NASA CONTRACTOR REPORT 177421

CONTROLLED ECOLOGICAL LIFE SUPPORT SYSTEMS (CELSS)

CONCEPTUAL DESIGN OPTION STUDY

M, 0LESON

R, L. 0LSON

BOEING AEROSPACE COMPANY

SEATTLE,, WASHINGTON

PREPARED FOR

AMES RESEARCH CENTER

UNDER CONTRACT NAS2-11806

I ASA

National Aeronautics and

Space Administration

Ames Research Center

Moffett Field, California 94035
FOREWORD

The Conceptual Design Option Study- Controlled Ecological Life Support System (CEL_S)

Program Planning Support (Contract NAS2-11806) was initiated February 28, 1984 and

completed December 31, 1985. This contract was an extension of the Regenerative Life

Support/Controlled Environment Life Support System contract completed in 1983 for

NASA Ames Research Center. The Contracting Offieerts Representative was Dr. Robert

MaeElroy.

This study was conducted by the Boeing Aerospace Company, Seattle, WA.

The study final report is contained in two volumes as shown below:

D180-29490-1 Final Study Results

D180-29490-2 Final Study Appendix C ECLSS trade analysis
ACKNOWLEDGEMENTS

The Boeing CELSS study team wishes to thank the following persons for their assistanceDr. M. Averner

Dr. B. Bugbee

Mr. F. Buck

Mr. P. Budininkas

Dr. T. Hoshizaki

Dr. R. MacElroy

Dr. M. Modell

Dr. K. Mori

Dr. C. Mpelkas

Dr. R. Mudget

Mr. T. Parks

Dr. D. Raper

Mr. D. Smernoff

Dr. T. Tibbitts

Univ. of New Hampshire

Univ. of Utah

General Electric Lamp Co.

Chamberlin National

NASA Jet Propulsion Laboratory

NASA AMES Research Center

Modar Inc.

Keio Univ. at Tokyo

Sylvania Lighting Center

Univ. of Massachusettes

Food and Agro Systems

Univ. of North Carolina

NASA AMES Research Center

Univ. of Wisconsin at Madison

ql,

ii
CONTENTS

FOREWORD

ACKNOWLEDGMENTS

CONTENTS

GLOSSARY

LIST OF FIGURES

LIST OF TABLES

1.0

1.1

1.2

1.3

1.4

INTRODUCTION

OVERVIEW

BACKGROUND

STUDY OBJECTIVES

STUDY APPROACH

2.0

2.1

2.2

2.3

2.4

2.5

STUDY SUMMARY

DESIGN OPTION DEVELOPMENT AND REVIEW

PLANT GROWTH SUPPORT SYSTEMS

PARAMETRIC ANALYSIS

SENSITIVITY ANALYSIS

RESEARCH AREA SUMMARY

3.0

3.1

3.2

3.3

3.4

3.5

3.6

CELSS CONCEPTUAL DESIGN

CONCEPTUAL DESIGN PHILOSOPHY

CONCEPTUAL DESIGN EVALUATION

CONCEPTUAL DESIGN SELECTION PROCESS

CELSS SUPPORT SYSTEM

GUIDELINES

CELSS STUDY ASSUMPTIONS

4.0

4.1

4.2

4.3

PRELIMINARY DESIGN

CELSS SYSTEMS DEFINITIONS

SYSTEM DESCRIPTION

SYSTEM INTEGRATION

Page

i

ii

el.

Ul

vi

vii

X

1

1

1

2

2

5

9

13

17

18

19

23

23

23

31

34

38

39

41

42

45

88

°°°

III
CONTENTS

Page

5.0

5.1

5.2

PARAMETER ESTIMATES

COST ESTIMATING PROCEDURE

WEIGHT ESTIMATING PROCEDURE

91

91

97 V

6.0

6.1

6.2

6.3

6.4

6.5

SENSITIVITY ANALYSIS

SENSITIVITY ANALYSIS APPROACH

SYSTEM PARAMETRICS ANALYSIS

ILLUMINATION SYSTEM COMPARISON

ELECTRICAL POWER UTILIZATION ANALYSIS

CROP-MIX ANALYSIS

99

99

101

108

118

123

7.0

7.1

7.2

7.3

RESEARCH AREAS

BIOLOGICAL RESEARCH AREAS

ENGINEERING RESEARCH AREAS

ADVANCED TECHNOLOGY RESEARCH AREAS

129

130

135

137

8.0

8.1

8.2

8.3

8.4

8.5

8.6

8.7

8.8

8.9

8.10

8.11

8.12

8.13

8.14

8.15

8.16

CELSS REQUIREMENTS

PLANT ILLUMINATION REQUIREMENTS

PLANT NUTRIENT SUPPLY REQUIREMENTS

WATER MANAGEMENT REQUIREMENTS

THERMAL CONTROL REQUIREMENTS

AUTOMATION REQUIREMENTS

PLANT GROWTH STRUCTURE REQUIREMENTS

ATMOSPHERE CONTROL SYSTEM REQUIREMENTS

EXTERNAL PLANT STIMULI REQUIREMENTS

PHYTOTOXICITY CONTROL REQUIREMENTS

PLANT GAS EXCHANGE REQUIREMENTS

PLANT SPACING REQUIREMENTS

UTILITY ROUTING REQUIREMENTS

ACCESSIBILITY and MAINTENANCE

DATA COLLECTION and MANAGEMENT REQUIREMENTS

PLANT HARVEST SYSTEMS REQUIREMENTS

FOOD PROCESSING SYSTEMS REQUIREMENTS

141

142

142

142

143

143

143

144

144

144

144

144

145

145

145

145

146

v

iV
8.17

8.18

8.19

CONTENTS

WASTE REGENERATION REQUIREMENTS

PATHOGEN CONTROL REQUIREMENTS

ROBOTIC SYSTEMS REQUIREMENTS

Page

146

146

146

BIBLIOGRAPHY A-1

APPENDIX B: TABLES OF REFERENCE VALUES B-1

APPENDIX C: CELSS DOCUMENTS PUBLISHED AS NASA REPORTS C-I
GLOSSARY

CELSS

CRES

ECLSS

ECS

HID

IR

LEO

ORU

PCM

PGU

ppm

PRICE H

RLSR

ROM

SCWO

SE&I

STS

UV

eontroUed environment life support system

corrosive-resistant steel

environmental control and life support system

environmental control system

high-intensity diseharge

infrared

low Earth orbit

orbital replacement unit

parametric cost model

plant growth unit

parts per million

RCA parametrie eost model for hardware

Regenerative Life Support Researeh (program)

rough order of magnitude

supereritical water oxidation

system engineering and integration

Space Transportation System (shuttle)

ultraviolet

Y

vi
Figure

2.0-1

2.0-2

2.0-3

2.1-1

2.1-2

2.1-3

2.2-1

3.2-1

3.2-2

3.2-3

3.2-4

3.2-5

3.2-6

3.2-7

3.2-8

3.2-9

3.2-10

3.2-11

3.2-12

4.2-1

4.2-2

4.2-3

4.2-4

4.2-5

4.2-6

4.2-7

4.2-8

4.2-9

4.2-10

LIST OF FIGURES

Space Station Module Cost Comparison

Cost per Man by CELSS Module Length

Cost per Man vs Number of Men Supported by one CELSS

Module

Accordion Tray Concept

Automated Warehouse Concept

Expandable Tray Concept

Example CELSS Module

Example Conceptual Design Rating Sheet

Conveyor Belt PGU

Honeycomb Tray Concept

Parallel to Hull Concept

Warehouse Tray Stack

Cone Shaped Growth Chamber

Radial Tray Concept

Baloney Slice Concept

Clam Shell Growth Concept

Rotating Tray Stack

Hybrid Tray Stack

Accordion Tray Stack

Plant Growth Unit Configuration

Plant Growth Pattern

CELSS Tray Concept

Tape Application to Tray

CELSS Seeder

Solar and Fluorescent Baseline Plant Lighting System

Solar Collector Detail of Fiber Optics

Fiber Optic Luminaire

Combined Solar and Fluorescent

Cooling Air Flow Diagram

Page

8

10

10

11

14

24

25

25

26

27

27

28

28

29

30

30

31

46

47

48

49

5O

55

56

5'7

58

62

vii
Figure

4.2-11

4.2-12

4.2-13

4.2-14

4.2-15

4.2-16

4.2-17

4.2-18

4.2-19

4.2-20

4.2-21

4.2-22

4.2-23

4.3-1

LIST OF FIGURES

Nutrient Mist Sprayers

Nutrient Flow Diagram

Nutrient Injection Detail

Nutrient Regeneration Subsystem

Air Circulation Flow Diagram

Atmosphere Contaminant Control

Waste Management System Flow Diagram

Super Critical Water Oxidizer

Super Critical Water Oxidation Space Station

Applieation

Plant Flow Path Through CELSS

CELSS Plant Harvester

CELSS Robots

CELSS Module Packaging

Preliminary Design Integration Flow

Page

64

64

66

66

69

71/72

73

73

74

77

78

81

86/87

89

5.1-1

5.1-2

5.1-3

Space Station Module Cost Comparison

Costing Information Flow Diagram

Boeing Aerospace Company Cost Estimating

Approach Flowchart

93

94

95

6.2-1

6.2-2

6.2-3

6.2-4

6.3-1

6.3-2

6.3-3

6.3-4

6.3-5

CELSS Electrical Power Configuration Comparison

CELSS Volume Configuration Comparison

CELSS Cost Configuration Comparison

CELSS Mass Configuration Comparison

Fresnel Lens--Fiber Optic Solar Light Collector

Illumination System Power Comparison

Combined Solar and Fluorescent Illumination System

High Intensity Discharge Lighting System

Combined Fiber Optic--High Intensity Discharge

Illumination System

Illumination System Mass

Illumination System Cost Comparison

106

106

107

107

109

II0

112

113

114

115

116

.°°

VXU
Figure

6.3-8

6.4-1

6.4-2

6.5-1

6.5-2

6.5-3

6.5-4

LIST OF FIGURES

IUumination System Volume Comparison

Electrical Power Load Cycle

CELSS Running Average Power

Crop Mix Mass Comparison

Crop Mix Cost Comparison

Crop Mix Volume Comparison

Crop Mix Power Comparison

Page

117

121

122

127

127

128

128

ix
LIST OF TABLES

Figure

2.0-1

2.0-2

2.2-1

Summation of CELSS Module General Parameters

CELSS System Ordered by Impact on Parameters Values

Plant Growth Unit Summary

Page

6

9

14

4.2-1

4.2-2

4.2-3

4.2-4

4.2-5

4.2-6

4.2-7

4.2-8

4.2-9

CELSS

CELSS

CELSS

CELSS

CELSS

Plant Growth Tray Assembly

Seeder Mechanism

Growth Unit Lighting--Conducted Sunlight

Thermal--Cooling

Plant Growth Nutrient Supply

CELSS Atmosphere Control

Super Critical Water Oxidation System Component Listing

CELSS Harvester Components

CELSS Robot Components

51

51

60/61

63

68/69

72

76/77

8O

84/85

5.1-I CELSS Module Cost Summary 92/93

6.2-1

6.2-2

6.2-3

6.2-4

6.3-1

6.3-2

6.4-1

6.5-1

6.5-2

Peak Electrical Demand 102

Volume Comparison 103

Cost Comparison 104

Mass Comparison 105

Fiber Optic Based IlluminationSystem Comparison 115

Fiber Optic Based Illumination System Parameters Comparison 117

CELSS Power Loading Flow Chart 119/I 20

Potential CELSS Crop Productivity Figure 124

Crop Mix Analysis 126
1.0 INTRODUCTION

1.1 OVERVIEW

This document contains the results of the Controlled Environmental Life Support System

(CELSS) study (NAS2-11806) originated by NASA Ames Research Center. The study

approach, analysis procedures, results, and source data are presented in this document.

Response to the CELSS Interim Conceptual Design Review document, published in

August 1984, provided the commentary and discussion used in shaping the format and

focus of this document. The document presents various options for the development of s

CELSS design for a future space station. Research facilities that may lead to the CELSS

module, such as the Life Sciences Research Facility and Ground-Based Plant Growth

demonstrator, may benefit from the study results, as well as planning for longer range

missions (e.g., lunar base and manned missions to Mars).

1.2 BACKGROUND

The CELSS program is a long-term research and development effort that addresses the

future needs of NASA for recycling and regenerating materials needed for human

sustenance during extended space missions. Long-term research and development

programs always have inherent uncertainties associated with them. Uncertainties occur

when mission specifics are not identified: specific outcomes of research tasks cannot be

foreseen, inventions cannot be predicted, and specific test results cannot be scheduled.

The solution to these uncertainty problems is to develop a flexible, planned approach of

supporting research and development for long-term generic missions.

NASA has taken signifieant strides toward establishing long term goals and identifying

potential mission areas requiring CELSS technology. Mission area identification was

addressed in the Regenerative Life Support/ControLled Ecological Life Support Mission

Model Study (NAS2-11148) conducted for NASA by Boeing Aerospace Company. Five

generic missions were identified where the application of CELSS technology would be

beneficial. In addition, critical data gaps were identified in the CELSS data base with

respect to CELSS weight and cost estimates. These data base gaps were addressed

during the current study by developing and analyzing a series of conceptual designs.
1.3 STUDYOBJECTIVES

The primary study objectives are to develop weight and cost estimates for a projected

CELSS module based on preliminary designs. The estimates are to be compared with

those used in the Regenerative Life Support Research/Controlled Ecological Life Support

System Program Planning Support (Transportation Analysis) Study (NAS2-11148), This

comparison will determine the validity of the conclusions reached in the transportation

analysis.

Study objectives are met by--

a. Developing a minimum of six Space Station CELSS module conceptual designs.

These designs are for review by NASA and other CELSS related personnel and are to

be used as a springboard to selecting a preliminary baseline design candidate.

b. Conducting a CELSS module preliminary design effort to identify components and

subsystem relations.

c. Conducting a sensitivity analysis of the CELSS subsystems.

d. Developing a research topical listing to aid in directing future research and

development efforts.

1.4 STUDY APPROACH

A four-step study approach was used to attain weight and cost estimates. First, multiple

conceptual design options were developed for review by NASA and personnel associated

with the CELSS program. Second, a CELSS module preliminary design was produced

based on the first step and comments received from NASA during the conceptual design

stage. Third, weight and cost estimates were developed using preliminary design data

for equipment lists and sizings. Fourth, a parametric sensitivity analysis was conducted

using the preliminary design cost and weight data.

The documentation was developed parallel the study effort. This documentation

approach allows the reader to follow the design flow and decision processes that went

2
into preliminary design development. A research ares topical identification listing was

formed that identified research areas where insufficient information was available to

support CELSS module design. The topical listings are divided into three research area

categories that are key to CELSS design development: biologics] research, engineering

research, and technology development.

3
This page intentionally left blank

4
2.0 STUDY SUMMARY

Study results support the premise that an operational CELSS research module will not

create unacceptable demands on Space Station support services. A general CELSS

requirement summary (Table 2.0-1) indicates that -

a. The CELSS system would require approximately 56.9 m 3 of space per man for plant

growth area, support equipment, and access.

b. The degree of CELSS system automation can be very high; one man can tend the

growing area for a large crew (8 to 12 crewmen) with time for other duties. The

daily average for man tending should be less that 0.5 hr for routine tasks.

Co Based on preliminary design, approximately 21 000 kg will need to be lifted into

orbit for a two-man module. This includes module and equipment but not initial

consumables.

d. Based on preliminary design, resupply should not exceed 764 kg per 90 days, but is

highly dependent on CELSS system design.

e. Electrical power requirement can range from an average of 6.8 kW for a fiber optic

solar collector system to 87.7 kW for a 24-hr/day artificial lighting system.

Electrical power requirement for maintaining continual illumination (using a

combination of 16-hr solar and 8-hr artificial lighting) are 8 kW light side and 17 kW

dark side. This provides full intensity (750 _mole/m2/s) light-side illumination using

solar collectors and one-tenth intensity (75 umole/m2/sec) dark-side illumination

using artificial lights.

Pgl_gOiNO t_GE BLANK NOT FILMF.,D
Volume requirement

Crew time

Lift to orbit including module

Resupply per 90 days

Electrical power (all fiber optic system)

Electrical power (all artificial light system)

Illumination level (full)

Illumination level (power conservation mode)

56.9 m 3 per man

0.5 hr per day

21 000 kg

763.9 kg

6.8-kW average

87.7-kW average

750 Ijmol/m2/h

75 _mol/m2/h

Table 2.0-1. CELSS General Parameters Summary

Comparing Space Station module costs (fig. 2.0-1) shows that the CELSS module costs

($590 million ) are slightly lower than those for a comparable laboratory module (e.g.,

755

5O0

Module

cost

(x million $)

250

653(B)

612(A 2-1_""_

17 _ _N.Xx _

kX\\\\

122 _\\\\_

_xx\\x

_\\N\N

_98_

_xxxx\

_xxxx _x_x_x

'359 ......

_xx_x

xxxxx _xxx_x

\\_\\ xxxxx_

\\\\\

3333_ "////-

/////

..... :162,

114: .....

Figum _0-1. Space S_gon

590(C)

8 ...-_m...

\\NN\\

\\\\\\

_\x\\x

_\\\\x

_\_xxx

_xxxx

_\\\\\

_\\\\X

_492;

_X\\\\

_xxxxx

_\\\\x

_\x\\x

_\N\\\

,',,\\\_

k\\\\\

_NN\\\

N\NN\N

K\\\NN

x\\\\_

_\\\\\

_\\\\x

\\\\\\

:.:.:.:.:-:.:.: iiiiii iiiiii!i So.are

IIII GFEoutriding

Lab outfitting

lab module

(A) Estimate based on SS Phase B work

(B) Estimate based on ref(12)contract re0ort

(C) Cost adjusted estimate from this study

Est. _ 110(A)

-N/////,

;90;

V////

Module Cost Comparison
Life Science Research module, $653 million, or Manufacturing and Technology

Laboratory module, $612 million). Further analysis demonstrates that cost per man can

be reduced as the module size is increased (fig. 2.0-2) because overhead costs remain

relatively constant for support equipment when additional plant growth units (PGU) are

70

60-

50-

A

40-

C

_=

_=

: 30-

20-

10-

!

0 5O

A 20 M2 per man ]

\ • 13.5 M2 per man |

I

Cost per man ($ in millions)

Figure 2.0-2. Cost Per Man by CELSS Module Length

added. Additional improvement in CELSS cost effectiveness occurs when plant growth

area required to support one man is decreased (fig. 2.0-3). The improvement is in both

cost per man and an increased number of men supported per module.

This study validates the power, mass, volume, and cost conclusions developed in the

Regenerative Life Support Research Controlled Ecological Life Support Study

(RLSR/CELSS), conducted in 1982, by showing the systems weights used are reasonable

and correct. The break-even calculations in the RLSR/CELSS study are found to be

based on realistic masses, power, and cost values. The RLSR/CELSS study demonstrated

a potential break-even point of 7.5 years for low Earth orbit (LEO) CELSS system based

on a mass of 6750 kg/person. Data from the current study estimate a mass of

6472 kg/person; a 4.1% difference. This suggests that inclusion of a CELSS module, even

in the currently proposed Space Station, could be beneficial economically and

7
15

E

E

z

12.

9'

6-

Z_ 20 M2 per man

& 13.5 M2 per man

I1 7 M2 per man

0 I

o 200 350

Co=t per man (S in millions)

Figure 2.0.3. Cost Per Man Versus Number of Men Supported by One CELSS Module

scientifically. Volume comparisons are within 10%, 56.9 m 3 current study versus 51.15

m 3 RLSS/CELSS. Electrical power value difference stems from different approaches to

lighting systems. The RLSS/CELSS study uses a continuous, artificial illumination

system emitting 500 _mol/m2/s. This study uses combined fiber optic solar collectors

and low-level artificial illumination to provide 750_mol/m2/s during light-side orbit and

75 _ mol/m2/s during dark-side orbit.

The design phase produced 11 concepts for evaluation and testing. A PGU structure was

developed that held plant trays in place and allowed for positioning plant growth support

equipment (e.g., nutrient supplies and lights). The selected PGU uses an accordion growth

tube to economize on volume. The nutrient supply system features quick-disconnect

fittings. Plant harvesting and processing designs are totally automatic for normal

operations. Robotic gardening concepts are explored that use current robot capability

combined with rudimentary artificial intelligence. This combination significantly

reduces the human workload. Supercritical water oxidation (SCWO) provides a system

with excellent potential for recovering nutrient salts. Using recovered salts can reduce

the need for nutrient resupply from Earth by 40% to 90% depending on waste system

configuration.
A sensitivity analysis, using the developed weight and cost data highlighted the

parameters that most heavily impact CELSS design. This sensitivityanalysis included

mass, cost, electricalpower, and volume evaluations. Systems that have the greatest

affect on parameter values are identifiedin table 2.0-2.

Parameter Mass Cost Volume Power

IST Module Lighting PGU Lighting

2ND Lighting Module Module Thermal

3RD Thermal Robotics Lighting Nutrient supply

Table 2.0-2. CELSS Systems Ordered by Impact on Parameter Values

Research area listings are provided to aid in determining future CELSS research topics

(sees. 2.6 and 6). These listings reflect the areas where insufficient data was available

for preliminary design. Listings are broken into biological research areas, engineering

research areas, and advanced technology research areas.

Major study topics are summarized in the following subsections. Succeeding chapters

provide detailed discussion of each topic.

2.1 DESIGN OPTION DEVELOPMENT AND REVIEW

Seventeen alternative conceptual designs were considered in this study. Three of these

designs were selected for further review and refinement.

a. Accordion tray concept (fig. 2.1-1).

b. Automated warehouse concept (fig. 2.1-2).

e. Expandable tray concept (fig. 2.1-3).

These design options were selected based on consideration of -

a. Minimizing CELSS module mass. Reduced mass decreases launch costs and impact

on Space Station attitude control.

b. Minimizing cost for each kilogram of edible biomass produced per day.

9
S_ded trays ---) /--- Nutrient feed in

in for grow_ / /

Area available -.-% _ / i

for equipment

L_.\ ._=_=_l _j / Mechanism rotates . _ _'_-7/_Plants Air space

Curve _ _ / II [ "]r4J_. out to clear trays _" A-A conforms _._. '/L.--_'1_

tO module __ / "".r_ [ for removal Plant _" __ source

hull / gro.wth----_ :_ _ Light

mC°_m°n-"_ untt _ '7

mechanism

A-A Light panels

L L- Newly seeded tray

Super critical

water oxidizer

Figure 2. I- 1. Accordian Tray Concept

ma

ii

I=

L Mature

New trays Medium growth

F /_ /-_ Large growth

-"=°= t"-

-,- __,..I _

,i_l__l '' "

_uL_tL:,,ij,,,_8_ ,,

plants

Plant arrangement -- / \ /-_ ImZ ' I I

eleven racks distributed [ "X_ ,''/ "_ I J

on both s,des t __.._ _ _ __

. " -, -i/r . -

\\ I 1 ./" _ _0.o._,.,,oo

common module

Figure 2.1-2. Automated Warehouse Concept

10
Newlyseeded,compressedtray

Mediumgrowth,

partially expanded

Full height,

fully expanded

tray,

fully expanded

from shelfto shelf

&---Robot Robottrack

Figure 2. 1-3. Expandable Tray Stack

C. Minimizing volume for each kilogram of edible biomass produced per day. Study

guidelines dictate maximum volume available of 145 m 3 from which to feed two or

more crew members. This requires compact PGUs with high packing densities within

the module.

de Minimizing power consumed for each kilogram of edible biomass produced per day.

Electrical power is supplied by Space Station on an allocation basis. CELSS design

must minimize power consumption to operate with allotted power while producing

maximum food.

e. Mechanical reliability must be high to prevent plant loss due to equipment failure.

High reliability also conserves crew time by reducing maintenance and repair

activities.

f. Automated operation is necessary to reduce crew involvement. Crew time is a

limited resource that must be conserved. The appropriate application for automation and robotic systems, while expensive, can recover cost in crew-time savings.

1]
2.1.I Conceptual Design Option Evaluation

Design options cover a wide range of possibilities. Final selected design for CELSS may

vary slightly or significantly from those identified in this study. Each design considered

during the study conceptual design phase is discussed below. All options are workable

and can be built with existing technology. Designs selected are the compromised

versions that produced the best yield at a minimal penalty to Space Station resources.

2.1.1.1 Accordion Concept

Accordion tray stack (fig. 2.1-1) met design criteria best and was selected for further

development. Tray structure is more complex in accordion tray stack than in the other

two concepts. This design used volume 77% better than the other two concepts because

accordion trays permit small seeded areas to expand with plant growth; this also

eliminates transplanting. This design is capable of growing different crops without major

changes in the plant growth system.

2.1.1.2 Automated Warehouse Concept

Warehouse tray stack (fig. 2.1-2) is a conventional vertical stack of growth trays. Height

of each compartment is tailored to the growth phase of the plants. Seedling spacing is

the same as for mature plants due to nonexpanding trays and study guidelines prohibiting

transplantation. This results in an inefficient use of volume in early growth stages.

Warehouse tray stack is relatively simple to build and service.

2.1.I.3 Expandable Tray Concept

Expandable tray stack (fig. 2.1-3) combines vertical stacking of warehouse tray stack

with accordion tray concept. This improves volume usage as trays are compressed during

early stages of growth. Because trays must be placed in a limited number of tray

openings sized for different stages of growth, the expandable tray stack does not

optimize lighting as plants spend a period of time in compartments that are too tall for

the plants. This places light source outside optimum range from the plant canopy.

Expandable tray stack is mechanically simpler than accordion tray stack, but more

complex than warehouse tray stack. Other design options are not pursued for reasons

12
outlined in section 3.0. These designs may be feasible under conditions not currently

being considered for this contract.

2.2 PLANT GROWTH SUPPORT SYSTEMS

2.2.1 Plant Growth Unit

CELSS plant growth ares uses a portion of a module similar to the common module but

the floor and ceiling are farther apart.

There are 24 PGUs in the plant growth area. Each unit occupies a volume approximately

30 in wide by 66 inches high by 56 in deep. The floor-to-ceiling distance is occupied by

two PGUs. Each side of the module has 12 PGUs (fig. 2.1-1).

Each PGU has eight trays,each tray is8 in square by 56 inlong when the collapsibletray

bellows are extended. Tray structure is compressed along its length after a seedcarrying tape is applied over matched slots in the tray. The collapsed tray is inserted

into the PGU in the positionclosest to the floor or ceiling(fig.2.2-!),as the position1.

As plants in lower trays (position 8) mature, they are removed from the PGU. The

bottom of allPGUs is in the vicinityof the module center (i.e.,plant tray movement is

from floorand ceilingtoward the center of the module).

When mature plants are removed from the PGU, volume isavailable for the next tray to

move down. This leaves space in the beginning of the PGU cycle for a newly seeded,

collapsed tray to be inserted.

Table 2.2-1 summarizes PGU parameters. Electricalpower data are expressed as the

peak power demand for each system. Duty cycles express the percentage of time the

system will be operating. (See see. 6.4 for detailed electricalpower demand and duty

cycle discussion.)When more than one major system iscalled out under a singleheading,

ss in this case each major system is called out with it's related parameters.

13
Tray in ---,,,-

¢l

E

8

E

p.

Tray out ..,.-..

Tray out -"-'-

E

8

E

>.

pTray in

Light source

No. 1

Plant growth

unit

No. 8

No. 8

Plant growth

unit

No. I

Figure 2.2-1.

f

Module ceiling direction

Direction of module long axis

Outboard

Module floor direction

1

Trays

Tray Positioning in PGU

System

Plant growth

Seeder

Seed cartridges

Nutrient sup

Atmo etl sys

Harvester/proe

Waste regen sys

Plant lighting

Thermal

Robots

MASS COST VOLUME

QTY (kE) (MS) (m3)

24 704.8 22.6 41.2

1 32.8 16.8 .3

set 257 2 .3

1 879.9 82.2 1.1

1 691 7.4 5.9

1 465.1 49.3 1.3

1 691 74.5 1.2

1 6062.8 167.3 8.1

1 2106.4 24.6 .9

set 245.8 73.2 1.4

PEAK

PWR

0

.2

0

2.2

6.6

1.0

5.6

12

2.4

.3

DUTY

CYCLE

0

7%

0

100%

10096

5%

14%

6696

66%

23%

Table 2.2-1. Plant Growth Unit Summary

14
2.2.2 Nutrient Supply

The nutrient supply system consists of a main reservoir supply of fresh nutrient solution

that supplies each PGUts nutrient system that in turn supplies nutrient solution to each

plant growth tray. Sensor probes analyze the nutrient composition, and control

replenishment of exhausted ingredients. Periodically, used nutrient solution is dumped

to the waste control system and replenished from the main reservoir. Nutrient supply

parameters are summarized in table 2.2-1.

2.2.3 Atmosphere Control

The atmosphere control system maintains a constant CELSS air composition, including

humidity, and removes contaminants. Plants use carbon dioxide and give off oxygen.

Trace contaminants are given off by plants, out-gassing of plastics, the nutrient system,

and eleetromeehanieal equipment. Air is circulated to the waste management system

and contaminants are oxidized or removed by filters. Additional filtering, as required,

will be included in the air circulation cooling system. The waste management system

supplies carbon dioxide for the plants and nitrogen as required to compensate for

leakage. If additional 02, CO2, and N2 are required to maintain an optimum

atmosphere, they wU/ be furnished by stored supplies. Atmosphere control system

parameters are summarized in table 2.2-1.

2.2.4 Harvesting and Food Processing

The harvester and food processor operate together to separate edible from inedible

biomass. Edible biomass is processed to a storable condition then stored. Inedible

biomass is shunted to the waste regeneration system. Harvesting and food processing are

automated (see. 2.2.8). A tray of mature plants is placed in the harvest machine, stems

are cut and the root biomass is pulled out of the tray. The crop is separated from the

waste material and put into storage. Waste materials are ground and stored until the

next waste regeneration cycle. Harvester and food processor parameters are summarized in table 2.2-1.

2.2.S Waste Regeneration System

CELSS waste regeneration system converts organic waste material into constituents

needed for plant growth. Organic waste materials are ground into fine particles and

15
consumed in a SCWO unit. Significant power (5360w) is required for the initial heating

of the SCWO unit. Therefore, waste material is collected and stored until there is

enough for an efficient burn period. Contaminants in the air are oxidized as air passes

through the reactor, which acts as an air contaminant scrubber. Carbon dioxide and

nitrogen are gaseous reactor byproducts. These byproducts are used to maintain

atmospheric balance. Salts are recovered and used to replenish the plant nutrient

solution. Waste regeneration system parameters are summarized in table 2.2-1.

2.2.6 Plant Lighting

Lighting provides the energy source that drives the otherwise closed CELSS system.

CELSS lighting system provides high-intensity plant illumination during LEO light-side

operations. Reduced intensity illumination is provided during dark-side operations.

Sunlight is collected by a solar collector and conducted via fiber optics to the PGU for

the primary light source. Artificial light may be provided during the dark-side orbit. At

one-tenth of fuLl intensity, artificial light will be provided to conserve power. Fluorescent lights will be used for the artificial light baseline source in this study. Fluorescent

bulbs are moderately power efficient and weigh less than the high-intensity discharge

(HID) lamp with fiber optic light pipes, which is considered an alternative system. Plant

lighting system (solar and fluorescent) parameters are summarized in table 2.2-1.

2.2.7 Thermal Control

CELSS thermal control system provides the means to remove heat generated by

electricalequipment, solar illumination,and human activity. The highest heat load is

generated during light-sideorbit. Conducted sunlight on the plants will bring approximately 81,000 Btu/h into CELSS. If the SCWO is running at the same time, another

50,000 Btulh or more will be generated. Additional heat will be generated by the fan

motors used for air circulation,robot operation, and by other equipment, such as the

harvester and nutrient supply equipment. A portion of the heat may be used for Space

Station processes requiringheat input. The balance willbe dissipatedthrough CELSS and

Space Station radiators.Thermal control system parameters are summarized in table

2.2-1.

2.2.8 Robot Operation

CELSS robots are used to relieve crew-time demands. Robots perform routine

operations of planting, harvesting, and processing the food crop without human inter16
action. The robotic gardener positions the seeded plant growth tray into the PGU and

harvests the tray of mature plants. The food processor robot completes processing the

crop through the harvesting equipment. The food processor robot handles tray

preparation for reseeding, operates the seeder, and performs limited maintenance tasks.

Robotic system parameters are summarized in table 2.2-1.

2.3 PARAMETRIC ANALYSIS

Parametric analyses conducted for this study were used to support preliminary design

and sensitivity analysis. Four parameters were evaluated" electrical power, volume,

mass, and cost. Initial preliminary designs provided approximate equipment volumes.

These volumes were evaluated against CELSS module volume to determine if all systems

would fit together, iterations and refinements to systems design led to a specific set of

equipment dimensions. System design was weLt established by this [_oint, allowing call

out of materials, electronics, motors, and other specific items of equipment. These

equipment listings are compiled for use in weight estimates.

Weight estimates are conducted using the CELSS systems equipment listings (see. 4.0).

Systems requirements for strength, heat resistance, flexibility, pressures, and other

engineering variables are identified. Weights engineers compare these data to existing

models with known weights. Some adjustments are made to compensate for unique

requirements or operations. The weight of each equipment item is then added to obtain

subsystem and/or system totals. Some estimates are made for interconnecting structures, power cables, plumbing, etc. to complete the system weight estimate.

Electrical power requirements were developed for unique equipment by calculating the

mass moved, speed at which it moved, and time in operation. Fan, pumps, and other

standard-type equipment were assigned values from standard engineering references

based on equipment loading. Thermal and atmospheric control equipment power demands

are calculated for highest loading. During operations, power demands are expected to be

lower because maximum loading is rarely attained. These loading factors are evaluated

in section 6.4.

Cost estimates are based on a Boeing parametric cost model (PCM) system in

conjunction with the RCA PRICE modeling system. Both systems use equipment

breakdowns by mass, power, complexity, technology, manufacturing, testing, and

17
assemblyfactors to determine costs. These factors are integrated to determine three

cost categories: design and development, manufacturing, and systems integration and

checkout. CELSS system costs are the sum of three categories. Launch and on-orbit

operational costs are not included in this study.

2.4 SENSITIVITY ANALYSIS

Sensitivity analyses were conducted to identify the key design drivers in developing a

CELSS module. These design drivers are -

a. Electrical power consumption.

b. Plant species selection.

c. Internal CELSS module volume.

d. Thermal control.

Design drivers are selected for their CELSS mission impact. This impact is determined

by evaluating parametric values for mass, volume, power, and cost. The parameters are

then related to edible biomass produced per day per square meter. Relating parameters

to crop yield in this manner determines which systems have the greatest impact on the

overall CELSS mission to produce food for the erew.

Electrical power has the greatest effect on CELSS design. Electrical power impact is

derived from its scarcity on the operational Space Station. About 210 kW are available

for the entire station during light-side operations in 1999. Less power is available from

station fuel celts during dark-side operations. This power must sustain All station

activities, including housekeeping, life support, industrial operations, laboratories, satellite repair, and waste management. Based on current projections, sufficient power will

not be available for all of these activities. Allocations will set limits on each modulets

power consumption. CELSS module designs must conform to these limits. Power limits

constrain artificial lighting schemes, especially during dark-side operations. Total

artificial lighting at 87.7 kW (table 6.2-4) is an unacceptable design approach. Alternative direct solar lighting designs have serious thermal and safety problems. Solar

collectors, using fiber optic light pipes, presented the only viable solution. While

providing effective light-side illumination, the solar collector is inoperative during darkside operations. CELSS design has to provide a low-power lighting system to maintain

plants during dark-side operations. Limited electrical power dictates the CELSS

illumination system. Thermal control, atmospherie control, PGU, robot, and automation

18
designsare directly impacted by illumination system selection. Thus, electrical power

directly affects the major CELSS systems designs.

Crop selection must be oriented toward maximum edible biomass yield. Three factors

combine to determine yield: (1) growth period from planting to harvesting, (2) calories

contained in each gram of edible biomass, and (3)edible biomass produced per unit

growth area. These factors must be considered in combination when selecting a crop

plant. For example, wheat has a 62-<lay growth cycle, 2400-g/m2/cycle production rate,

and 3.6 cal/g. Wheat can support over three men per 3$-ft long by 14-ft diameter

module. Mixing crops to balance nutrition must consider the impact low productivity has

on size, power, mas.% and cost for CELSS designs.

Internal module volume limits the area that can be dedicated to crop production. Each

CELSS module requires a certain amount of overhead equipment for atmosphere and

temperature control, waste management, nutrient supply, and food processing and

storage. The remaining internal volume is used for PGUs. CELSS design task is to

minimize overhead penalty while increasing quantity of operational PGUs. Future

CELSS designs should consider advantages derived from larger modules. PGUs can be

added at little additional overhead penalty once the initial support equipment penalty is

paid. This requires increased module size either through greater length and/or diameter.

Increasing number of PGUs by adding small modules results in paying the full overhead

penalty each time.

[ntense plant iUumination generates heavy heat loads within the CELSS module.

Illuminating heat sources are located directly over plants. Preventing crop heat damage

requires a powerful, redundant, and integrated thermal control system. Thermal designs

incorporate atmospheric control to transport heat from plants to heat exchangers. PGU

designs were altered to aid in effectively removing heat. Waste management systems

are designed to incorporate high-efficiency liquid cooling systems. Even the robot was

slowed down to reduce heat loads generated by larger motors required for higher speeds.

All CELSS systems were designed to reduce thermal load, thereby redueing size and

power demand for the thermal control system.

2.5 RESEARCH AREA SUMMARY

Three classes of research areas were identified in this study: biology_ engineering, and

advanced technology. Biological research areas address the issue of growing plants in a

19
mitt.gravity environment. An example is plant tropism. Engineering research areas

address the questions of designing and constructing a CELSS facility. An example is

development of structures that do not contain phytotoxic off-gassing materials and are

able to withstand corrosive nutrient solutions. Advance technology research areas

address the equipment and capability that will be needed, but does not exist, to support a

CELSS facility in micro-gravity. An example is development of a fiber optic solar ray

collector that will function in a space vacuum and direct solar radiation.

Key research areas are identified in the following listing. These areas are selected from

the listing in section 7.0, which contains additional research area topics. This larger

listing identifies CELSS systems and parametric values affected by the research area.

2.5.1 Biological Research Areas

Tl_e foUowing are certain biological research areas that need immediate attention to

support further CELSS development.

a. Determine microgravity-grown plant dimensions. These dimensions impact sizing

PGUs, which consume the greatest percentage of volume in CELSS module.

bo Determine edible biomass production per unit area when grown in a microgravity

environment. Even minor changes in production can create major increase or

decrease in plant growth volume required per man.

Co Determine which organisms (e.g., algae, bacteria, fungi) can convert inedible plant

biomass to edible food stocks for humans. Recovering normally inedible biomass can

reduce both volume and energy requirements to feed each crew person.

d. Determine plant development under light- and dark-orbit cycles. [Uuminating plants

only during Space Station light-side orbit reduces electrical power and equipment

requirements. Questions exist as to plants viability, growth characteristics, reproduction, and food production rate under the Space Stations 60-min light 30-min dark

cycle.

e. Determine lowest illumination levels that maintain plant photosynthetic state. This

information supports low intensity, artificial lighting design for Space Station dark°

orbit phase. Using low-level illumination to hold plants in photoactive state may

2O
support high production levels while significantly reducing electrical load on the

Space Station.

f. Determine lighting characteristics necessary to induce phototropic response in

plants. Inducing plants to grow in a predetermined direction using light is the least

difficult tropistic response option. Alternative growth orientation procedures (e.g.,

electrical fields, chemical sprays, agitation, etc.) all add utility penalties and

complexity to CELSS design.

g. Identify high-yield plants that are adaptable to growth in CELSS. Pursue selective

breeding and/or genetic engineering to develop plants for high yields, compact size,

and rapid maturity. Plant specie_ in which all, or most, of the plant is edible are

especially valuable.

2.5.2 Engineering Research Areas

a. Develop PGU design using noncorrosive and nonphytotoxic material while maintaining lightweight structure. A highly corrosive nutrient solution and problems with

off-gassing in a closed module require careful material selection. High launch costs

dictate that PGU mass be minimized.

b. Design nutrient fluid handling system that ensures adequate supply, constant

monitoring, and prevents leaks.

C. Design plant processing unit that can process a variety of edible foods. This unit

must separate inedible from edible biomass. It should have the capability to wash,

dry, and sort edible plant products as required. Plant processing unit will store

edible materials and grind inedible material for regeneration.

do Design robotic gardener to use multiple, specialized tools for plant maintenance and

processing. Robotic gardener is a key element in CELSS automation plan. With this

robot, one crew member (on a part-time schedule) can support many additional crew

members. This unit eliminates human requirements during routine CELSS operations. Human involvement is limited to equipment maintenance and repair and

picking up the harvest for consumption.

21
2.$.3 Advanced Technology Research Areas

8. Develop solar light collection system to provide plant illumination. A lens or mirror

system focusing sunlight on fiber optic cables provides an option for conducting

sunlight into plant growth area. Cable construction, rotating joints, terminal

illuminators, and collector pointing all require development.

b. Design SCWO system for use in a mitt.gravity environment. This unit requires a

salt separation unit added to recover plant nutrients. Recovering nutrients and

releasing carbon and water from waste materials are essential processes in CELSS.

SCWO prototypes have demonstrated a potential to accomplish these goals with a

small energy-efficient system.

Co Develop physiochemieal or biologically based inedible-to-edible biomass conversion

systems to maximize return from each plant grown. Low-energy systems are

preferred even if they require slightly larger volumes and masses. Biological system

must adapt to varying waste types and quantities. Physiochemical system should not

require resupply from Earth or hazardous materials.

do Develop mercury free, low temperature, high-intensity discharge (HID) lamps. These

lamps are inherently more efficient than other artificial light sources. However,

their high temperature precludes spacing close to growing plants. Mercury

amalgams are contained in these lamps, which produce a hazardous material

handling problem. The problem is eompounded by the closed-environment system.

22
3.0 CELSS CONCEPTUAL DESIGN

3.1 CONCEPTUAL DESIGN PHILOSOPHY

The purpose of this study was was to develop design options for higher plant growth

systems for use on Space Station. These designs are for growing wheat, soybeans, and

potatoes in 8 miero-gravity environment. A CELSS module is seheduled initially to be a

research tool attaehed to the Space Station. Essentially, the total system will reeyele

water, atmosphere, and plant nutrient material.

CELSS eonceptual designs developed for this study are intended to define a closed

mierogravity higher plant growing system. An optimum design was developed within

volume and power constraints of Spaee Station. The requirement for very limited human

operational involvement dietates a highly automated system.

Designs developed for this study are based on existing technology in electronics,

automation, robotics, and biology. All systems that received serious consideration are

accommodating to automated servicing. Routine maintenance and repair times are

planned to be minimized by the use of fault-tolerant systems and/or high-reliability

parts. Only unplanned repairs and maintenance are expected to be performed by crew

members.

3.2 CONCEPTUAL DESIGN EVALUATION

PGUs comprise the largest single unit in CELSS module design. Since many PGUs are

contained in each CELSS module they heavily impact volume utilization. Designs were

examined and rated in terms of useful volume, efficiency of light distribution, reliability

of mechanical systems, ease of service, ease of harvest, cost, etc. Figure 3.2-1 is an

example of a rating sheet. Major rating criteria for CELSS systems conceptual design

are8. Minimize human involvement in CELSS.

b. Use Space Station common module primary structure.

c. Satisfy caloric requirements for two crew members.

d. Satisfy biological requirements for plants.

23
Plant

Growth

System

f

_v

_..jrFigure 3.2-1. Conceptual Design Selection by Comparison

of Design Criteria Rating Sheet

Because crew time is a criti,_al resource, human involvement in CELSS must be kept to a

minimum. This drives design to highly autonomous systems for a broad range of

operations. CELSS systems are only planned to require human attention when equipment

failureor severe plant damage occurs.

Eleven different PGUs were considered. Brief descriptionsof each of these units follow.

a. Conveyor-belt PGU (fig.3.2-2),uses two conveyors facing a common light source.

Newly seeded trays are inserted at shallow side (where lightsare close to conveyor).

Plants grow as conveyor belt slowly moves. Deep side (where lightsare far away

from conveyor) has mature plants. These are removed from conveyor for

harvesting.

So Honeycomb tray concept (fig. 3.2-3) has six-sided trays facing toward six-sided light

sources. Plants grow on two or three sides depending on tray location in pattern.

Trays plug inlongitudinallyto growth unit.

24
i, /

I +I

I I

Mature tray

out to

harvester

" F Light source shines both sides

_/ Mature tray out

Figure 3.2-2. Conveyor Belt PGU

_-- Trays

_.,/- Open s-- for growth

_T.__ Lighting

Figure 3.2-3. Honeycomb Tray Concept

25
Co

do

e.

ParaUel-to-hull concept (fig. 3.2-4) grows plants in a false wall between module

interior and hull. False walls permit module interior use for other purposes. The

robot travels against huU, is short and long, and carries harvester with it.

• Light source mounted on inside Robot

surface on hull. harvester

• Plants on outside surface of

walls, growing out towards

lights.

• Nutrient delivery to plant

roots located in walls.

• Interior volume is useable

and is same radius ashull,

permitting use of standard "_

racks.

Plants

Common

module

Walls

Lights

Figure 3.2-4. Parallel to Hull Concept

Warehouse tray stack (fig. 3.2-5) has trays on vertical racks serviced by a robot that

moves along center aisle. Trays fit into different sized slots, which places lights as

close as possible to plant canopy while allowing area for growth. As plants grow,

robot moves trays into progressively larger slots that accommodate growth.

Cone-shaped growth chamber (fig. 3.2-6) has a continuous tray moving through a

cone with light source facing inward from cone surface. Growth surface is a

coUapsible continuous tube. Slit in tube allows injection of nutrient and removal of

roots at harvest.

f.

ga

Radial tray concept (fig. 3.2-7) places trays facing outward from the module center

with the robot at the module center. Circumferential arrangement of trays uses

large available surface area for plant growth.

Baloney slice concept (fig. 3.2-8) has vertical panels that grow plants on their sides.

As plants grow, panels move laterally to allow growth and adjust lightin_ distance

from plant canopy. Panels are removed from the system for harvest.
---New trays F Medium growth

Mature plants Plant arrangement -

eleven racks distributed

on both sides

Large growth

Space Station

common module

Chamber is cone shaped.

Plants enter at small end.

As plants grow, they fill

large end of cone.

Figure 3.2-5. Warehouse Tray Stack

Mature

plants out

Flexible, recirculating

tubing is sli_ed.

/

/

/

/

Nutrient injection

through slit in tube.

Newly

seeded tube

Lights on inside

of chamber wall

Figure 3.28. Cone Shaped Growth Chamber

Harvester

Cone-shaped

growth chamber

27
reservedforsupports,

tubing,wiring,etc.

Traysupport

Robotrotatesto

anyposition,removes,

servicesandreplaces

trays.

28
he

i.

Clamshell growth concept (fig. 3.2-9) grows plants on a core facing toward the

inside of a sphere that has a light source. Plants grow on most of the core excluding

only the tube that supports core and provides nutrient plumbing.

Rotating drum concept (fig. 3.2-10) has a slowly rotating drum (one revolution per

growth cycle of 60 to 115 days). Seeding and harvesting are performed continuously

as the drum rotates.

j.

k.

Hybrid tray stack (fig. 3.2-11) has trays on vertical racks accessible from an aisle.

The racks extend from aisle to module inner hull surface. This creates progressively

deeper slots with deepest slot at module center line. Trays are built with accordion

folds so they may be collapsed to fit the shallow top slot. The trays are moved to

deeper slots as plants mature. This allows the tray to be expanded, thereby

providing more plant growth area per tray. Trays are moved from slot to slot and

finally to the harvester by robot.

Accordion tray stack (fig. 3.2-12) has expanding trays in a vertical stack with plants

growing on the sides. This unit was selected as the best CELSS PGU concept. It

Typical

hinge

Light source on

inside surfaces

of clamshell

Core

• As plants grow,

robot moves core

to progressively

larger clamshells.

• Hinged doors

open to provide

clearance for

removal of core.

tfeed

tube and core

support

Figure 3.2-9. Clamshell Growth Concept

29
Harvester Drum sterilizer

Mature

plants

Slowly

rotating

drum with

nutrient

feed

implanter

Lighting

Figure 3.2-10. Rotating Drum Concept

Drum rotates

slowly (once

every 62 days

for wheat)

Newly seeded, compressed tray

Medium growth,

partially expanded

Full height.

fully expanded

Mature tray,

fully expandeO

Robot

k

Figure 3.2-1 I. Hybrid Tray Stack Concept

"_.

from shelf to shelf

3O
Seeded trays

in for growth

Area available

for equipment

CurvQ

conforms--'_

to module

hull

Used nutrient

out

Ratchet Plant,

mechanism

A-A

Nutrient feed in

Plants Mechanism rotates _ _ Air $oace

, out to clear trays _A-A_ for removal Plant _ _ Light

Common

module

_ature Mant trays

try,

_-- Newly seeded tray

L-_ Super _iticai

water oxidizer

Figuoe 3.2-12. Accordian Tray Concept

required minimal volume while supporting maximum lighting efficiency and reliable

mechanisms.

3.3 CONCEPTUAL DESIGN SELECTION PROCESS

CELSS study employed a design process that compared design criteria analytically to

identify best-fit conceptual desis_m. This process used a series of design iterations,

criteria refinements, and design reviews. Process results are designs that satisfy CELSS

requirements.

During the CELSS study, criteria weighting (importance) changed as design options were

explored. For example, mechanical complexity was not initial/y considered a major

design driver. However, crew time is a major design driver. Therefore, CELSS was

substantially automated to minimize human interfacing with CELSS. Initial designs

tended to be mechanically complex PGUs. Evaluation revealed these mechanicaLty

complex designs decreased reliability, which increased crew maintenance and repair

time. While some mechanical complexity is unavoidable, it is neeessary to simplify

systems designs to reduce crew maintenance and repair load. During design iteration,

mechanically complex components were eliminated, if possible.

31
It wasalsodetermined that systemscould be designed that were adaptable to changes in

requirements. An example of this is the PGU. The ground rules were to grow wheat,

soybeans, and potatoes. Initial conceptual designs concentrated on sizing for wheat

growth. After the first selection of growth systems to accommodate wheat, sizing for

soybeans and potatoes were considered. PGUs that were unadaptable to changed

requirements were eliminated. PGUs that did meet increased requirements did so

because of their inherent flexibility. These designs can be changed yet again to

accommodate new requirements. This design flexibility is useful for further development. As future CELSS development occurs, the selected PGU should be capable of

changing to meet most new plant growth requirements.

Three configurations emerged from the selection process as final candidate concepts.

Selected concepts were (1) warehouse tray stack, (2) accordion tray stack, and (3) hybrid

tray stack. These concepts best satisfied design issue requirements. Suitability

determination was made by comparing concepts against individual issues and ranking

accordingly.

3.3.1 Warehouse Tray Concept

This concept configures growth trays to fit into graduated height openings in a vertical

stack (fig. 3.2-5). Nutrient is supplied by pressure-fed injectors. A vacuum system

removes excess and spent nutrients. When a tray is removed, nutrient and vacuum

systems are disconnected. Valve arrangement prevents leakage.

Lighting panels are located above openings in stack. This distributes light on a tray-bytray basis and allows regulation of light intensity for different growth phases.

As plants grow, trays are removed from their slots and transferred by a robot to taller

slots that can accommodate taller plants in the next phase of growth. This happens

incrementally until a given tray has been placed in a slot where the plant matures. At

maturity, the tray is removed entirely from the stack and transferred to harvesting

equipment.

After harvest and tray recondition, the trays are reseeded and placed in the smallest size

slots in vertical stack so growth process can be repeated.

32
The warehouse tray concept is conventional in construction. It can be built of simpleangle shapes attached by mechanical fasteners. No mechanisms are required within the

strueture for tray manipulation, the robot performs these functions.

The warehouse tray stack does not optimize volume usage. Area between racks and hull

is not used for plant growth. Light distribution is not optimal. Seeds are spaeed for

mature plant spacing requirements. Until plant canopies cover the tray surfaces, light

reaches the tray surface and creates undesirable heat.

3.3.2 Accordion Tray Coneept

The concept (fig. 3.2-12) is centered around use of trays that are accordion pleated so

they expand longitudinally. Trays are essentially rectilinear in section and expand from

approximately 36 to 60 in. Tray ends are removable for harvesting operations. This

allows robot access to tray interior to push out root masses.

The trays are arranged (fig. 3.2-12 A-A) so that plants grow out one or both sides. Trays

are stacked vertically, one tray abutting the other. They are pushed down incrementally

and expanded by a mechanism that can be either a tracked device or a tray-mounted

ratchet.

Each time trays are moved down incrementally, the nutrient delivery system disconnects

and moves clear of the tray travel envelope. When trays are repositioned, nutrient

injectors are returned to engage tray nutrient delivery orifices. Nutrient leakage is

prevented by an automatie valve system that requires firm seating of nozzles before

fluid transfer. Tubing inside trays carries nutrient to multiple misting nozzles

that spray nutrient directly onto roots. A vacuum pickup system collects spent and

excess nutrients for recycling. Tubes inside trays collect nutrient, transferring it

through exhaust nozzles similar to nutrient injectors.

The bottom trays contain the most mature plants. The tray is removed from the PGU

stack, making room for the remaining trays to move clown into the next growth position.

The tray containing mature plants (which is fully expanded) is transferred to the

harvesting area.

Harvesting equipment cuts and removes roots from the tray interior, permitting the

remainder of the plant to be pulled out and processed. The tray is then sterilized and

33
reseeded. After reconditioning and reseeding, the tray is compressed and inserted at the

top of the PGU stack to repeat growth process.

The accordion tray stack uses volume efficiently. It expands to follow module huh

contours as plants grow. A smaller lighting system can be used in early stages of growth.

The accordion tray stack permits greater concentration of light onto plants because

plants are spaced closer when younger and move apart as they grow.

3.3.3 Hybrid Tray Concept

The hybrid tray concept involves trays that have a vertical orientation similar to the

warehouse concept but expand on one axis. This means newly seeded trays can go into

openings more shallow than mature trays. Again, as plants grow, hybrid trays are

expanded and moved to larger openings in vertical stack (fig. 3.2-11).

The hybrid tray concept improves volume usage over the warehouse tray, but not as well

as the accordion tray. Improvements in lighting efficiency are similar.

These concepts were submitted to NASA for review and final selection process. The

accordion stack tray concept was selected by NASA for further development during

study preliminary design.

3.4 CEI._S SUPPORT SYSTEM

The accordion stack tray concept selection provides the base from which the remainder

of the support systems designs can be considered. CELSS support systems are -

a. Food harvesting, processing and storage.

b. Seeding equipment.

c. Robot.

d. Thermal control system.

e. Atmosphere eont_l system.

f. Plant lighting.

g. Waste regeneration system.

h. Nutrient supply system.

34
The support systems design philosophy "is to optimize for volume and conserve Space

Station resources. Highly reliable mechanical systems are preferred. Systems that

accommodate automation are preferred to reduce human workloads. Module sheU cost

optimization is accomplished by using baseline Space Station common module primary

structure.

3.4.1 Harvesting, Processing, and Storage

The harvesting, processing, and storage system was developed to ensure compatibility

between PGU, tray design, robot, and a series of design iterations to the PGU and

harvester. The resulting harvester eoneept has capability to harvest wheat, soybeans, and

potatoes. It will separate edible biomass (crop) from plant and root masses. The

attached food processing system will wash or dry erops as needed for storage. The food

processing equipment is fully automated processing plant products from harvest to

storage. Volume oeeupied by harvester is approximately one standard Space Station

equipment rack, filled from floor to eeUing.

3.4.2 Seeder

The automated CELSS tray seeder operates in conjunction with a robot to apply a seedembedded foam tape over slots in an accordion tray surface. The seed tape seals tray

slots to prevent nutrient leakage. The seeder uses a ridged roller to press tape firmly

into the tray pleated surface to ensure adhesion. A solenoid-activated knife cuts the

seed tape. Clearance is provided behind tape applicator mechanism for tray length.

The seeds are stored on tape contained in a cartridge. Unused tape remains in the

cartridge, protected against humidity and temperatures that could cause seed deterioration. The robot can remove tape cartridges from seeder, store them, and load different

seed tape cartridges into seeder. This allows use of a common seeder for all p/ants.

3.4.3 Robot

The CELS8 system concept includes robots, which are autonomous for normal operations.

The robots have the capability of handling plant trays through the entire growth process,

from seeding to harvesting. The robots notify the crew of equipment failure or plant

damage. (See see. 3.4.8 for a description of the proposed robot function.) A power

conservation concept limits the robot eyele times to light-side orbit. For example, a

35
plant tray can be harvested and processed in one sunlit segment of an orbit. CELSS

generates approximately four trays per day. There are 16 orbits per day, the robot wiU

use one-forth of its time to harvest trays, the remaining time can be used for

monitoring, maintenance, and inspection tasks.

3.4.4 Thermal Control System

The thermal control system uses air flow around plants and over light sources to collect

heat. This heated air passes through a heat exchanger connected to the Space Station

thermal bus. Selected high-heat sources, such as the waste regeneration system and HID

lamps, use liquid cooling loops to achieve greater efficiency. Liquid cooling also

connects to the Space Station thermal bus.

3.4.5 Atmosphere Control System

The atmosphere control system uses the Space Station as a reserve and buffer system for

CELSS. Carbon dioxide is collected from the Space Station ECLSS system and piped to

CELSS. It is released as needed to maintain desired carbon dioxide partial pressure. The

oxygen generated by plants is collected by CELSS environmental control system (ECS)

and piped to Space Station or reserve tanks. Stored oxygen may be used later to supply

the waste regeneration system or dark period plant respiration as well as crew needs.

Nitrogen is used as atmosphere inert gas. It is drawn from Space Station storage tanks to

makeup for leakage. Water vapor is condensed and piped to the nutrient supply system

for makeup water.

The atmospheric contaminant control system uses filters, catalytic afterburners, and

waste regeneration system. A percentage of each air exchange is passed through filters

and afterburners, depending on contaminant level.

3.4.6 Plant Lighting System

The plant lighting system provides plant illumination requirements for normal plant

development and accelerated growth. A full intensity (750 to 1000 _mol/m2/s) plant

lighting can be provided during light-side orbital periods using either fiber optic solar

light collectors or artificial lamps powered by the Space Station electrical power. Space

Station paotovoltaic power sources will charge electrical power storage devices for use

during dark-side orbital periods. This study uses estimates that suggest that approxi36
mately one-tenth intensity maintains plants in a photosynthetic state during dark-side

orbital periods. This is provided by artificial light using Space Station-stored electrical

power.

3.4.7 Waste Regeneration System

The CELSS waste regeneration concept uses the SCWO system. This system was

selected by NASA for its potential increased efficiency obtained by operating at

elevated temperature and pressure. Short duty cycles are used to reduce power

consumption especially during dark-side orbital periods. Waste heat from the SCWO

exothermie reaction is used to preheat wastes thereby reducing power requirements. A

salt separation system is envisioned to recover nutrient salts for reuse. Carbon dioxide

and water vapor given off are collected and stored for later use.

3.4.8 Nutrient Supply System

The nutrient supply system uses eccentric cam-mounted injectors that seat against

openings in tray ends. The injectors have o-rings seats to form a leak-resistant seal

when they are inserted into mated receptacles in each growth tray. Each tray has a

probe that permits the injectors to operate only when fully inserted and sealed. The

spray nozzles are located inside the trays to carry nutrient to plant roots. When the

injectors are retracted, the injector valve closes, stopping nutrient flow. A valve at the

tray opening closes to prevent any incidental nutrient leakage from tray. This concept

does not require any threaded fittings, only accurate alignment of the injector and tray.

This nutrient supply concept was developed to allow a robot to readily perform tray

change-out.

Nutrient maintenance and contaminant control uses a dual-reservoir concept. One

reservoir contains a generic nutrient solution made from salts and water recovered in the

waste regeneration system. A second reservoir is located on each bank of PGUs and

includes monitoring devices and injection systems to keep nutrient pH, conductivity,

nutrient content, and oxygen level within specified parameters. Additional injectors may

be used for pathogen control or chemical stimulation. This concept calls for periodic

nutrient dumping to the waste regeneration system, a precaution against phytotoxie

material buildup in the nutrient solution. Each PGU bank has a separate nutrient supply

system to aid in preventing disease spread.

37
3.5 STUDYGUIDELINES

NASA Ames Research Center provided or approved assumptionsand guidelines for

conducting this study. These guidelines provide a baseline from which to compare and

evaluate various designs. CELSS study guidelines are as follows:

a. Design CELSS module to grow edible biomass to provide the caloric contents for two

men per day.

b. Primary crop wilt be spring wheat (Triticum aestivum - Ultra-dwarfl

c. Secondary crops will be white potatoes (Solanum tuberosum -norland) and soybean

(Glyeine max - Ransom)

d. Aeroponies will be used for wheat and soybean growth. A modified hydroponics

system will be used for potatoes.

e. PGUs wilt be open to the module atmosphere.

f. Cabin atmosphere carbon dioxide range will be controlled at 250 ppm to 2000 ppm

(+/- 20ppm).

g. Cabin humidity range wilt be controlled at 40% to 85% (+/-5%) relative humidity.

h. PGU plant canopy temperatures wilt be individually controlled using airflow

injection.

SCWO system wilt be used for waste regeneration. Technology will exist for

separation of by-products into salts usable in nutrient solution.

i. Module size will be compatible with the Space Shuttle (STS). The module contents

will be assembled on orbit.

k. Module equipment must be repairable and/or replaceable on orbit.

. The CELSS module will be totally automated for plant seeding, growth, harvesting,

and processing for storage.

38
m. No centrifuge will be incorporated in the CELSS module design.

n. Collect CO2 from Space Station and return excess 02 to Space Station.

o. Urine, hygiene and process grey water will be fed to SCWO for use as makeup water.

P. Oxygen supply for humans in CELSS module will be provided by plants or ducted in

from Space Station.

q. A continuous-harvesting approach will be used for PGU design.

r. Plant lighting levels will be adjustable for dark and light cycles.

3.6 CELSS STUDY ASSUMPTIONS

CELSS study assumptions are -

a. Wheat, potatoes, and soybeans will grow and reproduce in a micro-gravity environment without the aid of artificial gravity.

b. Transpired water from higher plants is considered potable with Umited

posttreatment.

e. Higher plants grow to the same general dimensions in micro-gravity as on Earth.

d. Plants will grow with 300 _mol/m2/s illumination intensity.

39
This page intentionally left blank

4O
4.0 PRELIMINARYDESIGN

CELSS preliminary designs are developed from study conceptual designs and are reported

in this section. Preliminary design focused on developing a volume efficient, low-power

CELSS system from NASA selected conceptual design. Plant growth support systems are

selected to provide the best volume and power utilization while keeping costs and

manpower requirements to a minimum. Plant iUumination systems are the preliminary

design variable that will be evaluated during sensitivity analysis. Preliminary design also

included integration tradeoff analysis between candidate systems.

The conceptual design selection process resulted in the accordion tray plant growth

concept selection by NASA as the basis for preliminary design. This PGU concept was

modified to use several natural and/or artificial lighting system combinations. An

accordion tray system using a solar collector augmented with fluorescent for dark-side

orbit illumination was selected as the best compromise CELSS system from the options

evaluated.

The foUowing ground rules and assumptions were used to select systems.

a. Design for enclosure in the Boeing-proposed phase B Space Station common module.

b. Design to function in microgravity<10-3g.

e. Adaptable to function in reduced gravity (10-2g to 0.9g).

d. Design for operation with automated systems, including robots performing routine

activities. CELSS will be manned only for nonroutine maintenance and repair

functions, and to transport food to the Space Station galley.

4.1 CELSS SYSTEMS DEFINITIONS

The systems making up a CELSS module perform the functions necessary to grow a food

crop (wheat etc.) in the Space Station environment. The performance requirements for

each system are described in the following sections.

tJRDCEDhN(I P-AG]_ i_uA_NK NOT FILMED

41
4.1.1 Plant Growth Unit

The PGU provides a place for growing plants and a means to hold them in positionduring

the growth eyele. The method of retaining and holding the plants permits exposure to

lightand nutrients.PGU design must confine nutrientsto root zone.

The PGU design provides a means of starting the plants from seed. Mature plants can be

automatically collected for food processing. PGU design permits sequencing of crop

planting and harvesting in order to have daily food collection.

4.1.2 Plant Lighting System

Sufficient illumination intensity is provided for efficient plant growth by using fiber

optic technology to directly collect and route sunlight. The light is provided in the

wavelengths most usable by the plants (i.e., the visible wavelengths, with emphasis on

red and blue). Sunlight is collected using Sun tracking arrays of Fresnel lenses. These

lenses are specifically constructed to focus each wavelength at a specified point. The

fiber optic fibers are positioned to collect only those frequencies useful to the plants.

Harmful frequencies (infra-red (IR), ultraviolet (UV), etc.) are not collected for

transmission. The collected light energy is transmitted through fiber optic cables formed

from numerous smaller cables fused into a trunk line. This trunk line pipes the light to

distribution buses from which it is directed to PGUs. Artificial light is provided during

the dark-side orbit. Fluorescent lights were used in this design because of their

simplicity, relatively low weight, and reliability.

Wheat, the primary study crop, can thrive under continuous light. A fluctuation between

light and dark periods during each orbit, 16 times per day, may alter normal growth and

development. Illumination intensity is adjusted for dark-side orbit to keep plants

photosynthetically active. Light intensity is limited by available electrical power and by

the resulting temperature control requirements.

4.1.3 Thermal Control

CELSS thermal control must maintain module interior temperature within a relatively

narrow range (12-28°C) for efficient plant growth. Heat loads are primarily contributed

42
by plant lighting system. Waste regeneration system contributes a second high,

concentrated thermal load for a few hours each day. Additional heat is generated by

electrically powered equipment on board.

Forced air circulation and the natural transpiration of moisture from plants are used to

maintain growth temperature range. Cooling sir velocities are kept low to avoid

inhibiting plant growth. These low cooling air velocities dictate that cooled air be used

to remove maximum heat load per cubic foot of cooling sir. A relatively large ECLSS

cooling capability is provided because the design uses ambient sir cooling.

The concentrated, high-temperature thermal load from the waste regeneration reactor is

controUed with a water jacket and heat exchanger.

Heat from CELSS module is routed to the Space Station heat bus for possible use in

Space Station processes. Excess heat is radiated to space by Space Station radiators.

4.1.4 Nutrient Supply

The nutrient supply system keeps plant roots moist and provides the required nutrients.

Nutrient solutions are monitored and adjusted for each plant species grown. A constant

aerated nutrient supply is pumped to the roots. The exhausted nutrient is removed from

the root zone by aspiration.

Aspirated air, with entrained nutrient solution, is passed through a water separator. The

used nutrient solution is automatically monitored for composition and pH. The nutrient

solution elements are replenished, pH and solution concentration adjusted, and then the

solution is recycled to roots.

Particulates and some contaminants in the nutrient solution are filtered out as the

solution is recirculated. When the dissolved contaminants reach upper-limit levels, old

nutrient is dumped to the waste regeneration system and fresh solution is added.

43
4.1.5 Atmosphere Control

The plant atmosphere is controlled for composition, pressure and contaminant

concentration. Carbon dioxide concentration is a variable for different plant growth

conditions. Carbon dioxide levels can be maintained at desired concentrations by

regulating output from waste regeneration and from the Space Station atmosphere. This

may require reserve carbon dioxide tanks to capture SCWO exhaust carbon dioxide.

Oxygen levels build up as the plants produce oxygen and will be controlled by oxygen

scrubbers. Contaminants are removed by filtersand/or catalyticburners.

4.1.6 Waste Regeneration

CELSS operation produces a high volume of organic waste material An SCWO unit is

used to process the plant waste. Other organic Space Station waste material is

processed with the plant waste. Oxidation products are reclaimed for reuse in the

nutrient supply, for replenishingcarbon dioxide and nitrogen in the atmosphere, and for

potable water supply.

Waste material is ground into very fine particles then mixed with water to form a slurry.

The slurry is preheated and sent to the SCWO reactor. Preheated air and oxygen are

injected, which results in waste oxidation. Supercritical steam from this oxidization is

vented to the preheat exchangers and subsequently separated from the entrained carbon

dioxide and nitrogen gasses. The steam is condensed into potable water. Carbon dioxide

and nitrogen, the other major gaseous outputs, are compressed and stored for later use.

Nongaseous oxidation products are passed through a salt separator. This unit salvages

plant nutrients by using pressure and temperature variations to selectively precipitate

desirable compounds. Unusable wastes are sent to storage pending disposal.

4.1.7 Food Processing

Food processing includes harvesting mature plants and separating food from inedible

biomass. Mature plant trays are removed from the growth unit, inserted in the harvest

machine, which clips off stems whUe an air flow pulls and the robot arm pushes the

stems, crop, and roots into the harvester chamber. A cross flow of air causes less dense

particles to deflect while denser crop material continues relatively straight through the

44
chamber. Separate collection containers are used to hold the crop and inedible biomass.

Collected wastes are ground to fine particles and stored until the next waste regeneration cycle. Edible crop material is stored until storage containers are full. The Space

Station crew is alerted to retrieve the food, a crew member enters the CELSS module

and empties the food container.

4.1.8 Robotics

CELSS module operations are fully automated. This automation includes robots unit that

perform all planting, harvesting, waste handling, and some maintenance operations.

Space Station crew members normally only enter the module to perform unusual

maintenance, conduct repairs, or remove food supplies.

One robot handles the planting operations. Its primary functions are to remove trays of

mature plants from the growth unit, insert newly seeded trays to maintain crop growth

sequence, and move mature plant trays to the harvest equipment.

The second robot proeesses plant trays through the harvest equipment. It also handles

the trays through the reseeding operation and replaces empty seed mat cartridges in the

seeder.

4.1.9 Module Structure

With the exception of minor changes, the common module shell is used as the primary

structure; the secondary module structure is CELSS unique. Working area height is

increased to more efficiently use interior volume for plant growth. Secondary support

structure is added for each CELSS systems equipment.

4.2 SYSTEM DESCRIPTION

Each CELSS system (defined above) is described in the following sections.

45
4.2.1 Plant Growth Unit

The PGU design was selected to meet the requirements defined in section 8. This

design comprises a series of plant trays arranged in a tier eight high. Sufficient plant

growth area (for two crew members) is attained by stacking four tiers to a module cross

section and using six cross sections to obtain 40-m 2 growth area (fig. 4.2-1).

Seeded trays

in for growth

Area available

for equipment

Cu rye

conform$'-_

to module

hull

Used nutrient

out

Ratchet Plant growth

mechanism

A-A Light panels

Nutrient feed in

Plants Air space

rotates

out to clear trays A-A

for removal Plant _ Light

m

t X _ _'_]_ _ Newly

1 _ _ _ seeded

ture plant trays tra'

Ma tray

L ¢-- Newly seeded tray

Super critical

water oxidizer

Figure 4.2-1. Plant Growth Unit Configuration

Each tier is supplied with nutrient, (see. 4.2.4) and light, (see. 4.2.2). When the plants

are mature, the trays are removed individually and transported to the harvest equipment.

A fresh tray with a seed mat is inserted in the empty tier and all remaining trays are

moved one space nearer the center mature-tray position (fig. 4.2-1, see. A-A).

4.2.1.1 Growth Unit Arrangement

The PGUs are configured to take advantage of plant growth patterns and keep light

sources (luminaries) close to growing plants. The units are divided into eight increments

to permit a close match with plant height change and harvest cycle (fig. 4.2-2). The

PGUs are arranged (fig. 4.2-1) to maximize growing area per volume in a cylindrical

moclule cross section. Access to all growth units is ensured by a central aisle running the

module length.

46
Twenty-four growth units (tiers) with eight trays each provide adequate plant growth

area to satisfy caloric requirements for two adults. A 20% reserve is included in this

calculation (table 6.5-1, 100% wheat).

(Growth

cycle)

I00%

50 (19.68 in)

(Growth

cycle)

66%

40

/

/

/

/

I0

2

0

4.2.1.2 Plant Trays

Mature pack _

(700 plantslm 2)

Growing days

Figure 4.2-2. Plant Growth Pattern (Wheat)

63

The plant trays have an 8-in 2 cross section. An 8-in width is an efficient size to make

eight increments in each growth unit. An S-in depth should provide ample space for

plant roots and nutrient distribution. The tray length is determined by module crosssection contours. Stacking the trays in tiers of eight in each quadrant of a module cross

section generates tray lengths increasing from 25 to 56 in as plants grow. The accordion

trays are compressed to 25 in immediately after seeding. As seeds germinate and grow,

the trays are moved toward module center. The plant lighting panels are arranged to

accommodate increasing plant height at each succeeding tray position. At the same

47
time, trays expand to conform to module contours and provide more room for root and

stem growth. The aecordion tray construction permits planting seeds at a very high

density. Therefore, mature plants, at maximum tray expansion, ean have a density of

700+ plants per square meter growth area, (fig. 4.2°3).

ow'th slots (Typ. one side)

-='-2.10-'_

Detail A

Tray expanded

See details A & B _-

Tray compressing

winch and cables

Plant

, growth (Ref)

!

l

1.05

Plant density

• 6 rows of plants, 26

• Plants per row = 156

• Plants per tray

Detail B

Tray compressed

Tray expanded

L_

_. Pulley for cable run (Typ)

-_ Plant

growth (Ref)

I

Tray support and supply arms (Ref)

Section A-A

4.9-.1.3 Seeder

Figure 4.2-3. CELSS Tray Concept

The equipment to reseed trays after harvest is not a direct growth unit item, but is

essential to successful growth unit operation. Seeds are shipped from Earth embedded in

a foam tape (seed tape) that is coated with an adhesive on one side. The preloaded seed

48
tape cartridges are placed in the seeder device. As the tray is inserted into the seeder, s

power drive feeds the tape out over the tray. The unseeded tray has the tape applied to

one surface. Seed locations are matched to slots in the tray surfaee, (fig. 4.2-4). A

ribbed roger then presses the tape into place. After the tray is covered with tape, a

solenoid-operated knife cuts the tape. If no other trays require seeding, the robot

removes and stores the tape cartridge (fig. 4.2-5).

Figure 4.2-4. Tape Application to Tray

The seed tape must be kept cool and dry untila seed tray isplaced in the seeder unit.

Preseeded tape is kept in closed cartridges for safe storage and easy handling.

Cartridges hold sufficienttape to seed 18 trays. Eighteen cartridges hold enough tape

for 90 days for two adults.

Power feed for the tape consists of an electrically driven roller that removes the tape

from the cartridge. The roller accesses the tape through a slot in the forward cartridge

feed lip. Seed registration with tray slots is maintained by locating sprockets and

perforation in tape border.

Tape-to-tray adhesion is accomplished by a ribbed roller that presses tape onto the tray

and down into the accordion depressions. A pneumatic piston operates the roger and

regulates pressure. Roller registration on the tray is maintained by alignment of roller

ribs in tray accordion depressions. Tape is cut to length by a solenoid-operated knife

acting against a metal platen attached to the tape cartridge.

49
Pneumatic

toggle

mech. Pneumatic pressure roller

Tape knife

! F Power tape feed

_ ,_-_- Seed tape cartridge

Tray _J_

rails

(Both sides)

Figure 4.2-5. CELSS Seeder

After a tray is seeded it is removed from the seeder. The taping mechanism is pivoted

out of the way to facilitate tray removal A pneumatic piston provides the rotating

force.

4.2.1.4 Parts Listing

Tables 4.2-1 through 4.2-2 list major plant growth tray and seeder unit components.

4.2.2 Lighting System

The plant lighting system selection considered four options. The first was a solar

collector (only) based system. The second was a totally artifici_-based system. The

5O
Table 4.2-1. CELSS Plant Growth Tray Assembly

Equipment

Accordian

tray box

Seed mats

Telescoping

spray tube

Tray end

(nutrient

input)

Tray end

(blind)

Quantity

required

216

+

spares

192

X

cycles

216

÷

spares

216

+

mares

216

spares

SLoe

8" x 8'"

x 56"

(expanded)

8" x 54"

1" x 54"

(extended)

8 we X 8 we

8 e# X 8 #w

Product

in

Nutrient

solution.

and air

Seeds

Nutrient

solution -

and air

Product

out

Crop

Utility and

power

requirements

Support

structure

nutrient

supply system

Support (tray)

nutrient

supply system

Attachment

to accordian

tray

I Attachment

to accordian

tray

i

Comments

Needs method for compression, attach points for

support and transport,

nutrient supply port

Contains nutrient and air

inlet port (into telescoping tube)

Attaches to blind end of

telescoping tube

Table 4.2-2. Seeder

Equipment

Tape cartridge

Tape feeder

Tape knife

Pressure

roller

Subframe

toggler

Subframe

Frame

Quantity

required

20/90 days

Size

12" dia x 6"

4" dia x 6"

6" x 4" x 6"

6" x 6"

xlO"

4" dia x 10"

75" x 10"

x 24"

Function

Hold and dispense seed

tape

Feed tape out

to roller

Cut tape to

length

Presses tape

onto growth

tray

Moves seeding

system into

and away from

growth tray

Carries seeding

equipment,

rotates in joint

Registers tray

place, provides

pivot plus

reaction base

for seeder

Utility and

power

requirements

None

28 VDC,

100W

28 VDC,

200W

Pneumaticstation air at

100 psi electrical valve

regulator

Pneumaticstation air at

100 psi electrical valve

regulator

Comments

Robot changes out cartridges

as required

Intermittent pulse operation.

solenoid powered shear

Pneumatic actuator with

"rubber" roller

Pneumatic actuator

1" x 1" angle, some nonmetallic material such as

kevlar composite

1" x 1" angle, some nonmetallic material such as

kevlar composite

5]
third and fourth were two variations on hybrid systems using solar illumination on lightside orbit and artificial lighting using one-tenth illumination level on dark-side orbit to

conserve power.

A hybrid system using solar collectors and fluorescent lamps is identified as best

compromise illuminationsystem during preliminary design tradeoff analysis. This solar

plus fluorescent system uses reduced plant illumination intensity during dark-side

operations to reduce power consumption. A discussionof each system follows.

4.2.2.1 All-Solar Lighting

The collected sunlight is conducted through fiber optic cables to be distributed from

luminaries over the tiers of plant trays. A Fresnel lens system is used as the solar light

concentrator. The system-unique characteristics permit selective light frequency collection (filter IR and UV) by selective positioning of the fiber optic cables. Fiber optic light

cables from each lens are bundled together into trunk lines then run through the module

huH. These bundles are then broken out into individual cables. Cables are routed to

PGUs where they are connected to terminal illuminators. Varying cable count to each

illuminator varies the light intensity. Internal illuminator controls permit reducing light

intensity without moving cables.

Tradeoff analyses determined that a solar collector lighting system saves signif'icant

electrical power. Because solar light provides the plant illumination, the station need

only expend the power to keep the collector Sun oriented, an estimated 373W. Working

against the solar-only collector system are two factors. First, solar lighting will be on

for approximately 60 rain and off for approximately 30 rain each orbit. Frequent, short

day- and night-cycle exposure may have an adverse effect on plant growth. Second, is

the anticipated reduced yield when compared to continuous full lighting. This causes a

volume penalty by requiring additional PGUs. These effects, added to the unknown

effects of microgravity on plants, result in caution in selecting solar collector-only

lighting as the CELSS lighting system.

4.2.2.2 All-Artificial Lighting

Providing effective plant growth illumination levels and frequencies with artificial

lighting is possible using available electric lamps. Fluorescent tubes, xenon lights, and

high intensity discharge (high-pressure sodium) lamps were compared. The power

required for the desired illumination levels for a two-member module are52
Fluorescent 79.2 kW

Xenon 306.0 kW

HID (high-pressure sodium) 77.4 kW

These values probably represent an unrealistic allocation from the 1999 proposed Space

Station power budget (-210 kW). This consideration resulted in dropping artificial-only

lighting as primary illumination system when compared with other available systems (fig.

4.2-1).

4.2.2.3 Hybrid Lighting

Combining solar lighting during light-side orbit with artificial lighting during dark-side

orbit provides continuous light and reduces power demand. This hybrid system provides

any length of day required by plants up to a continuous 24 hr of illumination. Reduced

illumination intensities during dark-side operations are necessary to conserve power.

Artificial lights equivalent to solar-light levels (750 _mol/m2/s) requires over 75 kW.

Reducing artificial illumination to 750 foot-candles (75 kwnole/m2/s) may keep plants in a

photosynthetic state while reducing power consumption as followsFluorescent

Xenon

HID (high-pressure sodium)

Comparing these lamp sources requires considering additional lamp characteristics. For

example, warm-up time for lamps requires energy expenditure without appreciable light

generation. Short warm-up times are preferred in lamp design. Xenon and HID lamps

require relatively long (several minutes) warm-up time and generate intense, localized

heat loads. Fluorescent tubes require no appreciable warm-up time, do not generate

intense, localized heat. Ballast losses are comparable for each lamp at a nominal 10%.

HID lamps are three to four times more efficient than fluorescent in terms of lumens

produced per watt. HID intense heat generation makes them unsuitable for direct plant

iUumination at the required very close plant-to-lamp spacing. An alternative approach

using fiber optic light pipes solves the heat problem; however, the efficiency losses

encountered in focusing and transmitting HID light reduce overall efficiency by 3096 to

6096. Compared to fluorescent lights in fixtures directly over the plants, the power

53
requirements are nearly identical for each lumen at plant canopy. Volume, cost, and

mass values also favor a solar-plus-fluorescent system.

A hybrid plant lighting system using solar light when available and supplementing with

fluorescent light during dark-side orbit is selected as the study baseline plant growth

lighting system (fig. 4.2-6).

4.2.2.4 Solar Light Collection

Solar light is collected by a number of Fresnel lenses focusing solar rays onto the ends of

glass fibers (fig. 4.2-7). Solar collector lens area totals about 62.9 m 2 to provide 1000

IJmol/m2/s to 40 m 2 of plant growth area in the module. A tracking mechanism

maintains exact alignment of the solar ray coUector with the Sun. This pointing system

moves very slowly as the Space Station precesses during its orbit. Slow speed combined

with microgravity allows a small motor to power the pointing system. Net system power

consumption is about 373W.

A 2-mm glass fiber exits from each lens then is combined into bundles and routed to

PGUs. Study design assumed a continuous cable from lens to illuminator. In practice,

breaks in each cable are necessary for handling, maintenance, and system upgrading.

These breaks can cause from 2% to 3596 light loss depending on technique used. Rotating

joints are avoided in study design by using slack cable loops. This approach avoided the

20% to 3096 losses common to fiber optic rotating joints. No joints are used at hull

penetration to avoid light loss. Current hull penetration technology is adequate to safely

permit penetration by unbroken bundles.

4.2.2.5 Fiber Optic Cables

The fiber optic light transmitting cables are made up of bundles of individual glass

fibers. Each cable is 2 mm in diameter and collects and transmits light from one

Fresnel collector lens. Current fiber optic technology uses germanium-doped fibers to

enhance transmission quality. This technology is based on high-frequency light (UV) used

for fiber optic communication systems. Several glass types are used in fiber construction. Most glass types are tuned to a frequency range. Glass additives are used to filter

undesirable frequencies. These characteristics will aid in removing UV and IR light in

transmission to plants. Improved and frequency-tuned doping compounds and glasses wiU

reduce light loss at bends and junctions.

54
0

"0

°_

.Q ,..

S_

\

0

_°-

.__

>. -=

(1)

_E

v)(_l

0

..j

55
Fresnel lens

assemblies

Top view

Fiber optic cable

(focal point)

oroid

shield frame

Visible

light (red) _ i

- I

Visible

I

light (blue) _ i

\\N',

; 1

Expansion I _

gasket _ _ila

F resnel I_i.=.._ 11I

Lens support

Fiber

o

0

o

o

Ultraviolet

0

o..=------- Infrared o

Ionizing radiation

ii

i

Micrometeoroid

' __rame

' ! XX Lens

I '-- focal

I

: point

!

Figure 4.2-7. Fiber Optic Solar Ray Collector (Side View)

56
4.2.2.6 Solar Light Distribution

Solar light distribution uses an inverted-tree structure to direct desired light intensity to

each PGU. Light is transmitted from fiber optic cables to primary beam splitters at

each tray location. An aperture control mechanism or adjustable shutter is located

between cable end and beam splitter. Primary beam splitters transmit light to eight

secondary beam splitters forming luminaries to emit light to each tray. Each luminary

beam splitter (fig. 4.2-8) has a series of steps on the surface away from the plants.

These step surfaces are silvered to reflect light onto the plants. Reflecting steps are

staggered to ensure an even distribution of light. A reflector over each luminary helps

reduce light loss and also serves as a reflector for the artificial lighting system.

//'-- FiberAperture opic cable control

||

(Reflector omitted for clarity)

Primary

m splitter

;/ /-- Light path

_ =:J I

I *ell.f '

I I II;

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

,(--H ..... f ..........

/,,_/f '_ Plant

l

Secondary beam splitter (2 shown)

-;_, ............. _,

gg ,

II il

I, _ A-A

Reflecting step

Plant growth tray

|1

/ Reflecto_

A-A

detail

Cable-splitter interface

Figure 4.2-8. Fiber Optic Luminaire

4.2.2.7 Artificial Lights

Light from fluorescent lamps is provided, when necessary,

operations. [Uumination intensity equivalent to coUected solar

by high electrical power requirements (75 kW) for artificial light.

during dark-side

light is precluded

A light intensity

57
of 750 ]Jmol/m2/s, is used to maintain plants in a photosynthetic state. Providing

this intensity with fluorescent tubes requires about 11-1/2 kW, including ballast

losses.

The fluorescent tubes are installed in the same luminaries with fiber optic beam

splitters (fig. 4.2-9). One reflector serves both types of light emitters. Heat loads

generated at the light-emitting surface are comparable for both types. Approximately 12W/ft 2 of tray aces (41 Btu) from the beam splitters and 17W/ft 2 of tray

area (58 Btu) from fluorescent tubes. Common cooling provisions will handle

luminary heat loads for all lighting conditions.

Fluorescent

tubes

through

fiber olatic

emi_ers

Plant

trays

Light shines

towards plants

Figure 4.2-9. Combined Solar and Fluorescent

The fluorescent lamp frequency spectrum is adequate for plant growth. Modifications in phosphor coatings can increase red frequency output, which may enhance

plant growth. The fluorescent lamp mercury content is a major health hazard.

Specially design sealed lamps and/or fixtures may be required to prevent mercury

escape.

58
4.2.2.8 Lighting Efficiency

Lighting efficiency can be defined in terms of lumens per square foot of plant area

per watt of electrical power.

Efficiency: lumens on plants/W

Fluoreseent tubes 41.3

Collected solar rays 9700

Solar light eolleetion effieieney ean also be defined in terms of light transmission per

distribution effieiency.

Efficiency: lumens on plant/lumens collected

Collected solar rays 0.456

The solar collectors pick up 8.0 million lumens. Fiber optic cables transmit 6096 or 4.8

million lumens to the luminaries. The luminaries emit about 7696 or 3.64 million lumens

to the plants, or 7500 lumens per square foot. The values for lumens collected and

transmitted are based on a continuous cable between the solar collectors and the

luminary connections. Lights transmitted through fiber optic cables can be reduced 296

to 396 through an optimum connection and up to 2096 to 3096 for current technology

rotating joint connections.

4.2.2.9 Parts Listing

Table 4.2-3 lists major components for solar ray lighting and fluorescent tube supplementary lighting.

4.2.3 Thermal Control

Heat is added to the CELSS module by solar lighting and by artificial lighting.

Additional heat is added by the SCWO waste regeneration unit, (sec. 4.2.6.) For each

watt of electrical power used, approximately 3.4 Btu of heat are generated.

Cool air eireulation is the principal method seleeted for removing heat from the PGUs.

Air is passed through heat exchangers, excess moisture is removed, and the air is

recirculated. Air exchange rate peaks at about once every 2 rain for maximum heat load.

59
Table 4.2-3. CELSS Growth Unit Lighting--Conducted Sunlight

Equipment

Solar

col lector

Solar

collector

lens

F ibers

(quartz)

Fiber optic

cable

Beam splitter

(one at each

tray)

Beam splitter

(luminaire)

Light sensors

Reflectors

Light

aperture

control

Servo motor

or solenoids

Microprocessor

"controller"

Tracking

mechanism

Florescent

lamps

Quantity

required

2712

2712

24

192

1152

192

192

192

192

192

Size

See lens

6.77" dia

(35.997 in2)

2mm dia

x lOOft

26ram x

100 ft

(.52 Ib/ft)

10" long x

2"x 2"

(stepped

down -

use .6

factor)

Tray length

X 2" x .25"

(stepped

down -

use .6

factor)

Tray

length x

8" x .375

2 #' X 2 'e

X 3"

(estimate)

Length to

match tray

length

Product

in

Light

Heat

Light

Heat

Light

Light

Ught

Light

Light

Light

Control

signal

Electrical

power

Sensor

signals

Sensor

signals

Electric

power

Product

out

Sensor

signal

Shutter

motion

Motion

(to shutter)

Control

signals

Control

motion

Lightand

heat

Utility and

power

requirements

Support

Support and

cooling

Support

Support

115 VAC

or 28 VDC

373 W

Mounting,

cooling,

21.74 watts

per sq ft

(stand by)

Comments

Composed of 2712 lenses

113/PGU = 2712 lenses

(677.94 ft 2 lens)

Composed of 113 fibers

each = 2712 fibers 1 cable/

tier

Glass transmits light from

tray cable to tray beam

splitters

Glass 4/tray (6/tray) as

required for even light

distribution to plant

canopy

To measure light level,

detect light failure or

malfunction

Reflect back and conserve

light lost from tray beam

splitters

Shutter up stream surface

(toward light source) is a

mirror

Operates aperture control

shutter

Varies light intensity by

controlling aperture

shutter

Keeps collector lenses

directed at sun

(1) or 2 lamps per tray

probably special lamps

6O
Equipment

Table 4.2-3. CELSS Growth Unit Lighting- Conducted Sunlight (Continued)

Utility and

Quantity Product Product power

required Size in out requirements Comments

Ballasts

Reflectors

Light

Sensors

Light

intensity

control

Microprocessor

"controller"

192

192

192

192

8" x tray

length x

.375

Electric

power

Light

Light

Control

signal

Sensor

signals

Electric

power plus

heat

Sensor

s_gnal

Light

intensity

adjustment

Control

signals

Electric

power = to

10% of lamp

power

Structural

supports

Support

111amp

(1) or 2 lamps per tray

Use same reflector used

with solar light

Varies light intensity

Heat exchangers are cooled by a water circulation system, heat is sent to a Space

Szation thermal bus, and unneeded heat is radiated to space.

4.2.3.1 Plant Growth Unit Cooling

Heat from light-emitting surfaces and from impinging light energy combine to form the

major thermal load. FuLl illumination with collected solar rays creates approximately

82,000 Btu/h. Maintaining plant temperatures between ?0oF and 900F (20oc and 30oc)

requires approximately 2000 ft3/min of air circulation. Air flow is directed past and

through plant growth trays to carry heat toward adjacent luminaries. The air circulated

past and through luminaries is allowed to gain more heat than air around adjacent plants.

Air passing over light-emitting surfaces is allowed to reach temperatures as high as

120°F. Cooling effects of water transpired from the plants helps minimize air

circulation requirements. Energy required for air circulation system adds heat that must

be removed.

4.2.3.2 Waste Regeneration Cooling

When operating, the waste regeneration system operates at S4OF to 1240oF (450oc to

670°C). This concentrated heat load is generated by the SCWO reactor, a small, high61
pressure device. Some of this heat is used to preheat entering waste material. The

remaining heat is removed by circulating water through a jacket and then through a heat

exchanger. Heat that is not used in other processes is radiated to space.

4.2.3.3 Cooling Air Circulation

ALl air circulation must be forced-air generated because convection currents do not

occur in microgravity. Air to cool PGUs is forced, by a fan, through four main ducts

along the PGUs (fig. 4.2-10). These ducts feed distribution passages that direct air past

plant trays and luminaries. Warm air is drawn through heat exchangers as the fan forces

air into the distribution ducts. Chilled water circulating through the heat exchangers

removes and carries heat to Space Station thermal buses. Excess heat is then radiated to

space.

T Sensible HX

Cpmpower- =,3'5002 hp Q[L_7 I = 87,000 Btu/Hr

Chamber air _ "7 _ _ Chamber

(lOOOF) Fa_n _ air

(70 °)

hp = H20 ,. _

Cooling water

; Chamber air

(60°F)

Cooling water ,

supply (40°F)

T = 70°F I_

M = 2,900 Ib/H21

Humidity condensate

to potable water system

Super-critical

water oxidation

/V_i unit HX

T = 60°F

M = 2501 [JHr

Q = 54,000 Btu/Hr T = 120°F

M = 675 lb/Hr

Capacity = 1000 Ibs

= 16 atmosphere

= 120 gallons

_,_e Accumulat°r/

servoir

Thermal

bus HX

_-_#/_ 1_ _Extemai HX and body-mounted radiatorl_

4k To/from • Thermal bus (35°F)

Figure 4.2.10 Cooling Air Flow Diagram

4.2.3.4 Parts Listing

1.0 hp

Pump motor

Tables 4.2-4 lists major CELSS thermal control system components.

62
Equipment

Sensible

heat

exchanger

Sensible

heat

exchanger

fan and motor

Latent heat

exchanger

SCWO

heat

exchanger

Accumulator

Pump and

motor

Thermal bus

exchanger

External heat

exchanger and

body mounte(_

radiator

Quantity

required

1

Table 4.2-4. CELSS Therma/-Cooling

Size

1.7 ft 3

6" dia x

22"

524 in3

Product

in

Warm air

Cool H20

Air --

Warm

moist air

cool H20

Cold

Water_

Water

Product

out

Coo! air

Warm H20

Cool dry

air water

warm H20

Hot H20

(120°F)

Utility and

power

requirements

Air flow and

cooling water

Either 28 VDC

115 VAC

1600 W

Circulating

air and water

Either 28 VDC

115 VAC

800 W

Comments

Cooling capacity required:

87,000 Btu/hr

16" dia fan to move 3500

CFM

Removes up to 5000

Btu/mv from moist air

• Volume ==net

622 in3 -- 98 in3

675 Ib H20/hr

Capacity 120 gallons

(1000 Ib)

Pumps cooling water

Same as priced for common module in phase B proposal

Same as priced for common module in phase 8 proposal

4.2.4 Nutrient Supply

The CELSS nutrient supply system provides roots a constant nutrient solution bath. Two

major subsystems compose nutrient supply system. The first is s nutrient reservoir

where the nutrient salts are combined to ereate fresh base solution (i.e., Hoagland's).

This system is eentralized_ feeding aZl PGU nutrient regeneration subsystems. The

second is a series of PGU nutrient regeneration subsystems, one for each four PGUs.

These regenerat ion units constantly adjust nutrient solution to maintain opt i mu m solutions for

plants.

Aeroponic systems are used to supply nutrient solution to roots (fig. 4.2-11). A spray of

nutrient s6lution is injected into each plant growth tray through orifices in an extendable

spray tube that runs the length of each tray. Aspiration removes exhausted nutrient

solution from root zone.

The aspirated nutrient solution is separated from the air, analyzed for correct composition, renewed with necessary nutrient salts, and returned to the PGU supply tank.

63
Injectors

t

A

I

Mist sprayers

I

Nutrient Nutrient

in out

Vacuum

pickup

Figure 4.2-11. Nutrient Mist Sprayers

Quantity is measured and replenishment solution or water added as required (fig. 4.2-12).

Particulate contamination is filtered out as nutrient solution is returned to PGU supply

tanks. When dissolved contamination reaches limit levels, solution is dumped to the

waste regeneration system and fresh solution is added from the main nutrient supply

reservoir.

Sterile

/ s,,,.,"\ \

from waste _

I _managemeny __/Nutrient _ /

(_ composition X

PGU

Non-recoverable

Chemical ,=/ waste

analysis "_regeneratio? unit _/

I

Renewable

nutrient

solution

I

Figure 4.2-12. Nutrient Flow Diagram

64
4.2.4.1 Nutrients

Nutrient solutionsare specificallyformulated to promote optimum growth for each plant

species. When crops are changed, nutrient solution compositions are adjusted. As

nutrient solutions are recovered from PGUs, the compositions are analyzed. When

analysis indicates low nutrient levels in solutions,make-up constituents are added as

required. Ph is constantly adjusted and buffers added. Solution concentration is

monitored through conductivity measurements that trigger.water injectionsto-make up

for water lost to transpiration. Fungicides, bactericides, and other pest-control

materials can be added to nutrient solutions to control specific problems. These

photogenic organisms are identifiedby central microbial analyzer that receives periodic

nutrient samples from each nutrient regeneration unit. When analysis indicates a

maximum allowable buildup of contaminants, solutionsare routed to waste regeneration

system. Replacement solutionsare added from the main nutrient supply reservoir.

4.2.4.2 Nutrient Circulation

The nutrient solution is supplied to all plant growth trays. An independent nutrient

regeneration system supports every four PGUs to minimize crop failurein the event of a

nutrient system failure. Nutrient solution ispumped to each tray at the rate of 1⁄21/rain

for each square meter of plant growth area. Air is mixed with nutrient solution to

ensure an adequate oxygen supply to roots. Air, with entrained nutrient solution, is

removed by aspiration. Constant supply and removal of nutrient solution keeps root

masses moist, aerated, and supplied with fresh nutrients.

Nutrient supply to each tray is pumped through injectors on swinging arms (fig. 4.2-13).

This design permits direct nutrient injection into a telescoping spray tube inside the tray.

The nutrient supply feed lines are are rotated aside when trays are removed for harvest,

newly seeded trays are planted, and trays are shifted in position as crops mature.

Air from plant trays is passed through a water separator with recovered nutrient

solution. The nutrient solution is returned to the nutrient supply system and the air is

vented to module atmosphere.

Each PGU nutrient regeneration subsystem (fig.4.2-14) isable to operate independently.

Independent operation islimited by contaminant buildup or need to supply fresh makeup

65
-- Nutrient feed tube

Rotating

joint or

flex joint

Shuttle

mechanism

G rowth

trays

As trays are moved

periodically, nutrient

injectors shuttle clear,

then return after trays

are. repositioned.

loadedSpringpin\_ flapper Spring actuated valve - 7

/

" Pin depresser _

Injector Detail

Figure 4.2-13.

canister

Phytotoxin

sensor

and valve

To waste

management

system

Figure 4.2 14.

Nutrient Injection Detail

F Nutrient reservoir

To PGU nutrient

,,_ _ injectors

,_" :_k:: GU vacuum

Air return to ambient

separator

Nutrient Regeneration Subsystem

66
nutrient solution from the main supply reservoir. Isolation valves prevent major nutrient

loss or contamination if problems develop anywhere in the nutrient supply system

network. Cross-flow plumbing and control valves wiU allow adjacent PGUs to share

nutrient supply if one supply subsystem fails. This redundancy wiU prevent crop loss.

4.2.4.3 Nutrient Contamination Control

Particles of root mass and any other particulate contaminants are filtered out of

recovered nutrient solution before the solution returns to a supply tank. Dissolved

contaminants are monitored. When maximum aeceptable limits are reached, nutrient

solution is dumped to the SCWO waste regeneration system and replaced with fresh

solution from the main supply tank. Discarded solution is proeessed to recover nutrient

salts for use in mixing fresh supply solutions.

4.2.4.4 Parts ListlnE

Table 4.2-5 lists major CELSS plant growth nutrient supply components.

4.2.5 Atmosphere Control

The CELSS module atmosphere is controlled for composition, pressure, and contaminant

concentration. Atmosphere control flow is depicted in figure 4.2-15. Plant growth

produces oxygen and uses carbon dioxide. Surplus oxygen is concentrated and stored.

This oxygen can be directly fed to crew or waste regeneration system. Carbon dioxide is

drawn from Space Station carbon dioxide scrubbing system or collected and stored from

waste regeneration system gases. Contaminants enter the module atmosphere from

plants, by out-gassing of plastics used in construction, by operation of powered

equipment, by nutrient solution seepage, and by human entry into the module. Contaminants and concentrations are monitored and excessive levels are reduced by filtering and

catalytic oxidation.

4.2.5.1 Composition and Pressure

The CELSS module nominal atmosphere is a standard pressure atmosphere with sea-level

gas ratios. Some adjustment of carbon dioxide levels are made to optimize plant growth.

Carbon dioxide levels are maintained at a nominal 750 ppm but may range from 250 to

2500 ppm. Nitrogen levels are kept near normal ratio. Stored gas reserves are used to

67
Equipment

Main

nutrient

reservoir

(bladder

tank)

Tier unit

reservior

(bladder

tank)

Pump main

tank

Pumps tier

tanks

Quantity

sensor

A ir/water

separator

Filter

Probes

PH

O2

Conductivity

ION (9)

Injectors

Monitor

probes

PH

O2

ION (3)

Nutrient

supply arm

Table 4. 2-5.

Quantity

required Size

1 3.2ft 3

12 .3ft 3

(24) (8.03" x

8.03" x

8.03")

1 3 - 6 gal/

rain

10x12x16

1920 in3

12 .3 - .4 gal/

(24) rain

4x6x8

192 in3

24

(48)

12 8'" dia x 7"

(24) 351.9 in 3

12 6" dia x 2"

(24) 56.5 in3

.25" x 4"

24

24

24

216

192 .5" x .6"

25" x 4"

24

24

72

192 2.5" x 3.0"

x 7"

53 in3

CELSS Nutrien_ Supl_/ System

Utility and

Product Product

in out

Nutrient Support

stock --- ----=,- structure

solution

Nutrient- _ Support

solution structure

Nutrientsolution

Nutrient _

solution

Air and Air fluid

nutrient nutrient

solution solution

Nutrient Nutrient

_lution solution

particulate solid waste

material

Replenishment --------msolutions

Nutrient

and air

power

requirements

Eider 28 VDC

115 VAC

2OO W

Either 28 VDC

115 VAC

40 W

Either 28 VDC

115 VAC

40 W

Comments

Volume a_proximately 4

times system flow rate per

minute

12 = 1 per 2 tiers

(24) = 1 per tier

Replenish tier unit tank

as required

Controls replacement of lost

quantity in tier tank

Returns fluid nutrient to

system

Strain out particulate

matter, root particles, etc.

Analyze nutrient solution

Maintain proper nutrient

concentration

Check proper nutrient

concentration

1 per growth tray

68
Table 4.2-5. CELSS Plant Growth Nutrient Supply

Equipment

Solenoid

actuators

(arm)

Flow

regulator

Quantity

required

Solenoid

fill valve

192

192

Size

2" x 2"

x 3 °"

12 in3

5" high x

4" wide x

2"

40 idne_

Product

in

Nutrient

solution

Check 192 2" high x Nutrient _ ----=--

valve 4'" wide x solution

6"48 dn_P

Injector 192 .5'" x 6'"

By pass 24 4" x 4" Nutrient -- ---.-

valve x 3" solution

48 in3

24 5" x 4"

x 2 H

40 in3

Nutrient

solution

Product

out

Utility and

power

requirements

28 VDC

20O W

Either 28 VDC

115 VAC

40 W

28 VDC

200W

Comments

Intermittent operation

Control nutrient flow rate

to each tray

To each tray

Inject nutrient into tray

To tray or dump to SCWO

Intermittent works with

quantity sensors to keep

tier tanks full

maintain module pressure and ensure a constant source ot constituent gases. Nitrogen

and carbon dioxide are by-products from the waste regeneration system that aid in

maintaining the atmosphere. Additions] carbon dioxide may be gained from Space

Station atmosphere control.

Nitrogen

and inert

gases

(SCWO)

Carbon

dioxide

(SCWO)

water from

waste management

water

Space

Station

potable

water

Waste

system

dehumidifier _rough

plants

Collect

air and

contaminant

sensor

Air to

catalytic

oxidizer

F/gum 4.2-15. Air Circulation Flow Diagram

69
Oxygen produeed by plant growth isused in waste regeneration (see.4.2.6)and for Space

Station crew oxygen supplies. An oxygen scrubber is used to remove surplus oxygen

produeed by the plants. This oxygen isstored and used in the waste regeneration SCWO

reaetor or added to Spaee Station supply.

4.2.5.2 Contaminant Control

Contaminants enter CELSS atmosphere from most equipment, materials, and processes

in the module. Growing plants emit contaminants as well as producing oxygen. Outgassing of materials and operation of powered mechanisms may generate a variety of

gaseous and vapor contaminants. Seepage and subsequent evaporation of nutrient

solution adds corrosive salts and some particulate material.

CELSS air circulation is used to transport contaminants to removal equipment. Passing

air through filters removes particulate matter and some contaminant gasses. Bleeding

off air for the catalytic combustion system destroys or converts contaminant gssses into

less noxious substances. Periodic oxidation of remaining contaminants through the waste

regeneration system removes remaining CELSS atmospheric contaminants (fig. 4.2-16).

4.2.5.3 Parts Listing

Tables 4.2-6 lists major CELSS atmosphere control system components.

4.2.6 Waste Regeneration

All solid and liquid wastes produced by the CELSS operation along with some or all the

waste from two crew members are processed through the SCWO waste regeneration unit.

This process uses the unusual properties of steam under high pressure and temperature to

oxidize all organic products to salts, water, carbon dioxide, and nitrogen. Oxidation

products (mainly salts) are reclaimed for replenishing plant nutrient materials and Space

Station stores.

In operation, solid wastes are finely ground and mixed with liquid wastes and waste

water. The resulting slurry is processed through the SCWO unit reactor. Salts are

salvaged to replace nutrients, steam is condensed for potable water, and gases are stored

for atmosphere control. Unusable solid waste residue is collected and stored for

eventual disposal (fig. 4.2-17).

7O
16.9

Urine

biormm

Wash

feo_

Air

25.07

SCWO

11.43 0.71

BOSCH.

CO2 CO 2 02

_nerator removt| r_u_mn

H20

14.13 14.6 6.39

Solids [

t

)2--_ CELSS module

I atent

264

H20

H20

(?) + 264

:::> Run through trac_ contmmirmnt control loop N2 Pmck

Figure 4.2-16. Atmosphere Contaminant Contro/

0

6.39

5.S

O? to habitat ..-..¢>

module

Hygiene to habitat

module and potable

4.2.6.1 Biomass and Nutrient Waste

Plant waste, totalling approximately 7 lb/day of nonedible plant material, is ground verdi

fine, mixed with waste nutrient solution or other liquid waste and water (as required) to

form a slurry. Eleetrie power is used to heat the slurry; the slurry is then pumped to the

SCWO reaetor (fig. 4.2-18 and 4.2-19). Preheated air and oxygen are added under high

pressure eausing the waste material to oxidize. Supereritieal water from the oxidation

proeess is routed to heat exehangers to reduee preheat eleetrie power. Water and

entrained carbon dioxide and nitrogen gases are subsequently separated. The water is

added to potable water stores and gases are stored for atmosphere eontrol (see. 4.2.5.1).

71
Equipment

N2

storage

tank

J

Pump

Electric

solenoid

vaJves

SCWO

CO 2

removal

BOSCH

CO 2

reduction

O2

storage

tank

Note:

Table 4.2-6. CELSS Atmosphere Control

Quantity

required

6

Size

10" dia

30" long3 (2356 in )

7" dia

.10" Ion9

(385 in a)

5" high

4" wide

2" deep

(40 in a)

10" x 12"

x 14"

/,1680 in 3)

12"'x 10'"

x 10"

( 1200 in 3)

8" dia

10" long

'503 in 3)

12" dia

36" long

(4072 in3)

Product Product

in out

ii

N 2

N2

0 2 _-

• See SCWO or waste

SCWO CO 2

combustion N 2

gas Iso2

CO 2 C

H2 CO 2

H20

Module 0 2 and

atmosphere air

0 2 _ ---=,-

Utility and

power

requ ire me nts

28 VDC

115 VAC

150 W

28 VDC

115 VAC

50 W

Comments

t 1

Store for addition to CELSS

atmosphere

Pumps N 2 and 0 2 to

storage tanks

Sends CO 2 to module

atmosphere or storage

Store 0 2 in tank

Store 0 2 for SCWO or

Space Station use

Basic humidity control is part of temperature control -- circulation of air during non SCWO

operation is part of temperature control air movement

72
ate water /_,

\,cE_/_ /_--°/

/lw-.\ Water \ \\ /s-V Conde.= ,o k_J,==\ Space

\ (s.,= /_ \ *==r / -\ porte/

\Stati°n) / X _ /_ m_ k \ water ,

/ c_ \ \ \ / / .,,.=-°\/s_=,_:o\_/ .,. \

_, plant mar= _ _ _11 / _ and inert 1( pressure ) _ circulition_

/rO2andair_ _ °x_i_zrer __// =rbon _/ Air

from _ " _ _ dioxide X circulatiOn }

_.o,_. /

Figure 4.2-17. Waste Management System Flow Diagram

Air compressor

Reactor

Valves

Accumulators

Sludge pump

Heat exchangers

Tilt rack

M Shieidin¢j

Figure 4.2-18. Super Critical Water Oxidizer

"73
74
Solid oxidation produets are proeessed in the inorganie salt separator. Nutrient salt

materials are reeyeled in makeup nutrient solution. Unusable solid waste residue is

stored for later disposal.

4.2.6.2 Space Station Waste

Solid and liquid wastes from two Space Station crew members, approximately 10 ib/day,

are moved to the CELSS module and processed through the SCWO unit. They are treated

in the same manner plant wastes are processed. Solids are ground and mixed with liquid

to make a slurry, oxidized, and the products of oxidation reclaimed for recycling. These

wastes may include human fecal wastes and Space Station process wastes.

4.2.6.3 Other Waste

Other waste material includes atmosphere contaminants and contaminant control filter

material. Atmosphere control filters are ground up with other oxidizable waste (e.g.,

garbage, clothing) noncombustible waste or waste that would create toxic hazards when

oxidized are separated from routine waste regeneration. Not used in the waste

regeneration system are broken or disearded equipment, such as metal parts and

burned-out fluorescent tubes. This material is added to the nonreusable residue from the

oxidation process and disposed of in accordance with Space Station procedure.

4.2.6.4 Parts Listing

Table 4.2-7 lists major CELSS waste regeneration system components.

4.2.7 Food

Food proeessing includes harvesting mature plants, separating food from inedible waste,

and storing collected food (fig. 4.2-20). Food processing starts when a plant growth tray

is removed from PGUs.

4.2.7.1 Food Harvest

The trays with mature plants are removed from the PGU by the harvest robot, (see.

4.2.8). The robot transports each tray to the harvest unit where tray end caps are

removed. A processing robot then positions each tray into the harvest machine (fig.

75
Equipment

Reactor

Inorganic

salts

separator

Liquid/

!liquid heat

exchanger

Liguid/

gas heat

exchanger

Air

compressor

Accumulator

Manual

shut-off

valve

Mixing

valve

Electric

solenoid

valve

8 ack

:)ressure

valve

Table 4.2-7. Super Critical Water (

Quantity

required

8

4

Size

2.5" dia x

20" long

98 in J

2" dia x.

11" Ion_q

34.6 in`)

12" dia x

4" high -,

452.4 in`)

12" dia x

4" high

452.4 in 3

15" high x

30" wide x

13" dee?

5850 in`)

7" dia x

11" high

423.3 in 3

7" high x

4" wide x

5" deej_

140 in `)

7'" high x

4" wide x

5" dee_

140 in"_

5" high x

4" wide x

2" depp

40 in3

3" high x

4" wide x

4" deep

48 in3

Product

in

Slurry and

0 2 or air

Inorganic

salt=,

steam,

CO 2, N 2

Slurry is

heated,

super- --

critical

water is

cooled

O 2 or air

is heated,

supercritical

water is

cooled

Cabin air

or 0 2

Condensate

storage

Slurry

and

hygiene

water

3xidation System Component LJ'sdng

Product

out

Inorganic

salts and

steam, CO 2,

N2

Inorganic

salts by pass

others to

heat

exchangers

Compressed

air or 0 2

Reacto r

ready

slurry

Utility and

power

requirement

Pressure and

temperatu re

sensors

5639 W for

5 minutes

Sensors

Note: Pressure

on slurry

maintained by

sludge pump

Either 28 VDCt

115 VAC

812W

Quantity

sensor

Slurry composition

28 VDC

Comments

3700 psi operating pressure

700°F operating temperature

Double tube spiral coil

Double tube spiral coil

Should be downstream of

liquid/liquid heat exchanger

Isolate system loops for

maintenance

Controls concentration of

slurry by adding hygiene

water

28 VDC or

115 VAC

28 VDC or

115 VAC

Flow regulation (on/off

cycles)

Prevents contamination of

hygiene water by slurry

76
Equipment

Turbine/

generator

Fan

separator

Sludge

pump

Check

valve

Control

power

Size

24'" high x

24" wide x

36" deep

20,736 in 3

7" dia x

6" high ,,

230.9 in"_

10" high x

13" wide x

20'" deeR

2600 in"_

2'" high x

4" wide x

486"d3p

Total

volume

31,293.5 in3

Table 4.2.7. SCWO (Continued)

Product

in

High

pressure

steam

Water,

CO2,

N2

Reactor

ready

durry

Product

out

Low pressure

steam and 1

kW of electricity

Water,

CO 2,

N2

3700 psi

slurry

Utility and

power

requirement

Pressure,

speed, voltage

and current

sensors

115 VAC

anticipate

large power

requirements

373 W

6Wx6

units = 36 W

Comments

May or may not be used

Separates reactor outflow

water from CO 2 and N2

Approximately 20 Ibs/

batch in one hour

Prevents slurry bad<flow

through sludge pump

T

Move

tray to

PGU X Grow Move

to to

maturiW / harvest

Move \

tray to Sterilize

storage tray

Harvest

plants

R emove

tape from

tray

Move

tray to

sterilizer

Sepwata

plant

parts

Crop to

washer/

dryer

Wash

ordry

crop

X-waste toXo..o waste X-) waste to

SCWO grinder

Move

crop to

storage

Figure 4.2-20. Plant Flow Path Through CELSS

77
4.2-21). A cutter at the entrance clips plant stems close to the tray surface while the

roots are pushed out of the tray by the robot arm (sec. 4.2.8.3).

Air flow through the tray and harvest area puUs the loose crop, stems, and roots into the

harvest chamber. All material is drawn into an air pump and expeUed into CELSS food

processor separation chamber. Here, a cross-flow of air separates crop from chaff by

deflecting less dense biomass waste from direct passage through the chamber. Waste

and crop are gathered into separate-containers for subsequent processing.

Air pump

7

cro.flow --_

separator

Pressurized

air for J

crossflow

Discharge

tubes for X I,

crop and waste J

Wash/dry utility j

interfaces

Waste grinder

Washer/d ryer

4.2.7.2 Food Proeess_

Figure 4.2-21. CELS3 P/ant Harvester

Harvested food is coUected into a washer/dryer (fig. 4.2-21). Dust, dried nutrient

solution, and any other contaminants are rinsed off in a water bath. The washed crop is

then dried in a flow of warm, dry air. The edible material is collected and stored until

needed for space Station consumption. A crew member wig enter the CELSS module, as

required, to transfer food supplies back to crew quarters.

78
4.2.7.3 WasteMaterial

Waste material collected during harvest operations are ground and stored pending

additional proeessing. Finely ground waste is mixed with water to form a slurry that is

pumped into the SCWO reactor for direct waste regeneration (see. 4.2.6.1). The waste

slurry may also be processed for cellulose conversion to edible biomass.

4.2.7.4 CeUulose Conversion

In order to make use of the inedible biomass left over from the crop harvest, it will all

be run through the processor until finely ground. The inedible biomass can then be

eonverted into sugars that, in turn, can be fermented for use as a chemical feed stock or

edible protein.

Conversion is accomplished by means of hydrolysis of the cellulose material by cellulase

or eellulolytie microorganisms. When hydrolysis is complete, the sugars that are a

product of the conversion can be used as an energy source to aid in the fermentation

process that follows. Alcohols, ketones, hydrocarbons, fibers, etc. are examples of some

of the products derived from cellulose conversion.

Anaerobic, mesophilie, eellulolytie bacteria, which survive in medium temperatures

around 98.6OF, from natural aquatic environments are among the microorganisms that

have been isolated. These microorganisms are effective in converting cellulose into

singie-eell protein and ethanol through yeast fermentation.

Fungi are another group that can convert carbohydrates. Temphe, fungal mycelium,

grown on soybean cakes and wheat cakes is used in Southeast Asia as a high-protein food

source. Fungi species are known that operate under nearly any temperature and

humidity combination expected on Space Station. Fungi can also break down complex

carbohydrates not attacked by bacteria. For example, along with cellulose, which is a

carbohydrate, there exists a nonearbohydrate called li_min that also acts as a structural

component in higher plants. Lignin has no known human food value but is assimilated by

many varieties of fungi, some of which may be edible.

4.2.7.5 Parts Listing

Table 4.2-8 lists major CELSS harvester and food processing equipment.

79
Equipment

Plant

harvester

Air

pump

Crossflow

separator

Washer/

dryer

Waste

grinder

Motor

(Harvester,

see page 1)

Motor

(Air pump,

see page 1)

Cabling

Ducting

Quantity.

required

Table 4.2-8, CELSS Harvester Corn

Size

11'" wide x

35" ta_l x

60" deep

15" dia x

18" long

8" wide x

40" tall x

30" deep

15" dia x

18" long

15" dia x

18" long

Product

in

PGUtrays

with

plants,_._.

dried from

robot

Dissociated

plant mass,.

roots and

crop

Dissociated

plant mass,

roots and

crop

Crops

Plant and

root mass

Electric

power

Electric

power

Air

Product

out

Dissociated

plant mass,

roots and

crop

Separated

crops from

plant and

root masses

Washed and

dried crops

go to robot

Finely

chopped

plant and

root mass to

SCWO via

robot

Power to

actuate

harvester

mechanism

Power to

actuate air

pump

oonents

Utility and

power

requirements

Suction air

provided by

air pump

28 VAC.

300 watts

28 VDC,

400 watts

Pressurized

air for crossflow air

currents

(from

station)

Warm air

from station

Washing

water which

is potable

return water

28 VDC,

200 watts

28 VDC,

300 watts

28 VDC,

300 watts

28 VOC,

400 watts

Comments

Needs to be vibration

insulated as it is a

vibration source

Diaphragm type, sized to

accommodate potatoes

Separates by .deflecting

lower mass/greater surface area from higher

mass/lower surface area

particles

Washes and/or dries

crops only as needed for

an individual crop, i.e.

wheat might only be

dried, potatoes might be

washed and dried

Vibration isolation

req, ired (see Plant

harvester, page 1)

Diaphragm type, sized to

accommodate potatoes

(see Air pump, page 1)

Electric power to motors

Air flow routing, etc.,

crop flow

4.2.8 Robotics

CELSS module operation is fully automated. Robots are a key automation element

performing allplanting, harvesting, and waste handling operations. Space Station crew

members normally enter the module only for removing food supplies or to perform

maintenance or repair functions.

80
Two robots are mounted on a pair of tracks running full length of the module. One track

is above and one is below the center aisle (fig. 4.2-22). Each robot is on a column

between the two tracks and can move up or down between tracks. Longitudinal travel is

made possible by a powered roller platform riding on each rail

Figure 4.2-22. CELSS Robots

The harvest robot handles plant trays in the PGUs, planting newly seeded trays and harvesting

mature plant trays. It also transports trays to he plant harvesting and processing

equipment.

81
The process robot handles the tray after the harvest robot positions it in the harvest

equipment.

Reseeding trays with new seed mats is accomplished by the process robot operating the

seeder equipment. It also moves seed mat cartridges into position when replacing an

emptied cartridge.

The following list outlines robot major functions operating the plant growth and harvest

equipment.

CELSS Robot Functions

1. Take a clean tray from tray storage area.

2. Stretch tray to its full length.

3. insert tray into tray seeder.

4. After seed tape is put on tray, remove tray from seeder.

5. Compress tray.

6. insert tray into PGU.

7. Using optical and electrical resistance sensors, monitor plant growth; health; and

nutrient, moisture, and light levels.

8. Remove mature plant tray from PGU.

9. Compress tray.

10. Remove end caps from tay.

11. insert tray into harvester unit.

12. As tray enters unit, operate a plunger to push plant and root masses further into

harvester.

13. After plant and root masses are in harvester, remove tray.

14. CoUeet crop and waste products from their appropriate tubes.

15. Compress tray fuUy.

16. Put tray in tray sterilizer.

17. Put crops in appropriate storage bins.

18. Put waste products into waste management system

19. Remove sterilized tray from tray sterilizer.

20. Put tray in tray storage area.

82
4.2.8.1 RobotSupportStructure

Both robots are mounted on a pair of longitudinal rails running the full length of the

CELSS module. Each robot unit is installed on a column between the rails. Motion along

the rails is accomplished by powered roller platforms on each end of the columns. The

robot units move up and down the column to gain access to aLl equipment in the module.

4.2.8.2 Harvest Robot

The harvest robot has two extendable arms with tray-grasping latches at each end.

These arms hold s tray in either compressed or extended conditions and can extend or

compress a tray as required. One arm faces each end of the module to handle trays

oriented in either direction. The supporting column rotates the position of the

extendable arms to either"side of the aisleto service allPGUs.

4.2.8.3 lh'oeess Robot

The proeess robot handles plant trays through all operations of the food harvest and

proeess equipment and tray seeder. It removes tray end caps when trays arrive in the

proeessing area. After an opened tray is inserted into the harvest equipment, the

proeess robot moves it past the stem eutter and forces root mass out and into the

harvester biomass eoUeetion chamber.

Tray preparation and seeding is the process robot's second major activity. Empty,

harvested trays are cleaned, sterilized, and positioned in the seeder. After completion of

seeding operations, the process robot reattaehes end caps and places trays in ready

storage. This robot services the seeder with loaded seed mat cartridges as required after

each set of the 18 trays is processed.

4.2.8.4 Parts of the Listin K

Table 4.2-9 lists major CELSS robot components for both robots.

4.2.9 Module Paekagdng

CELSS module packaging is shown in figure 4.2-23. The common module shell

determines dimensions and gross volume for packaging the CELSS design. The module

83
Table 4.2-9, CELSS Robot Cor_

Equipment

Track

Pedestal

Trucks

(pedestal)

Planting

power

unit _

Telescoping

tray handling arms

Motor(s).

reversing

Motor

reversing

Actuator(s) 4

Power 1

unit

motor

(planting)

Pedestal

motor(s)

Motor(s),

truck(s),

pedestal

Harvest and

utility

power unit

Arm

( Harrest

and

utility)

Quantity

required

2

4

Size

27" long

x?

4" x 4"

x11'

14" x 16"

x 18"

2" x 8"

x 6.8'

(extended)

Product Product

in out

Electric Motion

power

Electric Motion

power

Electric Motion

power

Electric Motion

power

Electric Motion

power

)onents

Utility and

power

requirements

Support

structure

in module

Either 28 VDC

115 VAC

40 W each

Either 28 VDC:

115 VAC

40 W each

Either 28 VDC

115 VAC

140 W

Either 28 VDC

115 VAC

140 W each

Either 28 VDC

115 VAC

160 W

Comments

Longitudinal track

"above" and "below"

aisle way. Robot travels

along track

Supports and guides

planting and harvest

power units

Supports and moves

power units(s) to

required position along

aisle

Insert, remove, and

transport plant trays

Extend and retract telemoping arms

Move arms to insert or

extract trays

Operate tray grippers on

telescoping arms

Move power unit "up"

and "down" pedestal

Rotates pedestal (power

unit faces other side of

aisle)

Move pedestal(s) along

trad(s

Push biomar_ from tray

into harvest machine,

move crop to storage,

perform operating

functions r etc.

84
Equipment

Motor(s)

Actuator

Table 4.2-9. CEL$S Robot (Continued)

Quantity

required

(1 for

each o of

freedom)

6

Size

Product

in

Electric

power

Product

out

Motion

Tools 5 ?

(hands)

1 Electric Motion

power

Power

unit

motor

(Harvest

and utility)

Utility and

power

requirements

Either 28 VDC

115 VAC

40 W each

Either 28 VDC

115 VAC

140 W

Comments

Move arm to harvest

crop, handle tray, etc.

Operate robot '1land"

(or tool)

Various tools for

different robot tasks

Move power unit "up'"

and "down" pedestal

primary structure needs only minor ehanges for this packing scenario (i.e., removal of

unneeded features or creating new pierce points for fiber optic cable entry). The module

secondary structure (interior) is organized for specific CELSS equipment. Working area

height is increased to provide efficient volume use for plant growth. PGU structures are

installed to support plant growth trays and lighting systems. Tracks are installed for

robot mobility. Rack support structures are designed specifically for each CELSS

system.

4.2.9.1 Module Primary Structure

The Boeing-proposed Space Station common module is used as primary structure in this

packaging scenario. Available volume is fixed by an interior diameter of 164 in and a

length of approximately 35 ft. Changes to the common module include elimination or

radial berthing ports and one end berthing port. Special outer shell pierce points are

added for fiber optic cable entry (sec. 4.2.2.2).

4.2.9.2 Module Secondary Structure

The CELSS module interior structure is customized for specific plant growth equipment

and requirements. Support bulkheads are added from plant tray supports; frames are

installed to support lighting luminaries. Nutrient supply system tanks, pumps, and

plumbing are installed adjacent to PGUs in V-shaped areas between light panels. Rails

are installed down the aisle between PGUs for robot mobility. An alcove exists at the

85
w

I I I I I ] I I -

:L.]_[_, ,___,..LL_

I l I I I I I I I I

m_

OW

k___

w

"-d
robot servicing station to allow robot storage out of the aisle. The support structure for

other systems is installed as required for each unique item. Air cooling ducts are

installed along the rows of PGUs. Areas under the flooring and over ceiling hold ECLSS,

storage bins, nutrient supply tanks, and waste regeneration system. These units are all

on hinges to facilitate maintenance. ALl of the secondary structure is CELSS unique.

Material selection for CELSS module secondary structure is complicated by the highly

corrosive environment created by nutrient solutions. Metals, including stainless steel,

corrode. Plastics are used for much of the secondary structure adjacent to the PGUs for

corrosion resistance. Plastics are considered s viable candidate for other support

structures for weight savings. Metal interior module structure is limited to corrosionresistant alloys with protective coatings. Plastic structure material is selected for

stability, strength, and compatibility with CELSS materials and processes.

4.3 SYSTEM INTEGRATION

Packaging CELSS in one module amplifies each system's effect on and interaction with

other systems. No system design can be considered alone without considering its

interaction with other systems. Examples of system interaction and factors influencing

design are illustrated in figure 4.3-1 and the following sections.

4.3.1 Lighting System Integration

Lighting system conceptual design includea. Collected solar rays.

b. CoUected solar rays supplemented with artificial light sources.

c. Artificial light sources.

The first calculations of electrical power required ( 75 kW to provide efficient growth

illuminations see see. 4.3.2.2) eliminated artificial iLlumination for total plant lighting.

Electrical power in excess of 75 kW exceeded any reasonable power allocations.

CoLlected solar ray lighting only for 60 rain followed by 30 rain of darkness may not

promote normal plant growth. Thus, solar lighting alone is not considered an optimum

design alternative.

88
e-

.@

¢J

0

e_

.o_ W

\

/i
Several sources of artificial light to supplement collected solar rays are possible.

a. Direct fluorescent.

b. Xenon lamps.

c. HID lamps (High-pressure sodium).

Xenon and high-pressure sodium lamps are high-temperature, concentrated lightsources

and are considered in conjunction with a fiber optie light pipe distribution system.

Xenon lamps require excessive power compared to fluorescent or high-pressure sodium

lamps. Fluorescent and high-pressure sodium lamps require approximately the same net

power for equal plant illumination. The fiber optic light pipe and focusing lens array

required for high-pressure sodium lamps weigh much more than fluorescent luminaries

and represent a greater development risk. collected solar rays supplemented by direct

fluorescent lighting is the preferred lighting system for the CELSS plant growth

illumination preliminary design.

4.3.2 Thermal Control Integration

PGU thermal control is critical to normal plant growth. Total heat loads from plant

growth lighting are as follows:

a. Direct fluorescent lighting, 31,500 Btu/h from luminaries and ballasts and 8200

Btu/h from light energy on plants.

b. Collected solar ray/fiber optie distribution, 19,700 Btu/h from luminaries and 62,300

Btu/h from light energy on plants. Therefore, eoUected solar rays (natural light)

sizes PGU thermal control.

CELSS PGU thermal control must be compatible with plants. Cooling jackets may work

with luminaries, but are not feasible with growing plants. An atmospheric heat transfer

method is feasible. Moving air past the plants by convection is not possible in

microgravity but fans can maintain air motion to move heat away from plants. Forced

cool air flow is selected as the preferred thermal control system for CELSS PGUs.

9O
5.0 PARAMETER ESTIMATES

5.1 COST ESTIMATING PROCEDURE

The objective of the cost analysis was to provide a credible cost estimate for outfitting a

CELSS module. The cost estimate was based on ground rules and assumptions developed

in conjunction with the engineering staff as the study p_'ogressed. Several iterations

were used to aid optimizing preliminary design. Cost model sum maries, shown in table 5.1-1,

identify total CELSS module cost of $677.8 million, ready for launch. This cost consists

of (A) engineering costs of $176 million, (B) manufacturing costs of $579.8 million, and

(C) support costs of $98 million.

This cost compares favorably with the estimated costs for other Space Station modules

as shown in figure 5.1-1. (Note: the costs in fig. 5.1-1 are adjusted to reflect CELSS

module construction in 1990 instead of 2000.)

The two primary tools used to estimate the hardware acquisition costs for the CELSS

study were the Boeing parametric cost model (PCM) and the RCA developed parametric

cost model (PRICE H). Since PCM is structured to represent the Boeing Aerospace

Company costs and procedures it was used to integrate the acquisition cost estimate for

plant growth and to generate most subsystem component costs.

PCM develops costs from hardware physical descriptions and program constraints. This

model allows inclusion of costs generated by other methods. These throughput costs are

handled within the PCM logic the same as PCM-generated costs. This process guarantees

the proper impact on support costs (e.g., system engineering, ground test, program

management, etc.). This model permits Boeing to use acquisition cost estimates from

the best available source data.

Figure 5.1-2 iUustrates the source, type, and level of information that can be handled by

the Boeing integrated computerized system. As depicted in the U/ustration, the scope of

study was defined by NASA and amplified by Boeing to establish the overall design, test,

and fabrication philosophy required to successfully implement plant growth in space.

91
q_I

.q

...JI

rj ,,_

Ld

)-

¢fl

ILl

0=

'e[

O=

'4[

*°*°°o**...°_ °...,°°°.°.°

HI',,. u

IO

ov_9 Io CI_

oo t_ N

_1_OOO_OO_

_1 ...........

v_l

_o

On

z

Z_

_Z

_0

Z_

0o

ORON_N_ _OIN

"''*''''''-I

NR _IN

I

L

E_

_O ............

II

It

•°*** .........• li

o00ooo00000000ooo nlo

II

II

II

N ¢1_0 ogN

•n•

•_0 IO _r' iio

ii

¢DZ

bJZ

leul

¢D

uJ

*° .........

m

o_

¢D

_N__

_1.° ..... °..°.

_1__

II

0 *IQ _*0 tO ,-,4

•• II

_ (%1NuN

M

w=

I--

ELZ

_N__

_N____

=¢

I,--

¢)

I--

¢D

_L

I"

Q= Z

UJ

UJ

'e[

--¢

'el

92
Table 5. 1-1. CELSS-Laboratory Module P/ant Growth-Base Input File: CELSS

HARDHARE TOTALS (FROM ABOVE) ($M)

SUPPORT COST ($M),

ENGR MFG TOTAL

176.0_7 _05.801

ENGR MFG

SYSTEM ENGINEERING & INTEGRATION 9._91 -

SOFTHARE Et_GIIIEERING 8.025 -

SYSTEMS GROU/ID TEST CONDUCT 18.003 -

SYSTEMS FLIGHT TEST CONDUCT 0.0 -

PECULIAR SUPPORT EQUIPHENT (,.235 5.316

TOOLING & SPECIAL TEST EQUIPMENT - 33.156

LIAISON ENGINEERING 1Z.G5_ -

DATA 7. 079 -

PROGRAM MANAGEMENT O. 0 O. 0

SUPPORT EFFORT TOTAL ($M) 59._&E 3&._,72

579.E_7

TOTAL

9.491"_

8.o25 \

18.003 \

0.0

9.551 _'

33.156

7.079_

____:___/

97.960

C

TOTAL ESTIMATE ($M)

Module

cost

(x million $)

750--

500 --

250--

0

235.53_ _2.Z73

677.807 _D

2.1 612(A

17 NT

122!

IIIII1!

1359

114!

\% \_

653(8)

i=l=l=l=lsw_

_398xl

x\\\\X1

N

_\\\'x'l

590(C)

8!"""N

*\\\"1

",'d,'d,',i

N.\\\\NI

_,4921

N\\\"_

,x,\\\\Xl

\\\\\\1

_xxx_!

2.2.;.:.2.2.:.:

iiiiiiiiiiiiiiii So,*are

JJllJIJl] GFE outfitting

x_ Lab outfitting

lab module

(A) Estimate based on SS Phase B work

(B) Estimate based on ref ( ) contract report

(C) Cost adjusted estimate from this study

Est. _= 110(A)

,////,

.. _ _-"///.'!

: \,_.: \% \

\

Figure 5. I-1. Space Station Module Cost Comparison

93
___ Hardware designers

Concept ]Equipment _ ancl _na;UnfaCt_ring

• Weight

• Complexity

• Redundancy

• Development status

• Material

• Quality control level

• Software

etc.

Total

acclu isition

dollars

• Test program

• Schedule

• Spares philosophy

• Contract structure

etc.

"_ iHna;:zware_-[ 'fl

v

0

_,=other estimates

_.. GFEgivenandcosts other _

Program

input

sheet

• Ground rules

• Schedule

_: Labor rates Overhead

rates

• Factors

i Price

• Weight @

• Complexity

• Circuitry

etc.

Figure 5. 1.2. Costing Information Flow Diagram

These data, along with financial information relative to labor, support, and overhead

rates comprise the program constraints within which the models work.

Figure 5.1-3 iUustrates the data flow necessa_m] to develop component hardware

estimates. Engineering and manufacturing functionally describe the components that

make up the system. Each component description includes weight, hardware type,

complexity, quantity, learning curve, and manufacturing schedule. This hardware

information, in conjunction with the programmatic data described above, are processed

by PCM to generate the cost estimate.

PRICE H was used to generate hardware acquisition cost estimates for sensing devices,

optics, and electronic hardware. PRICE H inputs are program constraints and hardware

physical descriptions. The estimates generated by PRICE H were then throughput into

PCM.

94
J Definition data J • Sketches

Gro_ .system

• Rough program

plans

• Early equipment

lists

• Early weight

• Baselineconfiguration

• Firm program plan

• Make-or-buy plan

• Detailed equipment lists

• Functional inputs

• Vendor quotes

)efinition Trade studies

_nd Early .... Final baseline J_ -.-

,.,_,_,,,w I-rellmlnary .... _ UlO

'oat - .... w_ k_.I;n, final options

' - studi_ .w ......

uncertainty -" estimates _

_ _-- Bid scoping

_, Rules of • •

-_ I ihumb I 9.------ Detailed. _ mooe. ¢,_,-;,i_ --

u:._. J..., _ parametric =- -- -_" ..... -

..... --! I nl_Jii- .... I / models parameters

r'sumatLng I ( parametric I _= Firm proposal approacn I mooels process

Figure 5.1-3. Boeing Aerospace Co. Cost Estimating Approach Flowchart

The costs estimated by PCM/PRICE H are all traceable to standardized input forms,

with the information on the forms representing the engineering, manufacturing, and

planning decisions that defined the estimate. Therefore, configuration control of the

estimate was maintained throughout the estimating process.

The accuracy of this parametric approach is a function of (1) program and hardware

definition, (2) the depth of analysis that translated this definition into cost model inputs,

(3) the ability of the cost models to be sensitive to cost-driving conditions, and (4) the

inherent accuracy of the models.

More specifically, these considerations translate intoa. Quality of inputs.

b. Capability to handle NASA program conditions.

c. Inherent model accuracy.

Goodness of inputs is a function of hardware definition, program functionals, and

estimator's capability to express the system in terms of model inputs. As the CELSS

system definition evotved, considerable design detail yielded good hardware definition.

PCM/PRICE is designed to accept increasing amounts of detail as the design evolves; the

evolution results in more accurate estimates. Further, the technical and estimating

95
staff assigned to CELSS study have sufficient experience with the models to ensure

successful interpretation of design concepts into model inputs.

The ability to handle real program conditions is enhanced by using PCM to integrate the

total acquisition estimate. PCM is structured to be sensitive to varying design

approaches, internal organization structures, and subcontracting philosophy. Inputs to

the model are sensitive to design complexities, the use of off-the-shelf designs,

development status, etc. To summarize, inputs to PCM are those that have been proven

to directly relate to cost and customer reporting requirements.

Inherent model accuracy differs between PCM and the PRICE model. PCM estimating

relationships are based on statistical correlation to Boeing history as contained in its

standardized, company-wide data bank. These estimating relationships have been in

continuous development since 1972 and are specifically designed for aerospace systems.

Variance analysis has shown accuracy to within 23% when tested against known costs for

mechanical, electrical, electromeehanical, and propulsion hardware.

Estimating relationships in the PRICE models are proprietary to RCA and are not

available to direct verification. However, the PRICE H model can be, and has been,

calibrated to the Boeing aerospace environment using actual Boeing cost history and

physical characteristics of the hardware.

5.1.1 Co6t Parametric Ground Rules and Assumptions for CELSS

a. The estimate is in constant 1985 dollars.

b. 1985 full-scale development wrap rates for the Inertial Upper Stage program were

used.

e. Customer-requested changes are not included in the cost estimates.

d. Program management has not been discretely estimated.

e. Spares were estimated to be 5% of hardware costs for Boeing and subcontract.

f. The schedule was assumed to be nominal.

g. Sets of peculiar support equipment: one.

h. Developmental shop hours were estimated to be 25% of total Boeing engineering

hours.

96
i. Quality control hours were estimated to be 1596 of total Boeing-furnished labor

hours.

j. The estimate assumes high reliabilityrequirements in a very corrosive environment.

k. It is assumed Space Station electrical power would be used to satisfy CELSS

requirements.

I. Common module nonrecurring design costs are not included inthe estimate.

m. A rough-order-of-magnitude (ROM) manufacturing cost to buildone common module

isincluded.

n. The ROM weight for the solar ray collectorpointing system was estimated to be 500

lb.

O. Using rules of thumb, the cost to build the solar ray collector pointing system was

estimated to be $7 million.

p. Again using rules of thumb, the nonrecurring design cost for the instrument pointing

system was estimated to be $35 million.

q. Material sectors used reflect the use of corrosive resistant steel (CRES) for most

hardware items.

r. Ninety percent learning curve was assumed on high quantity items only.

s. Estimate does not include fee.

t. Modification costs to the common module structure were not priced.

5.2 WEIGHT ESTIMATING PROCEDURE

Weight estimating methodology employed in developing the CELSS weight statement

used preliminary design component weight estimating techniques. These techniques

require a wide range of input parameters, including volume/density estimates, specifically calculated temperatures, pressure, and heat loads. Weight estimate summary is

shown in figure 6.2-4.

Two basic assumptions apply to the CELSS weight analysis: (1) the source of the CELSS

electrical power is the Space Station, and (2)the external portion of the conducted

sunlight system (i.e., collector mirror, transmitter, etc.) is not included in the CELSS

module weight statement.

CELSS is separated into six functional elements for weight estimating purposes. These

functional areas are defined as follows:

97
a° Basic Capsule-Weight is derived from Space Station common module by removing

systems not pertinent to CELSS. Aluminum isthe principalstructuralmaterial.

b. Plant Growth Units-Weight estimates for the PGUs, which include the growth trays,

nutrient supply system, and lighting system, were based on preliminary sketches,

schematics, and equipment lists. The baseline lighting system was considered to be

conducted sunlight augmented with fluorescent lamps. Calculations used weights of

existing hardware (valves, pumps, fluorescent bulbs, ballasts, and fiber optics)

wherever possible.

Co Harvester-The harvester encloses a volume of approximately 1.3 m 3. Components

were defined from a preliminary design equipment list and a density factor applied

to each part.

d. Super Critical Water Oxidizer-Major components were defined and sized, including

the air compressor. Sludge pumps and heat exchangers are the major weight parts.

e. Robot-The CELSS robot consists of a harvester unit and a planter. The units can

move up and down along a pedestal connecting the tracks and rotate 360 deg about

the pedestal. Major assumptions in weighing the robot were (1) there are no highspeed requirements for the motors, (2) there are no heavy-weight requirements

because of zero gravity, and (3) there are six degrees of freedom for the harvester

unit arm. The weight statement reflects aluminum structures for the tracks and

mobile units.

f. Environmental Control-Heat dissipation requirements and the allowable temperature

range for the plant growth environment were the significant factors in sizing, and

therefore weighing, the environmental control system. The primary circulation unit

was sized for approximately 40,000-Btu/h heat load dissipation and the moisture

control system was sized for a moisture production rate of approximately 22.3 Ib/h.

go Weight Growth Allowance-To accommodate future weight increases due to design

and manufacturing problems and development test results, a 15% weight growth

allowance has been included in the CELSS weight statement.

98
6.0 SENSITIVITY ANALYSIS

Sensitivity analyses evaluated effects of each system on the CELSS module. Parametric

values formed the basis for evaluation. Primary evaluations were conducted on mass and

cost. Additional evaluations were conducted on selected systems for electrical power

and volume. These analyses provide a means of judging the relative and actual impact of

each system on the CELSS module.

These analyses indicate that electrical power and volume will drive technical design.

These resources are most limited on the operational Space Station. Cost will also drive

design by limiting design options to mitigate constraints of power and volume. Mass is a

relatively minor impact on the operational CELSS module. Mass penalty is a one-time

launch cost for the module. Consumable costs are not directly addressed in this study;

however, the nature of the CELSS system to recycle materials should keep this cost

within reasonable levels. A key resupply assumption is that an adequate CELSS waste

recycling system is operational.

6.1 SENSITIVITY ANALYSIS APPROACH

Plant illumination system comparison is the basis for this sensitivity analysis. Plant

illumination essentially determines edible biomass production. All other CELSS systems

respond either directly to illumination (thermal, atmosphere control) or indirectly

through biomass produced per day (robot, harvester, waste regeneration, etc.). Plant

illumination levels are set to 750 mieromole/m2/s. Plant lighting systems are designed

to provide this level during Space Station light-side operations. Dark-side plant light

levels are set to 75 micromole/m2/s for both artificial lighting systems. A system with

only solar light produces range of 750 to 1000 micromole/m2/s illumination level. An

adjustment factor based on biomass production is used to equalize the parameters for

solar-only and solar-plus-artificial lighting systems (see. 6.3). Sensitivity analyses use

the parametric values generated during the preliminary design and weighting/costing

study tasks. These values are compiled to evaluate four questions.

a. What are power, mass, volume, and cost parametries for each lighting option?

(see. 6.2)

99
b. How do power, mass, volume, and cost parameters compare between lighting

configurations? (see. 6.3)

c. What is CELSS power demand at any moment based on system activity? (sec. 6.4)

d. What are the parametric effects of mixing crop species to provide a balanced diet

with greater variety? (see. 6.5)

Analyses are discussed in subsequent subsections for each question. Conclusions and data

developed are engineering estimates because the Space Station current early

developmental stage precludes precise CELSS equipment parametric values.

Comparing systems of dissimilar design, but similar purpose, requires that a consistent

approach be used in calculating parametrics.

a. Volume: Internal CELSS module equipment volumes are used in system comparisons.

Internal module volume provides the plant growth space. Plant growth volume

influences hi.mass production. Internal module equipment volumes impact the

growth space. Externally mounted equipment, such as insulation blankets and solar

ray collectors, do not reduce potential growth space. This study's primary interest

is hi.mass production, which can only be accomplished internally.

b. Mass: All CELSS equipment mass are considered in comparisons. All equipment

must be lifted into orbit; launch costs are related to equipment mass. CELSS launch

cost must consider the mass of all related equipment. Once in orbit, equipment

mass has little impact or CELSS operation. Additional Space Station feb.,st fuel

mass will be needed; however, the amount is insignificant to overall station fuel

needs.

Co Electrical Power: All electrical power demands are included in comparisons. Power

usage by any CELSS system are chargeable to the CELSS power allocation budget

from the Space Station. CELSS system loads must be balanced to stay within

budget. Orbital light/dark cycles affect power allocation. Direct photovoltaic

conversion on light-side orbit wiU permit target power allocations. Dark-side fuel

cell operations wiU limit power allocation. CELSS system activities are geared to

I00
this cycle. Most power-consuming activity occurs during light-side phase. Ordy

critical plant support and illumination systems are operated during dark-side cycle.

Normal equipment operating power values are used to avoid skewing comparisons by

considering transient peak values.

do Cost: Total cost for aU equipment is used in comparisons. These costs are the

summation of engineering and development costs, hardware costs, assembly costs,

and support service costs. Launch costs are not included in values as they are a onetime, system-wide cost. Operational costs and resupply costs are outside the scope

of this study.

Four CELSS systems were evaluated for sensitivity analysis.

a. Solar ray collector only using fiber optic cables to _ine light to plants.

b. Solar ray collector with fluorescent light for low-level, dark-side illumination.

fluorescent lamps are mounted directly over the plants.

c. Solar ray collector with HID lamps for dark-side, low-level illumination. Fiber

optics pipe light to plants from HID source.

d. Artificial light only from HID source directly over plants. Direct-illuminating

fluorescent lights are used as a baseline for systems comparison.

6.2 SYSTEMS PARAMETRICS ANALYSIS

Each system parameter is pt_esented in tables 6.2-1 through 6.2-4. Bar chart plots

derived from data in tables for each system parameter are presented in figures 6.2-1

through 6.2-4. Evaluating these data indicates that electricaa power consumption

(table 6.2-1) can range from 6.8 kN to 87.8 kN peak demand. Major power consumption

depends on the system employed. Artificial lighting operated at high intensity consumes

83.4% of CELSS module power. Even low-intensity artificial lighting consumes about

62% module peak power.

101
ELECTRICAL ROWER

(MAJOR SYSTEMS

PLANT GROWTH

UNIT

LIGHTING

SYSTEM

THERMAL CONTROL

SYSTEM

DEMAND (WATTS) ARTIFICIAL SOLAR SOLAR

UNADJUSTED) ONLY ONLY FLOURESCENTS

SOLAR _

FO HID

TRAY SUPPORT SYSTEM 0.0 0.0 0.0 0.0

SEED PLANTER 0.0 0.0 0.0 0.0

SEED CARTRIDGES 0.0 0.0 0.0 0.0

TOTAL- 0.0 0.0 0.0 0.0

LOW LEVEL ARTIFICIAL LIGHT 0.0 0.0 10560.0 10320.0

ART INDIRECT LIGHTING 69660.0 0.0 O.0 0.0

SOLAR P.O. LIGHTING (INSIDENA 0.0 0.0 0.0

P.O. CABLE (SOLAR INSIDE NA 0.0 0.0 0.0

BALLASTS 3483.0 0.0 1056.0 1032.0

PROCESS CONTROLLER 8.0 8.0 8.0 8.0

EXTERNAL SOLAR COLLECTOR 0.0 375.0 375.0 375.0

EXTERNAL P.O. CABLE 0.0 0.0 0.0 0.0

P.O. fnside cable 0.0 0.0 0.0 0.0

TOTAL- 73151.0 33.0 11999.0 11735.0

RADIATORS 0.0 0.0 0.0 0.0

PUMPS/PANS/ACCUMULATORS 6886.0 2263.0 2400.0 2400.0

HEAT EXCHANGERS 0.0 0.0 0.0 0.0

INSULATION 0.0 0.0 0.0 0.0

TOTAL- 6886.0 2263.0 2400.0 2400.0

NUTRIENT SUPPLY

SYSTEM NUTRIENT PIPING 360.0

NUTRIENT REGENERATION 1820.0

NUTRIENT REPLENISHHENT 0.0

TOTAL = 2180.0

ATMOSPHERE CONTROL

SYSTEM

CONTAMINANT CONTROL 202.0

CONSTITUENT CONTROL 457.0

TOTAL- 659.0

360.0 360.0 360.0

1820.0 1820.0 1820.0

0.0 0.0 0.0

2180.0 2180.0 2180.0

WATE REGENERATION

SYSTEM

202.0 202.0 202.0

457.0 457.0 457.0

659.0 659.0 659.0

SUPER CRITICAL WTR OXI 373.0 373.0 373.0 373.0

SALT SEPARATOR 0.0 0.0 0.0 0.0

HEAT EXCHANGER 0.0 0.0 0.0 0.0

TANKAGE 0.0 0.0 0.0 0.0

TOTAL= 37).0 373.0 373.0 373.0

NODULE STRUCTURE

FOOD PROCESSING

ROBOTICS

PRIMARY STURCTURE 0.0 0.0 0.0 0.0

COMMUNICATIONS 0.0 0.0 0.0 0.0

ELECTRICAL SYSTEM 3784.0 307.0 970.0 970.0

DATA HANDLING 315.0 315.0 315.0 315.0

FINAL ASSEMBLY 0.0 0.0 0.0 0.0

SPARES 0.0 0.0 0.0 0.0

TOTAL- 4099.0 622,0 1285,0 1205.0

HARVESTER 0.0 0.0 0.0 0.0

PROCESSOR 0.0 0.0 0.0 0.0

STORAGE 0.0 0.0 0.0 0.0

WASTE PROCESSOR 0.0 0.0 0.0 0.0

INEDIBLE .MASS RECOVERY 0.0 0.0 0.0 0.0

TOTAL = 0.0 0.0 0.0 0.0

ROBOTIC GARDENER 193.0 193.0 193.0

ROBOT TOOLS 140.0 140.0 140.0

SUPPORT STRUCTURE 0.0 0.0 0.0

TOTAL= 333.0 333.0 333.0

SYSTEM ._AL- SYSTEM TOTALS- 87681.0 6813.0 19229.0

193.0

140.0

0.0

333.0

18965.0

PLANT GROWTH UNIT 0.04 0.0% 0.0% 0.0t

LIGHTING 83.4% 5.6% 62.44 61.9%

THERMAL CONTROL 7.9% 33.2% 12.5t 12.74

NUTRIENT SUPPLY 2.5t 32.0% ii.34 Ii.5t

ATMOSPHERE CONTROL 0.8% 9.7% 3.4% 3.5%

WASTE REGEHNERATIO 0.4% 5.5t 1.9% 2.0%

,V_)DULE STRUCTURE 4.7% 9.1% 6.7t 6.8%

FOOD PROCESSING 0.0% 0.0% 0.0% 0.04

ROBOTICS 0.4% 4.9% 1.74 1.84

i00.0% i00.0% 100.0% 100.0%

Table 6.2-1. Peak Electrical Power Demand Comparison

102
VOLUME (M3)

PLANT GI_TH

UNIT

LIGHTING

THERMAL CONTROL

SYSTEM

TRAY SUPPORT SYSTEM

SEED pLANTER

SEED CARTRIDGES

TOTALLOW LEVEL ARTIFICIAL LIGHT

SOLAR P.O. LIGHTING (TERMINALS)

?.O. CABLE (SOLAR INSIDE)

BALLASTS

PROCESS CONTROLLER

EXTERNAL SOLAR COLLECTOR

EXTERNAL P.O. CABLE

HID P.O. CABLE (INSIDE)

TOTALRADIATORS

PUMPSFANSACCUMULATORS

HEAT EXCHANGERS

INSULATION

TOTALNUTRIENT SUPPLY

SYSTEM NUTRIENT PIPING

NUTRIENT REGENERATION

NUTRIENT REPLENISHMENT

TOTALATMOSPHERR CONTROL

SYSTEM

CONTAMINANT CONTROL

CONSTITUENT CONTROL

TOTALHASTE REGENERATION

_Ys't_M

SUPER CRITICAL HTR OXI

SALT SEPARATOR

HEAT EXCHANGER

TANRAGE

MODULE STRUCTURE

TOTAL=

PRIMARY STURCTURE

SOLAR

ONLY

41.2

0.3

0.3

41.8

0.0

6.2

0.6

0.0

0.1

0.0

0.0

0.0

8.8

0.0

0.5

0.4

0.0

0.9

0.5

0.5

0.1

1.1

2.4

3.5

5.9

0.4

0.2

0.1

0.5

1.2

9.8

SOLAR ÷

FLOURESCENTS

41.2

0.3

0.3

41.8

6.1

0.6

0.6

0.7

0.1

0.0

0.0

0.0

8.1

0.0

0.5

0.4

0.0

0.9

0.5

0.5

0.1

I.i

2.4

3.5

5.9

0.4

0.2

0.I

0.5

1.2

9.8

SOLAR

FO HID

41.2

0.3

0.3

41.8

2.8

6.1

0.6

0.l

0.1

0.0

0.0

0.6

10.3

0.0

0.5

0.4

0.0

0.9

0.5

0.5

0.1

1.1

2.4

3.5

5.9

0.4

0.2

0.1

0.5

1.2

9.8

FOOD PROCESSING

ROBOTICS

COMMUNICATIONS

ELECTRICAL SYSTEM

DATA HANDLING

FINAL ASSEMBLY

SPARES

TOTALHARVESTER

PROCESSOR

STORAGE

WASTE PROCESSOR

INEDIBLE MASS RECOVERY

TOTALROBOTIC ARDEMER

ROBOT TOOLS

SUPPORT STRUCTURE

TOTAL=

SYSTEM TOTAL- SYSTEM TOTALS0.0

0.0

0.7

0.0

7.2

17.7

0.4

0.3

0.3

0.1

0.2

1.3

0.6

0.6

0.2

1.4

78.1

0.0

0.0

0.7

0.0

7.2

17.7

0.4

0.3

0.3

0.1

0.2

1.3

0.6

0.6

0.2

1.4

79.4

0.0

0.0

0.7

0.0

7.2

17.7

0.4

0.3

0.3

0.I

0.2

1.3

0.6

0.6

0.2

1.4

81.6

PLANT GROWTH UNIT 53.5t 52.61 51.28

LIGHTING 8.7q 1O.Nt 12.68

TNEPRAL CONTROL 1.2t 1.1% 1.1%

NUTRIENT SUPPLY 1.4q 1.48 1.38

ATMOSPHERE CONTROL 7.8t 7.4t 7.2%

WASTE REGERNENATION 1.5% 1.5% 1.5%

HODULE STRUCTURE 22.78 22.38 21.7t

FOOD PROCESSING 1.7q 1.68 1.68

ROBOTICS 1.8q 1.8% 1.78

lO0.Oq

Table 6.2-2. Volume Comparison

100.0% lO0.Ot

103
PLANT GROWTH

UNIT

LIGHTING

THERMAL CONTROL

SYSTEM

NUTRIENT SUPPLY

ATMOSPHERE CONTROL

SYSTEM

WASTE REGENERATION

SYSTEM

MODULE STRUCTURE

ONLY FLOURESCENTS

SOLAR +

FO HID

TRAY SUPPORT SYSTEM 21.0 21.0 21.0

SEED PLANTER 15.6 15.6 15.6

SEED CARTRIDGES 1.9 1.9 1.9

TOTAL= 38.5 38.5 38.5

5.7

50.6

0.3

98.8

0.0

LOW LEVEL ARTIFICIAL LIGHT 0.0

SOLAR F.O. SYS (INTERNAL) 50.6

PROCESS CONTROLLER 0.3

SOLAR F.O. SYS (EXTERNAL) 98.8

HID F.O. SYSTEM 0.0

0.0

50.6

0.3

98.8

69.0

TOTAL- 149.7 155.4 218.7

TOTAL= 22.8 22.8 22.8

TOTAL= 76.1 76.1 76.1

TOTAL= 6 •9 6.9 6.9

TOTAL- 69.2 69.2 69.2

79.5

49.8

18.5

PRIMARY STURCTURE

INAL ASSEMBLY

SPARES

79.5

49.8

18.5

79.5

49.8

18.5

TOTAL- 147.8 147.8 147.8

FOOD PROCESSING TOTAL = 45.7 45.7 45.7

ROBOTICS TOTAL= 115.4 115.4 115.4

SYSTEM TOTALS- 672.1 677.8

5.7%

22.9%

3.4%

11.2%

1.0%

10.2%

21.8%

6.7%

17.0%

lOO.O%

Illumination System

PLANT GROWTH UNIT 5.7%

LIGHTING 22.3%

THERMAL CONTROL 3.4%

NUTRIENT SUPPLY 11.3%

ATMOSPHERE CONTROL 1.0%

WASTE REGERNERATIO 10.3%

MODULE STRUCTURE 22.0%

FOOD PROCESSING 6.8%

ROBOTICS 17.2%

100.0%

Table 6.2-3. Cost Comparison by

741 .i

5.2%

29.5%

3.1%

I0.3%

0.9%

9.3%

19.9%

6.2%

15.6%

100.0%

104
MASS (EG)

PLANT GR(_TR

UNIT

LIGRTING

TRERR_L CONTROL

SYSTEM

SOLAR SOLAR +

ONLY FLOURESCENTS

SOLAR +

SO HID

TP_%Y SUPPORT SYSTEM 704.8 704.8 704.8

SEED PLA_tTER 32.0 32.8 32.8

SEED CARTRIDGES 257.0 257.0 257.0

TOTAL- 94.6 994.8 994.6

IOW LEVEL ARTIFICIAL LIGHT 0.0 900.0 1064.6

_LAR P.O. LIGRTING (TERMINALS) 1652.0 1652.0 1652.0

P.O. CABLE (SOLAR INSIDE) 51.7 51.7

HA/LASTS 0.0 135.1 135.1

PROCESS CONTROLLER 4.5 4.5 4.5

EXTER_L%L _LAR OOLLEC'bDM 2644.4 2644.4 2644.4

EXTERNAL P.O. CABLE 595.1 595.1 595.1

HZD F.O. CABLE (ZNSIDE| 607.0 924.0

T_TAL- 5503.0 6062.8 7071.4

RADIATORS 655.4 655.4 655.4

PUMPSFANSACCUMULATORS 752.0 752.0 752.0

HEAT EXCHANGERS 587.0 587.0 587.0

INSULATION 112.0 112.0 112.0

TOTAL- 2106.4 2106.4 2106.4

NUTRIENT SUPPLY

SYSTEM NUTRIENT PIPING 228.5 228.5

NUTRIENT REGENERATION 303.0 303.0

NUTRIENT REPLENISffNENT 348.4 348.4

TOTAL- 879.9 879.9

AT_SPRERE C{_qTROL

SYSTEM

CONTARINANT COWTROL 267.0 267.0

CONSTITUENT CONTROL 424.0 424.0

TOTAL= 691.0 691.0

WASTE REGENERATION

SYSTEM

SUPER CRITICAL WTR OXI 64.6 64.8

SALT SEPAHATOR 59.0 59.0

HEAT EXCHANGER 22.7 22.7

TANKAGE 87.9 B7.9

NGDULE STRUCTURE

228.5

303.0

348.4

879.9

267.0

424.0

691.0

64.6

59.0

22.7

87.9

TOTALPRIMARY STURCTUHE

234.4 234.4 234.4

6754.0 6754.0 6754.0

POOD PROCESSING

ROBOTICS

COMMUNICATIONS

ELECTRICAL SYSTEM

DATA HANDLING

FINAL ASSEMBLY

SPARES

TC_rAL53.0 53.0 53.0

423.0 423.0 423.0

604.1 604.1 604.1

NA NA NA

1034.9 1034.9 1034.9

6869,0 8669.0 8869.0

HARVESTER 117.9 117.9 1179

PROCESSOR 147,0 147.0 147.0

STORAGE 100.0 100.0 100.0

WASTE PROCESSOR 100.2 100.2 100.2

Z_DIBLE MASS RECOVERY RA NA NA

TOTAL= 465,1 465.1 465.1

ROBOTIC GARDENER

ROBOT TOOLS

SUPPORT STRUCTURE

_ALSYSTEM TOTAL- SYSTEM ._TALS6.5 63.5 63.5

46.2 46.2 46.2

136.1 136.1 136.1

245.8 245.8 245.0

19989.2 20549.0 21557.6

PLANT GROWTH _NIT 5.0% 4.8% 4.6t

LIGHTING 27.5t 29.5% 32.8%

TRER4qAL CONTROL 10.5% 10.3% 9.8%

NUTRIENT SUPPLY 4.4_ 4.3% 4.1%

ATMOSPHERE CONTROL 3.5% 3.4% 3.2%

WASTE REGERNERATION 1.2% 1.1% 1.1%

NODULE STRUC_JRE 44.4% 43.2% 41.1%

FOOD PROCESSING 2.3q 2.3% 2.2%

ROBOTICS 1.2% 1.2% l.lt

100.0% i00.0% 100.0%

Table 6.2-4. Mare Comparison

105
801

Configuration comparison

7O

6G

50

4O

o. 30

20

10

PGU

[] Art

E_ Solar

D Solar/Fluorescent

IT_ Solar/Hid

ILL THER NUT ATMO WST MOD FOOD

Subsystems

ROB

45

40-- ,t.s

?,

?,

,I 35- ,,

tl

//

30- _

//

-i_,

- Z

.Z

-- i 1/

F_

FI

rt

10 - ,/

Z

//

_ 25

E 20

O

_>

15

Figure 6.2-1. CELSS Electrical Power Configuration Comparison

"" ilii

!ill

ii!!

,, ri!i

,X :i:!

_x :.:,

R .:.:

Z N ::::

_%, ,,

,. :.1

:: x i:t i/

•. %- .,_

PGU

System comparison

ILL THER NUT ATMO WST MOD

Subsystem

E_] Solar

[_] Solar/Fluorescent

Solar/Hid

FOOD ROB

Figure 6.2-2. CELSS Volume Configuration Comparison

106
240

Subsystem comparison

2OO

160,

A

e_

o

= _2o,

8

0,

4O

-s

0

I--

_E

PGU

7 i

6-

5-

4-

3

2

0

'N

PGU

iill

ILL THER

//,,\,, ,:.:.

_,,,:!:!:

%'"i:i:i,,,

_'"iiiii

I_'"_:_,,,--"

NUT

_ ::::-"

:::::

_/, :.:.1 r/_ %\

" ilii

ATMO WST

Confkju ration

[] Solar

I_ Solar/Fluorescent

O Solar/Hid

ii

_ \\ .:-:

// \\ :.:

// _\ .:.:

" liiii

// "" 125:

,".\I_:!:

// _\' J;:;:

% ,x.'.I::::

% ×x fi!i

\\ gi:

// _\ g-:-

iii!i

x_l:!:!

NOD

 -iii #/.,

IP'/__ :::::

_'/-, _.\ ':-:.

FOOD ROB

Figure 6.2-3. CELSS Cost Configuration Comparison

Masscomparison

!8]

::;::1

ILL THER

[] Solar

!_ S°lar/J=lu°rement

I_ Solar/Hid

NUT ATMO W_T

Subsystems

i!ii!

// ,, :::::

// _ _ ,:.:.

// ,:-:-

// "-\ i-:-:

,...:i:i:

_:::::

//_ \\ ::::

// \\ :::::

l_:::::

MOD FOOD ROB

Figure 6.2-4. CELSS Mass Configuration Comparison

]07
Equipment volume requirements (table 6.2-2) are about 80 m 3. This is slightly over onehalf of a module for equipment. Additional space will be needed for maintenance and

access. An additional 43% is allowed for these functions (1). This totals 114 m 3 for two

crew members. PGUs consume the most volume, 53%. Slight variation in volume

distribution occurs with differing lighting schemes.

Approximately $749 million (table 6.2-3) are required for the firsttwo-person CELSS

module. Additional modules willcost about $459 million.

Mass values (table6.2-4) are within current shuttle23 600 kg launch limits, total system

mass averages 20 700 kg. Primary module structure, at 8869 kg, composes the largest

mass portion,43%. Illuminationsystem averages 5900 kg, about 27%. Water weights are

not included because plans are to use Space Station waste water for nutrient makeup.

8.3 ILLUMINATION SYSTEM COMPARISON

Lighting systems are the major differences in system designs. Each system optimizes

some aspect of CELSS design. The solar ray collector using fiber optic lightpiping has

low power consumption relative to other systems. This optimization creates conditions

that can negate the improvements. For example, the solar ray collector will be

shadowed for 30 rain out of every 90 rain. During the shadowed period, many plant

species will shift from photosynthetic to a respiratory state. Transition back to the

photosynthetic state can take a few too many minutes depending on species. This rapid

cyeling of metabolie state can adversely affect plant morphology and development. Less

than continuous light deereases wheat edible biomass yield and can increase growth

eyele.

Illumination intensity at the plant canopy forms the constant value to which each system

is designed. All other CELSS systems are sized to support illumination system

requirements. The fuLl-intensity illumination level during light-side operations is 750

mieromol/m2/s. This level (1)Life Science Research Facility NAS8-35471, 1985

corresponds with full-intensity wheat lighting (ref). Dark-side orbital lighting is

evaluated at full intensity (750 mieromol/m2/s), one-tenth intensity (75 mieromol/m2/s)

and module ambient lighting (_lmicromol/m2/s).

108
Light-side lighting is provided by a visible light solar ray collector (fig. 6.3-i). This

collector connects with fiber optic cables that transmit the light to the plant growth

areas, fiber optic terminal illuminators distribute the solar light to the plants at

predetermined intensities. Each lighting system that uses a solar ray collector uses the

same collector design. This reduces variability in comparing each lighting system.

Solar

position

sensor

Cooling

air

supply

Fresnel lens

Selective radiation

coated dome

Dome

motor

air return

Module

skin

Rotation

control

motor

Coolant { Supply Return

F/gum 6.3-1.

Fiber optic

transmittirKJcable

Fresnel Lens Lighting System

with electrically powered

Fan

Dark-side iUumination originates artificial light sources.

These sources are either fluorescent or HID lamps. Electrical power is drawn from space

Station fuel cells. No significant power sources are on the CELSS module.

Four illumination systems are initially considered in the preliminary design.

a. Artificial full-intensity illumination only.

b. Solar ray full-intensity illumination.

109
c. Solar ray full-intensity illumination plus fluorescent dark-side partial-intensity

illumination.

d. Solar ray fun-intensity illumination plus HID dark-side partial-intensity iUumination

using fiber optic cables to pipe the light.

Determining an optimum iUumination system was the sensitivity analysis goal. An

optimum system produces maximum edible biomass per unit of Space Station volume.

Edible biomass produced per kilowatt consumed by CELSS module is considered in

selecting the best illumination system. IUumination system power consumptions are

compared in figure 6.3-2. A discussion of each system's electrical power demand

follows.

2o

lO

o

Artificial Solar Solar/Fluorescent

Configurations

Figure 6.3-2. Illumination System Power Comparison

Solar/Hid

HID lamps produce light at high intensity that is routed to plants through fiber optic

light pipes. This approach was selected to minimize subsystem volume and power

requirements compared with direct fluorescent or direct HID illumination. Continuous

artificial lighting subsystem power demand is 73 kW (table 6.2-1). Total CELSS power

demand reaches 87.7-kW peak power when supporting systems are included. This

significantly impacts thermal control requirements, driving it up to 6.9 kW. Just the

II0
power loss from line drop and electrical connections approaches 4.1 kW. These latter

two values alone nearly add up to the total power requirement for the next most powerintensive system, (solar plus fluorescent at 12 kW). With total Space Station power in

1999 predicted at 210 kW, the artificial-only lighting system would draw 44% of station

power. This massive power demand essentially eliminates artificial lighting as the sole

light source.

Alternative design uses a visible light solar ray collector (fig. 6.3-1) as the sole

illumination source. These collectors are mounted on Space Station masts for optimum

exposure to sunlight. Fiber optic cables carry the collected sunlight to the PGUs. Light

is directed onto the plants by columniating fiber optic terminal illuminators. No plant

illumination occurs during Space Station dark-side operations. Power requirements total

0.37 kW for the solar light collector subsystem. This power drives motors and sensors

that maintain collector orientation to the Sun. The intense light level does require an

extensive thermal and atmosphere control systems. These systems consume 2.3 kW and

0.7 kW, respectively. Overall CELSS system demand is 6.8-kW peak power (fig. 6.3-2).

This uses 3.2% of Space Station power. A significant question arises about the effects on

plant physiology and morphology caused by 16 dark/light cycles per day. Yields may be

substantially lower and growth cycles greatly lengthened.

Hybrid lighting systems are proposed to resolve the plant growth questions associated

with a solar-only system while avoiding the high energy requirements from a fullintensity system. Hybrid systems use solar collectors during light-side operations, then

shift to low-intensity artificial lighting during dark-side operations. The low intensity

maintains the plants in a photosynthetic state, provides phototrophic stimuli for

orientation, and maintains a normal lighting cycle. Low intensity levels would equate to

a cloud passing over a field, a condition plants are adapted to handle without adverse

physiological or morphological effects. Crop yields probably are going to decrease under

hybrid lighting when compared to continuous, full-intensity lighting. This results from

decreased total photon flux per day because 33% of each day is at 10% full illumination.

Identieal solar eolleetion subsystems are used for both hybrid systems. This is the same

colleetor used in the solar-only system. Fluorescent luminaries are fixed directly over

plants in one hybrid system. Point-source HID lamps are centrally located in the CELSS

module with fiber optie light pipes to the plants in the second hybrid system.

III
Fluoreseent fixtures are known technology that will require little additional development

for CELSS applieations. Excellent light control and distribution is possible with

luminares design. Fiber optic terminal illuminators are integrated into luminares (fig.

6.3-3) to eonserve mass and volume. Problem areas inelude: mercury content of lamps;

short life span beeause of rapid on/off eyelin_ lamp replaeement, and mutual

interferenee, whieh limits close spaeing of lamps. Designs created during this study

suggest that all of these problems are manageable. For example, mutual interferenee by

floureseent fixtures is eliminated by installing the fiber optic terminal illuminator

between them to aet as a shield. Solar plus fluoreseent use 12-kW peak power (fig.

6.3-2) for illumination. Thermal control adds 2.4 kW and atmosphere eontrol adds

0.7 kW. Total CELSS peak-power consumption is 19.3 kW; about 9% of Space Station

available power.

Plant

trays

Fluorescent

tubes

Light shines

towards plants

Figure 6.33. Combined Solar and Fluorescent

through

fiber ootic

emitters

The HID lamp system uses high-pressure sodium lamps enelosed in eylindrieal fixtures

fitted with focusing lenses (fig. 6.3-4). These lenses focus light onto fiber optic cables

that then pipe the light to the plants (fig. 6.3-5). The same terminal illuminators used

for solar eoUeetors distribute the light. Subsystem advantages are the high-efficiency

lamp, centralized cooling, simplified maintenanee and hazardous-material containment.

112
Fiber optic cables

_---_- Collection

/ cable to bundles

_ Focus lenses

. _, Hid light

Hid light is

focused onto

fiber optic cable

ends.

Fiber optic

bundles deliver

light to PGUS.

End view of

lighting system

Fiber optic bundles

out to PGUS.

Packagingplan

for six Hid lights

Figure 6.3-4. Hid Lighting System

Problems are light loss at interface with fiber optic cable and the need to preheat lamps.

This system uses 11.7-kW peak for illumination (fig. 6.2-1). Thermal control and

atmosphere control are 2.4-kW peak and 0.66-kW peak, respectively. Total CELSS

module power requirement is 19-kW peak (fig. 6.3-2); about 9% of Space Station

available power.

Illumination systems power analysis suggesta. Solar-only illuminator provides the best illumination per watt.

b. Hybrid systems are essentially identical in performance.

Co Artificial-only lighting system power demands are prohibitive. Because of the

excessive power demand, artificial-only lighting is dropped from further

consideration in this study.

113
Solar collection

light source

module

Hid light

source

Figure 6.3-5. Cornbined Solar and Hid Lighting

Further analysis needs to consider power cycles and edible biomass production to verify

the analysis. Power cycle analysis is presented in section 6.4. Insufficient information is

available to conduct edible biomass production analysis.

Comparing mass of illumination systems (fig. 6.3-6) focuses on the three remaining

systems; solar only, solar plus fluorescent, and solar plus HID. The solar collector

subsystem has considerable mass (5503 kg_ fluorescent subsystem adds 559 kg for a total

of 6062 kff; HID subsystem adds 1564 kg, for a total of 7067 kg. Illumination system

mass analysis suggesta. Solar-only illumination provides best illumination per kilogram

b. Solar plus fluorescent provides best illumination per kilogram for hybrid system.

o. Solar plus HID has highest illumination-to-mass ratio.

Comparing systems on a percentage basis shows that differences range from 10% to 28%.

114
A

O

H

OI

v

¢0

22

20-

18

16

14-

12-

10-

8

6-

4-

2-

0

Solar SolarlFluorescent Solar/Hid

Configurations

Figure 6.3_. Illumination SF_tem Mass

Table 6.3-1

Solar plus Solar plus

Option Solar only fluorescent HID

Solar only NA 1096 28%

Solar plus flour 1096 NA 1796

Solar plus HID 28% 1796 NA

Cost analysis (fig. 6.3-7) indieates that solar-only system has lowest illumination system

eost at $161.2 million. Four pereent more will purehase a fluoreseent system at $167.3

million. Solar plus HID eosts $230.2 million, a 4396 inerease over solar-only eosts. These

eost differences refleet the development cost assoeiated with new systems. Solar

eoUeetor designs exist but must be redesigned to withstand spaee conditions.

Floureseent fixtures already exist in spaeeeraft and will need little additional

development. Using HID with fiber optics is a totally new lighting eoneept. This

eoneept will suffer high development eosts; especially to overcome light losses at

junctions. Illumination cost analysis suggestsa. solar-only iUumination has lowest net cost.

115
800

7OO

6OO

5OO

A

o 4O0

E

o 300 (.)

200,

100'

Solar Solar/Fluorescent

Configuration

Solar/Hid

F/gum 6.3-7. Illumination System Cost Comparison

b. Solar plus fluoreseent cost is marginally higher than solar only.

e. Solar-plus-HID high cost results from extensive development and design work

required by this new system.

Volume analysis (fig. 6.3-8) indieates that lowest illumination system volume penalty is

the solar-only system. Solar-only system requires 6.8 m 3 internal module volume. Solar

plus fluorescent system needs an additional 1996 internal volume totaling 8.1 m 3. Solar

plus HID is 5196 larger than solar only requiring a net internal volume Of 10.3 m 3.

Illumination volume analysis suggestsa. Solar,only illumination has lowest net volume.

b. Solar fluorescent has best volume of hybrid systems.

116
E

_=

O

9O

SO D

70-

60-

50

40-

30

20 _"

10

0

Solar Solar/Fluotescerrt Solar/Hid

Configuration

Figure 6.3-8. Illumination System Volume Comparison

e. Solar plus HID system has largest illumination system volume.

CELSS module sensitivity analysis considers the illumination systems plus all additional

CELSS systems. Table 6.3-2 summarizes these data.

Table 6.3-2. rllumination System Parametrie Comparison

Option Mass Power (kW) Cost (MS) Volume (m 3)

Solar only 19919 6.8 724 78.1

Solar plus 20549 19.2 730 79.4

fluorescent

Solar plus HID 21544 19 793 81.6

OveraLl, the best choice is solar-only based on parametries. Solar plus fluorescent is

primarily penalized by the power requirement. The other parametric values are too

close to call significant. Solar plus HID is marginally better in power but significantly

117
poorer in mass and cost. This system could become more attractive when improved fiber

optics reduce the power requirement. Maintenance, safety, and accessibility factors also

favor the HID approach in the hybrid systems. Unanswered plant physiology and

morphology questions haunt the solar-only system. Satisfactory plant growth and

production under this system would make solar-only the logical choice for CELSS.

Several factors need evaluation under the three lighting systems.

a. Growth period to maturity (harvest).

b. Edible biomass production.

c. Oxygen generation levels.

d. Carbon dioxide uptake.

e. Transpiration rates.

f. Nutritional values of edible biomass.

When these factors are known a system selection can be made.

6.4 ELECTRICAL POWER UTILIZATION ANALYSIS

Electrical power may be the most limited service provided by Space Station. CELSS

power demand must be tailored to fit station resources. Analyzing electrical power

demand requires developing load-cycle flow charts. These load-cycle flow charts

combine Space Station operational constraints, how often and how long a system

operates, and the loading placed on each system. These factors are plotted out as a

function of time to analyze CELSS power demands at any time. The plot is continued

until every normal function performed by the CELSS is incorporated at about a 21-hr

cycle. This results in every normal power consumption combination being considered in

the 21-hr load-cycle flow chart. The time period required for every operation is a power

duty cycle. Duty cycles repeat continually until some new power consumption

combination is established. Table 6.4-1 is a CELSS load-cycle flow chart using the solar

plus fluorescent light system. Figure 6.4-1 plots the total power demand. Examining

these charts allows general conclusions about this system. CELSS power demand

responds sharply to orbital light/dark cycles. Power demands levels are relatively

constant for each orbital phase; the exception is at cycle hour 18. Twenty-one hours

forms an electrical power duty cycle during which every normal power-consuming

operation occurs.

118
119
Q

o*

w,J

u_

w,J

ORIG1NAI: PAGE IS

a _

o

120
18

Demand flow

12

"D

r10

8

16-

14-

1

i

6-_

v,

v,

w,

4-_

v.

v,

v,

2 - r/

0

[]Running average

4 6 8 10 12 14 16

Time (hours)

/.4

"A VA

"A YA /4

"AYA "A VA

'A YA /,4

rJva

NH

18 20

#A

Figure 6.4-1. Electrical Rower Load Cycle

Detailed load-cycle flow ehaz't examination reveals the factors that determine total

power demand. IUumination has minimal impact on light-side power demand. This tow

demand results from using solar coUeeto_s for lighting. These collectors require only

373W to capture 8 mill lumens. This 373W drives the lens-pointing system that maintains

optimum coUector orientation. Sun-side thermal control and atmosphere control are

relatively high values as they remove the heat imported by direct solar iUumination.

Light-side total CELSS power demand averages about 6.8 kW.

Artificial lighting, even at one-tenth intensity, creates a heavy power draw during darkside operations. This draw averages about 11.6 kW. Thermal and atmosphere control

average of CELSS dark-side power draw is about 14.5 kW. This equates to ?96 of Space

Station power for CELSS dark-side operation using fluorescent low-intensity

illumination.

Power perturbations occur as CELSS supporting systems are activated to perform their

tasks. All possible supporting tasks were scheduled during light-side operations for

preparing this load cycle flow chart. This practice conserved Space Station stored power

during dark-side operations. For example, robotic gardener activates at hour 11 and

121
ORIGINAL PAGE I8

OF, POOR QUALITY,

operates during orbital light cycles until hour 17.5. During this period additional power

demands are crated when the harvester and food processor operate on plants collected by

robotic gardener.

The Supercritical water oxidation system startup creates the largest CELSS power

perturbation at hour 18.5. During this half-hour light-side period, the SCWO reaction

chamber is heated to initiation temperature. Subsequent SCWO reactions are

exothermic requiring no additional chamber heating. High-pressure compressors are

required to sustain reactant flow into the reaction chamber. These compressors operate

contimiously through light and dark cycles for 2.5 hr until cycle hour 21. SCWO impact

on thermal control is minimized through a highly efficient liquid cooling subsystem.

CELSS module overall power loading ranges from 6.3 kW to 15.7 kW with the highest

draw during dark-side orbit. Average CELSS power demand is about 9.4 kW for both dark

and light cycles. A three datum running average is calculated for this example system

(table 6.4-1). The running average is plotted in figure 6.4-2. The graph suggests that

sustained power draw from Space Station can be held to 9.5 kW. This approach requires

a power storage device on the CELSS module. A power storage device imposes volume,

cost, and weight penalties but can reduce limitations created by dark-side power surge

demands on the Space Station.

14

10

A

r"

8

O

r=

v

,_ 6

12-

,JvAr:

_,vAr/

/JYAr/

/I v.l I,,

#l V_l v..

/IV, IV',

/|vlv,

/|V,4V.

4 /iv,iv.

/ivAv.

zlvav

2 /IVAV.

/=vav

_.v.v

0 , I _1.4 V,

0 2

Demand flow

_--_ Running average

I

4 6 8 10

Time (hours)

/i V.41 IV

/_Y.4 V

zl VA]¢;'

A V'_I V

/qVAV

/I_AV

,'11'1,4gt

20

Figure 6.4-2. CELSS Running Average Power

122
An alternative approach to reducing power peaking is to alter system operations. This

rescheduling approach may optimize system operational periods and loading to minimize

power demand fluctuations. For example, shutting off lights during SCWO system

operation reduces power consumption by up to 1.8 kW light side and up to 12 kW dark

side. Arranging this action to coincide with a plant's photoperoid can save power without

reducing yield. Load cycle flow charts provide a means to examine this type of power

de mand rearrange ment.

6.5 CROP-MIX ANALYSIS

Mixed crop systems are needed to support long durations, manned space flight. These

crops must be highly efficient in light utilization and provide a balanced diet. This crop

mix sensitivity analysis examines representative plant species effect on CELSS. Three

representative crop species are used in this study to examine plant species selection

effect on CELSS. These selected species were chosen for two purposes.

a. The species provide physical dimension models for a grass (wheat), legume (soybean),

and tuber (potato) to use during preliminary design.

b. The species model plant productivity effects on CELSS parametric values. Plant

dimension effects on preliminary design are discussed in section 4.0. The plant

dimension variations required extensive flexibility in plant growth unit, robot,

harvester, food processor, structures, and illumination design. Systems less affected

are those that provide supporting services, such as atmosphere control, thermal

control, and storage.

Productivity effects on parametrics examines three crop characteristics.

a. Edible hi.mass produced per unit volume (m3).

b. Growth period from planting to harvest.

c. Biologically recoverable calories per gram of dry edible biomass.

Usable calories per day per unit volume (daily yield) is determined by these three

characteristics.

123
Edible plant biomass used in this study are the wheat berry, soybean berry, and potato

tuber. Although some other parts of each plant may be edible it would require secondary

processing technology that is not currently identifiable. Growth period used is for

optimum growing conditions with illumination adjusted for maximum yield at maturity.

Period selected results in a maximum biomass production per growth day. Crops may be

harvested green (soybean) and dried using waste heat from thermal control system.

BiologicaLly recoverable calories are those that can be obtained from the crop edible

parts by a human eating a balanced diet. For example, wheat eaten alone yields about

3.3 cal/g, but when eaten as part of a balanced diet yields about 3.7 cal/g.

Analysis demonstrates that increased CELSS volume requirements results from reduced

yield per unit area, longer growth periods, or decreased calories per gram of edible

biomass. For example, increasing the wheat growth cycle from 62 to 85 days reduces

edible biomass harvested per square meter per day by a proportionate amount (37%). To

compensate, larger areas are harvested, which in turn requires more PGUs. Each PGU

adds 1.71 m3 to CELSS volume. This increase in growth period may also increase total

power requirements because a larger system maintenance overhead occurs with larger

modules.

Multiple variations in productivity factors result in algebraic, not additive, changes in

daily yield. For example, table 6.5-1 contains productivity values for wheat, soybean,

and potatoes.

Table 6.5-1. Productivity Figures

cal/G gram/m2 cycle Increment

Wheat 3.6 (100%) 2400 (100%) 62 (1009Q 1.0

Soybean 4.0 (111%) 950 (39.6%) 100 (161%) 5.9

Potato 3.7 (102%) 3275 (136%) 115 (185%) 1.3

Using wheat as a baseline (increment = 1), a quick examination shows that soybeans

require about 5.9 times the volume as wheat, and potatoes require 1.3 times the volume

as wheat to produce the same daily yield. Major differences in daily yield are caused by

the compounding of the effect of differences in each productivity value. These

productivity differences effect on the CELSS module are examined in a crop-mix

124
analysis (table 6.5-2). This analysis relates the proportion of each type crop grown to

the parameters for the CELSS module required to support the crop mix. A 10096 wheat

crop (set 1 on table 6.5-2) uses 79.8 m 3 of module volume, crop 8.5 kW of power. A

change to 10096 soybeans results in a need for 342 m 3 and 28 kW of power. This is a

difference of 42096 for volume and 32996 for power. This is not the predicted 59096

increase because some of the costs are absorbed in the overhead penalty common to all

systems. It does demonstrate rapid changes in parameters that can occur with a change

in crop. The analysis also shows that when crops with similar productivity values are

mixed (5096 wheat, 5096 potatoes, table 6.5-2) the changes in module parameters are

relatively minor. Table 6.5-2 presents eight crop-mix variations. These scenarios are

graphically compared in figures 6.5-1 through 6.5-4 for each parameter.

The results of this analysis supports a case for intense research into three areas to

improve CELSS productivity.

a. Screen plants of the world for very high productivity crops, identifying several

plants that can best provide the human nutritional needs, while retaining high

productivity, is essential to practical higher plant CELSS development.

bo Inedible-to-edible biomass conversion procedures and equipment will improve daily

yields. Commonly used crop species have a high proportion of inedible biomass.

This figure often exceeds 50% and may be higher. Converting this inedible biomass

into a food material can effectively double daily yield.

Co Examine single cell organisms for species that can supplement a diet based on a few

higher plants. These organisms would be used to provide essential nutrients

available only in very small amounts in higher plants. Genetic manipulation may be

required to develop the species characteristics desired.

125
= _c

ooo

ew

r.i

E

N |

_(o

_, oo {el

• ° , .

• oo ,_.

_,,,

i :z ,-

...... :'....° i "" , __ 9, '_" _ _. _ ,-', r,- _,_ _ r,", _1 e4

, ._ ._ _ ._ _ ,

-°°0;_ ........ •,.,°..°°° ,°°,_... .°°._°. o _.

_" "_.._.............. _'." '",°°..I_ _....... !.._o_o_ ..... ,_ _o_.....

g'" { {{

e4

............... _ _ _ I_

..... = 1 = = 1 =

126

ORIGINAL PAGE IS

0F_ POOR QUALITY
6O

O

e.,

40

8

o

X

30

o

= 2O

el

10

_Om

B

m

-k'%_

_\\\\\'x'l

*\\\N

_\\\N

0 I"'" ....

1

k\\\\\X

\%%%%\_

xX\\\\_

_\\\\\% \\%\\%_

%%\%\%-_

%\\\\%M

,X\\\\\_

2

x\\\\\_

%%%%%%%

N\\\N

X\\\\\N

%N\N\\N

3

Mix comparison

_\\\\N .......

xX\\\\X'I .......

N\",_\\N 73.'233t

4 5

Crop mix scenarios

4\\\\\\\ _\\_\\\

_\\\\\\\ \\\_\\x

_\\\\\\_ \\\\\\_

X\\\\\_,....... %\\\\%_

%%\\N%_

_\\\\\\" _\\\\N

_\\xxxx_ \%\\\\_

\\%JK\\\I

6 7

.........

_\\\\\\H

8 9

2.4

Figure 6.5-1. CELSS Crop Mix Mass Comparison

2.2

2.0

1.8

"o

: 1.6

=

,,.,=

o 1.4

1.2

= 1.0

o

0.8

0.6

0.4

0.2

0.0

m

m

-- l,,,,,\\\\\x_

X\\',,Ix\\_

1

,x,\\\\',_

_\\\\\v

,',,,\\\\'%

\\\\\\N

x\\\\\'R

_\\\\_,------,

....... _\\\\\\,

_\\\\%\"

_'"" k\\'1_\N _\N

2 3

Mix comparison

4

_xxxxx

_xxx_x_

X\"4K\_

5

Crop mix scenarios

_\\Mk\\\

6

_ _xxxx\_

_xxxxxx

-,,,\\\\_ ...............

_\\\\_ ........ I .......

_\\_,I........ \\\'1L'X\\x _i ....... _\\',_\_

7 8 9

Figure 6.5-2. CELSS Crop Mixes

127
35

3O

25

2o

Q

E

o 15

;>

10

5

0

B

1

ORIGINAL PAGE IS

OF POOR QUALITY

_\\\\\,,

Mix comparison

I

I

I

i

O--1E

_X\\\\'_ "\I_\%.\\%.% \\''" _ _,\\\\\x

,\\\\\\_ e,xxxxxx "_'_"" ........

....... r_,\\x%x_ • x x x x x • I_._.\\%%',o

_.\\%%\\

\\\IL\\\ I_\\",1%\\ \\\'lk\\' .._._x .,_ x •

3 4 5 6

%%%%%%%

\\\\\\\

x_xxxxx

\\\R\\_

7

Crop mix scenarios

Figure 6.53. CELSS Crop Mixes (Volume)

%%%%%%%%

%\N\\N%_

\\\"i'%\\_

8

_xx

%%X% %%_

%%%% _\%

%%%%

%\%\

%XX% _\%

%\\%

i .... )5)

9

28--

24-

20--

16

=o

12

,X\\\\\_

,',,,\\\\%_

1

x\\\\\R

,X\\\\\ _,

x\\\\\N

_\\\\N

N\N

X\\\\\N

X\\\\\N

%\\\%\_J

\\\%\\N

2

O,%%xx'_

_x_x_x

_%\\\\,

--_-_-_-_-_

\\\\\\

\\_k\\

3

Mix comparison

%%%%%%% x\\x\x_,

_xx_xx_

....... &\\\NR I

%%%%%%_

4 5

Crop mix scenarios

_xxxxxx_

_xxxxx_

_xx_xxx_

6

_,\\\\\\N x\\\\\'_

%,%,% _.._. \ \'NI

,_,\\\\\_1

' iN\\\\,q

_,\%.\\\X%1

NX\NX\X1

_.%X%l%\\%1

7 8

X\\\\\\

\\\\\%\

XX\\\\\

,xxxx_x_

×\\_\'_

9

Figure 6.5-4. CELSS Crop Mixes

128
7.0 RESEARCH AREAS

Major increases in CELSS data base are necessary for fuU-scale CELSS module

development. Research programs are needed to develop this data base. Biological,

engineering, and technology areas that need additional research were identified during

this study. Significant differences in the study results can occur as values become more

concrete. For example, increased effectiveness in coUecting direct solar energy may

reduce weight, cost, power, and design complexity. Even known values in many areas are

based on 1g experience and may change in a microgravity environment. For example,

plant size and growth characteristics are unknown for mierogravity conditions. Even a

modest increase in plant size can add significant volume to the PGUs.

A research area compilation is provided in this section to aid the reader in understanding

the unknown aspects of the CELSS. This listing identifies areas within which are many

specific research topics. A detailed listing is too long and tedious to meet the purpose of

this study. Three categories are identified:

a. Biological Research Areas - Research areas involving the growth, morphology,

nutrition, reproduction, or culture of plants in a microgravity environment. For

example, genetic engineering plant species to provide improved nutrition.

be Engineering Research Areas - Research areas involving the construction, design,

material, and integration of CELSS materials and equipment. For example, PGU

design to support plants with highly divergent morphological configurations.

C. Advanced Technology Research Areas - Research areas involving the development

of currently unavailable equipment, procedures, techniques, or materials. For

example, developing a nonphytotoxic structural plastic that does not create a

significant off-gassing problem and is useable with plant nutrient solutions.

Each research area entry foUows the same general format: (1) entry identification

number;, (2) suggested research area described; (3) parameters affected (electrical power,

mass, volume, cost) and/or other considerations identified.

o

129
This listing is intended to aid CELSS researchers to target their work. When evaluating

these suggested research areas, consider the inherent vehicle limitations. The limitations

of a space vehicle/station are primarily in electrical power and volume. Additional

considerations are resupply and initial launch masses. Cost presents a constraining

aspect of any design, thus affecting CELSS operations.

Research listings generated in any study are inherently incomplete. Readers are

encouraged to submit any other suggested research areas to the National Aeronautics

and Space Administration, Ames Research Center, Moffett Field, California, Attention:

Dr. R. MaeElroy.

?.1 BIOLOGICAL RESEARCH AREAS

. Determine plant growth dimensions in microgravity environment. Volume is a

function of plant size and yield per plant. Plant growth unit, lighting system, and

robotics are primarily affected. Thermal control and atmosphere control may be

impacted.

. Determine edible biomass production per unit area in microgravity environment for

edible plants. Volume is a function of the unit area yield and the volume of

equipment required to support each unit area. PGU and lighting are primarily

affected. Thermal control may be impacted.

. Develop biologically based inedible-to-edible biomass conversion systems. Volume

can be reduced when hi.mass utilization is improved. Energy requirements may be

reduced if a low energy, biologically based system performs the conversion process.

Food processing and waste regeneration systems are primarily affected. Lighting

system and thermal control are impacted.

. Determine artificial gravity requirement for plant development in microgravity.

Volume and power required per person will significantly increase if a centrifuge

deviee is needed. All CELSS systems are affeeted by artificial gravity

requirements.

130
e Evaluate aeroponic plant growth in mitt.gravity. Aeroponics may reduce mass and

volume while reducing plant handling problems. The feasibility of this technique in

microgravity is in question. Also, certain plants (i.e. potatoes) do not develop

properly with current aeroponic techniques.

e Examine orbital light/dark cycles effect on plant development. Lighting, power,

thermal, and volume requirements are impacted by any requirement to provide

Ulumination during orbital dark phase. Effects on yield, flower/seed development,

and maturation time are needed to support electrical power versus volume trades.

. Determine light levels necessary to maintain plant photoactivity while in orbital

dark phase. Lower light levels will reduce electrical power and fuel cell

requirements. Maintaining plant photoactive state during dark phase may support

high yields and rapid maturation compared with total darkness during the dark

phase.

. Lighting requirements for optimum plant growth in CELSS. The trade between high

energy use with high light levels in densely packed plants versus using lower energy

levels for lower light levels in moderately densely packed plants affects all aspects

of CELSS system design.

. Determine lighting characteristics to orient plant growth through phototropic

response in microgravity. Light provides the simplest system to induce plants to

grow in a predetermined direction. Alternative growth orientation procedures (e.g.,

electrical fields, chemical sprays, agitation, etc.) add complexity to the CELSS

design. Nonoriented plant growth may make CELSS a nonviable option using higher

plants.

10. Develop cultivars with maximum yield per kilowatt of light for desirable plant

species. Lighting consumes most CELSS module power and creates the largest heat

load. Improved edible return per watt decreases net power consumption and

corresponding power required to remove excess heat. Increased yields will also

reduce volume requirements provided maturation periods remain constant.

131
11.

12.

13.

14.

15.

Develop cultivars with optimum physical configuration for CELSS PGUs. A short,

dense growth plant with small root mass appears to be the optimum plant

configuration. Short plants reduce the light source height above the tray surface

decreasing the net plant growth unit volume. The denser the plant, the less growth

area required for a given number of plants. Short roots decrease tray depth, thus

reducing net PGU volume.

Develop cultivars that mature earlier while producing full edible biomass for desired

plant speeies. Earlier maturity dates increase pgu production per unit time.

Increased production decreases net volume requirements. Electrical power

decreases may also occur with fewer plant growth units required.

Identify aLl edible plant species that may be CELSS compatible. Investigate each

plant, evaluating its nutritional return and growth characteristics. All parameters

are affected by plant selection. For example, reduced power consumption may

result from selecting a plant with high edible biomass to power consumption ratio.

Volume reductions occur with plants that produce more biomass per unit volume.

Develop biologically based inedible-to-edible plant biomass conversion processes.

Volume and power savings are possible when the 40%, or more, of inedible biomass is

converted into edible matter. Inedible biomass require significant power and volume

to grow while in pursuit of edible biomass. The inedible biomass may contain as

much energy value as the edible portion. A simple biological system could be very

effective in recovering the inedible biomass, using little power and limited volume.

Develop a micromoles-to-lumen conversion table. Major difficulty exist in relating

micromoles (a biological measure) to lumens (an engineering measure). Engineering

design work requires conversion tables to determine the most effective

configurations.

16. Determine minimum photosynthetic maintenance light levels. Electrical power

requirements are reduced by using low light levels to hold plants in a photosynthetic

state during the orbital dark=side. Station mass and volume are reduced as additional

fuel cells and supporting solar panels are not required to maintain high artificial

light levels. Electrical power requirements are feasible when low-level dark phase

lighting is combined with a direct solar illumination device.

132
17. Determine strobe lighting effects on plant growth. Power, mass, and volume

reductions are possible when a single illumination source is used to briefly illuminate

each plant tray on a cyclic basis. Cycle time, illumination period, effects on plant

physiology, reproduction, and morphology need to be evaluated. Orbital dark-side

illumination parameters would benefit from a strobe system generating low net light

intensities.

18. Evaluate effects caused by absence of UV and/or IR light. Fiber optic cable and

direct solar light collector design will essentially eliminate the UV and IR

frequencies. Preliminary work by Dr. Kei Mori suggests major plant growth

improvements under these conditions. Volume and mass reductions can occur with

improved plant growth.

19. Develop techniques for stimulating directional plant growth (stems up and roots

down) in absence of gravity. PGU and lighting system designs are predicated on

Earth-like plant growth pattern. Any pattern variation may alter designs and their

related parametric values. Orientation phototrophism was assumed in this study.

Alternative approaches using chemicals, vibration, magnetic fields, or moisture

gradients should be examined.

20. Determine stem, leaf, and root temperatures for optimum edible biomass

production. Temperature requirements affect thermal control, mass, and volume by

modifying the CELSS and nutrient supply system design. Temperature requirements

will affect lighting to plant canopy distances in some configurations. This wiU

affect the PGU volume.

21.

22.

Determine transpiration rates for plants grown under high light intensity, high

humidity, high CO2 conditions of a CELSS system. ECLSS, thermal control and

nutrient supply systems design are dependent on plant transpiration rate. Higher

transpiration rates increase ECLSS efficiency, reducing power requirements. These

rates increase system volume and power with larger nutrient supply systems.

Integrate plant growth factors to produce the maximum edible biomass with the

least power. The factors are nutrient supply, CO2 levels, humidity, stem and root

temperatures, oxygen levels, air flow rates, light frequencies, and light intensity.

I33
23.

24.

25.

26.

27.

28.

29.

Plant dynamic interaction requires that all factors are integrated in determining

optimum CELSS growth conditions. Electrical power availability currently imposes

the greatest limitation on the CELSS. Configuring plant growth conditions for

minimal power provides the greatest benefit to CELSS concept.

Determine nutrient recycle period to support optimum plant growth. Power and

mass are affected by the recycle period. Frequent recycling requires added power

to the SCWO system. Nutrient makeup (chemical mass) increases with frequent

recycling. Growth versus nutrient age data are needed to conduct trades to

optimize the CELSS system.

Determine light intensity and frequency requirements for each day of plant growth.

Electrical power reductions are possible when light intensity and frequency are

tuned to plant requirements. For example, low light levels during early growth

stages may not affect final yield and could result in a more compact plant.

Determine germination conditions necessary in microgravity. Plant incubators,

small centrifuges, may be necessary for plant germination. Volume, power, and mass

increases would occur with this additional equipment. Human involvement would

increase to accommodate plant tending complexity.

Determine optimum plant density for aeroponic growth under microgravity

conditions. Yields are affected by plant density under identical conditions. CELSS

volume requirements are favored by high plant densities.

Breed or genetically engineer plants to eliminate adverse flavors, inhibitors, aromas,

and textures. Parametric values are not directly affected, but crew acceptance of

the product is.

Develop species for uniform seed, fruit, and tuber size and placement. Harvesting is

simplified by consistent plant characteristics. Simplified harvesting equipment saves

mass, volume, and power.

Determine a growth environment that supports increased oxygen production, CO2

removal, water transpiration, or food production. CELSS capability to act as an

134
ECLSSsystemdepends on ability to adjust for changing needs. System designs must

accommodate changes in primary CELSS mission.

30. Develop plant disease control and prevention techniques applicable to CELSS

conditions.

31. Determine plant response to rapid heating and cooling based on Space Station orbital

cycle.

32. Determine effect of CO2 levels in root aeration atmosphere.

7.2 ENGINEERING RESEARCH AREAS

1. Develop PGU design using corrosion-resistant and nonphytotoxic material while

maintaining a lightweight structure. The nutrient solution contains corrosive salts

that will destroy structures made from conventional metals. The use of highly

corrosion-resistant materials and plastics can reduce this problem. Accessibility,

maintainability, and resupply are directly affected by this problem. Using

lightweight plastics may reduce mass. Off-gassing plastics may require additional

ECLSS equipment and/or processes.

o Develop thermal control system with minimum energy and volume penalty to

remove lighting heat load. Lighting imparts multiple kilowatts of heat energy into

the CELSS module. Developing optimized air and fluid cooling combinations are

needed to reduce thermal control system power and volume requirements.

. Develop electrical power generation system using waste heat generated by lighting

system. Adapting thermal collectors may generate large temperature differentials

usable for electrical power generation. Power generation using thermister

principles are found in popular literature using a temperature difference of 250°F.

Electric power limitations strongly impact CELSS design. Any power-producing

system using waste heat can reduce power penalty, increased mass, volume, and

complexity penalty may be outweighed by the availability of increased power.

135
. Develop nutrient fluid handling system that ensures adequate supply, constant

monitoring, reconditioning and leakproof design in a ruler.gravity environment.

Continuous nutrient supply must be maintained to prevent crop failure. Nutrient

solution requires constant reconditioning for pH and essential minerals. The nutrient

solutionWs corrosive nature requires a high degree of containment to protect other

CELSS systems. All parameters are affected by nutrient system design.

Maintainability and automation are especiaLly impacted.

. Design a multiple-species plant harvesting unit. Balanced diet will require growth

and harvest of multiple plant species. Volume and automation are affected by the

number and variety of harvesting devices required to handle the different species.

Initial study evaluation suggests a multiple speeies device is more volume effective

and less difficult to automate than a series of single-crop harvesters.

. Design a plant processing unit that can process numerous varieties of edible foods.

Balanced diet will require consumption of multiple plant species. Volume and

automation are affected by the number and variety of food processing devices

required to handle the different food types. Initial study evaluation suggests a

multiple-food device is more volume effective and less difficult to automate than a

series of single-purpose harvesters.

. Design robotic gardener for plant tending, processing_ and equipment maintenance.

Automation requires an active device to perform gardening-related operations. A

mobile, intelligent device can concentrate these activities into minimum volume

while attaining maximum flexibility and capability. Rob, tie gardener may require

multiple, speeialized tools to support additional tasks such as harvesting_ planting

and tray sterilization.

. Design multiple speeies plant growth unit. Balaneed diet will require consumption of

multiple plant speeies. Volume, mass, power, and automation are affected by the

number and variety of plant growth devices required to grow different plant species.

Study evaluation suggests a multiple-species device is more effective and less

difficult to maintain.

136
.

10.

11.

12.

Design nutrient solution reconditioning system. Nutrient solution reconditioning

enhances plant growth and reduces the frequency of new nutrient makeup.

Reconditioning requires adjustment of pH minerals, trace elements, and the removal

of particulates and phytotoxic chemicals. Reconditioning the nutrient solution

reduces resupply requirements and power consumption by the waste regeneration

system used to dispose of used nutrient solution.

Design fiber optic cables for unbroken runs from solar collectors to terminal

illuminators. Every connector in fiber optic cables can reduce light levels 2 to 3 dB.

This significant loss can be prevented by using a continuous fiber, pile cable from

collector to plants. Continuous cable design reduces the number of collectors and

thus require fewer collectors. This reduces the mass launched to orbit and on-orbit

power requirements. Secondary maintenance and reliability advantages occur

because connectors are not required.

Design ruler.gravity adapted supercritieal water oxidation (SCWO) system. Current

SCWO size and equipment are for use in hazardous waste processing on Earth.

Redesign for space application should reduce volume, mass, and power requirements.

Redesign allows safety, maintenance, and reliability features specifically for Space

Station applications.

Design tray sterilization system using nontoxic process. Tray sterilization reduces

incidence of plant pathogen spread to new plants. Nontoxic techniques reduce

chances that a hazardous material wiLl be released into CELSS atmosphere. Tapping

into thermal system to use waste heat for steam generation provides one approach.

13. Design columnar luminares (light fixtures) for use with HID lamps. HID lamps are

the most efficient artificial light source available. Even distribution of HIDgenerated light to plants requires precisely designed luminares.

7.3 ADVANCED TECHNOLOGY RESEARCH AREAS

lo Develop fiber optic solar collector system to transmit solar illumination to plant

growth area. Solar light directly transmitted to plants can significantly reduce

power requirements. Direct illumination, using windows, possess many technical

137
.

.

o

5.

.

design problems that affect crew safety. Remote solar light collection and

transmission using fiber optic cables provides an alternative approach. Fiber opties

also permit precise light distribution and intensity control. Prototype systems exist

with 6096 transmission efficiency. Artificial lighting efficiency is 496 to 5% from

solar collector to plant light.

Develop fiber optie eable specifieally tuned to visible light. Currently available

fiber optics are tuned to higher communication frequencies. Transmission

improvements are possible with a frequency-tuned fiber optic cable. This cable

design can include components absorbent to IR and UV frequencies. This feature

will reduce critical lens alignment features of the "HIMINARI" solar collector

identified in this study.

Develop fiber optic cable connectors to reduce light-loss levels at cable switching

and connecting points. Current connectors impose 2- to 3-dB loss at each

connector. This loss requires more solar collectors to compensate for light loss.

More collectors increase mass, power, and maintenance requirements.

Develop SCNO system for use in mitt.gravity environment. SCNO prototypes

demonstrate very high efficiencies (99.99596) in organic waste oxidation. This

system could potentially handle all CELSS wastes while producing carbon dioxide,

potable water, and nitrogen gas. The system also recovers nutrient salts and oxides.

System adaptation will require development of (1)high pressure, low volume, fluid

pumps capable of processing corrosive fluids with high particulate loads, (2)highpressure fluid/gas and gas/gas separators; (3) waste pulverizer to reduce biomass to

very fine particulates. 4) high-pressure heat exchangers.

Develop a steam turbine generator to operate from SCWO system. This system can

operate exothermicaUy using 596 or more organic waste effluent. Reaction pressure

and temperature indicate that a turbine could operate from SCWO output. This

turbine could supply electrical power or compressed air to the Space Station.

Develop inedible-to-edible biomass conversion systems. Maximizing food value

return from each plant grown requires processing the inedible material into an

edible format. Power, mass, and volume requirements could be reduced with more

138
efficient biomass conversion. Biological and physiochemical biomass recovery

systems should be investigated.

. Develop artificial intelligence programs required by robotic gardener. Labor-hours

are saved using a robot to perform routine CELSS chores. Additional savings occur

with increased robotic artificial intelligence capability. Robot tasks include plant

health monitoring, seeding, harvesting, and plant tray manipulation.

. Develop high-efficiency, mercury-free lights for use in microgravity. Modern highefficiency lights (high pressure sodium, high-intensity discharge) use mercury as an

amalgam component. Highly toxic mercury is prohibited in the Space Station closed

environment. Amalgam pooling or positioning is critical to lamp operation.

Microgravity conditions may prevent pooling or positioning.

o Develop aeroponic plant growth systems that are operable in microgravity CELSS

conditions. Mass, volume, and power penalties are lowest in aeroponics systems.

Root oxygenation, nutrient transfer and temperature control are not well defined.

Tubers fail to develop normally in aeroponic systems.

10. Develop plant seeding tape for use on accordion growth trays. Automated seeding

requires positive seed control and placement in microgravity. Seed tape must

adhere to damp surfaces, retain plants in position, promote plant growth, aid in

germination, retain structural integrity for growth cycle, and prevent fluid escape

from plant growth tray. This tape is a necessary component of this studies selected

plant growth concept.

11. Develop pH and ion probes for monitoring nutrient solution.

in microgravity with low maintenance reliability,

concentrations. Probes must be ion specific.

These probes must work

and accuracy at low

139
This page intentionally left blank

140
8.0 CEL88 REQUIREMEI_I_

Growing higher vascular plants under microgravity conditions in a Space Station module

provides the background for CELSS requirements definition. The requirements were

identified and evaluated in 19 design areas.

8.1

8.2

8.3

8.4

8.5

8.6

8.7

8.8

8.9

8.10

8.11

8.12

8.13

8.14

8.15

8.16

8.17

8.18

8.19

Plant illumination.

Plant nutrient supply.

Water management.

Thermal control.

Automation.

Plant growth structure.

Atmosphere control system.

Tropism.

Phytotoxicity control.

Plant gas exchange.

Plant spacing.

Utility routing.

Accessibility and msintenanee.

Data coIIeetion and management.

Plant harvesting systems.

Food processing systems.

Waste regeneration.

Pathogen control.

Robotic systems.

CELSS operation scenarios establish the constraints within which requirements are

evaluated to define the best CELSS systems designs. For example, when electrical

power supply becomes more containing than growth cycle interval, lighting intensities

are reduced to accommodate available power while accepting longer growth cycles.

Certain parameters (power, mass, volume, and cost) are strongiy impacted by design

requirements. For example, electrical power varies with lighting and thermal requirements while volume responds mostly to PGU design. Therefore, while specific values are

stated in requirements, they should be considered engineering estimates that are

interdependent on other system designs.

141

PRI_-J_INU I_/_G E BLANK NOT FILt_ED
8.1 PLANT ILLUMINATION REQUIREMENTS

1. Provide 10 to 1000 micromol/m2/s illumination. This requirement covers lighting

needs of plants considered for CELSS.

. Heat generation in the vicinityof plants shallbe evenly distributed across the plant

canopy to avoid hot spots. Heat generated should not exceed the thermal dissipation

systemts rated capacity.

3. Equal lightintensityshallbe provided to allplants at the same growth stage.

4. Minimize lightsource electricalpower, volume, and mass demands.

8.2 PLANT NUTRIENT SUPPLY REQUIREMENTS

1. Plant nutrients shall be supplied by recycling Space Station wastes.

2. Automatic monitoring and replenishment of nutrients shall be provided.

3. Nutrient delivery to plants shall be via aeroponics (mist spray on root masses), or

hydroponics.

4. Exeess nutrient shall be removed from root vicinity.

5. Dissolved oxygen content of nutrient shall be three to nine ppm.

8.3 WATER MANAGEMENT REQUIREMENTS

Any available water sources may be used by CELSS. Potential water sources are1. SCWO condensate recovery from Space Station waste water including hygiene, wash,

and urine flush water, optionallyincluding fecal wastes.

2. Recycled, depleted nutrientsolution.

3. Condensate recovery of plant transpired water.

PRECED_O D_CE P.'LAk_'K NOT FILMED

142
4. Space Station potable water.

8.4 THERMAL CONTROL REQUIREMENTS

1. Thermal control shall be provided to maintain CELSS module temperatures of 20°C

to 30oc,

2. Thermal control shall be provided to maintain optimum plant canopy temperature

range for plants.

8.5 AUTOMATION REQUIREMENTS

1. CELSS routine operations shall be autonomous.

2. Human attention to CELSS shall be minimized by automation and robotics.

3. Equipment repair and maintenance shall be performed by crew members.

4. Repairs shallbe made at orbitalreplacement unit (ORU) level.

5. ALl function shall be provided by system-sensor monitoring, with fault identification

provided by CELSS computer.

8.6 PLANT GROWTH STRUCTURE REQUIREMENTS

1. Plants shall be securely fixed to their growth tray or growth device.

e A physical separation shall exist between plant root zone and aerial parts. This

separation shall prevent exchange of gases and fluids between roots and plant

atmospheric parts.

3. Roots shall be shielded from light.

4. Vertical air circulation from tray surface to plant canopy is required.

143
8.7 ATMOSPHERE CONTROL SYSTEM REQUIREMENTS

1. Plant canopy and root zone atmosphere compositions shall be maintained

independently.

2. Conditioned air circulation shall be used to maintain plant canopy humidity control.

8.8 EXTERNAL PLANT STIMULI REQUIREMENTS

1. Roots shall not be exposed to light.

2. Vibration levelsshallbe below plant response threshold.

3. Airflow shallflow from plant base to canopy to influence plant orientation.

4. Potential electromagnetic field effects on plant orientation shall be considered

when placing electrical utilities.

8.9 PHYTOTOXICITY CONTROL REQUIREMENTS

I. Nutrient makeup system and CELSS shall remove plant toxin accumulation. Some

toxins to be considered are ethylene, ozone, heavy metals, and fluorides.

8.10 PLANT GAS EXCHANGE REQUIREMENTS

1. Airflow shallbe used to maintain humidity, temperature, carbon dioxide,and oxygen

levels.

2. Air exchange rate shallrange from 0.42 to 1.1 m3/s.

8.U PLANT SPACING REQUIREMENTS

1. Plants shall be spaced to optimize volume usage and light distribution.

2. Transplantation shallnot be used to provide optimum plant spacing.

144
8.12 UTILITY ROUTINGREQUIREMENTS

1. Utilitiesshallbe availableto plant growth units to provide nutrientand airexchange

functions.

8.13 ACCESSIBIIJTY AND MAINTENANCE

1. Human access to plants shallbe provided.

2. Plant growth unitsshallbe designed for modular service.

3. Plant growth units shallnot be deactivated for partialsystem service.

4. CELSS shallconform to modular standards that apply to the Space Station.

8.14 DATA COLLECTION AND MANAGEMENT REQUIREMENTS

I. Sensors shallmonitor allCELSS operations.

2. CELSS system operations are implemented by the CELSS computer to reflect

changes inoperating conditions.

3. CELSS computer shallgenerate failurealerts to Space Station computer for failures

beyond the automated systems capabilityto modify or adjust.

8.15 PLANT HARVEST SYSTEMS REQUIREMENTS

1. Harvesting shallbe autonomous for normal operation.

2. Plant harvesting shall utilize robots.

3. Harvest equipment shah operate only on light-side orbit.

4. Harvest devices shall have the capability to process wheat, soybeans, and potatoes.

145
8.16 FOOD PROCESSING SYSTEMS REQUIREMENTS

1. Food processing shall be autonomous in normal operation.

2. Minimum food processing preparation shall be required for crop storage.

8.17 WASTE REGENERATION REQUIREMENTS

1. Waste management system shall be based on the SCWO.

2. Waste management system shall provide water, carbon dioxide, and salts for the

CELSS.

3. Space Station wastes, except fecal wastes, shall be processed by the SCWO system.

8.18 PATHOGEN CONTROL REQUIREMENTS

1. CELSS module shall provide sterilization of plant enclosures, harvest equipment, and

food processing equipment to prevent bacteria propagation.

2. Sterilization processes shall not pose any immediate or residual threat (e.g.,

chemical processes that leave a phytotoxic residue on trays).

8.19 ROBOTIC SYSTEMS REQUIREMENTS

1. CELSS robot performs routine plant growth and harvesting tasks.

2. CELSS robot shall interface with automated plant growth units, seeder, and harvest

equipment.

3. CELSS robot shall be limited in CELSS system repair and maintenance capability.

146
lo

e

o

.

e

.

e

.

.

10.

11.

12.

13.

BIBLIOGRAPHY

Akutsu, H. August 1981

A New High-Pressure Sodium Lamp with High Color Acceptability.

IES.

Journal of

Arno, Roger July 1984

NASA's Plans for Life Sciences Reasearch Facilitieson a Space Station.

of Automotive Engineers.

Society

Auslander, D.M. October 1983

Control and Modeling of a CELSS (Controlled Ecological Life Support System).

NASA, Washington D.C.

Auslander, D.M. 1984

Dynamic Control Considerations for Closed Life Support System.

Averner, M.M. 1984

Atmosphere Behavior in Gas Closed Mouse-Algal Systems:

Model. COSPAR Vol. XXV.

An Experimental and

Babcock, P.S. 1984

Dynamic Considerations for Control of Closed Life Support Systems.

Vol. XXV.

COSPAR.

Baker, J.D. December 1976

Hydroponic Vegetable Growing. Agric Gaz of New South Wales

Ball.u, E.V. 1982

Mineral Separation and Recycle in a Controlled Ecological Life Support System.

NASA-CR-166388. NCC 2-53. NASA, Washington D.C.

Berry, W. L. etal 1979

Further Development of the Use of Wastewater for Hydroponic Crop-Culture.

Alex J. Agri Research. Vol. 27 #1, pp 189-198.

Biological Life Support System: Bio-Regenerative Systems. 1968. NASA-SP-165.

NASA, Washington D.C.

Blankenship, P. D.

A Method for Automatic Cutoff of Laboratory Peanut Dryers Trans of Amer Soc

Agr Eng.

Boeing Aerospace Co. 1982

Regenerative Life Support Research/-Controlled Ecological Life Support System.

NAS2-11148. Washington D.C.

Boe, A.A. 1974

Hydroponic Culture of Plants, University of Idaho.

A-I
14.

15.

18.

17.

18.

19.

20.

21.

22.

23.

24.

25.

26.

27.

Boruch, M. 1981

The Automatic Control of Starch Drying Process.

28.

Boston, P.J. 1981

Low-Pressure Greenhouses and Plants for Amanned Research Station on Mars.

Brit Interplanetary Society Vol. 34.

Buck, J. A.

High Intensity Discharge Lamps for Plant Growth Applications ASAE Vol. 16.

Bugbee, B.G. August 1985

An Evaluation of MES (2(N-Morpholino) Ethanesulfonic Acid) and Amberlite IRC50 as Buffers. J. Plant Nutrition. 8(7), 567-583 (1985)

Buley, N. 1984

Innovations in Greenhouse Growing Challenge

Nurseryman. Vol. 159.

Conventional Methods American

Carpenter, W.J. 1974

High Intensity Lighting in the Greenhouse, Michigan State University.

Cheng, Y.W. 1978

The Design of Simple Automatic Irrigation Systems for Small Scale Hydroponic

Culture. Singapore JJ. PRI IND. 6(1):52-62

Yutaka, C. 1982

Delayed Light Emission as a Means of Automatic Sorting of Tomatoes.

the Fac of Agri.

Journal of

Cohen, S. 1983

Ballasting the Miniture Metal Halide Lamp. Journal ofIES.

Davtyan, G.S. 1980

Classification of Hydroponic Methods of Plant Production.

Soiless Culture.

Proc 5th Inter Cong

Dufour, P.A. July 1985

Publications of the NASA CELSS Program.

NASA, Washington D.C.

NASA HQ. CR-3911-N. NASW-3165.

Filka, P. October 1981

Process Automation as a Part of Integrated Project Engineering of Food Plants.

North-Holland Publ. Co.

Fukuda, H. 1984

Microbial Production of C3 and C4

Agric. Biol. Chem 48(8).

Hydrocarbons Under Aerobic Conditions.

Gausman, H.W. June 1982

Optical Parameters of Leaves of Seven Weed Species. USDA-ARS.

Gray, V.H. August 1971

Rotating Vivarium Concept for Earth-Like

Medicine.

Habitation in Space Aerospaee

A-2
29.

30.

31.

32.

33.

34.

35.

36.

37.

38.

39.

40.

41.

42.

Hammer, E.E. July 1983

Fluorescent System Performance of F40T12 and Smaller Lamp Diameters.

Journal of IES.

Hoff, J.E. 1982

Nutritional and Cultural Aspects of Plant Species Selection for a Controlled

Biological Life Support System. NSG-2401/2404.

Hoshizaki, T.

Generic Waste Management Requirements

Support System. NASA, Washington D.C.

for a Controlled Ecological Life

Howe, J.M. October 1981

Plant Diversity to Support Humans in a

NASA, Washington D.C. NSG-2401

CELSS Ground-Based Demonstrator.

Huang, Barney K. October 1984

Systems Engineering in Precision Automatic Transplanting Agric Mech Asia, Afr,

L.A.

Tadashi, Ito March 1980

Effieient Management in Greenhouse Horticulture ASPAC.

Jensen, Merle H. April 1980

Tomorrow's Agriculutre Today American Vegetable Grower.

Johnson, E.J. March 1982

Genetic Engineering Possibilitiesfor CELSS: A Bibliograph and Summary of

Techniques. NASA, Washington D.C. NASA-CR-168306

Jokinen, K. February 1983

Automation in a Vegetable Oil Extraction Plant.

Society.

Journal American Oil Chemical

Kamarei, A.R. July 1985

Potential for Utilization of Algal Biomass for Components of the Diet in CELSS.

ICES San Francisco. SAE 851388

Kitson, J.A. March 1978

Metamorphosis of Fruit Trimmings Creates Sweet Alternative to Dried Fruit.

Food Product Develpment.

Kolesnikov, Y. 1977

Plants in the Gravitational World

NASA, Washington D.C. NASA TTF-17528

Konstantinov, B.P. July 1974

Inhabited Space. NASA Teeh Translation. NASA TTF820. Washington D.C.

Krauss, R.W. 1979

Closed Ecology in Space from a Bio-engineering

Vol. XVII.

Perspective. COSPAR.

A-3
43.

44.

45.

46.

47.

48.

49.

50.

51.

52.

53.

54.

55.

56.

57.

58.

Kreutz, D. March 1980

Tucson is Growing the Food of the Future. Tucson Citizen Mag.

Lagsdon, G. 1977

Small Scale Grain Raising. Rodale Press Inc.

Lamberts, D. 1981

Hydroponics in Horticulture. Catholic University of Leuven.

Larsen, J.E. 1982

Growers Problems with Hydroponics. Journal of Plant Nutrition, #5 (8)

Lawhon, J.T. March 1981

Soy Protein Ingredients Prepared by New Processes--Aqueous Processing.

American Oil Chemical Society.

Journal

Liener, I.E. March 1981

Factors Affecting the Nutritional Quality of Soya Products.

Chemical Society.

Journal American Oil

Lonisko, B.

Wet-Oxidation as a Waste Treatment Method in Closed Systems.

Lusas, E.W. March 1979

Food Uses of Peanut Protein. Journal American Oil Chemical Society, Vol. 56.

MaeElroy, R.D. 1978

Space Ecosynthesis: An Approach to the Design of Closed Ecosystems for Use in

Space. NASA, Washington D.C. NASA-TM-78491

Malachowski, M.J. 1980

Cellulose Conversion Handbook. C.E.I. Cellulose Conversion

Mason, R.M. 1979

Guiding the Development of a Controlled Ecological Life Support System.

Washington D.C. NASA CP-162452

NASA,

Meissner, H. P 1980

Recycling Plant, Human and Animal Wastes

Ecological Life Support System.

to Plant Nutrients in a Closed

Mitchell, C. A.

Photosynthetic Productivity and Vibration/Accelerational Stress Considerations

for CELSS. The Physiologist, VoL 27.

Walter, L. Jr. November 1981

An Automatically-Fed Bandoleer Transplanter. American Soe Agricul Engr.

ModeU, M. July 1977

Sustaining Life in a Space Colony. Technology Review.

Modell, M. April 1982

Treatment of CELS8 and PCELSS Waste to Produce Nutrients for Plant Growth.

ASME. 81-ENAS-19.

A-4
59.

60.

61.

82.

63.

64.

85.

68.

67.

68.

69.

70.

71.

72.

Moore, B. 1982

Controlled Ecological Life Support System (CELSS):

Washington D.C. CP-2233

Biological Problems. NASA,

Morgan, P.W. 1979

A Preliminary Research Plan for Development of a Photosynthetic Link in a

CELSS. NASA, Washington D.C. NASA 9-15873

Mori, K. May 1985

Photoautotrophic Bioreactor Using Visible Solar Rays

Lenses. 7th Stop. Biotec. Fuels & Chemicals

Condensed by Frensnel

Mori, K. 1985

Microalgal Cultivation for Oxygen Production Using Filtered Sunlight Transmitted

by Fiber Optics.

Mpelkas, C.C. October 1984

Alfalfa Sprouts Grown Under Sylvania Lamps

Groceries. Sylvania Division of GTE.

Supply Chicago Salad Bars and

Mpelkas, C.C. July 1984

Sylvania Lamps are Playing an Important Role in Helping to Reclaim the Blighted

Landscape. Sylvania Division of GTE.

Nir, I. May 1982

Growing Plants in Aeroponics Growth System. Inter Soc Hort Science.

Nit, I. 1975.

Growning Plants in Aeroponics Growth System.

pp 435-448.

Acta Horticulture, Vol. 126,

Nitta, K. July 1985

CELSS Experiment Model and Design Concept of Gas Recycle System.

851393. ICES San Francisco.

SAE

Nowosielski, O. May 1975

The Use of Sphagnum Peat and Brown Coals for Growing Plants in Hydroponic

Containers. ACTA Horticultura; 50:165-171.

O'Lear_, J.W. 1975

High Humidity Overcomes Lethal Levels of Salinity in Hydroponically Grown SaltSolution. Plant and Soil; #42.

O'Neill, G.K. 1979

Space Resources and Space Settlements. NASA, Washington D.C. NASA-SP 428

Ohya, H. July 1984

Survey of CELSS Concepts and Preliminary Research in Japan. XXV COSPAR.

Onisko, B.L. 1980

Wet Oxidation as a Waste Treatment

Washington D.C.

Method in Closed Systems. NASA,

A-$
73.

74.

75.

76.

77.

78.

79.

80.

81.

82.

83.

84.

85.

86.

87.

88.

Paschold, H. June 1980

Sensors - The Prerequisite for Automation in the Food Industry.

Industry.

Chemistry and

Peterson, C.

Overview of Automatic Seeding Equipment. Ohio State University.

Peterson, R. February 1984

Biological Food Production from Chemically Reduced CO 2 Products.

Pasadena, CA.

NASA 2PL,

Pierce, J.H. 1977

Greenhouse Grow How. R. R. Donnelley & Son

Pirie, N. 1980

Space Victualling. Endeavour, Vol. 4 #2

Raper, C. July 1985

Simulation Model for Plant Growth

SAE 851390, ICES, San Francisco

in Controlled Environment Systems.

Richardson, F.I. 1980

Nutrient Film Technique. Agri. in N. Ireland, 55,11.

Richards, J.R. 1981

A Closed Ecosystem for Space Colonies. J. Brit. Interplanetary Society; Vol. 34.

Robinson, J. 1979

Think Hydroponics. GC and HTJ; 182

Salisbury, F.B. 1984

Achieving Maximum Plant Yield in a Weightless, Bioregenerative System for a

Space Based CELSS. The Physiologist; Vol. 27.

Sargent, E. February 1984

Advantages of Automatic Seeding. FloristsReview; Vol. 169.

Schippers, P.A. June 1980

Hydroponic Lettuce: The Latest. American Vegetable Grower.

Schubert, F.H. July 1984

Advanced Regenerative Environmental Control and Life Support Systems: Air and

Water. COSPAR; Vol. XXV.

Schwarz, M. July 1966

Simplified Analysis of Hydroponic Solutions. National Count Res & Dev.

Schwarz, M. 1979

Irrigation with Brackish Water in Soiless Culture. Acta Horticulturae; #89.

Sheppard, C.R. October 1981

Greenhouses without Windows: Subterranean Forestry for Surface Reflamation.

Minning Cong. Journal.

A-6
89.

90.

91.

92.

93.

94.

95.

96.

97.

98.

99.

100.

101.

102.

103.

Skoog, A. I July 1984

BLSS: A Contribution to Future Life Support. COSPAR; Vol. XXV.

Smernoff, D.T. July 1985

Controlled Ecological Life Support System CELSS "85 Workshop NASA AMES.

Moffett Field,CA.

Spurlock, J.M. April 1980

Comparison of Closure Scenarios for Controlled Ecological Life Support Systems.

NASA, Washington D.C. NASW-3196.

Spurlock, J.M. 1977

Review of Technology Developments Relevant to Clo_ed Ecological Systems for

Manned Space Flight. NASA, Washington D.C. NASW 2981

Spurlock, J. M. eta/ 1979

Technology Requirements for NonterrestrialEcosystems. COSPAR; Vol. XVII.

Steinkraus,D.H. April 1978

Tempeh-An A?sianExample of Appropriate/Intermediate Food Technology.

Technology.

Food

Stokes, B.O. 1981

Unconventional Processes for Food Regeneration in Space:

81-ENAS-35

An Overview ASME;

Sylvania Staff. 1985

Metalarc and Super Metalarc Lamps. Sylvania Div of GTE

Taub, F.B. October 1963

Some Ecological Aspects of Space Biology.

Vol. 25, No. 6.

American Biology Teacher.

Taub, F.B. 1974

Closed Ecological Systems. Rev Ecology and Systematics; Vol. 5.

Tibbitts, T. W. eta/ 1979

Controlled Environmental Guide for Plant Research.

Wk Group.

Proc. Controlled Environ.

Tofu, A Far East Import, Offers Potential as Meat, Fish, Cheese Substitute.

May 1979. Food Product Development.

Wallace, A. 1978

Reclaimed Sewage Water:. A Hydroponic Growth Medium for Plants Resource

Recov & Conser.

WaLlace, A. 1979

Wastewater as a Hydroponic Growth Medium for Greenhouse Crop Culture.

J. Agric Res; 27(1)181-188.

Alex

Wallace, A.

Wastewater as a Source of Nutrients and Water for Hydroponic Crop Production in

Greenhouses. Hardwood Academic Pub.

A-7
104.

105.

106.

107.

108.

109.

110.

111.

112.

113.

114.

Wheeler, R.M. November 1984

Controlled Ecological Life Support System - Higher Plant Flight Experiments.

NASA, Washington D. C.

Winfield, B.A. 1981

Techniques of Iron Addition to a Sewage Effluent Based Nutrient Film System.

Journal of Plant Nutrition; 4(3).

Wyner, E.F. July 1984

Increased Red Output, Low Color Temperature Metal Halide Lamps.

IES

Journal of

Zobel, R.W. 1976

Method for Growing Plants Aeroponically. Plant Physiol; Vol. 57.

Berry, W.L. 1979

Further Development of the Use of Wastewater for Hydroponic Crop Culture.

Alex J. Agrie. Res; Vol. #27(1).

Bone, D.

Sugar Form Sewage. Brit Sugar Beet Review.

Conroy, P.F. March 1981

The Greening of the Desert. Quest.

Nelson, P.V. 1978

Greenhouse Operation and Management. Reston Publishers.

Payne, L.F. 1972

Recording Water Use by Means of Digital Equipment.

# 1 pp 83-84.

Agronomy Journal; Vol. 64

Resh, H.M. 1978

Hydroponic Food Production. Woodbridge Press.

StangheUini, M.E. October 1971

Damping-off of Tomato Seedlings in Commercial Hydronie Culture Prog. Agr.

Arizona; #23 (5)

A-8
_t

MICROMOLE PER SECOND PER SQUARE METER MEASUREMENTS

(Micromole/S/M 2)

To obtain micromole S-1 M-2 measurements multiply footcandle readings by the given

constants depending on the lamp type.

LAMP TYPE

Multiply FC by the given constant

for micromole S1 M-2 conversions**

400-700 nm 400-850 nm

Daylight (Sun and Sky)*

Blue sky only*

High Pressure Sodium

Metal Halide

Mercury Deluxe

Warm White Fluorescent

Cool White Fluorescent

Standard Gro-Lux Fluorescent

Wide Spectrom Gro-Lux Fluorescent

Incandescant

Low Pressure Sodium

0.20 0.30

0.21 0.26

0.13 0.20

0.15 0.18

0.13 0.14

0.14 0.15

0.15 0.15

0.33 0.35

0.20 0.23

0.22 0.54

0.10 0.12

*Typical of clear summer sky at 40 ° latitude

**These are generic values based on Thimijan and Heins (Horticulture Science, 18:818, 1983),

and McCree (Agricultural Meteorol, I0:443, 1972)

Christos C. Mpelkas

Photobiologist

Manager -

Photobiological Applications

B-I
• o

_1o_ _._.

==

o=_0_._. _

0

0

0

0

0

B-2
TABLE OF REFERENCE VALUES

Ref Topic Value Source .

Light Level 0-20 days wheat

Max usable light level

Natural Daylight light level

Leaf crop light requirement

Fluorescent-canopy spacing

HID canopy spacing

S. Station ambient CO 2

Module outside diameter

Module inside diameter

HID heat load w/ballast

1000 watts

400 watts

I00 watts

Micromoles/m2/sec to

foot-candle ratio (approx)

Ballast load as % bulb rating

HP Sodium light emitter size

Solar Light Constant

Solar Ray collector efficiency

Solar Ray collector pointing

Minimum optical cable temp

Lumens from 3.17m 2 solar ray

CoUector @ 50% efficiency

in orbit.

500mm/m2/sec

1000 m mlm21sec

10000 ftcndl

1000+ ftcndl

6 inches rain

12 inches rain

2000ppm

14ft

13ft 8in

3750 btu/hr

1600 btu/hr

400 btu/hr

1:10

10-20%

80ram x 9.Smm

1353 watts/m 2

60%

.02 degree

-20 ° degree

500,000 lumens

Bugbee 4/9/85

Bugbee 4/9/85

F. Buck @ GE

F. Buck @ GE

F. Buck @ GE

F. Buck _ GE

R. Ames ECLSS

SS ref Config

SS ref Config

Sylvania Co.

Sylvania Co.

Sylvania Co.

R. MacElroy 3/15/85

GE Seattle Staff

GE Seattle Staff

Dr. K. Mori

Dr. K. Mori

Dr. K. Mori

Dr. K. Mori

Dr. K. Mori

B-3
TABLE OF REFERENCEVALUES(Continued

Ref Topic Value Source

Grams oxygen/liter std atmo

Average % biomass containing

hydrogen, carbon & nitrogen

Average % carbon & hydrogen

in carbon, hydrogen nitrogen

Potatoes transpiration G 400ram

20 ° 325ppm CO 2

Potatoes light requirement

Potato light cycle

Potato growth temp

Potato growth humidity

Potato plant dimensions

Potato plant spacing

Potato maturity early

nominal

Potato canopy temperature

Variance from air temp.

Potato toxins

Potato biomass (total)

(edible)

Potato harvest index

1.429

89%

75%

5.4 L/m2/d

400-700 mm

m2/see

24 hr light

20 ° Cent

70%

24" high x 20"

diameter

.2m2/plant

56 days

105-140 days

2 ° Cent

Selenium

38 g/m2/d

20.7 i_/m2/d

.53

CRC handbook

Fundamental Chem

Fundamental Chem

Tibbits 12/21/84

Tibbits 12121/84

Tibbits 12/21/84

Tibbits 12/21/84

Tibbits 12/21/84

Tibbits 12/21/84

Tibbits 12/21/84

Tibbits 12/21/84

Tibbits 12/21/84

Tlbbits 12121/84

Tibbits 12121184

Tlbbits 12121184

Tibbits 12/21/84

Tibbits 12/21/84

B-4
TABLE OF REFERENCE VALUES (Continued

Ref Topic Value Source

Soybeans

Illumination level(max)

(rain)

Light cycle (light)

(dark)

Air temperature (range)

Air temperature (nominal)

Root temperature (nominal)

CO 2 levels

Canopy temperature variance

from air temp

Tray depth

Maturity (early)

(nominal)

Germination time (dark)

Plant height (30° C.)

(18oc.)

700 mm/m2/see

350 mm/m2/sec

9-12 hr/24/hr

12-15 hH24hr

22-28 ° Cent

26 ° Cent

24 ° Cent

400-600 ppm

4 ° Cent

30-35 em

90-120 days

I00 days

48 hrs

1.8 meters

0.5 meters

Dr. D. Raper

Dr. D. Raper

Dr. D. Raper

Dr. D. Raper

Dr. D. Raper

Dr. D. Raper

Dr. D. Raper

Dr. D. Raper

Dr. D. Raper

Dr. D. Raper

Dr. D. Raper

Dr. D. Raper

Dr. D. Raper

Dr. D. Raper

Dr. D. Raper

Dr. D. Raper

B-S
APPENDIX C:

CELSS Documents Published as NASA Reports

C

,

.

,

.

.

.

.

Johnson, Emmett J.: Genetic Engineering Possibilities for CELSS: A Bibliography and

Summary of Techniques. NASA CR-166306, March 1982.

Hornberger, G.M. and Rastetter. E.B.: Sensitivity Analysis as an Aid in Modelling and

Control of (Poorly-Defined) Ecological Systems. NASA CR-166308, March 1982.

Tibbitts, T.W. and Alford. D.K.: Controlled Ecological life Support System: Use of Higher

Plants. NASA CP-2231, May 1982.

Mason, R.M. and Carden, J.L.: Controlled Ecological Life Support System: Research and

Development Guidelines. NASA CP-2232, May 1982.

Moore, B. and MacEIroy, R.D.: Controlled Ecological Life Support System: Biological Problems. NASA CP-2233. May 1982.

Aroeste, H.: Application of Guided Inquiry System Technique (GIST) to Controlled Ecological Life Support Systems (CELSS). NASA CR-166312, January 1982.

Mason, R.M.: CELSS Scenario Analysis: Breakeven Calculation. NASA CR-166319, April

1980.

8. Hoff, J.E., Howe, J.M. and Mitchell. C.A.: Nutritional and Cultural Aspects of Plant Species

Selection for a Controlled Ecological Life Support System. NASA CR-166324, March 1982.

g. Averner, M.: An Approach to the Mathematical Modelling of a Controlled Ecological Life

Support System. NASA CR-166331, August 1981.

10. Maguire, B.: Literature Review of Human Carried Microbes' Interaction with Plants. NASA

CR-166330, August 1980.

11. Howe, J.M. and Hoff, J.E.: Plant Diversity to Support Humans in a CELSS Ground-Based

Demonstrator. NASA CR-166357, June 1982.

12. Young. G.: A Design Methodology for Nonlinear Systems Containing Parameter Uncertainty: Application to Nonlinear Controller Design. NASA CR-166358, May 1982.

13. Karel, M.: Evaluation of Engineering Foods for Controlled Ecological Life Support Systems

(CELSS). NASA CR-166359, June 1982.

14. Stahr, J.D., Auslander, D.M., Spear, R.C. and Young, G.E.: An Approach to the Preliminary Evaluation of Closed-Ecological Life Support System (CELSS) Scenarios and Control

Strategies. NASA CR-166368, July 1982.

15. Radmer. R., Ollinger, O., Venables, A. and Fernandez, E.: Algal Culture Studies Related

to a Closed Ecological Life Support System (CELSS). NASA CR-166375, July 1982.

16. Auslander, D.M.. Spear, R.C. and Young, G.E.: Application of Control Theory to Dynamic

Systems Simulation. NASA CR-166383, August 1982.

c-1
17. Fong, F. and Funkhouser, E.A.: Air Pollutant Production by Algal Cell Cultures. NASA

CR-166384, August 1982.

18. Ballou, E. V.: Mineral Separation and Recycle in a Controlled Ecological Life Support

System (CELSS). NASA CR-166388, March 1982.

lg. Moore, B., III, Wharton, R. A., Jr., and MacEIroy. R.D.: Controlled Ecological Life Support

System: First Principal Investigators Meeting. NASA CP-2247, December 1982.

20. Carden, J. L. and Browner, R.: Preparation and Analysis of Standardized Waste Samples

for Controlled Ecological Life Support Systems (CELSS). NASA CR-166392, August 1982.

21. Huffaker, R. C., Rains, D. W. and Qualset, C. O.: Utilization of Urea, Ammonia. Nitrite.

and Nitrate by Crop Plants in a Controlled Ecological Life Support System (CELSS),

NASA-CR 166417, October 1982.

22. Gustan, E. and Vinopal, T.: Controlled Ecological Life Support System: Transportation

Analysis. NASA CR-166420, November 1982.

23. Raper, C. David, Jr.: Plant Growth in Controlled Environments in Response to Characteristics of Nutrient Solutions. NASA CR-166431, November 1982.

24. Wydeven, T.: Composition and Analysis of a Model Waste for a CELSS. NASA Technical

Memorandum 84368, September 1983.

25. Averner, M., Karel, M., and Radmer, R.: Problems Associated with the use of Algae in

Bioregenerative Life Support Systems. NASA CR-166615, November 1984.

26. Radmer, R., Behrens, P., Fernandez, E., Ollinger, O., Howell, C., Venables. A., Huggins. D.

and Gladue, R.: Algal Culture Studies Related to a Closed Ecological Life Support System

(CELSS). NASA CR-177322, October 1984.

27. Wheeler, R. and Tibbitts, T.: Controlled Ecological Life Support System: Higher Plant

Flight Experiments. NASA CR-177323, November 1984.

28. Auslander, D., Spear, R., Babcock, P. and Nadel, M.: Control and Modeling of a CELSS

(Controlled Ecological Life Support System). NASA CR-177324, November 1984.

29. Karel, M. and Kamarei, A.R.: Feasibility of Producing a Range of Food Products from a

Limited Range of Undifferentiated Major Food Components. NASA CR-177329. April 1984.

30. MacEIroy. R.D.. Smernoff, D.T., and Klein, H.: Life Support Systems in Space Travel.

(Topical Session of XXVth COSPAR meeting, Graz, Austria) NASA CP-2378, May 1985.

31. MacEIroy, R.D., Martello, N.V., Smernoff, D.T.: Controlled Ecological Life Support Systems: CELSS '85 Workshop, NASA TM-88215, January 1986.

32. Tibbitts, T.W.:Controlled Environment Life Support System: Calcium-Related Leaf InJuries

on Plants. NASA CR-177399, March 1986.

33. Tibbitts. T.W., Wheeler, R.M.: Controlled Environment Life Support System: Growth

Studies with Potatoes. NASA CR-177400, March 1986.

(3-2
34. Babcock,P.S.: Nonlinear System Controller Design Based on Domain of Attraction: An

Application to CELSS Analysis and Control, NASA CR-177401, March 1986.

35. Smernoff, D.T.: Atmosphere Stabilization and Element Recycle in an Experimental MouseAlgal System. NASA CR-177402, March 1986.

C-3
1. Report No, 2. Government Accession No, 3. Recipient's Catalog No.

NASA CR- 177421

4. Title end Subtitle

Controlled Ecological Life Support Systems

Conceptual Design Option Study

(CELSS)

7. Author(s)

Melvin Oleson and Richard L. Olson

9. Performing Organi_tion Name and Address

Boeing Aerospace Company

Seattle, WA 98124

12. Sponsorin9 Agency Name and Addr_s

National Aeronautics and Space Administration

Washinston, D.C. 24056

5. Report Date

June 198

6, Performing Organization Code

SLX

8. Performing Organization Report No.

36

10. Work Unit No.

T6934

11. Contract or Grant No.

NAS2-118 06

13. Type of Report and Period Covered

Contractor Report

14. Sponsoring Agency Code

199-61-12

15. Supplementary Notes

Point of Contact :

Robert D. MacElroy, NASA Ames Research Center

MS 239-4, Moffett Field, CA 94035

415-694-5573 or FTS 8-464-5573

16. Abstract

This document contains the results of a study designed to explore options for the

development of a Controlled Ecological Life Support System (CELSS) for a future Space

Station. In addition, study results will benefit the design of other facilities such as the

Life Sciences Research Facility, a Ground-Based CELSS demonstrator and will be useful

in planning longer range missions such as a lunar base or manned Mars mission. The primary study objectives were to develop weight and cost estimates for one CELSS module

selected from a set of preliminary plant growth unit (PGU) design options. Eleven Space

Station CELSS module conceptual PGU designs were reviewed, components and subsystems identified and a sensitivity analysis of CELSS subsystems performed. Areas were

insufficient data is available were identified and divided into the categories of biological

research, engineering research and technology development. Topics which received significant attention in this report were lighting systems for the PGU, the use of automation

within the CELSS system and the electrical power requirements of the system. Other areas

examined included plant harvesting and processing, crop mix analysis, air circulation and

atmosphere contaminant flow subsystems, thermal control considerations, utility routing

including accessibility and maintenance and nutrient subsystem design. Extensive analysis

of the waste processing subsystem was done and included as an Appendix to this study.

That Appendix is published as a separate NASA Contractor Report.

17. Key Words (Suggested by Author(s})

CELSS, Plant growth systems, lighting

systems, Space Station modules,

automation,sensitivity analysis

18. Distribution Statement

Unclassified - Unlimited

STAR Category 54

19, Security Classif. (of this report)

Unclassif led

20. Secu:ity Classif. (of this page)

Unclassified

21. No. of Pages

]71

"For sale by the Nationat Technical Information Service, Sprin(jfield, Virginia 22161

22. Price"

Ib