rapid cycle amine 3.0 system development

45th International Conference on Environmental Systems ICES-2015-313 12-16 July 2015, Bellevue, Washington

Rapid Cycle Amine 3.0 System Development

Cinda Chullen,1 and Colin Campbell2

NASA Johnson Space Center, Houston, Texas, 77058

and

William Papale,3 Kevin Hawes,4 and Robert Wichowski5

UTC Aerospace Systems, Windsor Locks, Connecticut, 06096

The Rapid Cycle Amine (RCA) 3.0 system is currently under development by NASA at the

Lyndon B. Johnson Space Center (JSC) in conjunction with United Technologies Corporation

Aerospace Systems. The RCA technology is a new carbon dioxide (CO2) and humidity removal

system that has been baselined for the Advanced Extravehicular Mobility Unit Portable Life

Support System. The evolution of the RCA development has progressed through several

iterations of technology readiness levels including RCA 1.0, RCA 2.0, and RCA 3.0 test

articles. The RCA is capable of simultaneously removing CO2 and humidity from an influent

airstream and subsequent regeneration when exposed to a vacuum source. The RCA

technology uses two solid amine sorbent beds in an alternating fashion to adsorb CO2 and

water (H2O) (uptake mode) and desorb CO2 and H2O (regeneration mode). The two beds

operate in an efficient manner so that while one bed is in the uptake mode, the other is in the

regeneration mode, thus continuously providing an on-service sorbent bed by which CO2 and

humidity may be removed. The RCA 2.0 and RCA 3.0 test articles were designed with a novel

valve assembly that allows for switching between uptake and regeneration modes with only

one moving part while minimizing gas volume losses to the vacuum source by means of an

internal pressure equalization step during actuation. The RCA technology also is low power,

small, and has fulfilled all test requirements levied upon the technology during development

testing thus far. A final design was selected for the RCA 3.0, fabricated, assembled, and

performance tested in 2014 with delivery to JSC in June 2015. This paper will provide an

overview on the RCA 3.0 system design and results of pre-delivery testing with references to

the development of RCA 1.0 and RCA 2.0.

Nomenclature

acfm = actual cubic feet per minute

AdvSS = Advanced Space Suit

AES = Advanced Exploration Systems

ALPM = actual liters per minute

atm = atmosphere

cm2 = square centimeter

COTS = commercial off-the-shelf

CO2 = carbon dioxide

EMU = Extravehicular Mobility Unit

EVA = extravehicular activity

1 Project Engineer, Space Suit and Crew Survival Systems Branch, Crew and Thermal Systems Division, 2101 NASA

Parkway/EC5. 2 Portable Life Support System Team Lead, Space Suit and Crew Survival Systems Branch, Crew and Thermal

Systems Division, 2101 NASA Parkway/EC5. 3 Staff Engineer, Research and Development, Space & Sea Systems, 1 Hamilton Rd., Windsor Locks, CT 06096/ M/S

1A-2-W66. 4 Staff Engineer, Electrical Design, Space & Sea Systems, 1 Hamilton Rd., Windsor Locks, CT 06096/S 1A-2-W66. 5 Staff Engineer, Electrical Design, Space & Sea Systems, 1 Hamilton Rd., Windsor Locks, CT 06096/S 1A-2-W66.

International Conference on Environmental Systems

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FPGA = Field Programmable Gate Arrays

FY = fiscal year

GN2 = gaseous nitrogen

HILT = human-in-the-loop

H2O = water

ISS = International Space Station

JSC = Johnson Space Center

kg = kilogram

kPa = kilopascals

LiOH = lithium hydroxide

MetOx = metal oxide

NASA = National Aeronautics and Space Administration

NEOs = near-Earth objects

NGLS = Next Generation Life Support

N2 = nitrogen

O2 = oxygen

Pa = pascal

PAS = Power, Avionics, and Software

PGS = Pressure Garment System

PLSS = Portable Life Support System

psia = pounds per square inch absolute

psig = pounds per square inch gauge

RCA = Rapid Cycle Amine

STMD = Space Technology Mission Directorate

TRL = technology readiness level

UTAS = United Technology Corporation Aerospace Systems

I. Introduction

pacewalks (also known as extravehicular activities [EVAs]) are performed in the vacuum of space, which presents

unique challenges for maintaining life. Therefore, spacesuits must be pressurized. Critical environmental control

functions have to be maintained. Delivering breathing gas to and removing the carbon dioxide (CO2) from an astronaut

are two of the most challenging environmental control functions. In particular, the current technologies used for CO2

removal in the International Space Station (ISS) Extravehicular Mobility Unit (EMU) are lithium hydroxide (LiOH)

and metal oxide (MetOx). Apollo relied on LiOH. The current technologies (LiOH and MetOx) have a limited capacity

and are primarily the limiting factor in the amount of time that a spacewalk can occur. Canisters (either LiOH or

MetOx) are installed into the spacesuit and removed after each use. The LiOH canister can be used only one time. A

14-hour regeneration cycle with an extensive energy demand is necessary for the MetOx technology.1,2

Destinations to near-Earth objects (NEOs) and surface missions to the moon, Phobos, and Mars will have unique

challenges. Therefore, new and improved technologies will be needed to enable these extended missions. The new

technologies for CO2 removal and humidity control in spacesuits will need to be operable over a wide range of

metabolic conditions, sustainable over long durations of time with minimal power and consumable loss, and

regenerative.3

The Rapid Cycle Amine (RCA) technology is a particular technology for CO2 removal and humidity control that

has the potential to meet the stringent requirements for the next-generation Advanced Space Suit (AdvSS). The RCA

uses a solid amine sorbent (designated as SA9T). SA9T was developed to remove, substantially, all the CO2 in either

a dry or humid environment.4 The RCA technology is being employed in the AdvSS Portable Life Support System

(PLSS) in an alternating bed configuration whereby the SA9T can adsorb CO2 in one bed while desorbing the CO2 in

the alternate bed via exposure to vacuum. With continuous access to space vacuum, the RCA system can be

continuously regenerating.5 The RCA system has the potential to operate efficiently and regeneratively to support

extended-duration missions.

The RCA swing-bed technology has undergone a migration from prototype to flight-like unit in a matter of just a

few years. The technology is promising and has been vetted through a series of designs, developments, tests, and

evaluations over the last several years to prove the technology viable for the AdvSS PLSS. These previous efforts and

other laboratory demonstrations have investigated the scalability of the technology, different sorbent canister

geometries, flow control valve designs, and process control schemes aimed at optimizing the RCA for system

S


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integration into the AdvSS PLSS. This paper provides an overview of the PLSS development and the RCA

development, and will focus on the recent design, fabrication, development, and testing of the RCA 3.0 system.

II. Background and Portable Life Support System Development

From 2005 to present, programs such as the Constellation Program, the Exploration Technology Development

Program, the Office of Chief Technology, the Space Technology Mission Directorate, and the Advanced Exploration

Systems (AES) program have continued to facilitate the development of the AdvSS and the advancement of new

technologies for the PLSS. The AES program is currently funding the development of the AdvSS for EVA. The three

major subsystems in the AdvSS include the following: the PLSS; the Power, Avionics, and Software (PAS); and the

Pressure Garment System (PGS). These subsystems are depicted in Figure 1 along with the function of each. The

primary function of the PLSS is to provide the oxygen supply, active thermal control, CO2 removal, and pressure

regulation. The function of the PAS is to provide the caution and warning systems, informatics, communication, audio,

and video along with displays and controls. The function of the PGS is to provide the bladder, softgoods, gloves,

boots, helmet, hard upper torso, and the lower torso assembly along with providing passive thermal control.

A schematic study that was performed during the Constellation Program in 2005 and 2006 resulted in the selection

of a baseline schematic for the next-generation PLSS and associated technologies. The results of the study were

documented in a formal NASA report published in January 2007.6 From 2007 to 2010, the focus was on the technology

development. However, previous development work was performed on the RCA CO2 and moisture removal

technology before the PLSS schematic study ensued, thereby indicating that there was potential with this technology.4

Figure 1. Advanced EVA development subsystems.


4

When the PLSS schematic study was complete, it confirmed that the RCA CO2 and moisture removal system was

the right choice for the PLSS. The RCA then became one of five new technologies targeted for infusion into the

advanced PLSS application. A progression of the RCA development, testing, and infusion into the PLSS from 2006

through 2020 is shown in Table 1. The PLSS progression of development is depicted in Figure 2.

The progression of the PLSS development is under way in house at JSC. Thus far, four progressions of the PLSS

are being realized and planned: PLSS 1.0, PLSS 2.0, PLSS 2.5, and PLSS 3.0. The RCA has been identified as a major

component in all the progressions of the advance PLSS. RCA 1.0 was used for PLSS 1.0 testing. RCA 2.0 is being

used for PLSS 2.0 testing. RCA 3.0 will be used for both PLSS 2.5 and PLSS 3.0.

Table 1. Progression of Development from RCA 1.0 to RCA 3.0 (Letters Denote Months)

Figure 2. PLSS development progression.


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The first system-level evaluation of the advanced PLSS 1.0 schematic—which included the RCA 1.0, four other

new technologies, plus several commercial off-the-shelf (COTS) components—occurred at JSC in 2011 in the PLSS

1.0 breadboard test. It was the first test where all the initial advance developed components were integrated into the

PLSS. The test stand functioned properly and performance

objectives were met. The test demonstrated overall

performance for parameters such as pressure and metabolic

rates. The PLSS 1.0 breadboard testing completed 168 test

points over 44 days of testing.7 There were 397 hours of full

PLSS operation during the testing.

One of the main accomplishments with the PLSS 1.0 test

was the prototype evaluation of the RCA vacuum swing bed

within the ventilation subsystem. The success of the RCA

1.0 evaluation contributed to the PLSS 1.0 testing success.8

Prior to the successful PLSS 1.0 testing, the RCA

technology performed well in testing at the component level

and during performance and checkout testing. The RCA 1.0

is shown in Figure 3.

From 2012 to 2015, the PLSS team at JSC performed the

buildup, packaging, and testing of PLSS 2.0.5 The team has

successfully completed PLSS 2.0 human-in-the-loop

(HITL) testing using the Mark III spacesuit and the RCA 2.0.

Calibration of the instrumentation was performed in-situ,

functional evaluations were performed, and the data are

being analyzed in detail. The test data will evaluate the RCA

2.0 component and subsystem performance. The testing

included 20 to 25 EVAs, failure simulations, and integration

tests. COTS hardware along with tubing and fittings were

used throughout the PLSS 2.0. One of the important aspects of the PLSS 2.0 is the packaging of the PLSS. This

configuration simulates an on-the-back volume of the PLSS. The PLSS 2.0 HITL testing is shown in Figure 4. The

PLSS 2.0 is in the vacuum chamber. The RCA 2.0 is shown in Figure 5 as designed and fabricated.

In fiscal year (FY)16 through FY18, the plan is to build up a PLSS 2.5 unit. This unit will contain the RCA 3.0.

The objectives for PLSS 2.5 include: 1) a flight design without paperwork (gaseous nitrogen (GN2)/air only); 2) pre-

installation acceptance test against system specification; 3) 100 planned unmanned EVAs in vacuum; 4) planned

Figure 3. RCA 1.0 in PLSS 1.0 Test.

Figure 4. PLSS 2.0 HITL Testing.


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unmanned thermal vacuum testing; 5) pressurized launch vibe testing; 6) electromagnetic interference testing; 7) static

magnetics testing; 8) 19 psia air human integrated testing. The design review for the PLSS 2.5 is currently targeted

for April 2016. The RCA 3.0 has been in development over the last 2 years in preparation for infusion into PLSS 2.5.

In FY19 and FY20, the plan is to build up a PLSS 3.0 unit. The RCA prototype to be integrated into the PLSS 3.0

will remain RCA 3.0. The main objective of PLSS 3.0 is to be an oxygen and human-rated flight unit. The other

objectives for PLSS 3.0 include: 1) flight detailed test objective unit; 2) pre-installation acceptance; 3) full

qualification test; 4) 100 unmanned EVAs in vacuum; 5) unmanned thermal vacuum testing; 6) pressurized launch

vibe testing; 7) electromagnetic interference testin testing; 8) static magnetics testing; 9) manned vacuum integration

testing; 10) manned thermal vacuum testing.

III. Rapid Cycle Amine Development

The RCA technology originated in 1996 when Hamilton Standard (now United Technologies Corporation

Aerospace Systems [UTAS]) demonstrated that CO2 and water (H2O) vapor removal was achievable in a venting-type

system. This demonstrated the technology could regenerate when vented to vacuum. The technology implements a

dual-bed solid amine approach. Approximately 20 amine sorbents were studied and tested. The technology was not

mature enough to use in the current space suit. However, there was evidence that venting solid amine swing-bed

system had potential. The swing-bed approach is shown in Figure 6.

The venting approach proved to be

very successful. It appeared that it could

support an indefinite EVA. It was realized

that this technology would be able to

eliminate the CO2 removal system from

being the limiting factor on the length of

EVAs. Other components such as battery

power, O2 supply, and crew member

endurance would be the influencing

factors.9,10 These results were published in

1996. NASA then contracted with UTAS

to develop and build a prototype CO2/H2O

removal and regeneration system and

deliver it to JSC by 1999. The prototype

(RCA 1.0) was successfully designed,

fabricated, laboratory-tested, and

delivered to NASA in 2007.11

Figure 5. RCA 2.0 Designed (left) and RCA 2.0 Fabricated (right).

Figure 6. Solid amine swing-bed system.


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The RCA design consists of alternating adsorption and desorption

amine beds that selectively adsorb CO2 and H2O. One bed adsorbs

while the other bed desorbs. The sorption bed exposed to the spacesuit

ventilation loop can continuously remove CO2 and H2O vapor (Bed A

adsorb), while the other sorbent bed regenerates (Bed B desorb), as

shown in Figure 6. The amine beads are contained inside with a

reticulated aluminum foam (Figure 7) that serves to provide support,

a means of heat transfer media between the beds, and space for growth

and shrinkage to occur within the individual sorbent particles.11

The RCA 1.0 is rectangular in design. Other designs were

considered as an alternate early proof of concept. However, a different

vendor developed these alternate cylindrical canister designs.12 Other

valving types were investigated, including a spool valve, ganged

valve, and drum valve. The test data were analyzed and a math model

was correlated suggesting the rectangular canister was optimal among

the choices.

The RCA 1.0 was a proof-of-concept unit. An RCA 2.0 was built as a full-size assembly. The RCA 2.0 is made

up of an integrated rectangular canister and a ganged ball valve. The ball valve was selected for the RCA 2.0 because

of its previous successful history. UTAS fabricated, tested, and evaluated the RCA 2.0. It was then delivered to NASA

for integration into the PLSS 2.0.

The same vacuum-regenerated technology has been under development for space vehicle applications.13 This

investment of research on the RCA technology enables the practical use of common CO2 removal technology from

EVA spacesuit systems to long-duration vehicles.

IV. Rapid Cycle Amine 3.0

NASA decided that the design and development of an RCA 3.0 was warranted based on the performance of the

RCA during very successful testing that was accomplished with RCA 1.0 performed in the PLSS 1.0 breadboard along

with the performance testing that was accomplished in the RCA 2.0 in the PLSS 2.0.

The development of the RCA 3.0 spanned a 2-year time frame. The development of the RCA 3.0 began in April

2013. A contract was continued with UTAS to design, develop, and fabricate an RCA 3.0 assembly. This effort was

a continuation of the development contract for RCA 2.0. A requirements review was held in June 2013, followed by

a pre-manufacturing design review in September 2013. The kickoff of the buildup was held in February 2014. A major

component of the RCA 3.0 was the controller design and buildup. The controller is required to not only control the

RCA 3.0, but to control other components in the PLSS ventilation loop as well. The delivery of the RCA 3.0 is

expected by the end of June 2015. The significant dates associated with the development of the RCA 3.0 are included

in Table 1, Section II of this paper.

A. Design Goals The RCA performance parameters that were monitored in the Next Generation Life Support (NGLS) program for

RCA 3.0 are shown in Table 2. The NGLS program targeted a mass reduction of 67% as compared to the state-of-the-

art. The RCA 3.0 exceeded that target by a significant amount.14

The RCA 3.0 was designed to comply with the document CTSD-ADV-955, Technology Development

Specification for the RCA CO2 and Humidity Removal System. The design goals for the RCA 3.0 include the

following:

a. Effectively remove CO2 and H2O

b. Incorporate a bypass valve function

c. Optimize for environments specified in CTSD-ADV-955

d. Optimize for valve actuation and drive mechanism efficiency to sustain cycling

e. Minimize ullage losses

f. Optimize for size based on PLSS 2.0 Testing results (mass and volume [bed size])

g. Optimize for fidelity of the packaging in order to be incorporated with PLSS 2.5

h. Improve integrated electronics from RCA 2.0 to achieve optimum integration with PLSS 2.5

Figure 7. Amine sorbent in reticulated

aluminum foam.


8

It was also important that the RCA 3.0 be adaptable to space-like environments. The highest priority included the

requirement to be operable in an environment where oxygen is the working fluid. Oxygen compatibility is essential

for spacesuit application; thereby, it is critical to control ignition sources. It was also essential that the RCA 3.0 also

be compatible with a vacuum and thermal environments for spacesuit application. It is important for the RCA 3.0 to

operate in the fullest ranges of the spacesuit thermal environment. Finally, the RCA 3.0 will need to tolerate certain

launch and vibration loads based on the targeted launch vehicle. A vibration and loads environment assessment is

currently being evaluated.

B. Design

The RCA 3.0 assembly consists of the amine canister, cycling valve assembly, valve motor, and integrated

controller. The RCA 3.0 will be incorporated into the PLSS 2.5 packaged design, which is an ongoing system design

in house by NASA. The PLSS 2.5 is more compact than the PLSS 2.0. RCA 3.0 has been fabricated and tested, with

delivery to NASA planned in June 2015.

An integrated controller design will monitor the RCA 3.0 and other ventilation loop parameters such as partial

pressure of CO2, air flow, pressures, and temperatures. The RCA 3.0 design is shown in Figure 8. The completed valve

and canister (without controller) is shown in Figure 9. Figure 10 shows the RCA 3.0 integrated into the PLSS 2.5.

Figure 8. RCA 3.0 Design. Figure 9. RCA 3.0 manufactured without controller.

Table 2. RCA Key Performance Parameters

aMetOx plus regenerator unit. bBased on life testing of RCA ball valve test article. Valve survived >105,000 cycles, equivalent to ~2,100 EVAs. cTo be determined following completion of PLSS 2.0 Integrated Testing.

Description

State of the

Art (SOA)

Threshold

Values

R&TD

Goals

Measured

Value Rapid Cycle Amine (RCA) Swing Bed

CO2 removal system mass (kg) 60.8a 15.5 5 8.3

System Life (EVA uses) 25 50 100+ >100b

H2O removal rate (g/min) 1.49 1.49 >1.49 TBDc

CO2 removal rate (g/min) 2.26 2.26 3.04 TBDc

Variable Oxygen Regulator (VOR)

Pressure Settings 2 5 84** 7,400

Pressure Range (psi) ~0.9 & 4.3 0.3-8.4 0-8.4 0 - 8.4

Contamination Tolerance < 2mg/ft2

>2 mg/ft2 50 mg/ ft

2 100 mg/ ft

2

Mass (lb) 8 6 3.5 3.96

Alternative Water Processor (AWP)

Wastewater Recycling (Full

Wastewater)d

0%e 85% >95% 92%

Consumable Reduction from SOA - 20% 50% 29%

High Performance EVA Glove (HPEG)

Mobility (% of Barehanded Capability) 20% 40% 60% TBDf

Durability (Useful Life) 7 EVAs 14 EVAs 50 EVAs TBDf

Injury Potential (% of Total Reported

Incidents) 47% 35% 30% TBD

f

Advanced Oxygen Recovery (AOR)

Recovery of O2 from CO2 (%) <50% 75% >95% TBDf

Amine Canister

Inlet

Controller

Vacuum Port Inlet Vacuum Port Outlet

Outlet

Valve Assembly Valve

Assembly


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C. Ball Valve Testing

The RCA needs a reliable valve that can shift from one bed to the other for regeneration to occur. A multiple-ball

valve assembly has been designed and integrated into the RCA assembly to accomplish a near-instantaneous and

simultaneous change in bed states. The RCA ball valve assembly consists of a ventilation inlet diverter valve, a

ventilation outlet diverter valve, and a vacuum diverter valve—all actuated on a common shaft and coupled to a direct-

current-powered stepper gear motor. Through several prototype design iterations, this valve assembly design has

reliably demonstrated the ability to divert the process air flow to the uptake bed while simultaneously directing the

vacuum source to the regeneration bed. Uncertainty in the ability for the valve seats to continue sealing under induced

stresses, such as actuation cycling over the anticipated system lifetime, resulted in the recommendation of cycle testing

of a separate valve assembly.

Analysis of the RCA 3.0 operating life requirements coupled with the anticipated number of valve cycles over an

EVA period (by analysis) yielded a minimum of 5,000 valve cycles. A maximum leak rate of 1 standard cubic

centimeter per minute at a differential pressure of 4.3 psia is specified by requirement. Provided there is no other

significant leak path, this requirement helps establish a maximum leakage rate across the valve seats to vacuum for

testing. Previous hardware testing fell within this leakage requirement up to 2,000 test cycles (prior to requirement

analysis). However, the risk of not meeting this requirement over the anticipated valve lifetime or not identifying a

failure mechanism that leads to excessive leakage would likely have a significant impact on design modifications to

meet this requirement.

Figure 10. PLSS 2.5 design (flight prototype).

RCA 3.0


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Stand-alone testing of an RCA valve assembly was therefore undertaken to evaluate and reduce risk in the ability

to meet the required external leakage rate following a high degree of actuation cycles and at representative actuation

speeds. The accelerated life cycle valve test was conducted on residual valve parts to test RCA 3.0 valve seats. The

test operated the RCA 3.0 ball valve continuously under an accelerated cycle profile. The test was periodically stopped

to measure overall seat leakage at ~1 atm differential to vacuum in each valve position. The cycles were logged. The

leak rate and vacuum was observed. Each valve cycle was defined as movement from Position A to Position B and

back to Position A. The schematic for the RCA valve assembly test apparatus is shown in Figure 11.

The RCA multi-ball valve design that has been incorporated into both the RCA 2.0 and RCA 3.0 assemblies

successfully completed the accelerated valve seat wear testing. The testing demonstrated valve seat sealing ability

well beyond the anticipated valve design cycle life of

5,000 cycles by periodically quantifying leakage rates

over a 105,089-cycle test period and under accelerated

operating conditions. The results of the RCA valve

assembly are shown in Figure 12. The risk of not

meeting currently defined leakage requirements

through the valve assembly over the currently

anticipated life of the RCA assembly is low for similar

operating conditions. Further, no internal valve

component failures were observed in the cycle testing

at the cycle test conditions. Testing to investigate

potential failure mechanisms under more aggressive

conditions or under actual RCA operating conditions

may be an area of further study with this valve

assembly.

D. Rapid Cycle Amine Integrated Controller

The RCA integrated controller is designed to be a

modular component that mounts within the RCA volume. The controller functions currently include the following:

a. Monitor and control RCA operation

b. Monitor and control ventilation loop flow

c. Monitor various input sensors (CO2 concentrations, temperatures, pressures, flow)

d. Process and distribute data to higher-level software control or between controller nodes

Central to the controller design is a field programmable device that incorporates a stepper motor controller, a

brushless motor controller, an analog-to-digital converter, serial communications interfaces, and input discretes for

external user interfaces. At the time of this writing, the controller was undergoing functional verification testing and

final assembly into the RCA 3.0.

Figure 11. RCA valve assembly life cycle test schematic.

Figure 12. RCA value assembly life cycle test results.


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V. Design Comparison of Rapid Cycle Amine 1.0, 2.0, and 3.0

Overall, it has taken a multiyear effort to produce RCA 1.0, RCA 2.0, and RCA 3.0 from design concept to

fabrication and testing. The main design differences between the RCA 1.0, 2.0, and 3.0 are listed in Table 3. This table

reflects the changes in the generations of the hardware.

In RCA 1.0, the beds switch by using a pneumatically actuated linear motion spool valve. The RCA 2.0 and RCA

3.0 valve design is essentially the same using a motorized custom-designed ball valve for switching amine beds. The

improvements included a transition to a design that meets more of the flight environmental and operating requirements.

The canister volume was reduced between the RCA 2.0 and RCA 3.0 designs to support improved PLSS packaging.

Minimal engineering and configuration changes between the RCA 2.0 and RCA 3.0 canister designs allowed for

tooling re-use and similar interfaces with only a slightly modified canister assembly.

A detailed design feature comparison associated with each RCA designed iteration is depicted in Table 4.

Performance comparison of the three design iterations tested over a relevant range of operation is shown in Figure 13,

Table 4. RCA 1.0, 2.0, and 3.0 Design Feature Comparison

* Pressure drop values are shown for O2 at 6 acfm, 4.3 psia, and 70 °F.

*

Table 3. Differences Between the First (RCA 1.0), Second (RCA 2.0), and Third Generation (RCA 3.0)

Designs of the RCA

1.0 2.0 3.0

RCA

Pneumatic spool valve

Subscale

External controller

Operation with air or N2

Ambient Lab Environment

Concept lab-scale unit

Technology readiness level

(TRL) 4

Motorized ball valve

Full scale

Locally mounted controller

Operation with air or N2

Lab or vacuum environment

Form & fit for PLSS integration

TRL 5

Motorized ball valve w/high-

efficiency actuator

Full scale, optimized size

Improved integrated controller

Rated for 100% oxygen

Flight environments

High-fidelity brassboard

TRL 6


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which shows the relative half-cycle time (log-scale) against the CO2 input rate. Note that RCA 1.0 and RCA 3.0 have

similar sorbent volumes, whereas RCA 2.0 has a greater sorbent bed volume. This is reflected in the observed half-

cycle performance in the various designs while operating the units with a CO2 feedback control scheme.

VI. Conclusion

This paper has provided a development summary of the RCA 3.0 technology development. The background of the

PLSS development was reviewed and the infusion of the RCA 1.0, RCA 2.0, and RCA 3.0 was discussed. RCA 3.0

was the final development prototype funded by NASA’s Space Technology Mission Directorate (STMD) and will be

infused into a component test loop upon delivery, followed by the AES AdvSS PLSS 2.5. Ball valve testing was

discussed to reveal the risk of ball valve failure is low. A comparison of the RCA 1.0, RCA 2.0, and RCA 3.0 was

provided. The RCA 3.0 prototype has been discussed including the design, system integration, and testing. Overall,

the successful progress of the RCA technology development provides evidence of being a viable alternate technology

to the existing technologies of MetOx and LiOH that are currently used in the ISS spacesuits.

Acknowledgments

The authors thank the NGLS Project managed by the Game Changing Development Program within NASA’s

STMD for funding the development of the RCA. Additionally, the authors thank the AES program for facilitating

the buildup of the RCA test system and funding the infusion of the technology into their program. The authors thank

the leadership of the Crew and Thermal System Division for the dedicated laboratories to accomplish the testing.

Finally, the authors would like to thank the entire PLSS team for their dedication and committement to furthering

the development of the PLSS.

Figure 13. Results from RCA development testing – CO2 feedback mode (note that numerical

values on axes are not shown since data is subject to export control restrictions).


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