.1 

0.05 

0.03 (0.1) 

0.2 

5 

2 

10,Ooo 

24 

10 

115 

60 

RH:3 Digit LCD 

Power On, RH Overlimit, RH Override 

RH Overlimit 

20-Turn Trim Potentiometedb) 

25-Pin AMP Connector 

0.1 (0.2) 

29.5 (1.8) 

1.8 dia x 12.1 L (0.7 dia. x 4.75 L) Boss-Mounted 

2.7 (6) 

30.5 x 11.4 x 27.9 (12 x 4.5 x 11) 

Free Standing or rack mounted 

9,734 (594) 

06.1 (0-20) 

34-1 38 (5-20) 

263-343 f 1 4-1 58) 

277-31 1 (40-1 odj 

0-2 

Sensor, Electronics Package 

0.2 

0.3 

None 

(a) Variation from one instrument to another. 

(b) Internal to electronics package. 

43 
A control electronics package, shown in Figure 23, was also designed and 

fabricated. This TRRHS monitor provides for measurement and display of the 

RH. 

voltage for each of the sensing elements. Each sensing element is continuously monitored. 

that the capacitance of each sensor is proportional to the RH. The output of 

each sensing element is amplified and further signal conditioned to yield an 

output which is linearly proportional to the RH and displayed on independent 

liquid crystal display meters. 

control circuit which allows the operator to select and set a predetermined RH 

limit (e.g., 95% RH). If any one of the sensing elements detect this level of 

RH, the monitor will send a shutdown signal to the TRRHS test stand. The 

TRRHS test stand and testing are discussed in subsequent sections of this 

report. 

The monitor contains an oscillator circuit which provides an excitation 

Signal conditioning for each sensor is designed such 

The monitor also contains an RH overlimit 

Sabatier CO Reduction Reactor 2 

2 The EDC subsystem concentrates C02 removed from cabin atmosphere into an H 

stream. 

to reduce the C6 and recover water from the reaction product stream. 2 technique which can be used to accomplish this is a C02 reduction process 

based upon the Sabatier reaction. A task was included in this program to 

evaluate the effects of product gases exhausting from the EDC on a CO 

reduction reactor based upon the Sabatier reaction. 

This H /C02 stream undergoes further processing downstream of the EDC 

A 

2 

The Sabatier Reactor is depicted schematically in Figure 24. 

reactant mixture from the EDC (containing water vapor at a dew poing less than 

289 K (60 F)) enters the Sabatier Reactor. 

equation shown in Figure 24. The CO reduction reaction generates heat which 2 is removed by the incoming reactant gases and cooling air. A decreasing 

temperature profile from the inlet of the reactor to the outlet of the reactor 

is maintained so that the best reactor efficiency is obtained. The methane 

(CH4) and water vapor formed along with excess reactants are subsequently 

delivered to a condenser/separator where the water vapor is condensed, removed 

from the gas stream and stored in an accumulator. The accumulator is 

periodically emptied as required while the CH and excess reactants, after 

being cooled in the condenser/separator, exhaust the subsystem to overboard 

vent. 

The H /C02 

The CO reacts with H2 via the 2 

4 

To enable downstream testing with the EDC, a one-person S-CRR was designed and 

fabricated. It is shown in Figure 25. This one-person S-CRR, which is based 

on a previously-developed prototype design, optimizes the prototype design 

with respect to the length-to-diameter ratio, mechanical and electrical 

interfaces and overall subsystem maintainability. 

which weighs 2.4 kg (5.3 lb) (with catalyst) and which has 56% fewer parts 

than the prototype version. These design features are summarized in Table 8. 

The EDC testing with the Sabatier Reactor is discussed in a subsequent 

section. 

The end result is a reactor 

44 
FIGURE 23 TRIPLE REDUNDANT RELATIVE HUMIDITY SENSOR AND MONITOR 

45 
H2/C02 

(+ H20 vapor) 

From EDC * 

Cooling 

Air 

. CHdH20 (vapor3 Sabatier Reactor (+ excess reactants) 

C02 + 4H2 + CH4 + 2H20 + Heat 

_r 

FIGURE 24 SABATIER C02 REDUCTION SUBSYSTEM CONCEPT 

46 
FIGURE 25 SABATIER C02 REDUCTION REACTOR 

47 
TABLE 8 SABATIER REACTOR DESIGN FEATURES 

1. Optimized catalyst bed - LID ratio, catalyst type ratio and quantity. 

2. Single plane interface at one end for mechanical and electrical interfaces. 

3. Fewer total parts: 

Prior design - 77 parts 

Current design - 43 parts 

4. Two-stage heater for development testing - secondary heater may 

5. Cooling air flow controlled in two different zones. 

be removed after testing. 

6. Maintainable heater - four screw removal. 

7. Maintainable temperature sensors in wells. 

8. Simplified bed loading with wafer springs. 

9. Reactor line maintainable using quick-release strap clamp and CPV 

fluid fittings 

48 
PROGRAM TEST ACTIVITIES 

Testing was performed as part of the overall program activities. The testing 

included continued endurance testing of the CS-1 subsystem, the six-cell EDCM, 

the FCA and the CCA and cyclic testing of the CS-1. Performance evaluation 

tests were completed on the TRRHS and the Sabatier Reduction Reactor. Results 

of each of these test activities are discussed in the following sections. 

One-Person CO Concentrator Subsystem Testing 2 

Over 4,800 hours of CS-1 testing (both endurance and cyclic) were completed 

under this contract. As discussed in the following sections, the performance 

of the CS-1 was excellent. 

Test Support Accessories 

The CS-1 subsystem TSA, which were developed under previous contracts and were 

refurbished for the current program, are shown schematically in Figures 26 and 

27. Figure 26 illustrates the gas/coolant supply schematic and Figure 27 

shows the arrangement for gas sample analysis. Performance of the CS-1 based 

on air side (e.g., pC0 ) measurements and H /CO exhaust measurements (e.g., 

flow rate) was determined with this equipment. 2The CS-1 TSA provides the 

following: 

2 2 

1. 

2. 

3. 

4. 

5. 

6. 

2 Process air at the desired flow rate, dew point, temperature and pC0 

levels. 

Nitrogen and H 

Coolant simulating a central spacecraft coolant source. 

gases at the desired pressures and flow rates. 2 

Electrical power at 28 volts for the C/M I and 115 volts, 400 Hz for 

the CCA pump. 

Electrical circuitry to permit shutdown interface between the CS-1 

and the TSA. 

Gas analysis equipment for meeting CS-1 performance. 

Endurance Testing 

The CS-1 subsystem was endurance tested for an additional 4,225 hours (176 

days) beyond the test time completed under the previous contract. 

endurance testing demonstrated the ability of the module to maintain 

acceptable performance while running continuously. Conditions were typically 

maintained within the ranges listed in Table 9. Performance during the entire 

4,225 hours of continued endurance testing is plotted in Figure 28. 

removal efficiency averaged greater than 90% and cell voltage averaged 

0.38 V even with pC02 and process air inlet RH excursions outside the nominal 

operating conditions. The stability and reliability of the electrochemical 

cells are evidenced by the results of this testing. 

The 

The C02 

49 
C-- k 

-- 

I 

I 

i 

I 

I 

4 

\D 

N 

w 

k 

50 
c 

C 

8 

E+ 

m 

I L 7 

U 

I 

I 

I 

v1 

V 

w 

c4 

5 

2 I 

iki h I 

M 

3- 

51 
TABLE 9 CS-1 NOMINAL TEST CONDITIONS 

Current, A 

Process Air 

Flow Rate, dm3ls (cfm) 

pC02, Pa (mm Hg) 

Relative Humidity, YO 

Dew Point, K (F) 

Dry Bulb, K (F) 

Hydrogen 

Flow Rate, kglh (Iblh) 

Pressure, kPa (psia) 

Module Backpressure, kPa (psia) 

Purge Gas 

Type 

Pressure, kPa (psia) 

Coolant 

Temperature, K (F) 

9.9 

5.1 (10.8) 

400 (3.0) 

56-64 

283-286 (50-56) 

291 -293 (64-68) 

0.006 (0.01 4) 

172 (25) 

34.5 (5.0) 

Nitrogen 

207 (30) 

275-277 (36-40) 

52 
I 

v) 

U 

co 

N 

w 

53 
8 

t 

8 

-?' 

(3L 

r 

8 

cv 

a 

al 

3 

C 

-4 

U 

U 

I 

Q) 

N 

al 

8 

t 

N 

8 

-! 

cv 
The total accumulated endurance test time on the CS-1 subsystem, including the 

testing completed under this contract and the previous contract, is 6,035 hours. 

Cyclic Testing 

Over 600 hours (25 days) of cyclic testing was performed at subsystem baseline 

conditions. The cyclic testing was designed to simulate operating conditions 

with respect to light side, dark side Space Station orbit characteristics. To 

achieve this, the CS-1 subsystem C/M I software was modified to provide a 

"Standby" operating mode in place of the "Normal Shuttle'' operating mode. 

Through the C/M I, the CS-1 subsystem cycled between Normal operation and 

Standby. A test cycle was defined as 54 minutes in Normal operation (on, or 

light side of orbit) and 36 minutes in Standby operation (off or dark side of 

orbit). Approximately 400 test cycles were completed during the 600 hours of 

cyclic testing. The CS-1 consistently demonstrated the ability to achieve 

baseline CO removal efficiency requirements within six minutes following the 

transition Zrom Standby to Normal. 

Conclusions of CS-1 Testing 

The results of the endurance and cyclic tests verified the predictable, 

reproducible, high-level performance of the EDC subsystem. The test results 

verified the concept of the unitized core and liquid-cooled cells and the 

preconditioning of the EDCM inlet air using the air/liquid heat exchanger. 

Six-Cell EDCM Testing 

Long-term endurance testing of the six-cell EDCM with the developmental 

unitized cell cores continued under this contract. The objective of the 

testing was to expand the data base for the liquid-cooled, unitized core EDC 

concept. The test stand used to perform the continued endurance testing of 

the six-cell EDCM is shown in Figure 29. 

under a prior program and was refurbished for the testing under this program, 

provides for unattended EDCM operation for long periods. 

electronic packages which automatically control and monitor the GO 

concentrating process and protect against failures. 

instrumentation for monitoring operating temperatures, pressures, RHs, cell 

current and cell voltages. 

This test stand, which was developed 

It incorporates 

The test stan3 includes 

Test inn 

Figure 30 shows the EDCM endurance test data obtained from an additional 4,728 

hours (197 days) of testing under the current program. In spite of over 

2.2 years of total accumulated test time and an additional 3.3 years of module 

storage, cell voltages still averaged almost 0.30 V and the average CO 

removal efficiency was still approximately 70% during this test cycle. 

Although these values have dropped off somewhat since testing of this module 

began 5.5 years ago, the development unitized cores continue to perform the 

CO removal function. 

2 

2 

55 
L 

5 

FIGURE 29 LIQUID-COOLED EDCM TEST STAND 

56 
w 

U 

3 n 

z 

W 

E 

F 

0) 

C 

3 

w 

H 

I 

c3 

z 

0 

I4 

c 

U 

W 

n 

0 

m 

w 

57 
Conclusions 

The total test time accumulated on this EDCM over a 5.5 year period is now 

19,375 hours (807 days). 

have demonstrated signiffcant performance capability and reliability, have 

verified the unitized core concept and its application to electrochemical CO 

concentration and have provided an excellent data base for the new and 

improved unitized cores which are now part of the baseline design of EDC 

modules. 

The developmental unitized cores used in this module 

2 

Coolant Control Assembly Testing 

Endurance testing of the CCA, which was fabricated and initially tested under 

a prior program, continued under the current program. Figure 31 shows the 

test stand used to perform the continued endurance testing of the CCA. This 

test stand, which uas developed under a prior program and was refurbished for 

the testing under this program, provides the instrumentation required to 

exercise the CCA through a range of conditions simulating various EDCM heat 

loads. 

temperature. 

The CCA varies the coolant flow in response to the simulated varying 

Testing 

Figure 32 shows the performance of the CCA over the 9,550 hours (398 days) o 

endurance testing completed under this program. The parameters selected for 

illustrating performance are the following: (1) total mass flow rate, 

(2) developed pump head pressure, (3) temperature of the heat source which the 

CCA is trying to maintain and (4) cycle time of the heater used to simulate a 

varying module heat source. For the last parameter, the heater is on for 

30 minutes and off for 30 minutes in the case shown. The CCA completed the 

testing without hardware malfunction or premature component wearout. 

Conchs ions 

The CCA has accumulated a total of 18,925 hours (788 days) of endurance 

operation under this and the previous contract. The CCA has demonstrated 

consistent, reliable operation and has verified the reliability of the 

hardware and control concept. 

Fluid Control Assembly Testing 

Endurance testing of the FCA, which was fabricated and tested under a prior 

program, continued under this program. Figure 33 shows the test stand which 

was used to perform the continued endurance testing of the FCA. This stand, 

which was developed under a prior program and was refurbished for testing 

under this program, provides the instrumentation necessary to exercise the FCA 

through various operating modes. 

58 
FIGURE: 31 COOLANT CONTROL ASSEMBLY TEST STAND 

59 
888 (D*cuo 

O Z 8” 88°*cu0 cur 8 cu ““mm TL 

c I3 

Cn 

w 

I3 

w 

N 

Cr) 

w 

60 
I. 

-- 

FIGURE 33 FLUIDS CONTROL ASSEMBLY TEST STAND 

61 
Testinq 

Figure 34 shows the FCA performance over approximately 9,050 hours (377 days) 

of added endurance testing. The parameters plotted are gas (air) inlet 

pressure, flow rate and residence time. Residence time is related to how 

often the FCA valve is actuated or cycled in a given period. For a residence 

time of 10 minutes, the FCA remains in each of its four states for 10 minutes 

before changing states, resulting in a complete cycle every 40 minutes or 36 

cycles per day. During the course of the testing, the FCA successfully 

performed over 13,500 test cycles. No problems were encountered with any 

mechanical parts of the FCA including the housing, valve spool, seals or drive 

motor. 

Conclusions 

The total test time accumulated on the FCA during this and the prior contract 

is approximately 18,500 hours (771 days). Thus far, no FCA failure due to 

premature component wear or failure has occurred, verifying the reliability of 

the FCA. 

Triple Redundant Relative Humidity Sensor Testing 

Characterization testing of the TRRHS designed and fabricated under this 

program was completed. 

test stand specifically designed and fabricated for the TRRHS test program. 

The characterization testing was performed using a 

Test Support Accessories 

A test stand was designed and fabricated to characterize TRRHS performance. 

The test stand is shown schematically in Figure 35 and photographically in 

Figure 36. The test stand provides for humidification and monitoring of the 

RH of the sample air stream, control of the sample air stream flow rate and 

control and monitoring of temperatures critical to the accurate determination 

of RH. A Relative Humidity Monitor (previously discussed) is included in the 

test stand for observation of sensor performance. The test stand will provide 

a RH range from 18% to 100% in the sensor environmental chamber. 

The test stand takes air from a compressed air source, passes it through a gas 

humidifier which is controlled to impart a pre-determined level of humidity in 

the air, and routes the air to an enclosed environmental chamber housing the 

TRRHS. The TRRHS sensor elements respond to the RH level in the process air 

and the RH readings are displayed on the TRRHS monitor. 

temperature (temperature of the water in the gas humidifier) is closely 

controlled and monitored in order to achieve a desired RH in the process air. 

The temperature of the test chamber is monitored as the dry bulb temperature. 

These two temperatures, when plotted on a psychrometric chart (previously 

shown in Figure 15), determine the actual RH of the sensor test chamber. 

The wet bulb 

A comparison of the sensor readings on the TRRHS Monitor with the actual test 

chamber RH from the psychrometric chart provides an evaluation of sensor 

performance. 

62 
8 0 

7 

0 0 

0 

63 
T3 

I 

I 

MV3 

-Drain 

FIGURE 35 TRRHS TEST STAND MECHANICAL SCHEMATIC 

64 
FIGURE 36 TRIPLE REDUNDANT RELATIVE IlUMTDITY SZNSOR TEST STAND 

65 
Testing 

Checkout and shakedown testing of the TRRHS test stand provided calibration of 

all temperature sensors and verified the performance of each automatic 

shutdown feature and the TRRHS Monitor. 

evaluated the overall accuracy, repeatability and linearity of the TRRHS. 

The characterization testing 

Following calibration of the individual sensor elements, conditions in the 

environmental chamber were varied over the operating range of the sensor. The 

response of the sensor was linear from 18 to 90% RH with only a slight 

nonlinearity indicated above 90% RH. The accuracy of the sensor elements was 

within 23% of actual RH. At 50% RH, the repeatability and short-term 

stability of the sensor was within 22%. 

interval at 100% actual RH without a permanent adverse effect on the sensor 

elements. 

The sensor was operated for a short 

Conchs ions 

Short-term testing of the TRRHS indicates a favorable design and sensor 

selection and promising performance characteristics. More extensive 

evaluation of the TRRHS is required, particularly with respect to temperature, 

air velocity, air pressure and sensor position sensitivity. Long-term sensor 

stability and reliability also require evaluation. 

Carbon Dioxide Reduction System Evaluation 

2 A task performed under this program evaluated the effects of CO and H 

exhausting from the EDC on the Sabatier CO 

was conducted using the CS-1 and the S-CRR fabricated under this program as 

previously described. The S-CRR was mounted in the exhaust line of the CS-1 

subsystem, as shown in Figure 37. Exhaust gases from the S-CRR were analyzed 

by a gas chromatograph to evaluate S-CRR performance. The performance of the 

Sabatier reactor was determined by evaluating the efficiency of the reactor in 

4' converting the reactant gases to CH 

"Conversion efficiency" can be expressed as a percentage of the amount of H 

or CO reacted, and is dependent upon which component (H or CO ) is the 

limitgng or "lean" reactant. 

reaction (Figure 24), four moles of H are required to completely convert one 2 mole of CO By optimizing 

the reactor size, catalyst bet composition, reactor temperature profile and 

reactant gas flow rates, the efficiency of converting stoichiometric 

quantities of the reactant gases to CH will approach 100%. If the reactant 4 gases are not at the stoichiometric ratio of four moles of H to one mole of 2 C02, one reactant gas will be completely reacted (the lean component) while 

some portion of the second reactant will remain unreacted. For example, if 

less H is present than required for complete conversion of C02, the 

conversion efficiency based upon reacted H will be greater than the 

conversion efficiency based upon reacted C6 since all H2 will be reacted and 

some CO will remain unreacted. Conversion efficiencies based upon the 

abundang reactant (or reactant in excess) are not an accurate measure of 

reduction process. 2A test program 2 

2 

As previously illustrated $n the Sabatier 

to one mole of CH and two moles of water vapor. 2 

2 

2 

66 
---f 

---i 

r67 
reactor efficiency since the total amount of reactants 

converted are limited by the quantity of lean, or less 

Therefore, the lean component in the Sabatier reaction 

the reactor conversion efficiency. 

Testing 

which could be 

abundant, component. 

is used to calculate 

Endurance testing of the CS-1/S-CRR system was performed for 1,296 hours (54 

days). At the initiation of testing, the CS-1 product gas H /CO mole ratio 

was nominally 3.88 but varied in a range of 3.36 to 4.05 durgng $he term of 

testing. The operating conditions for the S-CRR evaluation test are presented 

in Table 10. Since the H /CO mole ratio in the CS-1 outlet stream was 

typically below the stoiclhometric requirement for the Sabatier reaction, H2 

(the lean component) was used to determine the reactor conversion efficiency. 

Hydrogen conversion efficiencies were determined before, at several intervals 

during and at the end of testing. The reactor conversion efficiency at the 

start of the test was greater than 98%; conversion efficiency at the end of the 

test was greater than 99%. These results indicate no reduction in reactor 

conversion efficiency during the 1,296 hours of testing and no adverse effects 

of EDC-exhausted H and CO on reactor catalyst performance. 

Conclusions 

2 

2 2 

As expected, the S-CRR exhibited no catalyst degradation or loss of catalytic 

activity when operated in-line with the product gases from the EDC subsystem. 

Continued testing of the CS-1/S-CRR system is recommended to further evaluate 

the long-term effects of EDC subsystem exhaust gases on S-CRR catalytic 

activity. Additionally, optimization of S-CRR operating conditions, including 

reactor temperature profile and catalyst bed composition, are expected to 

further enhance S-CRR performance. 

AIR REVITALIZATION SYSTEM INTEGRATION TECHNOLOGY STUDIES 

Under previous NASA contracts and sponsorship, Life Systems designed, 

fabricated and evaluat he performance of a one-person Experimental Air 

Revitalization System. e'35 This system was designed to provide the atmosphere 

revitalization functions necessary to support spacecraft crew members. Under 

an advanced development program, a one-person integrated ARS will be developed 

to provide weight, power and volume savings over the use of discrete 

subsystems. 

A series of studies and analyses were performed under this program to define 

requirements needed to incorporate the EDC CO concentration function into an 

integrated ARS. The studies included (1) definition of the mechanical/ 

electrochemical assembly of the integrated ARS, (2) definition of the C/M I 

requirements for the ARS, (3) a study detailing the impact of replacing the 

EDC with a steamed desorbed amine CO concentrator subsystem in the ARS, (4) a 

study evaluating techniques for minimizing ARS blower noise and (5) preparation of a subsystem component size and characteristics table. The results of 

each of these studies are discussed in summary fashion in the following 

sections, with Figures and Tables used to provide illustrations or examples of 

the type of information generated by the individual technology studies. 

2 

2 

68 
TABLE 10 SABATIER REACTOR TEST OPERATING CONDITIONS 

H2/C02 Molar Feed Ratio 

H2 Inlet Flow, cm3/min (in3/min) 

C02 Inlet Flow, cm3/min (in3/min) 

Inlet Temperature, K (F) 

Bed Temperature(a) K (F) 

Bed Temperature(b) K (F) 

Outlet Temperature, K (F) 

Total Operating Time, days 

Nominal 

3.80 

1,560 

(95.2) 

400 

(24.4) 

71 6 

(830) 

535 

(504) 

473 

(392) 

380 

(225) 

54 

Range 

3.364.05 

1,340-1,610 

(81.8-98.2) 

38041 0 

(23.2-25.0) 

704-752 

(808895) 

522-572 

(481 -570) 

394-503 

(250446) 

367398 

(202-257) 

- 

(a) Thermocouple located approximately 2.54 cm (1.0 in) from bed inlet 

(b) Thermocouple located approximately 11.7 (4.6 in) from bed inlet 

69 
Mechanical/Electrochemical Assembly Design 

c02 The ARS performs the function of humidity control, CO concentration, 

reduction and oxygen (0 ) generation. 

heat exchanger for humigity control, an EDC for CO 

Reactor for CO 

generation. 

atmosphere through the system and collect both humidity and Sabatier Reactor 

condensate. 

shown in Figure 38. A study was completed which defined the preliminary 

schematics, parts lists, component sizing and selection and heat and mass 

balances for a one-person Space Station level ARS. The study defined the 

following : 

Technologies uzilized are a condensing 

concentration, a Sabatier 

reduction and a Static Feed Water hectrolyzer (SFWE) for 0 

A3so included is the ancillary equipment necessary to move cab2n 

The mechanical schematic with sensors for a single-person ARS is 

0 The major mechanical components in a one-person ARS, including the 

weight, power and volume requirements of each component. 

0 Mass and energy balance calculations based upon inlet atmosphere 

temperature, RH and CO partial pressure conditions and 

specifications. 2 

0 A mass and energy balance flow scheme. 

0 The one-person ARS operating interfaces and overall mass and energy 

balance summary. 

0 A summary of the system electrical power requirements. 

The ARS design specifications, weight, volume and power data are summarized in 

Table 11. 

Control/Monitor Instrumentation Design 

A study 

will be 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

a 

0 

0 

was performed which identified the means by which the one-person ARS 

controlled. Areas which were evaluated during this study included: 

Sensor and Actuator Identification Code Definitions 

Mode Definitions and Allowable Mode Transitions 

Control Definitions 

EDCM Current Control and EDCM RH Control Definitions 

EDC-FCA Control Definition 

S-CRR Accumulator Level Control and Temperature Control Definitions 

SFWEM Current Pressure and Coolant Temperature Control Definitions 

2-FPC Temperature Control Definition 

WES-FCA Control Definition 

Dew Point Temperature Control Definition 

Sensor and Input Definitions 

Actuator and Output Definitions 

Steady-State Actuator Conditions 

70 
CIBJCINAL PAGE IS 

OE POOR QUALIn 

m 

I i: 

B 4 

I I= 

I 

i 

i 

ji 

71 
TABLE 11 ARS-1 SPECIFICATIONy WEIGHT, VOLUME AND POWER SUMMARY 

Crew Size 

CO, Removal Rate, kglday (IWday) 

0, Generation Rate, kglday (IWday) 

Humidity Condensate Rate, kglday (IWday) 

Sabatier Reactor Efficiency, O/O 

Cabin pCO,, Pa (mmHg) 

Cabin PO, kPa (psia) 

Cabin Temperature, K (F) 

Cabin Dew Point, K (F) 

Cabin Pressure, kPa (psia) 

Gravity, g 

Duty Cycles 

Mechanical Assembly Weight, kg (Ib) 

Mechanical Assembly Dimensions, 

Height x Width x Depth, cm (in) 

Mechanical Assembly Volume, m3 (ftj 

Mechanical Assembly Power Requirement, W 

(a) Range = 133 to 1,600 Pa(l to 12 mmHg.) 

1 

1 .OO (2.20) 

1.40 (3.08) 

2.82 (6.22) 

>95 

400 (3.Ofla) 

21 (3.0) 

291 300 (65-80) 

277-289 (4060) 

101 (14.7) 

Otol 

Continuous 

and Cyclic 

116.0 (255.7) 

91 ~46x84 

(36 x 18 x 33) 

0.36 (12.64) 

584 

72 
The ARS operating modes and mode transitions, control loops and control 

algorithms and lists of sensors and actuators to be included in the 

electromechanical assembly were defined. The results can be summarized as 

follows . 

1. 

2. 

3. 

4. 

The C/M I will have the capability to both control system operation 

and provide automatic protection against out-of-tolerance 

conditions. 

Operation of the ARS-1 will be characterized by five separate modes: 

Normal, Standby, Purge, Shutdown and Unpowered. 

Mode transitions will be performed automatically by the C/M I and 

each mode transition will consist of a series of sequential steps 

which will provide a safe and orderly change from one mode to the 

next. 

To implement each mode and programmed mode transition, a series of 

specific control loops must be initiated and maintained. 

The information evaluated during this study effort will form the architecture 

for an ARS-1 C/M I. 

selection of the required electrical hardware components and their assembly 

into an integrated instrumentation package. 

Implementation of this information can be achieved by the 

Impact of an Alternate CO Removal Subsystem 2 

The objective of this study report was to evaluate the impact of substituting 

a Steam Desorbed Amine CO Concentrator Subsystem (SDAS) in place of the EDC. 

The evaluation included t?ie preparation of a schematic, a power, weight and 

volume comparison and a discussion of operational differences which would 

result from the substitution. 

The SDAS technology is based on the cyclic absorp @n~ and desorption of CO 

a bed of a weekly basic ion exchange amine resin. 

absorption and desorption are defined by equations (2), (3) and (4) below ani 

illustrated in Figure 39. 

by 

The mechanisms for $0 

Absorption: RzNH + H20 + RzNH OH ( 2) 

Desorption: RzNH2 H 23 CO + Heat + RzNH2 + C02 + H20 (4) 

2 3 

RzNH 3 OH + C02 + RzNH2 H2C03 (3) 

A key parameter not shown by these equations is that the moisture content of 

each bed must be maintained in the 20 to 35% range for optimal C02 absorption. 

Also, because the process operates in an on-off batch mode, two resin beds are 

required. This requires having one bed absorbing while the other is desorbing 

to maintain a steady pC02 level. 

73 
Air (-CO,) 

CO, + H, 

(To Reduction) Dist. H,O 

A 2 1 I 

From OGS From WRS H2O 

Resin Bed Desorbing 

RzNH2,H2C03 + Heat - RzNH30H + C02 

OGS = 0, Generation Subsystem WRS = Water Reclamation System 

FIGURE 39 STEAM DESORBED AMINE C02 REMOVAL PROCESS 

74 
I. 

Figure 40 illustrates the schematic of a single-person ARS system using the 

SDAS CO concentrator. 

Subsystem illustrated in Figure 38 (previously shown). A comparison of the 

two integrated systems resulted in the following key points: 

This can be compared with the ARS using the EDC 2 

1. Substitution of the SDAS results in a weight increase of 22.5 kg 

(49.5 lb) and an equivalent weight increase of 110.9 kg (244.1 lb). 

2. Substitution of the SDAS results in a negligible net power increase 

(only 1.8 W). 

n 

3. Substitu ion of the SDAS results in a volume increase of 0.12 m3 

(4.08 ft 1. 5 

4. Substitution of the SDAS results in a net sensible heat rejection 

decrease of 75 W and a net latent heat rejection increase of 76.4 W. 

5. Substitution of the SDAS results in a reduction of the oxygen 

consumption rate by 0.42 kg/day (0.93 lb/day). 

While these values are specifically for a one person-sized system, they can 

readily be used on a per person basis when scaling the ARS concept to larger 

crew size. 

Substitution of an SDAS into the ARS in place of an EDC module results in 

significant weight and volume penalties for a spacecraft ARS. 

the operating rate flexibility provided by an EDC-based ARS is lost by 

SDAS-based ARS without further power, weight and volume penalties. An 

advantage of the SDAS substitution is an ability to operate without concurrent 

operation of the water electrolysis unit during the dark portion of the orbit, 

since H is not required for SDAS function. Results of the comparison are 

summarized in Table 12. 

In addition, 

2 

Evaluation to Minimize ARS Blower Noise 

A concern in design of the Space Station is high noise levels in the crew 

environment. A major source of noise are fans and blowers. In recognition of 

this concern, a study was performed to identify blowers and noise prevention 

techniques for the ARS. 

The mechanical schematic of the ARS was previously shown in Figure 38. As 

shown, two blowers are utilized. Blower B1 is used to provide air flow 

through the condensing heat exchanger and the cooling air through the Sabatier 

Reactor; blower B2 is used to provide air flow through the EDC module and the 

humidity condensate separator. Several blowers which meet the noise, power, 

weight and current requirements are commercially available. 

Noise reduction techniques were grouped into the following categories: 

1. Noise control at the source. 

2. Control of the path sound. 

3. Noise control at the receiver. 

75 
7 

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ORIGINAL PAGE IS 

(IE ROOR QUU"X 

75 
TABLE 12 ARS-1 SDAS-EDC COMPARISON 

Subsystem characteristic(') 

Total Power, W 

Total Heat Rejection, W 

0, Consumption, kglday (IWday) 

H,O Latent Load, kg H,O/day (Ib H,O/day) 

Total Weight, kg (Ib) 

AC Power Penalty, kg (Ib) 

DC Power Penalty, kg (Ib) 

Liquid Coolant Penalty, kg (lb) 

Cooling Air Penalty, kg (lb) 

Humidity Control Penalty, kg (lb) 

Condensate Processing Penalty, kg (Ib) 

0, Generation Penalty, kg (Ib) 

Total Equivalent Weight, kg (lb) 

Total Volume, m3 (ft? 

ARS-1 With 

SDAS 

57.8cb) 

54.O(b) 

32 (7.0) 

56.4 (124.3) 

46.4 (102.2) 

1.4 (3.0) 

21.2 (46.6) 

81 .O (1 78.5) 

21.5 (47.3) 

227.9 (501.9) 

0.16 (5.6) 

ARS-1 With 

EM: 

56.0 

129.0 

0.4 (0.9) 

0.5 (1 .l) 

33.9 (74.8) 

15.5 (34.1) 

2.1 (4.7) 

9.0 (19.9) 

4.2 (9.2) 

12.4 (27.3) 

3.3 (7.2) 

36.6 (80.6) 

11 7.0 (257.8) 

0.04 (1 5) 

(a) Penalties: AC Power = 0.32 kg/W (0.71 Iww), DC Power = 0.27 kg/W (0.59 Iww), Liquid Coolant = 0.08 kgfW (0.18 Iww), Cooling Air 

= 0.20 kgMl(O.44 Ibw, Humidity Control = 11.56 kg/kg/day (25.50 IWlWday), Water Processing = 3.06 kg/kg/day (6.75 IWIWday), 

0, Generation = 34.93 kglkg H,O/day (77.00 lWlb H,O/day). 

(b) Includes 40 W credit for reduction of blower 82 duty with elimination of EDC and a91.2 W credit for reduction of the SFWE duty. 

77 
An evaluation of each of these noise control/reduction techniques was 

performed. 

selection of equipment with inherently quiet operation. However, other 

methods of controlling noise at the source exist including changing the 

radiating structure and method of mounting. Changing the radiating structure 

includes techniques such as reducing surface areas of external vibrating parts 

and placing holes in radiating members to reduce the efficiency of radiation. 

Mounting can prevent transmission of vibrations from one structure to another 

through the use of shock mounts and viscous damping materials applied to 

vibratory surfaces. 

The most straightforward and best method of noise control is 

Two elements can be altered to control the path of sound: 

environment. 

direction and/or the distance from the receiver. Both of these methods are 

effective only when a free-field condition exists, which is not the case being 

considered. Addition of acoustical absorbing materials to the environment is 

very effective and a wide range of these materials exist and can be found in 

the literature. Attenuating structures such as walls, barriers and total 

enclosures, can also be added to the environment to reduce noise levels to the 

receiver. Airborne sound reduction can be achieved by a total enclosure or 

combination of enclosures. The trade-off between complexity, weight, volume 

and cost and noise levels must be considered when adding attenuating 

structures. 

position and 

The position of the source can be altered by changing the 

Noise control at the receiver consists primarily of personal protective 

equipment, e.g., ear plugs. This method is not practical for the case being 

considered. 

The evaluation indicated that the most favorable means of blower noise 

reduction for the ARS is the selection of equipment with inherently quiet 

operating characteristics. Noise reduction can then be further enhanced 

through the use of supplementary acoustical absorbing materials. 

Sizing and Characteristics Table for an ARS EDC 

The preparation of Space Station trade studies requires information on the 

power, weight and volume characteristics of the candidate technologies. A 

study was completed which determined power, heat rejection, weight, 

dimensional, volume packaging, maintainability, safety and reliability data 

for the individual components of a one-person EDC subsystem. The information 

was broken down to the ORU level. Data were generated for each of the 

following components: the EDCM, the FCA, the CCA, the inlet duct assembly, 

the outlet duct assembly, the RH sensor, the filter and isolation valves and 

the liquid/liquid heat exchanger. 

summarized in Table 13. 

Data defined as a result of this report are 

78 
TABLE 13 COMPONENT SIZING AND CHARACTERISTICS SUMMARY FOR ARS-1 EDC 

Item 

No. Unit or Comment Name 

Module, Elec. CO, Conc. 

Assembly, Fluids Control 

Assembly, Coolant Control 

Assembly, Inlet Duct 

Assembly, Outlet Duct 

Sensor, Relative Humidity 

Valve, Filter and Isolation 

Heat Exchanger, LiqJLiq. 

- Qty. 

1 

1 

1 

1 

1 

2 

2 

1 

Total Weight(') 

kg Ob) 

14.8 (32.6) 

1.1 (2.5) 

1.6 (3.5) 

2.0 (4.3) 

1.0 (2.2) 

0.6 (1.4) 

2.6 (5.8) 

0.7 (1.5) 

1 

1 

0 

Weight of 

0fl.hrd 

ExpendaMes 

kg Ob) 

0.0 

0.0 

0.0 

0.0 

0.0 

0.0 

0.0 

0.0 

Vdume 

cm3 fin? 

Heat 

Reiection. W 

Total Average 

Power. w 

Est. Maintenance 

Time Reauired. hrhr 

18,354 (1,120.0) 

1,966 (120.0) 

3277 (200.0) 

4,588 (280.0) 

3277 (200.0) 

38 (2.3) 

411 (25.1) 

90 (5.5) 

63 

2 

48 

4 

0 

-24 

2 

48 

0 

0 

4 

70 

0 

<0.8 

<0.8 

<12 

0.0 

0 .o 

<0.8 

<0.8 

0.0 

(a) Basic System 

79 
CONCLUSIONS 

The following conclusions are a direct result of the program activities. 

1. 

2. 

3. 

4. 

5. 

6. 

The CS-1, sized for one-person CO removal capacity, successfully 

performed its intended function wgth the liquid-cooled electrochemical 

cells. Over 4,200 hours of added operation were achieved with an 

average CO removal efficiency of greater than 9OX and an average 

cell voltage of 0.38 V. Total operating time on the CS-1 has now 

reached 6,035 hours. 

2 

Cyclic operation of the CS-1 verified overall subsystem versatility 

and demonstrated the capability to quickly recover the CO 

process following the transition from Standby operation to Normal 

operation. 

removal 2 

Continued endurance testing of the EDC subsystem components (EDCM, 

FCA and CCA) was successfully conducted. 

testing were achieved on the FCA and CCA and over 4,700 hours on the 

six-cell EDCM, bringing the total test time to 18,500 hours on the 

FCA, 18,925 hours on the CCA and 19,375 hours on the six-cell EDCM. 

Over 9,000 hours of 

The isolation valve designed and fabricated under this effort 

demonstrated effective operation and sealing characteristics against 

both pressure and vacuum while imparting a pressure drop of 107 Pa 

differ ntial pressur5 (0.43 in water) at an air flow rate of 

1.22 m /min (43.2 ft /min> . 5 

The Sabatier Reactor fabricated under this program to aid in 

evaluating EDC exhaust gas effects demonstrated design level 

performance with no deterioration in CO 

1,296 hours of operation. 

reduction capability after 2 

The TRRHS demonstrated reliable, accurate relative humidity sensing 

in the range of 20 to 95X RH. 

RECOMMENJIATIONS 

It is recommended that the current program be extended and focused on 

continued testing of the CS-1 concept, hardware and ancillary components. 

This added activity would include continued endurance testing of the CS-1 

subsystem in both the normal and cyclic operating modes to accumulate extended 

performance and reliability data. 

six-cell EDCM, the FCA and the CCA would be performed to expand the hardware 

reliability data base. 

characterization testing of the TRRHS to evaluate its long-term accuracy, 

reliability, stability and durability. Added endurance testing with the 

Sabatier CO 2 performance profile when tested with EDC exhaust gases at the nonstoichiometric 

H /CO 

og a lollow-on activity would be to advance the EDC subsystem to the stage 

where it can be incorporated into the ECLSS for the Space Station. 

Continued long-term testing of the 

The follow-on program should include extensive 

Reduction Reactor should be performed to determine a long-term 

mole ratios typically experienced with an EDC. The overall objective 

80 
REFERENCES 

1. Quattrone, P. D.; Babinsky, A. D. and Wynveen, R. A., "Carbon 

Dioxide Control and Oxygen Generation," Paper No. 70-Av/SpT-8 ASME 

Conference; Los Angeles, CA; 1970. 

2. Wynveen, R. A. and Quattrone, P. D., "Electrochemical Carbon Dioxide 

Concentrating Systems," Paper No. 71-Av-21, SAE/ASME AIM 

Conference; San Francisco, CA; July, 1971. 

3. Wynveen, R. A.; Schubert, F. H. and Powell, J. D., "One-Man, 

Self-contained CO Concentrator Systems," Final Report, Contract 

NAS2-6118, NASA C6-114426; Life Systems, Inc., Cleveland, OH; 

March, 1972. 

4. Powell, J. D. et al., "Six-Man, Self-contained Carbon Dioxide 

Concentrator Subsystems," Final Report, Contract NAS2-6478, NASA 

CR-11473; Life Systems, Inc., Cleveland, OH; July, 1974. 

5. Schubert, F. H. and Quattrone, P. D., "Development of a Six-Man, 

Self-contained Carbon Dioxide Collection Subsystem for Spacecraft 

Application, Paper No. 74-ENAs-16, Intersociety Conference on 

Environmental Systems; Seattle, WA; July, 1974. 

6. Schubert, F. H.; Marshall, R. D.; Quattrone, P. D. and Wynveen, R. 

A., "Development of a Three-Man Preprototype CO Collection 

Subsystem for Spacecraft Application," Paper No? 77-ENAs-19, 

Intersociety Conference on Environmental Systems; San Francisco, CA; 

July, 1977, 

7. Marshall, R. D.; Ellis, G. S.; Schubert, F. H. and Wynveen, R. A., 

"Extended Duration Orbiter Study: CO Removal and Water Recovery," 

Final Report, Contract NAS9-15218, NAgA CR-160317; Life Systems, 

Inc., Cleveland, OH; May, 1979. 

8. Schubert, F. H.; Heppner, D. B.; Hallick, T. M. and Woods, R. R., 

"Technology Advancement of the Electrochemical CO Concentrating 

Process," Final Report, Contract NAS2-8666, NASA 6R-152250; Life 

Systems, Inc., Cleveland, OH; May, 1979. 

9. Marshall, R. D.; Schubert, F. H. and Yang, P. Y., "EDC - A 

Regenerable CO 

Orbiter," Paper No. 79-ENAs-34, Intersociety Conference on 

Environmental Systems; San Francisco, CA; July, 1979. 

Removal Subsystem for an Enhanced Capability 2 

10. Schubert, F. H. and Lance, N., "Regenerable C02 Collection for 

Spacecraft Application," Paper No. 81-ENAs-28, Intersociety 

Conference on Environmental Systems; San Francisco, CA; July, 1981. 

81 
11. Schubert, F. H. ; Hallick, T. M. and Koszenski, E. P., "Advanced 

Electrochemical Depolarized Concentrator Cell Development," Final 

Report, Contract NAS2-10204, NASA CR-166141; Life Systems, Inc., 

Cleveland, OH; December, 1981. 

12. Heppner, D. B.; Dahlhausen, M. J. and Schubert, F. H., 

"Electrochemical Carbon Dioxide Concentrator Subsystem Development," 

Final Report, Contract NAS2-11129; Life Systems, Inc., Cleveland, 

OH; November, 1983. 

13. Heppner, D. B.; Hallick, T. M. and Schubert, F. H., "Advanced Air 

Revitalization System Testing," Final Report, Contract NAS2-10961; 

Life Systems, Inc., Cleveland, OH; June, 1983. 

14. Heppner, D. B. and Schubert, F. H., "Electrochemical and 

Steam-Desorbed Amine CO Concentration: Subsystem Comparison," 

Paper No. 831120, Intersociety Conference on Environmental Systems; 

San Francisco, CA; July, 1983. 

2 

82 
. 

1. Report No. 

NASA CR-177411 

4 

2. Gowmmont Acurrion No. 3. Recipient's Cltalog No. 

NASA CR - 177411 

i 

ri 

4. Title md Subtitle 

ELECTROCHEMICAL CARBON DIOXIDE CONCENTRATOR SUBSYSTEM DEVELOPMENT - Final Technical Report 

7. Author(s1 

E. P. Koszenski, D. B. Heppner, C. T. Bunnell 

Life Systems, Inc. 

24755 Highpoint Road 

0. Psrfaming Orgnniutim Name and Address 

Cleveland, OH 44122 

12. Sponsoring Aqtncv bme and Address 

National Aeronautics and Space Administration 

Washington, DC 20546 

15. Supplementary Notes 

5. Report Date . 

6. Worming Orpniration bdo 

March 1986 

8. Worming Orwnization Raport No. 

10. Work Unit No. 

T-6936 

11. Controct or Grant No. 

NAS2-11787 

13. Typ of R.pwr and Riod Covered 

Contractor Report 

14. Sponsoring -cy Code 

506-64-3 1 

117. Key Words (Suggcrted by Author($)) I 18. Distribution Statement 

19. Security Qascif. (of this report1 

UNCLASSIFIED - UNLIMITED I Electrochemical Carbon Dioxide Concentrator, Integrated Air Revitalization 

20. Security Classif. (of this p~l 21. NO. of p.gcr 22. Rice' 

Subject Category: 54 I System, Sabatier Carbon Dioxide Reduction Reactor I 

1 UNCLASSIFIED 1 UNCLASSIFIED I 92 I 

'For ule by the National Trhnicrl Infornution Sonice. Springfield. Virginia 22161