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TR-I028-5

IMPACT OF LOW GRAVITY ON WATER

ELECTROLYSIS OPERATION

FINAl, REPORT

by

F. T. Powell, F. H. Schubert and M. G. Lee

March, 1989

Distribution of this report is provided in the interest

of information exchange. Responsibility for the contents

resides in the authors or organization that prepared it.

Prepared Under Contract NAS9-17966

by

Life Systems, Inc.

Cleveland, OH 44122

for

National Aeronautics and Space Administration

Lyndon B. Johnson Space Center

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FOREWORD

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

under Contract No. NAS9-17966 during the period May 23, 1988 through March 22,

1989. The Program Manager was Ferolyn T. Powell. The principal investigator

for the experiment is Franz H. Schubert. The personnel contributing to the

program and their responsibilities are outlined below:

Personnel

Gene Lee, Ph.D.

Dennis B. Heppner, Ph.D.

Arthur B. Nagel

Franz H. Schubert

David W. Novak

Ferolyn T. Powell

Area of Responsibility

Electrochemical Designs and System

Analysis

Control/Monitor Instrumentation Design

Integrated Current Controller Design

Electrochemical and Mechanical Designs

and System Analysis

Mechanical Design

Flight Experiment Integration Design,

and Program Management

Dr. Simon Ostrach, Case Western Reserve University, was a consultant to the

program, providing expertise in the area of Low Gravity phenomena.

The Contract's Technical Monitor was Albert F. Behrend, Jr., Chief, Special

Projects Branch, Crew and Thermal Systems Division, National Aeronautics and

Space Administration Lyndon B. Johnson Space Center, Houston, TX.
TABLE OF CONTENTS

PAGE

LIST OF FIGURES ............................ iii

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

LIST OF ACRONYMS ........................... v

SUMMARY ................................ i

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

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

Static Feed Water Electrolysis Concept ............. 4

Basic Process ....................... 4

The Static Feed Electrolysis Cell ............. 6

Subsystem Concept ..................... 6

Previous Work Accomplished ................... 8

FLIGHT EXPERIMENT OBJECTIVE/SCOPE ................... 13

JUSTIFICATION FOR CONDUCTING EPICS EXPERIMENT ............. 13

Interrelationship to Other Organizations ............ 15

TECHNICAL DESCRIPTION OF EPICS FLIGHT EXPERIMENT ........... 15

Overall Experiment Design .................... 17

Mechanical/Electrochemical Assembly ............... 17

Integrated Electrolysis Unit ............... 17

Pressure Control and Safety Enclosure ........... 30

Ancillary Components ................... 30

Control/Monitor Instrumentation ................. 30

C/M I General Description ................. 30

ANALYTICAL AND EXPERIMENTAL RESULTS .................. 36

Design Safety Analysis .................... 40

Design Reliability Analysis ................... 40

continued-
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Table of Contents - continued

PAGE

INITIAL COST AND SCHEDULE ASSESSMENTS ................. 40

Implementation Plan ....................... 40

Preliminary Flight Test Plan Overview .............. 44

CONCLUSIONS .............................. 45

REFERENCES .............................. 45

il
LIST OFFIGURES

FIGURE PAGE

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EPICSExperiment Packaging Concept (in Locker) .......

Static FeedWater Electrolysis - A MannedSpaceExploration

Utility ...........................

Electrolyzer Cell Schematic and Reactions ..........

Simplified SFEProcess Schematic ..............

Advancementin Water Electrolysis Technology ........

SFECell, Module and ComponentTest Program .........

Static FeedWater Electrolysis Technology Is Mature .....

NASAConsidering Several Applications of SFE ........

SFEApplications Meet NASAMission Needs/Goals .......

Interrelationship of EPICSExperiment to NASAand Other

Agencies ..........................

EPICSExperiment Packaging Concept .............

EPICSInterface Block Diagram ................

EPICSModesand Allowable ModeTransition ..........

EPICSMechanical/Electrochemical Assembly ..........

EPICSDetailed Mechanical Schematic With Sensors ......

Integrated Electrolysis (IE) Unit ..............

Exploded View of IE Unit ..................

Typical Cylindrical Heat Pipe ................

Cross Section of IE Unit ..................

Pressure Control Enclosure Seal Options ...........

EPICSC/M I and Integrated Current Controller Packaging

EPICSElectrical Block Diagram ...............

Detailed Block Diagram of EPICSCurrent Controller (i of 3) .

Magnification of Gravity Effects on Gas-Liquid Interface/

Electrolyte Distribution ..................

Projected SFEPerformance Improvementsof O-GEnvironment .

Payload Developmentand Integration Schedule ........

Payload Integration Process .................

Preliminary Flight Test Plan for EPICSExperiment ......

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TABLE

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LIST OF TABLES

EPICS General Design Objectives ...............

EPICS Design Specification .................

EPICS Interfaces ......................

EPICS Operating Modes and Unpowered Mode Definitions ....

EPICS Characteristics ....................

Integrated Electrolysis Unit Cell Configurations ......

EPICS Flight Experiment Actuator List ............

EPICS Flight Experiment Sensor List .............

EPICS C/M I Enclosure Characteristics ............

EPICS Integrated Current Controller Characteristics .....

EPICS Shutdown Parameters ..................

EPICS Data Storage Parameters ................

Initial Assessment of EPICS Costs and Schedule .......

PAGE

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iv

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CCDS

C/M I

ECLSS

EPICS

EVA

FCA

IE

M/EA

NASA

NSTS

OAST

OGA

ORU

PCA

PCSE

PDU

SFE

SFWEM

TCA

LIST OF ACRONYMS

Command, Control and Display Subsystem

Control/Monitor Instrumentation

Environmental Control and Life Support System

Electrolysis Performance Improvement Concept

Studies

Extravehicular Activity

Fluid Control Assembly

Integrated Electrolysis

Mechanical/Electrochemical Assembly

National Aeronautics and Space Administration

National Space Transportation System

Office of Aeronautics and Space Technology

Oxygen Generation Assembly

Orbital Replaceable Unit

Pressure Control Assembly

Pressure Control/Safety Enclosure

Performance Display Unit

Static Feed Electrolyzer

Static Feed Water Electrolysis Module

Thermal Control Assembly

V
SUMMARY

Advanced Space Missions will require oxygen and hydrogen utilities for several

important operations including the following: (I) propulsion, (2) electrical

power generation and storage, (3) Environmental Control and Life Support, (4)

Extravehicular Activity, (5) In-Space Manufacturing activities and (6)

In-Space Science activities. A key to providing these utilities for Advanced

Space Missions will be to minimize resupply from earth requirements and

initial earth to orbit launch mass. Static Feed Water Electrolysis technology,

using an alkaline electrolyte, has been recognized as a design capable of

efficient, reliable oxygen and hydrogen generation with few subsystem

components. The Static Feed concept has evolved over the last 19 years under

the National Aeronautics and Space Administration and Life Systems, Inc.

sponsorship. The overall objective of the present program was to perform a

preliminary conceptual design of a flight experiment which investigates ways a

low gravity environment may improve water electrolysis performance.

The program was sponsored by the National Aeronautics and Space

Administration's Office of Aeronautics and Space Technology and monitored by

the Johnson Space Center. The program was a part of the Office of Aeronautics

and Space Technology In-Space Technology Experiment Program. The experiment,

entitled Electrolysis Performance Improvement Concept Studies, meets all

requirements and constraints of a Space Shuttle standard middeck payload.

Projected physical characteristics of the Electrolysis PerformanceqImprovement

Concept Studies experiment are weight of 37.6 lb, volume of 1.9 ft - and 100 W

of power.

The program included consideration of the following: (I) end use design

requirements, (2) phenomena to be studied (e.g., gas/liquid interfaces, fluid

flows, capillary flows, thermal gradients, etc.,), (3) Space Shuttle Orbiter

experiment constraints including flight experiment reliability and quality

assurance requirements and flight experiment design constraints, (4)

experiment descriptions including procedures, timelines and data requirements,

and (5) test hardware requirements to obtain the necessary data. The results

were integrated to arrive at a flight experiment conceptual design and a

preliminary implementation plan which are described in this Final Report.

Design goals and requirements were considered in three subcategories including

(I) scientific, (2) engineering and (3) Space Shuttle Orbiter. The scientific

and engineering goals are to obtain scientific and engineering data for future

research and development. The Shuttle goals and requirements focus on

demonstrating and monitoring for safety and meeting design constraints of a

standard middeck payload. The National Space Transportation System safety

requirements were an important focus throughout the program. These

requirements were evaluated and incorporated into the design. Three levels of

containment, including O-rings, a nitrogen blanket and a sealed enclosure were

incorporated Into the experiment hardware design.

The Electrolysis Performance Improvement Concept Studies experiment integrated

within a Space Shuttle Orbiter standard middeck locker is illustrated in

Figure I.
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Integrated Electrolysis

Pressure Control/

Safety Enclosure

Characteristics

Weight, Ib 37.6

Volume, ft : 1.9

Power, W • 100

L Modified

Standard Middeck

Modular Locker

Locker Door

FIGURE 1 EPICS EXPERIMENT PACKAGING CONCEPT (IN LOCKER)
THIS PAGEINTENTIONALLYLEFTBLANK
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INTRODUCTION

The National Aeronautics and Space Administration (NASA) Office of Aeronautics

and Space Technology (OAST) has developed and initiated a program entitled the

In-Space Technology Experiment Program (In-Step). The primary objectives of

this program as described by Dr. Leonard Harris at the In-Step Workshop, held

December 6 through 9, 1988 in Atlanta, GA, are to obtain data and validate the

feasibility of technologies in space. Inherent in these two objectives is the

concept of utilizing low gravity as a resource to improve the performance of

earth-based technologies. Part of the In-Step Program is to gear up for use

of the Space Station Freedom as an engineering research laboratory.

The In-Step Program is divided into two subprograms. These include the

Inreach and Outreach Programs. The Inreach Program is aimed at experiments

from within the NASA. The Outreach Program includes experiments from industry

and universities. The experiment described in this report is one of the 36

initial Outreach experiments. The Outreach Program is subdivided into eight

theme topics including:

I ,

2.

3.

4.

5.

6.

7.

8.

Space Structures

Space Environmental Effects

Fluid Management and Propulsion

Power Systems and Thermal Management

Automation and Robotics

Sensors and Information Systems

Humans In Space

In-Space Systems

The Electrolysis Performance Improvement Concept Studies (EPICS) flight

experiment described herein has officially been placed in the Humans In Space

theme. As described throughout this report, it will become apparent that the

EPICS experiment will also provide valuable information to the Fluid

Management and Propulsion Theme area as well as the Power Systems and Thermal

Management theme area.

Background

Advanced space missions will require oxygen (0_) and hydrogen (H_) utilities

for several important operations including: (_) propulsion, (2)_electrical

power generation and storage, (3) Environmental Control and Life Support

System (ECLSS), (4) Extravehicular Activity (EVA), (5) in-space manufacturing

activities and (6) in-space science activities. A key to providing these

utilities for advanced space missions will be to minimize resupply from Earth

requirements and initial Earth-to-Orbit launch mass.

This report presents the details of a flight experiment which will investigate

the use of low gravity to improve the performance of an electrochemlcally-based

subsystem which provides these utilities. The experiment focuses on the

Static Feed Electrolysis (SFE) concept of generating 02 and H 2. It is

important to note that this focus on a specific electrochemical process will

not only provide performance design data for that specific process; it will

also provide methodologies, flight experiment hardware and performance

information applicable to a diverse range of electrochemical processes (e.g.,

electrolysis of carbon dioxide from the Martian atmosphere.
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The SFE technology, using an alkaline electrolyte, has been recognized as a

design capable of efficient, reliable 02 and H2 generation with few subsystem

components. Figure 2 illustrates the use of t_e SFE technology as a space

exploration utility. The static feed concept has evolved over the last 19

years under the NASA and Life Systems, Inc. (Life Systems) sponsorship.

During this time, the concept progressed from single-cell operation through

the fabrication and testing of multiperson subsystems (for life support)

culminating in its selection for the Oxygen Generation Assembly (OGA) of the

Air Revitalization System aboard the Space Station Freedom.

Recent developments at Life Systems have demonstrated substantial reduction in

the operating voltage of the electrolysis cells and have allowed for the

consolidation of ancillary components resulting in the reduction of power,

weight, volume and complexity. The overall impact of these state-of-the-art

advancements is significant since the OGA is the largest power consuming

subsystem of a regenerative llfe support system and even more significant when

considering advanced mission scenarios which require tons of 02 production per

year for propellant.

The technical concepts and prior performance are described below.

Static Feed Water Electrolysis Concept

Detailed descriptions of the static feed process| i_,s h _ of operation and

its performance have been discussed previously. , __e_ y The following

subsections briefly summarize the subsystem and cell level concepts and the

electrochemical reactions involved.

Basic Process

Within a water electrolysis cell, water is broken apart into its component

elements by supplying electrons to the hydrogen at a negatively charged

electrode (cathode) and removing electrons from the oxygen at a positively

charged electrode (anode). The half-cell reactions are as follows for water

electrolysis cells using an alkaline electrolyte:

At the cathode:

2 H20 + 2e- = H2 + 2 OH- (I)

At the anode:

m

2 OH -- I/2 02 + 2e + H20 (2)

These result in the overall reaction of:

Electrical Energy + H20 = H 2 + I/2 02 + Heat (3)

(I) Superscripted numbers in parentheses are citations of references listed at

the end of this report.

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The Static Feed Electrolysis Cell

The efficiency with which these reactions can be used for practical Op/H 2

generation is, however, highly dependent on cell technology, especialIy on

electrode components. Figure 3 is a functional schematic of a SFE cell.

As electrical power is supplied to the electrodes, water in the electrode core

is electrolyzed creating a concentration gradient between the water feed

cavity and the electrolyte in the electrode core. Water vapor diffuses from

the water feed matrix cavity through the water feed membrane to the cathode

due to this gradient.

I Supply Power

eCirculating _ :isi_ Feed Water As .,i-- -...... _.--_ i:i:i:i:

Coolant --I !L] ili!::!il

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Reactions

4OH----,,- 02 4- 2H20 + 4e4H20 + 4e-._-- 2H2 + 4OH2H20 + Power --_ 2H2 + 02

I

FIGURE 3 ELECTROLYZER CELL SCHEMATIC AND REACTIONS

Subsystem Concept

The basic cells are combined with supporting components to form the subsystem.

A simplified process schematic of a static feed electrolysis subsystem is

shown in Figure 4. The mechanical/electrochemlcal portion of the subsystem

consists principally of four components: an electrochemical module, a

Pressure Control Assembly (PCA), a Thermal Control Assembly (TCA) and a Fluid

Control Assembly (FCA). The module consists of a series of individual

electrochemical cells stacked fluidically in parallel and connected

electrically in series to form the Static Feed Water Electrolysis Module

(SFWEM). Oxygen and H 2 are generated in the SFWEM from water supplied by the

water supply tank.
_ Circulation Pump _ ---- H2

C) - ----o2

__ Electrol_er

Water Coolant

Heat

Exchanger

Module

FIGURE 4 SIMPLIFIED SFE PROCESS SCHEMATIC

From the module the product gases pass through the PCA which monitors and

adjusts subsystem pressures and maintains proper overall and differential

pressures between the O7, H 2 and water feed cavities of the module. The PCA

is an integrated mechanical component which integrates several components into

one Orbital Replaceable Unit (ORU), increasing reliability and maintainability.

The TCA supplies liquid coolant to the module for thermal control. Again, the

TCA integrates several components into one ORU. The heat is transferred from

the subsystem by way of a liquid/liquid heat exchanger. Water is supplied to

the module by a pressurized, cyclically filled water supply tank. During the

fill cycle, the water tank is isolated from the module and depressurized. The

subsystem has the capability for separate Nitrogen (N?) purging of 02-and-H 2

containing cavities of the SFWEM and for repressurizifig of the water feed tank

after the water tank fill cycle. The fill cycle of the water tank and the

capability for N 2 purging of both the 02 and H 2 cavities of the SFWEM are

controlled by the FCA. The PCA, TCA and FCA are mounted on an interface plate

in which a major portion of the plumbing is embedded.

An automatic control/monitor instrumentation (C/M I) provides the following

functions: (I) automatic mode and mode transition control, (2) automatic

shutdown provisions for self-protection, (3) provisions for monitoring

subsystem parameters, (4) automatic fault isolation diagnostics and (5)

provisions for interfacing with the operator through a performance display

unit (PDU) and/or NASA-provided command, control and display subsystem (CCDS).
Previous Work Accomplished

Major breakthroughs/improvements have been made on electrode performance, cell

design, module construction, integrated ancillary mechanical components,

packaging, maintainability and C/M I. These breakthroughs/Improvements are

well documented in final reports, design handbooks, papers and Life Systems'

engineering reports and notes. Figure 5 illustrates the overall advancement

of the SFE technology.

Extensive endurance testing has shown that the operation of the electrolysis

module gives long life with little cell degradation. Module endurance test

hours that have been achieved within Life Systems' endurance testing program

include one cell operating continuously (noncycllcally) for over 45,000 hours

(five years) and two single cell modules operating cyclically, simulating low

earth orbit conditions for over 45,000 hours each. Converting the cumulative

45,000 and 44,000 hours of operation to cyclic time results in over 74,000 and

71,000 hours (over eight years each) of Space Station equivalent llfe each.

Figure 6 summarizes the SFE test program.

The inherent simplicity of the electrolysis module design is directly

responsible for these results. The static water addition concept of the SFE,

for example, separates the feed water from the cell electrolyte eliminating

electrode catalyst contamination. The amount of electrolyte present in the

module is very small, resulting in negligible corrosion potential. The

extensive endurance testing has shown that the operation of the SFE will meet

long-life requirements without cell degradation. There are no moving parts

within the module stacks.

Multic_ll modules have been built and tested with 0.I ft 2, 0.25 ft 2 and

1.0 ft active individual cell areas.

Several subsystems have been built and tested for application to the ECLSS and

the regenerative fuel cell. Figure 7 pictorially illustrates how the SFE has

matured, reducing size and complexity, while improving performance and

reliability. Current efforts include a 4-person ECLSS OGA for the NASA Space

Station Freedom technology demonstrator program and high pressure gas

generation applicable to EVA O^ bottle recharge and propellant production.

Development of the SFE has bee_ sponsored by many organizations for several

applications, as shown in Figure 8.

The NASA has and is continuing to conduct an extensive endurance testing

program for the ancillary mechanical assemblies of the SFE. The objective of

this testing program is not to generate Mean Time Between Failure data in the

conventional way, but to highlight the types of mechanical improvements and

problems which should be addressed to ensure long llfe and reliable operation,

yet stay within typical research and development funding. The basic functions

of the mechanical assemblies under test will remain the same for the SFE

propulsion application on the Space Station Freedom. However, the

configuration may be changed to feature redundancy, as required, and to

incorporate those design changes based upon what was learned during the

endurance testing program. Additionally, cycling of the assembly hardware is
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Test System, 1965

Static Feed Electrolyzer

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FIGURE 5 ADVANCEMENT IN WATER ELECTROLYSIS TECHNOLOGY
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WX-1

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Prototype

Preprototype (1 Person)

WS-1

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FIGURE 7 STATIC FEED WATER ELECTROLYSIS TECHNOLOGY IS MATURE

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Johnson Space Center

Marshall Space Flight Center

Lewis Research Center

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Application

Propulsion and Power

Life Support

EVA

Propulsion

Life Support

Power

Life Support

High Pressure OxygenHydrogen

FIGURE 8 NASA CONSIDERING SEVERAL APPLICATIONS OF SFE

12
Systems, JHc

being accelerated much beyond what would be required onboard the Space

Station Freedom. This, in effect, leads to increased endurance testing of

these components above the actual hours over which they have operated.

The mechanical assemblies do contain moving and rotating components where

reliability and operating constraints must be considered. These assemblies

should be and are being examined as units rather than a series of individual

components. Simplicity of design, installed redundancy, low speed motors,

integrated gear shaft and aerospace-quality hardware are incorporated into

each assembly design to ensure reliable operation and greater than i00,000

hours of operation.

FLIGHT EXPERIMENT OBJECTIVE/SCOPE

The overall objective of the EPICS flight experiment is to investigate how a

low-C environment may improve water electrolysis performance by experimenting

with various cell components of different microstructural characteristics,

fluid flows, current densities and thermal conditions within the cell. The

results will be used to improve static feed electrolysis process efficiency

for propulsion, energy storage, life support, EVA, in-space manufacturing

activities and in-space science activities.

Specific objectives of the experiment include:

I . Investigate the impact on cell performance of varying electrode

characteristics, porosity and thickness, in low-G.

. Evaluate performance improvement in low-G over a range of current

densities.

J Develop flight experiment hardware which is easily adaptable to

other electrochemical research activities.

5. Develop flight experiment hardware which is safe and reliable.

. Develop flight experiment hardware which requires minimal

interaction by the crew, yet provides for means of positive

intervention to enhance experiment success if necessary.

1 Develop flight experiment hardware which requires minimal National

Space Transportation System (NSTS) integration efforts.

8. Bring attention to the concept of using low-G as a local resource.

JUSTIFICATION FOR CONDUCTING EPICS EXPERIMENT

The SFE technology is very important to meeting NASA mission needs/goals as

illustrated in Figure 9. Hydrogen and Oxygen are key to the survival of

humans in deep space and the technology is key to a Hydrogen/Oxygen based

economy.

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It is hypothesized that the low gravity environment will improve the performance of the SFE. This improvement would be a result of eliminating the

effects of gravity on the electrolyte fluid distribution and electrolyte

density distribution. (Further analysis of thls is described in this report

in the sectlon entitled Analytical and Experiment Results.) Also, it should

be noted, that demonstration of an improvement in performance of this

electrochemical process would indicate, by correlation, definite improvement

possibilities in the performance of other electrochemical processes. This

impact will be very significant in view of the fact that electrochemical

process technology wlll be a key to the industrialization of space.

The use of parabolic aircraft flights would not provide sufficient periods of

low gravity environment for this investigation (25 to 30 seconds). As

described previously, years of design effort and thousands of hours of testing

in a one-G environment have been performed on the SFE technology to arrive at

an efficient and reliable design applicable to manned space missions. The

effects of low gravity on fluid flows and two phase systems have been analyzed

and conservatively accounted for within the design of the SFE. Tests have

also been performed on the hardware in several orientations to ensure that

orientation has no noticeable effect on the operation. The result is a design

which w111 perform reliably and efficiently, but does not incorporate the

performance improvement factor of operating in low-G. The use of low gravity

to enhance performance of the SFE must be demonstrated and investigated in a

low gravity environment before mission planners will incorporate the benefits.

An example of the potential benefits/payoffs of SFE technology performance

improvement is given by considering a lunar base advanced mission scenario,

where On is to be produced to meet the propellant requirements of advanced

z

space exploration missions. The On propellant production requirement is l,O00

tons per year for this scenario. _n electrolysis performance improvement of

only 0.01V per cell would result in a savings in power generation capacity of

approximately 4 kW for this scenario's 02 production requirement. A voltage

improvement of 0.02 V per cell would result in a savings of almost 8 kW. The

improvement in performance can be realized as a savings in power generation

capacity as described or as a savings in launch mass and volume, depending on

the more critical design driver, i.e., if a nuclear power source is available,

then launch mass and volume would be more important than power.

Interrelationship to Other Organizations

Development of the SFE technology has been a multi-agency effort. Figure I0

outlines the relationship of the technology development to the NASA

organizations as well as other organizations involved. Also provided in

Figure I0 is a listing of organizations which have supported the development

of the static feed water electrolysis technology.

TECHNICAL DESCRIPTION OF EPICS FLIGHT EXPERIMENT

The first part of this section describes the design objectives for the EPICS

and some general characteristics that apply to the overall experiment.

Subsequent sections describe the results of the design effort in terms of the

two primary hardware assemblies: The Mechanical/Electrochemical Assembly

(M/EA) and the C/M I.

15
Syst , IHc.

SFE Technology

National

Research

Council of

Canada

Power

National

Aeronautics

and Space

Administration

Power

• Propulsion

• Life Support

• EVA

• In-Space Manufacturing

• In-Space Science

Department

of

Energy

Power

Department

of

Defense

Power

• Propulsion

• Life Support

• EVA

ORGANIZATIONS SUPPORTING AND/OR HAVE SUPPORTED OUR WATER

ELECTROLYSIS TECHNOLOGY DEVELOPMENT

• NASA Johnson Space Center, Propulsion and Power Division

• NASA Johnson Space Center, Crew and Thermal Systems Division

• NASA Lewis Research Center

• NASAAmes Research Center

° Boeing Aerospace Company

• TRW, Inc.

• Rocketdyne Division of Rockwell International

• Department of Energy (Via Brookhaven National Lab.)

• Defense Advanced Research Projects Agency (Via U.S. Navy)

• National Research Council (NRC) of Canada

• Life Systems, Inc.

FIGURE i0 INTERRELATIONSHIP OF EPICS EXPERIMENT TO NASA AND OTHER AGENCIES

16
£i/e SHstems,Juc.

Overall Experiment Design

The overall experiment design is shown pictorially in Figure II and

schematically in Figure 12. The M/EA contains the integrated electrolysis

units and all supporting pressure and temperature control components. The

C/M I controls all operations of the M/EA and provides for monitoring and

control of critical parameters and storage of data. Therefore, as shown in

Figure 12, these two assemblies are interactive.

Table I lists general objectives for the design of the EPICS. The design

specifications for the EPICS is given in Table 2. Fluid interfaces/resources

of the EPICS hardware are defined in Table 3. Interfac_5ac_om_gdations and

safety requirements were defined in NSTS documentation. _ ' '

The EPICS has three different operating modes, as illustrated in Figure 13 and

defined in Table 4. Three different transitions between the operational modes

are permissible and are programmed into the C/M I.

Mechanical/Electrochemical Assembly

The M/EA of an EPICS experiment is illustrated in Figure 14 and schematically

shown in Figure 15. The weight, power and volume characteristics are listed

in Table 5. The functions of the various components are illustrated in

Figure 15 and described here. Three Integrated Electrolysis (IE) units are

enclosed in a Pressure Control/Safety Enclosure (PCSE). The IE units are

thermally controlled using a heat pipe and heater configuration• Waste heat

from the IE units is rejected to the heat pipe, which then rejects it to the

circulating Np atmosphere within the PCSE. The heater transfers heat via the

heat pipe to _he electrolysis cell prior to start-up. Product gas pressures

are controlled by direct interface between the PCSE and the product gas

accumulators• The feed water is continuously replenished through automatic

recombining of the product gases. No additional feed water, other than that

contained in the original electrolyte, is needed. The manual valves are used

during preparation of the IE units and are closed and capped off prior to

flight.

The subsystem components are described in greater detail below.

Integrated Electrolysis Unit

A single IE unit is shown in Figure 16 with an exploded view of an IE unit

shown in Figure 17. The major components of the IE unit include the

following:

I • The electrolysis cell integrated with the oxygen/hydrogen

recombiner.

2. The thermal control plate.

3. The oxygen and hydrogen accumulators.

17
THIS PAGEINTENTIONALLYLEFTBLANK
_fc SHstcms. :#c

Pressure Control/Safety

rated Current Controller

Integrated Electrolysis

Control/Monitor

----Instrumentation

Characteristics

weight_, Ib - _16

Volume, ft 1.9

Power, W ' 100

FIGURE 11 EPICS EXPERIMENT PACKAGING CONCEPT

18
THIS PAGE INTENTIONALLY LEFT BLANK
__ $_stems.Jttc

EPICS

Mechanical/

Electrochemical

Assembly

Input Power

Command Signals

Cooling Air

Control

Signals

and Power

for Sensors/

Actuators

and Module

V

Control/Monitor

Instrumentation

and

Data Storage

Sensor

Signals

I

I

I

I

I

1

External Signals

Data

Cooling Air

FIGURE 12 EPICS INTERFACE BLOCK DIAGRAM

19
TABLE 1 EPICS GENERAL DESIGN OBJECTIVES

Independent operation, requiring only electrical energy, and cooling air

Eliminate all variables except those being investigated

Fail-Safe Operation

Three Levels of Containment

Automatic Operation

C/M I Package Separately within Locker

Computer Based Instrumentation with Data Storage Capability

Shelf Life of up to 6 months

Compatible with Low, Partial and loG testing

Compatible with Standard Middeck Payload Requirements

Weight - less than 54 Ib

Power - less than 115 W (maximum continuous DC)

Power - none during ascent/descent

Heat Rejection - Heat Pipe/Air cooling

Does not require late installation

Does not require early removal

All materials Flight Qualifiable

2O
8ystms,JHc.

TABLE 2 EPICS DESIGN SPECIFICATION

Vehicle Data

Middeck Total Pressure, psia

Middeck Temperature, F

Nominal Operating Conditions

Number of Units

Number of Cells/Unit

Current Density, ASF

Operating Pressure, psia

Operating Temperature, F

Touch Temperature, F

Coolant Source

Type

Pressure, psia

Temperature, F

14.7 + 0.2

65 to 80

3

1

24-144

13.7 +_0.2

150+2

<113

Heat Pipe to Air

14.7 + 0.2

65 to 80

TABLE 3 EPICS INTERFACES

Interface/Resource

Water Supply

N 2 Supply

Coolant (air cooled)

Electrical Power

Data Acquisition/Storage

Crew Intervention/Operation

Tools

Source

Self-contained in experiment

Self-contained in experiment

Space Shuttle

Space Shuttle

Self-contained in experiment

Single on actuator of experiment by operator.

Crew intervention required only to enhance

experiment success if an anomaly occurs.

No tools required

21
TABLE

Mode (Code)

Shutdown (B)

Normal (A)

Unpowered (D)

4 EPICS OPERATING MODES AND UNPOWERED MODE DEFINITIONS

Definition

IE Units are at ambient temperature. Current is at zero. The PCSE is at 14.7 psia.

The experiment is powered and all sensors are working. The Shutdown mode is

called for by:

• Manual actuation

• Low IE Unit Cell Voltage

• High IE Unit Cell Voltage

• High IE Unit Temperature

• High PCSE Pressure

• High PCSE Temperature

• Power on reset from Unpowered Mode (D)

• Mode transition from Shutdown Mode (B) to Normal (A) was not successful

The IE Unit(s) are performing their function, as specified by the test sequence. The

unit(s) are at normal operating temperature. The Normal Mode is called for by:

• Automatic actuation

No electrical power is supplied to the EPICS. The Unpowered Mode is called for by:

• Manual actuation

• Electrical power failure

Normal

(A)

Unpowered

(D)

Shutdown

(g)

• 3 Modes

• 2 Operating Modes

• 5 Mode Transitions

• 3 Programmable, Allowable

Mode Transitions

FIGURE 13 EPIC'S MODES AND ALLOWABLE MODE TRANSITIONS

22
__ Systems.Juc

Pressure Control/Safety Enclosure

N 2 Atmosphere

Integrated Electrolysis Units

Thermal Control Blower

-- Cold Plate

FIGURE 14 EPICS MECHANICAL/ELECTROCHEMICAL ASSEMBLY

23
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24
SHstems.JHc

TABLE 5 EPICS CHARACTERISTICS

Item

No. Description

1 Integrated Electrolysis Unit

2 Blower

3 Combustible Gas Sensor

4 Pressure Sensor

5 Temperature Sensor

6 Pressure Control/Safety Enclosure

7 Integrated Current Controller

8 Control Monitor Instrumentation

9 Tray

10 Wiring

Total

Schematic Weight, Volume, Power, (a)

Symbol Qty. Ibs ft 3 W

IE1, IE2, IE3 3 15.6 0.6 36

B1, B2 2 0.6 0.0 7

CG1 1 1.0 0.0 3

P1 1 0.4 0.0 2

T4 1 0.2 0.0 1

PCSE 1 5.1 1.0 0

IEC 1 3.0 0.1 33

C/M I 1 7.2 0.2 18

- 1 4.5 0.0 0

- - 0.4 0.0 0

37.6 1.9 {hi 100

(a) Operation at peak current of 12 Amps per IE Unit, all three operational.

(b) Not additive.

25
_k 8Hstcms, JHc.

Electrochemical Cell Tabs

Electrolysis Cell Clear End-Plate --

Thermal Control Plate

Fabrication Manual Valve

Process Buffer Gas Accumulators

Integrated Electrolysis Cell

FIGURE 16 INTEGRATED ELECTROLYSIS (IE) UNIT

26
£ifc $_stcms,JHc.

Suppod Screen

H 2 Port

O-Ring

H 2 Port

O-Ring

H 2 Port

O-Ring

H 2 Port

I

Electrode Core Assembly

O_Passage

Suppo_ Screen

ThermalControIPlate

O2Po_

Assembly Valve

HJO 2Accumulators

FIGURE 17 EXPLODED VIEW OF IE UNIT

27
S tems, JHc

Three IE units, weighing approximately 5.2 ib each, having different electrode

configurations are included within the EPICS experiment. These electrode

configurations, as well as the other components of the IE unit, are described

in further detail below.

Electrolysis Cell - As described previously, the water electrolysis cells are

the heart of the static feed water electrolysis subsystem. Three

configurations of the electrolysis cell are included in the design of the

EPICS as described in Table 6. The IE Unit No. i configuration is that of the

baseline state-of-the-art SFE subsystem. The baseline configuration, as

described for IE Unit No. I, is an optimized configuration resulting from

one-G testing. The IE Unit Nos. 2 and 3 vary from the baseline configuration

to investigate a low-G optimum design.

TABLE 6 INTEGRATED ELECTROLYSIS UNIT CELL CONFIGURATIONS

Parameter

Matrix Thickness, mil

IE Unit No.

1 2 3

Baseline (0.67) Baseline Baseline

Electrode Thickness, mil Baseline Baseline Baseline

Pore Size, prn Baseline Baseline (0.5) Baseline

Porosity, % Baseline Baseline TBD

Thermal Control Plate - The Thermal Control Plate is used to maintain the

operating temperature of the electrolysis cell at 150 F and to provide heat

input during the startup of the experiment. Heat pipes are used to maintain

thermal control as shown in Figure 18. Variable conductance heat pipes, which

maintain isothermal conditions without the use of variable heat sink

requirements, i e., N_ flow across the condensing portion of the heat pipe,

• z

are also being considered. The Hughes Aircraft Company, who currently has a

Phase B Outreach Experiment related to heat pipe thermal performance and

working fluid behavior, has provided design information and data to the EPICS

experiment design program.

Oxygen and Hydrogen Accumulators - The cross-sectlon of the IE Unit given in

Figure 19 illustrates the accumulators design. The accumulators are

mechanical bellows which interface the higher pressure side of the bellows to

the nitrogen atmosphere in the PCSE. This provides a positive pressure

gradient from exterior to interior, eliminating the possibility of leakage of

O_ or H^ from the IE Unit. Prior to startup, the bellows are compressed and

t_e dea_ volume is minimized by design to minimize the amount of N 2 in the IE

28
_ 8Hstcms. JHc.

CAPILLARY

/

HEATIN HEAT OUT

Ref: Basiulis, A., Tanzer, H. and McCabe, S., "Thermal Management of High Power PWBs Through

the Use of Heat Pipe Substrates" Sixth Annual International Electronics Packaging Conference,

November 17-19, 1986,San Diego, CA.

FIGURE 18 TYPICAL CYLINDP, ICAL HEAT PIPE

1 I

S Electrolysis Cell

H2 Accumulator

L H2 Path efface

--Thermal Control Plate

/

_//////////////////_

_O 2 Path

Accumulator

FIGURE 19 CROSS SECTION OF IE UNIT

29
unit. During startup, 02 and H2 generation occurs without O2/H 2 recombination

until the accumulators are at t_eir full setpoint. This dilutes the amount of

N_ within the IE unit to an insignificant level. Bellow position sensors, YI

t_rough YI2, are used during startup to indicate that a specified amount of 02

and H 2 generation has been completed. When this setpoint is reached, the

O2/H p recombiner is automatically activated. Position sensors YI3 through Y24

are Included for safety and indicate a shutdown should be initiated if the

amount of 02 and/or H 2 is greater than the specified setpoint.

Pressure Control and Safety Enclosure

The PCSE is used to provide multiple functions, including: (I) pressure

control of the IE Units, (2) safety via a Np blanket and (3) a heat sink for

thermal control of the IE Units. The structure of the PCSE is made of Lexan

or similar, with the back wall being made of aluminum with fins for heat

rejection. Sealing of the PCSE joints to ensure that the N^ atmosphere is

maintained was evaluated. Two options for sealing the PcSEZare illustrated in

Figure 20. The PCSE interior pressure is 14.7 psia and the touch temperature

is <113 F.

Ancillary Components

The ancillary components consist essentially of two blowers and standard

temperature and pressure sensors. The first blower circulates the N^

atmosphere within the PCSE while the second blower circulates middec_

atmosphere through the locker, both of which are included for thermal control.

There are no solenoid valves, pumps or separators required in the EPICS

experiment. Tables 7 and 8 list the experiment actuators and sensors.

Control/Monltor Instrumentation

A microcomputer-based instrumentation hardware concept was selected to provide

for parameter control, automatic mode and mode transition control, automatic

shutdown for self-protection, monitoring and storage of subsystem parameters

and interfacing with data acquisition facilities. Also included in this

discussion is a description of the EPICS current controller, which controls

the current supplied to each of the IE Units. The C/M I and Current

Controller are illustrated in Figure 21. Figure 22 is a block diagram of the

interactive sections and interfaces of the C/M I, current controller, M/E A

and the middeck locker. A more detailed block diagram of the EPICS current

controller is given in Figure 23. Design characteristics for the C/M I and

Current Controller are listed in Tables 9 and I0.

C/M I General Description

The C/M I receives or transmits signals from or to the M/EA sensors and

actuators and the current controller. Through these signals it controls and

monitors flow rates, temperatures, voltages and currents in each operating

mode (shown in Figure 13 and described in Table 4). It implements each mode

as initiated automatically and provides fail-safe operational changes to

protect the mission and experiment if malfunctions occur.

30
$ tcms. JHc.

_Epoxy Join_Seal _O-Ring Groove

"_ /--Enclosure

Enclosu

FIGURE 20 PRESSURE CONTROL ENCLOSURE SEAL OPTIONS

TABLE 7 EPICS FLIGHT EXPERIMENT ACTUATOR LIST

No. Description Qty. Symbol

1 PCSE Fan 1 B1

2 Locker Fan 1 B2

3 Thermal Control Plate Heater 3 H1, H2, H3

4 Current On/Off 3 X11, X21, X31

5 Current Level 3 X21, X22, X23

11

Type

DC Motor

DC Motor

DC resistance

0 to 5 V Digital

0 to 5 V Analog

TABLE 8 EPICS FLIGHT EXPERIMENT SENSOR LIST

No. Description Qty. Symbol

1 Cell Voltage 6 E1 to E6

2 Cell Current 3 I1, 12, 13

3 Cell Temperature 3 T1, T2, T3

4 Enclosure Temperature 1 T4

5 Enclosure Pressure 1 P1

6 Combustible Gas Sensor 1 CG1

7 Accumulator Level 24 Y1 to Y24

Total 39

Type

Voltage Tabs

Shunt

RTD

RTD

Strain Gauge/Bridge

Catalyzed Bead

Hall Effect Switch

31
£i/c8Hstcms. Jnc.

Units and C/MI Interface

Sensors/Actuators and Current Controller Interface

Supply Interface

Acquisition Port

Integrated Current

Controller

C/MI

FIGURE 21 EPICS C/M I AND INTEGRATED CURRENT CONTROLLER PACKAGING

32
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r

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-- C

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"_: _.. _ __

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36
TABLE 9 EPICS C/M I ENCLOSURE CHARACTERISTICS

Size, in

Weight, Vol, Power,

No. Description Ib H W D in 3 W

1. Signal Conditioning

Excitation 0.2 0.75 4.75 4.75 16.9 3

Multiplexer 0.1 0.75 4.75 4.75 16.9 1

Signal Conditioning 0.1 0.75 4.75 4.75 16.9 1

A/D & Comp. I/F 0,1 0.75 4.75 4.75 16.9 2

Card Rack 0,6 3.0 5.0 5,0 75.0 -

2. Computer card 0.3 0.60 6.75 4.5 18.2 6

3, Power Supplies 1.3 2.5 3.0 2.2 16.5 2

4. Connectors/Wiring 0,6 - - - 12.0 -

5. Actuator Drive, Electronics 0.9 3.2 4.0 4.5 57.6 2

6. Data Storage 0.8 3 8 12 288 1

7. C/M I Enclosure 2.2 4 8 12 384 -

Total 7.2 4 x 8 x 12 384 18

(Envelope)

TABLE i0 EPICS INTEGRATED CURRENT CONTROLLER CHARACTERISTICS

Weight, Size, in Volume,

No. Element Qty. Ibs H W D in 3

1 Resonant Converter 6 0.94 3.0 7.5 1.7 38.4

2 Drive for Res. Conv. 6 0.12 1.2 1.5 1.3 2.4

3 Transformer 3 0.21 1.5 1.5 0.7 4.8

4 Rectifier Bridge 3 0.06 1.5 1.0 0.8 1.2

5 Control Board 1 0.20 3.7 7.7 0.5 14.2

6 Control Power Supply 1 0.10 1.0 1.0 0.3 0.5

7 Shunt 3 0.06 1.0 0.2 1.5 0.3

8 Relay 3 0.30 1.0 1.0 0.5 1.5

9 Enclosure 1 1.0 4 8 3 96

Total 3.0 4 x 8 x 3 96

(Envelope)

PowerS,)

LOSS, W

6.0

0.6

3.0

18.0

1.0

1.0

3.0

0

0

32.6

(a) Operation at peak current of 12 Amps per IE unit and all three IE Units operational.

35
Operating Mode Control includes sequencing of actuators and checking

parametric conditions as the transitions proceed. This procedure for control

is fully automated by the C/M I so that the operator only needs to press the

mode transfer request button to initiate startup or shutdown.

Experiment Control - Control algorithms/concepts were defined for specific

subsystem parameters and sequences. The IE Unit current and temperature are

controlled to preset values using closed loop, feedback controls.

Subsystem Monitorin_ - Critical EPICS experiment parameters were selected for

monitoring and data storage to provide for automatic shutdown and

self-protectlon. These parameters are given in Table ii for the normal

operating mode. Shutdown levels were selected for above and/or below nominal

operating values. Parameter values which are stored in the data storage

capability of the C/M I are listed in Table 12.

ANALYTICAL AND EXPERIMENTAL RESULTS

The results of prior analytical and experimental efforts have been

incorporated into the design of an SFE capable of reliable and efficient 02

and H 2 generation for space missions. The EPICS experiment is designed to

further investigate ways by which a low gravity environment may improve water

electrolysis performance by experimenting with various cell components of

different microstructural characteristics, fluid flows, current densities and

thermal conditions within the cell as the electrode core components are key to

the performance of the SFE.

One-G experimental results provided the information required to design an SFE

which maintains proper gas/electrolyte interfaces in the cathode and the anode

of the electrode core. In this context, properly refers to the one-G design

which maintains an electrolyte distribution which balances the resistances for

optimum performance. The optimum design is one which has a uniform

distribution of electrolyte and electrolyte composition across the entire area

of the electrode core. Uniform composition and depth of electrolyte along an

entire electrode area would provide even resistance to gas and liquid

diffusion, even electrical resistance and consequently result in optimum

performance.

Figure 24 illustrates the gravity effects on the gas/liquid interface/

electrolyte distribution in a cross section of the electrode core. The

illustration magnifies the electrode core to make the individual pores of the

cathode, matrix and anode visible. As illustrated, there will be a range of

pore sizes throughout each section of the core, i.e., cathode, matrix and

anode. The matrix will have much smaller pores than either the cathode or

anode, whose pores have similar pore size range. The capillary force of the

smaller pores will be greater than that of the larger pores. The capillary

forces of the larger pores may not be strong enough to completely counteract

the force of gravity in one-G. This is seen in the illustration in circle A,

where the electrolyte only partially fills the cathode and anode pores,

compared to the complete filling of the same size pore in circle B. Circles C

and D illustrate the same pores magnified in a 0-G condition. In the latter

case, the capillary effects are not resisted by gravity and there is an even

36
$ zcms.JHc

TABLE II EPICS SHUTDOWN PARAMETERS

Parameter

Cell Voltage

PCSE Pressure

Accumulator Level

IE Temperatures

PCSE Temperature

Combustible Gas Sensor

Shutdown Level

Low High

v' v'

v'

v'

i/ v'

v'

v'

TABLE 12 EPIC DATA STORAGE PARAMETERS

Parameter

IE Cell Voltage

IE Cell Current

IE Cell Temperature

PCSE Temperature

PCSE Pressure

No. Sensors

3

3

3

1

1

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electrolyte distribution. A density gradient-caused convection of electrolyte

can also exist in a one-G environment, which will not exist in a 0-G

environment. Eliminating both of these gravitational effects in 0-G should

improve performance as shown in Figure 25.

Performance is projected to be improved in two ways. One will be a decrease

in cell voltage, resulting in savings in power. The other will be an increase

in the operational range of current density, resulting in improved operation

flexibility.

O

Operation

Flexibility

Improvement

I

I

i I

Existing Current Density Range I I

/ I Performance

mpr°iement

• I

I

I I

i I

Increased Current Density Range

I

I

I

I

Current Density

FIGURE 25 PROJECTED SFE PERFORMANCE IMPROVEMENTS OF O-G ENVIRONMENT

39
Design Safety Analysis

Following are the results of the design safety analysis performed throughout

the preliminary conceptual design program and incor_9_ated into the EPICS

design. The NSTS Safety Requirements documentation'-" was referred to

throughout the analyses.

I .

2.

3.

.

.

.

7.

8.

9.

i0.

Product gas ports are separated and isolated.

Temperature sensing with shutdown protection.

Positive differential pressure from exterior to interior of the IE

unit by the accumulator bellows.

Three levels of containment including O-rings, N 2 blanket and

pressure control/safety enclosure.

Product gas accumulators are separated by a solid metal and the

assembly valve interfaces are on opposite ends of the unit.

Pressure fluctuations eliminated by the bellows.

Accumulator level sensing with shutdown protection.

All product gases are contained within the IE unit.

Over-temperature protection is included with the thermal control

plate heater.

Product gas volumes are minimized.

Design Reliability Analysis

Following are the results of the design reliability analysis performed

throughout the preliminary conceptual design effort.

I.

2.

3.

4.

5.

6.

7.

Multiple IE units included.

Last minute IE unit replacement procedure.

Elimination of all solenoid valves, pumps and separators.

Long-term database on materials of construction.

Low operating pressure (ambient pressure).

Accumulator uses metal bellows construction.

Few ancillary components to reduce complexity.

INITIAL COST AND SCHEDULE ASSESSMENTS

An initial assessment of the EPICS experiment cost and schedule is given in

Table 13. This assessment covers the period beginning from initiation of the

final design through the flight readiness review and launch.

Implementation Plan

Figure 26 provides an initial payload development and integration schedule for

the EPICS experiment. The schedule contains tasks performed by the Space

Transportation System, the payload supplier and joint activities. The overall

schedule is 24 months_8)The NSTS Shuttle/Payload Standard Integration Plan for

Middeck-type Payloads a_the Implementation Procedure for STS Payloads

System Safety Requirements" " were used as guidelines during the development

of this preliminary plan. Figure 27 provides a flow diagram of the payload

integration process.

40
Syst s,Juc.

TABLE 13 INITIAL ASSESSMENT OF EPICS COSTS AND SCHEDULE

Task Description

Final Design

Phase 0 Safety Review

Preliminary Design Review

Phase I Safety Review

Critical Design Review

Phase II Safety Review

Fabrication

Purchase Materials

Configuration Management

Quality Assurance

Assembly

Engineering Analyses

Loads Analysis

Thermal Analysis

EMI/EMC Analysis

Testing, Quafification

Design Verification

Certification

Acceptance

Interface Verification

Documentation-Interface

Payload Integration Plan

Payload/STS ICD

PIP Annexes-1,2,3,6,7,8,9

Cost, $ K Duration, Months

20O 8

2OO 7

30 11

5O 6

25 5

Total 505 24 _a)

(a) Not additive since periods overlap.

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[

ENGINEERING i

DESIGN

& ANALYSES

PiP ANNEXES

PAYLOAD

STRUCTURAL &

THERMAL MODELS

Ref: NSTS 07700, Volume XIV, Space Shuttle System Payload Accommodations, Revision J, 01/27/88

FIGURE 27 PAYLOAD INTEGRATION PROCESS

43
Preliminary Flight Test Plan Overview

A preliminary top level Test Plan for the EPICS experiment has been developed

and summarized in Figure 28. All sequences will be controlled automatically

by the C/M I.

Day 1

Current, A 2

Unit No. I, hrs. 10

Unit No. II, hrs. 10

Unit No. III, hrs. 10

2 3 4 5

3 5 8 12

t0 10 10 10

10 10 10 10

10 10 10 10

U0..

E

I160

150 -

140 -

130 -

120 -

110 - ,"

100 ,"

O' I

0 1

Normal Operation:

Transition: ......

#

t

t #

#

I

I t

I

i I

I I 1 I I I I 1 I I

2 3 4 5 6 7 8 9 10 11

Time, hr

Note: Each 10 hr period consists of three 3-hr periods with

two one-half-hr periods between them.

FIGURE 28 PRELIMINARY FLIGHT TEST PLAN FOR EPICS EXPERIMENT

44
 fe 8Hstems. JHc.

CONCLUSIONS

The following conclusions were reached based upon the EPICS experiment

conceptual design efforts:

I. An Electrolysis Performance Improvement Case Studies (EPICS)

experiment is required to investigate ways a low gravity environment

may improve water electrolysis performance.

, The results of an EPICS experiment will be used to improve static

feed electrolysis (SFE) process efficiency for propulsion, energy

storage, life support, EVA, in-space manufacturing activities and

in-space science activities.

. The EPICS experiment is capable of meeting all design requirements/

constraints of a standard middeck payload.

, The EPICS experiment will require minimum crew interface for nominal

operation. All modes and mode transitions, parameter monitoring and

data storage will be performed automatically by the payload supplied

C/M I.

. The incorporation of certain safety features (O-rings, nitrogen

blanket and Pressure Control/Safety Enclosure) meet the NSTS three

levels of containment requirement without adding any significant

weight, power or volume penalties to the experiment design.

. The experiment has been defined with a minimum number of moving

components to increase reliability.

REFERENCES

i. Schubert, F. H.; Lantz, J. B. and Hallick, T. M., "Development of a

Static Feed Water Electrolysis System," Final Report, Contract

NAS2-I0306, CR-166142, Life Systems, Inc., Cleveland, OH;

January 1982.

o Schubert, F. H.; Lee, M. K.; Davenport, R. J. and Quattrone, P. D.,

"Water Electrolysis Systems: H_ and O_ Generation," Paper No

Z

78-ENAs-3, Intersociety Conference on _nvironmental Systems, San

Diego, CA; July 10-13, 1978.

o Schubert, F. H.; Wynveen, R. A. and Jensen, F. C., "Development of

an Advanced Static Feed Water Electrolysis Module," Paper No.

75-ENAs-30, Intersociety Conference on Environmental Systems, San

Francisco, CA; July 21-24, 1975.

, Schubert, F. H. and Wynveen, R. A., "Technology Advancement of the

Static Feed Water Electrolysis Process," Final Report, Contract

NAS2-8682, CR-152073, Life Systems, Inc., Cleveland, OH; November,

1977.

45
o

o

o

,

,

Shuttle/Payload Interface Definition Document for Middeck Accommodations, NSTS 21000-1DD-MDK, March, 1988.

Space Shuttle System Payload Accommodations, NSTS 07700, Volume XIV,

Revision V; January, 1988.

Safety Policy Requirements For Payloads Using the Space Transportation System, NHB 1700.7A.

Shuttle/Payload Standard Integration Plan for Middeck-Type Payloads,

NSTS-2100-SIP-MDK, Revision A; December, 1988.

Implementation Procedure for STS Payloads System Safety Requirements,

JSC 13830A; May, 1983.

46