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IS20

George C. Marshall Space Flight Center

Marshall Space Flight Center, Alabama

35812
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i

NASA/CR—2010–216451

Integrated Evaluation of Closed Loop Air 

Revitalization System Components

K. Murdock

Wolf Engineering, LLC, Somers, Connecticut

November 2010

National Aeronautics and

Space Administration

Marshall Space Flight Center • MSFC, Alabama 35812

Prepared for Marshall Space Flight Center 

under Contract NNM10AB15P
ii

Available from:

NASA Center for AeroSpace Information

7115 Standard Drive

Hanover, MD 21076 –1320

443–757–5802

This report is also available in electronic form at

<https://www2.sti.nasa.gov>

Acknowledgement

The work documented in this Contractor Report (CR) was performed over the period of 2004 through 2006 

as a joint effort between NASA Marshall Space Flight Center (MSFC), Johnson Space Center (JSC), and Ames 

Research Center (ARC); Hamilton Sundstrand; and Southwest Research Institute. JSC provided the initial funding 

for the preparation of a test report. MSFC provided funding for the completion and publication of this CR. 

The author would like to thank all NASA civil servants and contractors for their support in completing this sizable 

project, especially Bernadette Luna, ARC; James Knox, Jay Perry, and Monserrate Roman, MSFC; Fred Smith, JSC; 

Lee Miller, ECLS Technologies; and Melissa Campbell, Hamilton Sundstrand.
iii

TABLE OF CONTENTS

1. INTRODUCTION ............................................................................................................... 1

1.1 What Did We do ............................................................................................................. 2

1.2 Why Did We do It ........................................................................................................... 2

1.3 What Did We Learn ........................................................................................................ 2

1.4 What do We Want to do Next ......................................................................................... 3

2. INTEGRATED TEST CONFIGURATION ....................................................................... 4

2.1 Description of Equipment—Subsystems and Support Hardware ................................... 5

 2.1.1 4-Bed Molecular Sieve (4BMS) Carbon Dioxide Removal Assembly (CDRA) ...... 6

 2.1.2 Mechanical Compressor Engineering Development Unit and Accumulator .......... 9

 2.1.3 Temperature Swing Adsorption Compressor (TSAC) ............................................ 11

 2.1.4 Sabatier Carbon Dioxide Reduction Subassembly ................................................. 19

 2.1.5 Support Hardware Configuration .......................................................................... 23

2.2 Integrated Test Using the Mechanical Compressor ......................................................... 32

 2.2.1 Overall Test Plan Objectives .................................................................................. 32

 2.2.2 Description of Test Plan Details ............................................................................ 35

 2.2.3 Discussion of Test Results ..................................................................................... 43

 2.2.4 Conclusions From This Test Section ...................................................................... 55

2.3 Integration Test Using the TSA Compressor .................................................................. 55

 2.3.1 Description of Tests ............................................................................................... 55

 2.3.2 Discussion of Test Results—Integration Test With TSAC ..................................... 63

 2.3.3 Conclusions From This Test Section ...................................................................... 71

3 CONCLUSIONS .................................................................................................................. 73

3.1 Overall Conclusions From the Integration Test Experience ............................................ 73

3.2 Summary of Observation From the Integration Test ...................................................... 73

3.3 Lessons Learned ............................................................................................................. 76

 3.3.1 Lessons Learned From the Integration Testing ...................................................... 76

 3.3.2 Lessons Learned fFom the Sabatier Flight Program .............................................. 78

3.4 Recommendations for Subsystem Modification if Designing a New System ................... 79

4 RECOMMENDATIONS ..................................................................................................... 82

4.1 Recommended Future Testing ........................................................................................ 82

 4.1.1 Recommended Test Objective ................................................................................ 82

 4.1.2 Specific Recommended Tests .................................................................................
iv

TABLE OF CONTENTS (Continued)

4.2 Recommended Future Hardware Development .............................................................. 83

 4.2.1 Subsystem Development ........................................................................................ 83

4.2.2 Component Development ............................................................................................... 84

 4.2.3 Controls Development ........................................................................................... 84

5. APPENDICES ...................................................................................................................... 86

REFERENCES ......................................................................................................................... 190
v

LIST OF FIGURES

 1. Closed Loop Air Revitalization System .................................................................... 1

 2. Overall block diagram of the Air Revitalization System (ARS) sub-systems. ........... 4

 3. 4-Bed Molecular Sieve Schematic ............................................................................. 7

 4. Work cycle of the TSAC ........................................................................................... 11

 5. Flow diagram of the air-cooled TSAC ...................................................................... 12

 6. TSAC and 4BMS beds temperature and pressure profiles ......................................... 13

 7. Flow diagram of a three-bed TSAC device.. Internal pressure is controlled 

through a feedback loop to the heater. Inert gas vent tubes are not shown ............... 14

 8. Adsorption isotherms and compression cycle ........................................................... 15

 9. Heating and cooling assemblies of the TSAC ........................................................... 17

10. Schematic of 2-bed, liquid-cooled TSAC .................................................................. 17

11. Schematic of the air-cooled TSAC prototype ........................................................... 18

12. Air-cooled TSAC prototype ..................................................................................... 18

13. Sabatier Engineering Development Unit Schematic .................................................. 20

14. Original Sabatier EDU Hardware Configuration ...................................................... 22

15. Nodal representation of ISS for CO2 concentration prediction ................................ 25

16. Example metabolic load profile ................................................................................ 26

17. Example of Metabolic Load Profile CO2 Injection Rate .......................................... 26

18. CO2 Concentration for Simulated Lunar EVA Profile .............................................. 27

19. Integration of ARS Components ............................................................................. 29
vi

LIST OF FIGURES (Continued)

20. High CO2 rate requires excessive activation of vent valve ......................................... 30

21. Test setup of CDRA product CO2 moisture measurement using TILDAS ............... 32

22. CO2 inlet concentration fed to 4BMS for metabolic load profile case ....................... 34

23. Simplified Schematic of CDRA and CRA as intended to be integrated on ISS ........ 36

24. Integrated Test Schematic – 4BMS, Mechanical Compressor, 

Accumulator, Sabatier .............................................................................................. 37

25. Hardware configuration for 4BMS and compressor only tests. ................................. 40

26. Typical Performance Data for Mechanical Compressor Integration Tests ................ 51

27. Simplified Schematic of 4BMS and TSAC Integration Test ...................................... 56

28. Integrated Test Schematic – 4BMS, TSAC, Sabatier ................................................. 57

29. Lunar EVA Mission Scenario Cabin ppCO2 ............................................................ 63

30. Graphical presentation of integration effects on 4BMS efficiency ............................ 64

31. Typical TSAC Performance Data ............................................................................. 66

32. TSAC equilibrium loading pressure is dependent on CO2 feed to CDRA ................ 68

33. Results of simulated Lunar night .............................................................................. 70

34. Simulated Lunar EVA Excursion profile results in long periods 

of Sabatier starvation ............................................................................................... 71
vii

LIST OF TABLES

 1. Compressor Operating Rules .................................................................................... 9

 2. TSAC and 4BMS Synchronization Table .................................................................. 12

 3. Production rates and resource requirements of TSAC sized for two kilograms 

CO2 production per day at 100 kPa .......................................................................... 16

 4. Test conditions for mechanical compressor test ........................................................ 23

 5. Test conditions for the TSAC test ............................................................................. 24

 6. Standoff Valve Operating Rules ................................................................................ 30

 7. Fluid Composition Analysis ..................................................................................... 31

 8. Integrated Test Matrix Input Parameters, Mechanical Compressor Test ................... 42

 9. Integration Test Metrics ............................................................................................ 43

10. Mechanical Compressor CO2 Capture Performance Data ........................................ 49

11. Sabatier Water Production Rate Efficiencies ............................................................. 54

12. Integrated Test Matrix—TSAC Test ......................................................................... 60

13. Operating parameters for 4BMS/TSAC comparison tests ......................................... 63

14. TSAC Performance Target and Actual Results ......................................................... 64

15. Test results for 4BMS/TSAC/Sabatier integrated testing ........................................... 67

16. Sabatier Efficiency Data when Integrated with TSAC ............................................... 69
viii
1 Introduction

NASA’s vision and mission statement include an emphasis on human exploration of 

space, which requires environmental control and life support technologies. As the target 

destination becomes more distant and the target mission duration longer, closed loop life 

support systems become increasingly necessary for feasibility and success.

Figure 1 – Closed Loop Air Revitalization System 

An air revitalization system (ARS) includes temperature and humidity control, oxygen 

and nitrogen supply and control, carbon dioxide and trace contaminant removal and 

carbon dioxide reduction for oxygen recovery. These processes also interact with the 

water recovery system. Crew oxygen is produced by the electrolysis of water. The 

hydrogen by-product of electrolysis is utilized by the carbon dioxide reduction assembly 

along with the waste carbon dioxide to re-form water. This last step, carbon dioxide 

reduction, is a necessary step for loop closure that minimizes the resupply needed for 

crew support. 

This paper describes the development of components for a closed loop ARS, modeling 

and simulation of the components and integrated hardware testing, with the goal of better 

understanding the capabilities and limitations of this closed loop system. The integrated 

testing included a carbon dioxide removal assembly (CDRA), carbon dioxide reduction 

assembly (CRA), and two different compressor technologies that provided the necessary 

link between the CDRA and CRA.

Contractor Report

Integrated Evaluation of Closed Loop Air Revitalization System Components
1.1 What did we do 

The overall test objective was to integrate the carbon dioxide removal assembly with the 

carbon dioxide reduction assembly. Two distinct compressor technologies were 

developed to provide the function of collecting and storing CO2 from the CDRA before it 

is consumed by the CRA. The systems were tested over a range of conditions that 

represented both ISS and Lunar surface activities. The test program was conducted from 

November 2004 through March 2006 in the Laboratory Module Simulator facility at the 

NASA Marshall Space Flight Center (building 4755). 

1.2 Why did we do it 

The purpose of the integrated testing was to operate the two configurations of ARS 

components to determine any limitations or requirements imposed on each component by 

the interfacing components. Each of the hardware assemblies (CDRA, mechanical 

compressor, Temperature Swing Adsorption Compressor (TSAC), and Sabatier Reactor 

Subassembly (SRS)) has been tested independently, and computer simulations have been 

run of the integrated system. Testing was required to evaluate the performance of the 4-

bed molecular sieve (4BMS, another name for CDRA), compressor and Sabatier 

performance when integrated together and to verify the results from the engineering 

analysis. Specifically, the testing was intended to: 

 Provide understanding of transients and integration issues; 

 Validate baseline operation/control logic for the compressors; 

 Validate FORTRAN integrated model of the 4BMS, compressors and Sabatier; 

and 

 Validate the mechanical compressor and TSAC computer models. 

1.3 What did we learn 

The testing described herein was the first integrated test of a Four-Bed Molecular Sieve 

and Sabatier Carbon Dioxide Reduction Assembly with the interfacing CO2 compressor. 

Two compressor technologies were tested, a mechanical oil-free piston compressor and a 

temperature swing adsorption compressor (TSAC). The mechanical compressor was 

tested under simulated International Space Station parameters. The TSAC was tested 

under both ISS and Lunar Base parameters. Both sets of tests provided enhanced 

understanding of nominal steady operation and dynamic, transient scenarios that can be 

expected to occur in an integrated Environmental Control and Life Support System. 

In general, the 4BMS, Sabatier and both compressor technologies were proved 

compatible and able to perform their intended functions for a wide range of input 

conditions. It is feasible, using these technologies to recover oxygen in the form of 

water, to make the next step toward oxygen loop closure. These technologies are ready to 

be advanced to the next Technology Readiness Level (TRL) level and put in service in a 

flight mission. 

2
1.4 What do we want to do next 

This test program showed not only that water recovery is feasible using CO2 reduction, 

but it also identified areas where each of the technologies could be improved. These 

improvements include upgrades to hardware components, changes to control logic and 

the implementation of artificial intelligence or smart controls. Additional testing should 

be performed with these systems to better define the proposed modifications to arrive at 

the best possible solution.

3
2 Integrated Test Configuration 

Integrated testing of carbon dioxide removal and reduction assemblies was performed at 

MSFC over the period from 2004 through 2006. This testing was performed to 

understand the interactions between the different subassemblies in order to plan for future 

phases of subsystem development. This section details the hardware used in the 

integration testing, test configurations and operating parameters, and test results. 

Figure 1 below depicts three main elements of an Air Revitalization System (ARS). 

These systems and their interactions were the focus of this test program. The three 

systems shown below are the carbon dioxide removal assembly (CDRA), the oxygen 

generation assembly (OGA) and the carbon dioxide reduction assembly (CRA). The 

CDRA collects and concentrates carbon dioxide and feeds it to the CRA. The OGA 

electrolyzes water for crew oxygen and feeds the by-product hydrogen to the CRA. The 

CRA reacts hydrogen and carbon dioxide to form methane and water. The water is 

returned to the OGA, thus partially closing the oxygen loop. The OGA/CRA interaction 

has been separately studied by Hamilton Sundstrand, the supplier of the ISS OGA, and is 

not reflected in this report. This report focuses on the interaction of the CDRA with the 

CRA. 

Oxygen Generation System (OGS) Rack Air Revitalization (AR)

Rack

Oxygen Generation 

Assembly (OGA) Carbon Dioxide Reduction 

Assembly (CRA)

Carbon Dioxide 

Removal Assembly 

(CDRA)

Carbon Dioxide 

Management

Subassembly 

(CMS)

Sabatier 

Reactor 

Subassembly 

(SRS)

Waste Water Bus Overboard Vent

H2 CO2

H2O CH4

Oxygen Generation System (OGS) Rack Air Revitalization (AR)

Rack

Oxygen Generation 

Assembly (OGA) Carbon Dioxide Reduction 

Assembly (CRA)

Carbon Dioxide 

Removal Assembly 

(CDRA)

Carbon Dioxide 

Management

Subassembly 

(CMS)

Sabatier 

Reactor 

Subassembly 

(SRS)

Waste Water Bus Overboard Vent

H2 CO2

H2O CH4

Figure 2 – Overall block diagram of the Air Revitalization System (ARS) sub-systems. 

The CRA is further separated into two sub-assemblies, the Sabatier Reactor Subassembly 

(SRS) and the Carbon dioxide Management Subassembly (CMS). The CMS includes the 

compressor and accumulator. The focus of this test program, therefore, is the insertion of 

different compressor technologies into the CMS role supporting the requirements of the 

CDRA and Sabatier in their respective roles in the overall Air Revitalization System. 

4
The 4BMS, Sabatier and compressors have each been independently tested over a range 

of operating conditions. These isolated tests are not covered in this test report, but are 

discussed in references [ ], with the focus of this study being to understand the 

subsystem interactions. The previous liquid and water-cooled versions of the TSAC were 

also tested in conjunction with the 4BMS. These tests are not reported here but are 

detailed in references [ ]. The sequence of test configurations presented here were 

planned to develop a working ARS originally for use on the International Space Station, 

and later as a potential solution for lunar missions. The test configurations are described 

below as they were conducted chronologically: 

1. 4BMS with mechanical compressor and accumulator – (November, December 

2004) 

2. 4BMS, mechanical compressor, accumulator and Sabatier – (February, March 

2005) 

3. 4BMS with air-cooled TSAC – (November 2005) 

4. 4BMS, air-cooled TSAC and Sabatier – (January 2006) 

Referring back to Figure 1 of the Air Revitalization System, the Carbon Dioxide 

Reduction Assembly (CRA) consists of both the Carbon Dioxide Management 

Subassembly (CMS) and the Sabatier Reactor Subassembly (SRS). In these tests we 

evaluated two hardware configurations for the CMS. The mechanical compressor 

requires a separate accumulator; the TSAC serves as both compressor and accumulator. 

Regardless of which compressor technology was installed as CMS, the CMS would 

operate when required based on CO2 availability from the 4BMS, regardless of the 

operating state of the SRS. Since the compressor and 4BMS are so closely linked, each 

compressor was initially tested with the 4BMS prior to addition of the Sabatier. 

2.1 Description of Equipment – Subsystems and Support 

Hardware 

This section describes each of the subsystems used in the integration testing. The 

summary includes the 4-bed molecular sieve (4BMS) carbon dioxide removal assembly 

(CDRA), the Sabatier reactor subassembly (SRS), the mechanical compressor and 

accumulator (the 1st evaluated compressor), and the temperature swing adsorption 

compressor (the 2nd evaluated compressor). 

5
2.1.1 4-Bed Molecular Sieve (4BMS) Carbon Dioxide Removal 

Assembly (CDRA) 

Throughout this paper different terminology will be used to reference the hardware that 

was tested. The term Carbon Dioxide Removal Assembly (CDRA) refers to any system 

that removes carbon dioxide from the breathing atmosphere of a spacecraft. This function 

can technically be performed by a variety of technologies, however the name CDRA was 

given to the CO2 removal system aboard the International Space Station, which is a 4-

bed molecular sieve (4BMS) technology. 

2.1.1.1 4BMS Hardware Description 

The carbon dioxide removal assembly tested in this development project is the same 

technology and configuration as the hardware currently installed and operating on the 

International Space Station (ISS). The ISS CDRA, developed by Honeywell (1), uses a 

four-bed molecular sieve process that consists of two desiccant beds and two CO2 sorbent 

beds. Ancillary components include a blower, air-save pump, heat exchanger, valves, and 

sensors. Figure 3 is a schematic representation of the major components of the four-bed 

molecular sieve process. Cabin air is drawn through one desiccant bed to remove the 

moisture then through one CO2 sorbent bed to remove the CO2. This processed air is then 

sent through the second, heated desiccant bed to re-humidify the stream before returning 

the air back to the cabin. At the same time, the second CO2 sorbent bed, which is loaded 

with CO2, is heated and evacuated to desorb the CO2. Prior to exposing the loaded bed to 

vacuum the air save pump removes ullage air out of the desorbing bed and vacuum 

circuit and pumps it to the cabin. This is done in the first 10 minutes of the desorption 

half-cycle. The vacuum circuit runs from the desorbing bed check valve to space vacuum, 

shown as the yellow line in Figure 3. A half-cycle refers to the timed period in which one 

bed is doing all of the CO2 removal function. At the start of the next half-cycle, all beds 

switch to the opposite mode and cabin air flow ‘swings’ to the other set of adsorbent 

beds; the alternate bed then performs the CO2 removal function. In this manner 

continuous CO2 removal is achieved. 

The Performance and Operational Issues System Testbed (POIST) 4BMS unit located in 

the ISS Laboratory Module Simulator (LMS) at MSFC was used for this testing. This 

system has been extensively modified to achieve functionally flight-like performance for 

ISS sustaining engineering ground support testing (2). 

The CDRA uses a pressure and temperature swing adsorption cycle to remove carbon 

dioxide from the crew breathing air. The CO2 removal beds are filled with 5A molecular 

sieve that is packed between heater plates. At the start of an adsorption cycle, the mass 

fraction of CO2 on the desiccant is very low and therefore the equilibrium concentration 

of CO2 in the air returned to the cabin is practically zero. With prolonged exposure to 

CO2, the bed adsorbs CO2 and ‘fills’, and the return air may contain small but increasing 

amounts of CO2. At the end of the half-cycle, it is desorbed with both heat and vacuum. 

The bed is heated electrically to 400°F during daytime operation when power on the ISS 

6
is plentiful, but during nighttime operation, the heaters are turned off. The length of the 

ISS orbit is approximately 90 minutes with the “day” portion running from 90 minutes 

maximum to 53 minutes minimum, depending on the inclination of the orbit. For all 

day/night cyclic testing, the worst case 53 minute day was used. The 5A molecular sieve 

material has a high affinity for water vapor, which preferentially adsorbs and displaces 

CO2. Because of this phenomenon, the two desiccant beds are included in the 4-bed 

design. One desiccant bed removes water prior to the air stream entering the 5A bed, 

while the other bed, previously loaded, replenishes the water to prevent over-drying of 

the cabin air. 

AIR SAVE

PUMP

OPEN LOOP

VENT

VALVE

SELECTOR

VALVES

TO

SPACE

VACUUM

CO2 SORBENT BED (2)

(ADSORBING)

ELECTRICAL

HEATERS

CO2 SORBENT BED (4)

(DESORBING) ELECTRICAL

HEATERS

AIR BLOWER

DESICCANT BED (3)

(DESORBING)

DESICCANT BED (1)

(ADSORBING)

AIR

INLET

AIR

RETURN

CHECK

VALVE

ITCS

INLET

SELECTOR

VALVES

SG 13X 5A

ABSOLUTE

PRESSURE

SENSOR

SG 13X 5A

PRECOOLER

1

2

1

2

1

2 1

2 1

2 2

1

Air wit h CO2, H2O Air wit hout CO2, H2O

Air wit h CO2 (no wat er) Air wit h H2O (no CO2)

CO2

13X

13X

Figure 3 - 4-Bed Molecular Sieve Schematic 

2.1.1.2 4BMS Integration Characteristics 

One of the peculiarities of the 4BMS CDRA is that it is designed to operate on a 144 

minute half cycle (10 cycles per 24-hour day). This becomes an issue only when 

integrating CDRA with other systems designed to operate in synch with the 90 minute 

diurnal orbit of the International Space Station. The 4BMS operates on the physics of 

adsorption isotherms of 5A molecular sieve. As such, the temperature and pressure 

achieved during the desorption period affects the capacity for air scrubbing on the 

following cycle. This becomes an important factor when integrating with a downstream 

system that affects the desorption pressure and when nighttime power saving protocols 

limit the temperature the bed reaches. The two molecular sieve beds must have sufficient 

capacity such that the high efficiency periods can carry it through the times when the 

pressure and temperature are not so favorable for good desorption. 

The 5A molecular sieve material also has adsorptive capacity for chemicals other than 

CO2 and water. Some trace contaminants in the cabin atmosphere will be adsorbed on the 

zeolite and desorbed along with the carbon dioxide. Some of these chemicals have been 

7
shown to affect the operation of downstream systems, specifically the Sabatier reactor. A 

summary of contaminant testing that was performed on the Sabatier catalyst is detailed in 

J.D. Tatara and J.L. Perry; International Space Station Trace Contaminant Injection Test, 

Revision A, NASA Test Requirements Document, January 1997. 

8
2.1.2 Mechanical Compressor Engineering Development Unit and 

Accumulator 

2.1.2.1 Mechanical Compressor Hardware Description 

A compressor is needed to provide a vacuum for 4BMS desorption as well as 

compression of CO2 for efficient storage and controlled delivery to the Sabatier. The first 

compressor design tested was a mechanical two-stage, reciprocating piston compressor 

design with three in-line cylinders, which was developed by Southwest Research 

Institute. There are two first stage pistons and one second stage piston. The compressor is 

an oil-free design so that no oil contamination is introduced to the downstream Sabatier 

reactor. A 2-micron filter on the inlet suction line traps any dust particles generated by 

the 4BMS beds. The compressor is cooled with 65°F chilled water representative of the 

medium temperature loop (MTL) on ISS. At median pressures of 4 psia suction and 70 

psia discharge, the compressor delivers approximately 17.7 scfh (1.9 lb/hr) of CO2. 

To reduce compressor run time, the operating rules in Table 1 were established and 

programmed into the integrated control system. PACCUM is the compressor discharge or 

accumulator pressure while PSUCTION is the compressor suction or 4BMS desorbing bed 

pressure. These rules set the pressure limits for compressor activation and deactivation. 

For example, when the accumulator is almost full, at 110 psia, the compressor will not 

activate until the bed pressure exceeds 7.5 psia. These operating rules were developed 

with the goal of minimizing the compressor operating time, minimizing compressor 

power consumption and preventing starvation of the Sabatier. Starvation is defined as any 

time when hydrogen is produced by the OGA, but no CO2 is available for reaction. The 

performance goals are achieved by limiting the compressor operation to periods when 

CO2 is plentiful or the pressure rise is low. These operating rules were established during 

the model development period (described later) and were verified during this test activity. 

The compressor rules successfully minimize Sabatier starvation. 

Table 1 – Compressor Operating Rules

Compressor Transition Conditions 

Transition PACCUM (psia) PSUCTION (psia) 

>=100 AND <120 AND > 7.5 Standby to >25 AND <100 AND > PACCUM/58 + 3.6 Operate 

<=25 AND > 1.0 

> 40 AND < PACCUM/58 + 1.5 Operate to 

Standby <= 40 AND < 0.5 

>130 NA 

9
2.1.2.2 Accumulator 

Due to the chromatographic nature of CO2 desorption from molecular sieves resulting in 

short duration ‘waves’ of CO2 flow, and the Sabatier requirement for constant inlet CO2 

flow, a buffering capacity is needed to integrate a 4BMS and a Sabatier when using a 

mechanical compressor. This is accomplished with a 0.73 ft3 accumulator. Due to space 

limitations within the OGA rack where the CRA hardware would be located on orbit, the 

total accumulator volume is achieved by ganging several small vessels together. The 

accumulators used for this test matched those being installed in the OGS rack. 

2.1.2.3 Mechanical Compressor / Accumulator Integration 

Characteristics 

Since the mechanical compressor has no storage capacity, an accumulator is required to 

buffer the short duration, high rate production of CO2 from the CDRA into the long 

duration, low flow rate consumption of the Sabatier. The initial sizing of the accumulator 

was to be one cubic foot. This resulted in an ultimate pressure of 90 psia needed to store 

adequate CO2 to prevent starvation. This pressure level is under the 100 psia threshold 

that requires additional analysis on pressure vessels. Due to the space limitations in the 

OGS rack, the maximum volume accumulator that could be packaged was 0.73 ft3. This 

results in a need for 120 psia storage pressure to prevent starvation. 

The CDRA desorbs carbon dioxide from the molecular sieve first, followed by a wave of 

water. Water vapor in the mechanical compressor could pose problems if condensation 

occurs in either the compressor or the accumulator tank. A series of tests were conducted 

to analyze the desorption flow from the CDRA for the concentration of water in the 

carbon dioxide. The details of this test series are given in section 2.2.2.5. The results 

indicated that there is not enough water vapor desorbed by the CDRA during the normal 

desorption cycle to cause condensation in the compressor at pressures up to 120 psia. 

10
2.1.3 Temperature Swing Adsorption Compressor (TSAC) 

2.1.3.1 TSAC Hardware Description 

The TSAC is a solid-state device that compresses CO2 using a temperature swing 

adsorption process on a CO2 selective molecular sieve. The TSAC combines the 

functions of a compressor and accumulator in one device. 

2.1.3.1.1 Operating principle 

Fundamental operating principles and designs of adsorption compressors have been 

applied in adsorption refrigeration cycles and heat pumps. Similar to the heat pumps, the 

TSAC operates based on thermal-swing adsorption compression. 

 Figure 4. Work cycle of the TSAC

The typical work cycle of the TSAC is shown in Figure 4. The cycle includes four steps. 

[Ref. 1] 

STEP1: Adsorption of the gas (or gas component from a gas mixture) of interest at a low 

pressure and temperature. Adsorption is an exothermic process. Heat of adsorption is 

removed during this step by cooling the sorbent bed. 

STEP 2: Compression of the adsorbed gas by heating the sorbent. The bed volume is 

isolated during this step. The set point pressure of the process determines the temperature 

limit. The loading of the gas on the sorbent is reduced during heating, raising the pressure 

in the bed. 

STEP 3: Release of the compressed gas at the desired flow rate and pressure as required 

by the processor downstream. Heat must be applied to maintain production as the sorbent 

is depleted of the adsorbed gas. 

STEP 4: Decompression of the gas is achieved by cooling the sorbent. The bed volume is 

again isolated during this step. Temperature is reduced and gas pressure declines to the 

initial point in the work cycle. 

2.1.3.1.2 Process Description 

11
The process flow diagram for the air-cooled TSAC is shown in Figure 5. To obtain 

continuous operation, two identical adsorption chambers (beds) are used. 

 Figure 5 - Flow diagram of the air-cooled TSAC 

The basic function of the TSAC is to remove the carbon dioxide from the CDRA at a 

pressure varying roughly from vacuum to 12 psia and deliver the gas to the Sabatier 

reactor at 21 psia. The carbon dioxide removal assembly (CDRA) includes two CO2 

adsorption beds for removing the carbon dioxide vapor from the cabin air. Like the 

TSAC, these beds function cyclically to switch between their adsorption and desorption 

processes to ensure a continuous operation. The TSAC must be synchronized with the 

CDRA‘s operation cycle to maintain complete regeneration of the CDRA beds and to 

supply compressed CO2 to the Sabatier reactor. The synchronization schedule for the 

4BMS and the TSAC is shown in Table 2. 

Table 2 – TSAC and 4BMS Synchronization Table 

Half Cycle 1 Half Cycle 2 

Time (min) 0 10 134 144 154 278 288 

Desorb to 

TSAC A 

Desorb to 

space 

4BMS Bed A 

Adsorb CO2 from Cabin Air Air-Save

TSAC Bed 

A Produce CO2 Cool Adsorb Compress

Desorb 

to TSAC 

B 

Air 

Save 

Desorb to 

space 

4BMS Bed B 

Adsorb CO2 from Cabin Air 

TSAC Bed B 

Cool Adsorb Compress Produce CO2 

12
Step 4 Step 1 Step 2 Step 3

Half Cycle 1 Half Cycle 2

Figure 6 – TSAC and 4BMS beds temperature and pressure profiles. 

The correspondence for TSAC Bed 2 between Figure 6 and Figure 4 is as follows: Step 4, 

cooling/decompression in preparation for the CO2 intake, occurs from 0 to 10 minutes. 

Step 1 where the TSAC adsorbs CO2 from the 4BMS occurs from 20 to 134 minutes. 

Step 2, compression in preparation for the production step runs from 134 minutes to 144 

minutes. Finally, Step 3, the production step, runs from 144 minutes to 288 minutes. 

Referring to the 4BMS desorbing bed in Figure 6, the segments are as follows: From 0 to 

10 minutes is segment 1, when the desorbing bed is being evacuated to cabin via the air 

save pump and the primary heater is energized. Segment 2 is from 10 to 134 minutes; 

here primary and secondary heaters are energized. The bed is isolated for the first ten 

minutes of segment 2 to allow cooling of the TSAC bed. For the remainder of the 

segment, it is desorbing to the TSAC. Finally, during segment 3, the bed communicates 

with space vacuum for more complete desorption at low pressure. 

2.1.3.1.3 TSAC Development History 

13
Development of the TSA CO2 compressor at NASA ARC was originally started under 

the Mars In-Situ Resource Utilization (ISRU) program. An Engineering prototype of a 

CO2 compressor was developed and tested at NASA ARC under the payload proposal 

PROMISE, which was intended to fly in the 2005 Mars Surveyor Lander. The CO2 

compressor prototype was designed to extract and separate atmospheric gases from the 

Mars environment to produce buffer gases and pure, compressed CO2 for rocket 

propellant production. The CO2 compressor operates based on the TSA technology to 

separate, compress and produce CO2 at a specified rate. The concept of a CO2 

compressor for closing the air loop of an ECLS system was spun-off from the Mars CO2 

compressor design. Three different TSAC compressors were sequentially developed 

during this program with process and equipment improvements implemented in each 

successive build. 

2.1.3.1.4 Water Cooled TSAC 

The first compressor developed utilized water as the cooling medium. This compressor 

was designed with a concept of using three sorbent beds to cyclically adsorb and desorb, 

thus providing a constant sink for the 4BMS to exhaust to, and also a constant source of 

CO2 for the Sabatier. These beds were synchronized to the 90 minute Sabatier cycle. A 

single prototype bed of this configuration was fabricated and tested at NASA Ames 

Research Center in August 2000. 

The operation of each bed is scheduled such that when one bed is available for adsorption 

of CO2 from CDRA, another is ready to produce CO2 for the CRA, and the third bed is 

in a standby or a cooling mode. A flow diagram for the proposed three bed processor is 

shown in Figure 7. 

The complete cycle of this TSAC is 270 minutes, with each desorption cycle taking 90 

minutes. Each TSAC bed is designed to accommodate the full load of CO2 required by 

the CRA, which in this example is one-half the CO2 available from the CDRA. 

CDRA CRA

space vacuum

T P

Figure 7 - Flow diagram of a three-bed TSAC device. Internal pressure is controlled through a feedback 

loop to the heater. Inert gas vent tubes are not shown.

14
The baseline design for the TSAC uses a zeolite adsorbent and a working cycle that is 

shown in Figure 8. The intake cycle begins at a pressure of about 2.7 kPa (0.4 psi) and 

ends at 27 kPa (3.9 psi). The spacecraft coolant loop is used to maintain the temperature 

near 30°C during this step. During pressurization, the coolant flow is shut off and the 

sorbent is heated to approximately 60°C; production occurs at a pressure of 100 kPa (14.5 

psi) and temperatures rising to about 90°C. For depressurization, the coolant is again 

allowed to flow through the device to bring the temperature back to about 30°C. 

18

16

14

12

10

8

6

4

2

0

CO2 loading [wt%]

0 200 400 600 800 1000

pressure [torr]

25°C

50°C

75°C

100°C

175°C

Figure 8 - Adsorption isotherms and compression cycle. 

This cycle provides a working capacity of about 4.6 wt%. From it, a three-bed TSAC was 

sized to meet CDRA and CRA interface requirements for vacuum, CO2 pressure, and 

buffering capacity. 

A summary of the TSAC requirements is shown in Table 3. 

15
Table 3 - Production rates and resource requirements of TSAC sized for two kilograms CO2 production per 

day at 100 kPa. 

Resource Requiremen

t 

Production level 2 kg CO2 / 

day 

Production pressure 100 kPa 

Total mass 22.5 kg 

Average power 150 W 

Peak power 300 W 

Average heat 

rejection 

150 W 

Total volume 25 L 

2.1.3.1.5 Liquid Cooled TSAC 

The next development in the TSAC design was a change of the cooling medium from 

water to a heat transfer fluid known as Paratherm. This heat transfer fluid allowed the bed 

operating temperature to increase thus increasing the working capacity. This comes at the 

expense of added equipment to handle the heat transfer fluid, namely a pump, heat 

exchanger and reservoir. The operating schedule was also modified to reduce the number 

of beds to two. Rather than synchronizing with the Sabatier, the beds were synchronized 

with the 4BMS beds. One TSAC bed was sized to absorb the entire capacity of one 

4BMS bed. 

The two-bed, liquid-cooled, TSAC consists of two identical sorption beds equipped with 

a heater in the middle and cooling coils brazed on the outer surface of the canister. The 

compressor canisters also contain multiple temperature sensors and pressure sensors. 

Pictures of the compressor canister with heating and cooling assemblies are shown in 

Figure 9. 

16
Figure 9 - Heating and cooling assemblies of the TSAC

A flow diagram for the 2-bed, liquid-cooled TSAC is shown in Figure 10. 

Figure 10 - Schematic of 2-bed, liquid-cooled TSAC

The compressor beds are conservatively designed for handling about 2 kg of CO2 per 

day, which is half of the requirement of ISS. Similar to the CDRA, the TSAC beds 

operate in a cyclical fashion. While one bed produces or desorbs CO2 for the Sabatier 

reactor, the other bed continues to adsorb or extract CO2 from the desorbing CDRA bed. 

2.1.3.1.6 Air Cooled TSAC 

The most recent TSAC design iteration was the development of an air cooled bed. Air is 

a safe and practical cooling medium in a spacecraft environment and eliminates all of the 

extra hardware mentioned previously that was needed for the liquid cooled bed. The 

disadvantage of the air cooled bed is that the bed itself is larger to accommodate the air 

cooling passages. However, the bed temperature can be operated up to 250 degrees C 

yielding higher working capacity. 

17
The air-cooled TSAC design consists of multiple air slots and heaters spaced within the 

sorbent bed. A schematic of the TSAC design structure is shown in Figure 3. 

 Figure 11. Schematic of the air-cooled TSAC prototype 

The air-cooled TSAC prototype was designed to produce compressed CO2 at a rate of 8.8 

lb/day at a CO2 loading pressure of about 4psia. The loading pressure of 4psia for TSAC 

is the minimum downstream pressure required for CDRA to regenerate completely within 

the scheduled cycle time (144 minutes). This is only a conservative estimate, derived 

from the characterization data of the CDRA sorbent material. 

The key objective that guided the design and material selection for the TSAC was to 

minimize the heat loss from the compressor to the surroundings and maximize the heat 

transfer from the heated sorbent core to the cooling surface. 

 Figure 12. Air-cooled TSAC prototype 

18
The mechanical design of the TSAC was facilitated with a thermal model to finalize the 

size, material selection and coolant flow rate. 

2.1.3.2 TSAC Integration Characteristics 

In contrast to the mechanical compressor, the TSAC compresses and stores the carbon 

dioxide at the same time, eliminating the need for an accumulator. The CO2 is delivered 

to the Sabatier at a fixed pressure, which is controlled by regulating the temperature of 

the desorbing bed. This fixed delivery pressure eases the requirements on the Sabatier for 

CO2 flow control; i.e. the CO2 modulating valve would have only a 4:1 turndown 

requirement rather than 4:1 on flow and 6:1 on pressure. 

The 4BMS produces a high purity CO2 stream, but it will be contaminated by a small 

amount of nitrogen and oxygen. Because the TSAC is not a flow-through system, there is 

a potential for a buildup of non-adsorbing gases in the compressor. These could form a 

barrier to CO2 adsorption during the intake step. This situation is prevented by 

periodically venting this small amount of non-adsorbing gas to space vacuum via tubing 

between the TSAC beds and the CO2 vent line. 

2.1.4 Sabatier Carbon Dioxide Reduction Subassembly 

2.1.4.1 Sabatier Hardware Description 

The Sabatier Engineering Development Unit (EDU), developed by Hamilton Sundstrand, 

was designed to simulate the proposed flight configuration of the Carbon Dioxide 

Reduction Assembly (CRA) for ISS. As described previously, the CRA is an integral part 

of a closed loop air revitalization system and makes use of waste products, CO2 from a 

4BMS/CDRA and H2 from the OGA, which would otherwise be vented. The CO2 and H2

combine to produce methane (CH4) and water (H2O) as shown in the reaction below. The 

water and methane may then be used for other processes. In the case of ISS, the water 

would be sent to the wastewater bus and processed to potable quality for use by the crew. 

The methane would be vented overboard as a waste product. In future exploration 

missions, the waste methane could be used as a fuel source, or further reduced to carbon 

and hydrogen. 

Equation 1 

 

CO2 + 4 H2 ⇔ CH4 + 2 H2O 

The Sabatier EDU consists of a Sabatier methanation reactor, a condensing heat 

exchanger, a phase separator and accompanying valves and sensors necessary for safe 

operation. The Sabatier EDU was modified substantially after being tested with the 

mechanical compressor and before being tested with the TSAC. The overall function of 

the system was not changed, but the individual component fidelity was improved. The 

19
most current Sabatier EDU schematic is shown here in Figure 13. A description of the 

differences between the two test series is given in the appendix. 

SABATIER

REACTOR

CONDENSING

HEAT

EXCHANGER

T

P

CG CG CONTROLLER

AND EIB

N2 IN

CO2 IN

H2 IN

CH4 VENT

H2O OUT

MFC

P P

P

MFM

T

ΔP

MV202

SVO203 CV204 F201

F001

P002

FCV003

CV004

MFM005 P006-1

F101 SVC102

MFC103

CV104

R401

H402

T403-1,-8

DP405

T404-1,-2

SVO501

FAN502

T407-1,-2

DP409-1,-2

CV305

P304

P601

SVO604

BPR606

SVO608

CG411 CG412

P206

FR205

HX406

T

SVC007

P

ΔP

MV105

ΔP

DRUM

SEPARATOR AND

PUMP L

SVC303

T T

COLD PLATE

COOLANT

IN/OUT

T

P

P106

P006-2

Manual Fill Port

RV207

RV009

RV107

P

L602

CP301

T413-1,-2

SEP411

FR607

T T T T T T T T

N

N414

T

T T410-1,-2

Gas

Sample

Port

BED412

Gas

Sample

Port

SABATIER

REACTOR

CONDENSING

HEAT

EXCHANGER

T

P

CG CG CONTROLLER

AND EIB

N2 IN

CO2 IN

H2 IN

CH4 VENT

H2O OUT

MFC

P P

P

MFM

T

ΔP

MV202

SVO203 CV204 F201

F001

P002

FCV003

CV004

MFM005 P006-1

F101 SVC102

MFC103

CV104

R401

H402

T403-1,-8

DP405

T404-1,-2

SVO501

FAN502

T407-1,-2

DP409-1,-2

CV305

P304

P601

SVO604

BPR606

SVO608

CG411 CG412

P206

FR205

HX406

T

SVC007

P

ΔP

MV105

ΔP

DRUM

SEPARATOR AND

PUMP L

SVC303

T T

COLD PLATE

COOLANT

IN/OUT

T

P

P106

P006-2

Manual Fill Port

RV207

RV009

RV107

P

L602

CP301

T413-1,-2

SEP411

FR607

T T T T T T T T

N

N414

T

T T410-1,-2

Gas

Sample

Port

BED412

Gas

Sample

Port

Figure 13 – Sabatier Engineering Development Unit Schematic 

The Sabatier EDU has two primary modes of operation: process and standby. In process 

mode, inlet gasses flow through the system and methane and water are produced. In 

standby mode, supply gasses are isolated, coolant air is stopped, the unit is evacuated to 

below 1 psia, and the system is isolated. Reactor heaters cycle as required maintaining a 

reactor temperature of approximately 300oF. The Sabatier EDU is operated with excess 

CO2 (approximately 14%) to ensure that all hydrogen is reacted. The nominal molar ratio 

(MR) is 3.5 to 1, H2 to CO2. A hydrogen cylinder and a flow controller were used to 

simulate the delivery of hydrogen from an OGA. An operator sets the hydrogen flow rate, 

and the Sabatier system controller calculates the required carbon dioxide and controls the 

flow to achieve the desired molar ratio. 

The inlet CO2 and H2 gasses react in the catalytic reactor to produce methane and water 

vapor. This is an exothermic reaction that is self limiting at about 1000 F. The aft end of 

the reactor is air cooled to reduce the product exit temperature in order to achieve higher 

reactant conversion. Water vapor in the product stream is condensed in an air-cooled heat 

exchanger. The methane gas and liquid water are separated in a rotary drum phase 

separator. The rotation of the drum imposes an artificial gravity field that efficiently 

separates the two phases. When the delta pressure in the phase separator indicates a high 

level of liquid in the drum, the system controller increases the separator speed and the 

separator pumps the accumulated water to a pressurized water storage tank. The methane 

and excess, un-reacted gasses are vented to a facility combustible gas vent through a 

20
combustible gas compatible vacuum system. The Sabatier system is operated at subambient pressures, as planned for the flight design, to ensure that combustible gasses do 

not leak out to the surrounding atmosphere. 

2.1.4.2 Sabatier Hardware Changes between Tests 

The first series of fully integrated tests included the four bed molecular sieve, the 

mechanical compressor and accumulator, and the Sabatier engineering development unit. 

The Sabatier EDU, in its original configuration, matched the schematic shown here in 

Figure 14. Some of the more prominent features that were upgraded between the first and 

second test series are listed below: 

• Addition of the rotary drum separator and pump with two differential pressure 

sensors for level monitoring. The original Sabatier used a tank as a 1-g separator 

and a small gear pump to transfer the water to the water storage device when the 

separator tank was full. The rotary separator included in the upgrade is of flightlike quality and is the design basis that would be used for a flight installation of 

Sabatier technology. 

• Addition of a liquid sensor in the methane vent line. The original Sabatier had no 

liquid sensor. This sensor was included as a means to gather operational test data 

on the liquid sensor design. 

• Incorporation of a multi-point thermocouple in the reactor bed for data collection. 

The original Sabatier had only two temperature sensors that were used for heater 

control and over-temperature protection. A flight system would rely on only the 

two or three sensors in the hot end of the bed. The Sabatier EDU was upgraded to 

include a multi-point thermocouple in order to gather additional reactor 

performance data during operation, which will lead to improved reactor designs in 

the future. 

• Addition of a flight like modulating valve for CO2 control. The original Sabatier 

EDU used a commercial modulating valve with a stepper motor to control the 

CO2 flow. While this technology performed adequately, it could not be 

considered flight-like. The EDU was upgraded with a flight-like modulating valve 

that uses a variable solenoid to position the valve stem to control the flow. This 

valve was designed and manufactured with flight requirements in mind, including 

redundant seals and manifold mounting. 

• Upgrade of the back pressure regulator to a flight-like design. Again, the original 

back pressure regulator was a commercial-off-the-shelf design. The new regulator 

was designed and manufactured to meet flight requirements including a welded 

diaphragm, manifold mounting and double seals. 

21
SABATIER

REACTOR

CONDENSING

HEAT

EXCHANGER

T

P

CG CG

N2 IN

CO2 IN

H2 IN

CH4 VENT

H2O OUT

LF

CV

MFC

P P

P

T

T

ΔP

MV202

SVO203 CV204 F201

F001

P002 FCV003

CV004 MFM

MFM005 P006

F101

SVC102

MFC103

CV104

R401

H402

T403

DP405

T404

SVO501

FAN502

T407

ST408

DP409

PUMP301

SVC303

P304

P601

RV602 SVO604

RV603 SVO605

BPR606

FR607

SVO608

CG411 CG412

P206

FR205

HX406

T

T T

RV410

SVC007

P

T

ΔP

MV609

MV105

CV305

F406

SABATIER

REACTOR

CONDENSING

HEAT

EXCHANGER

T

P

CG CG

N2 IN

CO2 IN

H2 IN

CH4 VENT

H2O OUT

LF

CV

MFC

P P

P

T

T

ΔP

MV202

SVO203 CV204 F201

F001

P002 FCV003

CV004 MFM

MFM005 P006

F101

SVC102

MFC103

CV104

R401

H402

T403

DP405

T404

SVO501

FAN502

T407

ST408

DP409

PUMP301

SVC303

P304

P601

RV602 SVO604

RV603 SVO605

BPR606

FR607

SVO608

CG411 CG412

P206

FR205

HX406

T

T T

RV410

SVC007

P

T

ΔP

MV609

MV105

CV305

F406

Figure 14 – Original Sabatier EDU Hardware Configuration 

2.1.4.3 Sabatier Integration Characteristics 

The Oxygen Generation Assembly delivers its hydrogen byproduct to the Sabatier. The 

OGA has two hydrogen valves, one that goes directly to the vacuum vent of the ISS and 

the other that interfaces directly with the Sabatier. The control software includes a 

handshake between the OGA and CRA, which requires that both systems have to be 

ready to interact before the valve to the Sabatier is opened. This control software was not 

part of this test series, but has been independently verified. The Sabatier requires carbon 

dioxide pressurized at 18 psia or higher in order to operate. If the CO2 pressure available 

at the interface is too low, or the OGA is not ready, the Sabatier system will transition to 

Standby mode. 

The Sabatier CRA is designed to operate below ambient pressure. This prevents leakage 

of flammable gas to the cabin atmosphere after two failures. In order to test the system, a 

vacuum must be drawn on the methane vent line. This vacuum source must be 

compatible with methane and hydrogen and pose no explosion hazard. A water ejector 

setup was used in this integrated testing to simulate the vacuum source. The water ejector 

could only achieve about 4 psia under maximum flowing conditions; however, this did 

not seem to affect the system operating parameters elsewhere in the Sabatier system. 

22
2.1.5 Support Hardware Configuration 

2.1.5.1 4-BMS Inlet ppCO2 Control – Metabolic Load Simulation 

The metabolic load contribution to the integrated tests was created by injecting CO2 

according to a mass flow schedule into the air stream at the inlet to the 4-bed molecular 

sieve. Some of the testing was done with constant CO2 concentration, while other tests 

were designed to mimic the time profile predicted for a volume with crew performing 

various activities. 

During testing, CO2 was injected into the 4BMS inlet per the test matrices in the two 

following tables: Table 4 lists the conditions used for the mechanical compressor test and 

Table 5 lists the conditions used for the TSAC test. Test conditions ranged from a 2.3-

person crew to an 8.3 person crew (CO2 partial pressure of 1.5 to 5.3 mmHg 

respectively). 

Table 4 - Test conditions for mechanical compressor test. Vozdukh Operation (on=25% CO2 load) H2/CO2 Molar Ratio 

Day/night 

Duration (min) 

4BMS CO2 

Inlet 

Concentration 

(mmHg)

Comp Speed 

(rpm) 

US H2 Feed 

Rate (slpm)* 

Min. Number 

HC Required 

CO2 Feed 

Rate (slpm) 

Day/night 

Cyclic or 

Continuous 

Russian 

Elecktron 

Load (EP) 

Modeling 

CDRA 

EP total 

Location 

TP 

1** 1.5 3 off 0 2.461 3.5 0.703 cont 3 1000 - 53/37 

2** 1.5 3 off 0 4.179 3.5 1.194 day/night 4 1000 - 53/37 

3** 1.5 3 off 0 4.179 3.5 1.194 day/night 4 800 - 53/37 

4 3.5 7.25 on 2 4.289 3.5 1.225 continuous 3 1000 - 53/37 

5 3.5 7.25 on 2 7.282 3.5 2.081 day/night 4 1000 - 53/37 

6 3.5 7.25 on 2 7.282 3.5 2.081 day/night 4 800 - 53/37 

met 

profile 8 6 off 0 8.724 3.5 2.493 day/night 50 hrs 1000 Node3 53/37 

met 

profile 10 7.25 on 2 7.282 3.5 2.081 day/night 50 

hrs 

Node 

3 1000 53/37 

met 11 profile 7.25 on 2 7.282 3.5 2.081 day/night 48 

hrs 1000 Lab 53/37 

*includes air leakage compensation of 0.24 lb/day air 

** tests repeated after air leakage detected 

23
Table 5 – Test conditions for the TSAC test. 

US H2 Feed Rate 

slpm (lb/hr) 

TSAC Production 

Pressure kPa 

(psia) 

4BMS Inlet CO2 

Conc. 

Sabatier CO2 

Feed Rate slpm 

(lb/hr) 

TSAC Loading 

Pressure kPa 

(psia) 

H2/CO2 Molar 

Ratio 

Test Point # 

4BMS CO2 

Equiv. Pers. 

Loading 

kg/day 

(lb/day) 

MmHg 

(%) 

EP 

Test Point Description 

Integrated 4BMS/TSAC 

baseline test 

133 

1 8 (17.6) -- 8 27.6 (4) (19.3) -- -- -- 

Integrated 4BMS/TSAC at 

reduced CO2 loading 

133 

2 5 (11) -- 5 27.6 (4) (19.3) -- -- -- 

Integrated 4BMS/TSAC at 

reduced CO2 loading 

133 

3 4 (8.8) -- 4 TBD (19.3) -- -- -- 

Integrated 4BMS/TSAC at 

reduced CO2 loading 

133 

4 4 (8.8) -- 4 TBD (19.3) -- -- -- 

Integrated 4BMS/TSAC at 

reduced CO2 loading 

133 

5 3 (6.6) -- 3 TBD (19.3) -- -- -- 

Integrated 4BMS/TSAC at 

reduced CO2 loading 

pressure 

133 

6 5 (11) -- 5 41.4 (6) (19.3) -- -- -- 

Integrated 4BMS/ TSAC/ 

Sabatier at TSAC baseline 

conditions for TSAC health 

check 

The test points in Table 4 reflect the test conditions used for the mechanical compressor 

testing. During cyclic operation (all test points except 1 and 3), the system mimics ISS 

protocols for power savings during orbital night. During the “night” cycle the 4BMS 

desorbing bed heaters are turned off and the OGA goes to standby, stopping H2 

production and signaling the Sabatier to transition into standby as well. 

For test points 1 through 6, the CO2 load was constant and was set at the average 

metabolic load generation rate for the number of crew listed in the table. For test points 8, 

10, and 11 in Table 4, 4BMS inlet CO2 levels were varied to simulate variations in ISS 

atmosphere, which result from changes in crew locations and activities. These transient 

7 -- 

5.3 

(0.7%) 

124 

(18) 

6.766 

(0.0798) 

1.933 

8.3 -- 3.5 (0.502) 

Integrated 4BMS/ TSAC/ 

Sabatier for comparison to 

mechanical compressor test 

point #2 

3.5 

(0.46%) 

124 

(18) 

4.459 

8 -- 5.46 -- (0.053) 3.5 

1.274 

(0.331) 

Integrated 4BMS/ TSAC/ 

Sabatier for comparison to 

mechanical compressor test 

point #3 

1.5 

(0.2%) 

124 

(18) 

1.925 

9 -- 2.34 -- (0.023) 3.5 

0.550 

(0.143) 

Integrated 4BMS/ TSAC/ 

Sabatier Lunar night scenario, 

non-optimal TSAC shutdown/ 

startup 10 -- 

2.52 

(0.33%) 

124 

(18) 

3.273 

4 -- (0.037) 3.5 

0.935 

(0.243) 

Integrated 4BMS/ TSAC/ 

Sabatier EVA full crew 

departure scenario, CO2 

regenerated to cabin 

Per 

profile 

124 

(18) 

3.273 

11 -- 4 -- (0.039) 3.5 

0.935 

(0.243) 

24
cabin CO2 levels, or metabolic profiles, were generated using an integrated model 

developed at NASA JSC. The model allows for atmosphere mixing and air revitalization 

hardware analysis of multiple integrated modules as configured on ISS [3] or as a 

potential Lunar base. Crewmember location and metabolic activity levels were based on 

the location of sleep stations, work stations, galley, and exercise equipment. The CO2 

metabolic generation rate was defined by NASA document SSP41000 [4]. 

The model provided transient cabin CO2 levels, or metabolic profiles, for the United 

States Operating Segment (USOS) modules that will contain carbon dioxide removal 

units (Lab and Node 3) when ISS assembly is complete. Testing was conducted to 

evaluate integrated performance for the two different ISS CDRA locations. A generalized 

representation of the model is shown below. 

Figure 15 - Nodal representation of ISS for CO2 concentration prediction. 

Figure 13 is an example of a predicted crew metabolic profile including sleep, waking 

and exercising periods. This graph represents the gross overall CO2 load generated 

within the ISS for the 6 crew members. Figure 14 illustrates the predicted atmosphere 

concentration resulting from the crew activities and the calculated injection flow rate 

needed to simulate the mission profile. 

25
Metabolic Profiles - Max Crew Size

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0 4 8 12 16 20 24

Time (hrs)

CO2 loading, lb/hr

Crew 1

Crew 2

Crew 3

Crew 4

Crew 5

Crew 6

NOTE - crew 4 and 5 have the same profile.

Figure 16 - Example metabolic load profile 

CO2 Injection Rate to Simulate Metabolic Profile

0

0.5

1

1.5

2

2.5

3

3.5

4

59.5 60 60.5 61 61.5 62

Time (days) 

CO2 Injection Flow Rate (slpm)

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

4BMS Inlet CO2 Concentration (%)

Concentration

Injection Rate

Figure 17 - Example of Metabolic Load Profile CO2 Injection Rate 

26
The data in Table 5 reflects the test conditions used for the TSAC testing. For the TSAC 

testing, the system was configured to be always in “daylight”, in other words, there was 

no nighttime disabling of heaters and idling of the hydrogen generation. These conditions 

were set to simulate a Lunar habitat. For test points 10 and 11, 4BMS inlet CO2 levels 

were varied to simulate variations in a lunar habitat atmosphere based on crew locations 

and activities. The model used for ISS CO2 concentrations was modified to represent a 

Lunar habitat. Figure 16 shows the resulting CO2 concentration profile for the simulation 

of the Lunar EVA activity. 

TSAC CO2 Injection Rate

0

0.5

1

1.5

2

2.5

3

3.5

4

27 27.5 28 28.5 29 29.5 30 30.5

Time (days)

CO2 Injection Rate (slpm)

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

4BMS Inlet CO2 Concentration (%)

Injection Rate

Concentration

Figure 18 - CO2 Concentration for Siumulated Lunar EVA Profile 

27
2.1.5.2 4BMS venting 

When a 4BMS bed is desorbing, the compressor operation is governed by a set of 

operating rules based on the suction and discharge pressure. These rules have been 

established to optimize the compressor operation, including minimizing compressor 

power and compressor operating time without causing starvation of the Sabatier. These 

compressor rules allow the compressor to turn off while the 4BMS bed is still desorbing. 

Within the 4BMS, there are check valves that are closed when the bed is under vacuum 

and open when the bed is flowing cabin air. These check valves will crack open and leak 

CO2 back to the cabin atmosphere if the bed pressure gets too high. To prevent the check 

valves from opening, the standoff vacuum valve is used to vent the bed pressure when the 

compressor is not operating. The rules governing the operation of this valve are shown in 

Table 6. 

The desorbing sorbent bed pressure must remain low enough to maintain closing force on 

the flapper-style check valve. (Refer back to Figure 2 in Section 2.1.1) This pressure was 

set at 8 psia during the mechanical compressor testing and 12 psia during the TSAC 

testing. During 4BMS venting, the valve V2, shown in Figure 17 below, functions as the 

vent CO2 valve listed in the table. 

During high metabolic load cases, the accumulator often becomes full and the vent valve 

has to open to relieve the pressure in the 4BMS desorbing bed. Figure 18 shows how the 

vent valve is activated multiple times during each 4BMS half cycle. This would cause 

unnecessary wear on the valve. The actual Space Station implementation of this venting 

control will open the valve and leave it open until the end of the half cycle. This keeps 

the number of valve cycles at one actuation per half cycle. More CO2 is vented to 

vacuum, however, as seen in the chart, when the CO2 loading is high, there is more than 

enough CO2 available and it is not necessary to capture all of the CO2 from the 4BMS. 

28
Simplified Schematic of Ground Test Hardware

V209

V2

Vent Line

CDRA

To Vacuum

V209 Air Save V200

LMS

Space Vacuum

Simulator

V2

Facility

Vent

Sab

EDU

N2

Vacuum 

vent

PG

Venturi

Vac

Vent

H2

Bottle/

regulator

H2

Bottle/

regulator

CO2 inlet

TSAC

CDRA

To Vacuum

V209 Air Save V200

LMS

Space Vacuum

Simulator

V2

Facility

Vent

Sab

EDU

N2

Vacuum 

vent

PGPG

Venturi

Vac

Vent

H2

Bottle/

regulator

H2

Bottle/

regulator

CO2 inlet

TSAC

V209

V2

Vent Line

CDRA

To Vacuum

V209 Air Save V200

LMS

Space Vacuum

Simulator

V2

Facility

Vent

Sab

EDU

N2

Vacuum 

vent

PG

Venturi

Vac

Vent

H2

Bottle/

regulator

H2

Bottle/

regulator

CO2 inlet

TSAC

CDRA

To Vacuum

V209 Air Save V200

LMS

Space Vacuum

Simulator

V2

Facility

Vent

Sab

EDU

H2

Bottle/

regulator

N2

Vacuum 

vent

H2

Bottle/

regulator

CO2 inlet

PGPG

Venturi

Vac

Vent

TSAC

Figure 19 - Integration of ARS Components 

29
Table 6 – Standoff Valve Operating Rules 

Time in Vent Valve Command 

Cycle 

(minutes) 

Decision Criteria ISS 

Implementation Integrated Test 

0-10 ALWAYS CLOSED CLOSED 

Psuction <8 AND Compressor OFF CLOSED CLOSED 

Psuction < 10 AND Compressor ON CLOSED CLOSED 

OPEN until end 

of half cycle 

10-134 Psuction > 8 AND Compressor OFF OPEN for 20 sec 

OPEN until end 

of half cycle 

Psuction > 10 AND Compressor ON OPEN for 20 sec 

134-144 ALWAYS OPEN OPEN 

Vent Valve Operation at High CO2 Rates

0

1

2

3

4

5

6

7

8

9

10

45.4 45.6 45.8 46 46.2 46.4 46.6 46.8

Time (days)

Pressure

0

20

40

60

80

100

120

140

Vacuum Pressure Accumulator Pressure

Figure 20 - High CO2 rate requires excessive activation of vent valve. 

30
2.1.5.3 Sampling 

Influent CO2 and product Sabatier gasses were sampled at least once per test point and 

measured for purity. Sabatier product water was also collected once per test point for 

analysis. Gas samples were taken of the CDRA inlet, Sabatier reactor inlet and reactor 

outlet. Table 7 lists the test parameters for each sample type. This data is detailed in the 

results section for each test configuration. 

Table 7 - Fluid Composition Analysis 

Sample Type Analysis 

Sabatier Inlet Concentrated 

CO2 

CO2. O2. N2 (%) 

Sabatier Product Outlet CO2, CH4, H2, O2, N2 (%) 

Sabatier Product Water Total Carbon, Total Inorganic 

Carbon, Total Organic Carbon, 

pH, Conductivity 

2.1.5.4 CO2 Moisture Content 

Moisture content of the concentrated CO2 from the 4BMS is a concern for the 

mechanical compressor since the moisture can condense in the chambers of the 

compressor. Two independent tests were conducted to quantify the amount of moisture in 

the CO2 from this test equipment. 

One test used a low moisture analyzer to measure the quantity of water vapor in the CO2 

as it was evolved from the 4BMS desiccant. The instrument is a tunable infrared diode 

laser differential absorption spectrometer (TILDAS) provided by the NASA Glenn 

Research Center. A schematic of the moisture measurement test setup is shown in Figure 

21. The box labeled “Moisture Measurement” indicates the location where the TILDAS 

instrument was connected to the system. The TILDAS was used to measure moisture 

concentration in the CDRA product carbon dioxide during both continuous day and 

day/night simulated operation. 

31
CDRA

To Vacuum

P

TP

V209 Air Save

V200

Mechanical 

Compressor 

Simulator

LMS

Space Vacuum

Pump Simulator

PT

TP

Dew 

Point

TP

Flow

V2 V3

Moisture Measurement

V4

Bottled

N2

CDRA

To Vacuum

P

TP

V209 Air Save

V200

Mechanical 

Compressor 

Simulator

LMS

Space Vacuum

Pump Simulator

PT

TP

Dew 

Point

TP

Flow

V2 V3

Moisture Measurement

V4

Bottled

N2

Figure 21 – Test setup of CDRA product CO2 moisture measurement using TILDAS. 

The other test involved running the compressor from the desorbing CDRA to various 

fixed discharge pressures and measuring the resulting dew point. The discharge pressure 

was set to 20, 47.5, 75, 102.5 and 130 psia during different test points. The compressor 

on/off operation was still controlled based on the Compressor Operating Rules defined in 

Table 1 of Section 2.1.3. 

2.2 Integrated Test Using the Mechanical Compressor 

2.2.1 Overall Test Plan Objectives 

The integration tests using the mechanical compressor were designed specifically to 

determine how the hardware would operate in the Space Station configuration. The Space 

Station currently has a 4BMS CDRA installed in the Lab Module. An Oxygen Generator 

was launched July 2006 and activated in July 2007. The OGA is also installed in the Lab 

Module. The operating conditions of the Space Station were used to develop the test 

matrix in Table 1. 

32
In addition to the missions operations described below, test parameters were also established as a result of 

modeling of the systems that was being conducted in parallel to the test program. A FORTRAN program 

was developed by the NASA Johnson Space Center to simulate the 4BMS, mechanical compressor and 

accumulator. During the course of testing, the test data was correlated to the model predictions. 

2.2.1.1 Test Requirements Based on ISS Implementation 

The Sabatier design points detailed in Table 8 define operating conditions that serve as a 

simple baseline around which the Sabatier was designed to optimize water recovery 

performance. The Sabatier must be capable of responding to the variability of the full 

flow regime of both feed gases and continue operating robustly without compromising 

the life of any components. The interface conditions described next set the boundary 

conditions for the operation of the different subsystems and were used to define the test 

conditions. 

The following assumptions were used as the basis for the flow rates and settings used in 

the test points: 

Oxygen / Hydrogen Generation Rates 

The OGA is required to produce oxygen for the station at a commanded rate between 

0.212 and 0.85 lb/hr. The command to the OGA will be from the station level controller 

that will request 25% to 100% of the maximum power setting. Crew consumption of 

oxygen is nominally 1.84 lb O2/crew-day. This translates to 0.23 lb/crew-day of 

hydrogen that is delivered by the OGA to the Sabatier. Air leakage from the station is 

also made up by oxygen from the OGA and nitrogen from storage tanks. A nominal 

leakage rate of 0.24 lb/day of air (0.05 lb/day O2) was assumed, which translates to an 

additional 0.0063 lb/day of hydrogen delivered. The nominal crew size expected when 

the Sabatier is initially installed on station is 3 crew, the max expected is 6 crew plus 1.25 

EP worth of animals. 

Since the OGA is a high power user, it will likely only operate during the daylight time of 

the Space Station orbit. At the worst case azimuth, the available operating time is 53 

minutes out of a 90 minute period. The daily average hydrogen flow rate is therefore 

multiplied by 90/53 to arrive at the instantaneous flow rates given in Table 8. 

CO2 Generation / Removal 

CO2 generation by the crew is 2.2 lb CO2/crew-day. CO2 is desorbed from the 4BMS 

and is compressed by the compressor into an accumulator. The beds of the TSA 

compressor act as an accumulator and no external device is necessary. The mechanical 

compressor stores CO2 in a tank so that the wave of CO2 desorbed from the 4BMS over 

a short time span can be delivered to the Sabatier at a fixed rate over a longer duration. 

The CO2 feed rates given in Table 8 are based on the crew size and the operating 

schedule (continuous or day/night). The day/night flow rates are 90/53 times the 

continuous rates per crew member. The contribution of CO2 lost due to station leakage is 

considered insignificant and not included in the calculations. 

The concentration of CO2 at the inlet of the 4BMS to achieve the desired rate of CO2 

removal was obtained from a Fortran model of the 4BMS. The model and CO2 inlet 

control are described in more detail in Section 2.1.5.1. The model predicted the 

33
atmospheric steady state concentration given a specific crew size and the actual operating 

conditions of the 4BMS. The model did not include adsorption/desorption of CO2 onto 

the desiccant beds. The initial prediction of 1.5 mmHg for a crew size of 3 turned out to 

be low, and the CO2 removal rate did not match the flow rate of hydrogen available to 

the Sabatier for the first three test points. These test points were later repeated with a 

different CO2 feed concentration. 

The graph below shows the CO2 concentration at the inlet of the 4BMS for one of the 

metabolic load cases. The concentration is calculated from the predicted crew activity 

and location coupled with the effectiveness of the 4BMS. The tall spikes in 

concentration are the result of the daily sensor calibration. The small spikes are due to the 

valves changing position between adsorbing bed cycles. 

Metabolic Profile CO2 Concentration to 4BMS

0

0.2

0.4

0.6

0.8

1

1.2

59.5 60 60.5 61 61.5 62

Time (days)

CO2 Concentration (%)

Figure 22 – CO2 inlet concentration fed to 4BMS for metabolic load profile case. 

Load Sharing between US and Russian Hardware 

Some assumptions had to be made to establish the load sharing of Russian and US life 

support equipment on the Space Station. Since the Russian and US CO2 removal devices 

will be operating from the same mixed atmosphere aboard the Space Station, the split of 

CO2 concentrated by each system is a function of each one’s removal efficiency and the 

total amount of CO2 available. The Russian CO2 removal system (Vozdukh) 

specification requires that the CO2 partial pressure be maintained at 5.3 mmHg with a 

CO2 load of 3 EP. This can be considered the worst case performance point as actual 

Station data indicates that the CO2 partial pressure with the Vozdukh only operating is 

between 3.5 and 4.0 mmHg. The Station CDRA performance gives 3.0 mmHg pCO2 

34
with a 5.29 EP CO2 load. The following equation is used to calculate the removal split 

when both systems are operating at a given metabolic load: 

metabolic 

load

flow 

rate

removal 

rate

molar fraction 

of CO2 Vozdukh

= X X +

flow 

rate

removal 

rate

molar fraction 

of CO2

CDRA

X X metabolic 

load

flow 

rate

removal 

rate

molar fraction 

of CO2 Vozdukh

= X X +

flow 

rate

removal 

rate

molar fraction 

of CO2

CDRA

X X

Solving for the removal fraction yields approximately 25% Vozdukh and 75% CDRA, 

given the previous minimum Vozdukh performance. At actual performance levels of the 

Vozdukh, the split is really about 32.5% and 67.5%. 

Crew Size 

The crew sizes selected for ISS simulation testing include the current 3 person crew, a 

future planned 6 person crew when the station assembly is completed and a load of 7.25 

EP which reflects 6 crew plus animals. 

2.2.2 Description of Test Plan Details 

2.2.2.1 Integrated Test Schematic 

35
Simplified Schematic of ISS Life Support Hardware

Node 3

Bulkhead

AR

Rack

P

Adsorbing

5A Bed

Desorbing

5A Bed

Desorbing

Desiccant

Bed

Precooler

Adsorbing

Desiccant

Bed

Carbon Dioxide Removal

Assembly (CDRA)

CH4/CO2

P

CO2

Air

from

CCAA

Air to

CCAA

Inlet

H2O

H2

OGS

Rack

CO2

ACCUMULATOR Carbon Dioxide Reactor

Assembly (CRA)

COMPRESSOR

Sabatier

Reactor

Condensing

Heat

Exchanger

P P

Oxygen Generator H2 Assembly (OGA)

P

P H2O

M

P

M

P

STANDOFF

V209

V2

V3 P002

P000

Figure 23 – Simplified Schematic of CDRA and CRA as intended to be integrated on ISS. 

Figure 23 above shows simplified schematics of the CDRA and the CRA as they would 

be installed on the International Space Station. The highlighted components are shown 

with the component numbers as used in the ground integration testing. Figure 24 below 

is a schematic of the ground-integrated system with the same control components 

highlighted. 

36
Simplified Schematic of Ground Test Hardware

CDRA

To Vacuum

V209 Air Save V200

LMS

Space Vacuum

Simulator

PT

TP1

V2

V3

Accum

Facility

Vent Dew 

Point

HV1

HV2

BPRV1

FM1

TP2

HV3

CO2

Bottle

Sab

EDU

HV4

BPRV2

SVC007

PT P002

N2

H2O product

to weight 

scale

Vacuum vent

RV@150 psia

HV5

PG

Venturi

Vac

Vent

H2

Bottle/

regulator

H2

Bottle/

regulator

CO2

Mechanical

Piston Compressor

FM2

Coolant in/out

HV6

P000

CDRA

To Vacuum

V209 Air Save V200

LMS

Space Vacuum

Simulator

PT

TP1

V2

V3

Accum

Facility

Vent Dew 

Point

HV1

HV2

BPRV1

FM1

TP2

HV3

CO2

Bottle

Sab

EDU

HV4

BPRV2

SVC007

PT P002

N2

H2O product

to weight 

scale

Vacuum vent

RV@150 psia

HV5

PG

Venturi

Vac

Vent

H2

Bottle/

regulator

H2

Bottle/

regulator

CO2

Mechanical

Piston Compressor

FM2

Coolant in/out

HV6

P000

V209

Figure 24 – Integrated Test Schematic – 4BMS, Mechanical Compressor, Accumulator, Sabatier 

These components control the interaction between the different systems as follows: 

• V209 – this 3-way valve switches the desorbing 4BMS bed from air-save to vent. 

Air save is the first 10 minutes of the desorbing half cycle before CO2 is evolved 

from the bed. After air save, the valve switches to deliver CO2 to the vent line. 

• V2 – this shut-off valve is in the standoff of the space station. When this valve is 

open, the desorbing CO2 is vented to space vacuum. This valve must be 

commanded closed by the supervisory controller in order for the compressor to be 

able to draw the CO2 from the bed. If there is excess CO2 in the 4BMS that is not 

removed by the compressor, this valve opens to direct the excess to vent. 

• P000 – this pressure sensor is located within the CO2 Management Subsystem 

(CMS) within the CO2 Reduction Assembly (CRA). This sensor measures the 

pressure of the desorbing bed, which is also the compressor suction pressure. 

• V3 – this valve is also in the CMS portion of the CRA on the suction side of the 

compressor. Whenever the compressor is commanded to operate, V3 is opened. 

• P002 – this pressure sensor is in the CRA and is used by both the CO2 

Management Subsystem (CMS) and Sabatier Reactor Subsystem (SRS). This 

sensor measures the quantity of CO2 in the accumulator. It is used to tell the 

compressor when to turn on and off, and also tells the Sabatier when there is 

enough CO2 in the accumulator to process. 

• SVC007 - Valve SVC007, inside the Sabatier, opened to allow CO2 to flow when 

the Sabatier was in its processing state. 

• CO2 Bottle – for tests that did not utilize the 4BMS (compressor mapping, for 

example), bottled CO2 was used as the source by closing HV6 and opening HV4. 

V2

P000

V3

P002

37
• Accumulator - The compressor delivered CO2 to the Sabatier/Accumulator inlet. 

The accumulator is simply a buffer volume that fills and empties when the 

compressor flow is greater or less than the Sabatier usage rate. 

The 4BMS was operated in the nominal ISS CDRA mode. Half-cycle time was 144 

minutes and process air flowrate was 95 lbs/hour average. For the last 10 minutes of the 

desorb cycle, the desorbing bed was exposed directly to the space vacuum simulator 

pump. This would be the recommended operating procedure for ISS in order to fully 

desorb the 4BMS bed prior to its next adsorption cycle. The CO2 loading profile to the 

4BMS is described in Section 2.1.5.1. 

2.2.2.2 Single Component Tests 

2.2.2.2.1 4BMS 

The 4 bed molecular sieve system was tested alone to verify that it met the removal 

capability that had been demonstrated in prior baseline cases. The test conditions are 

listed in the table below. The baseline testing was repeated throughout the project to 

ensure that there was no performance degradation as a result of the integration. 

Test Case # ppCO2 Inlet CO2 Removal 

Rate 

Test Duration 

torr 

Lb/hr 

4BMS Baseline, 3 

EP 

1.48 0.23 8 hour min 

4BMS Baseline, 6 

EP 

3.39 0.52 8 hour min 

2.2.2.2.2 Mechanical Compressor 

This configuration tested the compressor as a stand-alone item. The test results would be 

compared to the vendor test results prior to delivery of the compressor to NASA. This 

testing is referred to in the test plan as “Compressor Health Check.” The Table below list 

the test conditions. 

Test 

Point 

Suction 

Pressure 

Discharge 

Pressure 

Pump 

Speed 

(psia) (psia) (RPM) 

1 4 20 1000 

2 4 130 1000 

Each test point will last a minimum of 5 minutes. 

38
2.2.2.2.3 Sabatier 

Sabatier stand alone tests were performed to generate a baseline of the Sabatier efficiency 

for comparison to previous Sabatier testing and to compare to the performance achieved 

during the integrated tests. The test conditions used are listed in the table below. 

Test 

Point 

JSC Test 

Point 

Reference 

CO2 

Supply 

Pressure 

Day 

Cycle 

Time 

Night 

Cycle 

Time 

US 

H2 

Feed 

Rate 

(lb/hr)

US 

H2 

Feed 

Rate 

H2/CO2 

Molar 

Ratio 

Sabatier 

CO2 

Feed 

Rate 

Sabatier 

CO2 

Feed 

Rate 

Cyclic or 

Continuous

(psia) (min) (min)

(slpm) (lb/hr) (slpm) 

1 3 85 - - 0.031 2.660 3.5 0.197 0.760 Continuous

2 7 25 53 10 0.106 9.000 3.5 0.567 2.570 Cyclic 

2.2.2.3 4BMS + Mechanical Compressor + Accumulator 

Two test objectives were completed in this configuration. The purpose of the first test 

was to measure the dew point of the product CO2 to determine if there would be 

condensation in either the compressor or the accumulator during operation. The 4BMS 

was operated with constant 0.2% CO2 inlet concentration. The compressor operated with 

the varying inlet pressure as produced by the 4BMS and with fixed outlet pressures and 

set by a backpressure regulator. The outlet pressures were set to 20, 47.5, 75, 102.5, and 

130 psia. 

39
Simplified Schematic of Ground Test Hardware

CDRA

To Vacuum

V209 Air Save V200

LMS

Space Vacuum

Simulator

PT

TP1

V2

V3

Accum

Facility

Vent Dew 

Point

HV1

HV2

BPRV1

FM1

TP2

HV3

CO2

Bottle

Sab

EDU

HV4

BPRV2

SVC007

PT P002

N2

H2O product

to weight 

scale

Vacuum vent

RV@150 psia

HV5

PG

Venturi

Vac

Vent

H2

Bottle/

regulator

H2

Bottle/

regulator

CO2

Mechanical

Piston Compressor

FM2

Coolant in/out

HV6

P000

CDRA

To Vacuum

V209 Air Save V200

LMS

Space Vacuum

Simulator

PT

TP1

V2

V3

Accum

Facility

Vent Dew 

Point

HV1

HV2

BPRV1

FM1

TP2

HV3

CO2

Bottle

Sab

EDU

HV4

BPRV2

SVC007

PT P002

N2

H2O product

to weight 

scale

Vacuum vent

RV@150 psia

HV5

PG

Venturi

Vac

Vent

H2

Bottle/

regulator

H2

Bottle/

regulator

CO2

Mechanical

Piston Compressor

FM2

Coolant in/out

HV6

P000

V209

V2

P000

V3

Open

P002

Controlled by 

4BMS for 

venting Controlled by 

Sabatier for 

compressor 

control

Closed

Closed

Open

Figure 25 – Hardware configuration for 4BMS and compressor only tests. 

In this test configuration, the 4BMS and compressor were integrated together with no 

other systems operating. The hand valves that connect the CO2 tank (HV4) and the 

accumulator (HV5) were closed. The Sabatier was powered on, but not processing so that 

it could monitor the compressor inlet (P000) and outlet (P002) pressures, and operate the 

compressor and inlet valve (V3). The back pressure regulator (BPRV1) was set to 

varying pressures according to the test plan. A closed hand valve isolated the 

accumulator. 

The other test was to start up the compressor under vacuum. Normally, the compressor 

discharge pressure ins never less than 18 psia, however a system self check is being 

considered that would evacuate the accumulator and compressor exit. The purpose of the 

test was to determine if there were any operational issues with the compressor. 

 

2.2.2.3.1 4BMS + Mechanical Compressor + Accumulator + 

Sabatier 

Table 8 below details the test conditions used for the integration of the mechanical 

compressor with the 4BMS and the Sabatier. The column data in the table is as follows: 

40
• Column 1 is the test point number used for recording test conditions and resulting 

data. 

• Column 2 is the constant CO2 concentration fed to the 4BMS at the cabin air flow 

inlet. These tests were run open loop, therefore the feed concentration to the 

4BMS was set by a CO2 mass flow controller with measured CO2 concentration 

feedback to the mass flow control setpoint. 

• Column 3, EP, is Equivalent Persons. Early mathematical modeling of the 4BMS 

predicted that 1.5 mmHg partial pressure of CO2 fed to the inlet of the 4BMS 

would result in the equivalent CO2 removal rate of 3 EP generation rate. After 

testing this condition and analyzing the data, it was found that 1.5 mmHg inlet 

resulted in only 2.3 EP worth of CO2 collected and delivered to the Sabatier for 

processing. The correction to the inlet feed rate was made in later tests. 

• Column 4 indicates the status of a virtual Vozdukh, the Russian CO2 removal 

system. When the Vozdukh is off, all of the CO2 from the entire crew is collected 

and concentrated by the US CRDA equipment and available for processing by the 

Sabatier. When the Vozdukh is on, 25% of the crew load of CO2 is collected by 

the Russian equipment and therefore not available to the Sabatier. 

• Column 5 indicates the status of a virtual Elektron, the Russian oxygen generator. 

The contributing level of the Elektron is given in EP of oxygen delivered by the 

Elektron. When the Elektron is producing oxygen, the US OGA production level 

is lowered by the same amount and therefore the hydrogen available to the 

Sabatier for processing is decreased. These contributions from other hardware 

become important when determining the amount of water recovery available from 

the Sabatier system. 

• Column 6 is the US hydrogen feed rate to the Sabatier. This value is the amount 

of hydrogen generated along with the rate of oxygen generated to make up for 

losses. The oxygen consumption rate is calculated from the crew size, the 

contribution supplied by the Elektron (subtracted out) and a component for make 

up oxygen for station air leakage amounting to 0.24 lb/day. The value of 

hydrogen in column 6 is used as the set point of the hydrogen mass flow 

controller in the Sabatier EDU. 

• Column 7 is the set point for hydrogen/CO2 molar ratio. While this number is a 

variable in the Sabatier control program, it was set to a constant 3.5 for these tests. 

The Sabatier calculates the control set point for its CO2 control valve based on the 

hydrogen feed rate and the molar ratio. 

• Column 8 is the CO2 feed rate. This is the average feed rate of CO2 that the 

Sabatier should be calculating for the set point of its control valve. 

• Column 9 indicates day/night cyclic or continuous operation. When the integrated 

system is operating in day/night mode, the OGA transitions to a standby mode 

when the space station is in the dark side of the orbit and power is scarce. When 

the station is back in the daylight side of the orbit, the OGA transitions back to 

Process mode. Hydrogen is only available to the Sabatier when the OGA is in 

Process mode. The times used for the duration of the day and night portions of the 

orbit are given in Column 13. 

41
• Column 10 indicates the minimum number of half cycles (HC) required to reach 

nominal steady state conditions for the test point. These values were used to 

schedule the test point in order to complete the series. 

• Column 11 is the compressor speed. Determining the correct size for the 

mechanical compressor was one of the objectives of this test program. Adjusting 

the speed of the compressor was a simple method of adjusting the compressor 

capacity to see its effect on integration. A compressor designed for the flight 

application of this system would be made with smaller pistons if necessary rather 

than slower speed. Motor speeds under 1000 rpm have major impacts on sizing of 

EMI filters in the controller. 

• Column 12 indicates the location of the CDRA (the station 4BMS) in the model 

used to develop the metabolic profile. The location of the CO2 removal 

equipment with respect to the location of crew members during different activities 

affects the instantaneous concentration of CO2 seen at the 4BMS inlet. 

• Column 13, as described previously, is the duration in minutes of the daylight and 

night portions of the space station orbit. 

Table 8 – Integrated Test Matrix Input Parameters, Mechanical Compressor Test Vozdukh Operation (on=25% CO2 load) H2/CO2 Molar Ratio 

Day/night 

Duration (min) 

4BMS CO2 

Inlet 

Concentration 

(mmHg)

Comp Speed 

(rpm) 

US H2 Feed 

Rate (slpm)* 

Min. Number 

HC Required 

CO2 Feed 

Rate (slpm) 

Day/night 

Cyclic or 

Continuous 

Russian 

Elecktron 

Load (EP) 

Modeling 

CDRA 

EP total 

Location 

TP 

1** 1.5 3 off 0 2.461 3.5 0.703 cont 3 1000 - 53/37 

2** 1.5 3 off 0 4.179 3.5 1.194 day/night 4 1000 - 53/37 

3** 1.5 3 off 0 4.179 3.5 1.194 day/night 4 800 - 53/37 

4 3.5 7.25 on 2 4.289 3.5 1.225 continuous 3 1000 - 53/37 

5 3.5 7.25 on 2 7.282 3.5 2.081 day/night 4 1000 - 53/37 

6 3.5 7.25 on 2 7.282 3.5 2.081 day/night 4 800 - 53/37 

met 

profile 8 6 off 0 8.724 3.5 2.493 day/night 50 

hrs 1000 Node3 53/37 

met 

profile 10 7.25 on 2 7.282 3.5 2.081 day/night 50 hrs 

Node 

3 1000 53/37 

met 11 profile 7.25 on 2 7.282 3.5 2.081 day/night 48 

hrs 1000 Lab 53/37 

*includes air leakage compensation of 0.24 lb/day air 

** tests repeated after air leakage detected 

42
2.2.3 Discussion of Test Results 

2.2.3.1 Description of Result Metrics for Fully Integrated Tests 

Table 2.2-2 lists the parameters used to evaluate the performance of the subsystems during the integration 

tests. The parameters are listed as Set points or Performance. Set points are input parameters that are 

established for each test case. They are the input variables to which the systems respond. Parameters are the 

responses of the subsystems. The input parameters include the items discussed in Section 2.2.3.2 as well as 

some additional items not included on the previous tables. Some of the additional parameters were not 

changed between test points, but would have to be considered in the development of an Air Revitalization 

System for other exploration mission scenarios. 

Summary plots of each Test Point are assembled in Appendix A. 

Table 2.2-9 – Integration Test Metrics 

Integration Test Parameters 

Set point Performance 

Overall System Test 

Test Duration Frequency of Vacuum Vent 

Day/Night or Continuous Sabatier Starvation 

Crew Size 

4BMS 

CO2 Inlet Concentration or Feed Rate CO2 Removal Efficiency 

Half Cycle Duration Power 

Mechanical Compressor 

Compressor Speed Power 

Accumulator Working Pressure Range Number of Start/Stop Cycles 

Accumulator Volume Duty Cycle 

Sabatier 

Hydrogen Feed Rate (based on crew size) Water Recovery Efficiency 

Molar Ratio Actual Water Production 

Day/Night Cycle Times Power 

Theoretical Water Production (based on 

H2 available) 

Reactor Temperatures 

Reactor Pressure Drop 

43
The significance of the Set points and Performance parameters are discussed in detail below: 

Overall System Test 

• Test Duration – the duration of each test was pre-established to attempt to reach steady state 

operation within the 4BMS. The tests with constant CO2 concentration fed to the 4BMS were run 

for three or four half cycles. The tests that incorporated a metabolic profile to simulate the 

movement of crew within the habitat were run for 50 hours or more to include repetition of the 

profile. 

• Day/Night or Continuous – Day/night vs. continuous operation affects the availability of power. It 

is assumed that when the ISS is in the night portion of the orbit that power consuming devices 

must be tuned down or off. This affects the Sabatier operation and the heater power allowed in the 

4BMS. 

• Crew Size – crew size is used as an indicator of overall load on the systems. Crew consumption of 

oxygen (reflected in hydrogen flow rate) and crew production of carbon dioxide drive the sizing 

requirements for the subsystems. 

• Frequency of Vacuum Vent – the vacuum vent is controlled at the system level based on what is 

going on with the 4BMS. Excessive venting is an indication of poor CO2 management and likely 

is associated with Sabatier starvation. 

• Sabatier Starvation – the overall goal of the system integration is to recover as much water as 

possible. Sabatier starvation means that there is hydrogen produced ready to be converted, but 

there is not enough carbon dioxide available to run the reaction. The overall mass balance of 

hydrogen and carbon dioxide is such that there is always excess CO2 available, so starvation is 

another indicator of poor CO2 management. 

4BMS 

• Inlet CO2 concentration or feed rate – The feed rate of CO2 to the 4BMS falls out of the crew size 

parameter and sets the operating envelope for the integrated systems. 

• Half Cycle Duration – A half cycle refers to the length of time that all beds of the 4BMS system 

are in either adsorb or desorb. The length of the half cycle affects how well the molecular sieve 

beds adsorb and desorb CO2. The integration tests were all performed with a 144 minute half 

44
cycle, however some of the stand alone tests were done with 155 minute half cycles to compare to 

the manufacturer’s baseline tests. Shorter half cycle times increase the CO2 removal performance. 

• CO2 Removal Efficiency – CO2 removal efficiency is a measure of the amount of CO2 actually 

captured by the 4BMS compared to the amount fed to it. Most of the tests were done open loop, 

which means that the scrubbed air from the 4BMS was not returned to the inlet. Because the 

testing was open loop, there was no buildup of CO2 concentration that would otherwise be seen 

with a poor performing 4BMS. CO2 removal efficiency is affected by the desorption pressure, a 

significant artifact of integration with a compressor instead of space vacuum venting. 

• Power – The 4BMS heaters consume power to desorb CO2 and water from the zeolite. The power 

requirement is a function of the CO2 loading isotherms. The lower the vacuum pressure available 

for desorption, the lower the power requirement to drive off the CO2. 

Mechanical Compressor 

• Compressor Speed – In this series of testing, the compressor speed was varied to effectively 

change the flow rate capacity of the compressor. In reality, the piston size and stroke would be 

optimized to achieve the desired volumetric flow rate. The speed change allowed an easy way to 

change flow conditions and observe the results. 

• Accumulator Working Pressure Range – The accumulator used in the mechanical compressor tests 

was restricted to operation between 18 and 120 psia. There are several factors that influence this 

range that could change for other than and ISS application. The low set point pressure is based on 

the pressure drop allocation for the control components in the Sabatier at maximum flow rate. This 

pressure drop is added to the reactor inlet pressure and the minimum pressure of 18 psia is 

achieved. The actual pressure drop of the EDU hardware was lower than the allocation because 

there were no filters installed in the lines. The upper pressure limit is based on pressure ratio 

achievable by the compressor, inlet dew point and the resulting dew point of the gas once 

compressed, and the pressure rating of the downstream components. The accumulator vessel can 

withstand over 2000 psia, however, not all of the shutoff valves can be exposed to that pressure. 

The maximum operating pressure selected for these tests was 120 psia, which was sufficiently low 

enough to prevent condensation. 

45
• Accumulator Volume – The accumulator volume for the ISS application is 0.73 ft3. This is the 

largest volume of accumulator bottles ganged together that could fit in the Space Station rack 

designated for Sabatier installation. All of the integration tests using an accumulator used similar 

size bottles to simulate the ISS available volume. 

• Power – Power is one of the key performance variables of the mechanical compressor. The power 

consumption is based on the work done to compress the carbon dioxide and also the mechanical 

and electrical efficiency of the compressor and motor. 

• Number of Start/Stop Cycles – The number of start/stop cycles resulting from the integration 

dynamics is an important factor in the life of the compressor. The number of start/stops affects 

wear of moving parts and life of electronic components. 

• Duty Cycle – Duty cycle is the most important factor affecting life of the compressor. The life 

limiting component of the compressor is the piston rings, and their life is directly attributed to run 

time. 

Sabatier 

• Hydrogen Feed Rate – The hydrogen feed in these tests was delivered from gas cylinders. In a real 

ARS application, the hydrogen would come from an oxygen generator and would be a function of 

the oxygen produced for crew consumption. The hydrogen feed rate can be any value for other 

mission scenarios. 

• Molar Ratio – Molar ratio is the ratio of hydrogen to carbon dioxide fed to the Sabatier reactor. 

The stoichimetric ratio is 4 moles hydrogen to 1 mole CO2. In these tests, the molar ratio was set 

to 3.5. In the space station application, CO2 is in excess of hydrogen. The reactor works more 

efficiently when the molar ratio is not at the stoichiometric value. In other applications, Mars for 

example, the reactor might be run at molar ratios greater than 4. 

• Day/Night Cycle Times – The day night cycle time for most of the tests was set to 52 minutes day, 

37 minutes night. This corresponds to the longest night duration of the ISS orbit. The length of the 

night cycle affects how much the reactor cools off before being restarted. 

46
• Theoretical Water Production – This value is the amount of water that could be generated by the 

Sabatier if every mole of hydrogen was consumed, and all of the water was collected. The molar 

ratio of water generated to hydrogen consumed is 1:2. 

• Actual Water Production – This is actual mass of water collected over each test duration. The 

water production is affected by the reactor efficiency, the separator waste heat and the number of 

shutdown cycles for night time operation. 

• Water Recovery Efficiency –This is the ratio of actual water to theoretical water. It is the most 

telling of the Sabatier performance metrics for overall system performance. 

• Power – Power is consumed by the Sabatier to preheat the reactor and to operate the separator, in 

addition to valves and sensors. 

• Reactor Temperatures – The reactor temperatures indicate the general health of the Sabatier 

reaction and vary with different inlet feed rates and molar ratios. 

• Reactor Pressure Drop – Reactor pressure drop varies with feed flow rate, unless there is 

excessive water condensation in the reactor bed. A high value would indicate a 

performance issue that would require adjustment. 

2.2.3.2 4BMS Baseline Test 

The table below lists the results of 4-BMS stand alone testing that was performed after the integrated tests 

were completed. 

Test Case # ppCO2 Inlet CO2 Removal 

Rate 

In – Out 

CO2 

Removal 

Efficiency 

torr 

Lb/hr 

4BMS Baseline 3.79 0.52 74% 

4BMS Baseline TP2 

Conditions 

1.48 0.23 84% 

4BMS Baseline TP4 

Conditions 

3.39 0.52 81.5% 

4BMS Baseline TP5 

Condition 

3.40 0.52 81.8% 

47
2.2.3.3 Mechanical Compressor Baseline Test 

The mechanical compressor was tested in a stand-alone configuration to compare its 

performance against the baseline data recorded by the manufacturer. The compressor was 

tested at 4 psia inlet pressure, 130 psia outlet pressure and produced about 2 lb/hr. The 

compressor was also tested at 4 psia inlet pressure and 20 psia outlet pressure. The flow 

rate varied between the three runs, with approximate averages of 1.2, 1.4, and 2 lbs/hr. 

Large variations in inlet pressure were observed. 

Test 

Point 

Suction 

Pressure 

Discharge 

Pressure 

Pump 

Speed 

Flow 

Achieved 

(psia) (psia) (RPM) 

1 4 20 1000 1.2-2 lb/hr 

2 4 130 1000 2 lb/hr 

Each test point will last a minimum of 5 minutes. 

2.2.3.4 4BMS + Mechanical Compressor 

The purpose of these integrated tests was to measure the dew point of the product CO2 to 

determine if there would be condensation in either the compressor or the accumulator 

during operation. The 4BMS was operated with constant 0.2% CO2 inlet concentration. 

The compressor operated with the varying inlet pressure as produced by the 4BMS and 

with fixed outlet pressures set by a back pressure regulator. The outlet pressures were set 

to 20, 47.5, 75, 102.5, and 130 psia. Dew point of the compressed CO2 remained below 

31 F for all conditions tested. During extended compressor operation, the dew point 

remained around 0 F. CO2 removal from the 4BMS using the mechanical compressor 

was the same as using the space vacuum simulator within the measurement accuracy of 

the tests. 

Test Case # ppCO2 Inlet CO2 Removal 

Rate 

In – Out 

CO2 

Removal 

Efficiency 

torr 

Lb/hr 

4BMS CEDU 1.48 0.24 87% 

4BMS CEDU 3.37 0.54 85% 

4BMS CEDU 3.38 0.58 92% 

4BMS Stand Alone 1.48 0.23 84% 

4BMS Stand Alone 3.39 0.52 81.5% 

4BMS Stand Alone 3.40 0.52 81.8% 

Dew Point Data 

Test Day Compressor outlet 

pressure 

Max Dew Point 

Day 7 20 31 F 

48
Day 8 50, 75, 100 30, 29, 27 

Day 9 130 31 

2.2.3.5 Mechanical Compressor Startup Under Vacuum 

One of the safety checks envisioned for the Sabatier CRA system required vacuum 

venting of the entire Sabatier system including the mechanical compressor and 

accumulator. The mechanical compressor was tested by starting it with vacuum at both 

the inlet and outlet to determine if there were any performance issues. Three successive 

tests were conducted with no problems encountered. No unusual noises or other unusual 

behavior were observed. 

2.2.3.6 4BMS + Mechanical Compressor + Accumulator + Sabatier 

This section describes the test results for the 4BMS, Mechanical 

Compressor/Accumulator and Sabatier integration test series. Eleven different test points 

were run, each with a different set of operating conditions. The summary of test results is 

given below in Table 2.2-3. 

Test points 1,2 and 3 were conducted at the minimum crew loading of 3 Equivalent 

Persons, with all of the CO2 removal performed by the 4BMS (no Vozdukh simulation). 

Test Point 1 was continuous operation, or no day/night cycling. This means the Sabatier 

and the 4BMS heaters were allowed to operate all of the time. Test Points 2 and 3 used a 

53 minute day/37 minute night cycle. Test Point 3 was run with the slower compressor 

speed (800 rpm) compared to 1 and 2 with the 1000 rpm speed. Test Points 4,5 and 6 

mimicked 1,2, and 3 except they were run at the maximum crew loading of 7.25 

Equivalent Persons with simulation of 2 EP of CO2 removal and H2 production by 

Russian hardware. Test Points 8, 10 and 11 were run with metabolic profile inputs for the 

CO2 feed to the 4BMS. Test Point 8 was 6EP with no Russian hardware, 10 and 11 were 

7.25 EP with 2 EP of Russian hardware. Test Points 8 and 10 were simulated with the 

ARS components installed in the Node 3 location of the ISS. Test Point 11 was simulated 

with the components in the Laboratory Module of ISS. 

Table 2.2-10 – Mechanical Compressor CO2 Capture Performance Data 

Test Point CO2 EP Time Period Evaluated (hrs) Number of 4BMS Half Cycles Number of Sabatier Day/Night Cycles Number of Compressor ON/Off Cycles Compressor Cycles per Half Cycle Total Compressor Run Time (min) Average Compressor Run Tim per Half Cycle (min) Compressor Duty cycle (%) Total Sabatier Starvation Time (min) 

1 3 16.10 6.75 - 21 3.11 168 25 17 15 

2 3 3.78 1.5 2.75 5 3.33 42 28 19 9 

49
3 3 22.50 9 15 25 2.78 324 36 25 9 

4 5.4 7.80 3.25 - 11 3.38 67 21 15 0 

5 5.4 14.43 6 9.75 23 3.83 136 23 16 0 

6 5.4 27.35 11.5 18 42 3.65 251 22 15 0 

8 6 (met) 40.78 17 27.5 68 4.00 399 23 16 0 

10 5.4 (met) 28.78 12 19 50 4.17 235 20 14 0 

11 5.4 (met) 43.20 18 28.5 80 4.44 355 20 14 0 Total Number of 4BMS Vent Cycles Accumulator Average Minimum Pressure (psia) Accumulator Average Maximum ( i ) Test Point CO2 EP Average 4BMS Vent Cycles per Half Cycle 

1 3 0 0 20 60 

2 3 0 0 20 40 

3 3 0 0 20 55 

4 5.4 6 1.85 50 130 

5 5.4 7 1.17 50 130 

6 5.4 13 1.13 60 130 

8 6 (met) 11 0.65 50 130 

10 5.4 (met) 9 0.75 60 130 

11 5.4 (met) 23 1.28 55 130 

The number of compressor cycles and compressor duty did not vary greatly from 

between test conditions. The greatest difference noted is at the lower CO2 loading, there 

is a marked difference between the low and high speed compressor tests. As expected, the 

lower speed had a higher duty cycle. This difference is not seen in the higher CO2 

loading cases. The compressor rules are less demanding on the compressor when the 

accumulator is near its full mark, and therefore the compressor operation is nearly the 

same for both cases. Some of the test periods evaluated were quite short and therefore 

there is significant round off error associated with the results. 

The minimum EP cases (1, 2 and 3) experienced periods of Sabatier starvation when H2 was being 

produced by the OGA but there was not enough CO2 in the accumulator for processing. The accumulator 

pressure dropped to the minimum operating pressure of 20 psia and only reached to a maximum pressure of 

60 psia. There were no vent cycles, which indicates that no CO2 was wasted. At these low rates, the impact 

of leakage is more significant, and it may not be possible to avoid starvation. 

The higher EP cases (test points 4, 5 and 6) did not experience any starvation. There were numerous vent 

cycles and overall high accumulator pressures. The overall water production efficiency was generally 

higher, since all of the hydrogen was processed. 

The compressor duty cycle for all cases was on the order of 13-21% with the higher CO2 loading cases 

having the lower duty cycle. There was not a large difference in duty cycle between the cases with the 

different compressor speeds (Test points 2 vs. 3 and 5 vs. 6). 

50
Figure 2.2-26 below is a typical example of performance data collected during the mechanical compressor 

integration tests. The performance data described above is shown in this plot of one CDRA half cycle. The 

top purple line is the accumulator pressure. In this test case, the accumulator is regularly near the upper 

limit of 130 psia. When the accumulator pressure is at this maximum value, the compressor rules do not 

allow the compressor to turn on to pump CO2 from the CDRA. In time, the CDRA bed pressure, indicated 

by the pink line, reaches the maximum allowable pressure of 8 psia and the vacuum vent valve is opened. 

The vent valve opening is noted by the sharp increase in pressure of the vacuum tank indicated by the dark 

blue line. The aqua line indicates when the Sabatier is in Process mode, and the green line indicates when 

the compressor is activated. For this test case, the compressor activates between 3 and 4 times per CDRA 

half cycle. 

0

2

4

6

8

10

12

14

4:13 4:27 4:42 4:56 5:11 5:25 5:39 5:54 6:08 6:23

Time

Data

0

20

40

60

80

100

120

140

Accumulator Pressure

Vacuum Tank Pressure

Compressor Activation

Sabatier Process Mode

CDRA Discharge Pressure

Pressure relief by 

vacuum vent valve, 

accumulator is full 

Compressor 

Operation

Compressor runs until 

max accumulator 

pressure is met

Sabatier operation 

uses CO2 from 

accumulator, then 

compressor refills

Test Point 6, 5.4 EP, Day/Night, 800 RPM

Sabatier 

Process 

Mode

Figure 2.2-26 – Typical Performance Data for Mechanical Compressor Integration Tests 

The following four plots show the characteristic water recovery data for some of the test points. In Test 

Point 4, the overall water recovery was 95%. This test point was at continuous operation at the higher CO2 

51
loading. There was no starvation of the Sabatier during this test point. This is the highest water recovery 

expected from the Sabatier system at these operating conditions. In contrast, Test Point 1, which was 

continuous at the lower CO2 loading, showed signs of Sabatier starvation and yielded only 89% water 

recovery. The offset of the blue line with the two small steps from the straight gray line is the loss of water 

due to insufficient CO2 available to the Sabatier. The water recovery of the Sabatier based on its operating 

time is 91%, the two percent difference is due to starvation. 

Test Point 6 is a cyclic day/night case. The water recovery suffers more in this mode due to the cyclic 

operation. Each time the Sabatier transitions to and from Standby, the system is evacuated and steam is lost 

to the vacuum vent. The reactor also is not at the optimal temperature due to the constant change of flow 

rate. The efficiency drops from the high of 94% in Test Point 4 down to 89% in Test Point 6 due to cyclic 

operation. Further, the recovery worsens in Test Point 3, which is cyclic at the lower CO2 loading. 

Starvation occurs in this scenario dropping the water recovery to 82% overall. 

The three metabolic load cases (Test Points 8, 10 and 11) did not experience any Sabatier starvation. Their 

water recovery numbers are slightly lower than the equivalent fixed CO2 feed cyclic case (Test Point 6). 

0

100

200

300

400

500

600

700

800

900

1000

45.9 45.95 46 46.05 46.1 46.15 46.2 46.25 46.3

Time

Water (g)

Theoretical Water 

Production

Actual Water 

Collected

Theoretical water 

production based 

on H2 delivered to 

Sabatier

Actual water 

periodically 

discharged from 

phase separator

Water recovery 

efficiency is 89%

Test Point 6, 5.4 EP, Day/Night, 800 RPM

0

100

200

300

400

500

600

700

800

900

1000

45.9 45.95 46 46.05 46.1 46.15 46.2 46.25 46.3

Time

Water (g)

Theoretical Water 

Production

Actual Water 

Collected

Theoretical water 

production based 

on H2 delivered to 

Sabatier

Actual water 

periodically 

discharged from 

phase separator

Water recovery 

efficiency is 89%

Test Point 6, 5.4 EP, Day/Night, 800 RPM

52
0

200

400

600

800

1000

1200

41.75 41.8 41.85 41.9 41.95 42 42.05 42.1 42.15 42.2

Time

Water (g)

Theoretical Water 

Production

Actual Water 

Collected

Test Point 4, 5.4 EP, Continuous, 1000 RPM

Water recovery 

efficiency is 94%

53
Table 2.2-11 - Sabatier Water Production Rate Efficiencies 

Actual Water 

Collected (gm) 

Theoretical Water 

Production Rate 

Actual Water 

Time Period Production Rate 

Evaluated (hrs) 

Water Production 

Test Point CO2 EP (gm/min) (gm/min) Efficiency 

1 3 16.10 876.3 0.99 0.85 89% 

2 3 3.78 197.1 0.99 0.85 84% 

3 3 10.85 574.6 0.99 0.81 82% 

4 5.4 5.97 576.0 1.72 1.6 94% 

5 5.4 6.65 637.7 1.72 1.6 93% 

6 5.4 15.05 1341.8 1.72 1.5 89% 

8 6 (met) 14.90 1590.3 2.06 1.8 88% 

10 5.4 (met) 19.97 1836.6 1.72 1.4 87% 

11 5.4 (met) 19.98 1713.9 1.72 1.5 86% 

The water production performance is presented in Table 2.2-4. As expected, the steady 

state cases (Test Points 1 and 4) had the highest water recovery rates as there was no 

water vapor lost due to venting during Standby operation. The higher EP cases had 

slightly higher water recovery as there were no periods of Sabatier starvation. 

54
2.2.4 Conclusions from This Test Section 

The integration test of the 4-Bed Molecular Sieve, Mechanical Compressor and 

Accumulator and Sabatier was a successful test program. The testing showed that these 

systems could be properly integrated together. There is no significant, detrimental impact 

on the 4-Bed CO2 removal system when desorbed with a compressor instead of space 

vacuum. 4-BMS CO2 removal efficiency was well above requirements for the wide range 

of CO2 inlet concentrations tested. The compressor control logic in place during this test 

program supported the wide range of conditions tested. Modifications were made in the 

flight CO2 compressor control logic to accommodate pressure sensor accuracy 

requirements. Also, the 4-BMS vent valve flight control strategy is different than what 

was tested and results in fewer valve cycles. 

As a result of this testing, the compressor simulation model was modified to better 

predict flow at low suction pressures. The 4-BMS model was also updated to incorporate 

a leakage factor to estimate air leakage into the system components that operate at 

vacuum. 

2.3 Integration Test Using the TSA Compressor 

2.3.1 Description of Tests 

2.3.1.1 4BMS + TSAC 

The TSAC integration tests were conducted in three phases at MSFC. The first phase 

included the integration test of the 4BMS and TSAC only with constant 4BMS CO2 

loading. Phases 2 and 3 included the Sabatier with constant and variable CO2 loading of 

the 4BMS. The primary objective of the first phase was to demonstrate the TSAC 

performance in a realistic environment where the CO2 flow and pressure from the 4BMS 

varied with time. The objectives of these tests were to gather data for the validation and 

optimization of the air-cooled TSAC design, and for development of a low power CO2 

removal system that incorporates the functions of the 4BMS and the TSAC. 

Figure 1 below shows a simplified schematic of the 4BMS and the TSAC configured for 

the initial phase of the stand alone tests. The Sabatier simulator was a mass flow 

controller set to draw a fixed flow rate of CO2 from the TSAC. 

55
Figure 27 - Simplified Schematic of 4BMS and TSAC Integration Test 

56
2.3.1.2 4BMS + TSAC + Sabatier 

Simplified Schematic of Ground Test Hardware

V209

V2

Vent Line

CDRA

To Vacuum

V209 Air Save V200

LMS

Space Vacuum

Simulator

V2

Facility

Vent

Sab

EDU

N2

Vacuum 

vent

PG

Venturi

Vac

Vent

H2

Bottle/

regulator

H2

Bottle/

regulator

CO2 inlet

TSAC

CDRA

To Vacuum

V209 Air Save V200

LMS

Space Vacuum

Simulator

V2

Facility

Vent

Sab

EDU

N2

Vacuum 

vent

PGPG

Venturi

Vac

Vent

H2

Bottle/

regulator

H2

Bottle/

regulator

CO2 inlet

TSAC

V209

V2

Vent Line

CDRA

To Vacuum

V209 Air Save V200

LMS

Space Vacuum

Simulator

V2

Facility

Vent

Sab

EDU

N2

Vacuum 

vent

PG

Venturi

Vac

Vent

H2

Bottle/

regulator

H2

Bottle/

regulator

CO2 inlet

TSAC

CDRA

To Vacuum

V209 Air Save V200

LMS

Space Vacuum

Simulator

V2

Facility

Vent

Sab

EDU

H2

Bottle/

regulator

N2

Vacuum 

vent

H2

Bottle/

regulator

CO2 inlet

PGPG

Venturi

Vac

Vent

TSAC

Figure 28 – Integrated Test Schematic – 4BMS, TSAC, Sabatier 

Figure 2 above is a simplified schematic of the 4BMS integrated with the TSAC and the 

Sabatier. The same V209 and V2 valves were used as with the mechanical compressor 

test. The two beds of the TSAC and the associated valves that allow switching are not 

shown in this diagram. These are all contained in the box labeled TSAC. The V209 valve 

again is used to allow the desorbing 4BMS bed to first perform the air-save function 

(removing ullage air volume back to the cabin). This valve then switched to the vent 

direction (to compressor or vacuum) once air-save was completed. The V2 valve, again 

was used to pressure relieve the 4BMS beds if the desorbing CO2 pressure was too high. 

The logic for this valve operation is described in Section 2.1 (Hardware Description). 

The integrated hardware shown above in Figure 2 operated as follows: 

• During bed desorption, the 4BMS (labeled CDRA in the figure) delivers CO2 

through valve V209. 

• Excess CO2 is vented through valve V2 to the space vacuum simulator. The 

venting logic is described in more detail in Section 2.1.5.2, 4BMS Venting. 

• CO2 for processing is delivered through valve V3 to the suction of the TSAC. 

The TSAC controlled all of the valves necessary to switch between the two 

sorbent beds and isolate the TSAC from the 4BMS and Sabatier. The Sabatier 

controller did not perform this function. 

• A separate vent line from the TSAC to the space vacuum simulator was used to 

allow the TSAC beds to bleed diluent gases (nitrogen and oxygen) from the beds. 

57
Without the bleed stream, these diluents would build up and the compression 

capacity would diminish. 

• The compressor delivered CO2 to the Sabatier inlet. The TSAC sorbent beds act 

as both accumulator and compressor. A separate accumulator is not needed with 

this compressor configuration. 

• Valve SVC007, inside the Sabatier (not shown), opened to allow CO2 to flow 

when the Sabatier was in its processing state. 

As with the mechanical compressor integration, during the TSAC integration the 4BMS 

was operated in the nominal ISS CDRA mode. Half-cycle time was 144 minutes and 

process air flow rate was 95 lbs/hour average. For the last 10 minutes of the desorb 

cycle, the desorbing bed was exposed directly to the space vacuum simulator pump. The 

CO2 loading profiles for the different test points are described in detail in Section 2.0. 

2.3.1.3 Test Conditions 

Table 5 below details the test conditions used for the integration of the TSA compressor 

with the 4BMS with and without the Sabatier. The column data in the table is as follows: 

• Column 1 is a description of the conditions being simulated. 

• Column 2 is the test point number for recording test parameters and resulting data. 

• Column 3 is the target CO2 loading on the 4BMS for the TSAC/4BMS parametric 

tests without the Sabatier. 

• Column 4 is the target CO2 inlet concentration to the 4BMS for fully integrated 

tests with the Sabatier. These tests were run open loop, therefore the feed 

concentration to the 4BMS was set by a CO2 mass flow controller with measured 

CO2 concentration feedback to the mass flow control set point. 

• Column 5 is the number of equivalent persons in the crew. The test points used 

for comparison of the two compressors were set with the same number of crew. 

For the test points that simulated a Lunar Base, the crew was set to 4. The 

compressor parametric tests used various crew sizes to achieve the desired 

loading values. 

• Column 6 is the TSAC loading or suction pressure. This value is controlled in 

each test. 

• Column 7 is the TSAC production or discharge pressure. The pressure was set at 

19.3 psia for the 4BMS/TSAC only tests. The pressure was set at 18 psia for the 

4BMS/TSAC?Sabatier tests. 

• Column 8 is the US H2 feed rate. This designation was carried over from the ISS 

simulation tests even though there currently is no concept of multiple life support 

hardware components for Lunar operations. The H2 feed rate is calculated from 

the crew O2 consumption with an allotment of 0.24 lb/day of air leakage. 

• Column 9 is the H2/CO2 molar ratio. While this value is a variable in the Sabatier 

control logic, it was set to a constant value of 3.5 for all tests. 

58
• Column 10 is the feed rate of CO2 from the compressor to the Sabatier. This 

value is calculated by the Sabatier controller from the indicated hydrogen flow 

rate and the desired molar ratio. 

The following describes the different test points and objectives: 

• Test Points 1 through 5 were performed with the 4BMS and TSAC only, without 

the Sabatier 

• Test Point 1 was a maximum loading test with 8 kg/day loading on the 4-BMS 

and TSAC loading at 4 psia. The TSAC production rate was 4.2 kg/day. 

• Test Point 2 was to determine the maximum TSAC production capacity at 5 

kg/day 4-BMS loading. 

• Test Point 3 was to determine the maximum TSAC production capacity at 4 

kg/day 4-BMS loading . 

• Test Point 4 was to determine the maximum TSAC production capacity with the 

4-BMS loaded to 4 kg/day, but the 4-BMS was not desorbed to vacuum at the end 

of the half cycle. This test would provide data pertinent to LPCOR development. 

• Test Point 5 was to determine the maximum TSAC production capacity at 3 

kg/day 4-BMS loading. 

• Test Point 6 was a parametric test with the TSAC loading pressure intended to be 

6 psia. 

• Test Points 7 through 11 were integrated tests including the Sabatier. 

• Test point 7 was a baseline configuration that mimicked conditions of a 

previously run 4BMS/TSAC only test. The purpose of this test was to verify that 

the integration of the Sabatier did not impact the performance of the TSAC and 

4BMS. 

• Test points 8 and 9 were designed to mimic previous integration tests with the 

4BMS/Mechanical Compressor and Sabatier. The purpose of these tests was to 

obtain direct comparisons of the compressor technologies as they relate to the 

integration requirements. 

• With the current focus on the Vision for Space Exploration, the team decided to 

develop test conditions that would reflect possible future exploration mission 

scenarios. These missions simulate a manned outpost at the Lunar south pole. Test 

Point 10 simulated the extended Lunar night and Test Point 11 simulated EVA 

activities. The basis for these test points is described in more detail in the next 

section. 

In all of these tests, the objectives also included measurement of the effects of integration 

on the efficiencies of the stand-alone components. 

59
Table 12 - Integrated Test Matrix – TSAC Test 

US H2 Feed Rate 

slpm (lb/hr) 

TSAC Production 

Pressure kPa 

(psia) 

4BMS Inlet CO2 

Conc. 

Sabatier CO2 

Feed Rate slpm 

(lb/hr) 

TSAC Loading 

Pressure kPa 

(psia) 

H2/CO2 Molar 

Ratio 

Test Point # 

4BMS CO2 

Equiv. Pers. 

Loading 

kg/day 

(lb/day) 

MmHg 

(%) 

EP 

Test Point Description 

Integrated 4BMS/TSAC 

baseline test 

133 

1 8 (17.6) -- 8 27.6 (4) (19.3) -- -- -- 

Integrated 4BMS/TSAC at 

reduced CO2 loading, 5 

kg/day 

133 

2 5 (11) -- 5 27.6 (4) (19.3) -- -- -- 

Integrated 4BMS/TSAC at 

reduced CO2 loading, 4 

kg/day 

2.3.1.4 Mission scenario development 

This section describes the operating conditions set for each series of integration tests. 

Section 0 explains the reasons for choosing the test point in the matrices and how each 

series of tests relates to future missions. Section 2.3.1.3 details the input parameters in 

terms of crew size, processing duration, etc. 

Specific, quantitative test conditions, like any requirement, must be traceable back to 

some realistic higher level requirement, which in turn is traceable to a mission scenario. 

Rather than starting “at the bottom” with candidate test points the test point definitions 

3 4 (8.8) -- 4 TBD 

133 

(19.3) -- -- -- 

Integrated 4BMS/TSAC at 

reduced CO2 loading and no 

vacuum desorb ot 4BMS 

133 

4 4 (8.8) -- 4 TBD (19.3) -- -- -- 

Integrated 4BMS/TSAC at 

reduced CO2 loading, 3 

kg/day 5 3 (6.6) -- 3 TBD 

133 

(19.3) -- -- -- 

Integrated 4BMS/TSAC at 

reduced CO2 loading 

pressure 

133 

6 5 (11) -- 5 41.4 (6) (19.3) -- -- -- 

Integrated 4BMS/ TSAC/ 

Sabatier at TSAC baseline 

conditions for TSAC health 

check 7 -- 

5.3 

(0.7%) 

124 

(18) 

6.766 

(0.0798) 

1.933 

8.3 -- 3.5 (0.502) 

Integrated 4BMS/ TSAC/ 

Sabatier for comparison to 

mechanical compressor test 

point #2 

3.5 

(0.46%) 

124 

(18) 

4.459 

8 -- 5.46 -- (0.053) 3.5 

1.274 

(0.331) 

Integrated 4BMS/ TSAC/ 

Sabatier for comparison to 

mechanical compressor test 

point #3 

1.5 

(0.2%) 

124 

(18) 

1.925 

9 -- 2.34 -- (0.023) 3.5 

0.550 

(0.143) 

Integrated 4BMS/ TSAC/ 

Sabatier Lunar night scenario, 

non-optimal TSAC shutdown/ 

startup 10 -- 

2.52 

(0.33%) 

124 

(18) 

3.273 

4 -- (0.037) 3.5 

0.935 

(0.243) 

Integrated 4BMS/ TSAC/ 

Sabatier EVA full crew 

departure scenario, CO2 

regenerated to cabin 

Per 

profile 

124 

(18) 

3.273 

11 -- 4 -- (0.039) 3.5 

0.935 

(0.243) 

60
can be derived “top down” from the mission scenarios. This process ultimately links the 

tests and the data produced to the mission need. 

Because of the configuration of the Sabatier scar in the OGS rack, the TSAC compressor 

is a less likely candidate for the ISS application, however its technical merits make it a 

viable candidate for other space exploration missions where interface conditions have not 

already been set. The TSAC test conditions were based on possible Lunar mission 

operating parameters. Various scenarios were explored that taxed the systems’ 

capabilities over a range of conditions. These Lunar mission scenarios were used to 

develop the input parameters of Table 5. 

 

Lunar Base CRA Installation 

With the current focus on the VSE, it was decided that test points should be included to 

reflect possible future mission scenarios. Three basic mission scenarios were developed: 

1) Impact of lunar day/night cycles at the south pole, 2) Lunar mission EVA, and 3) 

Reduced pressure cabin atmosphere. For this test series, the third mission scenario was 

ruled out since time constraints would not allow the reconfiguration of test hardware for 

sub-ambient operation. 

Impact of Lunar Day/Night Cycles at the South Pole 

Lunar missions will operate with very different power cycle availability than the more 

familiar ISS power-cycle profile. Due to a reduction in resupply water capability, the use 

of a CDRA/TSAC/Sabatier system is most advantageous as part of an Outpost life 

support system, which will most likely be positioned at the Lunar South Pole. At the 

South Pole, solar power is available nearly continuously for most of the month, with 

periods of 24 to 48 hrs where no solar power is available and stored battery power is 

required. Reduced power operations will probably be necessary during this night period. 

Since OGA provides hydrogen to Sabatier, one test point included shutting down the 

Sabatier production during what would be the Lunar night. With the Sabatier shut down 

during Lunar night, TSAC need not operate to produce CO2. Depending on the TSAC 

state when the system shuts down, the start-up could be simple or more complex. The 

CDRA would continue operating to maintain CO2 levels in the habitat. 

Due to time constraints, the most challenging scenario was selected where the lunar night 

cycle begins relatively early in a CDRA half cycle and ends towards the end of a CDRA 

half cycle. This results in the TSAC shutting down when only a fraction of the adsorbing 

bed has been loaded and only a fraction of the desorbing/producing bed has been 

unloaded. Hence, when the lunar night is over and the TSAC/Sabatier re-started, for the 

first TSAC cycle after the half cycle change, there is too much CO2 on the adsorbing 

TSAC bed for the CDRA to fully desorb. 

Preliminary testing found that by approximately 70-80 min into the 4BMS 144 min cycle, 

about 25% of the available CO2 was adsorbed onto TSAC. Hence for this test point, 

Lunar night or TSAC/Sabatier shutdown occurred at this time. Due to time constraints, 

the Lunar night cycle was reduced to a minimum of 6 hrs, about the time it takes to fully 

cool down the TSAC and Sabatier systems. After the lunar night cycle, the TSAC and 

61
Sabatier were started back up at roughly 120 min into the current 4BMS cycle. Since 

there is almost no CO2 remaining on the 4BMS desorbing bed at this time, the TSAC 

was not able to adsorb any additional CO2. Since the TSAC requires roughly 20 min to 

heat up before it can provide CO2 to the Sabatier, the desorbing TSAC bed at first was 

not able to unload any additional CO2 to Sabatier. Hence, when the CDRA half cycle 

change occurred, the TSAC was essentially in a worst-case configuration with both beds 

partially loaded with CO2. The results of this test configuration will be discussed below. 

Lunar Mission EVA 

Lunar Exploration missions will be highly EVA intensive, with crews of two to four 

making trips on the lunar surface multiple times in a week. The number of crewmembers 

actually in the habitat can change significantly during the day or the week, changing the 

load on each of the air systems. It was assumed that if an OGA were used for oxygen 

generation, it would also be used to generate oxygen that is stored for consumption 

during EVAs resulting in continuous H2 availability. It was also assumed that the CDRA 

would remain operational even if all crew were on EVA since this is the most likely flight 

configuration due to its simplicity. 

Multiple possible EVA scenarios were evaluated. These included: 1) 4 crew EVA where 

CO2 exhausted on EVA is stored and later regenerated back to the cabin, 2) 4 crew on 

EVA but CO2 is vented during EVA, 3) 4 crew on EVA but depart habitat in groups of 

two offset by 4 hrs, and 4) 2 crew on EVA and 2 remain in habitat. METOX 

regeneration was used as a model for the regenerable EVA CO2 removal technology. 

Overall, approximately ten different possible EVA scenarios were developed. Several of 

the configurations were modeled in JSC’s integrated model discussed previously. In 

comparing the predicted cabin ppCO2 profiles, it was concluded that the most dynamic 

and therefore worst case test scenario was defined as a 4 crew, single departure EVA 

where CO2 is stored and later regenerated to the cabin. Based on modeling, the most 

realistic EVA CO2 regeneration scenario involved 2 crew worth of CO2 being 

regenerated starting 2 hours post EVA followed by the remaining 2 crew’s worth of CO2 

regenerated the following day. Figure 3 depicts the cabin ppCO2 results of this scenario. 

 

62
0

1

2

3

4

5

6

7

8

9

0 10 20 30 40 50

Time (hours)

ppCO2 (mmHg)

60

sleep sleep sleep

EVA CO2 regen exercise exercise CO2 regen

Figure 29 - Lunar EVA Mission Scenario Cabin ppCO2 

2.3.2 Discussion of Test Results – Integration Test with TSAC 

2.3.2.1 Results - 4BMS + TSAC 

The 4BMS and TSAC were tested together over a range of CO2 feed rates to better 

define the TSAC operating envelope and to provide data for further design 

improvements. In order to understand the impact of the TSAC on the 4BMS, a test plan 

was developed to compare operating effects. The 4BMS was operated in a stand-alone 

open loop mode, and then integrated with the TSAC under similar input conditions. Table 

2 below lists the test conditions and the results for the two different operating modes. The 

CO2 removal efficiency of the 4BMS was an average of 2.75% less when integrated with 

the TSAC than in open-loop mode, desorbing to vacuum. The worst effect was in the 

middle of the range of input CO2 concentration, 2.6 mmHg ppCO2, where the efficiency 

dropped 5% when the TSAC was added. Figure 4 below shows the difference between 

the two sets of operating conditions. 

Table 13 - Operating parameters for 4BMS / TSAC comparison tests 

Inlet CO2 

Concentration 

CO2 

Removal 

4BMS CO2 

Removal 

Efficiency 

Loss with Data File 

63
(mmHg) Rate (lb/hr) Efficiency 

(%) 

TSAC 

4BMS Compare #1 5.30 0.73 69 2% 

TSAC Test #1 5.27 0.71 67 

4BMS Compare #3 3.31 0.56 85 3% TSAC Test #2 3.28 0.54 82 

4BMS Compare #4 2.63 0.44 84 5% TSAC Test #3 2.65 0.41 79 

4BMS Compare #5 1.96 0.32 84 1% TSAC Test #4 1.94 0.32 83 

Effect of Adding TSAC to 4BMS CO2 Removal Efficiency

0

10

20

30

40

50

60

70

80

90

1.9 2.6 3.3 5.3

Inlet CO2 Concentration (mmHg)

CO2 Removal Efficiency (%)

Open Loop 4BMS Efficiency

4BMS with TSAC Efficiency

Figure 30 - Graphical presentation of integration effects on 4BMS efficiency 

One objective of the 4BMS / TSAC testing was also to obtain parametric data for the 

TSAC for sizing and evaluation. Table 3 lists the test parameters for these tests along 

with the performance targets and actual results. These tests were described in the ICES 

paper 2006-01-2271 “Integrated Test and Evaluation of a 4-Bed Molecular Sieve, 

Temperature Swing Adsorption Compressor, and Sabatier Engineering Development 

Unit.” 

Table 14 - TSAC Performance Target and Actual Results 

Test Point 

Description 

Test 

# 

4 BMS 

Inlet 

ppCO2 

4 BMS 

CO2 

Removal 

TSAC 

Production 

Rate 

TSAC 

Delivery 

Pressure 

TSAC 

Loading 

Pressure 

Comments 

psi 

mmHg 

kg/day Target / kg/day mmHg 

Target / Result 

Result 

Target / 

Result 

Target / 

Result 

1 5.27 8 / 7.7 4 / ?? 4.2 / 4.24 1000 / This Integrated 

4BMS/TSAC 

64
1002 condition is 

not listed in 

the ICES 

paper 

baseline test 

2 3.28 5 / 5.39 4 / ?? Max / 4.24 1000 / 

1002 

ICES Test 

#1 

Integrated 

4BMS/TSAC at 

reduced CO2 

loading, 5 

kg/day 4.2 kg/day 

3 2.65 4 / 4.5 4 / ?? Max / 4.07 1000 / 

1004 

ICES Test 

#3 

11/18/05 

9:06 AM to 

11/19/05 

6:13 AM 

Integrated 

4BMS/TSAC at 

reduced CO2 

loading, 4 

kg/day 

4 2.58 4 / 4.16 4 / ?? Max / 2.89 1000 / 

1004 

ICES Test 

#4 

11/21/05 

9:06 AM to 

11/22/05 

7:12 AM 

Integrated 

4BMS/TSAC at 

4 kg/day and 

no vacuum 

desorb of 

4BMS 

5 1.94 3 / 3.49 4 / ?? Max / 3.99 1000 / 

1003 

ICES Test 

#5 

11/19/05 

4:28 PM to 

11/20/05 

11:41 AM 

Integrated 

4BMS/TSAC at 

reduced CO2 

loading, 3 

kg/day 

6 3.26 5 / 5.96 6 / ?? Max / 4.75 

/ 

1000 / 

1004 

ICES Test 

#2 

Integrated 

4BMS/TSAC at 

increased CO2 

loading 

pressure 4.8 kg/day 

2.3.2.2 Results - 4BMS + TSAC + Sabatier 

This section describes the test results for the 4BMS, Temperature Swing Adsorption 

Compressor and Sabatier integration test series. Five different test points were run, each 

with a different set of operating conditions. The summary of test results is given below in 

Table 3 along with the summary data from 4BMS + TSAC parametric testing. 

2.3.2.2.1 Integrated Test Results - Nominal Steady State Operation 

Some of the TSAC integration tests were conducted at nominal steady state inlet 

conditions to baseline the performance of the systems together. These first three test 

points were conducted with steady CO2 feed flow to the CDRA and continuous operation 

of the Sabatier. These cases resulted in sufficient CO2 capture by the TSAC so that there 

were no periods of Sabatier starvation. The excess CO2 not needed by the Sabatier was 

65
vented by the CDRA directly to the vacuum vent. Figure 5 below illustrates typical 

TSAC performance for Test Point #1. This test point was run with very high CO2 

loading, 8.3 EP. The pink and blue lines are the alternating TSAC bed pressures. There is 

instrumentation error between the pressure sensor measuring the 4BMS bed and the 

pressure sensor measuring the TSAC bed. The CDRA discharge pressure must be higher 

in order to flow to the TSAC. The saw tooth lines at about 10 psia are the equilibrium 

pressures when each TSAC bed has completed adsorbing CO2 from the desorbing CDRA 

bed. The saw tooth pressure is the result of the 4BMS bed heater cycling to maintain 

temperature while the CO2 is desorbing. The smooth lines at about 20 psia are each of 

the desorbing TSAC beds providing continuous flow to the Sabatier. As long as the green 

line at the top of the graph (Sabatier inlet CO2 pressure) remains above 18 psia, then the 

Sabatier is allowed to operate (shown by the purple line at the bottom of the graph). The 

brown line is the vacuum tank pressure. The large spike at each TSAC bed change is 

from the CDRA going into the 10 minute space vacuum desorb portion of its operating 

cycle. The smaller peaks in the middle of each half cycle are from the vent valve opening 

to relieve the CDRA pressure. 

0

5

10

15

20

25

10.75 10.8 10.85 10.9 10.95 11 11.05

Sabatier Inlet CO2 Pressure

TSAC Bed A Discharge Press

TSAC Bed B Discharge Press

Sabatier Operating Status

Test Point 1 4BMS/TSAC Comparison

Sabatier Inlet 

pressure is always 

above 18 psia

End of 

adsorption 

equilibrium 

pressure

CDRA Discharge Pressure

Vacuum Tank Pressure

Sabatier is 

always on Large peak, 10 

minute vacuum 

desorb

Small peak, vent 

valve relief

Figure 31 - Typical TSAC Performance Data 

66
Table 15 - Test results for 4BMS / TSAC / Sabatier integrated testing 

TSAC 

Loading 

(Suction) 

Pressure 

at End of 

Cycle 

(kPa) 

(Torr) 

Sabatier 

Reactor 

Hot 

Zone 

Temp 

(°C) 

TSAC 

Production 

(Sabatier Demand) 

Rate 

(kg/day) 

(slpm) 

Sabatier 

Reactor 

Outlet 

Temp 

(°C) 

TSAC 

Production 

Pressure at 

End of 

Cycle (kPa) 

(Torr) 

Sabatier 

Reactor 

Inlet 

Pressure 

(kPa) 

(psia) 

Number 

of 4BMS 

Vent 

Cycles in 

Integrated 

Operation 

4BMS 

Inlet 

CO2 

Conc. 

(mmHg) 

4BMS 

CO2 

Loading 

(kg/day) 

4BMS 

Removal 

(kg/day) 

Sabatier 

H2 Feed 

Rate 

(slpm) 

Sabatier 

Starvation 

Period 

(min) 

Sabatier 

Water 

Production 

Efficiency 

Objective 

of Test 

Point 

Cabin 

CO2 

Utilization 

Test 

Point 

(lb/hr) 

(°F) (°F) 

Steady 

State Load 

Conditions, 

8.3 EP 

1 10.90 5.21 7.57 72.79 141.09 5.23 6.76 72.48 534 74 0 93% 70% 

(0.72) (10.56) (1058.26) 1.85 10.51 993 166 

SS 5.46 EP 2 7.51 3.42 6.20 42.75 141.11 3.43 4.45 69.21 527 74 0 93% 55% 

(0.57) (6.20) (1058.42) 1.21 10.04 981 165 

SS 2.34 EP 3 3.27 1.48 2.46 26.28 141.15 1.49 1.91 65.05 472 69 0 92% 61% 

(0.23) (3.81) (1058.69) 0.53 9.43 882 157 

Lunar Night 4 5.56 2.52 4.50 32.36 141.15 2.53 3.26 67.50 518 73 41 0 95% 45% 

(0.41) (4.69) (1058.74) 0.90 9.79 965 163 

Lunar EVA 

Exit 

5 

Part 

1 

2.91 1.34 0.54 31.61 141.17 2.51 3.2 67.32 517 72 14 95% 71% 

0.18 4.59 1058.87 0.89 9.76 962 162 

Lunar EVA 

Return 

5 6.07 2.74 4.27 42.30 137.38 2.37 3.16 64.59 512 71 174 23 92% 62% 

Part 

2 

0.39 6.14 1030.45 0.84 9.37 953 100 

67
Test points 2 and 3 were designed to copy the operating conditions of the previously 

completed mechanical compressor integrated tests. The 3 and 5.4 EP CO2 loading cases 

with continuously operating Sabatier were chosen to replicate (refer to cases 1 and 4 of 

the Mechanical Compressor tests). As expected, the equilibrium pressure of the adsorbing 

TSAC bed for each case is related to the CDRA inlet CO2 concentration. This 

equilibrium data is summarized below in Table 5 and illustrated in Figure 6. 

0

200

400

600

800

1000

1200

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6

Time

Pressure (torr)/Temperature (C)

TP1 Bed A Press

TP1 Bed A Temp

TP2 Bed A Press

TP2 Bed A Temp

TP3 Bed A Press

TP3 Bed A Temp

8.3 EP 5.46 EP 2.34 EP

Equilibrium 

pressure of 

adsorbing 

TSAC bed

Bed 

heater 

temps

Production 

pressure of 

desorbing 

TSAC bed

TSAC Performance at Various CO2 Loading

0

200

400

600

800

1000

1200

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6

Time

Pressure (torr)/Temperature (C)

TP1 Bed A Press

TP1 Bed A Temp

TP2 Bed A Press

TP2 Bed A Temp

TP3 Bed A Press

TP3 Bed A Temp

8.3 EP 5.46 EP 2.34 EP

Equilibrium 

pressure of 

adsorbing 

TSAC bed

Bed 

heater 

temps

Production 

pressure of 

desorbing 

TSAC bed

TSAC Performance at Various CO2 Loading

Figure 32 - TSAC equilibrium loading pressure is dependent on CO2 feed to CDRA. 

Table 5 below lists water production efficiency data for the various scenarios tested with 

the 4BMS, TSAC and Sabatier. The Sabatier was upgraded from the previous 

configuration that was tested with the mechanical compressor, so the efficiency data 

cannot be directly compared. The upgraded Sabatier EDU has a rotary phase separator, 

which spins all the time to separate the gas and liquid phases in micro-gravity. Some of 

the excess heat from the separator motor goes into evaporating the product water, which 

lowers the recovery efficiency. The previous version of the Sabatier EDU had a tank 

separator with a pump that only operated when the tank was emptied. For a gravity based 

mission, such as a lunar habitat, a tank and pump would be the preferred separator. 

68
Table 16 - Sabatier Efficiency Data when Integrated with TSAC 

Sabatier Hot 

Zone 

Temperature 

with 

Mechanical 

Compressor 

Sabatier 

Water 

Production 

Efficiency in 

Equivalent 

Mechanical 

Compressor 

Test 

Sabatier 

Reactor Hot 

Zone 

Temperature 

(C) 

Sabatier 

Water 

Production 

Efficiency 

Sabatier H2 

Feed Rate 

(slpm) 

Sabatier 

Starvation 

Period (min)

Test 

Point Description 

(F) (C) 

(F) 

Compare to 

4BMS/TSAC baseline 

534 

1 6.76 0 993 94% 

Compare to Mech. 

Comp TP4 

527 510 

2 4.45 0 981 92% 950 94% 

Compare to Mech. 

Comp TP1 

472 454 

3 1.91 0 882 87% 850 89% 

518 Lunar night scenario 4 3.26 41 965 89% 

Full crew EVA 

5 Part 1 departure 3.20 14 

517 

962 96% 

Full crew EVA return 

and regenerate 

512 86% 

5 Part 2 3.16 174 953 (peak 91%) 

Stand alone Sabatier 

EDU Test prior to Mech 

Comp. Integration 

535 

NA 9.0 NA 995 92% 

Stand alone Sabatier 

Upgrade EDU test prior 

to TSAC Integration 

504 

NA 2.65 NA 940 92% 

2.3.2.2.2 Integrated Test Results - Simulated Mission Profiles 

In addition to the steady state tests, lunar mission cases described previously in Section 

2.2.3.1.2 were tested. The simulated cabin CO2 concentration profile, which was the 

result of the cabin atmosphere simulation model, was used as the input profile of CO2 fed 

to the CDRA. 

Test point number 4 was a lunar night scenario. At the South Pole, the lunar night lasts 24 

to 48 hours straight, once per month. Since operations would depend on battery power 

when no solar power is available, it is likely that the oxygen generator would be turned 

off. Without hydrogen, the Sabatier would also shut down and the TSAC compressor, 

likewise. A scenario was simulated in which the TSAC and Sabatier were turned off partway through a CDRA cycle, and allowed to completely cool down before restarting. 

Figure 7 below shows the results of the simulation when the systems were turned off, 

allowed to cool, then turned back on. 

69
32 minutes into Bed B adsorb 

cycle CDRA turned off

After turning back on, Bed B doesn’t 

have enough CO2 for full cycle

Lunar Night Cycle Simulation with CDRA/TSAC/Sabatier

Sabatier should 

have turned on here

Figure 33 - Results of simulated Lunar night 

During the simulation, the CDRA continued to operate as it would be required to 

properly maintain the atmosphere in the habitat. The CO2 desorbed from the CDRA was 

vented to the vacuum system as long as the TSAC was turned off. The systems were 

turned back on 120 minutes into the CDRA cycle, when there was essentially no more 

CO2 to transfer to the TSAC. The bed that had been adsorbing during the shutdown had 

only received a partial fill and during the following cycle there was not enough CO2 

captured to operate the Sabatier continuously. The systems recovered to normal operation 

following one full CDRA cycle. The starvation effect could be minimized by starting up 

the TSAC one half cycle ahead of the oxygen generator and Sabatier as long as the 

atmosphere oxygen concentration would allow further delay. 

70
0

5

10

15

20

25

27.5 28 28.5 29 29.5 30 30.5

Tme (days)

CO2 Pressure (psia)

0

0.25

0.5

0.75

1

1.25

1.5

CO2 Concentration (%)

TSAC Bed A Press TSAC Bed B Press Sabatier Inlet CO2 Press Cabin CO2 Conc Sabatier Status

Sabatier feed 

pressure falls every 

TSAC bed change

One full cycle 

delay between 

CDRA intake 

and TSAC 

delivery

Integrated Performance During 

Simulated Lunar EVA Mission

0

5

10

15

20

25

27.5 28 28.5 29 29.5 30 30.5

Tme (days)

CO2 Pressure (psia)

0

0.25

0.5

0.75

1

1.25

1.5

CO2 Concentration (%)

TSAC Bed A Press TSAC Bed B Press Sabatier Inlet CO2 Press Cabin CO2 Conc Sabatier Status

Sabatier feed 

pressure falls every 

TSAC bed change

One full cycle 

delay between 

CDRA intake 

and TSAC 

delivery

Integrated Performance During 

Simulated Lunar EVA Mission

Figure 34 - Simulated Lunar EVA Excursion profile results in long periods of Sabatier starvation. 

Figure 8 above shows the results of a simulated lunar EVA mission. The CO2 

concentration feeding the CDRA is the result of a simulation of a habitat with 4 

crewmembers with periods of EVA followed by regeneration of the EMU CO2 collection 

canisters in the habitat. There is a time delay of one CDRA cycle (4.8 hours) between 

when the CO2 concentration in the cabin drops and when the CO2 delivered to the 

Sabatier is insufficient. This effect could possibly be corrected with intelligent software 

that lowers the O2 production rate (therefore lowering the Sabatier processing rate) 

during periods when the TSAC bed loading is low. The final loading pressure of the 

TSAC bed in its previous half cycle is an indicator of the total bed loading and what the 

delivery capability will be in the next half cycle. 

2.3.3 Conclusions from This Test Section 

The testing described herein was the first integrated test of a 4-Bed Molecular Sieve, 

Temperature Swing Adsorption Compressor, and Sabatier Reactor. Five successful tests 

were completed with these three systems. These tests provided enhanced understanding 

71
of both nominal, steady-state operation and dynamic, transient scenarios that can be 

expected to occur on a Lunar base. Six additional 4BMS-TSAC tests explored widely 

varying 4BMS loading conditions and the corresponding response of the TSAC. In 

general, the three systems were proved compatible and able to perform their intended 

functions for a wide range of input conditions. 

These specific conclusions are drawn from these test results: 

• The dynamic transients expected in a Lunar EVA scenario were played out in 

Test Point 5. The CO2 concentration changes due to crew movement into and out 

of the habitat. The response of the systems is delayed, one system to the next, as 

each system progresses through half cycles. The hydrogen generation rate (byproduct from oxygen generation) is current with crew activity. The CO2 delivery 

rate is delayed by one half cycle. This mismatch results in Sabatier starvation. 

Adaptive software may be a solution to better match the hydrogen and CO2 rates 

to feed the Sabatier. There should be sufficient oxygen concentration buffer to 

allow delayed oxygen production while waiting for the CO2 to be concentrated. 

• Large variations between half cycles were noted during the Lunar EVA scenario. 

The causes for these variations need to be understood and rectified. 

• The TSAC had, on average, less than 5% negative impact on the 4BMS 

performance. However, much higher deviation was noted at 2.6 torr inlet ppCO2 

and bears further review. 

• A 4BMS heater ramp control algorithm can save about 50 watts (time averaged 

power). However, refinements to the TSAC operation will be required to prevent 

gaps in the CO2 production to the Sabatier. 

• Additional work is required to prevent TSAC exposure to humidity from room 

air. The TSAC material’s sensitivity to humidity required it to be extensively 

purged after inadvertent exposure to room air. Isolation mechanisms should be 

implemented and tested to prevent air leakage during 4BMS shutdowns. 

• Additional refinements to the overall control software are required for better 

communication between the 4BMS, TSAC and Sabatier. 

• The Sabatier software performed a vacuum leak check during every transition to 

Standby. If the water level was sufficiently high, the separator would be instructed 

to pump out the water during the vacuum leak check. The separator cannot create 

enough pressure rise when at vacuum to satisfy the pump out requirement, which 

then causes a system shutdown. An adjustment to the Sabatier control is required 

to prevent separator triggered shutdowns during standby mode. 

• The Sabatier required CO2 pressure deadband should be a minimum of 3 psi 

when integrated with a TSAC. The low pressure for Standby should be 16 psia 

and the high pressure should be 19 psia when operating at the conditions used in 

this test program. A smaller deadband results in valve chatter while the TSAC is 

heating up and generating pressure. 

• The TSAC and 4BMS need sufficient communications to synchronize their half 

cycles and to signal each when shutdowns and initiated. 

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3 Conclusions 

The testing described herein was the first integrated test of a Four-Bed Molecular Sieve, 

Sabatier Carbon Dioxide Reduction Assembly with the interfacing CO2 compressor. Two 

compressor technologies were tested, a mechanical oil-free piston compressor, and a 

temperature swing adsorption compressor. The mechanical compressor was tested under 

simulated International Space Station parameters. The TSAC was tested under simulated 

Lunar Base parameters. Both sets of tests provided enhanced understanding of both 

nominal steady operation and dynamic, transient scenarios that can be expected to occur 

in an integrated Environmental Control and Life Support System. 

Additionally, the compressors were tested independently and with only the 4BMS over 

varying CO2 loading conditions. The corresponding compressor response to changing 

conditions was observed. 

In general, the 4BMS, Sabatier and both compressor technologies were proved 

compatible and able to perform their intended functions for a wide range of input 

conditions. 

3.1 Overall Conclusions from the Integration Test Experience 

The integration test of the 4-Bed Molecular Sieve with two different compressors and a 

Sabatier reactor was a successful test program. The testing showed that these systems 

could be properly integrated together. There is no significant, detrimental impact on the 

4-Bed CO2 removal system when desorbed with a compressor instead of space vacuum. 

4-BMS CO2 removal efficiency was well above requirements for the wide range of CO2 

inlet concentrations tested. The different systems’ control logic in place during this test 

program supported the wide range of conditions tested. These tests provided enhanced 

understanding of both nominal, steady-state operation and dynamic, transient scenarios. 

In general, the three systems were proved compatible and able to perform their intended 

functions for a wide range of input conditions. 

3.2 Summary of Observation from the Integration Test 

These specific conclusions are drawn from the test results: 

• Both compressors (TSAC and mechanical) had a small but measurable effect 

on the CO2 removal performance of the 4BMS. Since the vacuum level is not as low 

as space vacuum, some residual CO2 remains on the CO2 removal beds, which in 

turn reduces their capacity on the next adsorb cycle. During the mechanical 

compressor testing, the performance reduction was 5.4%. During the TSAC testing, 

the performance reduction ranged from 1-9% with an average of 4.2%. The integrated 

73
performance may be improved with longer space vacuum desorb time or higher 

temperature. This subject is a candidate for further testing. 

• As a result of this testing, the mechanical compressor simulation model was modified 

to better predict flow at low suction pressures. 

• The 4-BMS model was also updated to incorporate a leakage factor to estimate air 

leakage into the system components that operate at vacuum. 

• The dynamic transients expected in a Lunar EVA scenario were evaluated in the 

TSAC testing. The test results showed a significant time delay from crew activity to 

system performance. Adaptive software may be a solution to better anticipate system 

changes and to alter production rates to maintain system balance. 

• Both compressors had, on average, less than 6% negative impact on the 4BMS 

performance. 

• A modified 4BMS heater ramp control algorithm was tested and resulted in power 

savings, however gaps in CO2 delivery occurred. The prospect of power 

improvements is likely and future testing of modifications to the heater schedule is 

warranted. 

• Additional work is required to prevent TSAC exposure to humidity from room air by 

implementing isolation mechanisms. 

• Additional refinements to the overall control software are required for better 

communication between the 4BMS, TSAC and Sabatier. 

• The TSAC and 4BMS need sufficient communications to synchronize their half 

cycles and to signal each other when shutdowns are initiated. 

• The current compressor operation/control logic appears to support a wide range of 

test conditions, but modifications may need to be made in order to reduce starvation 

during the low EP cases as well as reduce the number of brief operation cycles during 

high EP loading. 

• Also, the impact of increased cycles on the 4BMS vacuum vent valve should be 

evaluated to determine if these operating rules could be improved. 

• The data collected over the course of integrated testing is currently being compared 

with predictions from existing models to validate the model against test data. The 

model is being adjusted as required to duplicate test results. Thus far it has been 

determined that the current compressor model does not adequately predict flowrate 

through the compressor at low suction pressures. A curve fit has been added to the 

compressor model based on test results. In addition, the impact of vacuum circuit inleakage has become very evident upon comparison of test results with model 

74
predictions. Efforts are underway to estimate the current bed leak rates and 

incorporate them into the model as a “worst case”. An operational flight system, once 

leakage due to sorbent dusting is eliminated, is expected to have a much lower leak 

rate. 

• The impact of in-leakage on the system and its operating rules cannot be ignored 

since in-leakage results in increased compressor run time as well as decreased 

Sabatier efficiency. While it may be difficult to implement, any future plans regarding 

the integration of a flight CDRA with a CRA should also involve re-evaluating 

existing protocols for verifying CDRA as well as CRA leak rates. As observed in this 

test, current CDRA/4BMS leak test procedures could result in significant in-leakage 

that impacts CRA performance. 

• The dynamic transients expected in a Lunar EVA scenario (TP 5) provided insight on 

the delayed response of both the 4BMS and TSAC. Consideration of adaptive 

software to better utilize large influxes of CO2 is suggested. 

• Large variations between half-cycles were noted during the Lunar EVA scenario. The 

specific causes for this trend need to be understood and rectified. 

• The TSAC had, on average, less than 5% negative impact on the 4BMS performance. 

However, much higher values were measured at about 2.6 torr inlet pp CO2, and bear 

further review. 

• A 4BMS heater ramp control algorithm can save about 50 watts (time-averaged 

power). However, refinements to the TSAC operation will be required to prevent gaps 

in CO2 production to the Sabatier. 

• Additional work is required to prevent TSAC exposure to room air. An isolation 

valve, or other appropriate solution, should be implemented and tested. 

• Additional refinements to the overall control software are required for better 

communication between the 4BMS, TSAC, and Sabatier. 

• An adjustment to the Sabatier control is needed to prevent separator-triggered 

shutdowns following standby mode. 

• 4BMS performance was well above requirements for the range of inlet CO2 

concentrations tested. 

• In general, the current TSAC operation/control logic appears to support a range of test 

conditions, but a more robust test matrix should be explored in future. 

• Upgraded components within the Sabatier EDU performed as expected. 

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• Lessons learned from this test can, should, and will be incorporated into future 

revisions of the CDRS hardware. 

3.3 Lessons Learned 

3.3.1 Lessons Learned from the Integration Testing 

This section documents the Lessons Learned, Anomalies and Resolutions that were 

implemented as part of the integrated testing. 

• Hydrogen flow rate inconsistent across various measurement means, system mass 

balance not in check. Sabatier water production efficiency calculation is based on 

hydrogen flow rate. 

o Critical parameters that are used to evaluate system performance against 

requirements must be accurate and verified against accepted standards. 

• Loss of network communication from the Sabatier system led to a crash of the 

overall control computer, which in turn led to shutdown of the other subsystems. 

o Control systems need to be designed such that subsystems can continue to 

operate independently if they lose contact with the main controller. In the 

case of the ARS, the CDRA is considered critical life support and needs to 

have the capability to continue operation in the absence of higher level 

commands. The Sabatier software must be designed to not propagate 

errors outside its boundaries. 

• The Sabatier system rapidly cycled from Process to Standby during operation 

with the TSAC compressor during low CO2 production rates. The transition was 

keyed off of CO2 supply pressure limits. The Sabatier operating bands designed 

initially for the mechanical compressor operation were too tight for TSAC 

operation. Pressure bands were widened to allow smoother, slower mode 

transitions and avoid rapid cycling. 

o System triggers that initiate logic decisions (such as changing operating 

mode, activating control loops, etc) must be examined and exercised over 

the widest range of operating conditions possible. The problem during the 

testing was resolved by changing the set points for the transition 

commands. These type of set points should also be variable in the control 

software so they can be adjusted to optimize operation.

• The Sabatier phase separator pump attempted to pump water out of the system 

when in standby while the pressure was very low. The pump could not overcome 

the differential pressure to pump out water when the system pressure was so low. 

o The Sabatier flight software was designed to prevent the separator from 

pumping water during any low-pressure conditions. The software also 

performs a pump-out prior to transitioning to Standby while there is still 

pressure in the system to aid the pumping. 

• The Sabatier system rapidly between Standby and Process such that the Standby 

evacuation was not completed. Valves were chattering during the transition. The 

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action of the valves cause pressure changes that in turn changed status in the 

software that caused the valves to change position again. This was another artifact 

of control ranges set too close together. The transitions were taking place prior to 

completion of purge steps and the software ended up caught in an indeterminate 

state. 

o Software logic should be designed such that sequences are completed 

before subsequent operating state changes are allowed to occur. Checks 

should be incorporated to verify that procedures (such as purges) are 

completed. 

• If the Sabatier had gone through a shutdown and was still hot, upon restart it 

would go directly to Process without performing the required purge in Standby 

first. Apparently the temperature requirement was met and the software did not 

wait for the purge requirement to be met. 

o Software must be written to ensure that all requirements are met, not just 

the first requirement. Careful testing is often needed to flush out these 

types of errors in code, as it is often only a unique set of circumstances 

will create the right conditions for these anomalies. 

• Sabatier reactor thermal soak back – when flow to the reactor stops (as in Process 

to Standby transition) the heat of the reactor soaks back to the inlet. This was 

accommodated in the Sabatier EDU by increasing high temperature shutdown 

limits. The flight reactor design also acknowledged this phenomenon and 

designed the inlet end instrumentation to tolerate high temperature. 

o Component and controls design must consider all conditions, including 

non-operational conditions.

• 4MBS heater ramp rate – during the TSAC testing, the 4BMS heater control was 

modified from a fixed temperature setpoint control to a ramp rate in which the 

temperature linearly increased from 60 to 400 F. The result of this test was a 

savings of 50 W time averaged over the desorption cycle, however, less CO2 was 

desorbed from the 4BMS to the TSAC during the cycle. The overall integration 

result was starvation of the Sabatier reactor for steadily increasing durations. Due 

to the potential power savings, further evaluation of modified desorption 

schedules is warranted. 

• TSAC sensitivity to leaks – during testing, the TSAC was inadvertently exposed 

to room air several times. Since the adsorbent material is very sensitive to 

humidity, the TSAC had to be taken offline and purged for an extended period of 

time before resuming testing. 

o Future integrated designs must include means of isolating the TSAC to 

prevent accidental exposure to cabin air. Subsystem design must consider 

operating and non-operating states that may be damaging to the 

hardware. 

• Integrated TSAC / Sabatier control pressure – as a result of the testing, it was 

determined that a minimum of 3 psid is needed for the Sabatier setpoints for CO2 

pressure. When the Sabatier transitions to Process, the initial draw of CO2 lowers 

77
the TSAC pressure by more than 2 psid. If the transition setpoints are too close 

together, the systems will cycle rapidly between Process and Standby. 

• Air effects on Sabatier performance – temperature anomalies were noted in the 

Sabatier profile during the mechanical compressor testing. It was concluded that 

the temperature spike at the reactor inlet was due to higher than normal 

concentration of air during a 4BMS bed switching event. The Sabatier reactor is 

robust to the presence of air and its known temperature profile proved to be a 

good indicator of altered operating conditions. 

o A future test item would be to determine if the reconfigured Sabatier 

reactor temperature sensors are as sensitive to detecting air inclusion as 

the EDU Sabatier. 

• Sabatier Phase Separator operation at vacuum – testing determined that the rotary 

phase separator cannot pump water out when the gas pressure is at vacuum. The 

flight operating control is configured to empty the separator at the beginning of a 

Standby transition when the gas pressure in the system is still relatively high. 

• CDRA leak check – A significant observation made during integrated testing was 

that hardware leakage could be masked if the hardware is leak checked while not 

in operation. For example, during initial integration testing, the 4BMS passed 

leakage testing, yet significant air in-leakage was observed during testing. The 

root cause was a selector valve that was cold-soaked during operation that caused 

the soft goods to shrink and allow leak paths. The valve was not cold during the 

static system leak check, and therefore passed the test. 

o Systems need to be leak checked in their operating environment to ensure 

trouble free operation. 

3.3.2 Lessons Learned from the Sabatier Flight Program 

This section documents Lessons Learned that were incorporated into the flight Sabatier 

design as a result of the integration testing. 

3.3.2.1 Hardware Changes Required 

• Hydrogen Vent Tee – the space station OGS rack was initially designed with a 

scar for the Sabatier Assembly to be added at a later date to the Oxygen 

Generation Assembly, but the Sabatier design was not very far advanced at the 

time the rack was launched. The initial plan was for the Sabatier to vent in the 

same line as the CDRA. This was later changed to having the Sabatier use the 

hydrogen vent from the OGA instead. 

o The implementation of this change required the addition of a tee line that 

would be inserted at the interface panel quick disconnect. The change also 

78
imposed restrictions on the rate of discharge of the Sabatier to meet the 

restrictions of the shared vent line. 

3.3.2.2 Software Changes Required 

• CDRA Control Software – the flight CDRA software did not have provisions for 

interface commands related to a Sabatier system. The software had to be modified to 

keep the bulkhead vent valve closed so that the Sabatier could extract the CO2 from 

the desorbing CDRA beds. The CDRA venting logic, as noted earlier, is different for 

the flight system than the ground test system. Once the flight system bed pressure 

exceeds 8 psi, indicating that the compressor has not been activated, the vacuum vent 

valve is opened and left opened for the remainder of the desorption cycle. The loss of 

recovered CO2 is acceptable at this point since the accumulator is likely full or the 

system is not operational. This modification keeps the total number of cycles on the 

vacuum vent valve the same as that for which they were originally designed. 

• OGA Evacuation Check – the OGA will check the pressure in the Sabatier hydrogen 

delivery line before opening the valve to deliver hydrogen. If the pressure is high, the 

Sabatier could potentially have air in it. The OGA will not deliver if the pressure is 

too high to avoid a potentially hazardous condition. The pressure limit was initially 

0.3 psia. This limit was too low, as the Sabatier pressure would at least be that of the 

vapor pressure of water in the phase separator, plus any instrumentation error in the 

pressure sensor. The limit was raised to 3.0 psia and the change made to the OGA 

software. 

• Phase separator pumpout – as a result of the integrated testing, the flight Sabatier 

software included provisions to pump out the phase separator at the very beginning of 

a transition to Standby while there is still sufficient gas pressure in the separator. The 

software then does not allow the separator to pump out any other time in Standby. 

3.4 Recommendations for Subsystem Modification if Designing 

a New System 

• CDRA/TSAC combined design 

79
 Can there be weight/power/volume savings if the CDRA and TSAC were 

designed as a single system? LPCOR 

• CDRA / OGA cycle mismatch 

 The ARS system on ISS is designed with the OGA operating on a 90 

minute diurnal cycle, which matches the station orbit. The OGA would be powered and 

producing hydrogen during the “day” when power is plentiful and in standby during the 

“night” when power is scarce. The CDRA operated on a 144 minute half cycle. The 

mismatch in cycle times requires the use of storage volume to collect CO2 when 

hydrogen is not available to process. 

 This would be a good area to investigate in the future, either through 

modeling or testing, to see if matched cycles results in less starvation or smaller 

accumulator volume. 

• CDRA Power Usage – Desorption Rate 

The current design of the 4MBS has the heaters turn on full power during 

the desorption phase if the station is in the daylight portion of the orbit. Testing with both 

compressors has shown that the 4BMS can retain CO2 in the bed for a significant period 

of time as long as the bed is evacuated to space vacuum for the final 10 minutes of the 

cycle. The 4BMS may possibly be operated such that the bed is pressure controlled 

instead of temperature controlled to save power when the compressor is not ready to 

receive CO2. This would prevent venting of the CO2 from the 4BMS to space vacuum. 

Investigate by modeling or testing. 

• CO2 tank proof pressure 

 During the period of time leading up to the Integration Test program, the 

OGA for the International Space Station was designed and built. Coincidental 

development of the Sabatier led to incorporation of accumulator tanks into the OGS rack 

prior to its launch. The volume available for these tanks was smaller than desired, but 

development testing of the mechanical compressor showed that the compressor could 

meet the higher pressure demand required to offset the smaller volume. Although these 

tanks were designed and manufactured to accommodate very high pressures, they were 

only proof tested to 160 psia. The application of sensor inaccuracies and control bands to 

the operating system requirements resulted in a usable maximum operating pressure of 

only 115 psia. In practice, this lower operating pressure will result in greater venting of 

CO2 overboard and likely associated Sabatier starvation. Interfacing systems should be 

proofed to as high a pressure as possible per the results of trade studies. The CO2 

accumulator for ISS was proofed to 145 psig (160 psia), but the application of sensor 

accuracies to overpressure protection reduces the actual maximum operating pressure to 

100 psig (115 psia). 

 

• Shared Vent Lines - Restriction on flow, temperature, MDP, 

 In the ISS design, the Sabatier shares the vent line with the OGA. The vent 

line was sized and proof tested to meet the requirements of the OGA alone. During 

integrated operation, there are times when both systems must be able to vent gases 

80
through this line at the same time. The line is not sized to accept this much flow without 

creating excessive back pressure. The Sabatier must therefore restrict the rate at which it 

allows venting gases to flow into the line. 

 Future integrated designs must consider all operating scenarios, including 

startup and shutdown, as input to designing interfacing systems (i.e. vent line). 

• Coolant Interface 

 The coolant temperature directly affects the percent of water recovery of 

the Sabatier system by setting the dew point temperature at the phase separator. Coolant 

temperature should certainly be included in any trade study for future ARS designs. The 

additional water recovery would have to be traded against issues of external condensation 

on coolant lines if installed in a habitable volume of the spacecraft or habitat. 

• OGA Interface – Pressure Check 

 The design of the ISS controls requires that the OGA verify that the 

Sabatier had been vented prior to allowing hydrogen to flow to the system. This is done 

for system safety to prevent introduction of hydrogen to the Sabatier if it was full of air. 

The target pressure value had been set to 0.1 psia to verify evacuation. However, this 

value is not achievable when the Sabatier system has water in the phase separator. When 

evacuated, the inlet pressure will be something more than the vapor pressure of water at 

the phase separator temperature. For ISS installation, a modification will have to be made 

to the OGA software to raise the pressure limit used for the interface check. 

 This system check also requires that the Sabatier be evacuated during 

every standby. This results in some product water loss. The water recovery gained by not 

venting would have to be traded against other methods of preventing flammable 

mixtures. 

• Waste Water Bus MDP 

 The waste water bus on ISS has a MDP of about 90 psig. The Sabatier 

system was designed with an MDP of 268 psig to provide containment as a final means 

of protection against damage due to detonation. The interface of the phase separator to 

the waste water bus was an area of concern due to the possibility of transmitting a 

pressure wave through the water lines. I will get the details on how this was resolved. 

• Location in Habitable Volume 

 The ISS ARS is designed with all components in the habitable volume. 

This then requires that all of the components that contain flammable gas have either 

secondary containment (the OGA dome) or be operated at sub-ambient pressure to 

prevent leakage of gas out into the cabin. The sub-ambient operation results in a water 

recovery penalty, as the lower system pressure increases the volume fraction of water 

vapor that is vented with the methane product gas. For exploration systems, locating the 

flammable gas components outside the habitable area would allow operation at higher 

pressure, and therefore increase water recovery. There may be other benefits of volume 

and mass savings achieved by operating at higher pressure. 

81
• Acoustics and EMI Restrictions 

 Acoustics and EMI are not insurmountable requirements, but add weight 

and volume to systems for attenuation. Location of the system outside the habitable 

volume may lessen the burden of acoustic and EMI requirements. 

4 Recommendations 

4.1 Recommended Future Testing 

This integrated test program has shown that a closed loop Air Revitalization System is 

achievable and practical. However, there is insufficient data from either integrated test to 

draw conclusions about the long term effects of each compressor on the 4BMS operation, 

and vice-versa. The testing uncovered possible areas for improvement, and areas where 

more information is needed. The testing has shown that the systems can be integrated 

with acceptable reduction of performance of the 4BMS and the resulting water recovered 

is as much as 90% of what is theoretically possible. Long duration experiments under 

controlled conditions, in terms of 4BMS loading, TSAC loading, compressed CO2 

production, CO2 purity, vacuum levels, etc.., should be performed to better understand 

long term performance. 

4.1.1 Recommended Test Objective 

Any future development should focus on improving the systems’ equivalent system mass 

(ESM - weight, power and volume), efficiency and reliability. Many observations were 

made of potential improvements in ESM and reliability. These potential improvements 

should be the focus of follow on testing or modeling work. 

Due to software control limitations, the integrated tests to date were performed at preset 

operating schedules. Upon adding a more sophisticated and flexible control system, the 

integrated systems should be tested under dynamic operating conditions where the system 

parameters such as CO2 inlet, cycle time, standby time, etc are varied in a non-uniform 

pattern (that are realistic to mission-specific scenarios). 

4.1.2 Specific Recommended Tests 

The following specific test recommendations are made with a focus on discovering 

potential areas for improvement to system weight, power, volume, efficiency or 

reliability. 

• Test integrated combinations of compressors and the 4BMS with different lengths 

of vacuum desorb time and different desroption temperatures to determine if the 

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4BMS CO2 removal efficiency can be improved. The integrated testing showed 

an average loss of CO2 removal efficiency of about 4-5%. This loss may be 

recovered by modifying operating times. 

• Test adaptive software for the overall ARS system to better match CO2 and 

hydrogen availability. This would lead to minimizing instances of Sabatier 

starvation and improved overall water recovery. 

• Test variations of heater ramp algorithms to determine if power savings can be 

achieved in both 4BMS and TSAC components. 

• Test the TSAC with lower pressure cooling air (as might be a design requirement 

for a Lunar base or future spacecraft) or with alternate cooling medium (liquid) as 

might be available in future application. Each will have design impacts on the 

cooling rate and overall efficiency. 

• Use the ground based hardware to verify protocols for evaluating leakage rates of 

in-flight hardware to improve flight system reliability. 

• Further test variable loads, such as the Lunar EVA scenario tested here, to flush 

out the reason for the large variations noted between half cycles. This will lead to 

better understanding of the system operations and ultimately improve efficiency 

and reliability. 

• Investigate the large performance impact noted at 2.6 torr inlet CO2 pressure and 

not at other CO2 concentrations during TSAC/4BMS testing. Perform addition 

tests if warranted. It remains unknown whether this stems from a testing anomaly, 

analysis error, or is indicative of a true performance sensitivity. Additional 

testing will provide a basis for overall system repeatability and measurement 

accuracy. 

• Review test results to determine specific combinations of factors that cause 

subsystem shutdowns and make necessary control modifications. An example is 

the Sabatier separator attempt to empty at vacuum pressure. This protocol was 

corrected in the Sabatier flight software. 

• Perform testing over a more robust range of operating conditions. The wider the 

acceptable operating range, the more flexibility for future loop closure. 

4.2 Recommended Future Hardware Development 

4.2.1 Subsystem Development 

These are some possible development tasks that would result in improvements in ESM 

and reliability based on the results of the completed testing. Additional improvements 

may be discovered as a result of additional future testing outlined above. 

• Develop a heater ramp algorithm for the 4BMS that will save power, yet 

accomplish the CO2 desorption needed. 

83
• Develop isolation mechanism and associated control to prevent room air humidity 

from entering TSAC beds. 

• Improve heat transfer design of the TSAC and the 4BMS in order to reduce power 

usage by investigating the following factors: 

o Arrangement of heaters and cooling ducts to minimize the thermal mass; 

o New adsorbents or adsorbent structures with reduced thermal resistance; 

o Improved package insulation; and 

o Flexibility in design to allow utilization of waste heat. 

• Design TSAC for moisture management which may include system isolation, 

moisture sensing and on-line regeneration. 

• Improve TSAC controls which allow flexibility in startup, operation and 

shutdown, and allow better subsystem communication and synchronization. 

• Implement adaptive software which will allow optimization of product delivery 

based on previous cycle loading, purge control, compression time, and available 

power. 

• Develop subsystems that are modular, that operate more efficiently at reduced 

loading and can be stacked for higher loading. 

• Develop low volume, lightweight, high temperature components. 

• Continue development of the LPCOR system that combines the CO2 removal and 

CO2 compression functions of the 4BMS and TSAC. 

• Through modeling or testing, evaluate the impact of different cycle times for the 

4BMS and Sabatier. Determine if there is an optimum cycle time for each that 

minimizes the accumulator volume and/or overall system power. 

• Evaluate the impact of powering the 4BMS heaters to control bed pressure rather 

than temperature. 

• Evaluate the length of vacuum desorb time needed to fully clear the 4BMS beds if 

the bed is pressure controlled prior to desorption. 

• Determine the water recovery cost/benefit as a result of higher or lower Sabatier 

operating pressure, and the associated system level impacts. 

4.2.2 Component Development 

• Consider all operating and non-operating conditions (such as temperature and 

pressure extremes) when designing components. 

• Test flight-like Sabatier reactor to determine if the temperature sensors are 

sensitive enough to detect excessive air in the CO2 as was noted with the EDU 

reactor. 

• Develop a liquid cooled Sabatier phase separator for maximum water recovery. 

4.2.3 Controls Development 

• Improve communication links between integrated subsystems for synchronizing 

cycles and reporting system anomalies and shutdowns. 

• Improve mechanical compressor operating logic to minimize short cycles and 

reduce starvation at low CO2 loading. 

84
• Improve operating rules for 4BMS vent valve to minimize cycles on the valve. 

• Develop protocols for verification of accuracy of key measurement sensors. 

• Develop software protocols that prevent propagation of failures to other systems, 

and the ability to operate independently if needed. 

• Evaluate system triggers that initiate logic decisions and exercise them over the 

widest practical range of operating conditions. This will prevent issues such as 

rapidly cycling caused by pressure dead bands. 

• Develop controls protocols that can be adjusted by crew intervention or by 

“smart” controls. This will allow a system to acclimate to its environment (for 

example, microgravity) and make necessary adjustments. 

• Design software logic such that sequences are completed before subsequent 

operating state changes are allowed to occur. Checks should be incorporated to 

verify that procedures (such as purges) are completed. 

• Design software such that all conditions are met before transitions occur. Careful 

testing over a wide range of operating conditions is needed to locate errors in 

code. 

• Optimize Sabatier/TSAC pressure control logic and operating limits for 

transitions between Process and Standby that are based on TSAC delivery 

pressure. 

• Develop protocols for leak checking components in their operating environment 

so that so that non-operating conditions (temperature or pressure) do not mask the 

detection of leakage. 

85
5 Appendices 

Calculations 

This section details the calculations used to evaluate the performance of the subsystems during 

the Integrated Test Program. 

Raw Data – Sensor for Mechanical test only in green, for TSAC test only in red, for both tests in 

black. 

Tag Name Units 

CDPGas124 4BMS Inlet Air CO2 Concentration %CO2 

CDPGas125 4BMS Outlet Air CO2 Concentration %CO2 

AFCGas126 Lab Air CO2 Concentration %CO2 

CDPDP_120 4BMS Inlet Air Dewpoint F 

CDPDP_121 4BMS Outlet Air Dewpoint F 

AFcDP_120 Lab Air Dewpoint F 

CDPTmp120 4BMS Inlet Air Temperature F 

CDPTmp121 4BMS Outlet Air Temperature F 

AFcTmp120 Lab Air Temp. Middle F 

CDPmt13 5A Bed 308 Heater Temp A F 

CDPmt14 5A Bed 308 Heater Temp B 

CDPmt16 5A Bed 309 Heater Temp A F 

MSAFlw022 Lab CO2 Inject Flowrate SLPM 

CDPMpde 4BMS Operating Mode 

0OF 1SH 2A1 3A2 4A3 5B1 6B2 7B3 8WP 

CDPmw12 5A Bed 308 Primary Heater Power Watt 

CDPmw13 5A Bed 309 Primary Heater Power Watt 

CDPmw14 5A Bed 308 Secondary Heater Power Watt 

CDPmw15 5A Bed 309 Secondary Heater Power Watt 

CDPFlw121 4BMS Inlet Air Flowrate (TSI Meter) SCFM 

CDPTmp086 4BMS Precool Inlet H2O Temp F 

CDPFlw080 4BMS Precooler Inlet H2O Flow GPM 

CDPPrs120 4BMS Inlet Air Pressure PSIA 

CDPPrs122 4BMS Outlet Air Pressure PSIA 

CDPDP_023 Dessicant Bed Outlet Air Dewpt F 

MSAMas020 Facility CO2 Tank Weight Lbs 

CDPPrs021 Fac Vacuum Tank Air Inlet Pressure Torr 

CDPPrs023 

CDPPrs022 Fac Vacuum Tank Air Pressure Torr 

CDPPrs024 

CDPmt11 Desiccant Bed Outlet Temperature F 

THCFlw120 THC CHX Outlet Air Flowrate SCFM 

VenFlw120 

CDPPrs123 Sorbent bed 308 pressure PSIA 

CDPTmp125 Desiccant bed 104 Outlet Air Temp F 

CDPFlw120 4BMS Inlet Air Flowrate (Sierra Meter) SCFM 

CDPFacClk 4BMS cycle Elapsed Time 

CDPmdns 4BMS Day/Night Status 

AfcPrs120 Lab Pressure PSIA 

MSAFlw023 Lab High CO2 Inject Flowrate LBS/HR 

CDPPrs121 Precooler Outlet to Ambient PSIA 

CDPTemp133 Precooler Inlet Air Temp Deg F 

MSA3WV020 0 is Inlet 1 is THC 

CDPmp12 Pump Inlet Air Pressure PSIA 

CDPVlt120 2-Stage Pump (Air Save) Voltage Volts 

CDPCur120 2-Stage Pump (Air Save) Current Amps 

CDPmp10 Blower Delta Pressure In H2O 

CDPmz16 

CDPTmp640 

86
Tag Name Units 

CDPSpr003 

MEDDP_020 Mechanical Compressor Outlet Dewpoint F 

MEDFlw020 Compressor Outlet Flow after DP lb/hr 

MEDPrs020 Compressor Inlet Pressure PSIA 

MEDTmp020 Manifold Outlet or Crankcase HX inlet F 

MEDTmp021 Crankcase HX Outlet or CP HX inlet F 

MEDTmp022 Manifold Inlet F 

MEDTmp023 Cold Plate Outlet F 

MEDTmp024 Crankcase External Motor End F 

MEDTmp025 Lower Guide Cylinder Stage 1 Motor End F 

MEDTmp026 Crossover Head Stage 1 Motor End F 

MEDTmp027 Crossover Head Stage 2 F 

SEDCO2 cmd Sabatier CO2 Command SLPM 

MEDFlw021 Sabatier CO2 Flow SLPM 

SEDMFM006 

SEDCompressor Compressor command 1=on 0=off 

TSAF prod TSAC outlet CO2 flowrate Sccm 

TSAP1 Bed A Internal pressure Torr 

TSAP2 Bed B internal pressure Torr 

TSAExtWalA Bed A External Wall Temperature C 

TSAHA1 Bed A Heater 1 Temperature C 

TSAHA3 Bed A Heater 3 Temperature C 

TSATouchA Bed A Touch Temperature C 

TSAExtWalB Bed B External Wall Temperature C 

TSATouchB Bed B Touch Temperature C 

TSAHB1 Bed B Heater 1 Temperature C 

TSAHB3 Bed B Heater 3 Temperature C 

TSAPower Heater power for Bed A and Bed B Watts 

TSAF cdra TSAC Inlet CO2 flowrate Sccm 

TSAAirInA Bed A Cooling Air Inlet Temperature C 

TSAAirInB Bed b Cooling Air Outlet Temperature C 

TSAAirOutA Bed A Cooling Air Inlet Temperature C 

TSAAirOutB Bed A Cooling Air Outlet Temperature C 

TSAP cdra Inlet pressure Torr 

SEDP106 H2 Inlet pressure Psia 

SEDH2_SP_ent OGA H2 setpoint 

SEDP002 CDRA pressure psia 

SEDCRA READY Status 1=on 0=off 

SEDCurrent Current from OGA 0-4095 counts 0-100 Amps 

SEDDP405 Reactor Delta Pressure PSID 

SEDDP409 Separator Delta Pressure "H2O 

PSID 

SEDEOGAREADY Ethernet write 1=on 0=off 

SEDH2 cmd SLPM 

SEDHtr A 1=on 0=off (Y20) 

SEDHtr B 1=on 0=off (Y21) 

SEDMas020 Sabatier EDU Water Grams 

SEDMFC H2 Mass Flow SLPM 

SEDMolar User selected molar ratio 

SEDOGA READY Status 1=on 0=off 

SEDP000 Compressor suction Pressure PSIA 

CDRA Pressure 

MEDPrs021 Accumulator Pressure or CO2 inlet PSIA 

SEDP006 Reactor inlet pressure PSIA 

SEDP206 Nitrogen inlet pressure PSIA 

SEDP304 Product water pressure PSIA 

SEDP601 Reactor outlet pressure PSIA 

SEDProcess Process Mode (C102) 

SEDPUMP301 Water pump 1=on 0=off 

SEDSEP_run 

SEDPurge Purge Mode 

SEDstby_purge 

SEDReactCool 501 Cooling Air Valve 1=closed 0=open 

SEDSVO501 

SEDShutdown Shutdown Mode 

SEDStandby Standby Mode 

87
Tag Name Units 

SEDStop Stop Mode 

SEDASD 

SEDT CHXout A Heat Exchanger Outlet Temperature degF 

SEDT407-1 

SEDT CHXout B Heat Exchanger Outlet Temperature degF 

SEDT407-2 

SEDT React A Reactor Hot Zone degF 

SEDT403_1 Reacto Temperature 1 

SEDT React B Reactor Hot Zone degF 

SEDT403_2 Reacto Temperature 2 

SEDT React C Reactor Inlet degF 

SEDT403_3 Reacto Temperature 3 

SEDT React D Reactor Inlet degF 

SEDT403_4 Reacto Temperature 4 

SEDT React Out Reactor Outlet degF 

SEDT404_1 

CDPSV_160 Vacuum Solenoid 

CDPSV_640 (0 Closed 1 Open) TSAC 

CDPSV_641 (0 Closed 1 Open) Space Vacuum 

CDPSV_642 (0 Closed 1 Open) MPC 

CDPmz16 Valve Pos. 209 (T = Ener. = B Pos.) Volt 

CDPTmp640 Re-positional Instr. Cluster Temp F 

CDPSpr003 Sabatier Inlet Hydrogen Flowrate SLPM 

SEDFCV003_cmd CO2 flow command SLPM 

SEDsep_spd Separator speed Rpm 

SEDfan Cooling fan status 

SEDMFC103_cmd H2 flow command 

SEDH402_1 Heater status 

SEDsep_curr Separator current Amps 

SEDMas020 Sabatier EDU Water Grams 

SEDMFC103 Actual hydrogen flow SLPM 

SEDmolar_ratio User selected molar ration 

 

88
Calculated Data for Mechanical Compressor Test 

Name Units Calculation 

Time Hours (current time – initial time) *24 

FMG62 4BMS Inlet Air mmHg (inlet air CO2 concentration/100 * inlet air pressure) *760/14.7 

CO2 Pressure

CO2 in lb/hr (inlet CO2 pressure/air pressure) * (flow*60) * 14.7*144 *44 / (R * (T+460)) 

FFG69 4BMS Outlet Air (outlet air CO2 concentration/100 * inlet air pressure) *760/14.7 

CO2 Pressure 

mmHg 

CO2 out lb/hr (outlet CO2 pressure/air pressure) * (flow*60) * 14.7*144 *44 / (R * (T+460)) 

4BMS CO2 Removal CO2 rate in – CO2 rate out 

Rate 

lb/hr 

FMG10 Lab Air CO2 (lab air CO2 concentration/100 * inlet air pressure) *760/14.7 

Pressure 

mmHg 

4BMS CO2 Removal 1-CO2 out/CO2 in 

Fraction 

Total Heater Power Watts Sum of 4 heaters, bed 308, 309 primary and secondary 

Total Watts Sum of 4 heaters plus air save pump power 

FMD13 Desiccant bed Dew point converted to saturation pressure 

outlet 

mmHg 

H2O lost lb/min Air flow rate * sat pressure * 18 * 14.7 * 144 / (760 * R * (T +460)) 

Air-Save Pump Power, Watts Pump voltage * current (> 0) 

CO2 Injection scfm CO2 injection (slpm) * 0.035315 

Flow Rate from CO2 (CO2 injection flow * (1- outlet CO2 %))/((inlet – outlet CO2%)/100) 

injection 

Scfm 

CDPmp12 Pump Inlet Air Pump inlet air pressure / 2 

Pressure corrected 

torr 

CDPPrs123 Sorbent bed Bed 308 pressure psi * 760 / 14.7 

308 pressure 

torr 

CDPmp12 Pump Inlet Air Pump inlet pressure psi *760 / 14.7 

Pressure 

torr 

CDPDP_023 Dessicant Dewpoint degrees F converted to C 

Bed Outlet Air Dewpt 

C 

CDPDP_120 4BMS Inlet Dewpoint degrees F converted to C 

Air Dewpoint 

C 

CDPTmp120 4BMS Inlet Dewpoint degrees F converted to C 

Air Temperature 

C 

CRA Ready (11=on CRA ready status + 10 

10=off) 

OGA Current/10 SEDH2_SP_ent / 10 

TSAC Power/10 TSAPower / 10 

OGA Ready (9=on 8=off) OGA ready status + 8 

Compressor Status Compressor status + 12 

(13=on 12=off) 

Calc MR from Actual Corrected H2 flow / Sabatier CO2 flow 

Flow 

H2 Rate adjusted, Recorded data * slope + offset 

(@0°C) 

SLPM 

Calc H2O Prod @ 100% H2 flow/ 22.4 / 2 * 18 * timestep + previous summed value 

Eff 

gram 

Calc H2O Prod @ 90% Calculated 100% efficient water * 0.9 

Eff 

gram 

Calc H2O Prod @ 80% Calculated 100% efficient water * 0.8 

Eff 

gram 

H2O Prod Efficiency Actual water produced / calculated 100% efficient water * 100 

(valid with W/D calc) 

% 

H2O Production grams Current mass water (scale) – initial mass water 

H2 Useage Rate Liters H2 flow * timestep + previous summed value 

Day/Night Status (7=day, Day night status + 6 

6=night) 

Desired CO2 Flow (SLPM) H2 flow / selected molar ratio 

Starvation (Standby =1 when OGA ready is true and Sabatier is standby 

when OGA Ready) 

4BMS CO2 Dump in A2 =1 if 4BMS mode is 3 and pump inlet pressure > 11.5 

(mp12>7.95 and 

segment=A2) 

89
Name Units Calculation 

4BMS CO2 Dump in A2 

(mp12>7.95 and 

segment=B2) 

=1 if 4BMS mode = 6 and pump inlet pressure > 11.5 

CEDU Cycle Counter 

(flag step changes) 

Checks for change in CEDU status from one time step to next 

Water Dump Event Checks for water mass change > 17 grams from one time step to next 

Subsystem Efficiency Calculations 

4BMS 

4BMS CO2 Removal Rate (lb/hr) = CO2 Inlet (lb/hr) – CO2 Outlet (lb/hr) 

4BMS CO2 Removal Efficiency = 1- CO2 Inlet (lb/hr)/CO2 Outlet (lb/hr) 

Sabatier 

H2 Usage = Average H2 Flow * Total time of test 

Theoretical Water Production Rate = H2 Usage / 22.4 / 2 * 18 

Actual Water Production Rate = Scale reading at end of test – scale reading at beginning of test 

Sabatier Water Recovery Efficiency = Actual Water Production / Theoretical Water Production *100 

90
5.2 Appendix Data Plots 

5.2 ................................................................................................................................................................ 5-1 Appendix Data Plots

5.2.1 ...................................................................................................................................................................... 5-6 Introduction

5.2.2 ......................................................................................................................................................... 16 4BMS Baseline Case

5.2.3 ...................................................................................................................................... 28 Additional 4BMS Baseline Case

5.2.4 ...................................................................................................................... 31 Mechanical Compressor Stand Alone Case

5.2.5 ............................................................................................................................................. 40 4BMS/CEDU Baseline Case5.2.6 ................................................................................................................................... 48 Sabatier Standalone Baseline Case

5.2.7 .................................................................................................................. 67 4BMS/CEDU/Sabatier Fully Integrated Case

5.2.8 ................................................................................................................... 81 4BMS/TSAC/Sabatier Fully Integrated Case

Figure 1 - Detailed Schematic of 4BMS with sensor locations identified. .............................................................................................. 5-7 

Figure 2 - Detailed Schematic of Sabatier EDU used in Mechanical Compressor Test with sensor locations identified. ..................... 5-8 

Figure 3 - Schematic of Integrated Test with Mechanical Compressor with sensor locations identified. .............................................. 5-9 

Figure 4 - Schematic of Sabatier EDU used with TSAC testing with sensor locations identified. ....................................................... 5-10 

Figure 5 - Schematic of Integrated Test with TSAC with sensor locations indentified. ....................................................................... 5-11 Table 1 – Sensors in the 4BMS ................................................................................................................................................................. 12 Table 2 - Sensors in the Sabatier EDU ..................................................................................................................................................... 13 Table 3 - Sensors in the Mechanical Compressor .................................................................................................................................... 14 Table 4 - Sensors in the Temperature Swing Adsorption Compressor ..................................................................................................... 14

5.2.1 Introduction This document describes the test data collected from the integrated test program. Data was collected from all of the operating systems. Different data sets are plotted for different combinations of systems. The following graphs are representative data sets from the 

different cases that were run. 

91
CO

P 

T 

D P

2

Cabin

Atmosphere

CO 2 VENT

P 

T 

T 

RESIDUAL AIR RETURN LINE

CHECKVALVE 

DESICCANT OUTLET VALVE 

DESICCANT BED 

INLET AIRSELECTORVALVE

GEL 

SILICA

s 

T 

s 

T 

s 

T 

s 

T 

P 

BLOWER

P 

T 

ACCUMULATOR 

CO 2 

P 2 CO 

PUMP

COSELECTORVALVE 

2 

CO SORBENT BED 2 

ELECTRICALHEATER 

HX

T 

PRE-COOLER WATER

T 

S 

T 

CO SORBENT BED 2 

T 

P 

T 

TO VACUUM

S 

P 

S T 

AIR INLET 

POIST FOUR BED MOLECULAR SIEVE

P = PRESSURE SENSOR 

D P = DEW POINT SENSOR

T = TEMPERATURE SENSOR

S = SAMPLE PORT 

= SELECTOR VALVE = CARBON DIOXIDE SENSOR

308 

309 

DP

D P

CO2

CO2

CO2

AIR RETURN

DESICCANT BED 

CDPGas124

CDPGas125

AFcGas126

CDPDP_120

CDPDP_121,122

AFcDP_120

CDPTmp120

T 

CDPTmp121

AFcTmp120

CDPTmp086

P 

CDPPrs120

AFcPrs120

CDPDP_023

CDPmt11

CDPPrs123

CDPTmp125

CDPmt12

MSAFlw022 Lab CO2 Injection Flowrate

CDPPrs022 Vacm Tnk Inlet Press

CDPPrs023 Vacm Tnk Press

MSAMas020 CO2 Tank Weight

CO2 Injection

MSAFlw023 Lab CO2 Injection Flowrate

Cycle Info

CDPmdns Day/Night StatusCDPfcdck Cycle Elapsd Time

Process Air Flowrate

CDPFlw120 Inlet Air Flowrate (Sierra)

CDPFlw121 Inlet Air Flowrate (TSI)

Pre Cooler Water Flowrate

CDPFlw080 Pre Cooler Water Flowrate

Component Power

CDPmw10 Vacuum Pump PowerCDPmw12 308 Bed Primary Heater PowerCDPmw13 309 Bed Primary Heater Power

CDPmw14 308 Bed Secondary Heater PowerCDPmw15 309 Bed Secondary Heater Power

P 

T 

CDPTmp087

CDPTmp127

CDPTmp128

CDPTmp130

CDPTmp129

CDPmt-13,14,15

CDPmt 16, 17, 18

CDPmp10

CDPmp11

516 514

515 513

512

CDPmp12

511

CDPmt92 CDP- mp13

CDPmp14

CDPmt91

F = FLOW METER

F F CDPTmp133 CDPFlw120

517 CDPmz11

CDPmz10

CDPmz12

CDPmz13

CDPmz14

CDPmz16

CDPmz15

F CDPFlw080

CDPFlw121

DP

CDPmt10

P CDPPrs122

CDPPrs121

CDPTmp126

Figure 1 - Detailed Schematic of 4BMS with sensor locations identified. 

92
SABATIER

REACTOR

CONDENSING

HEAT

EXCHANGER

T

P

CG CG CONTROLLER

AND EIB

N2 IN

CO2 IN

H2 IN

CH4 VENT

H2O OUT

LF

CV

MFC

P P

P

T

T

ΔP

MV202

SVO203 CV204 F201

F001

P002 FCV003

CV004

MFM

MFM005 P006

F101

SVC102

MFC103

CV104

R401

H402

T403

DP405

T404

SVO501

FAN502

T407

ST408

DP409

PUMP301

SVC303

P304

P601

RV602 SVO604

RV603 SVO605

BPR606

SVO608

FR607

CG411 CG412

P206

FR205

HX406 T

T T

RV410

SVC007

P

T

ΔP

MV609

Sabatier Engineering Development Unit

SVL18383

MV105

6/25/04

CV305

F406

SABATIER

REACTOR

CONDENSING

HEAT

EXCHANGER

T

P

CG CG CONTROLLER

AND EIB

N2 IN

CO2 IN

H2 IN

CH4 VENT

H2O OUT

LF

CV

MFC

P P

P

T

T

ΔP

MV202

SVO203 CV204 F201

F001

P002 FCV003

CV004

MFM

MFM005 P006

F101

SVC102

MFC103

CV104

R401

H402

T403

DP405

T404

SVO501

FAN502

T407

ST408

DP409

PUMP301

SVC303

P304

P601

RV602 SVO604

RV603 SVO605

BPR606

SVO608

FR607

CG411 CG412

P206

FR205

HX406 T

T T

RV410

SVC007

P

T

ΔP

MV609

Sabatier Engineering Development Unit

SVL18383

MV105

6/25/04

CV305

F406

Figure 2 - Detailed Schematic of Sabatier EDU used in Mechanical Compressor Test with sensor locations identified. 

93
CDRA

To Vacuum

V209 Air Save V200

LMS

Space VacuumSimulator

PT

TP1

V2

V3

Accum

FacilityVent

Dew Point

HV1

HV2

BPRV1

FM1

TP2

HV3

CO2Bottle

SabEDU

HV4

BPRV2

SVC007

PT P002

N2

H2O productto weight scale

Vacuum vent

RV@150 psia

HV5

PG

VenturiVacVent

H2Bottle/regulator

H2Bottle/regulator

CO2

Coolant in/out

HV6

FM2

P000

CDRA

To Vacuum

V209 Air Save V200

LMS

Space VacuumSimulator

PT

TP1

V2

V3

Accum

FacilityVent

Dew Point

HV1

HV2

BPRV1

FM1

TP2

HV3

CO2Bottle

SabEDU

HV4

BPRV2

SVC007

PT P002

N2

H2O productto weight scale

Vacuum vent

RV@150 psia

HV5

PG

VenturiVacVent

H2Bottle/regulator

H2Bottle/regulator

CO2

Coolant in/out

HV6

FM2

P000

Figure 3 - Schematic of Integrated Test with Mechanical Compressor with sensor locations identified. 

94
SABATIER

REACTOR

CONDENSING

HEAT

EXCHANGER

T

P

CG CG CONTROLLER

AND EIB

N2 IN

CO2 IN

H2 IN

CH4 VENT

H2O OUT

MFC

P P

P

MFM

T

ΔP

MV202

SVO203 CV204 F201

F001

P002

FCV003

CV004

MFM005 P006-1

F101 SVC102

MFC103

CV104

R401

H402

T403-1,-8

DP405

T404-1,-2

SVO501

FAN502

T407-1,-2

DP409-1,-2

CV305

P304

P601

SVO604

BPR606

SVO608

CG411 CG412

P206

FR205

HX406

T

SVC007

P

ΔP

MV105

ΔP

DRUM

SEPARATOR AND

PUMP L

SVC303

T T

COLD PLATE

COOLANT

IN/OUT

T

P106

P

P006-2

Manual Fill Port

RV207

RV009

RV107

P

L602

CP301

T413-1,-2

SEP411

FR607

T T T T T T T T

N

N414 T

T T410-1,-2

Gas

Sample

Port

BED412

Gas

Sample

Port

SABATIER

REACTOR

CONDENSING

HEAT

EXCHANGER

T

P

CG CG CONTROLLER

AND EIB

N2 IN

CO2 IN

H2 IN

CH4 VENT

H2O OUT

MFC

P P

P

MFM

T

ΔP

MV202

SVO203 CV204 F201

F001

P002

FCV003

CV004

MFM005 P006-1

F101 SVC102

MFC103

CV104

R401

H402

T403-1,-8

DP405

T404-1,-2

SVO501

FAN502

T407-1,-2

DP409-1,-2

CV305

P304

P601

SVO604

BPR606

SVO608

CG411 CG412

P206

FR205

HX406

T

SVC007

P

ΔP

MV105

ΔP

DRUM

SEPARATOR AND

PUMP L

SVC303

T T

COLD PLATE

COOLANT

IN/OUT

T

P106

P

P006-2

Manual Fill Port

RV207

RV009

RV107

P

L602

CP301

T413-1,-2

SEP411

FR607

T T T T T T T T

N

N414 T

T T410-1,-2

Gas

Sample

Port

BED412

Gas

Sample

Port

Figure 4 - Schematic of Sabatier EDU used with TSAC testing with sensor locations identified. 

95
CDRA

To Vacuum

V209 Air Save V200

LMS

Space VacuumSimulator

V2

FacilityVent

SabEDU

N2

H2O productto weight scale

Vacuum vent

PG

VenturiVacVent

H2Bottle/regulator

H2Bottle/regulator

CO2 inlet

TSAC

CDRA

To Vacuum

V209 Air Save V200

LMS

Space VacuumSimulator

V2

FacilityVent

SabEDU

N2

H2O productto weight scale

Vacuum vent

PG

VenturiVacVent

H2Bottle/regulator

H2Bottle/regulator

CO2 inlet

TSAC

Figure 5 - Schematic of Integrated Test with TSAC with sensor locations indentified.

96
Table 1 – Sensors in the 4BMS Sensor 

Designation 

Sensor Description 

Sensor Designation 

Sensor Description 

CDPTmp126 Port 514 Internal Desiccant Bed 1 

Temp. CDPDP_023 Dessicant Bed Outlet Air Dewpt CDPTmp127 Port 515 Internal Desiccant Bed 1 Temp. 

CDPDP_120 4BMS Inlet Air Dewpoint CDPFlw080 4BMS Precooler Inlet H2O Flow 

CDPTmp128 Port 516 (mt98) Desiccant Bed 1 CDPFlw120 4BMS Inlet Air Flowrate (Sierra) CDPTmp129 Port 503 Sorbent Bed Internal Temp. CDPFlw121 4BMS Inlet Air Flowrate (TSI) CDPTmp130 Port 504 Sorbent Bed Internal Temp. CDPmw12 5A Bed 308 Prim. Heater Power CDPTmp133 Precooler Inlet Air Temp CDPmw13 5A Bed 309 Prim. Heater Power MSAFT_022 Total CO2 Added L CDPmw14 5A Bed 308 Sec. Heater Power MSAFT_023 Totalize CDPFlw023 CDPmw15 5A Bed 309 Sec. Heater Power AFcDP_120 Lab Air Dewpoint (1) CDPPrs021 Fac Vacuum Tank CO2 Inlet Pressure CDPPrs020 feedback delta pressure CDPPrs022 Fac Vacuum Tank CO2 Pressure CDPTmp020 Space Simulator Tank In CDPPrs120 4BMS Inlet Air Pressure THCTmp084 THC HX Chill In CDPPrs121 Precooler Outlet to Ambient THCTmp085 THC HX Chill Out CDPPrs122 4BMS Outlet Air Pressure THCTmp120 THC CHX Inlet Air Temp. CDPTmp086 4BMS Precooler Inlet H2O Temp THCTmp121 THC CHX Outlet Air Temp. CDPTmp120 4BMS Inlet Air Temp. AFcPrs120 Module Pressure (1) MSAFlw022 Lab Low CO2 Inject Flowrate AFcTmp120 Lab Air Temp. Middle (1) MSAFlw023 Lab High CO2 Inject Flowrate AFcTmp121 CABIN FRONT TEMP (1) MSAMas020 Facility CO2 Tank Weight AFcTmp122 CABIN BACK TEMP (1) THCFlw120 THC CHX Outlet Air Flowrate HB_Prs220 High Bay Pressure (1) CDPTmp121 4BMS Outlet Air Temp. HB_Tmp220 High Bay Temp. (1) AFcTmp120 Lab Air Temp. Middle (1) 

CDPCur120 CO2 Pump Current CDPVlt120 CO2 Pump Voltage CDPmp10 Diff. Fan 303 CDPPrs123 Sorbent bed 308 pressure CDPTmp087 CDRA Chill H2O Out CDPTmp121 4BMS Outlet Air Temp. CDPTmp125 Desiccant bed 104 Outlet Air Temp 

97
Sensor Designation Sensor Description Table 2 - Sensors in the Sabatier EDU 

Sensor Designation Sensor Description SEDPUMP301 Water pump 1=on 0=off (Y22) 

SEDPurge Purge Mode (C104) SEDCO2_cmd_003 CO2 Command 0-4095 counts Cooling Air Valve 1=closed 

0=open (Y31) SEDCO2_Flow_005 CO2 Mass Flow (V1414) SEDReactCool_501 Compressor command 1=on 

0=off (Y24) SEDCompressor 

SEDShutdown Shutdown Mode (C100) SEDStandby Standby Mode (C101) SEDCRA READY CRA Status 1=on 0=off (Y23) SEDStop Stop Mode (C103) SEDCRAREADY CRA Status 1=on 0=off (C131)3 Heat Exchanger Outlet 

Temperature (V1435) SEDCurrent f OGA 0-4095 counts 0-100 Amps (V1551) SEDT CHXout_A Heat Exchanger Outlet Temperature (V1436) SEDDP405 Reactor Delta Pressure (V1400) SEDT CHXout_B SEDDP409 Separator Delta Pressure (V1401) SEDT React_A Reactor Hot Zone (V1430) SEDEOGAREADY Ethernet write 1=on 0=off (C135) SEDT React_B Reactor Hot Zone (V1431) H2 Command 0-4095 counts 

(V1420) SEDH2_cmd_103 SEDT React_C Reactor Inlet (V1432) SEDT React_D Reactor Inlet (V1433) SEDHtr_A Heater A 1=on 0=off (Y20) SEDT React_Out Reactor Outlet (V1434) SEDHtr_B Heater B 1=on 0=off (Y21) Product water weight scale SEDMas020 Sabatier EDU Water 

SEDMFC_103_data H2 Mass Flow (V1415) SEDMolar ratio__ User selected molar ratio (V1660) SEDOGA READY OGA Status 1=on 0=off (X104) SEDOGAREADY OGA Status 1=on 0=off (C130) 

Compressor suction Pressure (V1554) SEDP000 Accumulator Pressure or CO2 inlet (V1402) SEDP002 

SEDP006 Reactor inlet pressure (V1403) SEDP206 Nitrogen inlet pressure (V1404) SEDP304 Product water pressure (V1405) SEDP601 Reactor outlet pressure (V1406) SEDProcess Process Mode (C102) 

98
Table 3 - Sensors in the Mechanical Compressor 

Sensor Designation Sensor Description MEDDP_020 Mechanical Compressor 

Outlet Dewpoint, F 

MEDFlw020 Compressor Outlet Flow 

after DP, lb/hr 

MEDPrs020 Compressor Inlet Pressure, 

PSIG 

MEDTmp020 Manifold Outlet or 

Crankcase HX inlet, F 

MEDTmp021 Crankcase HX Outlet or CP 

HX inlet, F 

MEDTmp022 Manifold Inlet, F MEDTmp023 Cold Plate Outlet, F MEDTmp024 Crankcase External Motor 

End, F 

MEDTmp025 Lower Guide Cylinder 

Stage 1 Motor End, F 

MEDTmp026 Crossover Head Stage 1 

Motor End, F 

MEDTmp027 Crossover Head Stage 2, F 

Table 4 - Sensors in the Temperature Swing Adsorption Compressor TSAF prod TSAC outlet CO2 flowrate TSAP1 Bed A Internal pressure TSAP2 Bed B internal pressure TSAExtWalA Bed A External Wall 

Temperature 

TSAHA1 Bed A Heater 1 

Temperature 

TSAHA3 Bed A Heater 3 

Temperature 

TSATouchA Bed A Touch Temperature TSAExtWalB Bed B External Wall 

Temperature 

TSATouchB Bed B Touch Temperature TSAHB1 Bed B Heater 1 

Temperature 

TSAHB3 Bed B Heater 3 

Temperature 

TSAPower Heater power for Bed A 

and Bed B 

TSAF cdra TSAC Inlet CO2 flowrate TSAAirInA Bed A Cooling Air Inlet 

Temperature 

TSAAirInB Bed b Cooling Air Outlet 

Temperature 

TSAAirOutA Bed A Cooling Air Inlet 

Temperature 

TSAAirOutB Bed A Cooling Air Outlet 

Temperature 

TSAP cdra Inlet pressure 

99
4BMS Baseline Case Test Day 58 6/27/05 Page 11 

Additional 4BMS Case Test Day 17 2/6/05 Page 23 Mechanical Compressor Stand Alone Case Test Day 4 11/2/04 Page 27 4BMS/CEDU Baseline Case Test Day 9 12/1/04 Page 36 Sabatier Standalone Case Test Day 16 2/4/05 Page 44 4BMS/TSAC Baseline Case 11/20/05 Page 57 4BMS/CEDU/Sabatier Fully Integrated Case Test Day 16 2/4/05 Page 63 4BMS/TSAC/Sabatier Fully Integrated Case 1/27/06 Page 77 

100
5.2.2 4BMS Baseline Case 

POIST 4BMS/Compressor EDU Testing - 4BMS B/L with TP1 Conditions - Elapsed Time from 6/27 -- Test 

Day 58 2005 

Plot 1 -- Status for 4BMS, CRA, OGA and Compressor (offset for clarity)

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Time, Hours

status

CDPMpde 0OF 1SH 2A1 3A2 4A3 5B1 6B2 7B3 8WP CRA Ready (11=on 10=off)OGA Ready (9=on 8=off) Compressor Status (13=on 12=off)

This plot gives the status of each of the operating systems against a timeline. For this case, only the 4BMS is operating. The integer values correspond to the different processing cycles of the 4BMS. 0=Off, 1=SH??, 2=Bed A Air Save, 3=Bed A Desorb, 4=Bed A Vacuum Vent, 5=Bed B Air Save, 6=Bed B Desorb, 7=Bed B Vacuum Vent. The compressor and Sabatier are both off. 

101
Plot 2 -- Carbon Dioxide Partial Pressures at 4BMS Inlet, 4BMS Outlet, and in Lab 

Module Simulator

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Time, Hours

mmHg

FMG62 4BMS Inlet Air CO2 Pressure mmHg FFG69 4BMS Outlet Air CO2 Pressure mmHg FMG10 Lab Air CO2 Pressure mmHg

This plot shows the CO2 concentration in and out of the 4BMS. The outlet concentration spikes every time the beds switch because 

there is residual CO2 in the lines from the desorbing bed that goes to the 4BMS outlet once that desorbing bed comes on-line and air starts flowing through it again. 

102
Plot 3 -- Air Dewpoint at 4BMS Inlet, 4BMS Outlet, and in Lab Module Simulator

-10-20-30-40

0

605040302010

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Time, Hours

Temperature, degrees F

CDPDP_120 4BMS Inlet Air Dew point #1 F CDPDP_121 4BMS Outlet Air Dew point #1 F AFcDP_120 Lab Air Dew point F 

This plot shows the dew point of the air entering the 4BMS and the bulk air in the Lab Module simulator. The outlet dew point sensor 

was not working during the test. 

103
Plot 4 -- Air Temperature at 4BMS Inlet, 4BMS Outlet, in Lab Module Simulator, and 

Water Temperature at Precooler Inlet

0

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0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Time, Hours

Temperature, degrees F

CDPTmp120 4BMS Inlet Air Temperature F CDPTmp121 4BMS Outlet Air Temperature F AFcTmp120 Lab Air Temp. Middle F CDPTmp086 4BMS Precool Inlet H2O Temp #1 F

This plot shows air temperatures throughout the 4BMS. At the start of a bed change (at 25.5 hours above) the previously desorbed bed that is still hot becomes the adsorbing bed. The air flowing through the bed picks up the heat from the bed, topping out at about 130 F. This hot air then flows through the spent desiccant bed and regenerates it by picking up the water and returning it to the cabin. 

104
Plot 5 -- Sorbent Bed Heater Temperatures

0

50

450400350300250200150100

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Time, Hours

Temperature, degrees F

CDPmt13 5A Bed 308 Heater Temp A F CDPmt16 5A Bed 309 Heater Temp A F 

This plot shows the temperatures of the molecular sieve beds. The desorbing bed heaters are fully on until the temperature reaches 400 

F and then an ON/OFF control is used to maintain the temperature at 400 until the end of the cycle. 

105
Plot 6 -- Desiccant Bed Inlet and Outlet Air Temperatures

0

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0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Time, Hours

Temperature, degrees F

CDPTmp120 4BMS Inlet Air Temperature F CDPmt11 Desiccant Bed Outlet Temperature F 

This plot shows the temperatures of the desiccant bed. The air leaving the desiccant is warmed by the heat of adsorption of water onto the desiccant material. 

106
Plot 7 -- Desiccant Bed Outlet Air Dewpoint Temperature

-10-20-30-40

0

40302010

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Time, Hours

Temperature, degrees F

CDPDP_023 Dessicant Bed Outlet Air Dew pt F 

This plot shows how the dew point of the air leaving the desiccant and entering the molecular sieve bed remains very dry. Water will contaminate the molecular sieve and require high temperature regeneration. The spikes in the dew point signal are due to calibrations of the sensor. 

107
Plot 8 -- 4BMS Process Air Flow Rate

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0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Time, Hours

SCFM

CDPFlw 120 4BMS Inlet Air Flow rate SCFM (Sierra) CDPFlw 121 4BMS Inlet Air Flow rate SCFM (TSI) 

Two different air flow instruments were used to monitor the process air flow. 

108
Plot 9 -- 4BMS Vacuum System Pressures

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Time, Hours

PSIA/Torr

CDPPrs123 Sorbent bed 308 pressure PSIA CDPmp12 Pump Inlet Air Pressure PSIACDPPrs021 Fac Vacuum Tank Air Inlet Pressure Torr CDPPrs022 Fac Vacuum Tank Air Pressure Torr 

This plot shows the pressures throughout the 4BMS. The bed pressure (red square wave shown in PSIA) cycles between ambient pressure during adsorption and vacuum during desorption. The vacuum system pressures spike up initially when the bed begins desorbing and then returns to vacuum levels as the CO2 is exhausted from the bed. 

109
Plot 10 -- 4BMS Component Power

0

600500400300200100

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Time, Hours

Watts

CDPmw 12 5A Bed 308 Prim. Heater Pow er Watt CDPmw 13 5A Bed 309 Prim. Heater Pow er Watt CDPmw 14 5A Bed 308 Sec. Heater Pow er Watt CDPmw 15 5A Bed 309 Sec. Heater Pow er Watt Air-Save Pump Pow er, Watts

This plot shows the power summary for the system. The primary and secondary heaters are on full until the bed reaches 400 F andthen cycle to maintain the temperature. The air save pump is activated for 10 minutes of each half cycle. 

110
Plot 11 -- 4BMS CO2 Injection and Coolant Water Flow Rate

0

0.5

1

1.5

2

2.5

3

3.5

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Time, Hours

SLPM/GPM

350300250200150100500

LBS

MSAFlw 022 Lab CO2 Inject Flow rate SLPM CDPFlw 080 4BMS Precooler Inlet H2O Flow GPM MSAFlw 023 Lab High CO2 Inject Flow rate LBS/HR MSAMas020 Facility CO2 Tank Weight Lbs 

This plot shows the CO2 injection rate into the 4BMS. The CO2 injection rate is based on a closed loop algorithm to maintain a constant CO2 concentration at the inlet of the 4BMS as shown in plot 2 and plot 12. The CO2 tank weight is a means of performing a mass balance on CO2 to verify the accuracy of the measurements. 

111
Plot 12 -- Percent Carbon Dioxide at 4BMS Inlet, 4BMS Outlet, and in Lab Module 

Simulator

0

0.5

1

1.5

2

2.5

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Time, Hours

%

CDPGas124 4BMS Inlet Air CO2 Concentration %CO2 CDPGas125 4BMS Outlet Air CO2 Concentration %CO2 AFCGas126 Lab Air CO2 Concentration %CO2 

This plot is the same as Plot 2 except it is reported in % concentration instead of mmHg. 

112
5.2.3 Additional 4BMS Baseline Case 

Another example of 4BMS Baseline test conditions: 

POIST 4BMS/Compressor EDU Testing - 4BMS Baseline - Elapsed Time from 2/6 -- Test Day 17 2005 

Plot 1 -- Status for 4BMS, CRA, OGA and Compressor (offset for clarity)

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Time, Hours

status

CDPMpde 0OF 1SH 2A1 3A2 4A3 5B1 6B2 7B3 8WP CRA Ready (11=on 10=off)OGA Ready (9=on 8=off) Compressor Status (13=on 12=off)

Plot 2 -- Carbon Dioxide Partial Pressures at 4BMS Inlet, 4BMS Outlet, and in Lab 

Module Simulator

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Time, Hours

mmHg

FMG62 4BMS Inlet Air CO2 Pressure mmHg FFG69 4BMS Outlet Air CO2 Pressure mmHg FMG10 Lab Air CO2 Pressure mmHg

Plot 3 -- Air Dewpoint at 4BMS Inlet, 4BMS Outlet, and in Lab Module Simulator

0

605040302010

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Time, Hours

Temperature, degrees F

CDPDP_120 4BMS Inlet Air Dew point #1 F CDPDP_121 4BMS Outlet Air Dew point #1 F 

Plot 4 -- Air Temperature at 4BMS Inlet, 4BMS Outlet, in Lab Module Simulator, and 

Water Temperature at Precooler Inlet

0

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0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Time, Hours

Temperature, degrees F

CDPTmp120 4BMS Inlet Air Temperature F CDPTmp121 4BMS Outlet Air Temperature F AFcTmp120 Lab Air Temp. Middle F CDPTmp086 4BMS Precool Inlet H2O Temp #1 F

113
Plot 6 -- Desiccant Bed Inlet and Outlet Air Temperatures

0

908070605040302010

100

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Time, Hours

Temperature, degrees F

CDPTmp120 4BMS Inlet Air Temperature F CDPmt11 Desiccant Bed Outlet Temperature F 

Plot 5 -- Sorbent Bed Heater Temperatures

0

50

450400350300250200150100

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Time, Hours

Temperature, degrees F

CDPmt13 5A Bed 308 Heater Temp A F CDPmt16 5A Bed 309 Heater Temp A F 

Plot 7 -- Desiccant Bed Outlet Air Dewpoint Temperature

-100

-20-40-60-80

0

4020

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Time, Hours

Temperature, degrees F

CDPDP_023 Dessicant Bed Outlet Air Dew pt F 

Plot 8 -- 4BMS Process Air Flow Rate

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0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Time, Hours

SCFM

CDPFlw 120 4BMS Inlet Air Flow rate SCFM (Sierra) CDPFlw 121 4BMS Inlet Air Flow rate SCFM (TSI) 

114
Plot 10 -- 4BMS Component Power

0

600500400300200100

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Time, Hours

Watts

CDPmw 12 5A Bed 308 Prim. Heater Pow er Watt CDPmw 13 5A Bed 309 Prim. Heater Pow er Watt CDPmw 14 5A Bed 308 Sec. Heater Pow er Watt CDPmw 15 5A Bed 309 Sec. Heater Pow er Watt Air-Save Pump Pow er, Watts

Plot 9 -- 4BMS Vacuum System Pressures

0

80604020

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0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Time, Hours

PSIA/Torr

CDPPrs123 Sorbent bed 308 pressure PSIA CDPmp12 Pump Inlet Air Pressure PSIACDPPrs021 Fac Vacuum Tank Air Inlet Pressure Torr CDPPrs022 Fac Vacuum Tank Air Pressure Torr 

Plot 11 -- 4BMS CO2 Injection and Coolant Water Flow Rate

0

0.5

1

1.5

2

2.5

3

3.5

4

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Time, Hours

SLPM/GPM

342340338336334332330

LBS

MSAFlw 022 Lab CO2 Inject Flow rate SLPM CDPFlw 080 4BMS Precooler Inlet H2O Flow GPM MSAFlw 023 Lab High CO2 Inject Flow rate LBS/HR MSAMas020 Facility CO2 Tank Weight Lbs 

Plot 12 -- Percent Carbon Dioxide at 4BMS Inlet, 4BMS Outlet, and in Lab Module 

Simulator

0

0.5

1

1.5

2

2.5

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Time, Hours

%

CDPGas124 4BMS Inlet Air CO2 Concentration %CO2 CDPGas125 4BMS Outlet Air CO2 Concentration %CO2 AFCGas126 Lab Air CO2 Concentration %CO2 

115
5.2.4 Mechanical Compressor Stand Alone Case 

POIST 4BMS/Compressor EDU Testing – CEDU Baseline - Elapsed Time from 11/22 -- Test Day 4 2004 

Plot 1 -- Status for 4BMS, CRA, OGA and Compressor (offset for clarity)

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Time, Hours

status

CDPMpde 0OF 1SH 2A1 3A2 4A3 5B1 6B2 7B3 8WP CRA Ready (11=on 10=off)OGA Ready (9=on 8=off) Compressor Status (13=on 12=off)

This plot is the same as the status plot for the 4BMS stand alone test. Each line represents the status of each piece of equipment. The 4-bed mol sieve was operated under its normal operating mode, and the compressor was only activated three times. The Sabatier and OGA were not involved in this test. 

116
Plot 2 -- CEDU Overview

-1

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0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Time, Hours

Suction Press 

(PSIA), Flow 

(Lb/hr), On/Off, 

Day/Night

140120100806040200-20

Discharge Press 

(PSIA)

Day/Night Status (7=day, 6=night) SEDCompressor command 1=on 0=offMEDFlw 020 Compressor Outlet Flow after DP lb/hr MEDPrs020 Compressor Inlet Pressure PSIA MEDPrs021 Accumulator Pressure or CO2 inlet PSIA

This plot shows multiple data items on one plot: compressor flow, inlet and outlet pressure and the compressor command. These same data are shown in separate plots following for better clarity. 

117
Plot 3 -- CEDU Outlet Flow Rate, On/Off

-1

-0.5

0

0.5

1

1.5

2

2.5

3

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Time, Hours

lb/hr

210

1=On/ 0=Off

MEDFlw 020 Compressor Outlet Flow after DP lb/hr SEDCompressor command 1=on 0=off

This plot shows the flow rate at the compressor exit. This data, along with the inlet and outlet pressure, is used to verify the flow rate 

model of the compressor. 

118
Plot 4 -- CEDU Inlet Pressure

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Time, Hours

PSIA

210

1=On / 0=Off

MEDPrs020 Compressor Inlet Pressure PSIA SEDCompressor command 1=on 0=off

This plot shows the compressor inlet pressure. The inlet pressure varies as the 4-bed mol sieve is transitioning through its operating modes. 

119
Plot 5 -- CEDU Outlet Dew Point

-20-40

0

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Time, Hours

Temperature, degrees F

210

1 = On / 0 = Off

MEDDP_020 Mechanical Compressor Outlet Dew point F SEDCompressor command 1=on 0=off

This plot shows the outlet dew point of the compressor. The dew point was anticipated to be high enough to cause condensation in the compressor, but as shown in the plot, the dew point remained low throughout the test. 

120
Plot 6 -- CEDU Outlet Pressure

0

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0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Time, Hours

PSIA

210

1 = On / 0 = Off

MEDPrs021 Accumulator Pressure or CO2 inlet PSIA SEDCompressor command 1=on 0=off

This plot shows the compressor discharge pressure. The compressor was tested at varying discharge pressures by incorporating a pressure regulator into the downstream plumbing. 

121
Plot 7 --CEDU Temperatures (1 of 3)

0

908070605040302010

100

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Time, Hours

Temperature, 

degrees F

210

1 = On / 0 = Off

MEDTmp020 Manifold Outlet or Crankcase HX inlet F MEDTmp021 Crankcase HX Outlet or CP HX inlet F SEDCompressor command 1=on 0=off

This plot and the next two show the temperatures at various locations within the compressor. The temperatures are measured in the 

cooling water throughout the compressor. The large temperature increase at 14-15 hours was due to thermocouples being removed from the coolant and not relevant to the specific test results. 

122
Plot 8 -- CEDU Temperatures (2 of 3)

0

908070605040302010

100

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Time, Hours

Temperature, 

degrees F

210

1 = On / 0 = Off

MEDTmp022 Manifold Inlet F MEDTmp023 Cold Plate Outlet F MEDTmp024 Crankcase External Motor End F SEDCompressor command 1=on 0=off

123
Plot 9 -- CEDU Temperatures (3 of 3)

0

80604020

120100

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Time, Hours

Temperature, 

degrees F

210

1 = On / 0 = Off

MEDTmp025 Low er Guide Cylinder Stage 1 Motor End F MEDTmp026 Crossover Head Stage 1 Motor End F MEDTmp027 Crossover Head Stage 2 F SEDCompressor command 1=on 0=off

124
5.2.5 4BMS/CEDU Baseline Case 

POIST 4BMS/Compressor EDU Testing – CEDU/4BMS BL #5 - Elapsed Time from 12/1 -- Test Day 9 2004 

Plot 1 -- Carbon Dioxide Partial Pressures at 4BMS Inlet and 4BMS 

Outlet, and 4BMS, CEDU and SEDU Status

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mmHg

1614121086420

Status

FMG62 4BMS Inlet Air CO2 Pressure mmHg FFG69 4BMS Outlet Air CO2 Pressure mmHg CRA Ready (11=on 10=off) CDPMpde 0OF 1SH 2A1 3A2 4A3 5B1 6B2 7B3 8WPCompressor Status (13=on 12=off)

This plot shows the status of the 4BMS and the compressor and the carbon dioxide concentration into and out of the CO2 removal system. The compressor was operated in the middle part of the day for this test series, as indicated by the purple line changing from 12 

to 13. For this test, the inlet CO2 concentration (indicated by the red line above) was set to 3 mmHg for half of the test and 1.5 mmHg 

for the remainder. 

125
Plot 2 -- CEDU Status

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Suction Press (PSIA), Flow (lb/hr), 

On/Off, Day, Night

140120100806040200

Day/Night Status (7=day, 6=night) SEDCompressor command 1=on 0=offMEDFlw 020 Compressor Outlet Flow after DP lb/hr MEDPrs020 Compressor Inlet Pressure PSIA MEDPrs021 Accumulator Pressure or CO2 inlet PSIA

This plot shows some of the key data for the mechanical compressor. The inlet and outlet pressures are both shown on this plot along 

with flow and the compressor command. The following plot shows the same data on a magnified time scale. 

126
Plot 2 -- CEDU Status

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15 16 17 18

Suction Press (PSIA), Flow (lb/hr), 

On/Off, Day, Night

140120100806040200

Day/Night Status (7=day, 6=night) SEDCompressor command 1=on 0=offMEDFlw 020 Compressor Outlet Flow after DP lb/hr MEDPrs020 Compressor Inlet Pressure PSIA MEDPrs021 Accumulator Pressure or CO2 inlet PSIA

This plot shows the magnified time scale of the previous plot. The light blue line above is the compressor inlet pressure, which is the 

same as the molecular sieve bed pressure as it is being desorbed. The purple line is the accumulator pressure into which the 

compressor is pumping the CO2. The green line shows the mass flow rate of CO2 from the compressor.

127
Plot 3 -- 4BMS Vacuum System Pressures

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Time, Hours

PSIA/Torr

CDPPrs123 Sorbent bed 308 pressure PSIA CDPmp12 Pump Inlet Air Pressure PSIACDPPrs021 Fac Vacuum Tank Air Inlet Pressure Torr CDPPrs022 Fac Vacuum Tank Air Pressure Torr 

This plot summarizes the vacuum system pressures for the integrated test. The vacuum pressures indicate when the 4BMS is venting to vacuum. The plot is shown again with a magnified time line on the next page. 

128
Plot 3 -- 4BMS Vacuum System Pressures

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Time, Hours

PSIA/Torr

CDPPrs123 Sorbent bed 308 pressure PSIA CDPmp12 Pump Inlet Air Pressure PSIACDPPrs021 Fac Vacuum Tank Air Inlet Pressure Torr CDPPrs022 Fac Vacuum Tank Air Pressure Torr 

This plot details the system vacuum pressures in more detail. The red and blue lines are the bed pressure and compressor inlet 

pressure, respectively. The pressures are basically the same during the desorption phase. The green and brown lines are the vacuum 

pressures. The bed is desorbed directly to the space vacuum simulator during the last 10 minutes of the desorption cycle, as indicated 

by the increase in the two vacuum pressures. During integrated testing, there are occasions when the accumulator is full, and the bed 

must therefore desorb to space vacuum instead of activating the compressor.

129
Plot 4 -- CEDU Inet and Outlet Pressures, Outlet Dew Point

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Inlet (PSIA)

140120100806040200-20-40-60

Outlet (PSIA), Dew Point 

(deg F)

MEDPrs020 Compressor Inlet Pressure PSIA MEDPrs021 Accumulator Pressure or CO2 inlet PSIAMEDDP_020 Mechanical Compressor Outlet Dew point F 

This plot again shows the compressor inlet and outlet pressure, and also the dew point of the product CO2. The data shows that the dew point never exceeds 30 F, even at high accumulator pressure. There is, therefore, little risk of condensation in either thecompressor or the accumulator. 

130
Plot 5 -- Sorbent Bed Heater Temperatures

0

50

450400350300250200150100

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Time, Hours

Temperature, degrees F

CDPmt13 5A Bed 308 Heater Temp A F CDPmt16 5A Bed 309 Heater Temp A F 

This plot shows the temperature of the two molecular sieve beds. The heater for the desorbing bed is turned on full power until the bed reaches 400 F. The heater is then cycled to maintain the bed temperature while the CO2 is desorbed. 

131
Plot 6 -- Desiccant Bed Outlet Air Dewpoint Temperature

-100

-20-40-60-80

0

4020

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Time, Hours

Temperature, degrees F

CDPDP_023 Dessicant Bed Outlet Air Dew pt F 

132
5.2.6 Sabatier Standalone Baseline Case 

POIST 4BMS/Compressor EDU Testing – Sabatier Baseline Pt #1 - Elapsed Time from 2/4 -- Test Day 16 2005 

Plot 1 -- Status for 4BMS, CRA, OGA and Compressor (offset for clarity)

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Time, Hours

status

CDPMpde 0OF 1SH 2A1 3A2 4A3 5B1 6B2 7B3 8WP CRA Ready (11=on 10=off)OGA Ready (9=on 8=off) Compressor Status (13=on 12=off)

This plot shows the operating status of the components. In this test, the Sabatier was operated alone. 

133
Plot 2 --SEDU Reactor Cooling Control

0

800600400200

12001000

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Time, Hours

Temperature (F)

1086420

Open/Closed, 

Flow (SLPM)

SEDT React A Reactor Hot Zone degF SEDT React Out Reactor Outlet degFSEDReactCool 501 Cooling Air Valve 1=closed 0=open MEDFlw 021 Sabatier CO2 Flow SLPMH2 Rate adjusted, SLPM (@0°C)

This plot shows the hydrogen and carbon dioxide flow rates along with the temperatures of the reactor. This case was run at full flow, 9 slpm hydrogen and 2.7 slpm CO2, in cyclic operation. The reactant flow is on for about 53 minutes and off for 37 minutes. The hot zone of the reactor peaks out at 1000 F while reactants are flowing and cools down to about 500 F when the flow is stopped. Thereactor outlet flow is below 200 F during the entire run. 

134
Plot 3 -- SEDU Separator Level Control

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Time, Hours

On/Off, Delta Pressure 

(IWC)

16001400120010008006004002000

Weight (grams)

SEDPUMP301 Water pump 1=on 0=off SEDDP409 Separator Delta Pressure"H2O SEDMas020 Sabatier EDU Water Grams

This plot shows the operation of the water collection tank and pump. The data is shown magnified in the next plot. 

135
Plot 3 -- SEDU Separator Level Control

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11 12 13 14

Time, Hours

On/Off, Delta Pressure 

(IWC)

16001400120010008006004002000

Weight (grams)

SEDPUMP301 Water pump 1=on 0=off SEDDP409 Separator Delta Pressure"H2O SEDMas020 Sabatier EDU Water Grams

This plot shows the operation of the water separator in more detail. The saw tooth line is the level in the separator as measured with a differential pressure sensor. When the level reaches a high limit, the pump is activated for about 5 seconds. The data collection for 

these tests was one reading per minute. Many times, the reading did not catch the activation of the pump, which is why only a few 

activations are shown on the graph. The water weight is measured with an electronic scale. The time period around hour 12 with no increase in water weight is a Standby period for the Sabatier system. 

136
Plot 4 -- SEDU System Pressures

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Time, Hours

PSIA

54.543.532.521.510.50

PSID

SEDP006 Reactor inlet pressure PSIA SEDP601 Reactor outlet pressure PSIASEDDP405 Reactor Delta Pressure PSID SEDDP409 Separator Delta Pressure"H2O

This plot shows the pressures throughout the Sabatier system. The maroon, spiked lines are the same separator differential pressure 

reading shown in the previous plot. The red and blue lines are the reactor inlet and outlet pressures, respectively. The reactor is 

evacuated to low pressure (< 2 psia) every time the system transitions to Standby. The green line is the reactor differential pressure. The differential pressure is related to flow rate, and is less than 1 psid at full flow. 

137
Plot 5 -- SEDU System Efficiency

0

500

30002500200015001000

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Time, Hours

Weight (grams), Usage 

(lites)

Calc H2O Prod @ 100% Eff, gram Calc H2O Prod @ 90% Eff, gram Calc H2O Prod @ 80% Eff, gramH2O Production, grams H2 Useage Rate, Liters

This plot shows the Sabatier water production rate plotted with calculated efficiency targets. The efficiency is calculated from the usage rate of hydrogen. This plot shows the efficiency to be about 80%. This plot is a little misleading for efficiency because the water weight is not recorded until the first dump out by the pump, and therefore the inventory of water in the system is not fully accounted. 

138
Plot 6 -- SEDU Molar Ratio

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0 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

Time, Hours

Flow (SLPM @ 0 C)

43.532.521.510.50

Molar Ratio

H2 Rate adjusted, SLPM (@0°C) Calc MR from Actual Flow MEDFlw 021 Sabatier CO2 Flow SLPM

This plot shows the hydrogen and carbon dioxide flows to the Sabatier reactor and the calculated molar ratio. The stoichiometric ratio 

for the reaction is 4 moles hydrogen per mole of carbon dioxide. Since the ISS life support closed loop mass balance is carbon dioxide 

rich, the reactor is controlled to a molar ratio of 3.5 to ensure that all of the available hydrogen is used in the reaction. 

139
Plot 7 -- SEDU CO2 and H2 Flow

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Time, Hours

CO2 Flow (SLPM)

109876543210

H2 Flow (SLPM)

MEDFlw 021 Sabatier CO2 Flow SLPM Desired CO2 Flow (SLPM) SEDMFC H2 Mass Flow SLPM

This plot shows the CO2 and H2 flow feeds to the reactor. In this test, the Sabatier was operated in cyclic mode, therefore the flows are turned on and off for every Process/Standby mode. 

140
Plot 8 -- SEDU Temperatures

0

800600400200

12001000

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Time, Hours

Hot Zone and Inlet Temps

SEDT React A Reactor Hot Zone degF SEDT React B Reactor Hot Zone degF SEDT React C Reactor Inlet degFSEDT React D Reactor Inlet degF SEDT React Out Reactor Outlet degF

This plot details the temperatures in the Sabatier reactor. Temperatures A and B are in the hot zone of the reactor, which is about three inches from the inlet end. Temperatures C and D are closer to the inlet end and intended to be used to detect the presence of air in the inlet CO2 stream. While the reactants are flowing into the reactor, the heat from the reaction is continuously pushed toward the aft end of the reactor bed. When the flows stop (around 11.75 hours, 13.25 hours, 14 hours, etc) the hottest part of the reaction zone starts to cool down, but the inlet end of the reactor immediately starts to heat up due to conduction of heat from the hot zone. The outlet of the 

reactor follows the same cooling trend as the hot zone when the reactants are removed. 

141
Plot 9 -- SEDU Water Production Rate

0

800600400200

1000

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Time, Hours

Rate (gm/hr)

210

Mode

H2O Production, grams SEDStandby Standby Mode SEDProcess Process Mode (C102)

This plot details the water production rate. The water product is recorded on a digital scale, which is incremented every time the 

product water pump turns on to empty the separator. During Standby (when the blue line is 1 and the green line is 0) there is no additional water production, and the red line is flat for the duration. Once Process mode starts again, the water production starts again. 

142
Plot 10 -- SEDU Overview

0

500

200015001000

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Time, Hours

Temperature (F), 

Accum Pressure 

(PSIA)

20151050

Reactor Pressure 

(psia)

SEDT React A Reactor Hot Zone degF SEDT React Out Reactor Outlet degFMEDPrs021 Accumulator Pressure or CO2 inlet PSIA SEDMas020 Sabatier EDU Water GramsSEDP601 Reactor outlet pressure PSIA

This plot is an overview of the Sabatier system operation, and gives analysts a quick glance at the state of the system. The reactor pressure and temperatures show readily that the system is operating in a cyclic mode, since the temperature and pressure are alternating. The water production line shows that the system is operating well, with no major problems. The CO2 accumulator pressure is also listed on this graph. In this test case, the CO2 feed was operated on a fixed 25 psia feed source. For the integrated tests, the CO2 pressure rises and falls and the compressor fills the accumulator and the Sabatier empties it. 

143
Plot 11 -- SEDU Status

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Time, Hours

Status

50403020100

Pressure (psia)

OGA Ready (9=on 8=off) CRA Ready (11=on 10=off)SEDStandby Standby Mode SEDProcess Process Mode (C102)MEDPrs021 Accumulator Pressure or CO2 inlet PSIA

This plot shows the status of some of the systems in the integrated test. The OGA status (off for this stand alone test) is given along with the Sabatier Process or Standby modes. The accumulator pressure is given here as well, which is more informative for the integrated tests. 

144
Plot 12 -- SEDU CO2 Flow Control Accuracy

0

0.5

1

1.5

2

2.5

3

3.5

4

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Time, Hours

Flow (SLPM), 

Reactor Press (psia)

302520151050

Accum Pressure 

(PSIA)

MEDFlw 021 Sabatier CO2 Flow SLPM Desired CO2 Flow (SLPM)MEDPrs021 Accumulator Pressure or CO2 inlet PSIA SEDP006 Reactor inlet pressure PSIA

This plot shows the accuracy of the CO2 flow control. The Sabatier required development of a flow control for space flight use. The Sabatier EDU incorporated a motor drive control valve. This plot shows that the actual flow met the desired flow over the range of inlet pressures used for this test.

145
4BMS/TSAC Baseline Case

POIST 4BMS/TSAC/Sabatier Testing – 4BMS-TSAC Test #4 - Elapsed Time from 11/20/2005 

Plot 1 -- Status for 4BMS and TSAC

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1 2 3 4 5 6 7 8 910 11

Tim e, Hours

status

120010008006004002000-200

sccm

CDPMpde 0OF 1SH 2A1 3A2 4A3 5B1 6B2 7B3 8WP TSAFprod TSAC Outlet CO2 Flow rate sccm

This plot is, again, the familiar status plot, which shows the operating mode of the 4BMS. The TSAC does not have a mode designation data element, but the plot of output flow gives a good indication of the operating state. Each bed is in a “Deliver” state 

when the output flow is constant. 

146
Plot 13 -- TSAC Internal Pressures

0

800600400200

12001000

1 2 3 4 5 6 7 8 910 11

Tim e, Hours

Pressure, torr

TSAP1 Bed A Internal Pressure torr TSAP2 Bed B Internal Pressure torr

This plot shows the pressures of the CO2 product in each of the two TSAC beds. When the beds are desorbing, the pressure is maintained at 1000 torr for the duration of the desorb cycle. 

147
Plot 14 -- TSAC Bed A Tem peratures

0

50

350300250200150100

1 2 3 4 5 6 7 8 910 11

Tim e, Hours

Temperature, °C

TSAHA1 Bed A Heater 1 Temperature C TSAHA3 Bed A Heater 3 Temperature CTSAExtWalA Bed A External Wall Temperature C TSATouchA Bed A Touch Temperature 

This plot shows the temperature profile for Bed “A”. The significance of the curves is explained for plot number 16 which showstemperatures and pressures together. 

148
Plot 15 -- TSAC Bed B Tem peratures

0

50

300250200150100

1 2 3 4 5 6 7 8 910 11

Tim e, Hours

Temperature, °C

TSAHB1 Bed B Heater 1 Temperature C TSAHB3 Bed B Heater 3 Temperature CTSAExtWalB Bed B External Wall Temperature C TSATouchB Bed B Touch Temperature C

This plot shows the temperature profile for Bed “B”. 

149
Plot 16 -- TSAC Bed A Pressures and Tem peratures

0

800600400200

12001000

1 2 3 4 5 6 7 8 9 10 11

Tim e, Hours

Pressure, torr

350300250200150100500

Temperature, °C

TSAP1 Bed A Internal Pressure torr TSAAirInA Bed A Cooling Air Inlet Temperature CTSAAirOutA Bed A Cooling Air Outlet Temperature C TSAExtWalA Bed A External Wall Temperature CTSAHA1 Bed A Heater 1 Temperature C TSAHA3 Bed A Heater 3 Temperature C

This plot shows the temperatures and pressures together. When Bed A transitions into desorb mode (about 5.5 hours on the plot) the heaters are turned on and the temperature and pressure of the bed quickly rise. Even though the bed temperature and pressure are not at the maximum at hour 6.0, the bed is capable of delivering full flow at this time (see plot 1). The temperature and pressure continue 

to rise until the delivery pressure of 1000 torr is reached and delivery is initiated. Once the delivery pressure is met, the heater power 

is reduced to maintain the pressure and the temperature momentarily drops. As CO2 is drawn off the bed, the temperature is increased to maintain pressure until the end of the cycle (hour 8.5 on the plot). Upon switching beds, the bed that was previously desorbing is 

isolated and cooled to reduce the internal pressure, preparing it for adsorption from the 4BMS, 

150
Plot 18 -- TSAC Inlet Flow Rate

-500

0

500

350030002500200015001000

1 2 3 4 5 6 7 8 910 11

Tim e, Hours

CO2 flow, sccm

TSAFcdra TSAC Inlet CO2 Flow rate sccm

This plot shows the flow rate of CO2 from the 4BMS into the TSAC. The CO2 comes off the 4BMS in a wave, and the saw tooth flow pattern at the end of each cycle is due to the oscillating heater control in the 4BMS as the last of the CO2 is desorbed from the 4BMS 

bed. 

151
5.2.7 4BMS/CEDU/Sabatier Fully Integrated Case 

POIST 4BMS/CEDU/Sabatier Testing – TP 3 – Elapsed Time from 2/4 – Test Day 16 2005 

Plot 1 -- Status for 4BMS, CRA, OGA and Compressor (offset for clarity)

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Time, Hours

status

CDPMpde 0OF 1SH 2A1 3A2 4A3 5B1 6B2 7B3 8WP CRA Ready (11=on 10=off)OGA Ready (9=on 8=off) Compressor Status (13=on 12=off)

This first plot shows the status of the different subsystems. In this test point, the Sabatier was operated cyclically. There was no real Oxygen Generation Assembly in the integrated test, but the test control system sent a signal to the Sabatier representing the OGA status, to which the Sabatier operation would respond. When the OGA signaled that it was Off, the Sabatier went to Standby or Not 

Ready status. Once the Sabatier had completed its health checks it would return a Ready status even though the OGA was not yet on. 

The Sabatier would wait for the OGA ready signal before going back to Process mode. The 90 minute OGA cycle was completely independent of the 4BMS 144 minute half cycle. 

152
Plot 2 --SEDU Reactor Cooling Control

0

800600400200

12001000

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Time, Hours

Temperature (F)

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Open/Closed, 

Flow (SLPM)

SEDT React A Reactor Hot Zone degF SEDT React Out Reactor Outlet degFSEDReactCool 501 Cooling Air Valve 1=closed 0=open MEDFlw 021 Sabatier CO2 Flow SLPMH2 Rate adjusted, SLPM (@0°C)

This plot shows the reactor temperatures and cooling control operation. The cooling air valve was set to open to maintain the reactor 

exit temperature below 300 F. Since this case was cyclic operation at 3 crew rate of hydrogen flow, the temperature was always below 300 F and the cooling air valve was always kept closed. As the Sabatier cycled from Process to Standby, the hydrogen and CO2 flow 

to the reactor was stopped and the reactor would naturally cool off until the next Process cycle began and the reactor heated itself up again. 

153
Plot 3 -- SEDU Separator Level Control

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Time, Hours

On/Off, Delta Pressure 

(IWC)

1600150014001300120011001000

Weight (grams)

SEDPUMP301 Water pump 1=on 0=off SEDDP409 Separator Delta Pressure"H2O SEDMas020 Sabatier EDU Water Grams

This plot shows the level control in the phase separator of the Sabatier. Since the system is operating cyclically, there are periods when the level in the separator stops increasing. This is the time when the Sabatier is in Standby and water generation ceases. The gradually increasing slope of the blue line is when water is generated at a constant rate during Process mode. The sharp vertical lines are simply irregular data from the differential pressure sensor. The orange line represents the accumulated water product that is recorded by a 

digital scale. The total increases in steps as the water from the separator is periodically pumped out to the reservoir on the scale. Each 

time the water is pumped out, the level decreases and then starts slowly building again. The data collection is once per minute, and the pump operation only lasts 5 seconds, so rarely is the pump activity captured by the data stream. 

154
Plot 4 -- SEDU System Pressures

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Time, Hours

PSIA

109876543210

PSID

SEDP006 Reactor inlet pressure PSIA SEDP601 Reactor outlet pressure PSIASEDDP405 Reactor Delta Pressure PSID SEDDP409 Separator Delta Pressure"H2O

This plot shows the different pressures within the Sabatier system. The reactor inlet and outlet pressures vary from 12 and 10 psia (respectively) during the Process mode to about 1 psia during the Standby mode. During each Standby period, the reactor is evacuated to space vacuum to exhaust the potentially flammable gases. While the pressure is low, the system does a self check to determine if there are any leaks. The reactor differential pressure is about 1 psid while gas is flowing, and it goes to zero during the Standby period of no flow. 

155
Plot 5 -- SEDU System Efficiency

0

500

350030002500200015001000

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Time, Hours

Weight (grams), Usage 

(lites)

Calc H2O Prod @ 100% Eff, gram Calc H2O Prod @ 90% Eff, gram Calc H2O Prod @ 80% Eff, gramH2O Production, grams H2 Useage Rate, Liters

This plot shows the actual water production and the calculated production based on different efficiency rates. The top line is the hydrogen usage, and it levels off every time the system switches into standby. The H2O Production line is the same value from the 

digital scale as was shown on the level control plot (#3). The calculated production values are the amount of water that would be collected if the system operated at the stated efficiency. For 100% efficiency, the water generation rate is 0.4 grams water per standard liter of hydrogen consumed. 

156
Plot 6 -- SEDU Molar Ratio

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Time, Hours

Flow (SLPM @ 0 C)

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Molar Ratio

H2 Rate adjusted, SLPM (@0°C) MEDFlw 021 Sabatier CO2 Flow SLPM Calc MR from Actual Flow

This plot shows the flow control of the hydrogen and carbon dioxide. The hydrogen is controlled by a mass flow controller and is therefore very constant. The CO2 is controlled by a motorized valve and must respond to the changing CO2 accumulator pressure. The CO2 flow control is not as constant as the hydrogen, but the molar ration remains very close to 3.5 throughout the test. 

157
Plot 8 -- SEDU Temperatures

0

800600400200

12001000

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Time, Hours

Hot Zone and Inlet Temps

SEDT React A Reactor Hot Zone degF SEDT React B Reactor Hot Zone degF SEDT React C Reactor Inlet degFSEDT React D Reactor Inlet degF SEDT React Out Reactor Outlet degF

This plot shows the Sabatier reactor temperatures during testing. It is the same characteristic as the Sabatier stand alone testing. 

158
Plot 9 -- SEDU Water Production Rate

0

800600400200

1000

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Time, Hours

Rate (gm/hr)

210

Mode

H2O Production, grams SEDStandby Standby Mode SEDOGA READY Status 1=on 0=off

This plot shows the water production rate overlaid with the Sabatier Ready status. The water collected increases only while the system 

is in Process mode and not in Standby. 

159
Plot 10 -- SEDU Overview

0

800400

200016001200

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Time, Hours

Temperature (F), Accum 

Pressure (PSIA)

20181614121086420 Reactor Pressure (psia)

SEDT React A Reactor Hot Zone degF SEDT React Out Reactor Outlet degFMEDPrs021 Accumulator Pressure or CO2 inlet PSIA SEDMas020 Sabatier EDU Water GramsSEDP601 Reactor outlet pressure PSIA

This plot is an overview of the Sabatier system operation. It shows the accumulator pressure, system pressure, reactor temperatures and the cumulative water product collected. With this one plot, one can tell that the system is operating in cyclic more, the temperatures are stable and the outlet temperature is cool enough to not need cooling air. The accumulator pressure is relatively low 

(about 50 psi) throughout the cycles. 

160
Plot 11 -- SEDU Status

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Time, Hours

Status

706050403020100

Pressure (psia)

OGA Ready (9=on 8=off) CRA Ready (11=on 10=off)SEDStandby Standby Mode SEDCompressor command 1=on 0=offMEDPrs021 Accumulator Pressure or CO2 inlet PSIA

This plot shows the status of the different operating systems and the accumulator pressure with the time scale magnified. At about 3.8 hours, the pressure in the accumulator dips below 20 psia. The Sabatier has to transition to Standby mode during this time that there is insufficient CO2, and therefore the Sabatier status is Not Ready. Each time the compressor turns on (bottom line) the pressure in the 

accumulator increases. When the OGA is operating and the Sabatier is in Process (red line) the pressure in the accumulator decreases as CO2 is drawn out. 

161
Plot 12 -- SEDU CO2 Flow Control Accuracy

0

0.5

1

1.5

2

2.5

3

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Time, Hours

Flow (SLPM), 

Reactor Press (psia)

706050403020100

Accum Pressure 

(PSIA)

MEDFlw 021 Sabatier CO2 Flow SLPM Desired CO2 Flow (SLPM)MEDPrs021 Accumulator Pressure or CO2 inlet PSIA SEDP006 Reactor inlet pressure PSIA

This plot shows the control accuracy of the CO2 modulating valve. The accumulator pressure is the upstream pressure to the valve. The reactor pressure is the downstream pressure. The valve must control flow over 4:1 flow turndown and 6:1 pressure turndown. The 

dark blue line is the desired flow and the red line over it is the actual flow as measured by a mass flow meter. The actual flow is within 4% of the desired flow. 

162
Plot 2 -- CEDU Status

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Suction Press (PSIA), Flow (lb/hr), 

On/Off, Day, Night

706050403020100

Day/Night Status (7=day, 6=night) SEDCompressor command 1=on 0=offMEDFlw 020 Compressor Outlet Flow after DP lb/hr MEDPrs020 Compressor Inlet Pressure PSIA MEDPrs021 Accumulator Pressure or CO2 inlet PSIA

This plot shows the status of the mechanical compressor when integrated with the 4BMS and Sabatier. It shows the compressor inlet and outlet pressures and flow rate. This information is used to fine tune the compressor operating logic to minimize power and maximize CO2 recovery. 

163
Plot 4 -- CEDU Inet and Outlet Pressures, Outlet Dew Point

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Inlet (PSIA)

120100806040200-20-40

Outlet (PSIA), Dew Point 

(deg F)

MEDPrs020 Compressor Inlet Pressure PSIA MEDPrs021 Accumulator Pressure or CO2 inlet PSIAMEDDP_020 Mechanical Compressor Outlet Dew point F 

This plot additionally shows the dew point of the CO2 leaving the compressor. The tall spikes at 4.5 and 16.4 hours are calibration runs of the dew point sensor. The dew point never exceeds 30 F, therefore condensation in the compressor or accumulator is not an 

issue. 

164
Plot 5 -- Sorbent Bed Heater Temperatures

0

50

450400350300250200150100

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Time, Hours

Temperature, degrees F

CDPmt13 5A Bed 308 Heater Temp A F CDPmt16 5A Bed 309 Heater Temp A F 

This plot shows the variation of 4BMS operation when the system test is simulating a day/night cycle. The heaters in the 4BMS are 

turned off during the night portion of the cycle resulting in temperature decrease of the desorbing bed. The cycle at hour 3 does not produce enough CO2 and results in a short period of CO2 starvation for the Sabatier (noted in plot # 11 above). 

165
5.2.8 4BMS/TSAC/Sabatier Fully Integrated Case 

POIST 4BMS/TSAC/Sabatier Testing – Lunar Night 1C – Elapsed Time from 1/27/2006 

The following plots are from one of the tests with the TSAC and the 4BMS and Sabatier. The conditions were set to simulate a Lunar mission with 4 crew all leaving for EVA together and returning together. The CO2 from 2 crew members is regenerated two hours after return from EVA, and the CO2 from the remaining 2 crew members is regenerated the next day. 

Plot 1 -- Status for 4BM S, TSAC and Sabatier

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10 15 20 25 30 35 40 45 50 55 60 65 70 75

Time, Hours

status

2000180016001400120010008006004002000-200

sccm

CDPMode 0OF 1SH 2A1 3A2 4A3 5B1 6B2 7B3 8WP CRA Ready (11=on 10=off)OGA Current/10 TSAFprod TSAC Outlet CO2 Flow rate sccm

This plot shows the status of the different subsystems in the test. The Lunar mission is assumed to be in daylight all the time, therefore there is no Day/Night cycling as in the ISS Mission scenarios used in the mechanical compressor tests. There are a few false starts at 

the beginning of the test, then at hours 22, 25 and 27 there are periods where the Sabatier switched to Standby. Later plots will show that the mission scenario resulted in periods of CO2 starvation for the Sabatier subsystem. Around 30 hours, there is a period where 

the Sabatier rapidly switched from Process to Standby. This occurred because the deadband on the pressure setpoint to turn the 

166
Sabatier on and off was too narrow, and the normal operation caused the pressure to cross that span quickly. One of the 

recommendations for future modifications is to broaden that deadband. 

Plot 2 -- Carbon Dioxide Partial Pressures at 4BM S Inlet, 4BMS Outlet, and in 

Lab M odule Simulator

-5

50

201510

10 15 20 25 30 35 40 45 50 55 60 65 70 75

Time, Hours

mmHg

FMG62 4BMS Inlet Air CO2 Pressure mmHg FFG69 4BMS Outlet Air CO2 Pressure mmHg FMG10 Lab Air CO2 Pressure mmHg

This plot shows the CO2 concentration at the inlet of the 4BMS. This concentration profile was the output result of modeling the 

Lunar habitat with the crew activities and location. This profile includes the 4 crewmember EVA with the staggered regeneration. The outlet CO2 is almost zero except for the sharp spikes at the bed changes. There is an increase in CO2 at the output between hours 35 and 40. This is the time period when the first two EVA CO2 packs are regenerated and the 4BMS in the habitat cannot keep up with the additional CO2 load during regeneration. This effect is seen again between hours 60 and 65 when the next two EVA packs are regenerated. 

167
Plot 3 -- Air Dewpoint at 4BM S Inlet and in Lab M odule Simulator

70605040302010

10 15 20 25 30 35 40 45 50 55 60 65 70 75

Time, Hours

Temperature, degrees F

CDPDP_120 4BMS Inlet Air Dew point #1 F AFcDP_120 Lab Air Dew point F 

This plot shows dew point readings at the 4BMS inlet and in the Lab Module simulator. The section between hour 30 to 50 is an 

apparent bad sensor reading. The tall spikes are calibration runs of the sensor. During each cycle, as the beds change, a dump of humid 

air from the desorbing bed is returned to the inlet of the condensing heat exchanger, which in turn feeds back to the inlet of the 4BMS. 

The red line shows the small spike in inlet humidity at each bed change, which is then reduced as the cycle completes its course. The blue line is the lab module average humidity, which follow the trend of the inlet humidity. Water is continuously injected into the lab module to make up for the water lost to the vacuum simulator. The inlet, being downstream of the condensing heat exchanger, is typically at a lower dew point than the lab module average. 

168
Plot 4 -- Air Temperature at 4BM S Inlet, 4BM S Outlet, in Lab M odule Simulator, 

and Water Temperature at Precooler Inlet

0

50

200150100

10 15 20 25 30 35 40 45 50 55 60 65 70 75

Time, Hours

Temperature, degrees 

F

CDPTmp120 4BMS Inlet Air Temperature F CDPTmp121 4BMS Outlet Air Temperature F AFcTmp120 Lab Air Temp. Middle F CDPTmp086 4BMS Precool Inlet H2O Temp #1 F

This plot shows the air and cooling water temperatures at the 4BMS. When the beds switch, the air exiting is initially very high 

temperature as it is flowing through the bed that was just recently heated to 400 F. This hot air is used to desorb the desiccant bed that is full of water. The air temperature quickly returns to normal temperatures as the bed cools down and begins adsorbing CO2. The air 

inlet temperature is cooler than the average Lab Module temperature since it has been cooled by the condensing heat exchanger. 

169
Plot 5 -- Sorbent Bed Heater Temperatures

0

50

450400350300250200150100

10 15 20 25 30 35 40 45 50 55 60 65 70 75

Time, Hours

Temperature, degrees F

CDPmt14 5A Bed 308 Heater Temp B F CDPmt16 5A Bed 309 Heater Temp A F 

This plot shows the 4BMS bed heater temperatures. Since the simulation is always daytime, the heaters of the 4BMS are kept on full power according to the normal processing schedule, i.e., there is no power save mode that turns heaters off. Each bed is heated to 400 F to desorb the CO2. 

170
Plot 6 -- Desiccant Bed Inlet and Outlet Air Temperatures

0

908070605040302010

100

10 15 20 25 30 35 40 45 50 55 60 65 70 75

Time, Hours

Temperature, degrees F

CDPTmp120 4BMS Inlet Air Temperature F CDPmt11 Desiccant Bed Outlet Temperature F 

This plot shows the temperature of the air into and out of the adsorbing desiccant bed. The temperature rises due to the heat of adsorption of water onto the desciccant. 

171
Plot 7 -- Desiccant Bed Outlet Air Dewpoint Temperature

-95.5

-95

-94.5

-94

-93.5

-93

-92.5

10 15 20 25 30 35 40 45 50 55 60 65 70 75

Time, Hours

Temperature, degrees F

CDPDP_023 Dessicant Bed Outlet Air Dew pt F 

This plot shows the dew point of the air leaving the desiccant and entering the CO2 adsorption bed. This dew point is monitored for breakthrough. Water that escapes the desiccant bed will interfere with the adsorption of CO2 onto the CO2 sorbent bed. The bed would then have to be regenerated at high temperature to remove the water. 

172
Plot 8 -- 4BM S Process Air Flow Rate, Fan dP

50

353025201510

10 15 20 25 30 35 40 45 50 55 60 65 70 75

Time, Hours

SCFM

4035302520151050

CDPFlw 120 4BMS Inlet Air Flow rate SCFM (Sierra) CDPFlw 121 4BMS Inlet Air Flow rate SCFM (TSI) CDPmp10 Blow er Delta Pressure inH2O

This plot shows the air flow rate to the 4BMS and the blower pressure drop. The pressure drop rises quickly while the air temperature 

is high from the desiccant. (Refer back to plot 6). The air flow was measured with two different devices, which showed very good agreement. 

173
Plot 9 -- 4BM S Vacuum System Pressures

-2

86420

16141210

10 15 20 25 30 35 40 45 50 55 60 65 70 75

Time, Hours

PSIA/Torr

20181614121086420

CDPPrs123 Sorbent bed 308 pressure PSIA CDPmp12 Pump Inlet Air Pressure PSIACDPPrs023 Fac Vacuum Tank Air Inlet Pressure Torr CDPPrs024 Fac Vacuum Tank Air Pressure Torr 

This plot shows vacuum pressures of the 4BMS. The 4BMS desorbing bed (bed 308) and the TSAC inlet pressure (Pump Inlet Air Pressure) are almost the same except for the pressure drop between the two systems. The spikes in the Facility Vacuum pressures

indicate when either the 4BMS is performing its 10 minute space vacuum desorb, or the bed pressure is excessive and the 4BMS must vent early. Between hours 35 and 40, when the EVA CO2 canisters are regenerated, there is excess CO2 in the habitat that the TSAC 

cannot deliver to the Sabatier, therefore, the 4BMS must vent some of the CO2 when its bed pressure increases. This happens again between hours 60 and 65. 

174
Plot 10 -- 4BM S Component Power

-100

0

600500400300200100

10 15 20 25 30 35 40 45 50 55 60 65 70 75

Time, Hours

Watts

CDPmw 12 5A Bed 308 Prim. Heater Pow er Watt CDPmw 13 5A Bed 309 Prim. Heater Pow er Watt CDPmw 14 5A Bed 308 Sec. Heater Pow er Watt CDPmw 15 5A Bed 309 Sec. Heater Pow er Watt Air-Save Pump Pow er, Watts

This plot shows the power usage of the 4BMS. The thick bars are the bed heaters cycling on and off when the bed is at temperature. The heater control is on/off control, which gives the temperature profile the characteristic saw tooth pattern. 

175
Plot 11 -- 4BMS CO2 Injection and Coolant Water Flow Rate

0

0.5

1

1.5

2

2.5

3

3.5

4

10 15 20 25 30 35 40 45 50 55 60 65 70 75

Time, Hours

SLPM/GPM

400350300250200150100500

LBS

MSAFlw 022 Lab CO2 Inject Flow rate SLPM CDPFlw 080 4BMS Precooler Inlet H2O Flow GPM MSAMas020 Facility CO2 Tank Weight Lbs 

This plot shows the CO2 injection rate. This injection rate is a result of the Lunar habitat model with the crew activity, including the EVA scenario previously discussed. The CO2 tank weight is also recorded as a backup to the injection flow rate recording. The coolant flow rate, which is constant at 0.5 gpm, is monitored for system health. 

176
Plot 12 -- TSAC Product Flow Rate

-200

0

800600400200

200018001600140012001000

10 15 20 25 30 35 40 45 50 55 60 65 70 75

Time, Hours

Flow Rate, sccm

TSAFprod TSAC Outlet CO2 Flow rate sccm

This plot shows the TSAC CO2 delivery flow rate to the Sabatier. The delivery is fairly constant until the periods of starvation begin at hour 22, 25 and 27. Then at hour 30, the period begins when the Sabatier repeatedly tried to start and the pressure deadband caused it to shut down. At hour 55 the hydrogen flow setpoint was temporarily set to twice the normal rate. The TSAC was momentarily able to keep up, but then later a period of starvation resulted at hour 57. 

177
Plot 13 -- TSAC Internal Pressures

0

800600400200

12001000

10 15 20 25 30 35 40 45 50 55 60 65 70 75

Time, Hours

Pressure, torr

TSAP1 Bed A Internal Pressure torr TSAP2 Bed B Internal Pressure torr

This plot shows the pressures of the TSAC beds. During periods of starvation (hour 30 to 35), the TSAC bed pressure falls shortbecause there was insufficient CO2 available from the 4BMS. This is seen again at hour 60-65. 

178
Plot 14 -- TSAC Bed A Temperatures

0

50

300250200150100

10 15 20 25 30 35 40 45 50 55 60 65 70 75

Time, Hours

Temperature, °C

TSAHA1 Bed A Heater 1 Temperature C TSAHA3 Bed A Heater 3 Temperature CTSAExtWalA Bed A External Wall Temperature C TSATouchA Bed A Touch Temperature 

This plot shows the temperatures of the TSAC Bed A. The detailed description is given for plot 16. 

179
Plot 15 -- TSAC Bed B Temperatures

0

50

300250200150100

10 15 20 25 30 35 40 45 50 55 60 65 70 75

Time, Hours

Temperature, °C

TSAHB1 Bed B Heater 1 Temperature C TSAHB3 Bed B Heater 3 Temperature CTSAExtWalB Bed B External Wall Temperature C TSATouchB Bed B Touch Temperature C

This plot gives the temperatures for the TSAC Bed B. The detailed description is given for plot 17. 

180
Plot 16 -- TSAC Bed A Pressures and Temperatures

0

800600400200

12001000

10 15 20 25 30 35 40 45 50 55 60 65 70 75

Time, Hours

Pressure, torr

300250200150100500

Temperature, °C

TSAP1 Bed A Internal Pressure torr TSAAirInA Bed A Cooling Air Inlet Temperature CTSAAirOutA Bed A Cooling Air Outlet Temperature C TSAExtWalA Bed A External Wall Temperature CTSAHA1 Bed A Heater 1 Temperature C TSAHA3 Bed A Heater 3 Temperature C

This plot shows the pressure and temperature profile of the A bed. In each cycle, the bed is heated until the delivery pressure is achieved. Heating continues as delivery begins until the temperature reaches a maximum setpoint. In the first cycle, pressure is maintained with the bed temperature below 200 C. In the next cycle, the temperature is increased a little over 200 C and in the third cycle the temperature reaches the maximum setpoint of 275 C. In each of these cycles the CO2 input from the 4BMS was less and less, as noted in Plot 18 below. Around hour 35-40 there is too much CO2 from the 4BMS and the TSAC could not deliver it all to the Sabatier so the bed started the adsorb cycle half full. This is noted in the vacuum system pressure plot back on Plot 9. 

181
Plot 17 -- TSAC Bed B Pressures and Temperatures

0

800600400200

12001000

10 15 20 25 30 35 40 45 50 55 60 65 70 75

Time, Hours

Pressure, torr

300250200150100500

Temperature, °C

TSAP2 Bed B Internal Pressure torr TSAAirInB Bed B Cooling Air Inlet Temperature CTSAAirOutB Bed B Cooling Air Outlet Temperature C TSAExtWalB Bed B External Wall Temperature CTSAHB1 Bed B Heater 1 Temperature C TSAHB3 Bed B Heater 3 Temperature C

This plot of Bed B pressure and temperature shows a couple of instances of the TSAC running out of CO2 pressure for delivery toSabatier. Between hour 25 and 30, the bed loses pressure before the end of the cycle. The following cycle the bed pressure is low for the full cycle, and again the next cycle the bed pressure fall short before the end of the cycle. This is the result of too little CO2 available from the 4BMS the preceding cycle. 

182
Plot 18 -- TSAC Inlet Flow Rate

-1000-2000-3000

0

7000600050004000300020001000

10 15 20 25 30 35 40 45 50 55 60 65 70 75

Time, Hours

CO2 flow, sccm

TSAFcdra TSAC Inlet CO2 Flow rate sccm

This plot shows the CO2 flow rate from the 4BMS to the TSAC. The CO2 comes off the CO2 adsorbent bed in a wave. Most of the flow comes off as the bed temperature is climbing. Once the bed reaches its setpoint temperature, the heaters start turning on and off to maintain the setpoint. Each time the heaters turn on, more gas is released, and when the heaters turn off, the flow rate decreases. 

This profile could potentially be improved with a variable power heater control instead of the on/off control. 

183
Plot 19 -- SEDU Separator Level Control

9876543210

10 15 20 25 30 35 40 45 50 55 60 65 70 75

Time, Hours

On/Off, Delta 

Pressure (PSID)

40003500300025002000150010005000

Weight (grams)

SEDSEP_run Separator run status SEDDP409-1 Separator DP PSID SEDMas020 Sabatier EDU Water Grams

This plot shows the operation of the rotary phase separator in the Sabatier system and the water collection rate. The rotating bowl of the separator gradually fills with water that is condensed in the heat exchanger. The differential pressure between the liquid at the bottom of the bowl and the gas pressure slowly rises as more liquid is accumulated. When the pressure reaches a setpoint, the speed is increased to pump the liquid out, dropping the differential pressure as the liquid is removed. During this test, the separator collected about 140 grams of water between each pumpout over a time period of about 116 minutes. This equates to 1.2 grams/minute of water 

generation. At the hydrogen inlet flow rate of 3.26 slpm, the maximum water recovery possible is 1.3 grams/minute. The Sabatier

achieved 92% recovery during the steady state portions of this test. 

184
Plot 20 -- SEDU System Pressures

86420

1816141210

10 15 20 25 30 35 40 45 50 55 60 65 70 75

Time, Hours

PSIA

2.521.510.50

PSID

SEDP006-1 reactor inlet pressure PSIA SEDP601 H2 vent pressure PSIA SEDDP405 Reactor DP PSID 

This plot shows the Sabatier system pressures. During steady state operation, the reactor pressure is about 10 psia. Operating at subambient pressure is a safety feature of the system that prevents leakage of flammable gas to the cabin environment. Any time the Sabatier transitions to Standby the system is evacuated to vacuum to remove the gases. The downward spikes in the plot indicate the times that the Sabatier went to Standby due to starvation. 

185
Plot 21 -- SEDU System Efficiency

-1000

0

50004000300020001000

10 15 20 25 30 35 40 45 50 55 60 65 70 75

Time, Hours

Weight (grams)

120001000080006000400020000

H2 Usage (liters)

Calc H2O Prod @ 100% Eff, gram Calc H2O Prod @ 90% Eff, gram Calc H2O Prod @ 80% Eff, gramH2O Production, grams H2 Useage Rate, Liters

This plot shows the actual water collection compared to the theoretic production rate. At 100% recovery efficiency, the Sabatier reaction created 0.4 grams of water for each standard liter of hydrogen consumed. The overall water generation during this entire test was about 86%. 

186
Plot 22 -- SEDU M olar Ratio

86420

1210

45 50 55 60

Time, Hours

Flow (SLPM @ 0oC)

54.543.532.521.510.50

Molar Ratio

SEDMFM006 CO2 flow rate SLPM Desired CO2 Flow (SLPM)H2 Rate adjusted, SLPM (@0°C) Calc MR from Actual Flow

This plot shows the molar ratio of hydrogen to CO2 during the test. The stoichiometric ratio for the Sabatier reaction is 4 moles hydrogen per mole CO2. The Sabatier is typically operated at a molar ratio of 3.5 because there is usually excess CO2 available in a 

partially closed loop Air Revitalization System. At one point in the test (hour 55) the hydrogen flow rate was temporarily increased and the CO2 flow increased to match it at the same ratio of 3.5. The molar ratio value is undefined when the hydrogen and CO2 flows 

are both zero. 

187
Plot 23 -- SEDU Temperatures

0

800600400200

12001000

10 15 20 25 30 35 40 45 50 55 60 65 70 75

Time, Hours

Hot Zone and Inlet 

Temps, degrees F

SEDT403_1 Reactor Temperature 1 deg F SEDT403_2 Reactor Temperature 2 deg F SEDT403_3 Reactor Temperature 3 deg F SEDT403_4 Reactor Temperature 4 deg F SEDT404_1R Reactor Outlet Temperature deg F SEDT407_2R Heat Exchanger Outlet Temperature 2 deg F 

This plot shows the Sabatier reactor temperatures during the test. The top line is the hot zone of the reactor. The reactor cools quickly any time the system transitions to Standby. Each time the reactor temperature dips in the plot is an indication that there was CO2 starvation. 

188
Plot 24 -- SEDU status

86420

1210

10 15 20 25 30 35 40 45 50 55 60 65 70 75

Time, Hours

Status

2520151050

Pressure (PSIA)

OGA Current/10 CRA Ready (11=on 10=off)SEDSTANDBY_Stat Indicator 0=FALSE 1=TRUE SEDPROCESS_Stat Indicator 0=FALSE 1=TRUE SEDP002 CO2 inlet pressure PSIA 

This chart shows the status of the Sabatier system and the CO2 inlet pressure. CO2 availability and OGA ready are the two key indicators that determine if the Sabatier can operate. This mission scenario had OGA ready all the time, therefore the CO2 inlet pressure was the cause for the Sabatier being unable to operate. 

189
References 

Reference Papers presented at the International Conference on Environmental Systems 

(ICES) 

Ref 

No. 

Paper No. Title Authors 

[1] 2006-01-

2271 

Integrated Test and Evaluation of a 4-Bed 

Molecular Sieve, Temperature Swing 

Adsorption Compressor, and Sabatier 

Engineering Development Unit 

James C. Knox 

Melissa Campbell 

Lee A. Miller 

Lila Mulloth 

Mini Varghese 

Bernadette Luna 

[2] 2006-01-

2133 

Modeling and Analyses of an Integrated 

Air Revitalization System of a 4-Bed 

Molecular Sieve Carbon Dioxide 

Removal System (CDRA), Mechanical 

Compressor Engineering Development 

Unit (EDU) and Sabatier Engineering 

Development Unit 

Frank F. Jeng 

Melissa Campbell 

Sao-Dung Lu 

Fred Smith 

James Knox 

[3] 2006-01-

2126 

Performance Characterization of a 

Temperature-Swing Adsorption 

Compressor Based on Integrated Tests 

with Carbon Dioxide Removal and 

Reduction Assemblies 

Lila Mulloth 

Micha Rosen 

Mini Varghese 

Bernadette Luna 

Bruce Webbon 

James C. Knox 

[4] 2005-01-

2864 

Integrated Test and Evaluation of a 4-Bed 

Molecular Sieve (4BMS) Carbon Dioxide 

Removal System (CDRA), Mechanical 

Compressor Engineering Development 

Unit (EDU), and Sabatier Engineering 

Development Unit (EDU) 

James C. Knox 

Melissa Campbell 

Karen Murdoch 

Lee A. Miller 

Frank Jeng 

[5] 2004-01-

2496 

Analysis of the Integration of Carbon 

Dioxide Removal Assembly, 

Compressor, Accumulator and Sabatier 

Carbon Dioxide Reduction Assembly 

Frank F. Jeng 

Sharon Lafuse, 

Frederick D. Smith 

Sao-Dung Lu 

James C. Knox 

Melissa L. Campbell, 

Timothy D. Scull 

Steve Green 

[6] 2004-01-

2375 

Integrated Testing of a 4-Bed Molecular 

Sieve and a Temperature-Swing 

Adsorption Compressor for Closed-Loop 

Air Revitalization 

James C. Knox 

Lila M. Mulloth 

David L. Affleck 

190
[7] 2004-01-

2444 

Measurement of Trace Water Vapor in a 

Carbon Dioxide Removal Assembly 

Product Stream 

Joda Wormhoudt 

Joanne H. Shorter 

J. Barry McManus 

David D. Nelson 

Mark S. Zahniser 

Andrew Freedman 

Melissa Campbell 

Clarence T. Change 

Frederick D. Smith 

[8] 2004-01-

2374 

Air Cooled Design of a TemperatureSwing Adsorption Compressor for 

Closed-Loop Air Revitalization Systems 

Lila M. Mulloth 

Dave L. Affleck 

Micha Rosen 

Martin D. LeVan 

Yuan Wang 

Celio L. Cavalcante 

[9] 2003-01-

2627 

Development of a Temperature-Swing 

Adsorption Compressor for Carbon 

Dioxide 

Lila M. Mulloth 

David L. Affleck 

[10] 2000-xxxxxx A Solid State Compressor for Integration 

of CO2 Removal and Reduction 

Assemblies 

Lila M. Mulloth 

John E. Finn 

[11] 2005-01-

2942 

Long-Duration Testing of a TemperatureSwing Adsorption Compressor for 

Carbon Dioxide for Closed-Loop Air 

Revitalization Systems 

Lila M. Mulloth 

Micha Rosen 

Mini Varghese 

Non-ICES Papers 

[12] JSC62218 

CTSDADV-546 

Test Plan and Requirements for the 

Integrated Evaluation of the 4-Bed 

Molecular Sieve (4BMS), Mechanical 

Compressor Engineering Development 

Unit (EDU), and Sabatier Engineering 

Development Unit (EDU) 

Melissa Campbell 

[13] Test Plan And Requirements For The 

Integrated Evaluation Of The 4-Bed 

Molecular Sieve (4BMS), Temperature 

Swing Adsorption Compressor (TSAC), 

And Sabatier Engineering Development 

Unit (EDU) 

Melissa Campbell 

[14] International Space Station Trace 

Contaminant Injection Test, Revision A, 

NASA Test Requirements Document, 

January 1997 

J. D. Tatara 

J. L. Perry 

191
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Integrated Evaluation of Closed Loop Air Revitalization System 

Components

K. Murdock

George C. Marshall Space Flight Center, Marshall Space Flight Center, AL 35812

Wolf Engineering, LLC, 24 Gulf Road, Somers, CT 06071

National Aeronautics and Space Administation

Washington, DC 20546–0001

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Availability: NASA CASI (443–757–5802)

Prepared for the Exploration and Space Operation Programs and Projects Office, Science and Missions Systems Office

COTR: Monserrate C. Roman

M–1300

NNM10AB15P

Contractor Report 01/11/04 to 03/31/06

NASA/CR—2010–216451

Environmental Control and Life Support Technologies, Air Revitalization System, Closed Loop Air Revitalization System, 4-Bed Modular Sieve, 

Mechanical Compressor Engineering Development Unit, Temperature Swing Adsorption Compressor, Sabatier Engineering and Development Unit

01–11–2010

U U U UU 200

NASA’s vision and mission statements include an emphasis on human exploration of space, which 

requires environmental control and life support technologies. This Contractor Report (CR) describes the 

development and evaluation of an Air Revitalization System, modeling and simulation of the components, and integrated hardware testing with the goal of better understanding the inherent capabilities 

and limitations of this closed loop system. Major components integrated and tested included a 4-Bed 

Modular Sieve, Mechanical Compressor Engineering Development Unit, Temperature Swing Adsorption 

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