August 1998

Compression Distillation/Urine ProcessingAssembly (VCD/UPA) at the MarshallSpace Flight Center (1993 to 1997)

P. Wieland, C. Hutchens, and D. Long

Marshall Space Flight Center, Marshall Space Flight Center, Alabama

B. Salyer

Ion Electronics, Huntsville, Alabama
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i

NASA/TM—1998–208539

Final Report on Life Testing of the Vapor

Compression Distillation/Urine Processing

Assembly (VCD/UPA) at the Marshall

Space Flight Center (1993 to 1997)

August 1998

National Aeronautics and

Space Administration

Marshall Space Flight Center

P. Wieland, C. Hutchens, and D. Long

Marshall Space Flight Center, Marshall Space Flight Center, Alabama

B. Salyer

Ion Electronics, Huntsville, Alabama
ii

Available from:

NASA Center for AeroSpace Information National Technical Information Service

800 Elkridge Landing Road 5285 Port Royal Road

Linthicum Heights, MD 21090–2934 Springfield, VA 22161

(301) 621–0390 (703) 487–4650
iii

TABLE OF CONTENTS

 1. INTRODUCTION AND BACKGROUND OF LIFE TESTING .......................................... 1

 2. VCD/UPA PROCESS AND HARDWARE DESCRIPTION ................................................. 2

 2.1 VCD Process ............................................................................................................. 2

 2.2 Hardware Description and Similarity with the ISS UPA ........................................... 3

2.2.1 VCD Hardware ............................................................................................... 3

2.2.1.1 Wastewater Storage Assembly ......................................................... 5

2.2.1.2 Fluids Control Assembly ................................................................. 5

2.2.1.3 Fluids Pump Assembly .................................................................... 5

2.2.1.4 Distillation Assembly....................................................................... 6

2.2.1.5 Recycle Filter Tank Assembly ......................................................... 7

2.2.1.6 Pressure Control Assembly .............................................................. 9

2.2.1.7 Purge Pump Assembly ..................................................................... 9

2.2.1.7.1 Harmonic Drive ........................................................... 10

2.2.1.8 Instrumentation and Monitoring ...................................................... 11

2.2.2 Flight-like Components.................................................................................... 11

 2.3 Upgrades from Previous VCD’s................................................................................. 12

2.3.1 VCD–5 History ................................................................................................ 14

2.3.2 VCD–5A History.............................................................................................. 14

 3. TEST FACILITY DESCRIPTION ......................................................................................... 16

 4. TEST DESCRIPTION AND PERFORMANCE .................................................................... 18

 4.1 Test Purpose ............................................................................................................... 18

 4.2 Operating Procedures ................................................................................................. 18

 4.3 Components Tested .................................................................................................... 18

 4.4 VCD–5 Testing........................................................................................................... 18

4.4.1 VCD–5 Test Events and Anomalies ................................................................. 21

4.4.1.1 VCD-5 Troubleshooting .................................................................. 23

4.4.2 VCD–5 Performance During the WRT Stage 10 ............................................. 25

4.4.2.1 VCD-5 Operation During WRT Stage 10 ........................................ 25

4.4.2.1.1 Software/Firmware Changes ....................................... 27

4.4.2.1.2 Motor Speed Controller ............................................... 27

4.4.2.1.3 Vespel® Gear Replacement .......................................... 27

4.4.2.1.4 Calculation of the Percentage of Solids in the RFTA .. 27

4.4.2.1.5 High Temperatures and Pressures in the Still .............. 28

4.4.2.1.6 High Conductivity Alarms ........................................... 32

4.4.2.1.7 Purge Pump Failure ..................................................... 33

4.4.2.1.8 Recycle/Filter Tank...................................................... 34
iv

4.4.2.2 VCD–5 Performance........................................................................ 34

4.4.2.3 VCD–5 Product Water Quality ........................................................ 35

4.4.2.4 VCD–5 Conclusions and Recommendations from the

 WRT Stage 10 ............................................................................... 36

 4.5 VCD–5A Testing ........................................................................................................ 37

4.5.1 VCD–5A Test Events and Anomalies .............................................................. 42

4.5.2 VCD–5A Field Service .................................................................................... 45

4.5.3 VCD–5A Operation Summary ......................................................................... 52

4.5.4 Proposed Modifications ................................................................................... 52

 5. TEST RESULTS AND LESSONS LEARNED...................................................................... 53

 5.1 General Results and Lessons Learned ....................................................................... 53

5.1.1 Variation of Production Rate ............................................................................ 54

5.1.2 Wastewater Supply ........................................................................................... 55

5.1.3 Instrumentation and Valve Failures.................................................................. 55

5.1.4 High Conductivity of Product Water................................................................ 55

5.1.5 Materials........................................................................................................... 55

5.1.6 Leakage ............................................................................................................ 56

5.1.7 Harmonic Drive Failure ................................................................................... 56

 5.2 VCD–5 Test Results ................................................................................................... 56

5.2.1 Wastewater Supply Tank .................................................................................. 56

5.2.2 Fluids Pump ..................................................................................................... 56

5.2.3 Purge Pump ...................................................................................................... 56

5.2.4 Distillation Assembly ....................................................................................... 57

5.2.5 Recycle Filter Tank .......................................................................................... 57

5.2.6 Gas/Water Separator......................................................................................... 57

 5.3 VCD–5A Test Results ................................................................................................ 58

5.3.1 Wastewater Supply Tank .................................................................................. 58

5.3.2 Fluids Pump ..................................................................................................... 58

5.3.3 Purge Pump ...................................................................................................... 58

5.3.4 Distillation Assembly ....................................................................................... 58

5.3.5 Recycle Filter Tank .......................................................................................... 59

5.3.6 Gas/Water Separator......................................................................................... 59

 6. CONCLUSIONS AND RECOMMENDATIONS .................................................................. 60

 6.1 Design ........................................................................................................................ 60

 6.2 Quality Control .......................................................................................................... 60

 6.3 Materials..................................................................................................................... 61

 6.4 Operation.................................................................................................................... 61

 7. REFERENCES AND BIBLIOGRAPHY ............................................................................... 62

 7.1 References .................................................................................................................. 62

 7.2 Bibliography............................................................................................................... 63
v

LIST OF FIGURES

 1. Schematic of VCD process ....................................................................................................... 3

 2. Photograph of the VCD–5 ........................................................................................................ 4

 3. Photograph of the VCD–5A ..................................................................................................... 4

 4. Schematic of VCD hardware and instrumentation ................................................................... 5

 5. Peristaltic pump design concept and operation ........................................................................ 6

 6. VCD distillation assembly schematic ....................................................................................... 7

 7. VCD/UPA RFTA disassembled (showing single filter configuration) ..................................... 8

 8. VCD/UPA filters (top: 25 μm pore size, bottom: 10 μm pore size) ......................................... 8

 9. Purge pump design concept and connections ........................................................................... 9

10. Harmonic Drive ........................................................................................................................ 10

11. ECLS test facility at MSFC ...................................................................................................... 16

12. Schematic of the ECLS test facility at MSFC .......................................................................... 17

13. EEF urinal ................................................................................................................................. 17

14. Gantt chart of VCD–5 operation............................................................................................... 19

15. VCD–5 typical compressor temperature (T1) .......................................................................... 19

16. VCD–5 typical compressor motor current (I1)......................................................................... 20

17. VCD–5 typical condenser pressure (P1) .................................................................................. 20

18. VCD–5 10 μm pore size filter used during WRT Stage 10 ...................................................... 28

19. VCD–5 compressor outlet temperature (WRT Stage 10 test days 11 and 12).......................... 29

20. VCD–5 condenser pressure (WRT Stage 10 test days 11 and 12)............................................ 29

21. VCD–5 compressor outlet temperature (WRT Stage 10 test days 40 and 41) ......................... 30

22. VCD–5 condenser pressure (WRT Stage 10 test days 40 and 41) ........................................... 30

23. VCD–5 compressor outlet temperature (WRT Stage 10 test days 68 and 69) ......................... 31

24. VCD–5 condenser pressure (WRT Stage 10 test days 68 and 69) ........................................... 31

25. VCD–5 calculated condenser temperature (WRT Stage 10 test days 68 and 69) .................... 32

26. VCD–5 product water conductivity and pH ............................................................................ 33

27. VCD–5 product water production rate during WRT Stage 10.................................................. 35

28. VCD–5 product water carbon composition during WRT Stage 10 .......................................... 36

29. Gantt chart of VCD–5A operation ............................................................................................ 37

30. VCD–5A typical compressor temperatures (T1) ...................................................................... 38

31. VCD–5A typical motor current (I1) ......................................................................................... 38
vi

32. VCD–5A typical condenser pressures (P1) .............................................................................. 39

33. VCD–5A product water conductivity ....................................................................................... 39

34. VCD–5A 25 μm pore size recycle filter performance .............................................................. 42

35. Facility vacuum connection to the purge and fluids pumps ..................................................... 45

36. VCD–5A current, temperature, and pressure profiles in November 1995 ............................... 46

37. VCD–5A end plate showing light corrosion............................................................................. 47

38. VCD–5A distillation drum spokes showing light corrosion ..................................................... 47

39. VCD–5A wastewater injection tube and product water pickup tube....................................... 48

40. VCD–5A disassembly showing old compressor gears ............................................................. 49

41. VCD–5A compressor temperature (T1) after repairs in January 1996 ..................................... 50

42. VCD–5A compressor motor current (I1), condenser pressure (P1), and

 compressor differential pressure (P2) after repairs in January 1996 ....................................... 51

LIST OF TABLES

 1. History of the use of Harmonic Drives in VCD’s..................................................................... 11

 2. Harmonic Drive operating history (as of May 25, 1993) ......................................................... 11

 3. VCD–5 and VCD–5A instrumentation list ............................................................................... 12

 4. VCD–5 and VCD–5A flight-like characteristics ...................................................................... 13

 5. VCD–5 product water and brine compositions ........................................................................ 21

 6. VCD–5 significant events and anomalies ................................................................................. 24

 7. VCD–5 key events during WRT Stage 10 ................................................................................ 26

 8. VCD–5 inputs and outputs during WRT Stage 10.................................................................... 26

 9. VCD–5 recycle/filter tank cleaning/filter replacement during WRT Stage 10 ......................... 34

10. VCD–5 product water quality during WRT Stage 10 ............................................................... 36

11. VCD–5A product water and brine compositions ...................................................................... 40

12. VCD–5A wastewater processed between filter replacements .................................................. 41

13. Purge gas test wastewater processing ....................................................................................... 43

14. VCD–5A significant events and anomalies .............................................................................. 43

15. VCD component lifetimes ........................................................................................................ 53

16. Average processing rate calculations ........................................................................................ 54

LIST OF FIGURES (Continued)
vii

ABBREVIATIONS, ACRONYMS, AND DEFINITIONS

> leads to (as in “T1 high alarm > shutdown”)

greater than (as in “K1 > 250 μmho/cm”)

< less than

A amperes of current

alarm (v.) Signifies that a sensor has entered an intolerable operating range and the VCD/UPA

will begin a transition to the shutdown mode automatically.

CHeCS Crew Health Care System

CL1 Sensor that provides information on the solids content of the brine.

Control/Monitor The electronic instrumentation that monitors and controls the subsystem. It consists

 Instrumentation of a signal conditioner, a controller, and a motor speed controller.

DA distillation assembly—The distillation assembly is a highly integrated mechanical

assembly that enables the evaporation of water from a flowing wastewater stream,

provides condensation of water vapor to form product water, and provides liquid/

vapor separation in microgravity. The DA consists of the DU, motor and drive

components, and ancillary components such as a heat exchanger, sensors, and

connectors.

dc direct current

DU distillation unit—The centrifuge component of the DA, including the compressor.

ECLS Environmental Control and Life Support

ECLSS Environmental Control and Life Support System

EEF End-use Equipment Facility—The room containing exercise equipment, washing

facilities, and a urinal for generating wastewater for processing.

EPROM Erasable Programmable Read Only Memory (computer firmware)

FCA fluids control assembly—The fluids control assembly manages and directs the flows

of waste feed, waste recycle, and product water.

FPA fluids pump assembly—Pumping of wastewater to the distillation assembly and

pumping of both concentrated wastewater and product water from the distillation

assembly is accomplished by a multipath, single motor fluids pump assembly.

Harmonic Drive the manufacturer of the fluids pump and purge pump drive mechanisms

hr hour(s)

in. inches

ISS International Space Station

ISS UPA VCD that will be used on board the USOS of the ISS
viii

K1 VCD–5 product water conductivity sensor

L1 liquid level sensor in the distillation unit

LSI Life Systems, Inc.—manufacturer of the VCD

μm micrometer or micron

μmho/cm measurement of water conductivity

min minute(s)

mm millimeters

N/A not available

Normal see Operating Modes

Norprene Material of the peristaltic pump tubing, a registered trademark of the Norton

Performance Plastics Corporation.

Operating Modes The four operating states of the VCD/UPA are:

Normal—The VCD/UPA recovers water from wastewater.

Standby—The VCD/UPA is waiting for sufficient pretreated urine and urinal flush

water to accumulate in the wastewater storage assembly before automatically

transitioning to the normal mode.

Unpowered—The VCD/UPA is unpowered and all sensors and actuators are

deenergized.

Shutdown—The VCD/UPA is not receiving or recovering water, all actuators are

deenergized and all sensors are functioning.

PACRATS Payloads and Components Real-time Automated Test System—data acquisition

system used during the WRT Stage 10.

PCA pressure control assembly—The primary function of this component is to

periodically purge the distillation assembly of noncondensable gases that enter as

dissolved or free gases with the wastewater feed. As noncondensable gases increase

in the distillation assembly condenser, the pressure will increase. The pressure

control assembly monitors this pressure increase and enables the purge pump

assembly when a purge is, required. The purge pump assembly pumps the

noncondensable gas with steam to pressures above ambient. From there, the

noncondensable gas and steam condensate pass through a membrane gas/water

separator where product water condensate is recovered from the noncondensable gas

and routed back into the product water stream. The noncondensable gases are

released to the atmosphere.

PDU performance display unit—An element of the test support accessories that simulates

the higher level command interface to the ECLSS subsystem. It provides an interface

to enable monitoring of the hardware performance and high level commands.

POST Predevelopment Operations Systems Test

Power Distribu- An element of the test support accessories that provides the interface between the

 tion and Control facility power and the subsystem.

Assembly
ix

PPA purge pump assembly—The purge pump assembly provides the pumping necessary

to purge noncondensable gases from the distillation assembly condenser to

atmosphere.

Q1 sensor measuring the bellows position in the wastewater supply tank

RFTA recycle filter tank assembly—The accumulation and filtering of concentrated

wastewater brine is performed in this assembly. In addition, it provides a

containment vessel for storing and transporting the concentrated brine during flight

tank resupply.

rpm revolutions per minute

S4 still drum speed sensor

SCATS Systems and Components Automated Test System—computerized data collection

and monitoring system.

Shutdown see Operating Modes

Standby see Operating Modes

Test Support devices that simulate the interfaces to the VCD

Accessories

TIC total inorganic carbon

TOC total organic carbon

Unpowered see Operating Modes

UP urine processor

UPA urine processing assembly

USOS United States on-orbit segment of the ISS

VCD/UPA vapor compression distillation/UPA

VCD–5 one of the VCD’s used for life testing (sometimes referred to as the VCD–V)

VCD–5A one of the VCD’s used for life testing (sometimes referred to as the VCD–VA)

Vdc Volts, direct current

Vespel the composition of one of the compressor gears, to provide lubrication, a registered

trademark of the DuPont Company

warning (v.) signifies that a sensor has entered a range that indicates an unusual operating

condition that may soon lead to an alarm condition

WP water processor

WRT water recovery test

WSA wastewater storage assembly—Storage of wastewater is performed by this

component. By monitoring the quantity of wastewater in the storage tank, this

assembly will initiate automatic startups and shutdowns of the VCD.
1

TECHNICAL MEMORANDUM

FINAL REPORT ON LIFE TESTING OF THE VAPOR COMPRESSION

DISTILLATION/URINE PROCESSING ASSEMBLY (VCD/UPA)

AT THE MARSHALL SPACE FLIGHT CENTER (1993 TO 1997)

1. INTRODUCTION AND BACKGROUND OF LIFE TESTING

Life testing of selected Environmental Control and Life Support System (ECLSS) equipment

began in 1992 after it was determined by Marshall Space Flight Center (MSFC) personnel that adequate

life testing was not being conducted by International Space Station (ISS) hardware developers. Testing

of qualifiable hardware by Boeing (the prime contractor) would not precede its launch; therefore, it

would not be possible to determine design problems early enough to prevent ISS ECLSS startup

difficulties. Life testing enabled identification of design problems in time to improve the flight

hardware. Specific objectives of the life test program were:

“1. To develop a knowledge base for design requirements and criteria which affect logistics and

reliability.

2. To minimize hardware development risk by providing long-duration operational histories at

space station operating conditions and making the data obtained during the course of the test

immediately available to the prime contractor and its hardware vendors so that the flight

design can take advantage of the lessons learned and make the appropriate design changes to

ensure a highly reliable ECLSS.

3. To determine specific component life characteristics and to understand their failure

mechanisms for space station ECLSS hardware designs.”1

The purpose of the Vapor Compression Distillation/Urine Processing Assembly (VCD/UPA) life

test was to provide for long duration operation of the VCD/UPA at normal ISS operating conditions to

determine the useful life of the hardware, specifically the flight-like components.2

 The VCD design has

evolved considerably over the past 20 years. Since it was initially developed, improvements include

changes in the peristaltic fluids pump, improved sensors, modifying the shape of the distillation

centrifuge to a tapered drum, and improvements to the compressor. The materials have been upgraded to

withstand the harsh environment inside the assembly, but long-term testing of a complete VCD/UPA

(with flight-like components) to determine the life characteristics of mechanical components under

simulated on-orbit conditions had not been done. The VCD/UPA contains mechanical design features

which inherently have limited life, such as the peristaltic pumps. The life test was planned so that the

VCD/UPA would be tested in the way that it will operate on orbit (with operation for a portion of each

day) rather than running continuously, as the manufacturer (Life Systems, Inc. (LSI)) had done during

previous testing. The on/off operation presents a more severe condition for the mechanical components

and, therefore, would reveal design problems not apparent during previous testing.
2

2. VCD/UPA PROCESS AND HARDWARE DESCRIPTION

The VCD/UPA is a phase-change water recovery technology which will reclaim water from urine

and other ISS wastewaters. Two VCD/UPA’s were tested, designated the VCD–5 and VCD–5A. The

process and hardware are described below.

2.1 VCD Process

In the VCD process, wastewater is distilled by evaporating clean water from a thin film of

wastewater at low pressures (3.4 to 5.5 kPa, 0.5 to 0.8 psia) and ambient temperatures (32 to 43 °C,

90 to 110 °F). The VCD process recovers the latent heat of condensation by compressing the water

vapor to raise its saturation temperature and pressure, and then condensing the vapor on a surface that is

in thermal contact with the evaporator. The resulting heat flux from the condenser to the evaporator,

driven by the saturation temperature difference, is enough to evaporate an equal mass of water from the

wastewater, so that the only additional energy required is that necessary to compress the water vapor and

overcome any mechanical and thermal inefficiencies.

As shown in figure 1, wastewater is circulated through the distillation unit (DU) by a foursection peristaltic fluids pump. One section of the pump discharges wastewater to the inner surface of

the evaporator centrifuge (still) in the DU at a rate greater than the vaporization rate. As water evaporates the vapor is compressed and transferred to the condenser. As the vapor condenses it is pumped out

of the DU by another section of the fluids pump and passed through a conductivity sensor. Unacceptable

water, that does not meet the conductivity specifications (<150 μmho/cm), is routed to the recycle loop

for reprocessing. Good quality condensate is delivered as product water. Excess wastewater is removed

from the still by two sections of the fluids pump and pumped through a recycle filter tank prior to mixing with fresh wastewater and reprocessing in the still. Periodically, a purge valve is opened to remove

noncondensable gases from the condenser by the purge pump and to maintain the operating pressure

between 3.4 to 5.5 kPa (0.5 and 0.8 psia).
3

Figure 1. Schematic of VCD process.

2.2 Hardware Description and Similarity With the ISS UPA

The design of the VCD–5 and VCD–5A hardware is described below and the degree of similarity

to the flight VCD/UPA is identified for each component.

2.2.1 VCD Hardware

Photographs of the VCD–5 and VCD–5A are shown in figures 2 and 3. As shown schematically

in figure 4, the VCD–5 and VCD–5A each consist of a wastewater storage assembly (WSA), a fluids

control assembly (FCA), a fluids pump assembly (FPA), a distillation assembly (DA), a recycle filter

tank assembly (RFTA), a pressure control assembly (PCA), a purge pump assembly (PPA), and sensors

for measuring conductivity, temperature, pressure, rotation speed, and electrical current level. These

components are described below.

RECYCLE FILTER TANK

MOTOR DISTILLATION UNIT

PURGE PUMP

WATER SEPARATOR

HEAT

EXCHANGER

FLUID

PUMP

CONDUCTIVITY

SENSOR

From

Urinal

Wastewater

Storage Tank

reprocess

coolant

c

purge gas

to cabin

atmosphere

to Water Processor

(via wastewater

distribution line)
4

Figure 2. Photograph of the VCD–5.

Figure 3. Photograph of the VCD–5A.

Facility Feed Tank

Feed

Transfer

 Pump

Chiller

Load Cell

Load Cell

DC Power

Data

Transfer

Computer

PDU

Computer

Power

Distribution

and Control Distillate

Storage

Purge

Pump

Fluids

Pump

VCD-VA

Subsystem
5

Figure 4. Schematic of VCD hardware and instrumentation.

2.2.1.1 Wastewater Storage Assembly. The WSA includes a titanium bellows tank (TK1) inside a shell

in which the quantity of liquid is measured by the position of the bellows. Wastewater stored in this tank

replenishes the wastewater loop as wastewater is injected into the still by the fluids pump. The WSA for

the ISS UPA is a single, integrated mechanical component which incorporates all of the discrete

components that make up the WSA in the VCD–5 or VCD–5A. The WSA for the ISS UPA has a sealed

shell which will act as a containment device if the bellows were to leak. The sealed shell can “breathe”

through a doubly redundant Gore-Tex membrane.

2.2.1.2 Fluids Control Assembly. The FCA consists of piping and valves that direct the flow of water

into and out of the DU, and provides an interface between the fluids pump and the recycle filter tank.

The FCA also includes a conductivity sensor, which monitors the conductivity of the distillate, and a

valve to direct the distillate to the product water outlet or to the recycle line for reprocessing. The FCA

for the ISS UPA is an integrated mechanical component which incorporates in one housing all of the

discrete components that make up the FCA in the VCD–5 or VCD–5A.

2.2.1.3 Fluids Pump Assembly. The FPA includes a four-section peristaltic fluids pump (PU1), as

shown schematically in figures 1 and 4, which continually circulates wastewater through the evaporator

side of the DU (one section supplies wastewater and two sections remove excess wastewater) and the

recycle filter tank, and removes the product water from the condenser side of the DU (one section).

T2

M1 S1 HX1

Distillation Unit

Coolant In

Legend

Pressure 

Transducer

P

P

P

P

P

P

P

∆P

P

P

P

P

S

T

T

T

Water

Separator

3 Way Valve

Temperature

Sensor

Speed Sensor

Solenoid Valve

Pressure

Regulator

Pump

Manual Valve

L Liquid Level 

Sensor

Flex Line

Cooling Coil

Conductivity

C Sensor

C

Check Valve

Relief Valve

S5

M2 S2 

Fluids Control and 

Pump Assembly

W1 M4

TK1

MV 4

Wastewater

Storage

Assembly

O1

MV3

CV1

Pretreated Urine From Urine

Collection System

P33

W1

M4

P31

CV2 

CV3

P32

LF1

MLF

RV2 

P41

Recycle Filter Tank Assembly

MV1 TK2 MV2 

Recycle 

Filter Tank

M4

W1 V2 CV4

Product

Water

P43

P42

K1

WS1

Condenser

Purge

P5

P2

Pressure Control and 

Pump Assembly

W2

V3

M3

S3

S6

PU2

PU1

LB1

LB

P12

CV5

Coolant

Out

Distillation Assembly

S4 S L L1 T1

P11

PR1

P13

RV1
6

Having two sections pumping water out of the DU ensures that the outlet capacity is always greater than

the inlet rate, which avoids flooding the still. A motor drives the fluids pump at 8 rpm through a

Harmonic Drive. The tubes of the pump are made of Norprene.

The FPA of the ISS UPA and the VCD–5 and VCD–5A are identical in size and function.

Differences are that the ISS UPA FPA housing is made of titanium whereas the VCD–5 and VCD–5A

FPA housings are aluminum, and the ISS UPA FPA uses a 120 volts, direct current (Vdc) brushless

motor, whereas the VCD–5 and VCD–5A use 28-Vdc brushless motors. The major processing function

of the tubes and rollers is the same. Figure 5 shows schematically the design concept and operation of a

peristaltic pump. The pump drive is described in section 2.2.1.7.1.

Figure 5. Peristaltic pump design concept and operation.

1

2

3

4

2.2.1.4 Distillation Assembly. The DA, shown schematically in figure 6, includes the DU, which is a

rotating drum centrifuge. The DU rotates at 185 rpm to spread the incoming wastewater into a thin film

from which water can evaporate easily at ambient temperature and reduced pressure (see also section

2.1). The water vapor is transferred to the outside of the drum through a compressor, where it condenses

as clean water. The DA of the ISS UPA and the VCD–5 and VCD–5A are identical in size and function.

The only differences are that the ISS UPA DU is made of titanium, whereas the VCD–5 and VCD–5A

DUs are stainless steel, the ISS UPA DA uses a 120 Vdc brushless motor, whereas the VCD–5 and

VCD–5A use 28 Vdc brushless motors, and the ISS UPA demister is a nonmetallic membrane-type,

whereas the VCD–5 and VCD–5A have steel wool-type demisters. The demister ensures that only

vaporized water is drawn into the compressor by blocking any droplets of wastewater.
7

Figure 6. VCD distillation assembly schematic.

Rotating Demister Rotating Centrifuge Housing

Magnetic Drive

Distillation Unit

Motor

Compressor

High Level Sensor

Evaporator Temp.

Sensor

Product Out

Evaporator

Pressure Tap

High Level Sensor and

Evaporator Temp. Sensor

Recycle Out

Purge Out

Feed In

2.2.1.5 Recycle Filter Tank Assembly. The RFTA includes a 22 L (0.78 ft3) tank with filters to remove

solids from the wastewater before it is recirculated through the distillation unit. The tank and filter

components are shown disassembled in figure 7. When the brine solids concentration reaches about 25

percent in the recycle filter tank, the tank is removed for cleaning and the filters are replaced. These

filters are shown in figure 8. The filters used for most of the life testing were dual 25 μm pore size spiral

wound filters, with a noncantilevered support (i.e., supported at each end). For testing of the VCD–5

during part of the Water Recovery Test (WRT) Stage 10,3 a single flight-like 10 μm pore size pleated

filter was used, with a cantilevered support, as shown in figure 7. Also, a 30 μm pore size pleated filter

was used during part of the WRT Stage 10 to compare the results. The brine was discarded during

cleaning of the tank. During flight operation the entire tank will be replaced as an orbital replaceable

unit (ORU) and the used tank will be returned to Earth for cleaning and filter replacement.
8

Figure 7. VCD/UPA RFTA disassembled (showing single filter configuration).

Figure 8. VCD/UPA filters (top: 25 μm pore size, bottom: 10 μm pore size).

The RFTA for the ISS UPA is an integrated mechanical component which incorporates all of the

discrete components that make up the RFTA’s in the VCD–5 or VCD–5A. Major differences are that the

ISS UPA RFTA uses a single cantilevered 10 μm filter element while the VCD–5 and VCD–5A use a

dual noncantilevered 25 μm filter design (except as noted above), and that the ISS UPA tank is made of

titanium, while the VCD–5 and VCD–5A tanks are stainless steel.
9

2.2.1.6 Pressure Control Assembly. The PCA consists of piping and valves to control the pressure in

the still. Also included is a gas/liquid separator (WS1) to remove any water from the purge gases and

return it to the product waterline. The primary function of the PCA is to periodically purge the DU of

noncondensable gases that enter as dissolved or free gases with the wastewater feed. As noncondensable

gases increase in the DU condenser, the pressure will increase, which will make the compressor work

harder and reduce the overall performance. The PCA monitors this pressure increase and activates the

PPA when a purge is required. The PPA compresses the noncondensable gas with water vapor to pressures above ambient, condensing the water vapor. From there, the noncondensable gas and condensate

pass through a membrane gas/water separator where condensate is recovered and routed back into the

product water stream. The noncondensable gases are released to the atmosphere.

The PCA for the ISS UPA is an integrated mechanical component which incorporates in one

housing all of the discrete components that make up the PCA in the VCD–5 and VCD–5A.

2.2.1.7 Purge Pump Assembly. The PPA is essentially identical with the FPA, consisting of a foursection peristaltic-type purge pump (PU2) which removes gases from the condenser side of the DU and

evacuates the casings of the fluids pump and itself. The four sections operate in parallel through inlet

and outlet manifolds. The only differences with the fluids pump are a cooling jacket around the purge

pump and the speed at which the pump operates (25 rpm versus 8 rpm for the fluids pump). Figure 9

schematically shows the basic design concept and connections of the PPA. The pump drive is described

in section 2.2.1.7.1. A membrane-type water separator removes condensed water from the purge pump

outlet stream. The water is combined with the product water from the DU and the air is returned to the

cabin atmosphere.

Figure 9. Purge pump design concept and connections.

Coolant

Out Coolant

In

Cooling

Jacket

Inlet Manifold

Purge Line

Casing

Connection

Casing

Connection

Fluids

Pump

Purge

Distillation

Pump

Unit

Outlet Manifold

Gas/condensate
10

The PPA of the ISS UPA and the VCD–5 and VCD–5A are identical in size and function.

Differences are that the ISS UPA PPA casing and cooling jacket are made of titanium, whereas the VCD–

5 and VCD–5A PPA casings and cooling jackets are aluminum; and the ISS UPA PPA uses a 120 Vdc

brushless motor, whereas the VCD–5 and VCD–5A use 28 Vdc brushless motors. The function of the

tubes and rollers is the same, as shown in figure 5.

2.2.1.7.1 Harmonic Drive. The FPA and PPA drive gearing is made by Harmonic Drive Technologies.4

The Harmonic Drive, shown schematically in figure 10, consists of concentric components that transmit

torque in less space and with a smaller support structure than conventional gearing. The components

consist of a circular rigid internal spline gear, an elliptical ball bearing wave generator, and an elliptical

nonrigid external flexspline gear. Benefits include low or zero backlash, efficiencies typically ranging

from 80 to 90 percent, torque transfer equivalent to other types of drives that are twice as large,

positional accuracy and repeatability, long life, and high reliability. The material of the rigid spline and

the flex spline is stainless steel. As used in the VCD, the Harmonic Drive is not subjected to a harsh

environment, and the temperatures and pressures around the Harmonic Drive are typical ambient

conditions. The normal speed of operation is 8 rpm for the fluids pump and 25 rpm for the purge pump.

Figure 10. Harmonic Drive.

Bearing

Support

Circular

Spline

Motor Mounting Adaptor

Wave

Generator

Drive

Flex Spline

Shaft Bearing

Drive

Shaft
11

The use of Harmonic Drives in VCD’s is summarized in tables 1 and 2.

Table 1. History of the use of Harmonic Drives in VCD’s.

VCD Designation Harmonic Drive Use Comments

Fluids Pump Purge Pump

VCD–4 √ Technology Demonstrator VCD

VCD–4A √

VCD–4B √ √ First VCD to Have a Peristaltic Purge Pump With Harmonic Drive

VCD-6 √ √

P VCD √ √ Converted From the VCD–4B

VCD–5 √ √ Converted From the POST VCD

VCD–5A √ √ Converted From the VCD–4

Table 2. Harmonic Drive operating history (as of May 25, 1993).

VCD Designation Harmonic Drive (HDC–1C–100–2) in Fluids Pump Harmonic Drive (HDC–1C–60–2) in Purge Pump

Drive # Run Time, hr (1) No. of Start/Stop Drive # Run Time, hr (2) No. of Start/Stop

VCD–4A 1 8,084 77 - - -

2 3,308 4

3 14,678 63

VCD–5 (3) 1 5,962 92 1 993 29,810

VCD–5A (4) 1 1,724 <100 1 127 (6) 3,810

2 362 N/A

VCD-6 1 370 50 1 191 (5) 1,850

Notes: (1) Time to failure, unless still operating

(2) Calculated based on 2 min per 12 min duty cycle without the startup time

(3) Converted from the VCD–4B (5,400 hr as VCD–4B, 562 hr as VCD–5)

(4) Converted from the VCD–4 (1,324 hr as VCD–4, 762 hr as VCD–5A)

(5) Actual time

(6) Based on 762 hr (362 + 400 hr) of operation as the VCD–5A

2.2.1.8 Instrumentation and Monitoring. The instrumentation identified in figure 4 and required to

monitor the operation and performance of the VCD–5 and VCD–5A for life testing is listed in table 3.

Data from these instruments were monitored via computer using the Systems and Components

Automated Test System (SCATS),5

 and the Payloads and Components Real-time Automated Test System

(PACRATS)6

 during the WRT Stage 10. The ISS UPA will have similar instrumentation and the sensors

will have redundancy built-in for fault tolerance.

2.2.2 Flight-like Components

The VCD–5 and VCD–5A were flight-like as indicated in table 4. Considering the components

by ISS UPA ORU, the function, capacity, material, and final design aspects are compared with the ISS

UPA. The controller for the VCD–5 and VCD–5A is a 400 Series Life Systems controller. The controller

for the ISS UPA is the next generation controller, with a new design having additional capabilities,

particularly with regard to self-diagnostics, e.g., fault detection and isolation.
12

Table 3. VCD–5 and VCD–5A instrumentation list.

Designation on Measurement ID Description Figure 4

vcl1 Recycle Filter Tank Concentration (Calculated)

I1 vi1 Compressor Motor Current

K1 vk1 Product Water Conductivity (Triple-Redundant Sensors,

Averaged Value)

L1 vl1 Liquid Level Sensor in the Distillation Unit

Q1 vq1 Wastewater Supply Tank Quantity

P1 vp1 Condenser Pressure

P2 vp2 Compressor Differential Pressure

vp3 Wastewater Inlet Pressure to the Recycle Filter Tank

vp4 Outlet Pressure Of Product Water From the Fluids Pump

P5 vp5 Differential Pressure Across the Gas/Liquid Separator

vqlb Wastewater Supply Quantity Average (lb)

vq4 Total Wastewater Processed (Calculated)

vq5 Recycle Fill Quantity

S1 vs1 Compressor Speed

S2 vs2 Fluids Pump Motor Speed

S3 vs3 Purge Pump Motor Speed

S4 vs4 Distillation Centrifuge Speed

T1 vt1 Compressor Outlet Temperature

vt2 Coolant Temperature

vt4 Condenser Temperature

Related Facility Instrumentation

VT5 Cooled Water Supply Temperature

VT6 Cooled Water Return Temperature

FP01 High Bay Pressure

FT01 High Bay Temperature

2.3 Upgrades from Previous VCD’s

The VCD–5 and VCD–5A are the designations given to refurbished earlier-generation VCD’s, as

indicated in table 2. During development of the ISS ECLSS design, the following additional

requirements were levied on the UPA and incorporated in the VCD–5 and VCD–5A:

1. Addition of a wastewater storage assembly (Facility wastewater tank used for the VCD–5A)

2. Addition of a coolant jacket to the PPA

3. Change in software operational aspects, i.e., operating modes, mode transitions, and process

control loops.
13

Table 4. VCD–5 and VCD–5A flight-like characteristics .7

VCD–5 and VCD–5A Flight-Like Characteristics (a)

ORU/component Function Capacity Material Design

Pressure Control Assembly

 Membrane Separator √ √√

 Pressure Sensors √ √

 Valves √ √

 Check Valve √ √

 Microbial Filter √

 QDs (b)

 Housing (b)

Fluids Control Assembly

 Conductivity Sensor √ √

 Pressure Sensor √ √

 Relief Valves √ √

 Check Valves √ √

 Valves √ √

 Microbial Check Valve (not on the 5A) √ √√

 QDs (b)

 Housing (b)

Controller

 Controller √ √

Wastewater Storage Assembly

 Bellows √ √

 Position Indicator √ √√

 Shell √

 Check Valve √

 Isolation Valve (b)

 QDs (b)

Recycle Filter Tank

 Valves √ √

 Filter √

 Shell √

 QDs (b)

Distillation Assembly

 Distillation Unit √ √

 Motor √

 Gear √ √√√

 Magnetic Drive √ √√√

 Bearings √ √√√

 Pulleys √√ √

 Insulation √

 Heat Exchanger √ √

 Plumbing √

 Speed Sensor √

 Liquid Level Sensor √ √√
14

Table 4. VCD–5 and VCD–5A flight-like characteristics .7 (Continued)

2.3.1 VCD–5 History

The VCD–5 is the designation given to the refurbished VCD used in the Boeing Predevelopment

Operation Systems Test (POST) at MSFC. The POST VCD had previously been the VCD–4B, the first

VCD to include a purge pump in the design and to use a Harmonic Drive on the purge pump. The VCD–

5 life test began on May 6, 1993. The VCD–5 was used in Stages 9 (July 19, 1994 to December 21,

1994) and 10 (October 1, 1996 to March 27, 1997) of the WRT. 3, 8

Distillation Assembly (Continued)

 Compressor √ √√√

 Temperature Sensor √

 Demister √ √

 Shaft Assembly √ √

 End Hub √ √

 Stationary Bowl √ √

 Front Plate √ √

 QDs (b) √ √

Fluids Pump Assembly

 Pump √ √√√

 Motor √ √

 Harmonic Drive √ √√√

 Shell √ √

 Tubing √ √√√

 Speed Sensor (S2) √ √

 Speed Sensor (b)

 QDs (b)

Purge Pump Assembly

 Pump √ √√√

 Motor √ √

 Harmonic Drive √ √√√

 Shell √ √

 Tubing √ √√√

 Cooling Jacket √ √

 Speed Sensor (S2) √ √

 Speed Sensor (b)

 QDs (b)

 Membrane Gas/Liquid Separator √ √√

Notes: (a) A √ indicates that the VCD–5 and VCD–5A component is like the ISS UPA design and is therefore

“flight-like.” If no √ is present then the component is not “flight-like.”

(b) This component is not used by the VCD–5 or the VCD–5A.

VCD–5 and VCD–5A Flight-Like Characteristics (a)

ORU/component Function Capacity Material Design
15

2.3.2 VCD–5A History

The VCD–5A is the designation given to the refurbished VCD used in the Comparative Test

(designated the VCD–4) in 1990 to compare the VCD with the Thermoelectric Integrated Membrane

Evaporation System (TIMES), previously baselined for use on ISS.

9

 The VCD–4 was not the final flight

configuration, but allowed performance characterization of the VCD components. The VCD–4 was

upgraded to be functionally identical with the flight design at which time it was redesignated VCD–5A.

The hardware modifications included design improvements to meet the additional requirements. The

VCD–5A was checked out in early 1993 in Building 4755 at MSFC and life testing began on January

12, 1993. A purge gas test was conducted in 1996 using the VCD–5A.

As a result of information gained during fabrication and testing of the VCD–4, the following

design improvements were made for the VCD–5A:

1. Retrofit of the fluids pump to provide dual support (two bearings) for the shaft, rather than

the previous cantilevered design

2. Replacement of the commercial vacuum pump with a dual support peristaltic purge pump

3. Change from truly tubular weld fittings to Parker weld fittings

4. Change from the commercial conductivity sensor to an LSI conductivity sensor

5. Replacement of the helicoil tube-in-shell recuperative heat exchanger with a tube-type heat

exchanger

6. Addition of a static membrane gas/water separator assembly

7. Addition of fluids pump tubing overpressurization protection.
16

3. TEST FACILITY DESCRIPTION

The VCD/UPA life testing was performed at MSFC in Building 4755, in the ECLS test facility

shown in figures 11 and 12. The test facility provided all necessary utilities and data collection and

monitoring capabilities. The VCD–5 was located next to the End-use Equipment Facility (EEF) and the

VCD–5A was located in the northwest corner of the north high bay. Urine was collected in the EEF (as

shown in figure 13) and a restroom, and pretreated using Oxone (Oxone is a registered trademark of

the DuPont Company) and sulfuric acid (in liquid form and, later, in solid tablet form as planned for use

on ISS) prior to processing in the VCD–5A. The EEF was designed, built, and integrated with the

ECLSS WRT to provide wastewater typical of that expected to be produced onboard ISS.

8, 10

Figure 11. ECLS test facility at MSFC.
17

Figure 12. Schematic of the ECLS test facility at MSFC.

Figure 13. EEF urinal.

VCD-5A

VCD-5

Life Test Area

Core Module

Simulator

Control Room

End-Use

Equipment

Facility

Sample

Preparation

Wet

Chemistry

North High Bay of Building 4755
18

4. TEST DESCRIPTION AND PERFORMANCE

The specific purpose for testing the VCD/UPA, the operating procedures, and summaries of the

testing performance are described below.

4.1 Test Purpose

The purpose of the VCD/UPA life testing was to determine the useful lifetimes of specific components that were considered to be subject to mechanical wear, and to monitor the processing performance

over an extended period of flight-like operation. Performance was assessed using simulated flight operation conditions, with the exception of microgravity.

4.2 Operating Procedures

The procedures for operating the VCD–5 and VCD–5A were different to evaluate somewhat

different aspects of operation. The VCD–5 was activated for two or three cycles each day with reduced

run times to gather data on startup and shutdown effects on the hardware and to accelerate mechanical

wear. Wastewater processing (production rate and quality of product water) was not monitored. When the

VCD–5 was incorporated in the WRT Stage 10, the operation was changed to more closely simulate flight

operation times and the production rates and quality of product water were monitored. The VCD–5A was

operated once each work day with processing run times as expected on-orbit (approximately six hours

each day) and the production rate was monitored to evaluate long-term performance characteristics.

4.3 Components Tested

The specific components of the VCD/UPA that were the subject of the life testing are the wastewater storage tank, peristaltic fluids pump, distillation unit, recycle filter tank, gas/liquid separator, and

peristaltic purge pump. These components are described in section 2.

4.4 VCD–5 Testing

The VCD–5 life test began on May 6, 1993 and ran until February 16, 1994, for a total of 204 test

days. A Gantt chart of the VCD–5 operation during this period is shown in figure 14. Significant test

events and anomalies are described in section 4.4.1. Additional testing was performed during the stage 9

and WRT Stage 10.3, 8 The WRT Stage 10 performance of the VCD–5 is described in more detail in section 4.4.2. Plots of typical operating conditions for the compressor temperature (T1), compressor motor

current (I1), and condenser pressure (P1) are shown in figures 15, 16, and 17, respectively. This testing

revealed several problems that can be directly attributed to quality control problems. Most anomalies were

related to low centrifuge speed, high compressor temperatures, and high condenser pressures. Conditions

that recurred, but were not listed as “anomalies,” are short-term high product water conductivity and

blockage of the gas/liquid separator and pressure regulator with Norprene particles.
19

Figure 14. Gantt chart of VCD–5 operation.

Activity Name

Normal Test

Operations

Shutdown

Anomaly: VCD–5–1

Shutdown Alarms

204

82

266

Go Status

Anomaly

Resolution

Down Time

Anomaly Review

Total

Days

MAY 93 JUNE 93 JULY 93

25 2 9 16 23 30 6 13 20 27 4 11 18 25

AUG 93

1 8 15 22 29

SEPT 93 OCT 93 NOV 93 DEC 93 JAN 94 FEB 94

5 12 19 26 10 17 24 31 3 14 21 28 7 12 19 26 5 9 16 23 30 6 13 20 27 2





Figure 15. VCD–5 typical compressor temperature (T1).

Compressor Outlet Temperature (°F)

0

50

100

150

200

250

69.3 69.4 69.5 69.6 69.7 69.8 69.9 70.0

Test Day

C

vt1 
20

Figure 16. VCD–5 typical compressor motor current (I1).

Figure 17. VCD–5 typical condenser pressure (P1).

Compressor Motor Current (A)

0

2

4

6

8

10

12

14

69.3 69.4 69.5 69.6 69.7 69.8 69.9 70.0

Test Day

vi1 

Condenser Pressure (mmHg)

0

10

20

30

40

50

69.3 69.4 69.5 69.6 69.7 69.8 69.9 70.0

Test Day

vp1 
21

The results of laboratory analyses of product water and brine samples are listed in table 5. The

product water quality was within specification for all parameters for all of these samples (150 μmho/cm

conductivity, pH of 3 to 8, and total organic carbon (TOC) <50). The brine analysis shows an increasing

solids content, as expected. The exact percentage of solids is difficult to determine. The three methods

used to calculate the percent solids show significant variation in calculated percent, but the trend is the

same for each of the methods.

Table 5. VCD–5 product water and brine compositions.

4.4.1 VCD–5 Test Events and Anomalies

The significant events and anomalies that occurred during testing of the VCD–5 are summarized in table 6.

The first anomaly related to difficulty at startup with reaching the normal drive speed for the

centrifuge, high compressor temperatures, and low gas/liquid separator pressures. The low centrifuge

speed was a particularly vexing problem and there were numerous efforts to correct this, including

adjusting the software. When the other problems led to disassembling the VCD–5 it was found that the

drive belt for the centrifuge had been incorrectly installed by the hardware supplier, resulting in the

low speed.

Units

Date

Test Day 122 126 131 138 143 149 152 161 168

Characteristic 11/8/93 11/22/93 12/20/93

Product Water Composition

pH 3.8 3.8 3.8 3.8 3.8 3.8 4

Conductivity μmho/cm 63 63.2 70.3 61.5 64 68.7 48.8

Turbidity NTU 0.3 <0.1 1.3 <0.1 <0.1 0.1 0.1

TOC mg/L 15.6 17.1 22.6 20.8 13

TIC mg/L 1 <1.0 2.01 <1.0 2.04

TC mg/L 17 17 25 21 15

Particles:

0-5 μm Particles Particles/mL 89.6 176 110 152 239 157 321 41.6

5.1-10 μm Particles Particles/mL 5.52 51.5 12.8 13.4 25.7 10.2 27.1 5.5

10.1-40 μm Particles Particles/mL <1.0 19.9 <1.0 <1.0 <1.0 <1.0 <1.0 <1.0

40.1-100 μm Particles Particles/mL <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 <1.0

100.1-500 μm Particles Particles/mL <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 <1.0

Brine Composition

Refractive Index 1.347 1.350 1.355 1.359 1.345 1.35 1.353 1.346

Specific Gravity 1.049 1.063 1.079 1.097 1.039 1.061 1.067 1.042

Solids Conc. (BS)* % 9.92 12.06 15.63 18.49 8.49 12.06 14.20 9.21

Solids Conc. (UJ)* % 7.45 9.08 11.8 13.97 6.36 9.08 10.71 6.91

Solids Conc. (UP)* % 9.22 11.11 14.26 16.77 7.96 11.11 13.00 8.59

Double vertical lines indicate cleaning of the recycle filter tank and replacement of the filters.

*Note: The Solids Concentration is calculated based on the refractive index and specific gravity of the brine. Three different methods were

compared to calculate the % solids: BS = Boeing Services, UJ = Umpqua Jolly, and UP = Umpqua Putman.
22

A recurring event was high conductivity of the product water. The procedure was changed to

include disconnecting the conductivity sensor at the beginning of a processing cycle until the timer reset

for up to 15 min of additional reprocessing. One effect of this is to reduce the performance by reprocessing water that meets specification.

Leakage occurred which limited the ability of the purge pump to maintain a vacuum in the still.

As a result, the pumping rate could not keep pace with the collection of noncondensable gases in the

condenser. Increasing the duration of the purge helped, but eventually a facility vacuum pump was

needed to ensure adequate vacuum. One source of leakage was the drive shaft of the pump.

The Data Acquisition System (DAS) was found to have a short, which was repaired the same day

it was found. This did not involve flight-like components.

The pressure regulator and the gas/liquid separator were found to be blocked with particles of

Norprene spalling from the purge pump tubes. These components were cleaned and reinstalled. (Further investigation of the purge pump tubing problem showed that spalling had occurred in the VCD–5A

as well. See section 4.5.1 for more information.)

High compressor temperature alarms occurred repeatedly during the life test. This was also

related to leakage. Use of facility vacuum to assist the purge pump helped to reduce these alarms, but the

combination of problems led to stopping the test on November 9, 1993 until repairs could be made on

January 13, 1994. Beginning on test day 20, a fan was used to cool the compressor motor from 66 to

42 °C (151 to 108 °F) which eliminated high temperature shutdowns. Also, software changes were made

to enable longer purge times since air in the wastewater feed was a factor. Compressor gear wear was

also a factor and during the repairs the compressor gear backlash was found to be 0.254 to 0.305 mm

(0.010 to 0.012 in.) versus 0.076 to 0.102 mm (0.003 to 0.004 in.) when new. This is considered normal

wear for a total running time of 7,400 hr, but near the maximum desired backlash. Particles of Vespel

from the compressor gear were also present in the product water due to gear wear.

To prepare the VCD–5 for the WRT Stage 9, the accelerated life test was discontinued on February 17, 1994, shortly after the repairs were made (on January 13, 1994) that resolved some of the

anomalies. Although the accelerated testing proved valuable, the decision to discontinue it was based

upon the continuing problems with the VCD–5. Repairs were made to correct the remaining problems

before continuing the testing (the WRT Stages 9 and 10).

The second anomaly occurred during the WRT Stage 9, when the CPU failed. (This was not a

flight-like CPU.) The multiplexer card was replaced and testing continued.

The third anomaly— recurring high compressor outlet temperatures at the beginning of each

processing cycle—also occurred during the WRT Stage 9, as well as during previous testing . The cause

for this is gravity-related, since any free gas entrained in the wastewater collects at the top of the tank,

where the outlet is located. This would not happen on-orbit due to more even distribution of free gas

throughout the wastewater. Thus, at the beginning of a cycle this gas is injected into the still before the

wastewater. Since the gas does not provide evaporative cooling, like the wastewater does, the compressor temperature increases until wastewater reaches the still.
23

The fourth anomaly occurred during the WRT Stage 10, when the motor speed controller malfunctioned. The motor speed controller was replaced by LSI. The cause of the malfunction was not

identified. The controller was sent to the manufacturer for repair, but was apparently lost.

The fifth anomaly was the presence of Vespel particles in the product water. This indicated

deterioration of the Vespel gear and the gear was replaced (see sec. 4.4.2). The quantity of Vespel

particles found in the product water then decreased as residual particles were swept from the water lines.

The sixth anomaly was the recurring high conductivity of the product water at the beginning of a

processing cycle. The cause of the high conductivity readings was not specifically identified until much

later (see section 4.4.1.1), although, when the sensor was cleaned, particles of Vespel were found in the

sensor and housing. Other possible factors are gas bubbles in the product water stream or leakage of

unprocessed wastewater into the fluids pump housing. The conductivity quickly decreased as processing

proceeded (see sec. 4.4.2.1.6).

The seventh anomaly was the recurring high temperatures at the compressor outlet (see also

anomaly three).

At the beginning of a processing cycle, high temperatures occurred for about 40 minutes, before

coming down to the desired range. The temperature was measured at the outlet of the compressor (vt1)

and indicated the temperature close to the gears. The temperature spiked above the alarm set-point of

93 °C (200 °F) due to the excessive load on the compressor and/or inadequate cooling of the gears. The

high temperatures were eliminated after a sample port was added at the outlet of the wastewater supply

tank, which enabled free gas to be removed during sample collection before the wastewater entered the

still. This is discussed further in section 4.4.2.

The eighth anomaly was failure of the purge pump, near the end of the WRT Stage 10. Facility

vacuum was used for the completion of the test. The pump was then disassembled, but no obvious

failure was apparent. Upon reassembly the pump worked properly.

4.4.1.1 VCD-5 Troubleshooting. In 1998, when the VCD-5 was being prepared for WRT Stage 11

integrated testing, the fluids pump was disassembled to investigate the problems with high conductivity

at start-up and occasionally at other times, and the difficulty maintaining sufficiently low purge

pressures. The housing of the pump (made of anodized aluminum) was found to be corroded inside.

None of the tubes had failed, but one of the clamps holding a recycle-loop tube (on the pressure side of

the pump) was very loose, which could allow small amounts of brine to be pumped into the housing and

then vacuumed out by the purge pump when the housings were evacuated. This would explain the high

conductivity of the product water and the pump housing leakage seen during Stage 10. In addition, one

of the O-rings fell apart when it was removed, and looked kinked like it had not been installed properly

or was the wrong size. This pump was last serviced by LSI possibly before Stage 9.
24Table 6. VCD–5 significant events and anomalies.

Anomaly

Number

VCD–5-1WRT Stage 9 VCD–5-2VCD–5-3WRT Stage 10VCD–5-4VCD–5-5VCD–5-6VCD–5-7VCD–5-8

Date

Occurred

5/7/935/19/931/11/94recurring problem5/26/93recurring problem6/4/938/2/93N/A11/4/93recurring problem11/9/9311/16/931/13/949/11/949/11/941/1/9610/30/9610/31/96 recurring11/4/963/21/97

 DateClosed Out 1/13/94 5/25/94 7/19/94 6/4/93 8/2/93 1/13/94 2/16/9411/9/94 12/22/94 6/27/96 11/6/96 10/31/9612/9/96 3/24/97

Notes/Action to Resolve 

LSI field service on 1/12/94 corrected misaligned during assembly. LSI field adjustments, recalibrated sensors, fixeLSI field service on 7/19/94 replaced fthe fluids pump.The procedure was changed so that thdisconnected at the beginning of a proresets for up to 15 minutes of additionPurge duration increased.Repaired.Norprene® particles found in the press

separator. These components were cleFacility vacuum used to assist the purgDrive belt reinstalled correctly, gas/liquregulator cleaned of Norprene® partic

Multiplexer card replaced.High pressures caused by urinal interfMotor speed controller replaced by LSVespel® gear replaced.

Cleaned K1 sensor and sensor housingthe discovery of a corroded fluids pumThe cause was air being injected into tcycle. A sample port was added at the tank. During sample collection, free gaenters the still.Facility vacuum was used until concluspump was then disassembled, but no Upon reassembly, the pump worked p

Event/Anomaly Description

Life test beganRecurring shutdowns due to low centrifuge speed (S4), low gas/liquid differential pressures, and high compressor temperatures (T1).High product water conductivity alarms, recurring problem.Leak found in pump housingsShort in the Data Acquisition System Blockage of pressure regulator and gas/water separator.High compressor temperature alarms.Test stopped due to low S4, low P5, and high T1Test restartedRepairs madeCPU failureHigh compressor outlet temperature (T1)Motor speed controller malfunction.Vespel® particles found in product water.

Continued high conductivity (K1) alarms.Compressor outlet temperature (T1) high, due to gas entering the still at the beginning of a cycle.Purge pump failure

Actionee

Hutchens, Long, SalyerHutchens, Long, SalyerHutchens, Long, SalyerHutchens, Long, SalyerHutchens, Long, SalyerHutchens, Long, SalyerHutchens, LongHutchens, LongHutchens, Long, SalyerWieland, LongHutchens, LongWieland, LongWieland, Long

Bold indicates that a flight-like component is affected
25

The housing was cleaned and found to be severely damaged. The sealing surfaces were corroded

to the point of significant leakage of air into the pump. For the flight VCD the pump housings will be

made of titanium.

4.4.2 VCD–5 Performance During the WRT Stage 10

Prior to beginning the WRT Stage 10, several modifications were made to the VCD–5. These

modifications consisted of installing a flight-like recycle/filter tank so that flight-like filters could be

used, use of a different motor speed controller, and revising the purge control algorithm. The urine

pretreatment process was also changed to a solid tablet form as will be used on board ISS (rather than

liquid as for previous testing).

The operation and performance of the VCD–5 during Stage 10 are described below. A total of

1175.2 kg (2,585.3 lb) of pretreated urine/flush water and 87.2 kg (191.9 lb) of the Crew Health Care

System (CHeCS) wastewater were processed by the VCD–5 during 565 hr of operation, with 1092.0 kg

(2,402.5 lb) of distillate delivered to the water processor (WP) waste feed stream. The average production rate, therefore, was 1.93 kg/hr (4.25 lb/hr), somewhat less than the WRT Stage 9 rate of 2.04 kg/hr

(4.50 lb/hr). The product water consistently met the water quality requirements and the VCD–5 recovered 88 percent of the pretreated urine and CHeCS wastewater.

4.4.2.1 VCD–5 Operation During WRT Stage 10. Key events during the stage 10 test are listed in

table 7. Repeated events are product water conductivity high warning/alarm, sensor indications of

slippage of the still drive belt, and occasional compressor outlet temperature high alarms. The high

conductivity of the product water is discussed in section 4.4.2.1.6. The indication of still drive belt

slippage was due to either a loose belt, Vespel particles, or condensation on the belt. The still would

come up to speed before the time limit was reached, so this did not stop the VCD–5, but could have

contributed to reduced performance. On test day 35, the compressor temperature high alarm occurred

when the compressor gears had worn enough to require replacement of the Vespel gear. The cause of

the compressor temperature high alarm on test day 141 has not been identified. Shutdowns occurred due

to high conductivity in the product water, gear wear (prior to replacement of the Vespel gear), and high

product water pressure (on test days 45 and 128, the cause has not been specifically identified). Other,

one-time, events are discussed in the following sections.

The inputs and outputs are summarized in table 8. During the first week of testing, and then daily

starting on test day 28, supplemental urine was added to have a total of 7.9 kg/day (17.5 lb/day) (processing occurred every other day as a result). In addition, on each Friday 4.5 kg (10 lb) of CHeCS

wastewater was added, about one-fourth of the volume of the Friday runs.
26

Date Test Day Event/Resolution

10/9/96 9 Appeared That the Drive Belt was Slipping (S4 was Low)

10/11/96 11 Product Water Pressure High Alarm, Due to Facility Valve Inadvertently Left Open When Working on a

Flow Meter, the Valve was Closed

10/12/96 12 Shutdown, Restarted After a Few Seconds

10/19/97 19 Supplemental Urine Added

10/24/96 24 K1 High Alarm >Shutdown Overnight, Restarted the Next Morning

10/28/97 28 Beginning of Regular Additions of Supplemental Urine to Have a Total of 17.5 lb/day

10/30/96 30 Vespel® Particles Found in Product Water

10/31/96 31 K1 High Alarm >Shutdown, Cleaned K1 of Vespel® Particles

11/4/96 35 K1 High Warning, Disconnected K1 to Allow Time for Water to Flush the Sensor,

Cleaned Vespel® Particles From V010 (pH)

T1 High Alarm >Shutdown, Due to Gear Wear and Free Gas in Wastewater Inlet

11/6/96 37 Vespel® Gear Replaced

11/7/96 38 K1 High Warning, Disconnected K1, Then Reconnected

11/14/96 45 P4 (Product Water) Pressure High >Shutdown

11/15/96 46 K1 High Alarm

11/23/96 54 K1 Alarm Not Responding, Shutdown to Clear Alarm

12/2/96 58 K1 High Warning, Disconnected K1 So That Distillate Would Be Produced,

Reconnected After Processing Began, No Warning Recurred

12/6/96 62 Q1 Low Alarm, Never Before Happened During Backfilling of Tank, Looks Like Valve V4 Did Not Close

12/9/96 65 A Sample Port Was Added Downstream of the Feed Tank (on Top of the Tank).

12/18/96 74 K1 High Alarm >Shutdown

12/20/96 Shutdown for Christmas/New Year’s Day Holiday Break

1/6/97 76 S4 Indicates That the Still Is Slipping

1/8/96 78 S4 Indicates That the Still Is Slipping

1/21/97 91 K1 High Alarm >Shutdown

1/29/97 99 K1 High Warning

2/4/97 105 S4 Indicates That the Still Is Slipping, K1 High Warning

2/11/97 112 K1 High Warning

2/18/97 118 S4 Indicates That the Still Is Slipping

2/25/97 124 K1 High Warning

2/27/97 126 K1 High Warning

3/3/97 128 P4 Alarm, Product Water Pressure too High >Shutdown, K1 High Warning

3/4/97 129 VI01/VF01 Stuck

3/20/97 141 T1 High Alarm >Shutdown

3/21/97 142 Purge Pump Not Working >Shutdown Due to High P and T in the Still, Facility Vacuum

Connected to the Vent Port

3/24/97 143 Connected Facility Vacuum to Downstream of Valve V3

3/26/97 145 Leak Through Purge Pump or V3 Suspected

Table 8. VCD–5 inputs and outputs during WRT Stage 10.

VCD–5 Inputs.

Units Urine Flush Supplemental Urine Supplemental Flush CHeCS Total

kg 731.70 181.92 196.60 64.94 87.23 1,262.39

lb 1,609.74 400.22 432.52 142.87 191.90 2,777.25

VCD–5 Outputs

Units Brine Samples Product Distillate Total

kg 133.52 26.90 1,092.03 1,252.45

lb 293.75 59.19 2,402.46 2,755.40

Table 7. VCD–5 key events during WRT Stage 10.
27

4.4.2.1.1 Software/Firmware Changes. The computer algorithm that controls the purge pump was

modified prior to beginning stage 10 to correct the following problems with the purge pump/valve

control:

1. During transition from normal to standby, the purge valve closed when it was supposed to

remain open.

2. Instead of having a 10 min purge cycle, the purge pump remained on continuously.

These problems were due to software errors and required new Erasable Programmable Read

Only Memory (EPROM’s). The desired sequence is that at startup the pump housings are purged for

10 min, then the still is purged. The controller checks the pressure in the evaporator and stops when the

pressure is reduced to the vapor pressure (determined by a curve based on the vapor pressure at the

current temperature), then purges for 2 min every 10 min.

As noncondensable gases build up in the still, one effect is that the current draw of the compressor increases. When the current reaches 11A, a purge is supposed to be initiated, however, the software

had not been changed to ensure that this would happen. New EPROM’s corrected this also, prior to

beginning Stage 10.

4.4.2.1.2 Motor Speed Controller. Prior to beginning the test, it was also found that the rotation speed

of the still was about 63 rpm rather than the desired 180 rpm. This was due to the controller telling the

motor that no more speed was needed, not because the belt was slipping, although slippage may have

occurred as well. The compressor was not coming up to speed either, but the speed signal was misinterpreted due to a software error. The motor and controller signals were, apparently, scaled improperly such

that the motor would never reach the desired speed. The motor speed controller was replaced prior to

Stage 10 and the new motor controller worked properly.

4.4.2.1.3 Vespel Gear Replacement. Vespel particles began appearing in the product water on test

day 29, indicating degradation of the Vespel gear. When the still was disassembled on test day 37 to

replace the gear, rust was found on the hub where L1 feeds through, apparently from the three locking

rings behind the hub. Yellow crystalline deposits were found on the separator plate between the evaporator spokes. Vespel dust was “everywhere”, including coating the drive belt. The old gear showed less

wear than expected (there were no chips or broken teeth) but the backlash was 0.279 to 0.533 mm (0.011

to 0.021 in.). With the new Vespel gear the backlash was 0.102 to 0.127 mm (0.004 to 0.005 in.). It is

estimated that the Vespel gear had about 8,000 hr of operation time, including 7,300 hr of continuous

operation at LSI and 700 hr of start and stop operation at MSFC (WRT Stages 9 and 10).

A filter was added to the product water line to monitor the presence of Vespel particles in the

water. Over time, after replacement of the gear, the amount of Vespel particles in the water diminished

as residual particles were removed and as “wearing in” of the new gear occurred.

4.4.2.1.4 Calculation of the Percentage of Solids in the RFTA. The criteria for determining when

to clean the recycle tank and replace the filter was initially based on when the VCD software controller

indicated it was time for replacing the filter, calculated by the amount of wastewater processed. As the

solids concentration increases the filter becomes coated, as shown in figure 18. The amount of
28

wastewater processed was determined by the delta of Q1 (which measures the bellows position in the

supply tank) before and after a processing period. This procedure, however, does not account for wastewater added during a processing period, and so, frequently, more wastewater was processed than was

indicated. One result was that the percentage of solids in the recycle tank exceeded the intended level of

25 percent solids when the tank is cleaned. The numbers shown in table 9 (see sec. 4.4.2.1.8) are the

CL1 sensor readings, which were below the actual values. This affects the performance, and may have

contributed to a lower production rate, although this same situation existed during stage 9 testing, as

well. (All other testing of the VCD at MSFC was in batch mode, which is not subject to this effect.) By

manually calculating the amount of wastewater processed, to account for wastewater added during a

processing cycle, the amount of solids on the filter was decreased. This procedure change was made

on test day 65.

Figure 18. VCD–5 10 μm pore size filter used during WRT Stage 10.

4.4.2.1.5 High Temperatures and Pressures in the Still. As shown in figures 19 and 20, at the beginning of a processing cycle, high temperatures and pressures occurred in the still during the first 40 min

before coming down to the desired ranges. The temperature was measured at the outlet of the compressor (vt1) and indicated the temperature close to the gears. The temperature spiked above the alarm setpoint of 93 °C (200 °F) due to the excessive load on the compressor and/or inadequate cooling of the

gears. The pressure was measured in the condenser (vp1) and reached about 60 mmHg. These same

conditions occurred during previous testing (see the Stage 9 report 8

) and were attributed to air in the

wastewater tank collecting at the top of the tank, where the outlet is located, and being injected into the

still (in microgravity the air would likely be more evenly distributed throughout the liquid). Therefore,

until liquid was injected into the still, no evaporative cooling would occur. The condition of the compressor gears was also found to be a factor. After test day 37, when the Vespel gear was replaced, the

temperature and pressure spikes were reduced considerably, to within the desired ranges (as shown in

figures 21 and 22). After test day 65, when a sample port (number 19) was added to the top of the feed

tank, the temperatures and pressures at startup were reduced further (as shown in figures 23 and 24). In

the process of collecting samples of the feed mixture, at the beginning of each processing cycle, the air

was purged from the supply line. The transition time required to reach normal operating conditions was

reduced from over 3 hr to under 2 hr, due to replacing the Vespel gear and purging air prior to a processing run.
29

Figure 19. VCD–5 compressor outlet temperature (WRT Stage 10 test days 11 and 12).

0

50

100

150

200

250

11.0 11.2 11.4 11.6 11.8 12.0 12.2 12.4 12.6

Test Day

d

vt1 

Figure 20. VCD–5 condenser pressure (WRT Stage 10 test days 11 and 12).

0

10

20

30

40

50

60

11.0 11.2 11.4 11.6 11.8 12.0 12.2 12.4 12.6

Test Day

H

vp1 

Compressor Outlet Temperature (°F)

Condenser Pressure (mmHg)
30

Figure 21. VCD–5 compressor outlet temperature (WRT Stage 10 test days 40 and 41).

Figure 22. VCD–5 condenser pressure (WRT Stage 10 test days 40 and 41).

0

50

100

150

200

250

40.40 40.60 40.80 41.00 41.20 41.40

Test Day

vt1 

0

10

20

30

40

50

60

40.40 40.60 40.80 41.00 41.20 41.40

Test Day

vp1 

Condenser Pressure (mmHg)

Compressor Outlet Temperature (°F)
31

Figure 23. VCD–5 compressor outlet temperature (WRT Stage 10 test days 68 and 69).

Figure 24. VCD–5 condenser pressure (WRT stage 10 test days 68 and 69).

0

50

100

150

200

250

68.6 68.8 69.0 69.2 69.4 69.6

Test Day

vt1

0

10

20

30

40

50

60

68.6 68.8 69 69.2 69.4 69.6

Test Day

vp1

Compressor Outlet Temperature (°F) Condenser Pressure (mmHg)
32

Figure 25 shows the condenser temperature (vt4) calculated from the operating pressure (by the

VCD software based on saturated steam correlations) during nominal processing of a batch of pretreated

urine. This is typical of the operating temperature curves for the VCD–5.

Figure 25. VCD–5 calculated condenser temperature (WRT Stage 10 test days 68 and 69). Calculated Condenser Temperature (°F)

65

70

75

80

85

90

95

100

105

68.6 68.7 68.8 68.9 69 69.1 69.2 69.3 69.4 69.5 69.6

Test Day

d

vt4

4.4.2.1.6 High Conductivity Alarms. During the transition from standby to normal, reprocessing of the

product water occurs while the pumps and motors are coming up to speed. Then after the fluids pump is

up to speed, the product water conductivity sensor (K1) checks the conductivity of the product water and

if it meets specification then the reprocessing valve (V2) switches to deliver product water, and within

1 to 2 min the transition to normal is completed.

If the water does not meet the specification when the transition to normal occurs then a high

conductivity warning is initiated and V2 switches back to reprocessing for up to 15 min. Within the

15 min period, if the conductivity of the water drops below 120 μmho/cm for 2 min then V2 cycles to

product. If the conductivity is still high at the end of the 15 min period then an alarm is initiated and

the VCD shuts down.

Repeatedly, throughout much of the test, at the beginning of a processing cycle K1 would indicate high conductivity (>250 μmho/cm) which could lead to shutdown. In order to prevent shutdown,

if the water was still above specification near the end of the 15 min period, K1 was disconnected (which

sends a reading of 0) which caused V2 to cycle to product. K1 was then reconnected within a few sec.

Upon reconnection, K1 indicated high conductivity and V2 cycled back to reprocessing for another
33

15 min period. This procedure was repeated until the conductivity stayed within specification, which

could require several repetitions. If K1 had not been disconnected, and the VCD shutdown and restarted,

after several restarts the conductivity would be within specification. Disconnecting K1 was a timesaving procedure which had the same result.

High conductivity was not detected later in a cycle and samples of the product water were well

within specification (with one exception on test day 35, as shown in figure 26 which also shows the pH

of the product water samples). One effect would be a reduction of the production rate, and this may have

contributed to having a lower average rate than for Stage 9. The primary cause of this condition was

later found to be due to leakage of brine into the fluid pump housing (see section 4.4.1.1).

Figure 26. VCD–5 product water conductivity and pH.

pH

0

50

100

150

200

250

0 50 100 150

Test Day

ho

0

1

2

3

4

5

6

7

8

Conductivity

pH

pH specification

3 to 8

conductivity specificatio

< 150

μmho/cm

pH

pH specification

3 to 8

conductivity specification

<150

4.4.2.1.7 Purge Pump Failure. Near the end of the test (test day 142) the purge pump failed, leading to

high temperatures and pressures in the still. To enable continued operation, a facility vacuum source was

connected to the vent port (as shown schematically in figure 35 for the VCD–5A). After completion of

the test, the purge pump was disassembled but no apparent mechanical failure was found. When the

pump was reassembled and checked, it worked as intended. It is thought that a seal began leaking and

that during reassembly it was seated properly.
34

4.4.2.1.8 Recycle/Filter Tank. After cleaning of the recycle tank and replacement of the filter, it takes

two cycles of the wastewater supply tank (fill and drain) to fill the recycle tank before processing is

initiated. The recycle/filter tank cleanings and filter replacements are listed in table 9. The filters used

during WRT Stage 10 were: single 10 μm pore size Osmonics Flotrex pleated filter (flight-like) used

initially, single 30 μm pleated filter (used two times), and double 25 μm spiral wound filter. Initially the

10 μm filters were used, until December 5, 1996 when a 30 μm filter was installed in order to determine

whether there was a significant difference in performance of the different filters. For the last processing

cycle, two 25 μm filters were used (the same type as used on all previous VCD testing at MSFC prior to

stage 10), also to compare the performance. No significant difference in water processing rate or quality

was apparent. The conditions of the filters showed variation, but this was true even when the same type

filters were used. The reasons for this variation may be related to different amounts of water processed

(related to the method for calculating percentage of solids in the recycle tank, see section 4.4.2.1.4) as

well as the different types of filters used. Further testing is needed to determine the reasons for this

variability and whether this could pose a problem.

Table 9. VCD–5 recycle/filter tank cleaning/filter replacement during WRT Stage 10.

Test

Day

0

35

50

61

84

108

131

Notes

Start of test on 10/1/96

Stopped due to gear wear, not solids buildup 

in the brine.

Removed for inspection and addition of a ∆P 

sensor and an inlet P transducer, not cleaned, 

no filter replacement

Replaced with 30 μm, tank filling failed, 

drained tank and reevacuated, V4 did not 

close which drained the feed tank too low, 

resulting in Q1 low alarm

replacement based on throughput, not Q3

replaced with two 25 μm filters to compare 

buildup of solids

replaced with original single element pleated 

10 μm filter 

Filter

10 μm 

Osmonics 

Flowtrex

10 μm

not replaced

10 μm

30 μm

30 μm

25 μm (two 

filters)

Condition

New

bottom 3/4 of filter coated with thick brownred brine, bottom of tank with thick 

white/yellow sludge

12.7% CL1, tank fluid was dark and the filter 

was dark (no solids on filter)

24.7% CL1, larger crystals were found in the 

brine than on 11/4

22.2% CL1, similar condition but not as bad. 

All slots on plastic sleeve filled with solids.

24.93% CL1, no crystals on filter mount, 

white crystals on filter

21.4% CL1, light tan tint, some small 

formations of light brown crystals, no thick 

brown solids, white solids on bottom of tank

Date

Removed

9/30/96

11/4/96

11/19/96

12/5/96

1/14/97

2/7/97

3/6/97

4.4.2.2 VCD–5 Performance. The VCD–5 production rate is shown in figure 27, which also shows

when the recycle tank cleanings and filter replacements occurred during the test and the type of filter

used. Tank cleaning and filter replacement occurred when the throughput of urine to the VCD–5 reached

approximately 182 kg (400 lb). The VCD–5 averaged 1.93 kg/hr (4.25 lb/hr) during the test, below the
35

specified processing rate of 2.04 kg/hr (4.5 lb/hr) for the ISS, which was achieved during Stage 9 testing.

The production rates were determined by dividing the amount of water processed in a batch by the

number of hours the VCD–5 was in operation. The duration of operation includes the transition periods

from standby to normal operation (which may take an hour or more) and from normal to standby (which

takes from 5 to 10 min), and periods of reprocessing. The production rate decreased over time as the

solids concentration increased in the recycle loop. The rate increased each time the recycle tank was

cleaned. The VCD–5 recovered about 88 percent of the pretreated urine and CHeCS wastewater. This

recovery rate is similar to previous testing conducted with the VCD–5. Differences in water recovery are

generally due to the timing of the cleaning of the recycle/filter tank.

Figure 27. VCD–5 product water production rate during WRT Stage 10.

4.4.2.3 VCD–5 Product Water Quality. The water quality specifications and average water quality data

for the VCD–5 distillate are shown in table 10. The TOC, total inorganic carbon (TIC), and total carbon

are graphed in figure 28. In general, the water quality was considered nominal for the VCD–5, and was

well within the specified level. The only exception was on test day 35 when the TOC reached 105 mg/L.

The reason for this may be related to the mechanical problems experienced on that day due to wear of

the Vespel gear. As shown in figure 26, the pH and conductivity are well within specification, with the

only exception on test day 35 when the conductivity reached 246 μmho/cm. On test day 133 the pH

showed a spike to 7.2. The reason for this has not been determined. No differences in water quality were

attributed to adding CHeCS water or to the urine pretreatment tablets, although the average conductivity

was about 12 μmho/cm higher than for Stage 9, and higher than the 40 to 60 μmho/cm (occasionally

above 70) during life testing in 1993 and 1994. Even so, the average conductivity was well below the

ISS specification of 150 μmho/cm maximum.

0

2

4

6

8

10

12

14

0 20 40 60 80 100 120 140 160

Test Day

lb/h

* recycle/filter tank cleaned

two 25 micron 

filters

30 micron

filter

10 micron

filter

purge pump

failure

sample port

19 added

Vespel gear

replaced

* * * * * *

10 micron

filter

lb/hr
36

Figure 28. VCD–5 product water carbon composition during WRT Stage 10.

Table 10. VCD–5 product water quality during WRT stage 10.

Parameter Specification Units Average for Stage 10 # of Samples

Conductivity <150 μmho/cm 72.10 41

pH 3 to 8 pH 3.90 41

Total Organic Carbon <50 mg/L 23.49 41

4.4.2.4 VCD–5 Conclusions and Recommendations from the WRT Stage 10. Overall, the quality of

the product water was well within the specified levels, increasing confidence in the ability of the VCD to

produce water meeting the required specifications. The production rate (1.93 kg/hr, 4.25 lb/hr) was

somewhat below the specified rate (2.04 kg/hr, 4.50 lb/hr), but the reasons for this may be related to the

shutdowns that occurred during processing cycles and additional reprocessing due to high conductivity

readings. The shutdowns were caused by other subsystems being tested (the WP), or by VCD–5

anomalies such as the Vespel gear failure and its related problems. The variation in condition of the

filters needs further investigation to determine the reasons for this variability and whether this could

pose a problem during flight operations.

0

20

40

60

80

100

120

0 20 40 60 80 100 120 140 160

Test Day

mg/L

Total C

TIC

TOC

TOC Specification < 50 mg/L
37

4.5 VCD–5A Testing

The VCD–5A life test began on January 12, 1993 and ran until November 9, 1995 (612 test days)

with additional testing (Purge Gas Test) after some repairs were made, until April 24, 1996, for a total of

665 test days. A Gantt chart of the VCD–5A operation is shown in figure 29. Plots of typical operating

conditions for the compressor temperature (T1), compressor motor current (I1), and condenser pressure

(P1) are shown in figures 30, 31, and 32, respectively. The total mass of wastewater/urine processed was

5,198 kg (11,449 lb) until November 9, 1995. The overall average production rate was, therefore,

1.76 kg/hr (3.87 lb/hr) for 2,960 hours in normal, through November 9, 1995. The quality of the product

water (measured by conductivity as shown in figure 33) was well below the specified limit (150 μmho/cm)

except for a few momentary spikes. The conductivity increased until the recycle filter tank was replaced,

when it would drop to about 25 μmho/cm. The composition of the product water and the brine are listed in

table 11.

Activity Name

Normal Test Operations

(Test Days Only)

Shutdown

Anomaly: VCD–5A–1

Flex Spline Failure

Anomaly: VCD–5A–2

Feedline Check Valve

Anomaly: VCD–5A–3

Flex Spline Failure

Anomaly: VCD–5A–4

Purge Pump Failure

Anomaly: VCD–5A–5

Compressor Differential

Pressure Sensor (VP2)

Anomaly: VCD–5A–6

Waste Recycle Pressure

Sensor (VP2)

Anomaly: VCD–5A–8

Condensor Pressure

Sensor (VP1)

Anomaly: VCD–5A–7

Peristatic pump tubing

particles

Anomaly: VCD–5A–9

Compressor Gears

665

(Test

Days)

117

(Shut

downs)

45

551

90

6

383

343

28

118

74

Go Status

Anomaly

Resolution

Down Time

Anomaly Review

Total

Days

1992 1993

OND J FM AMJ JAS ON D J FM

1994 1995 1996

AMJ J S OND A F MA J J JA M O ND J F MAM S J

Figure 29. Gantt chart of VCD–5A operation.
38

Figure 30. VCD–5A typical compressor temperatures (T1).

Figure 31. VCD–5A typical motor current (I1).

7 8 9 10 11 12

03/18/94

06:40

Calendar Time (hr)

Minor Tick = 5 min

03/18/94

12:24

DC Motor Current

 VI1

Averaged Data

10

9

8

7

6

5

4

3

2

1

0

Amps

7 8 9 10 11 12

03/18/94

06:40

Calendar Time (hr)

Minor Tick = 5 min

03/16/94

12:24

Compres Out Temp

 VT1

Averaged Data

160

150

140

130

120

110

100

90

80

Temperature ( ̊F)
39

Figure 32. VCD–5A typical condenser pressures (P1).

Figure 33. VCD–5A product water conductivity.

7 8 9 10 11 12

03/18/94

06:40

Calendar Time (hr)

Minor Tick = 5 min

03/18/94

12:24

Condenser Press

 VP1

Averaged Data

30

28

26

24

22

20

18

16

150

100

50

0

0 25 50 75 100 125 150 175

Test Week

Conductivity (

μmho/cm)

mmHg 
40

Table 11. VCD–5A product water and brine compositions.

Characteristic

Product Water CompositionpHconductivityturbidityTOCTICTCParticles:0-5 μm particles5.1-10 μm particles10.1-40 μm particles40.1-100 μm particlesBrine compositionRefractive IndexSpecific GravitySolids Conc. (BS)*Solids Conc. (UJ)*Solids Conc. (UP)*

Test Day

μmho/cm

NTU

mg/Lmg/Lmg/L

particles/mLparticles/mLparticles/mLparticles/mL

%%%

87

3.8

70

0.1

22.51.11

24

18.4

2.2

<1.0<1.0

1.3631.10421.3416.1519.29

9230 

Aug 

93

4 

43.4

0.1

13.3<1.0

13

64.5

10

<1.0<1.0

1.3431.033

7.075.276.70

97

3.8

61.6

0.2

18.71.67

20

74.28.86<1.0<1.0

1.3521.06613.4910.1712.37

104

3.8

72.4<0.124.34.71

2957

3.52<1.0<1.0

1.3631.10321.3416.1519.29

106

20 

Sep 

93

4 

44.4

0.2

14.5<1.0

15

79.57.95<1.0<1.0

1.3411.026

5.644.195.44

111

4 

56.9

0.4

19.12.68

23

44.34.78<1.0<1.0

1.3511.06212.78

9.62

11.74

116

3.8

68

<0.119.42.45

22

63.8

2.9

<1.0<1.0

1.3551.07515.6311.8014.26

121

17.7<1.0

18

47.52.92<1.0<1.01.36

1.09319.2014.5217.40

125

18 

Oct 

93

4 

41.9

0.1

19.72.36

2232

<2.0<1.0<1.0

1.3381.018

3.502.563.56

130

4 

50.2<0.113.62.23

16

70.9

5.5

<1.0<1.0

1.3451.042

8.496.367.96

135

3.8

62

0.9

16.1

<1. 0

16

42.94.92<1.0<1.0

1.3511.06312.78

9.62

11.74

140

18.71.57

20

54.73.55<1.0<1.0

1.3561.08416.3512.3414.88

144

15 

Nov 

93

4 

47.2<0.152.93.38<1.0<1.0

1.3421.026

6.354.736.07

Double vertical lines indicate cleaning of the recycle filter tank and replacement of the filters.* Note: The Solids Concentration is calculated based on the refractive index and specific gravity of the brine.

Three different methods were compared to calculate the % solids:BS = Boeing Services, UJ = Umpqua Jolly, and UP = Umpqua Putman.

 Date

Units
41

Wastewater Wastewater

Date Test Day Elapsed Days Processed (kg) Processed (lb)

2/4/93 16 16 161.90 356.60

2/26/93 32 16 165.08 363.62

3/18/93 45 13 147.40 324.66

7/15/93 59 14 147.36 324.58

8/4/93 73 14 174.35 384.03

8/25/93 89 16 167.23 368.35

9/17/93 104 15 160.17 352.79

10/18/93 124 20 168.38 370.88

11/10/93 142 18 163.59 360.32

12/7/93 157 15 167.88 369.78

1/6/94 177 20 164.48 362.30

2/4/94 197 2 180.99 398.66

3/7/94 218 20 171.99 378.83

4/7/94 239 21 159.51 351.35

5/16/94 266 27 143.26 315.54

6/23/94 292 26 148.22 326.48

8/3/94 319 27 167.67 369.32

9/9/94 340 21 173.99 383.23

10/16/94 364 26 171.68 378.16

11/22/94 392 26 151.19 333.01

1/24/95 424 32 159.93 352.27

2/24/95 446 22 135.36 298.15

3/22/95 465 19 150.26 330.96

5/8/95 485 20 137.76 303.43

6/6/95 506 21 160.06 352.56

6/26/95 520 14 109.91 242.09

7/19/95 534 14 89.29 196.68,

stopped early to

use brine for ersatz testing

8/21/95 556 22 157.99 348.00

9/14/95 573 17 105.01 231.31

10/23/95 599 26 196.02 431.76

The recycle filter replacements and the amounts of water processed through each filter are shown

in table 12 and plotted in figure 34. The average lifetime of the filters was 20.3 days of operation.

The duration of operation of the VCD–5A through November 9, 1995 was:

Total hours powered 21,650

Hours in Shutdown 816

Hours in Normal 2,960

Hours in Standby 17,027

Hours in Transition 847

Hours on the still motor 3,107

Hours on the fluids pump 3,076

Hours on the purge pump 1,285

An additional 459 kg (1,011 lb) of wastewater was processed through April 24, 1996 (including the

Purge Gas Test).

Table 12. VCD–5A wastewater processed between filter replacements.
42

4.5.1 VCD–5A Test Events and Anomalies.

The significant events and anomalies that occurred during testing of the VCD–5A are listed in

table 14.

The first anomaly occurred during checkout testing of the VCD–5A at LSI when the flex spline

failed in a gear speed reduction mechanism in the Harmonic Drive for the fluids pump (see fig. 10). At

that time the drive had operated for about 400 hr. The failed part was analyzed at MSFC, however, a

definite cause of the failure could not be determined because the failure surfaces were smeared due to

the assembly operating after the component had sheared. (See the third anomaly for more information.)

The drive was replaced with a new one of the same design. Previously the Harmonic Drives had

operated for much longer without failure, as shown in table 2.

The second anomaly was the failure of the wastewater feed line check valve on January 14, 1993

which allowed wastewater to flow back into the external transfer tank. This did not adversely affect

operation of the VCD and no immediate action was taken to replace the failed valve. The procedure was

changed to include closing the manual valve at the VCD interface after transfers of wastewater from the

facility supply.

Figure 34. VCD–5A 25 μm pore size recycle filter performance.

The Purge Gas Test was conducted for three weeks to collect purge gas samples for analysis to

ensure that the purge gases would not create a safety hazard during flight experiment operation. The test

was halted on April 24, 1996 due to persistent high compressor motor current draws and high compressor temperatures.11, 12 For the Purge Gas Test, the amounts of wastewater processed and the distillate

produced are summarized in table 13.

0

50

100

150

200

250

300

350

400

450

0 5 10 15 20 25 30 35

Days of Use of a Filter

Mass of Water Processed (lb) per Filter

0

20

40

60

80

100

120

140

160

180

200

Mass of Water Processed (kg) per Filter
43

Table 13. Purge gas test wastewater processing.

 Test DayUrineProcessed kg (lb)DistillateProduced kg (lb)% Recovery

1 

Batch 1

12.11

(26.68)

12.55

(27.65)

103.6

1 

Batch 2

12.21

(26.90)

11.37

(25.05)

93.1

2

20.22

(44.54)

18.89

(41.60)

93.4

3

25.03

(55.13)

23.70

(52.20)

94.7

4

11.71

(25.79)

10.79

(23.77)

92.2

5

16.91

(37.25)

15.89

(35.00)

94.0

6

12.31

(27.12)

11.42

(25.16)

92.8

7

10.31

(22.71)

9.53

(20.99)

92.4

8

9.11

(20.06)

7.97

(17.56)

87.5

9

6.29

(13.85)

6.17

(13.64)

98.5

10

5.61

(12.35)

5.08

(11.20)

90.7

11

6.01

(13.23)

5.49

(12.10)

91.5

12

5.71

(12.57

5.06

(11.14

88.6

Event/Anomaly Description

Fluids pump stopped due to harmonic drive failure.Test startedFeed line check valve allows back flow into the external transfer tank.Harmonic drive failure.Purge pump failure.Compressor differential pressure sensor (P2) failure.Waste recycle pressure sensor (P3) failure.Peristaltic purge pump tubing particles.Condenser pressure sensor (VP1) failure.High T1, high T2, high K1, and water coming out purge line. (Compressor gears worn out after 4831 hours of operation.)Facility vacuum used to assist the purge pump during Purge Gas Testing.Compressor and still will not rotate.

Date

Occurred

10/20/921/12/931/14/933/30/936/25/937/2/938/9/931/11/948/26/9411/9/956/27/96

Actionee

Hutchens, Long, SalyerHutchens, Long, SalyerHutchens, Long, SalyerHutchens, Long, SalyerHutchens, Long, SalyerHutchens, Long, SalyerHutchens, Long, SalyerHutchens, Long, SalyerWieland, Long, SalyerWieland, Long, Salyer

12/17/927/19/946/24/937/1/937/9/937/19/942/8/9412/21/941/19/967/31/97

Action to Resolv

Harmonic drive replaced. Cause 

Procedure change to close valve 

transfer.

Determined misalignment cause

Failed electronics in the signal c

No action required since the sen

evaluation and is not included in 

Flight-like sensor installed. New 

corrosive environment that caus

An inspection will be made perio

buildup of material.

Replaced with sensor made of H

 Replaced compressor gears and 

Compressor and still bearings re

personnel.

Anomaly 

Number

 VCD-5A-1  VCD-5A-2 VCD-5A-3 VCD-5A-4 VCD-5A-5 VCD-5A-6 VCD-5A-7 VCD-5A-8 VCD-5A-9VCD-5A-10

Date

Closed Out

Bold indicates that a flight-like component is affected

Table 14. VCD–5A significant events and anomalies.
44

The third anomaly was another failure of the fluids pump, after 51 days of testing at 362 hr of

operation. The failure was similar to that which occurred during checkout at LSI. A flex spline in the Harmonic Drive of the fluids pump failed in both cases. The exhaustive 3-month investigation which followed

determined that the failures resulted from a slight horizontal misalignment (0.127 mm (0.005 in.)) introduced into the pump drive shaft during its assembly at the hardware supplier. The manufacturer (Harmonic

Drive Technologies) said that misalignment of the spline could overstress it and lead to fatigue failure. The

potential for this problem may have been introduced into the pump during retrofit at the hardware vendor

(to support the drive shaft at both ends, see sec. 2.3.2 about the retrofit), since during previous testing when

the pump drive shaft was a cantilever design the Harmonic Drive operated for a much longer period of time.

The vendor has implemented use of a new alignment jig during hardware assembly to ensure proper alignment. This jig will be used for flight hardware assembly. The pump was sent back to the supplier, the part

replaced, and the misalignment corrected. Testing resumed on June 25, 1993, but the purge pump did not

receive power, due to the fourth anomaly.

The fourth anomaly was failure of the purge pump electronics. This problem was traced to a failed

power converter and capacitor on the purge pump controller card. These items were replaced and testing

resumed on July 2, 1993. This failure did not affect any flight-like components.

The fifth anomaly occurred when the VCD–5A was restarted on July 2, 1993 and the compressor

differential pressure sensor (P2) was nonfunctional. No actions were taken since the P2 sensor is not critical

to data evaluation and is not included in the flight configuration.

The sixth anomaly was failure of the waste recycle pressure sensor (P3) on August 9, 1993. This

sensor is flight-like in function (although the flight sensor will be somewhat different). LSI provided a

temporary replacement sensor so the failed sensor could be analyzed. The temporary sensor was installed

on August 30, 1993. Even without the P3 sensor, system backup features would allow operation of the

VCD–5A.

The seventh anomaly was related to the Norprene tubing used in the peristaltic purge pump. This

pump uses the same tubing as the fluids pump although it pumps a two-phase mixture which is mostly gas.

This application was found to cause spalling of the Norprene which resulted in clogging of the gas/liquid

separator with Norprene particles. The initial resolution suggested by the hardware supplier was to add a

filter downstream of the pump to prevent gas/liquid separator clogging. An inspection of the air/water

separator was made every 30 days to avoid buildup of particles.

The eighth anomaly was failure of the condenser pressure sensor (P1). This sensor was replaced

with a sensor made of Hastelloy C, a high nickel, molybdenum, and chromium alloy that is more resistant

to corrosion.

The ninth anomaly involved high temperature alarms and liquid coming out of the purge line. The

VCD–5A was deactivated until repairs could be made by LSI. The operating time on the compressor gears

and the drive belt was estimated to be 4,831 hr including time before the Life Test began. The compressor

gears and the centrifuge drive belt were found to be worn and were replaced. This anomaly and field service

is discussed further in section 4.5.2.
45

The tenth anomaly was failure of the compressor and centrifuge to rotate due to worn

compressor and still bearings. More torque was required than the motor generated. The compressor and

still bearings were rebuilt by MSFC personnel.

Facility vacuum was used to assist the purge pump when leakage exceeded the pump capacity to

adequately evacuate the pump housings and purge the condenser. The facility vacuum was connected as

shown in figure 35.

During test days 613 through 665 the VCD–5A processed 460.0 kg (1,011.3 lb) of waste feed

averaging about 3.6 lb/hr. The recycle filter tank was replaced on test days 626 and 651.

4.5.2 VCD–5A Field Service

Beginning on September 25, 1995 there were alarms and shutdowns due to high compressor

temperatures. On November 9, 1995 (test day 612), testing was halted due to continued degradation

even with the facility vacuum assisting, indicated by gradually increasing temperatures and current load,

leading to shutdown. The symptoms at that time were:

1. Excessive noise from the compressor

2. High current loads—From the normal 6 to 7A the current increased to 10 to 12A with a startup

spike up to 19A (see fig. 36)

3. Compressor temperatures increased from the normal 77 °C (170 °F) to >93 °C (200 °F). This

appears to stem from the high operating pressure inside the distillation unit (see fig. 36)

4. Slippage of the centrifuge during startup was occurring more frequently.

Coolant

Out Coolant

In

Cooling

Jacket

Inlet

Manifold

Purge Line

Casing

Connection

Casing

Connection

Fluids

Pump

Purge

Distillation

Pump

Assembly

Outlet Manifold

Facility

Vacuum Cold Trap

Gas/condensate

Figure 35. Facility vacuum connection to the purge and fluids pumps.
46

Also, moisture was still found in the moisture trap in the facility vacuum line which indicated

leakage of ambient air into the pump housing or through the pump tubing.

Figure 36. VCD–5A current, temperature, and pressure profiles in November 1995.

A field service was arranged to correct the problems. Due to a government furlough, the field

service was postponed until January 16, 1996. Prior to disassembly, a pressure check was performed that

showed no leakage into the still. The VCD–5A was then transitioned to normal mode. A loud noise came

from the VCD–5A and the compressor motor drew excessive current (17A). The VCD–5A was switched

off and disassembled.

The following conditions were noted upon disassembly of the VCD–5A:

• An O-ring seal was missing between the condenser end plate and the drum. However, there was

no indication of liquid leakage, so the metal-to-metal contact apparently provided an adequate

seal.

• Some slight corrosion was evident between the condenser end plate and the drum spokes, as

shown in figures 37 and 38.

0

50

100

150

200

250

11/9/95

12:00 AM

11/9/95

2:24 AM

11/9/95

4:48 AM

11/9/95

7:12 AM

11/9/95

9:36 AM

11/9/95

12:00 PM

11/9/95

2:24 PM

11/9/95

4:48 PM

11/9/95

7:12 PM

11/9/95

9:36 PM

11/10/95

12:00 AM

Time

Temperature (°F) or Pressure (mmHgA)

0

2

4

6

8

10

12

14

16

18

20

Current (A)

VP1 (mmHgA)

VT1 (°F)

VI1 (amps)
47

Figure 37. VCD–5A end plate showing light corrosion.

Figure 38. VCD–5A distillation drum spokes showing light corrosion.
48

• The wastewater injection tube had a small “blob” of solids (3.2 to 6.4 mm (1/8 to 1/4 in.) thick)

around the end of the tube, as shown in figure 39. The opening of the injection tube was not

restricted. This material was hard and was removed as a “chunk.”

Figure 39. VCD–5A wastewater injection tube and product water pickup tube.

• The compressor gears showed wear, with a gap of 0.330 to 0.419 mm (0.013 to 0.0165 in.)

rather than the desired 0.152 mm (0.006 in.), but there were no chips or missing teeth. There

was a coating of Vespel lubricant dust on components of the compressor, as shown in figure 40.

Examination under a microscope also showed metallic particles on the Vespel gear. The

recorded time of use for this set of gears is 4,831 hr of cyclic operation. The established life limit

for these gears is 12,000 hr of continuous operation. The condition of the gears indicated that

they had reached the end of their useful life.

product water

pickup tube

wastewater injection tube
49

Figure 40. VCD–5A disassembly showing old compressor gears.

• The centrifuge drive belt from the compressor to the drum was stretched about 14 percent. The

recorded time of use for this drive belt is 4,831 hr, and the condition indicated it had reached the

end of its useful life.

New compressor gears were installed and aligned. The backlash gap measured between 0.102

and 0.152 mm (0.004 and 0.006 in.). The VCD–5A was then reassembled. On January 17, 1996, the

VCD–5A was transitioned to normal mode. The VCD–5A ran well for 30 min and was returned to

standby mode. The motor current (I1) was still slightly high at 13A. The VCD–5A was left in standby

overnight to detect any significant pressure leaks. On January 18, 1996, the measured overnight pressure

leakage was only slight (from 37 to 47 mmHg). A second test run was performed for about an hour with

no degradation in performance. Again, I1 was slightly elevated at 13A. The VCD–5A was disassembled

and a new centrifuge drive belt installed. The compressor gears looked good and the backlash gap

remained the same. The VCD–5A was reassembled and restarted. After running for about an hour, I1

jumped from 10A to 18A and the VCD–5A alarmed to shutdown mode. No specific cause could be

found, but it was thought to be at least partly due to the VCD–5A having been dried out when it was

disassembled (dry air doesn’t remove as much heat from the compressor as moist air) or too high
50

pressure in the still, which makes the compressor work harder, therefore increasing the current load and

operating temperature. The VCD–5A was restarted, and after 3 hr another jump in I1 caused a shutdown.

The VCD–5A was again restarted and ran well the rest of the evening (5 hr). The VCD–5A ran well

again on January 19, 1996 for 3.5 hr. I1 stayed around 8A.

However, after a period of no operation (such as over a weekend), the unusual behavior was repeated

and shutdown occurred about one hour after startup on the following Monday. When the unit was

restarted, again, it operated normally and on subsequent days during the week operation was normal. On

Monday of test week 159, January 22, 1996, the condenser pressure increased to 54 mmHg and the

VCD–5A required additional power to bring the pressure down to normal operating conditions (32 to 45

mmHg). I1 started at 15A and after 15 min dropped to 12.6 A. I1 then jumped to 18A after 45 min in

normal and an alarm caused a shutdown. The VCD–5A was immediately restarted and ran nominally

with I1 remaining around 8A. The VCD–5A ran nominally for the remainder of the week, as shown in

figures 41 and 42.

Figure 41. VCD–5A compressor temperature (T1) after repairs in January 1996.

6 0

8 0

100

120

140

160

180

200

1/22 6:00 1/22 9:00 1/22 12:00 1/22 15:00 1/22 18:0

DATE

VT1 (°F)

Temperature (°F)

VT1 (°F)

1/22 6:00 1/22 9:00 1/22 12:00 1/22 15:00 1/22 18:00

Date
51

Figure 42. VCD–5A compressor motor current (I1), condenser pressure (P1), and compressor

differential pressure (P2) after repairs in January 1996.

0

1 0

2 0

3 0

4 0

5 0

6 0

1/22/96 1/22/96 1/22/96 1/22/96 1/22/ 9

DATE

VP1 (mmHgA)

VP2 (mmHgD)

VI1 (amps)

On Monday of test weeks 160 and 161, shutdowns were caused by a spike in I1 of the compressor

motor. During troubleshooting in February 1996 to determine the cause of the high current draw during

startup, the following actions were performed with the indicated results:

• Software changes were made to increase the duration of the initial purge, and facility vacuum

was used to “prepurge” the pump casings. These changes helped, but high current draw still

occurred during startup after an extended period (a couple of days) of no operation.

• The purge pump unit that was on the VCD–5 was installed on the VCD–5A to determine whether

the purge pump was the source of the problem. Operation improved somewhat, but was still not

optimal. Another concern, that may be related, is that corrosion was found in the coolant lines

when the VCD–5 purge pump was installed on the VCD–5A. This had not caused significant

problems but if severe enough, this corrosion could restrict the coolant flow such that insufficient

cooling of the purge gases occurs.

• The line connecting the purge pump and fluids pump casings was disconnected and the fluids

pump casing was connected to facility vacuum. Measurement of the vacuum showed that leakage

was occurring. Application of sealant around the pump motor drive shafts helped, indicating that

leakage had been occurring around the drive shafts as well as through other openings in the

pump casings. Another source may be leakage through the electrical connectors on the pump

casing.

A longer purge was required to compensate for the still leakage over the weekend. Still leakage was

not as great during the week because the VCD–5A was in Standby only overnight. The VCD–5A

continued to run through test week 168, however, the compressor temperature was higher than nominal.

VPI (mmHgA)

VP2 (mmHgD)

VI1 (amps)

1/22/96 1/22/96 1/22/96 1/22/96 1/22/96

Date

mmHg or A
52

4.5.3 VCD–5A Operation Summary

From mid-1993 to late-1995 performance was essentially nominal. The problems that did occur were

easily corrected.

From November 9, 1995 to the end of testing, startup and operation were increasingly assisted by

facility vacuum due to increasing leakage. The compressor gears installed in January 1996 initially

solved the high compressor temperature (T1) problem. However, as the VCD–5A life test continued,

problems developed with high motor current draw (I1) and high compressor temperatures (T1). Leakage

in the VCD–5A was greater than could be compensated for by using the facility vacuum. Except for

startup on Mondays, when the VCD–5A had not operated for 2 days, the VCD–5A could have run

without the facility vacuum, but purge periods would have been longer, so the facility vacuum was used

whenever the VCD–5A was running. That the weekend downtime created a problem indicates a leak

into the still or pump housings which raised the internal pressure too high for the purge pump to

overcome. Life testing of the VCD–5A was halted after completion of the Purge Gas Test on

April 24, 1996.

4.5.4 Proposed Modifications

To address the problems experienced with the VCD–5A, the following modifications have been

funded in FY98:

• Modify the pump drive shaft seals to make them flight-like (fluids pump and purge pump).

• Replace the tubing in the purge pump.

• Replace the demister with a flight design (not related to the problems described above).

• Replace the recycle/filter tank with a flight design (not related to the problems described above).

In addition, the purge algorithm or setpoints may need to be modified and this modification

implemented in the ISS VCD/UPA.
53

5. TEST RESULTS AND LESSONS LEARNED

The results of the life testing of the VCD–5 and VCD–5A have led to numerous improvements in the

flight design. For example, lessons learned about the VCD relate to the critical nature of pump drive

mechanism alignment and the impacts of quality control on system performance. Although the problems

have been resolved, the number of problems relating to quality control and the sensitivity of hardware

performance are causes for concern. General results and lessons learned, and specific results and lessons

learned about each component for the VCD–5 and VCD–5A are discussed in the following sections.

5.1 General Results and Lessons Learned

The operating lifetimes of VCD components are listed in table 15. The lifetimes of most of the

components are greater than the duration of the life test. The times indicate time of operation of that

component, excluding standby and shutdown conditions, except where “operation” is continuous such as

the WSA and FCA. The overall production rates and the performance of each component are discussed

below.

Table 15. VCD component lifetimes.

Component Lifetime

Wastewater storage assembly > 21,000 hr (test duration) (not replaced)

Fluids control assembly > 21,000 hr (test duration) (not replaced)

 - Waste recycle pressure sensor (P3) > 21,000 hr in the wastewater environment

Fluids pump assembly

 - Harmonic Drive > 2,676 hr of operation when properly aligned, otherwise <400 hr

 - Norprene tubing > 3,076 hr in use (not replaced)

Distillation assembly

 - Compressor motor > 3,107 hr of operation (not replaced)

 - Compressor gears 4,800 hr of operation (includes time before the Life Test began)

 - O-ring drive belt 4,800 hr of operation (includes time before the Life Test began)

 - Condenser pressure sensor (P2) >1,600 hr

Recycle filter tank

 - Filter (dual 25 μm pore size spiral wound) average 20.6 days of operation

 - Filter (single 10 μm pore size, pleated) insufficient run time to determine

Pressure control assembly > 21,000 hr (test duration) (not replaced)

Purge pump assembly

 - Harmonic Drive > 1,285 hr of operation when properly aligned, otherwise <400 hr

 - Norprene tubing > 1,285 hr of operation (but spalling indicates a limited life when

used in the purge pump) (not replaced)

 - Gas/liquid separator unknown, due to contamination by Norprene particles

 - Pressure regulator unknown, due to contamination by Norprene particles

Sensors no flight-like sensor failed

Valves no flight-like valve failed
54

5.1.1 Variation of Production Rate

The calculated average production rates of the VCD/UPA’s that have been tested at MSFC have

shown significant variation, ranging from 1.48 to 2.04 kg/hr (3.25 to 4.50 lb/hr). The reasons for this

variation relate to:

• Hardware variability due to differences in pump performance, quality control, etc.

• Operational variability due to shutdowns, component failures, facility variability, etc.

• Methods for calculating the production rate.

Regarding the calculation methods, during the course of testing VCD/UPA’s at MSFC, the data has

been recorded in different manners for different tests. The single largest variable has been the transition

time from standby to normal and from normal to standby. For some testing, transition times were not

separately recorded, resulting in apparently reduced production rates. The duration of the transition

times also has varied considerably due to hardware condition and operation procedures. Thoroughly

evacuating the purge pump and fluids pump casings reduces the transition durations, thereby increasing

the effective processing rate when transition periods are used in calculating the processing rate.

Another factor is calculating the production rate using the product water versus using the input

wastewater. When input wastewater is used for the calculation the processing rate is higher, obviously,

than when the product distillate is used.

The effects of using different methods to calculate the processing rate are shown in table 16. While it

is likely that the production rate of the VCD–5 was greater than the production rate of the VCD–5A, due

to the variability in transition durations the calculated production rates shown in the table cannot be

directly compared. This was not realized for all testing and the normal operating duration was not

always recorded. To ensure accurate comparison of different test runs, the same procedures for

calculating the production rate must be used. It is recommended that input wastewater mass, product

distillate mass, and the time in normal be recorded and used in the calculations for future testing and

operation.

Table 16. Average processing rate calculations.

VCD–5 VCD–5A

During WRT Stage 10 Jan. 12, 1993—Nov. 9, 1996

Input Wastewater Mass 1,262.4 kg (2,777.3 lb) 5,198 kg (11,449 lb)

Product Distillate Mass 1,092.0 kg (2,402.5 lb) NA

Duration of Operation

 Including Transition 565 hr 3,807 hr

 Normal Only NA 2,960 hr

Production Rate

 Wastewater ÷ Normal NA 1.76 kg/hr (3.87 lb/hr)

 Wastewater ÷ (Normal + Transition) 2.23 kg/hr (4.91 lb/hr) 1.37 kg/hr (3.01 lb/hr)

 Distillate ÷ Normal NA NA

 Distillate ÷ (Normal + Transition) 1.93 kg/hr (4.25 lb/hr) NA

NA = not available
55

5.1.2 Wastewater Supply

The check valve between the external wastewater supply tank and the WSA failed early in the

test period for both the VCD–5 and VCD–5A. This valve corresponds to the flight valve between the

urinal and the WSA. The cause of the failure was due to insufficient spring constant to keep the spring

from being deformed while being in one position for extended periods. While this spring is not flightlike, it points out an aspect which should be evaluated in the flight valve.

5.1.3 Instrumentation and Valve Failures

During troubleshooting it was found that a capacitor had failed and caused a power converter to

also fail on one of the circuit cards. Both faulty parts were replaced and the repaired circuit card returned

to the signal conditioner.

Valve V3, between the pump housing and the distillation unit, was not opening properly due to

incorrect wait timer commands from the EPROM (which had been inadvertently set incorrectly) and the

VCD–5A was shutdown. The wait timer was reset to the correct duration.

5.1.4 High Conductivity of Product Water

At startup high conductivity of the product water usually occurs after the still has been

pressurized above the normal operating pressure. This anomaly has not been resolved. Particles from the

compressor Vespel gear were found in the product water of all VCD/UPA’s which may contribute to

high conductivity readings.

5.1.5 Materials

Particles of Norprene tubing from the purge pump have been found in at least three VCD units

(the VCD–5, VCD–5A, and a development VCD/UPA). The life of the purge pump may not be affected,

but Norprene particles have clogged the gas/water separator and the pressure regulator, and have been

found in the product water.

Norprene tubing is intended for use in mostly liquid pumping, while in the VCD/UPA purge

pump there is mostly gas in the fluid stream being pumped, which increases mechanical wear and

degradation (spalling). In addition, the manufacturing process can leave particles of tubing material

loosely attached to the internal wall of the tube and flow through the tube will detach the particles.

The problems experienced with the Norprene tubing in the purge pump have resulted in the

possible addition of a filter to the flight design. The life of this filter is being specified to be consistent

with the purge pump assembly to minimize routine maintenance requirements. Although the problems

have been resolved, the number of problems relating to quality control and the sensitivity of hardware

performance is cause for concern. Degradation of the fluids pump and purge pump Norprene tubing

must be eliminated or controlled in order to avoid premature failure of the gas/water separator, the

pressure regulator, valves, and sensors. If a more durable tubing material is not feasible then a filter

downstream of the fluids pump is needed. Cleaning the tubing with high pressure water or gas prior to

installation will remove existing particles.
56

5.1.6 Leakage

When new, the purge pump tubing may have been capable of removing air that leaked in but

over time degraded to the point where it cannot perform adequately even with the assistance of the

facility vacuum. Because of this possibility, it is not known whether the leakage has increased or the

capability of the purge pump to deal with leakage has declined, or both. Samples collected from the

VCD–5 purge pump contained bits of material that appear to be the tubing material, indicating spalling

of the material which could lead to degradation in performance. In addition, corrosion in the VCD–5

fluids pump led to leakage through the housing which was very likely in the a significant factor. The

flight VCD will have pump housings made of titanium.

5.1.7 Harmonic Drive Failure

Lessons learned about the VCD also relate to the critical nature of pump drive mechanism

alignment. During previous testing using the Harmonic Drive, this failure did not occur. One design

change that may have affected this was the use of an additional bearing support for the motor instead of

the previous single-point cantilever attachment, which apparently was more tolerant of misalignment.

Although the test hardware misalignment may have resulted from a pump retrofit, the flight design has a

similar drive mechanism alignment requirement. The investigation of failures experienced in the fluids

pump has concluded that fatigue caused by a horizontal misalignment was the major contributor and that

when such a misalignment occurs, the drive life will not exceed 400 hr. The hardware supplier has

implemented use of a new alignment jig during hardware assembly to provide proper alignment. This jig

will be used for flight hardware assembly. Although the problem appears to have been solved, the

sensitivity of the VCD to such problems indicates a lack of design robustness and a need for close

attention by quality control personnel to prevent such problems during flight unit assembly.

5.2 VCD–5 Test Results

The test results are described below for each component.

5.2.1 Wastewater Supply Tank

No hardware problems were related to the wastewater supply tank. When operating on Earth, any

free gas in the supply wastewater collects at the top of the tank where the outlet line is located, leading

to high compressor temperature alarms when the gas is injected into the distillation unit.

5.2.2 Fluids Pump

On test day 17 the fluids pump housing and drive shaft seal were found to be leaking, at a rate of

15 to 20 mmHg/hr. This leakage reduces the effectiveness of the purge pump for maintaining a suitable

vacuum, therefore reducing the processing rate.
57

5.2.3 Purge Pump

Vacuum leakage into the VCD–5 still was higher than expected. When the pressure in the still

cannot be maintained low enough, performance is decreased and a shutdown may occur. The most likely

source was the purge pump drive shaft seal and a purge valve, which seemed to have failed, as well as

leakage through the back pressure regulator and fluids pump. These leaks, in combination, caused the

purge pump to lag behind in evacuating the still and not be able to keep the pressure sufficiently low.

The resolution was to replace the faulty valve, tighten the pump housing, and change the control

software for the purge algorithm, so the pump stayed on longer during the purge. This change to the

software also made it more tolerant of leakage so that a small leak will not cause a dramatic change in

pressure. This was successfully tested using a facility pump to assist the purge pump.

The purge algorithm provides a 1 min purge of the pump casing, then a 2 min purge of the still. If

P1 reaches 27 mmHg before 2 min then it repeats another 2 min purge. Double or triple purges indicate

leakage of ambient air (noncondensable gases). An initial increase in pressure indicates leakage in the

purge pump.

During investigation of the difficulty for the purge pump to maintain a suitable vacuum it was

found that the Norprene tubing in the purge pump was spalling. Small pieces of Norprene material

were found in the back pressure regulator, which prevented proper sealing, and in the gas/water

separator. This resulted in leakage into the still and blockage of purge gas flow, respectively, and

reduced performance. The pressure regulator was cleaned and reinstalled.

5.2.4 Distillation Assembly

During troubleshooting, the VCD–5 was disassembled and the still drive belt was found to have

been incorrectly installed. This had resulted in numerous low speed alarms. The belt was reinstalled

correctly and the problems did not recur. It was also found that an O-ring seal had not been installed.

Use of a fan to cool the compressor motor, increasing the duration of the purge, installation of a sample

port that also vented free gas from the WSA, and replacement of the Vespel gear all helped to reduce

the compressor temperature and eliminate shutdowns and warnings.

5.2.5 Recycle Filter Tank

No problems were found with the operation of the recycle filter tank. Filter replacement and tank

cleaning was performed as expected.

5.2.6 Gas/Water Separator

During repairs on January 13, 1994 the gas/water separator was removed and particles of

Norprene tubing material were found inside, blocking the separator inlet and fouling the filter medium.

The separator was cleaned and back flushed before being reinstalled. When Norprene particles were

found again later, the gas/water separator was replaced.
58

5.3 VCD–5A Test Results

The test results are described below for each component.

5.3.1 Wastewater Supply Tank

No hardware problems were related to the wastewater supply tank. As with the VCD–5, the

presence of free gas in the wastewater supply tank may have contributed to high compressor temperature

alarms.

5.3.2 Fluids Pump

The fluids pump failed during pretest checkout after about 400 hr of operation due to a sheared

flex spline in the Harmonic drive. This drive was replaced prior to beginning the life test, but after 360

hr of operation the same failure occurred again. The cause was a slight horizontal misalignment. The

hardware supplier made an alignment jig to ensure accurate installation and the problem did not recur.

Leakage around the pump drive shaft seals was also found to be significant (as for the VCD–5).

The flight VCD/UPA will have redesigned seals.

5.3.3 Purge Pump

Norprene tubing particles were shed from the purge pump, as with the VCD–5.

5.3.4 Distillation Assembly

High compressor temperature and low centrifuge speed alarms occurred occasionally beginning

367 and 434 days, respectively, into the life test.

The high temperatures were likely due to excess friction in the compressor gears as they

approached the limit of their recommended lives. Through November 9, 1995, the operating time on the

compressor gears and the drive belt was about 4,831 hr including time before the Life Test began. These

components were near the end of their design life. Another contributing factor may be free gas in the

wastewater feed.

At startup, high conductivity of the product water usually occurs after the still has been

pressurized above the operating pressure. This anomaly has not been resolved. Particles from the

compressor Vespel gear were found in the product water of all VCD/UPA’s which may contribute to

high conductivity readings.

The metal demister was found to shed tiny slivers of stainless steel (like steel wool) which were

found in the phase separator with the Norprene tubing particles. This has only occurred on one VCD

but may be a generic problem. The slivers were similar to metal taken (easily removed) directly from the

demister inside the distillation unit.
59

When the VCD–5A was disassembled during troubleshooting it was also found that an O-ring

seal had not been installed between the stationary bowl and the separator plate (as with the VCD–5).

5.3.5. Recycle Filter Tank

The waste recycle pressure sensor (P3) failed on August 9, 1993 and a temporary sensor was

installed on August 30, 1993. The temporary sensor failed on February 1, 1994 and was removed. The

materials in these sensors could not tolerate the wastewater environment. Both are flight-like in function,

but not material. A new, flight-like sensor made of Inconel 718 was installed on July 19, 1994.

A leak was found in the waste recycle relief valve, caused by corrosion of the pipe connector

fittings. The fittings were replaced with identical fittings, flight-like in function only. A vacuum leak test

was performed on the fluids pump assembly and the purge pump housing, and no leaks were found.

The filters lasted an average of 20.62 days each.

5.3.6 Gas/Water Separator

As with the VCD–5, particles of Norprene tubing material were found in the gas/water

separator, causing as much as 60 percent blockage.
60

6. CONCLUSIONS AND RECOMMENDATIONS

The VCD life test program has successfully met the objectives as stated in section 1.

Recommendations concerning the ISS VCD/UPA can be grouped into four categories: design, quality

control, materials, and operation.

6.1 Design

Redesign of the purge pump and fluids pump drive shaft seals is recommended to prevent leakage

into the pump housings. The drive shaft seals have been redesigned for the ISS VCD/UPA. Other

potential leak sites, such as connectors, should be designed to preclude leakage, and verified to ensure

no significant leakage.

Due to the potential for metal slivers to be shed from the stainless steel demister, an alternative

design is recommended. The demister has been redesigned to be a membrane-type for the ISS

VCD/UPA.

Wearing of the Vespel gear in the compressor is expected because the Vespel gear adds lubrication

as it wears. However, traces of Vespel were found in the product water, in all operating VCD/UPA’s. A

filter in the product water line is recommended to ensure that the allowable particulate level of the

product water will not be exceeded.

The wastewater feed tank design, with the outlet at the top, allows free gas to collect and contribute

to overheating and other problems during ground testing. This effect would not likely occur in orbit

since any free gas will be distributed in the liquid, but must be considered during ground testing. Unless

this free gas is removed prior to beginning a processing cycle, high compressor temperatures and high

current draws will result when the gas is injected into the distillation unit.

6.2 Quality Control

The Harmonic Drives of the purge and fluids pumps must be properly installed with careful attention

to the drive mechanism alignment.

Care must be taken during assembly to ensure proper installation of components such as the

centrifuge drive belt and O-rings.
61

6.3 Materials

To prevent premature failure of sensors and valves, it is essential that materials be compatible with

the environments where the sensors or valves are located, especially the harsher environments such as

the wastewater recycle lines. It is recommended that long-term material compatibility be verified for all

components.

To prevent particles of Norprene tubing from the purge pump from clogging components, it is

recommended that the tubing be cleaned with high pressure water or gas prior to installation to remove

any particles present due to the manufacturing process, and that a filter be added downstream of the

purge pump to ensure that any new particles generated do not cause problems.

To prevent corrosion of the fluids pump and purge pump in the event of leakage, the housings will be

made of titanium for the flight VCD.

6.4 Operation

It is very important to thoroughly evacuate the fluids pump and purge pump housings prior to

evacuating the still, and to have a sufficient purge duration prior to transitioning to normal operation

from standby. It is recommended that the purge duration be increased for this reason. This control

change to increase the duration of purge will be implemented on the ISS VCD/UPA and all currently

operating VCD/UPA’s.
62

7. REFERENCES AND BIBLIOGRAPHY

Cited references and other related documents are listed below.

7.1 References

1. Perry, J.L.: “Environmental Control and Life Support System (ECLSS) Life Testing Program

Interim Report,” memo ED62(27-93), NASA/Marshall Space Flight Center, August 27, 1993.

2. McGriff, Cindy F.: “Space Station Freedom Environmental Control and Life Support System:

Urine Processor Assembly (Vapor Compression Distillation) Life Test Plan,” memo ED62(59–

92), NASA/Marshall Space Flight Center, May 27, 1992.

3. Carter, D.L., et al: “International Space Station Environmental Control and Life Support System

Phase III Water Recovery Test Stage 10 Final Report,” Marshall Space Flight Center, in press,

1998.

4. “Life Test VCD-VA Flex Spline Failure Anomaly Review Meeting,” Marshall Space Flight

Center, December 4, 1992.

5. Scheidt, J.: “Data Acquisition Software Description and User Guide for Use in the ECLS Test

Facilities,” MFOP–FA–ETL–320, Marshall Space Flight Center, October 31, 1986.

6. Dotson, C.: “PACRATS Users Guide,” Marshall Space Flight Center, in press, 1997.

7. Simpson, W.G.: “Flight-Like Hardware for UPA Life Testing,” memo WGS–4–8, Life Systems,

Inc., April 7, 1993. This memo details the degree of flight-like characteristics for each

component of the VCD–5 and VCD–5A.

8. Carter, D.L.; Holder, D.W.; and Hutchens, C.F.: “International Space Station Environmental

Control and Life Support System Phase III Water Recovery Test Stage 9 Final Report,” NASA

Technical Memorandum 108498, Marshall Space Flight Center, September 1995.

9. Carrasquillo, R.L.; Carter, D.L.; Holder, D.W., Jr.; McGriff, C.F.; and Ogle, K.Y.: “Space Station

Freedom Environmental Control and Life Support System Regenerative Subsystem Selection,”

NASA Technical Memorandum 4340, Marshall Space Flight Center, AL, February 1992.

10. Carter, D.L.: “Protocol For the Participation of Human Research Subjects in the Environmental

Control and Life Support System Phase III Test Program: Water Recovery Test Stages 10 & 11,”

unnumbered, NASA, Marshall Space Flight Center, ED62/Life Support Systems Branch, August

1996.
63

11. Hutchens, Cindy: “Test Plan for the Purge Gas Analysis of the VCD-VA,” internal memo ED62

(36–96), Marshall Space Flight Center, May 7, 1996.

12. Long, D.A.; and T.D.: “Vapor Compression Distillation Subsystem (VCD–VA) Gas Purge Test

(VGP) Report,” ECLSS/TECH/EL96–003, Marshall Space Flight Center, July 30, 1996.

7.2 Bibliography

Chang, B-J: “Failure Analysis Report of Harmonic Drive,” TR–1305–5, Life Systems, Inc., June 3,

1993.

Chiu, Charles Y.; Perry, Jay L.; Salyer, Blaine H.; and Tatara, James D.: “Preliminary Results of NASA

ECLSS Life Testing,” 24th International Conference on Environmental Systems and 5th European

Symposium on Space Environmental Control Systems, SAE paper number 941463,

Friedrichshafen, Germany, June 20–23, 1994.

Chiu, C.; Salyer, B.; and Tatara, J.: “Environmental Control and Life Support Systems, Life Test

Quarterly Report #9,” Contract No. NAS8–40369, Ion Electronics, Huntsville, Alabama, October

1995.

Chiu, C.; Salyer, B.; and Tatara, J.: “Environmental Control and Life Support Systems, Life Test

Quarterly Report #11,” Contract No. NAS8–40369, Ion Electronics, Huntsville, Alabama, February

1996.

Chiu, C.; Salyer, B.; and Tatara, J.: “Environmental Control and Life Support Systems, Life Test

Quarterly Report #12,” Contract No. NAS8–40369, Ion Electronics, Huntsville, Alabama, May

1996.

Hutchens, C.: “Life Systems, Inc. Vapor Compression Distillation Subsystem Technical Interchange

Meeting Trip Report,” memo ED62(17–94), Marshall Space Flight Center, April 13, 1994. This

memo summarizes the status of the VCD–5 and VCD–5A, specifically regarding the check valve

failure, the presence of Norprene tubing in the pressure regulator and the gas/liquid separator,

vacuum leakage in the VCD–5, high conductivity of the product water at the beginning of a

processing cycle (especially when the still has been pressurized above normal operating pressures),

and low production rate of the VCD–5A.

“Life Test VCD–VA Flex-Spline Failure Anomaly Review Meeting,” presentation, December 4, 1992.

McGriff, Cindy F.: “Space Station Freedom Environmental Control and Life Support System: Urine

Processor Assembly (Vapor Compression Distillation) Life Test Plan,” NASA, Marshall Space

Flight Center, MSFC/ED62, May 1992.

Perry, J. L.; and Ray, C. D.: “Environmental Control and Life Support System Life Testing

Requirements Revision A,” memo ED62(107–92), Marshall Space Flight Center, November 17,

1992.
64

Perry, J. L., Chiu, C. Y.; Salyer, B. H.; and Tatara, J. D.: “Environmental Control and Life Support

System Life Testing Program Status,” memo ED62(45–94), Marshall Space Flight Center,

September 27, 1994.

Ray, C. D.: “Space Station Environmental Control and Life Support System Supporting Development

Plan,” memo DA01(ED62–20), April 19, 1994.

Ray, C. D.; and Minton-Summers, S.: compilers, “International Space Station ECLSS Technical Task

Agreement Summary Report,” NASA Technical Memorandum 108508, Marshall Space Flight

Center, May 1996.

Simpson, W. G.: “Response to Technical Questions Relating to the VCD–V (POST unit) and VCD–VA

Units,” memo WGS–5–6, Life Systems, Inc., May 6 ,1993. This memo documents responses to

questions relating to the Harmonic Drive failure, the fluids pump assembly repair, a slow leak into

the distillation unit of the VCD–5, purge duration, and other questions.
65

APPROVAL

FINAL REPORT ON LIFE TESTING OF THE VAPOR COMPRESSION

DISTILLATION/ URINE PROCESSING ASSEMBLY (VCD/UPA)

AT THE MARSHALL SPACE FLIGHT CENTER (1993 TO 1997)

P. Wieland, C. Hutchens, D. Long, and B. Salyer

The information in this report has been reviewed for technical content. Review of any information

concerning Department of Defense or nuclear energy activities or programs has been made by the MSFC

Security Classification Officer. This report, in its entirety, has been determined to be unclassified.

_________________________________________

W.R. HUMPHRIES

DIRECTOR, STRUCTURES AND DYNAMICS LABORATORY
66

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August 1998

Final Report on Life Testing of the Vapor Compression Distillation/

Urine Processing Assembly (VCD/UPA) at the Marshall Space 

Flight Center (1993 to 1997)

P. Wieland, C. Hutchens, D. Long, and B. Salyer*

George C. Marshall Space Flight Center

Marshall Space Flight Center, Alabama 35812

National Aeronautics and Space Administration

Washington, DC 20546–0001

Unclassified–Unlimited

Subject Category 54

Standard Distribution

ECLS, VCD, urine processor, UPA, life support, International


Space Station

Unclassified Unclassified Unclassified Unlimited

Wastewater and urine generated on the International Space Station will be processed to recover

pure water using vapor compression distillation (VCD). To verify the long-term reliability and

performance of theVCD Urine Processor Assembly (UPA), life testing was performed at the

Marshall Space Flight Center (MSFC) from January 1993 to April 1996. Two UPA’s, the VCD-5

and VCD-5A, were tested for 204 days and 665 days, respectively. The compressor gears and 

the distillation centrifuge drive belt were found to have operating lives of approximately 4,800

hours, equivalent to 3.9 years of operation on ISS for a crew of three at an average processing

rate of 1.76 kg/h (3.87 lb/h). Precise alignment of the flex-splines of the fluids and purge pump 

motor drives is essential to avoid premature failure after about 400 hours of operation. Results

indicate that, with some design and procedural modifications and suitable quality control, the

required performance and operational life can be met with the VCD/UPA.

NASA/TM—1998–208539

M–887

76

A05

Technical Memorandum

Prepared by Structures & Dynamics Laboratory, Science and Engineering Directorate

*Ion Electronics, Huntsville, Alabama