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Produced by the NASA Center for Aerospace Information (CASI)
February 1984

Boeing Aerospace Company

D1 Q-27935-1 

[ f

SPACE STATION SYSTEMS TECHNOLOGY STUDY

Final Report

VOLUMEI

EXECUTIVE SUMMARY

D180-27935-1

C,

Conducted for NASA Marshall Space Flight Center

Under Contract Number NAS8-34893

Spectra Research Systems

(NASA-CR- 1'101u) SPACE STATICN SYSTEMS N84-22614

TECHNOLOGY STUDY. VOLUtE 1: EX:.CUTIVE

SUMMARY Final Feport (Eoeinq Aerospace Co.,

Seattle, Wasti.) 111 p HC AC6/MF A01 Unclas

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D180-27935-1

FOREWORD

The Space Station Systems Technology Study (Contract MASS-34893) was initiated in

June 1983 and to be completed in April 1984. The study was conducted for the National

Aeronautics and Space Administration, Marshall Space Flight Center, by the Boeing

Aerospace Company with Spectra Research Systems as a subcontractor. The study final

report is documented in three volumes.

D180-27935-1 Vol. I Executive Summary

D180-27935-2 Vol. II Trade Study and Technology Selection Technical

Report

DI80-27935-3 Vol. III Technology Advancement Program Plan

Mr. Robert F. Nixon was the Contracting Officers Representative and Study Technical

Manager for the Marshall Space Flight Center. Dr. Richard L. Olson was the Boeing

study manager with Mr. Paul Meyer as the technical leader and Mr. Rodney Bradford

managed the Spectra Research Systems effort. A listing of the key study team members

follows.

i
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D180-27935-1

KEY TEAM MEMBERS

Subject MSFC-Management Team Contractor Team

Study Manager R. F. Nixon R. L. Olson

Technology Category

Thermal Control G. E. Comer T. J. Kramer

R. L. Shannon

Data Systems H. E. Brown B. A. Andrews

T. A. Nicolino

Attitude Control P. D. Nacaise M. H. Bantell

Integration of H. E. Brown D. P Meyer

Automated Systems

Test Planning (SRS) R. Bradford,

Management

J. Cody

S. Montgomery

ii .
D.180--27935-1

TABLE OF CONTENTS

VOLUME I

Page

1.0 INTRODUCTION 1

1.1 Technology Selections and Rationale 2

2.0 TECHNICAL SUMMARIES 7

2.1 Introduction 7

2.2 Attitude Control S

2.3 Data Management 23

2.4 Long Lifetime Thermal Management 44

2.5 Integration of Automated Housekeeping 67
DISO-27935-1

4A

LIST OF FIGURES

No. Page

1.0-1 Study Plan Flow Diagram 3

2.2-1 Space Station Balanced Array Concept with Astromast 5olar

Array Deployment 11

2.2-2 Buildup Sequence Defining Configuration for Control/Structural

Analysis 12

2.2-3 Software Architecture Technical Approach for Dynamic Simulation

Analysis 13

2.2-4 Disturbance Model for Crew Activity 14

2.2-5 Generic Block Diagram of an Attitude Regulator for a Flexible fil

Structure 15

2.2-6 Measurements of Flexible Elements for Reference in Time Histories 15

2.2-7 Closed Loop Response to 1000 N-M-Sec Impulse Doublet in

Pitch for Configuration 1 16

2.2-8 Closed Loop Response to 1000 N-M-Sec Impulse Doublet in

Roll for Configuration 1 16

2.2-9 Closed Loop Response to 1000 N-M-Sec Impulse Doublet in

Pitch and Roll for Configuration 2 17

2.2-10 Impulse Response (arc-sec) of Configuration I to Docking Load

of 2500 Newtons at Body Station 1201 19

2.2-11 Orbiter Docking to Space Station Showing Preferred Configuration 20

2.3-1 Data Processing, Storage, and Communication Requirements 24

2.3-2 Fiber-Optic Backbone Network 26

2.3-3 Multi-Star vs Graph Topologies 27

2.3-4 Transmitter Block Diagram 29

2.3-5 Receiver Block Diagram 30

2.3-6 NIU: Internal Organization 32

2.3-7 Network Operating System Example 34

2.3-8 DMS Closed Loop Simulation 35

2.3-9 Criticality of Technologies 37

2.3-10 Schedule for Data Management System Simulation Program 38

2.3-11 Schedule for Network Interface Unit Terhnology Advancement Program 46

2.3-12 Schedule for Network Operating System Technology Advancement

Program 42

2.4-1 Heat Transport System 47

iv
DISO-27935-1

LIST OF FIGURES (CONTINUED)

No. Page

2.4-2 High Temp. Two-Phase Ammonia Bus with Two-Phase Water Loops 50

2.4-3 Effect of Two-Phase Water Heat Transport System on High

Temperature Bus 51

2.4-4 Low Temp. Two-Phase Ammonia Bus with Two-Phase Water Loops 52

2.4-5 Effect of Two-Phase Water Heat Transport System on Low

Temperature Bus 53

2.4-6 Pumped Liquid Freon-11 System Schematic 56

2.4-7 Schedule for Two-Phased Thermal Management System Pump

Advancement Program 60

2.4-8 Schedule for Heat Exchanger Technology Advancement Program 62

2.4-9 Schedule for Two-Phased Water Interior Loop Technology Advancement

Program 65

2.5-1 Interactions Which Affect Housekeeping Functions 80

2.5-2 Interfaces Between an Integrating Controller and Automated

Housekeeping Subsystem 81

2.5-3 Functional Block Diagram for Electrical Power Load Management

by an Integrating Controller 83

2.5-4 Functional Block Diagram for Materials Transfer Management

by an Integrating Controller 84

2.5-5 Functional Block Diagram for Inter-Subsystem Failure Isolation

using Integrating Controller 85

2.5-6 Functional Block Diagram for Inter-Subsystem Redundant Path

Selection by an Integrating Controller 86

2.5-7 Functional Block Diagram for Maintenance Schedule Management

by an Integrating Controller 87

2.5-8 Functional Block Diagram for Startup Integration by an

Integrating Controller 88

2.5-9 Processing Functional Diagram of Integrating Controller

for Automated Housekeeping 91

2.5-10 Trade of Integrating Controller Functions 94

2.5-11 Schedule for Integrating Controller Technology Advancement Program 100

v
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DISO-27935-1

LIST OF TABLES

No. Page !

r

2.3-1 Resources for Data Management System Simulation Program 39 'r

2.3-2 Resources for Network Interface Unit 'technology Advancement Program 41

2.3-3 Resources for Network Operating System Technology Advancement

Program 43

2.4-1 System Weight Comparison 54

2.4-2 Resources for Two-Phased Thermal Management Pump Advancement

Program 61

2.4-3 Resources for Heat Exchange Technology Advancement Program 63 4

2.4-4 Resources for Two-Phased Water Interior Loop Technology Advancement

Program 66

2.5-1 Space Station Autonomy/Automation Philosophy 68

2.5-2 Functions for Housekeeping Controllers 69

2.5-3 Electrical Power Subsystem Automation 71 r

2.5-4 Life. Support Subsystem Automation 72

2.5-5 Thermal Control Automation 79

2.5--6 FY84 RTOP Submissions Related to Technology Applicable to

Space Station Integration of Automated H/K 98

2.5-7 Resources for Integrating Controller Technology Advancement Program 101

v!

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D180-27935-1 tfa

r^

^.FST OF ACRONYMS AND ABBREVIATIONS

APSTS Advanced Platform Systems Technology Study

BAC Boeing Aerospace Company

F,

BIT Built In Test

i

CADPS Communications and Data Management Station

s

CAE Computer Aided Engineering

CAMPS Construction and Material Processing Station

CCD Change Coupled Device

Cg Center of gravity til!

CMG Control Moment Gyros

CO2 Carbon dioxide

CPU Central Processor Unit

CRT Cathod Ray Tube

do/ac direct current/alternating current

deg/sec

^.

degrees per second Io

DMS Data Management System isi

EASY

EVA Extra Vehicular Activity

ft feet

FY Fiscal year i

HR Hour

H2O water

IAC

I.D. Inside diameter

I/O Input-output

JSC Johnson Space Center

vii
DISO-27935-1

LIST OF ACRONYMS AND ABBREVIATIONS (CONTINUED)

KG Kilograms

kW Kilowatts

LAN Local Area Network

lb pound

LED Light Emitting Diode

LISP List processor

LOARS Land, Ocean, and Atmospheric Research Station

MBPS Million bits per second

MHZ Megahertz

MIPS Million iterations per second

MSFC Marshall Space Flight Center

NASA National Aeronautics and Space Administration

NASTRAN

NIU Network Interface Unit

N-M-Sec Newton-meter-seconds (a measure of force)

NOS Network Operating System

ns nanoseconds (14- 9 seconds)

O.D. outside diameter

ORACLS Optimum regulator and control of linear systems

OTV Orbital Transfer Vehicle

PIN Positive intrinsic negative

PSI Pounds per square inch

PSIA Pounds per square inch absolute

PSID Pounds per square 'inch differential

R&D Research and development

RCA-PRICE Radio Corporation of America - Price Modeling program

RFP Request for Proposal

R1 Expert system used to configure VAX installations

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DISO-27935-1

- LIST OF ACRONYMS AND ABBREVIATIONS (CONTINUED)

RIT Receiver - Transmitter

RTOP Research Technology Objectives and Plans

sec second

SRS Spectra Research Systems

TCC Trace Contamination Control

TDMA Time division multiple access

TDRSS Tracking and Data Relay Satellite System

VAX Virtual Address Extension

VCD Vapor compression distillation

VHSIC Very High Speed Integrating Circuit

WQM Water Quality Monitor

ix

4
D180-27935-1

1.0 INTRODUCTION

This is the Executive Summary which is volume I of the final report on the Space Station

Systems Technology Study conducted for the Marshall Space Flight Center (MSFC) by the

Boeing Aerospace Company (BAC) and Spectra Research Systems (SRS). The overall

study objective was to identify, quantify, and justify the advancement of high-leverage

technologies for application to both the early and more advance space station. Research

plans were developed for each of the selected high-leverage technologies. The objective

was fulfilled through a systematic approach tailored to each of the technology areas

studied.

The current Space Station Systems Technology Study was an outgrowth of the Advanced

Platform Systems Technology Study (APSTS) which was completed in April 1983 for

MSFC by the Boeing/SRS team. The first study proceeded from the identification of 106

technology topics to the selection of five for detail trade studies. During the Advanced

Platform Systems Technology Study, the technical issues and options were evaluated

through detailed trade processes. Individual consideration was given to costs and benefits for the technologies identified for advancement, and advancement plans were developed. An approach similar to this was used in the current study with emphasis on system

definition in four specific technology areas.

The four study areas addressed in the Space Station Systems Technology Study are:

(1) Attitude Control, (2) Data Management, (3) Long-Life Thermal Management, and (4)

Automated Housekeeping Integration. These four areas are extensions of areas identified during the APSTS and were conducted to facilitate a more in-depth understanding

of the technology issues. While high-leverage technology identification was a study goal,

different study approaches were used for each study area. The attitude control study

utilized a specific representative configuration and determined by simulation the applicability of a low-bandwidth control system for space station use. The data management

task concentrated on the architecture characterization into structural blocks and systems to facilitate simulation planning. The thermal study focused on characterizing a

two-phase heat transport systems within the long life requirement constraints. The

automated housekeeping task was structured to characterize the functions of an integrated controller for an overall management system. Each of these approaches produced

useful advancements in the understanding of technology issues and development needs.

The summary discussions are presented in the following sections.

1
DISO-27935-1

{ The overall study was divided into four tasks. During task 1 the design concepts in each

of the four study areas were refined. The concepts were used to annunciate specific

technology options upon which comparative studies were conducted. Candidate highleverage advancement Technologies were then selected from the options. The cost,

benefits, schedules, and life cycle costs for the options were evaluated in task 2. Selection of the technology advancement items was made during this latter task. Technology

advancement plans were prepared for each of the selected items in task 3. All study

documentation was prepared in task 4. The overall study plan flow diagram is shown in

figure 1.0-1.

This volume presents a summary of the work performed to select these high leverage

items. The total final report is made up of this volume, Volume II: Trade Study and

Technical Selection Technical Report, and Volume III: Technology Advancement Program Plan. More detailed discussion of the trades conducted and the technology

advancement plans are given in volumes II and III respectively.

1.1 TECHNOLOGY SELECTIONS AND RATIONALE

Seven potential technology advancement items were identified during this study. These

items were analyzed and evaluated in task 2, considering technical as well as cost benefits and schedule criteria. Study plans were prepared for each of the selected high leverage items. These selected items are:

1. Data Management System Simulation Package.

2. Data Management Network Interface Unit.

3. Data Management Network Operating System.

4. Two Phase Thermal - Long Life Pumps.

5. Two Phase Thermal - Heat Exchanger.

6. Two Phase Thermal - Two Phase Water System.

7. Integrating Controller for Space Station Autonomy using Expert Systems.

The following sections summarize the rationale associated with selections made in each

of the four study areas.

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DISO-27935-1

1.1.1 Attitude Control Rationale

The objective of the attitude control study was to investigate a control system concept

thru simulation modelling to assess whether a core-mounted reactive controller could

provide satisfactory attitude control of a -typical space station. The simulations were

run, and the results indicate that a core-mounted controller that reacts to disturbances

fed back thru the structure is stable. The simulation results did expose a potential problem area due to very lightly damped oscillations at the astromasts in response to

modelled one shot disturbances. These oscillations appear to be of low amplitude and

therefore may not be disruptive to the space station. Modelling of the effect of cumulative disturbances is indicated for future studies.

The reason this simulation approach was taken is that speculation has been extensive on

how difficult the flexible dynamics of the station would be to control. This simulation

study is a start toward a better understanding of that problem, and a better understanding of where technology advancements are really needed in the attitude control area,

1.1.2 Data Management Rationale

The rationale for the technology selections in the data management area is that the 1

system will be complex and highly interactive with other systems and with missions of

the space station. An early simulation is therefore required of the data management

system allowing synthesis of the local area network (LAN) and sizing of data managemeet system components. The simulation package definition, in the presence of all the

undefined complexity of the space station at this time, is a technology advancement

effort that needs to be started.

The Network Interface Unit and Network Operating System advancements are the hardware and software areas needed to support the development of a local area network for

the space station. Within these two areas, several specific items are recommended for

advancement and are listed on figure 2.3-9 of this volume. Examinations of the study

configurations and concepts did not reveal any specific technology that is likely to be a

show stopper if not advanced. However, the general complexity of the, system and the

data management interfaces indicate that early structuring thru simulation is essential.

I 1. .J

4
2

D180-27935-1

{ The cost benefits analysis of the APSTS was not changed by the conclusions of this study.

The reduction in system development and operating costs thru use of a well definad local

area data management network remains as an impressive eight dollar saving of system

integration costs for every dollar spent in establishing an early structuring of the data

management system.

1.13 Lang Lifetime Thermal Rationale

The rationale for the technology selections in this area is based on the results of an analysis of the weight, size, and complexity of two-phased heat transport system concepts as

compared with pumped liquid concepts. The first result of the study is that the twophased concepts will be several thousand pounds lighter than the single phase liquid systems. The second result is that use of a two-phased loop for the interior cabin heat

transport would improve the weight advantage of the two-phased system by approximately 1000 additional pounds. This internal two-phased loop would also provide design

flexibility to support space station evolution. For these reasons, the development of a

two-phased (non toxic) water loop for heat transport within the space station pressurized

cabins is selected as a primary technology for advancement.

Further technology advancement effort to improve the life of pumps operating in space

is based on existing studies that indicate that current centrifugal pumps are unlikely to

operate continuously for the 10 years associated with the space station. Heat exchanger

technology advancement is also indicated especially when two-phased systems are used

both for the pressurized module heat transport and the main heat transport system on

the space station.

The cost benefits analysis for these technology advancements is detailed in section 4.3.9

of volume II. In summary, the benefits are based on transportation cost savings due to

weight reduction, radiator assembly cost savings due to smaller area, and system development cost savings due to reduced complexity (RCA-PRICE modelling was used here).

The costs were the estimated technology advancement costs. The result was that eight

dollars in quantified benefits could be achieved for every three dollars spent in advancing

the technologies in this area.

5

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D180-27935-1

1.1.4 Integration of Automated Housekeeping Rationale

The concept development group for the space station task force has established an

autonomy/automation philosophy for the space station (see table 2.5-1). This philosophy

is in agreement with the needs of a space station to provide a facility for a wide range of

missions without encumbering the crew (or mission controllers) with excessive hours for

station upkeep. This philosophy is also in agreement with the needs for efficient and

balanced operation of the space station complex systems over extended lifetimes with

limited consumable and power resources. The rationale for autonomous systems to provide housekeeping of the space station is that they are completely consistent with the

needs of a meaningful long life and evolutionary space station concept.

The rationale for the development of an integrating controller is that the controller is

necessary for space station autonomy because it provides overall decision-making functions to replace those that would otherwise have to be provided by human mission controllers or astronauts. The results of developing the integrating controller may also

drive out needs for advancements in space qualified data processing equipment, sensors,

actuators, and devices for interacting with the crew. If advancements in these areas

are needed, the development lead times may be long so those needs should be identified

by starting and advancement program for the integrating controller as soon as possible.

The cost benefits assessment of this study resulted in some modification of the conclusions of the Advanced Platform Study completed in April of 1983. The cost modification was based on higher costs due to higher labor rates and a more detailed understanding of the functions of the concept. The benefits were modified due to a consideration of phased application of the technology to the space station over a ten year

period. The result was that the cost versus benefit ratio changed from one to ten to four

to ten. This still provides an Impressive return on the advancement dollars spent and

does not consider the significant unquantifiable benefits of the integrating controller.

LQor

6
D 1$0-27935-1

2.0 TECHNICAL SUMMARIES

,this section summarizes the results of the trade study and technology advancement planning efforts conducted for the Space Station Systems Technology Study.

2.1 INTRODUCTION

The trade study effort conducted on Space Station Systems Technology Study characterized system concepts in order to define cost versus benefits for data management architecture, long-life thermal management, and integration of automated housekeeping. The

attitude control topic selected for study focused on characterizing the space station

attitude control problem through simulation of non interacting control system responses.

The first three topics, mentioned above, focused on specific technology items that require advancement in order to support a 1990 initial launch of an early space station,

while the attitude control study was an exploration of the capability of a conventional

controller.

The characterization studies were structured to start with the issues identified in the

Advanced Platform System Technology Study completed in April of 1983. Investigation

of these issues motivated consideration of a more detailed characterization of the four

topics that were then covered in this current study. A definition of concepts based on

space station needs and constraints was developed for each of these areas as an initial

step in the current study. These concepts were based on requirements that were derived

from space station related documentation or from requirements known to exist for similar missions. The next step was to develop the characterizations to identify options

within the trade topics. Based on fife cycle costs and benefits the options were then

evaluated and technologies necessary to support the more promising options were identified.

Cost and schedule factors related to advancing the technologies recommended in the

data management, long lifetime thermal management and integration of automated

housekeeping areas are also summarized in this section.

The four study topics are presented in this final report in the order that was established

by the RFP. That order is attitude control first, then data management architecture,

long-life thermal and lastly, integration of automated housekeeping. A summary of the

V

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DISO-27935-1

study approaches and results of the four topics is presented in this volume. Detail trade

study technical information is in volume II, and detailed advancement planning information is provided in volume III.

2.2 AT17TUDE COOL

The objective of the attitude control study was to examine the technologies required for

solving the control-structure interaction problem in space station design. The approach

was to determine through analysis and simulation the degree to which noninteracting

low-band controller technology is applicable to attitude regulation of a space station

with large flexible solar arrays. primary emphasis was given to identifying the limitations of low-band controller technology for flexible space station applications. Passive

and active control technologies were to be reviewed as potential improvements to the

damping provided by a low-band controller in the event that attitude stability and performance was unacceptable.

In this study all the available attitude information, including flexible effects as measured

by an ideal sensor package mounted on the core station, is passed to ideal control

moment gyros (CMG) actuators that attempt to control the attitude about the center of

mass. The low band controller will therefore attempt to regulate attitude in the presence of induced disturbance torques due to flexibility without actively controlling the

motion of the flexible elements. This simulation study demonstrated that a coremounted linear ideal controller is stable in the presence of flexibility and will provide

significant damping of most of the major structural modes. Some of the modes, however, cannot be controlled with a core mounted controller. The important issues are the

amplitude to which those modes are excited and the implications of sustained vibration

of the associated structural members.

'right-pointing accuracy requirements could produce associated requirements for

increased control system bandwidth. As controller bandwidth increases, many structural

modes will be included within the controller passband. Active stabilization of these

modes without sacrificing pointing accuracy is another major issue. Adapting to variations in mode shapes and frequencies caused by space station configuration changes is

elso a major issue.

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2.2.1 Technical Approach

The technical approach is formulated in terms of five main tasks. These tasks are identified in the discussion to follow.

The first task in the process was to select the configuration for the space station technology study. This was derived from the limited class premise with adherence to the

NASA governing assumption which is "a space station as a permanently inhabited facility engaged in productive work and delivered to low earth orbit in stages the dimensions

of which are consistent with the shuttle cargo bay."

The second task was to develop a schematic architecture consistent with the functional

attributes and incorporating various strategies for growth leading to a 12-man configuration representative of shuttle deliverable hardware.

The attitude control study considered four operational stages that incorporate two

phases of assembly, with and without the orbiter docked. The two phases of assembly

will include the initial habitable stage and the all-up fully operational stage.

A pictorial view of the study configuration is shown in fig. 2.2-1. A representative build

up sequence is shown in fig. 2.2-2 along with the stages selected for analysis.

Mass balance was a principal design goal in order to ensure that CMG controllers will

enable attitude stabilization with minimal expenditure of energy for momentum management. Dynamic balance is achieved by center pivoting the solar panels. This configuration eliminates dynamic products of inertia that arise as the panels are rotated to track

the sun line. The center mounted solar panels also increase the lowest frequency structural mode by a factor of two due to halving the length of the solar panel deployment

mast.

The third task was to develop a finite element model of the station and the resulting

mass and stiffness distribution of the structure into NASTRAN. The output modal data

from NASTRAN established the normal mode shapes and natural frequencies of vibration

for the simulation.

9
D180-27935-1

The fourth task was to develop a system of analysis programs for control and structure

interaction analysis and simulation, and these are shown in fig. 2.2-3. Finally, the analysis of attitude control system stability was performed by arguments based on the theory

of positivity of operators. The basic stability theory was verified by frequency response

methods and time response from simulation of the closed loop system. The performance

of the closed loop system was determined from time response data. System performance

includes the motions of the central core and the flexible elements. Stresses at the root

of the solar array boom and astromast were derived from time response data.

2.2.2 Technical Discussion

The simulated response of the structure to the test disturbance represented by an impulse doublet was computed for both open loop and closed loop cases (see figure 2.2-4).

The block diagram for the closed loop system representing an attitude regulator is shown

in figure 2.2-5. The nodal structure indicating the nodes used to extract measurement

data is shown in figure 2.2-5. Motion of the core structure relative to an inertial frame

was extracted from the rotational state of the variables ^ , 8 , * (roll, pitch, and yaw,

about x, y, z) of node 100. Measurements of flexible element motion relative to node

100 are specified as follows. These rotational measurements indicate the ilex and twist

of the solar panel boom and the astromast structure,

MBx

Flex of panel boom 0100-105)

MB = Twist of panel boom (E)100-105}

MBz

= Flex of panel boom (*100-105)

MAx; Twist of the astomast 0100-323)

MAY

= Flex of the astomast (6105-323)

The quantltiesE^, EB ,E^represent the contribution of the flexible modes to the total

attitude response. For example 6 = $ f +Ee is the total rotational response of node 100

about the pitch axis and Of is the component due to the free - free motion only. It is

noted that quantities MBx, MBz, and MAy represent the mode slopes at the end of the

associated flexible members. All response quantities are in arc-sec.

2.2.2.1 Control System Responses

Examples of the simulated response of the attitude regulator to the test disturbance are

shown in figures 2.2-7 thru 2.2-9. The system bandwidths chosen for presentation are

.05 Hz for configuration land .25 Hz for configuration 2. The controller was a simple

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proportional plus derivative feedback of free - free mode attitude measured at node 100

(fig. 2.2-6). The time responses indicate that regulated free - free made attitude is both

stable (in accordance with theoretical predictions) and controllable. The controllability

of the structure is not surprising because the impulse energy analysis has clearly indicated that controllable normal modes contain motions of all structural elements with the

exception of the astomast twist. The time responses support this claim and would indicate that torsional vibrations of the astomast are not controllable with the controllers

and sensors mounted on the rigid core as expected.

It is noted that the rate of suppression of vibration (damping) in the structural elements

appears to be independent of vehicle Inertia for fixed free - free mode control bandwidth. However, the magnitude of the vibration is, of course, inversly proportional to

vehicle inertia as expected. The damping of structural vibrations for a given vehicle

inertia decreases with increasing free-free mode control bandwidth. This is due to the

fact that with increasing bandwidth the closed loop modal poles approach the open loop

modal zeros, which are virtually undamped. The result is that the residual in the

response due to a given modal pole is reduced but so is the closed Ioop damping on that

pole.

The response of the structure to a typical orbiter docking from impact loading at body

station 1201 is shown in fig. 2.2-10. It is assumed that the orbiter has an initial rotational rate at docking about its c.g. of o° .2 deg/sec with a linear velocity of

o- .15 m/sec as shown in figure 2.2-11. Assuming the centerline of shock is I meter

from the station c.g. and further assuming that the collision is perfectly elastic, the

resulting impact will impart approximately 2500 N-sec to the station.

2.2.3 Summary os Results

The important control and structure interaction issues for a representative space station

configuration have been addressed. Specifically, the stability and performance of the

station with a core-mounted linear controller has been investigated. The inertias are of

order 106 with solar panel size of 1100 m 2, which is consistent with a 75 kW power requirement. The following statements summarize the results of the study.

I. Analysis has shown and the simulation has verified that the raft configuration is

stable and controllable when ideal sensors and CMG actuators are colocated.

18
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D180-27935-1

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D180-27935-1

Because the raft is rigid at frequencies of interest (0.5 - .5 Hz), colocation of ideal

sensors and actuator on the raft will guarantee stability.

2. Damping of the structural modes is substantially augmented in most cases by the

CMG core mounted controller. Damping of astromast torsional vibrations is not

augmented by the core mounted controller.

3. The performance of the ideal reactive controller to suppress transient disturbances

at levels of practical interest is limited only by the control authority. The issues

addressed in the current simulation work are therefore related to the assumption of

ideal (infinite band-width noise free) sensors and actuators.

4. Simulation shows no extreme motions of flexible elements when subject to the most

severe shocks due to docking loads. The loads were modeled as impact forces at the

docking interface. The maximum stress at the roots of the array boom and astromast are at least a factor of 100 less than the proportional limit stress.

5. Gimbal rate response to the test impulse doublet was found to be as high as 60/sec

for controller bandwidth of .05 Hz. Skylab class gyros are rate limited to 4-60/sec.

Therefore, if bandwidth above .05 1-lz is required for the class of space station

studied here, then three Skylab gyros is the minimum number to ensure accuracy of

100-200 arc sec under the assumed level of transient loads.

2.2.4 Conclusions

The conclusions of the study can be summarized as follows. Control of the free -- free

attitude modes using a regulator consisting of colacated CMG actuators and ideal rate

and position sensors is asymptotically stable. However, the response of flex modes associated with the astromast is lightly damped with long settling time. 11 the resultant low

amplitude vibrations are objectionable, then flex mode damping must be introduced.

Investigation of passive damping techniques should be a first priority. With these results,

the important issues of core station free - free mode attitude control using a simple controller without additional stability augmentation of the flex modes has been addressed.

21
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D180-27935-1 ti

i

2.2.5 Recommendations q

Continuing effort in attitude control for space station should concentrate on defining

control requirements during build-up and construction phases including configuration

with the orbiter docked. Emphasis should be given to definition of control modes for

each phase of evolution and schemes for managing the momentum envelope of candidate

momentum transfer systems. Control modes would include electromagnetic sensing and

actuation, momentum transfer, mass expulsion, attitude biasing, and appendage

articulation,

22

L
D180-27935-1

23 DATA MANAGEMENT

Data management includes the data system hardware and software needed to provide all

Space Station data processing, rtorage, and communications for onboard users, subsystems and payloads. This study was based on requirements determined in the Advanced

Platform Systems Technology Study as shown in figure 2.3-1, and extended that work as

summarized by the paragraphs that follow in this section.

2.3.1 Approach

Specifically, the three areas of data management extension for the Space Station Systems Technology Study are:

1. Mission configuration analysis.

2. Network interface Unit (NIU) description.

3. Network Operating System (NOS) definition.

The purpose of the configuration analysis subtask was to assess the impact of candidate

Space Station missions on the DMS, to ensure that the concepts developed in the previous

study would meet all requirements. This analysis was used to develop a DMS model for

future simulation studies, and also provided an input to subtasks two and three. The NIU

and NOS were identified in the APSTS, and a cost benefits analysis was conducted to

determine their potential value to the program. It was estimated that a potential savings of $176M could be realized if the LAN were developed, and if the onboard subsystems and payloads used the LAN hardware and software for data collection, processing,

storage, and communications. The higher cost alternative would have each experimenter

develop his own DMS hardware and software, followed by a systems integration step to

make the payload compatible with the onboard data management system. This approach

results in needless duplication of effort, when compared to the LAN. Also, the . savings

of $176M refers only to development costs. It is believed that the LAN would also yield

significant savings in operational costs, due to the ease of maintenance resulting from its

standardized, modular organization and due to the reduction in logistics requirements

brought about by the use of a small set of common modules.

The first subtask under study task one, was to investigate the impact of possible Space

Station mission configurations on the DMS, so that data communications bandwidths,

23 i

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D180-27935-1

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Figure 2.3-1 Elate Processing, Storage and Communications Requirements

24

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D180-27935-1

data storage capacities, processing requirements and interfacing requirements could be

estimated. Three mission models were investigated, including Construction and Materials Processing Station (CAMPS), Communications and Data Management Station

(CAMPS), and Land, Ocean, and Atmospheric Research Station (LOARS).

After completion of the mission configuration analyses (subtask 1), the impact on the

DMS hardware and software systems could be assessed more readily. This permitted the

primary hardware element of the DMS to be analyzed and described in greater detail, as

subtask 2; with the primary software element defined functionally, as subtask 3. These

elements are the Network Interface Unit (NIU) and Network Operating System (NOS),

respectively. Together, they comprise the onboard LAN that integrates the subsystems,

instruments, user interfaces, and other equipment that require data management services. The NIU provides the system connection points or interfaces, while the NOS controls the data communications, storage, and processing activities of the DMS.

2.3.2 Technical Discussion

Figure 2.3-2 shows how the backbone local area network might fit into a typical space

station configuration called the raft structure. The heavy lines are bundles of optical

fibers, that interconnect the network interface units.

The topology can be described as a two level hierarchy. The NIUs and their interconnections provide for communication between station modules, and form the upper level

of the hierarchy. The devices connected to the links and buses within the modules, supported by the NIUs, form the lower level. This approach allows for modularity at both

levels. The NIUs handle intermodule communications through standard berthing-port.

interfaces, allowing station modules to be plugged-in at any berthing port. At the loaner

level, sensors and medium-speed devices can be plugged into the NIUs by means of standand interface cards and standard buses.

The multi-star and graph fiber-optic backbone network topologies appear to be viable for

the station; they are shown in figure 2.3-3. The diagram shows the two possible methods

for interconnecting the station NIUs by means of fiber optics. The set of lines drawn

above the boxes represents the interconnection topology formed by the use of four optical start couplers, located near NIUs C, D, E, and F. For example, the coupler located

at NIU-C interconnects A through E, as shown by the lowest horizontal line. In this

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Figure 2.3-3 MulPi-&ar Versus Graph Topologies
D180-27935-1

example, each of the couplers would interconnect a subset of five of the eight NIUs, so

four five-port couplers would be required. The set of lines drawn below the boxes represents a point-to-point interconnection topology. Each link consists of a bidirectional

channel, using two fibers with transmitters and receivers at opposite ends. Store-andforward communications techniques are used, as opposed to the shared-bus techniques

needed for the multi-star topology.

The transmitter and receiver logic is essentially the same in both cases, as shown in

figures 2.3-4 and 2.3-5. These figures are block diagrams of the circuitry needed to

implement optical transmitters and receivers, with the exception of the control logic.

The transmitter converts digital data residing in memory to a serial bit-stream, encodes

it with clock information, and uses the resulting signal to modulate an optical source.

The receiver uses an optical detector to convert the signal back to an electrical form for

decoding and conversion to a parallel word format that can be stored in a memory

buffer. These examples use a 32-bit memory and a 100 MHz serial data rate, so the

required memory cycle time (320 ns) is relatively slow.

The two configurations use different access protocols for multiplexing the communications media. The graph topology uses simple TDMA, while the multiple-star topology

may use polling, contention, or token-passing. In a polling system, one of the NIUs functions as a controller, polling each of the other NIUs in sequence to enable them to transmit data, one after the other. In a contention scheme, each NIU acts independently and

listens for activity on the communications channel. If the channel is not busy, the NIU

can transmit; however, two may transmit almost simultaneously, resulting in a collision.

They must detect such bus con-cention, back off, and try again after a random delay interval. in a token-passing configuration, the system is initialized so that one of the NIUs

owns a logical token that enables it to transmit a packet. After completing its transmission, it then sends the token to another NIU, which may transmit and then pass the

token to the next NIU in sequence.

At this point, no clear reason seems to exist for choosing a pure graph or a pure multiple-star topology over the other. It is believed that data management network simulation studies are needed before a final configuration can be chosen.

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2.3.2.1 Network Interface Unit (NIU)

As shown in figure 2.3-6, the NIU is defined as a set of standard circuit cards that plug

into a high-speed parallel data bus, housed in a rack-mountable chassis. The cards provide high-speed sensor control and data acquisition interfaces, instrumentation bus interfaces, fiber-optic intermodule communications transceivers, and many other types of

input-output (I/o) interfaces and controllers.

The results of the study in this area indicate that the NIU should be modular, and should

have a high performance potential. Space Station requirements will surely change over a

period of many years, and the basic NIU chassis and high-speed parallel bus can support

such changes and upgrades if they are designed with flexibility in mind.

Development of NIU modules will be a major project, because a dozen or more standard

electronic modules will have to be specified, designed, and fabricated to meet most of

the potential station applications, such as data acquisition or subsystem interfacing as

follows:

I . NIU control processor and cache memory.

2. Fiber-optic communications transceiver.

3. Instrumentation bus interface controller.

4. RF communications transceiver interface.

S. Digital voice communications interface.

6. Crew station console/CRT interface.

7. High-speed sensor data buffer.

S. Magnetic tape mass memory controller.

9. Magnetic disk mass memory controller.

10. Color video & graphics I/O controller.

11. Analog I/O interface.

12. Discrete digital parallel interface.

Custom modules would also be needed, for specialized applications such as high speed

sensors.

31

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32
D180-27935-1

2.3.2.2 [Network Operating System (NOS)

An operating system is the collection of software processes and functions that control

computer systems, as shown in figure 2.3-7. In a dnstributed system environment, or in a

local area network, the term network operating system (NOS) is frequently used, and has

been adopted here. Aboard the Space Station, the NOS is conceived to have two major

functions. First, it provides the operating environment for DMS users. Second, it manages the overall operation of the devices attached to the network, supporting status

monitoring and control functions, and providing data storage, communications and processing services.

Development of an automated diagnostic and reconfiguration software system, as part of

the NOS, appears to be a major task. So-called nonstop computer systems exist, but they

are not in common usage and are not 100% effective. It would appear that more effort

is needed if such a capability is to be available for use aboard the station. One of the

most promising approaches to such a technology development is the use of software simulation to model the DMS and the NOS, and to test the response of the system to the

injection of simulated faults.

As mentioned above, a prime development task is to determine how automated diagnostic and reconfiguration software can be implemented. Figure 2.3-8 shows how a DMS

simulation process can be used to inject errors and hard faults into the model, to determine the impact on system functionality, and to test the performance of automatic

reconfiguration algorithms.

The simulation package consists of several software modules, as shown in the diagram.

The most important are the producers, servers, consumers, and the instrumentation

module. Producers simulate the production of messages or packets that, in a real system, would be transmitted by the devices that make up the DMS. The servers simulate

the behavior of the network communications components and software protocols. Consumers are the devices to which the messages or packets are sent. And finally, the instrumentation module performs data collection and simulates` fault injection.

The simulation package will allow the use of modern CAE techniques in DMS design, in

the same way and for the same reasons that integrated circuits are designed and simulated prior to fabrication. Simulation can give excellent indication of system performance, before major resources are committed to production; and, various concepts can be

traded and compared to produce an optimal design.

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35

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DISO-27935-1

2.3.3 Conclusions and Recommendations

The work performed during the data management study led to conclusions in data management system configurations, system hardware (NIU), and system software (NOS).

Three potential mission configurations were analyzed, with the Land, Ocean, and Atmospheric Research Station (LOARS) model developed in enough detail for simulation studies

to commence. The NIU was analyzed to the point where component technologies could

be identified; and the NOS was defined to a level of detail that included individual software modules and their functional interrelationships. These analyses were then used in

the second part of the study, task 2, to help in the evaluation of the need for each. In

the data management study, 16 technology areas were Identified during task 1 and were

scored in 5 categories, with a rating of 0, 10, or 20. These scored technology areas are

listed on figure 2.3-9. On that figure, a technology needed early in the program is more

critical to success than one that is needed Iate, so a score of 20 was assigned. The total

scores give a rough estimate of the program criticality of each of the 16 technologies.

That is, an area with a high score is an area that may have a greater program impact.

An area with a low score, such as the high-speed sensor data buffer, may still be important; however, low cost and risk, combined with a late need and relatively short lead

time mean that the relative program impact may be quite low.

The simulator, the NIU, and the NOS are the key elements of the DMS that have been

identified and described in detail during the Advanced Platform Systems Technology

study and those elements still appear to provide the greatest cost savings to the program. The total cost of development for the three items is $22.45M over six years. If

the development cost savings to the program is $176M primarily in reduced systems integration costs, then the ratio of benefits (savings) to cost is 7.9. That is, for every dollar

spent on network simulation, hardware (NIU) and software (NOS), NASA can expect savings in DMS development cost of almost eight dollars. The potentiai savings in operating

costs are also considered to be quite significant, and are worth investigating in future

studies. The main conclusion is that in the Space Station DMS development some technologies are needed before others and are, in fact, needed to facilitate development of

others.

36
D180-27935.1

20 EARLY LONG HIGH HIGH HIGH

SCORING 10 MID MID MID MID MID

0 LATE SHORT LOW LOW LOW

TECHNOLOGY AREA NEED I LEAP] 1 . COST I FRISK I VALUE TOTAL

HARDWARE

-eSTANDARD CARDS 20 10 20 10 20 00

*STANDARD BUSES 20 20 10 0 20 70

oF.O. TRANSCEIVERS 10 10 10 10 10 SO

*DECODER CHIP 10 10 10 10 10 50

SOFTWARE

O SIMULATOR 20 10 10 20 20 so

& EXECUTIVES 20 10 20 10 20 BO

*PROTOCOLS 20 10 10 10 20 70

& DIAGNOSTICS 10 0 0 0 10

GENERAL SYSTEM

*PAYLOAD DELI. SYS. 20 20 10 10 20 SO

*MAINTENANCE EXP. 10 10 10 20 20 70

0 IMAGE PROCESSOR 0 20 20 20 10 70

0 CONTROL SOFTWARE 10. 10 10 10 10 so

a INTERFACE TEST SET 20 10 10 0 10 s0

e CREW WORKSTATION 10 0 0 _ 0 10 20

0 DISK/BUBBLE MEM. 10 0 0 0 10 20

eDATA BUFFER 0 0 0' 0 10 10

Figure 2:3-9. Criticality of Technologies

11

37
TECHNICAL YEAR APPROACH 1 • 2 3 4 5 5

STEP TASKS

1 REQUIREMENTS DEFINITION —-^» m ---

2 CONCEPTUAL DESIGN

3&4 SIMULATOR SOFTWARE

5 SIMULATION ........e ^. b.».n._ ._

GR^^Css1UIeEDgggR^yASED -^ SPACE SYSTEM

^7Y^^iF1

CONCEPT SPACE

VERIFICATION QUALIFICATION

(VOTES: (1) DEVELOPMENT SdHEDULE BASED ON SCHEDULE FROM VOLUME Ill, "ADVANCE PLATFORM

SYSTEMS TECHNOLOGY STUDY"

V) SCHEDULES BEGIN AT ATP OIL NIV. IF ATP OCCURRED IN 4TH QUARTER OF 1ST YEAR

OF SYSTEM

(3) DARK LINES INDICeATt HEAVY EMPHASIS. DOTTED LINES INDICATE COORDINAT-ION

EFFORT.

Figure 2.3-1D Schedule for Data Management System Simulation Program

i

} o

F

E^

t^

0

000E

l^W

t71

F

iv
_

r ft

TECHNICAL

APPROACH

STEP

YEAR FROM ATP

TASK

1 2 3

TOTAL

(GROUND

BASED

SYSTEM)

1 REQUIREMENTS DEFINITION 700 350 3DD 1350

2 CONCEPTUAL DESIGN 2DO 800 350 1350

2,E 4 SIMULATOR SOFTWARE 850 760 200 16QO

5 SIMULATION 50 750 1250

TOTAL 1660 2400 1 6M 51"250

4 6 S

TOTAL

(SPACEBASED

SYSTEM)

OVERALL

TOTAL

...

- - 1350

— -- -- - 1360

9041 104? 100 300 Wa

660 200 9513 IWO 2250

73Sf1 300 260 1200 (

w

w

d

000

N

V

W

w

r^.

"able 23- 1 Resources for Data Management System Simulation Program

ROTEC: (1) FIGURES IN $1000 (1083)

(2) ESTIMATES TA€ EN PROM VOLUME IV, "ADVANCED PLATFORM SYSTEMS

TECHNOLOGY STUDY"
TECHNICAL

APPROACH

STEP

YEAR

TASKS

1 2 3 4 S 1

1 REQUIREMENTS DEFINITION --- - ------ -- ------ •--•--- --^

2 HIGH BANVWIDTH SENSOR

INTERFACE DEVELOPMENT

3 INiTRUMENT BUS

DEVELOPMENT

4 OPTICAL OUTPUT MODULE ._ __..___ ­-4

5 OPTICAL INPUT MODULE ^- ------ --- --^

6 INTERNAL BUS

DEVELOPMENT

J

0

0

iNv

w

u

0

^FGROg S EM EDleSPACE-BASED SYSTEM

V v

CC'NCEPT SPACE

VERIFICATION OUALIFICATION

NOTES: (1) NIU DEVELOPMENT SCHEDULE BASED ON SCHEDULE FROM VOLUME IV, "ADVANCE PLATFORM SYSTEM

TECHNOL003YSTUDY"

121 SCHEDULES BEGIN AT ATP ON NIU. IF ATP OCCURRE13 IN 4TH QUARTER OF 1ST YEAR OF SYSTEM

DEVELOPMENT SCHEDULE, MA. 1OR MILESTONES WOULD COINCIDE. SEE REFERENCE ABOVE

13) DARK LINES INDICATE HEAVY EMPHASIS, DOTTED LINEN INDICATE COORDINATION EFFORT.

Figure 2.3-11 Schedule for Network Interface Unit Technology Advancement Program

am
i'

i

-i

.s

.k

^r

2

S

3

4M1

i

Dr

d

C)iNV

W

r

nm

-0R5

O

^ C3

s Tj

E

Table 2.3-2 Resources for Network Interface Unit Technology Advancement Program

TECHNICAL

APPROACH

STEP

YEAR

TASKS

1 2 3

TOTAL

(GROUNDBASED

SYSTEM

1 REQUIREMENTS DEFINITION 80 10 10 10fD

2 HIGH BANDWIDTH SENSOR 120 120 10 250

INTERFACE DEVELOPMENT

3 INSTRUMENT BUS 2225 225 60 500

DEVELOPMENT

4 C- `;CAL OUTPUT MODULE 95 95 10 200

5 Q`: 4L, IldPUT MODULE 95 95 10 200

5 INTERNAL BUS — 200 350 550

TOTALS rir, 1 74s 1, 44a 18th?

NOTES; 11) SCHEDULE BEGINS AT ATP ON NETWORK INTERFACE UMT

12) TOTALS TAKEN FROM VOLUME IV, "ADVANCED PLATFORM SYSTEMS TECHNOLOG Y STUDY"

(3} SPACE-BASED SYSTEM (DEVELOPMENT UP TO SPACE QUALIFICATION SHOWN FOIL . REFERENCE).

DETAILS OF TIME PHASING CAN BE FOUND IN REFERENCE OF NOTE 2.

TOTAL

(SPACERASED

SYSTEM)

OVERALL

TOTAL.

400 500

1000 1250

200 266

1000 1200

9000 1200

2400 2950

7800 1 9WO
7

If

I '

r '

t

I

j`

1

f TECHNICAL

(n^y(^

YEAR

F S E

I REQUIREMENTS DEFINITION

2 EXECU'T'IVE PROCESSES

Ai

CODINGJDEDUQGING

3 SOFTWARE VALIDATION

1 2 3 4 S

MOM r M M r Y

®0

V r'"

®

/ Fa

0

c

7z

rya

aI...

I sv^

m

w

e

CONCEPT SPACE

VERIFICATION QUALIFICATION

NOTES: (1) NOS DEVELOPMENT SCHEDULE BASED ON SCHEDULE FROM VOLUME IV, "ADVANCE PLATFORMS SYSTEMS

TECHNOLOGY STUDY„

(2) SCHEDULES BEGIN AT ATP ON NIU. IF ATP OCCURRED IN KITH QUARTER OF 'IST YEAR OF SYSTEM

DEVELOPMENT SCHEDULE, MAJOR MILESTONES WOULD COINCIDE. SEE REFERENCE ABOVE.

(3) DARK LINES INDICATE HEAVY EMPHASIS. DOTTED LINES INDICATE COORDINATION EFFORT..

Figure 2.3 12 Schedule for !Network Operating System 7-ethnology Advancement Program
TECHNICAL

APPROACH

STEP

YEAR

TASKS

1 2 3

TOTAL

(GROUNDBASED

SYSTEM)

1 REQUIREMENTS DEFINITION 220 — w 200

2 EXECUTIVE PROCEPSES 90 1200 400 25M

rIODINGIDEBUGGIRM

3 SOFTWARE VERIFICATION — — 200 209

L_

TOTALS 11t?0 12tH 800 2905}

TOTAL

WAGEBASED

SYSTEM)

OVERALL

TOTAL

25M 00

195M 44DO

1900 :200

3'100 85MD

^E

4i W

i^

.y

vr

40

4

INV

WW

I

^ 6

s

Table 23-3 Resources for Network Operating System Technology Advancement Program

-f; C

NOTES: )1) SCHEDULE BEGINS AT ATP ON NETWORK OPERATING SYSTEM .

(x) TOTALS TAKEN FROM VOLUME IV, "ADVANCED PLATFORM SYSTEMS TECHNOLOGY STUDY-

(3) SPACE-BASED SYSTEM (DEVELOPMENT UP TO SPACE QUALIFICATION SHOWN FOR (DEFERENCE).

DETAILS OF TIME-PHASING CAN BE FOUND IN REFERENCE OF MOTE 2.

r
x... C

1

D180-27935-1

2.3.4 Technology Advancement Plans

As a result of system trades in the data management area, several components have been

pinpointed as offering significant benefits in cost and pers^,rmance. In addition, some

items were selected for advancement because they were necessary to be built for fiberoptic backbone data management system {as described in Volume II} rather than because

they were more cost effective than other options. For instance, in the case of the network operating system, there is no alternative but to have one.

The data management requirements of the early and evolutionary Space Station configu.

rations represent the near-term and evolutionary goals of the data network. Also, the

items below were selected for technology advancement because they represent those

items of a fiber optics data network that are critical since they might not otherwise be

developed in time for a FY 87 new start on the Space Station. The system development

and application area will involve a system simulation that is essentially the first generation network. The network interface unit and operating system areas are critical items

of the second generation network development.

Figures 2.3-10, -11, and -12 and tables 2.3-1, -2, and -3 provide schedules and resource

planning information respectively for the three data management advancement

programs.

2.4 LONG-LIFE THERMAL MANAGEMENT

The objective of the present long-life thermal management study was to identify heat

transport system technologies that increase performance, enhance system life, and reduce system weight and cost. Emphasis was placed on two-phase heat transport systems

that offer significant potential benefits. These systems absorb and reject heat at a near

constant temperature. This simplifies the thermal interfaces and allows thermal loads to

be placed at any location that provides a high degree of flexibility in reconfiguring the

space station. Reduced pump power requirements and heat transport by latent heat of

vaporization provide size and weight reductions compared to a conventional pumped

liquid loop heat transport system. These comparisons made possible the identification of

three new technology areas requiring advancement.

44

.:J r
D180-27935-1

The study approach, technical discussion of study and results are summarized in the following sections.

2.4.1 Approach

The trade study was divided into subtasks as outlined below:

1. Define baseline pumped two-phase heat transport system.

2. Optimize baseline system.

3. Identify optional systems.

a. Pumped liquid loop.

b. Capillary two-phase.

C, Alternate two-phase pumping concepts.

The trade study groundrules and the basic heat transport systems studied are defined in

section 2.4.2. The summary of results are presented in section 2.4.3.

2.4.2 Technical Discussion

The following paragraphs provide a technical summary of the study conducted for LongLife Thermal Management.

2.4.2.2 Groundru[es for Study

The following basic groundrules were established for the study:

1. Heat load: 25-150 kW.

2. Transport distance: approximately 150 ft.

3. Grumman Space Constructable Radiator 1.2 lb/ft2.

4. Power penalty: 350 lb/kW.

5. Heat transport fluids:

a. Two-phase: ammonia.

b. Pumped liquid: Freon 11, Freon 114, ammonia.

6. Low temperature (about 400F) heat rejection for metabolic and battery heat

loads.

7. High temperature (about SO oF) heat rejection for remaining loads.

S. Radiation sink temperature: 415 0R.

45
DiSO.27935-1

9. Pumped water heat transport loop inside pressurized modules.

10. Elements for each system:

a. Radiator.

b. Cold plates.

co Pressurized module interfaces.

d. Transport loop.

11. Thermal storage interface inclusion is beyond scope of study.

During the course of the study, only minor differences were found between the results

for Freon 11 and Freon 114. Consequently, the detailed analyses were completed for

Freon 11 only. It also became apparent that a two-phase water heat transport system

inside the pressurized modules offered benefits; that concept was added to the study.

2.4.2.2 Heat Transport Systems

Figure 2.4-1 shows the basic heat transport systems that were analyzed in this study.

The baseline is a pumped two-phase system with a liquid and vapor lines. A mechanical

pump is used to pump the liquid condensate from the radiator to the heat source heat

exchangers (evaporators). Control valves are used to meter liquid flow to the heat exchangers. The fluid vapor flows to the radiator when it condenses as the waste heat is

radiated to space. The thermal storage unit is used to provide load leveling and efficient

use of the radiator. (As noted previously, a detailed analyses of the thermal storage

interface was beyond the scope of the study.)

The capillary two-phase system is similar to the baseline system, except pumps and

valves are not required. The capillary wicks in the heat exchangers provide the required

pumping action. The pumped liquid loop is similar to the baseline system except that the

heat is transported as sensible heat rather than as latent heat of vaporization.

Alternate pumping concepts were briefly considered for the baseline pumped two-phase

system. One concept would use an osmotic pump in the liquid line. The liquid would

consist of a solvent and solution separated by a semipermeable membrane. The osmotic

pressure across this membrane causes solvent flow through the membrane into the solution. The solvent evaporates from the solution at the evaporators, condenses in the radiator and returns to the membrane. The other concept considered uses an ion drag pump.

This pump uses a high voltage probe to generate and accelerate ions in the fluid. These

ions exchange momentum with the fluid and produce the pumping action.

46
BASELINE

PUMPED 'TWO-PHASE

DISO-27935-1

ORIGINAL PAG iS

OF POOR QUAL17Y

CAPILLARY PUMPED

f"UMPEU TWO-RiASE LIQUID Lf7C3%'m

SYSTEM SYSTEM

COLD

PLATE Hx

PRESSURIZED fY}RlrP

MODULE

MATER LOOP

*COLDt

sfM7RFACE

HX

COLD COLA

PLATE H% PLATE fix

PUMP — CP

THERMAL

THERMAL STORAGE

STORAGE

I

I

RADIATOR RADIATOR

L. -- — — — — — — — _ — d

Figure 2.4-1 Heat Transport 5'Wems

47

r

u
D180-27935-1

2.4.2.3 Effect of Two-Phase Water System In Pressurized Modules

The interface between the two-phase heat transport bus and the pumped water loops in

the pressurized modules results in a lowering of the bus temperature in order to minimize system weight. The reason for this is that the water temperature change must be

less than the temperature difference between equipment and bus. Consequently, because

the water loop transports sensible heat, higher flow rates (and higher weights) are incurred as the temperature difference decreases. A two-phase water heat transport system allows a higher bus temperature and potentially fighter weight system.

2.4.2.3.1 Two-Phase Water Heat Exchanger and Line Sizing

The two phase heat exchanger weights were based on a detailed analysis conducted as

part of the study. Because the water vapor density is low for the temperature range

considered, the vapor pressure drop (in the vapor line between the equipment and interface heat exchanger) effect on vaporization (condensation) temperature was included in

the analyses.

For the high temperature heat rejection system case the vapor line was fixed at an inside

diameter of 2.25 inches and the liquid line at 0.5 inch inside diameter. These line sizes

result in an overall head difference of about 1 inch, which is compatible with capillary

pumping. The vapor line pressure drop produces a difference between vaporization temperature, at the equipment heat exchanger, and condensation temperature, at the interface heat exchanger of 1.760F. The heat exchangers were optimized as a function of

equipment to bus temperature difference that included this fixed vaporization temperatune difference.

The effect of pressure drop on vaporization temperature is more pronounced in the low

temperature heat rejection case. In -this case the vapor line size was optimized in conjunction with heat exchanger optimization to provide the lowest weight system for a

given humidity control unit to bus temperature difference. The liquid line size was fixed

at 0.25 inch O.D. with 0.02 inch wall.

48

}
VT

K

D180-27935-1

2.4.2.3.2 Effect on System sleight

Figure 2.4-2 shows the effect of incorporation of two-phase water heat transport systems in the pressurized modules on the high temperature two-phase ammonia system

element weights. The minimum total weight -now occurs at a bus temperature of 79oF

compared to the 70OF optimum for the system with pumped water loops. A detailed

schematic showing the effects on the two-phase water system is shown in figure 2.4-3.

The main bus sizes and weights remain unaffected. The equipment cold plate weights

are increased due to the higher bus temperature. The radiator and pressurized module

component weights are significantly reduced. The total system weight is 828 lb less than

that for the system with pumped water loops.

The effects on the low temperature heat rejection system are shown in figures 2.4-4 and

2.4-5. The optimum bus temperature for this case is 37.5 0F compared to 360F for the

case with pumped water loops. As in the high temperature case the bus weight remains

unaffected, the battery cold plate weight is increased and the other component weights

are reduced. The total weight is 79 lb less than that for the pumped water loop system.

2.4.3 Summary of Results

The weights for the various heat transport systems, applied to the baseline space station,

are summarized in table 2.4-1. The pumped two-phase ammonia system used in conjunction with two-phase water heat transport inside the pressurized modules is the lightest system. The corresponding capillary two-phase system is 359 lb heavier. The

pumped two-phase system with pumped water loops inside the modules is 907 lb heavier.

The pumped liquid ammonia system is heavier by 2126 lb and the pumped freon system is

heavier by 3699 lb. The total radiator area required is: 6186 ft 2 for two-phase ammonia

systems in conjunction with two-phase water loops; 6690 ft 2 for two-phase ammonia

systems with pumped water loops; 7900 ft2 for pumped liquid ammonia system; and, 8435

ft2 for pumped freon system.

244.4 Cost and Benefits Analyse

In the final report of the study completed in April of 1953 a cost and benefits assessment

was given for developing thermal storage systems for both pumped liquid and two-phase

heat transport concepts. The result indicated that those technology advancements were

49

t
a

^i

D180-27935-1

^I

!

it

ft

Gj

1'.

7000

TOTAL. WEIGHT

(CAPILLARY SYSTEM) ^^ l

6000

TOTAL WEIGHT

(PUMPED SYSTEM)

RADATOR SYSTEM

Fd

640 'J

CD

^^ BUS OAPILLARY SYSTEM) .__,..^..... ^..._ .._..o _.,.._

PRESSURIZED

M DU TWOPHASE WATER

^'^,ATE '^'RAlSP®R

SYSTEM

BUS (PUMPED SYSTEM!)

BATTERY

COLD PLATES

® 6 1. -i 1 1 t 3 I 1 !-

60 65 70 75 80 85

BUS TEMPERATURE — OF

Figure 2.4-2 High Temperature Two -Phase Ammonia Bus with Two-Phase Water Lapps

50
aL X, zi

DISO-27935-1

79°F RADIATOR 79°F

100 KW

VAPOR LINE LIQUID LINE

4342 FT2 (ONE SIDE)

5210 LBS (PANELS)

174 LBS (HK'S)

79°F EQUIPMENT 79°F

.,.... COLD PLATE

850F,10 KW

IA LBS

152 LBS

79°F 79°F

PRESSURIZED

MODULE

80 &F INTERFACE 80A60F HEAT

EXCHANGER

81.850F KW 131.850F

14.4 LBS

VAPOR LINE LIQUID LINE

225 INCH ID 0.50 INCH ID

0.022 WALL 0.02 WALL

25 FT LENGTH 25 FT LENGTH

13.6 LES 5.0 LBS

0.95 INCH HEAD LOSS 0.16 INCH HEAD LOSS

83.81°F EQUIPMENT

COLD PLATE

850F,10 KW

n

14.4 LBS

TOTAL

PUMPED CAPILLARY t

EQUIP 5780 LES 6073 LBS

POWER 88 WATTS

TOTAL 5811 LBS 6073 LES

Figure 2.4-3 Effect of Two-Phase Water Meat Transport System on High Temperature Bus

S.I.

mss.-.^ -. ^ .^-....r....^...,..,..--..-..^-,...-...-.--.^.....,..,.,.._.. ,__._-__.. _.._ _ -,. ...,3 t .rare. ^^.c 7.._^..,.-.....-..._.....^^ .__•_—____........^..Y.^,^......`.__._. _. - _ _t —lJ.
L ifii^'

lir

D18O --27935.1

ORIGINAL P92E

OF POOR QUALI1V

t

2800-

TOTAL WEIGHT

2804 Waft. ^CAPILLARY SYSTEM)/

2400 TOTAL, WEIGHT

RADIATOR (PUMPED SYSTEM)

SYSTEM

` ?J[1

^m

w^m

PRESSURIZED MODULE

200 TWO-PHASE WATER

HEFT TRANSPORT SYSTEM

BUS (CAPILLARY SYSTEM)

100

BUS (PUMPED SYSTEM)

20

BATTERY COLD PLA

of 1 l f I I I 1 1 T 1

L2®

32 34 36 38 40

BUS TEMPERATURE—OF

Figure Z4-4 Law Temperature Two-phase Ammonia Bus with Two-Phase Water Loops

52
37.5°F BATTERY

COLD PLATE

4WF,20 KW

7 LBS

37.5°F

DISO-27935-1

37.5°F RADIATOR 37.50F

25 KW

VAPOR LINE LIQUID LINE

4,09 LOS

37.50F 37.50F

PRESSURIZED

MODULE

38.043°F INTERFACE 38,1313°F HEAT

EXCHANGER

38.5580F 1 KW 38.'"x58°F

3.88 LBS =

VAPOR LINE LIQUID LINE

1.686 INCH ID 021 INCH 1D

0.020 WALL 0.02 INCH WALL

12.5 FT LENGTH 12.55 FT LENGTH { 4.65 LOS 0.82 LOS

0.118 INCH HEAD LOSS 0.501 INCH HEAD LOSS

HUMIDITY

39.485°F CONTROL UNIT

400F,1 KW

3.88 LOS TOTAL T

PUMPED CAPILLARY

EQUIP 2416 LOS 2528 LOS

POWER 42 WATTS

TOTAL 2431 LOS 2528 LOS

Figure 2.4-5 Effect of Two Phase Water Heat Transport System on Low Temperature Bus

53
D180-27935-1

^491S^tictl ?

L^.^ N':.'^^:74a li ..w .

®p poor,

Table Z4-1 System Weight Comparison

MANNED

TRANSPORT COLD MODULE RADIATOR TOTAL

LOOP PLATES WATER LOOPS HX't WEIGHT

PUMPED LIQUID LOOP

FREON 11 752 119 59 762 19259 11941

AMMONIA 2117 - 13 59 285 9604 10368

TWD-PHASE AMMONIA

PUMPED

HIGH TEMP 107 3 171 400 5558 6M9

LOW TEMP 52 4 46 70 2338 2310

TOTAL 959 7 217 470 8296 01+49

CAPILLARY

HIGH TEMP

LOW TEMP

149

149 SAME AS PUMPED TWO-PHASE 6907

2607

TOTAL 518 sm

TWO-PHASE AMMONIA

SYSTEM WIT14 TWOPHASE WATER SYSTEM

! IN MANNED MODULFF

PUMPED

HIGH TEMP 167 7 93 720 -rem 5819

LOW TEMP 52 7 27 59 2286 2431

TOTAL 159 14 120 279 7670 17242

CAPILLARY

HIGH TEMP 369 5073

LOW TEMP 140 SAME AS ABOVE 252B

TOTAL SIB DWI

NOTE: 125 KW HEAT LOAD 1100 KW AT WF; 20 KW BATTERY & 5 KW METABOLIC AT 400F)

300 FT TOTAL TRANSPORT DISTANCE

54
DISL-•27935-1

among the most desirable of the ones identified in that study. It was indicated in that

study that development costs for the two-phase system would be 50% higher due to the

complexity of:

at Phase change material packaging.

b. Thermal interface with the heat transport system.

In the current study, a further assessment of the pumped liquid versus two-phased heat

transport system was conducted. Two technologies were identified for advancement

specifically to support the development of a two-phase system. These are.

a. Two-phase water thermal transport loops for inhabited environment.

b. Heat exchanger for liquids in nearly saturated state in zero gravity.

The quantifiable benefits of these advancements are (1) that the two-phased system is

less complex than the pumped liquid system, (2) that the two-phased system weighs less

than the pumped liquid system, which means lower cost to transport the system to orbit,

and (3) that the radiator area is less for the two-phased system, which means the assembly labor costs will be lower.

The two systems compared are given by the pumped Freon-11 system of figure 2.4-6 and

the pumped two-phased water heat transport system of figures 2.4-3 and 2.4-4.

The complexity factors were compared using the RCS PRICE modelling technique and

the result came out $21.26M for the liquid and $16.08M for the two-phased, which results

in $5.18M in favor of the two-phased system.

The transportation costs were calculated using $718 per pound to orbit and the difference in system weights. This resulted in $2.66M in favor of the Iwo-phased system. The

assembly costs were based on $77,000 per 24-hr day for astronaut time and the assessment that was used in the last study of 8-labor hours to assemble 100 square feet of

radiator. This resulted in a $475,000 saving for the two-phased system.

The cost of advancing these technologies has been estimated at $0.8M for the heat exchanger program and $2.59M for advancing the two-phased water interior loop system

(assuming use of shuttle test data for heat pipes rather than a complete independent

AL

55

r Itb
^.a

(3allGi 9AL

Q

D180-27935-1

OF Proon

e

^T+ RADIATOR

125 KW

S035 FT2 (ONE SIDE)

9642 LOS (PANELS)

462 LOS HX

1.78 INCH ID 003 INCH WALL

54 PSID

440 WATTS

300 FT LENGTH

532 LOS

7.5 PSI D

602 WATTS

f

ri

I'll

r^

$.0 LOS

OS PSID

7.5 WATTS

8011F EQUIPMENT

GOLD PLATE 850F,10 KW

22.86°F

1S PSID

1470 WAT'T'S

32°F 32°F

49.5 LBS BATTERY

0.6 PSID COLD PLATE

47 WATTS 400P,20 KW

42.5 LOS

94 PSID 688 WATTS

SGOF 32°F

PRESSURIZED

n 82.50 F

MODULE

INTERFACE o

3400 F

83.34°F HEAT EXCHANGER 35.34°F

11 KW

977 PSID 24.4 LOS 47.8 WATTS 8.6 PSID 23.2 WATTS

EQUIPMENT COLD PLATE 11.3 LOS 6.4 LOS

HUMIDITY CONTROL

850F,10 KW 4.0 PSID 2.3 PSID

10.8 WATTS 6.1 WATTS

UNIT

400F,1 KW

3970°F

0.457 INCH ID I 0.02 INCH WALL 50 FT LENGTH

9 LBS T

2.75 PSID

745 WATTS TOTAL

EQUIP 11,343 LOS

POWER 1710 WATTS

TOTAL 11,941 LOS

Figure 2.¢6 Pumped Liquid Freon-11 System Schematic

56
D180-27935-1

#light test). Together these represent an expense for technology advancement for a twophased heat transport system of $3.4M.

Using the above figures the cost over benefit ratio of advancing technologies to support

the two-phased heat transport system is 0.41. This is based on the $3.4M advancement

cost divided by $8.32M benefits.

2.4.5 Conclusions and Recommendations

The study results show that a pumped two-phase heat transport system provides some

weight, power, and size reductions compared to a pumped liquid loop system. The twophase system also offers greater flexibility in configuring the space station.

A capillary two-phase heat transport system offers the advantages of a pumped twophase system with a relatively small weight increase. The capillary system does not

need the pumps, valves, and controls needed for the pumped two phase system. Consequently a capillary system is, in principle, a more reliable system.

A two-phase water heat transport system for pressurized modules provides an additional

weight savings when used with a two-phase main transport system. A capillary twophase water system would provide increased reliability and reduced vibration and noise.

Alternative pumping concepts for the pumped two-phase system were considered briefly.

One concept uses an osmotic pump in place of the baseline mechanical pump. This concept provides pumping by osmotic pressure that causes solvent to flow through a semipermeable membrane into a solution that flows to the evaporator. This concept requires

auxiliary mechanical pumps to keep the solution from being diluted next to the membrane. The weight, reliability, and performance deficiencies of this concept eliminates

it from serious consideration as an alternate pumping scheme. The other concept considered was an ion drag pump that produces fluid flow by creating ions in a corona discharge. The ions are accelerated in an electric field and impart momentum to the fluid.

This scheme has the advantage of pumping with no moving parts. However, the pumping

efficiency is only about 10%, high voltages are required, transport fluid must be a dielectric, and the corona discharge may have degrading effects on the fluid and electrode.

The results of this study showed that the weight of a two-phase heat transport system is

approximately 1200/lbm less than that of a comparable single-phase system of identical

L;

57
i

DISO-27935-1

capacity. This 12% lower weight alone would probably not be sufficient justification for

the selection of a two-phase system for the space station. The most compelling reasons

for the choice of a two-phase transpert system are (1) flexibility in locating heat loads

and reconfiguring experiments, (2) modular growth of the station, and (3) stable temperature interface with cooling and heating loads over a wide range of operating

conditions.

The two-phase system concept, however, has some inherent technical risks that will

require expensive space flight testing to resolve. The developmental costs of the twophase system would therefore be expected to be considerably greater than the cost of

developing a single-phase system.

Additional information is needed before a sound decision can be made as to which thermal transport system should be selected for the initial space station. It is therefore

recommended that a program be initiated to generate the necessary information to support the selection of a space station thermal transport system. A three step program is

envisioned. In the first step, system requirements would be established. These requirements would stem from the definition of: (1) system loads such as experiments, equipment, etc., (2) planned space station evolutionary growth, and (3) space station mission

planning.

Candidate single- and two-phase transport systems would be designed and optimized in

the second program step. These systems would be developed for a baseline station and

mission drawn from the step one requirements definition study. Dollar cost benefits of

each transport concept would be quantified for all important system attributes including,

a. Mass.

b. Size.

c. Flexibility/growth.

d. Reliability.

e. Maintainability.

f. ConstructabiIity.

g. Operation costs.

In the third step, detailed plans for transport system development would be prepared.

Developmental costs would then be predicted and a cost and benefit analysis performed

to identify the best thermal transport system concept.

58
DISO-27935-1

Regardless of the final selection of the thermal transport system concept for the space

station, the potential benefits of the two-phase system warrant immediate technology

development. Such developments are necessary to bring the level of technical maturity

up to the point required for space station preliminary design. Because a pumped twophase thermal bus system development program is currently in progress under NASA JSC

contracts NAS9-16781 and NAS9-16782, it is recommended that emphasis should be

placed on development of a two-phase transport loop suitable for thermal management

within pressurized inhabited environments of the space station. The high performance

fluids (ammonia or freon) envisioned for use in the main thermal transport bus cannot be

used in inhabited areas due to their toxicity. Water would be the first choice for the

working fluid in the internal transport loop. A two-phase design would provide the flexibility, modular growth capability, and isothermal interface characteristics desired for

the overall thermal management system. Both mechanically pumped and capillary

pumped loops should be investigated. Special emphasis should be placed on developing

pump and heat exchanger technology that would benefit both the main thermal bus and

internal transport loop concepts. In addition, capillary pumping for the main thermal

transport system should be investigated because of the potential for increased reliability

and reduced power, noise, and vibration by eliminating mechanical pumps.

2.4.6 Technology Advancement Plans

Recent developmental studies for long-life thermal control systems have identified some

problem areas in the use of pumps on two-phase systems. This technology deve'opment

plan has been derived to study and resolve those problems to bring pump technology to a

state of readiness for a new start on the Space Station program. Figure 2.4-7 and table

2.4-2 provide schedule and resource planning information for the pump technology

advancement.

Most two-phase thermal control concepts derived for application to the current modular

manned space station have characterized two kinds of fluid loops. The bus loop most.

often uses a toxic working fluid like freon and ammonia because they have good thermal

properties. However, for safety reasons, this loop is constrained to avoid exposure to the

pressurized living spaces. For those areas, a water loop is suggested for heat transport.

The device, which will exchange beat between the two systems, is the subject of the

second thermal management technology plan and the schedule and resource plans are

given by figure 2.4-8 and table 2.4-3 respectively.

59

^R. 32 .

^WIV
..1.

YEARS FROM ATP

TASK 1 2 3 4 5

MILESTONES a 0

1) DESIGN REQUIREMENTS

DEFINITION

Z) DESIGN EVALUATION AND

OPTIMIZATION TRADE STUDIES

3) IDENTIFY CRITICAL TECHNOLOGY

ITEMS

4) CRITICAL TECHNOLOGY ITEMS

CONCEPT DEVELOPMENT

5) COMPONENT OPTIMIZATION

AND DESIGN

6) FABRICATION AND TEST

7) FABRICATION OF NON-CRITICAL

PUMP PARTS

8) VERIFICATION TESTS

9) ASSEMBLY OF PUMP PACKAGE

10) PERFORMANCE TEST OF

INTEGRATED DESIGN

m0

I'

O 0

z^.

C_

r^

d

w0

NV%DW

A REQUIREMENTS REVIEW 0 DESIGN REVIEW ' O FINAL REVIEW V SPACE STATION IOC

Figure 7,4-7 Schedule for Two-Phase Thermal System Pump Advancement Program

Nft
::::YEARS FROM ATP

TASK

1 2 3 4 5 TOTAL

1) DESIGN REQUIREMENTS 15.7 18.7

DEFINITION

2) DESIGN EVALUATION AND 62,5 522,5

OPTIMIZATION TRADE STUDIES

.3) IDENTIFY CRITICAL 4.2 42

TECHNOLOGY ITEMS

4) CRITICAL TECHNOLOGY ITEMS 18.8 98.8

CONCEIT DEVELOPMENT

5) COMPONENT OPTIMIZATION 50 50

. AND DESIGN

6) -FABRICATION AND VEST 200 200 400

7) FABRICATION OF NUN- 45 100 45 190

CRITICAL PUMP PARTS

8) VERIFICATION "PESTS 22.5 225

9) ASSEMBLY O

(

F

7

PUMP PACKAGE 36K 35

10) PERFORMANCE TEST OF 210 70 280

INTEGRATED DESIGN

TOTAL 197.2 Soo 267.55 248 70 1479.7

m

0

r

Do

0

V

w

r

nZ

Tr F3 ®-

[4d a

1

RQ

Table 24-2 Resources for Two-Phase Thermal System Pump Advancement Program

I
YEARS ATP 2 3 4 5

TASK

MILESTONES p 13

1) DESIGN REQUIREMENTS

DEFINITION

2) DESIGN EVALUATION AND

OPTIMIZATION TRADE STUDIES

3) IDENTIFY CRITICAL

TECHNOLOGY ITEMS

GN 4) CRITICAL TECHNOLOGY ITEMS

CONCEPT DEVELOPMENT

5) COMPONENT OPTIMIZATION AND

DESIGN

6) FABRICATION AND TES'

7) FABRICATION OF NON-CRITICAL

HEAT EXCHANGER FART S

8) VERIFICATION TESTS oil

9) ASSEMBLY OF HEAT

EXCHANGER

10) PERFORMANCE TEST OF

INTEGRATED DESIGN

A REQUIREMENTS REVIEW O DESIGN REVIEW O FINAL REVIEW V SPACE STATION 10

Figure 24-8 Schedule for Heat Exchanger Technology Advancement Program

0

ao

0

.:AI Lo-
DEARS FROM ATP

TASK

1 2 3 4 TOTAL

1) DESIGN REQUIREMENTS DEFINITION 1 6.7 16.7

2) DESIGN EVALUATION AND 62.5 62.5

OPTIMIZATION TRADE STUDIES

3) IDENTIFY CRITICAL TECHNOLOGY 4.2 4.2

ITEMS

4) CRITICAL TECHNOLOGY ITEMS 18.6 182

CONCEPT DEVELOPMENT

6) COMPONENT OPTIMIZATION AND 66 so

DESIGN

6) FABRICATION AND TEST 200 100 300

7) COMPONENT INTEGRATI ON INTO

HEATEXCHANCER

8) FABRICATION OF NON -CRITICAL 45 57.5 1022

HEAT EXCHANGER PARTS

9) VERIFICATION TESTS 22.5 22.6 46

10) ASSEMBLY OF HEAT EXCHANGER 60 60

11) PERFORMANCE TEST OF ISO 8D07

INTEGRATED DESIGN

TOTAL '107.2 21 982.5 160 •E^3.7

mw

0

00a

N

.aw

X

0

0

ro

C

P^

3=j

t isd

Table 24-3 Resources for Neat Exchanger Technology Advancement Program

NZ
ILAL

DISO-27935-1

The application of two-phase thermal management subsystem in pressurized modules of

the space station configuration is the third technology for advancement in the thermal

management area. Reliability and performance are key objectives for the development.

Figures 2.4-9 and table 2.4-4 give the schedule and resource information respectively.

64

i
YEARS FROM ATP

1 2 3 4 S 6

TASK

MILESTONES v 0 O a

1) SYSTEM REQUIREMENTS

2) PRELIMINARY DESIGN

3) TECHNOLOGY READINESS

ASSESSMENT

4) COMPONENT DESIGN,

FABRICATION, AND TEST

5) TEST BED DESIGN

6) TEST BED FABRICATION

AND OPERATION .

7) FLIGHT TEST UNIT DESIGN

8) FLIGHT TEST ASSEMBLY

AND INTEGRATION

9) FLIGHT TEST 0 G

10) TEST EVALUATION AND

DESIGN UPGRADE

V REQUIREMENTS REVIEW 0PRELIMINARY DESIGN REVIEW 0CRITICAL DESIGN REVIEW

q FINAL DESIGN REVIEW A FLIGHT TESTS

Q^

l^

0

00OINV

^O

W

I

on

T0'

O rw

C

rFigure 2.4,9 Schedule for Two-Phase Water Interior Loop Technology Advancement Program

i ^

f
rn

Table 2.4.4 Resources for Two-Phase Water Interior Loop Technology Advancement Program

^•..^,^ ARS FROM ATP

TASK

1 2 3 4 TOTAL

FIGURES IN $1000 (1083)

1$ SYSTEM REQUIREMENTS 100 100

21 PRELIMINARY DESIGN 180 180

31 TECHNOLOGY READINESS 10* 10

ASSESSMENT

4) COMPONENT DESIGN, FAI3, 240 00 301)

AND TEST

6) TEST RED DESIGN 200 200

0) TEST BED FABRICATION SOD 400 low

AND TEST

7) TEST EVALUATION AND 810

DESIGN UPGRADE

TOTAL 280 250 1070 loco 2600

NOTES:

HEAT EXCHANGER FROM OTHER TECHNOLOGY DEVELOPMENT PROGRAM ASSUMED TO BE USED IN

TEST BED. DEVELOPMENT COSTS OF HEAT EXCHANGER MODEL NOT CHARGED TO THIS PROGRAM.

.E

0Q

n

0

000

ivVWtas

r, CIS]

E5
IbL:; f AD

DISO-27935-1

2.5 INTEGRATION OF AUTOMATED HOUSEKEEPING

This study was conducted to characterize a system for integrating the automation of

several housekeeping subsystems on an lFhabited space station. This integration system

will be a step toward meeting the autonomy/automation philosophy for the space station

that was defined by the Concept Development Group (see table 2.5-1).

In a study completed in early 1983, the cost versus benefits of integrating the automation of several utilities producing subsystems on a space station was assessed. The

results of this assessment indicate that the function of providing this Integration could

produce savings to the space station over a I0-year life of $184M. The same study indicated that a large part of the cost of such a system would be the software development

and the probable use of expert systems technology. These cost figures were assessed as

being about $9M. Because the system had not been described at a detailed level and

because the cost and benefits were impressive, it was decided to conduct the current

study to take a more detailed look at the functions of such a controller. The current

study also produced a reassessment of the cost and benefits of the system and generated

a more definitive identification of the applicability of expert systems to the process.

2.5.1 Approach

The objective of this study was to obtain a characterization of the integrating management controller to allow a better understanding of the benefits possible and the technology needed for implementing such a controller so that it will provide reliable, realtime management of the separate housekeeping controllers on a space station. To

accomplish this objective, the results of the initial study were extended by a more

detailed modeling of how a management type controller might be employed. The model

was then examined to identify options in the implementation that better defined the

benefits to be obtained from the integration process.

In performance of this task a system analysis was conducted to update the following list

of functions to be performed by each of the three automatic housekeeping subsystem

controllers:

67
D180-27935-1

w

Table 2.54. Space Station Autonomy/Automation Philosophy

Subsystem/system monitoring and control will be performed onboard.

Systems monitoring and control will be automated.

Fault detection and isolation will be an automated function for all subsystems.

Redundancy management including reconfiguration will be performed automatically

onboard.

Reverification of systems/subsystems elements will be performed automatically on

board.

Operations planning and scheduling will be performed onboard.

The degree of automation will increase as the space station grows and technology

becomes available.

Collection and analysis of trend data will be automated.

The space station platform shall have the same degree of automation onboard as the

manned base.

68

z
D180-27935-1

Table 2.5-2: Functions For Housekeeping Controllers

L w

F

Electrical Power Thermal Life Support

Control voltage at power Control temperature to Control oxygen and

user outlets. set points within cabins. nitrogen supplied to

cabin.

Control power levels at Control temperature at Control contamination

power user outlets. heat exchangers for levO in cabin air.

specific equipment items.

Switch sources based on Control humidity of cabin Control quality of potable

sensed status of sources atmosphere. and wash water.

Removal of CO2 from

cabin air.

The above table indicates the starting point on independent control functions within each

of the three housekeeping subsystems on the space station considered in this study.

These functions are those that relate to maintaining the environment on the space station for the crew and for the mission-peculiar equipment. The list was expanded for

models of the three subsystems to the level of detail where the control parameters would

be sensed.

A systems analysis was performed to develop a concept for integrating the control of the

three housekeeping functions and to identify the control parameters.

Based on the interactions identified, functions were defined for the integrating controller. Functional block diagrams were then developed along with functional descriptions of

each of those defined.

Because various mode shifts would be selected and implemented by an integrating controller, it was necessary to identify the mode shifts and to assess the sequencing of the

action. The scenarios for operation of an integrating controller were conceptualized in

this subtask by a systems analysis approach:

A systems analysis was then conducted for an integrating controller for automated

housekeeping functions in cooperation with data management specialists to identify

hardware and software elements of a concept and to isolate technologies to be considered for advancement in order to implement the concepts. The use of artificial intelligence in the form of expert systems was explored to implement the flexibility and

-tolerance for change needed in this integrating controller.

69
''

D180-27935-1

2.5..2 Technical Discussion

The automation of three subsystems on an inhabited space station was investigated to

identify the functions to be performed and the sensing that would be needed. The three

subsystems were electrical power, life support, and thermal management. The automation being considered is that which would be used internal to each of these subsystems

to enable them to perform their functions automatically. The integration of these automated systems deals with interactions between them, with outside factors which affect

them all, or with trends that involve more than one subsystem.

Tables 2.5-3 through 2.5-5 show the results of analysis conducted of these subsystem

concepts and lists the functions and sensed quantities for the automations identified.

The functions and sensed quantities in these tables were then used to construct an interface tabulation (see figure 2.5-1) to identify when interactions between the automated

subsystems could exist and where outside events could influence the overall operation.

These identifications lead to the definition of functions for the Integrating controller.

The integrating controller is a concept that is intended to provide management level

control of automated utilities subsystems on a manned space station. Initially this controller would be largely an advisory service for the astronauts. As such, it would tend to

replace the advisory service that has been provided by mission control with a more autonomous 'interactive system that the astronauts can use on board. Because there will be

actions that will be repetitive and bothersome to the astronauts, it is a worthy goal to

seek a fully automatic integrating controller for some functions.

Based on the interactions shown by figure 2.5-1, it is clear that the three subsystems

affect each other significantly and that there are outside factors that affect them all.

The functions performed by an integrating controller would then deal with those interactions, as shown by figure 2.5-2. Inspection of these indicate the following:

1. Electrical power load management is needed because both thermal and life support

are heavy power users and reduction of their usage to balance loads needs to consider their interacting functions.

70
DISO-27935-1

TABLE 2.5-3

ELECTRICAL POKIER SUBSYSTEM AUTOMATION

Functions

o Control solar array orientation

o Control of solar array selection - segment selections

o Regulation of solar array output voltage - shunt regulation

o Control of battery charge-discharge processes

o Battery selections - cell selections

o Load sharing control of regulators

o Shunting for under use control

o Redundancy Management within the electrical power system

Sensed Quantities

o Solar array temperatures

o Solar array positions

o Solar array voltages by sections of the array

o Battery cell voltages

o Battery cell temperatures

o Battery cell pressures

o Battery charge voltage

o do/dc converter line voltage

o Transformer coupled converter output voltage

o Series resonant inverter (dc/ac) output voltage

o Series resonant inverter fuse status

o Magnetic latching relay position

o Cable temperature

F

71
D 1 SO-27935-1

TABLE 2.5.4

LIFE SUPPORT SUBSYSTEM AUTOMATION

02 Generation

Functions

o Control of the flow of water to the electrolysis units

o Valve operation

o Pump operation

o Control of electrolysis current

o Control of the flaw of H2 away from the unit

i o Valve operation

o Control of the flow of water away from the unit

o Valve operation

o Pump operation

o Control of the flow of oxygen away from the unit

o Valve operation

o Redundancy management within the 02 generator

o Detection of failure

o Abnormal values of several quantities

o Selection of redundant elements; generators/pumps/valves

Sensed Quantities

o Partial pressure of cabin 02

o Flow rate of input water

o Pressure of H2 at output

o Flow rate of water at output

o Pressure of 02 in storage at output

o Selected set point condition

o Status of valves, pumps, generators and storage units

72
C

D180-27935-1

TABLE 2.5-4 (Continue)

LIFE SUPPORT SUBSYSTF-M AUTOMATION

N2 Supply

Functions

• Control of the flow of N2 from storage

o Valve operation

• Redundancy management functions within the N2 supply

o Detection of failures

o Abnormal values of several quantities

o Selection of redundant valves

Sensed Quantities

o Cabin pressure

o Pressure of N2 storage tanks

o Selected set point

o Status of valves and storage tanks

CO2 Removal

Functions

• Position of by-pass valves to control air flow to beds

• Position of by-pass valves to isolate beds for desorption from the cabin

• Control of electric heaters to create steam to flow through beds being desorbed

• Control of valves to direct CO2 to the reduction system from the beds being

desorbed

• Control of valves to provide hygenic water for steam into desorbed beds

• Redundancy management

• Detection of abnormal sensed values

• Selection of redundant elements: fans, by-pass valves, beds, and steam

generators

73

iR .
74

D180-27935-1

f—.A-Y I

TABLE 2.5-4 (Continued)

LU^E SUPPORT SUBSYSTEM AUTOMATION

Sensed Quantities

o Partial pressure of cabin CO2

o Flow rate of water at input to steam generator

o Pressure of CO2 in accumulator at output

o Temperature of steam in steam generator

o Flow rates at de-sorbed bed

o Status of beds being used for absorption and being desorbed

o Status of valves and fans

o Selected set point

CO2 Reduction

Functions

• Mixing of H2 and CO2

• Flow of mixed CO2 and H2 through filter to the reduction unit

• Pump and valve control for water accumulator at reduction unit output

• Redundance management within the CO2 reduction unit

• Selection of redundant el mentse reduction unit, valves, and accumulator

• Failure detection based on abnormal sensed values

• Cooling for unit

Sensed Quantities

• Flow and pressure of gases at input

• Temperature of unit

o. Flow and pressure of gases at output of unit

o Flaw of water to accumulator

o Capacity filled with water in accumulator

o Flow of water out of accumulators

o Status of valves and accumulators
U acv j.

DISO-27935-1 a

TABLE 2.5-4 (Continued) r,^

LIFE SUPPORT SUBSYSTEM AUTOMATION

Trace Contamination Control (TCC)

Functions

o By-pass valves to control air flow through beds

o Annunciation of below normal bed status

o Control of power to electric heaters

o Redundancy management within the trace contamination control system

o Failure detection based on abnormal sensed values

o Selection of redundant elements: alternate fans, paths through beds, and

oxidizer

Sensed Quantities

o Level of contamination

o Temperature of oxidizer

o Flow through units

o Status of fans, valves, oxidizer heater and beds

o Selected set point

Potable Water Process

Functions

• Control of water flow to post-treat

o valves

o pump

• Control of cycling in past-treat and Water Quality Monitor (WQM)

• valves

• pumps

• WQM processes

• Control of flow to selected storage tank

• Control of iodine addition in storage 'tank testing process

o Control of overflow to hygienic water

o Control of water heater

o Control of use flow out of storage tanks

75
L +$`^' p' III

D180-27935-1 r,^

TABLE 2,5-4 (Continued)

L11"E SUPPORT SUBSYSTEM AUTOMATION

Functions (Cont)

o Redundancy management with the potable water processor system

o Failure detect

o Seclection of redundant elements: accumulators, water duality monitors,

(WQM), tanks, valves, and beds

Sensed Quantities

• Capacity filled In accumulators

• Measured contaminants in WQM

o Capacity filled in storage, test, use tanks

• Iodine level in storage tank test processing

• Post treat valve and bed status

• Water temperatures in system

• Storage tank valve status

• Water flow rates in system

Hygenic Water Process

Functions

• Control of pre-treat pumping

• Control of pre-treat biopal VRG 20 addition

a Control of p-n aping and valving into the vapor-compression distillation (VCD) unit

• Control of compression in VCD

• Control of heating in VCD

• Control of conductivity testing of VCD condensate and valving for output

• Control of post-treat valving and pumping

• Control of WQM processes

• Control of flow to fill-use tanks

• Control of flow out of fill-use tank

76
D180-27935-1 a'

TABLE 2.5-4 (Continued)

LEFE SUPPORT SUBSYSTEM AUTOMATION

Functions (Cont)

o Redundancy management within the hygenic water processor system

• Failure detect

• Select redundant elements: INQM2 VCD, valves, fill tanks, pumps and heaters

Sensed Quantities

o PH level in pre-treat

o Flows in pre-treat

o Waste holding tank capacity filled

o Valve status indicators

o Waste tank capacity filled

o Sludge tank capacity filled

o Flows into VCD

o Pressure in VCD

o Temperature in VCD

o Conductivity of VCD condensate

o Flow of condensate from VCD

o Measured contaminants in WQM

o Post treat valve and bed status

o Flow rates in post treat and storage

o Storage tank valve status

o Capacity filled in storage tanks

o Capacity filled in accumulators in system

Wash Water Process

Functions

o Control of pumping to work holding tank

o Control of pumping and valving to hyper-filtration process
DISO-27935-1

TABLE 205-4 (Continued)

LIFE SUPPORT SUBSYSTEM AUTOMATION

Functions (Cont)

o Control of heating in hyper-filtration process

o Control of valving and pumping from the hyper-filtration process

o Control of. the addition of sodium hypochlorite in post-treat

• Control of the addition of iodine in post-treat

• Control of pumping and valving for post-treat

• Control of pumping and valving for storage of wash water

• Redundancy management within the wash water processor system

o Failure detection

o Selection of redundant elements: pumps, valves, hyper-filtration units, and

tanks

Sensed Quantities

• Flows to and from holding tank

• Flows to and from the hyper-filtration processor

• Temperature of hyper-filtration processor

• Capacity filled in holding tank

• Capacity filled in hyper-filtration process

• Measured contaminants in WQM

• Post-treat valve and bed status

• Flows for post-treat and to storage

• Storage tangy _ valve status

• Capacity filled in :storage tanks

• Quantity of iodine and sodium hypochlorite available for use

• Capacity filled in sludge tank

78
D180-27935-1

TABLE 2.5-5

t THERMAL CONTROL AUTOMAnON

Functions

• Control of cabin air flow through heaters

• Control of heaters

• Control of heat exchanger condensate flow to separators

• Control of water flow out of separators

• Control of positions of seeerable radiators or selections of selectable radiators

• Control of coolant flow - valve positions or pump speeds

• Redundancy management within the thermal control system

• Sensed :Failures from abnormal sensor values

• Selection of redundant elements: fans$ heaters, heat exchanges, separators,

pumps, and valves

Sensed Quantities

• Temperature of cabin air

• Humidity of cabin air

• Input air flow to heater

• Condensate flow at heat exchanger

• Water flow out of separators

o Air flow out of separators

• Heater temperature

• Set point status

a Equipment status

o Position and rate information for steerable radiator servos

o Valve positions

o _ Pump speeds
®0

A'w'.t•

1

D180-27935-1

FIGURE 2.5-1

TABULATION OF INTERFACES BETWEEN HOUSEKEEPING FUNCTIONS

^ p

INTERFACE BETWEEN THERMAL AND LIFE SUPPORT

• Temperature of cabin air

• Mmizdry of cabin air air to Iife support

• Water flow out of separators (water to life support)

• Air flow out of separators (air to life support)

OUTSIDE FACTORS WHICH EFFECT HOUSEKEEPING

o Lig itside/Darkside

• Electrical power solar arrays

• Thermal radiators

• Outside lighting

• EVA constraint

o Crew size and level of

o Life support load

a Load on electrical power

a Elargy input to thermal

o Moisture input to thermal

o Distribution of life support materials, power loads, and

thermal loads

o Compliment of Experiments

• Load on electrical power

• Load an Iife support materials

• Constraint on dumping of waste

• Thermal/humidity input

• Distribution of life support materials, power leads, and

thermal loads

o Shuttle Docked or Away

• Air mixing between shuttle and station

• Possible extra crew

• Possible power sharing considerations

• Passible thermal sharing considerations

o EVA or not

• Extra load an life support before and after

• Less load during

o Maintenance

• }stem s utdowns while need for functions continues

• Effect of maintenance an variations in performance of

systems

• Effect of maintenance an crew activity - EVA

INTERFACE BETWEEN ELECTRICAL AND THERMAL

• Battery cell temperatures

• Cable temperature

• Control of heaters (power usage)

• Shunting of power (generates thermal load)

INTERFACE BETWEEN ELECTRICAL AND LIFE SUPPORT

o Control of electrolysis current (power usage)

• Control of electric heaters to create steam to flow through beds being

desorbed (power usage)

• Control of power to Trace Contamination Control Heaters (power usage)

o Control of heating in VCD (power usage)

00 o Control of heating in hyper-filtration process (power usage)

0

o Control of water heaters (power usage)

t'

l
INTEGRATING CONTROLLER

0

r

O

iN

V

',nW

i

-0

O ^r

ANNUNCIATION COMMAND INPUTS

AND DATA (ASTRONAUTS

DISPLAYS OR GROUND)

MAINTENANCE MANAGEMENT COMMANDS

AUTOMATED MODE SELECT

ELECTRICAL REDUNDANT PATH SELECT POWER

SUBSYSTEM POWER SUPPLY DATA FAILURE STATUS, MODE

STATUS, PERFORMANCE PARAMETERS

THERMAL CONTROL EMERGENCY FOR BATTERIES & FUNCTIONS ELECTRONICS AND ALARMS

FAII.'.JRF STATUS POWER USE DATA, AND

PERFORMANCE PARAMETERS

MAINTENANCE MANAGEMENT CMDS

AUTOMATED MODE STATUS 00 THERMALCONTROL

SUBSYSTEM

4- REDUNDANT PATH SELECT

POWER USE COMMANDS

ELECTRICAL

POWER AND

DEMANDS

AIR AND WATER TEMPERATURE

AND CABIN HEAT EXCHANGES

POWER USE COMMANDS

MATERIALS TRANSFER COMMANDS

AUTOMATED LIRE 4

MODE SELECT

SUPPORT REDUNDANT PATH SELECT

SUBSYSTEM MAINTENANCE MGT COMMANDS

POWER USE DATA, MATERIALS

STORAGE LEVEL DATA, FAILURE STATUS

MODE STATUS, AND PERFORMANCE

PARAMETERS

Figure 2.5-2 Werfaces Between an Integrating Controller and Automated Housekeeping Subsystems

C 7.

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I O
D I SO -27935-1

2. Materials transfer management is needed because outside factors affect the location of needs as well as the location of the availability of life support materials

around the space station. In many cases transfers need to be considered against

scheduled events and against dumping constraints as well as impacts on power and

thermal loading.

3. Intersubsystem failure isolation is needed because failure diagnosis outside of subsystem boundaries will have to be conducted in order to trace the cause through

the interacting functions. For example, an apparent failure of the separator in the

thermal or humidity control system could be caused by an actual fallure in the

Water Quality Monitor (rWQM) in the life support which is producing a backup into

the accumulator receiving the condensate from the separators. In this case failure

isolation within a subsystem would not be sufficient to find the problem.

4. Intersubsystem redundant path selection is needed because selection of redundant

paths in response to failures or maintenance shutdown will have to consider the

impact on interacting subsystems.

5. Maintenance schedule management is an integrated function since changes to the

timing of maintenance actions for one subsystem can have affects on the operation

and maintenance of other subsystems. This is because maintenance may cause

temporary shutdowns and may result in changes in performance of the maintained

subsystem which affect others.

G. Start-up integration is needed to control the interdependent sequencing of bringing

subsystems on line so that outputs are available before the need is created.

Figures 2.5-3 thru 2.5-8 give functional diagrams for these six functions.

Scenarios, for initialization of a space station system and for a shift in life support

modes on a space station, were developed to describe the operating environment for the

integrating controller.

An initialization scenario is to describe events that might occur as a space station

module is initialized for habitation by the crew. It is assumed that the shuttle is

attached and that the crew relies on the shuttle systems to support the initial EVA. As

82
i

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D180-27935-1

r^

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ORIGINAL PAGE TO

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Figure Z 5-3 Functional Block Diagram for Electrical Power I-oad Management

by an Integrating Controller

83
NO---4.1 TTp

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Figure 2,5-4 Functional Block Diagram for Materials Transfer Management by an Integrating Controller

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Figure 2.6-5 Functional Block Diagram for Inter-Subsystem

Failure Isolation Using Integrating Controller

ANNUNCIATE d

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Figure 2.6--6. Functional Block Diagram for Inter-subsystem Redundant Path Selection

i

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9

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Figure 2'.5-7 Functlonal Black Diaeram for Mafntanance Schedule Management by an lntagrating Ccntroflar

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Figure 2.3-8 Functional Block Diagram for Startup Integration

by an Integrating Controller
89

I.

DISO-27935-1

can be seen, no attempt is made to work out the specific number of orbits for this process. The initialization crew will start out using EVA and then will go to shirt sleeves

after orbit L. The initialization crew would be two or possibly three astronauts and

would be joined by the remainder of the crew after orbit W.

Orbit

(1) Close cabins and establish initial atmosphere N

(2) Cabin power available N + M

(3) Cabin heat exchangers N+M+1 = L

(4) Cabin Trace Contamination Control (TCC) on N+M+1 = L

(S) Cabin dehumidifiers on N+M+1 = L

(6) 02 generators on L+R = Z

(7) N2 supply opened L+R = Z

(S) Cabin air heaters on L+R = Z

(9) CO2 removal on Z+1

(10) CO2 reduction on Z+2

(11) Crew begins cabin occupancy Z+S = W

(12) Potable water loop on Z+S = W

(13) Hygienic water loop on Z+S = W

(14) Wash water loop on Z+S = W

The mode shift sequence is the result of a change in the life support subsystem operating

mode between the nominal, degraded, or emergency set points. Again this is a conceptual sequence of events to be described more specifically after the space station design

becomes more defined.

1. Mode change selected either by crew or the integrating controller.

2. The integrating controller then adjusts control limits for each automatic

system reference to correspond with selected mode.

3. System configured for mode shift as necessary by commands from the integrating controller.

a. Materials transfer

b. Power Adjustments

C. Path Selection

4. Maintenance schedule adjusted as needed.

S. Annunciation to crew.

11
"W1" - A

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Dl$0-27935-1

d. Implement mode shift.

An integrating controller will consist of onboard central and distributed processors that

will initially be supported by an earth-based central data processing facility, which can

be used by employing the telemetry link. The processing functions will be largely in the

onboard central processor for all decision making and command generating. The distributed processors will be used for data collection and command execution functions.

The earth bound facility will be used for some off line comparisons and determinations,

especially for failure diagnostics and logistics control. Figure 2.5-9 shows a typical processor hierarchy and data path connection concept for a integrating controller. The

diagram indicates where the functions are in the central processor and where they are

distributed.

The following functions of the integrating controller are indicated to be definite candidates for some expert systems processing.

1. Electrical power load management - the MSFC has a study which is being

conducted by Martin Marietta and the indication from that study is that

expert systems apply to this function.

2. Redundant path selection - work is being done to apply expert systems to this

problem for nuclear power plants.

3. Maintenance schedule management - this general area is considered to be a

promising application of expert systems.

All of the other functions were considered by artificial intelligence specialists to be

good candidates for at least partial application of expert systems.

Any estimate of the size of the expert systems parts of an integrating controller is constrained by the following:

1. The preferred current method of developing an expert system is to use an expert

system language analogous to a programming language for conventional autornation. The number of statements in a conventional program can vary drastically

depending on the language. In the case of expert systems, there is probably at

least a 3:1 variation in number of rules depending upon the language used.

90

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Figure 2.59 Processing Functional Diagram of Integrating Controller for Automated Housekeeping

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2. Expert systems do not have to be developed using rules. Rules are a knowledge

representation technique. There are other ways of representing knowledge

including:

- Logic

- Networks

- Frames

- Hybrid

This is one reason why an integrating controller would involve several expert systems for

its different types of functions.

Given the above caveats, it was estimated that as an example, the intersubsystem failure

isolation function expert system would involve from 1,000-3,000 rules, and in that case

using rules for estimating is probably a good way to go.

Factors to consider when describing whether to use space borne or ground based computers for the integrating controller include;

1. Criticality—will the astronauts be threatened if access to the integrating controller is interrupted?

2. Resource usage—does the integrating controller use an excessive amount of space

borne computer resources?

3. Data bandwidth—does the integrating controller process so much data that transmitting it to earth would jug up the communications channels?

Because of the criticality of the failure isolation function and redundant path selection

function, they would be high priorities for space borne implementation. Maintenance

scheduling could probably be ground based at least in the early stages of the space

station.

In order to estimate the space borne computational capability required, several assumptions will be made:

I. The expert systems used will be programmed for the onboard system using the LISP

programming language. (LISP is a heavy user of resources).

V

92
^I

DISO-27935-1

2. The space station has a distributed processing system consisting of general purpose

as well as special purpose processors,

3. General purpose processors are machines with 32-bit CPUs, 2 MIPS throughput and

1 MB of memory.

4. Mass storage will be available to store expert systems rules when not actively

being processed.

Based on these assumptions, it is estimated that an expert system implementation would

require a general purpose processor for active processing of each expert system function

of the type exemplified by intersubsystem failure isolation sys-t..:m.

Any large expert system might require a special purpose processor, and unless the function was extremely critical for crew safety, it would not be space borne.

To estimate the effort needed to develop an expert system a single function such as the

failure isolation is estimated to require at least 5- 10 man-years of effort. Assuming one

expert system per function, 30-60 man-years of effort would be required. (Currently,

5 man-years seems to be the quickest any expert system can be developed).

All of thi,,, indicates that expert systems have a role to play in the integrating controller

concept, but that they are, when based on current technology, heavy users of computational resources and development effort.

2.5.3 Concept Trades

The results of the concept characterization studies for an integrating controller are

basically the definitions of functions to be per-farmed by such a controller, and concepts

for processing of those functions onboard the space station or on the ground using distributed as well as centralized architecture. This section discusses the comparisons

conducted with respect to these characterizations and the identification of technology

advancements needed.

Figure 2.5-10 gives a trade of the functions of the integrating controller against five

fairly nonquantif!able criteria.

93
TECHNOLOGY DISCIPLINE: INTEGRATION OFAUTOMATEDHOUSEKEEPING

TECHNO1.011YAD"NCER1ENT00AL: TO REDUCE COSTOF MAINTAINING THE HOUSEKEEPING FUNCTIONSOM A SPACE STATION WHILE ENHANCING

CREW SAFETY AND COMFORT.

SPECIFICTflAUE:COMPARESIX FUNCTIONS OFANINTEORATING CONTROLLERADAINSTCRiTERIA OF:

I USE FREOUERCY, INTERACTIVE SUPPORT, ESSENTIAL FOR SAFETY, 13ETERMIHISTiCPRDCES31HO AND DURABILITY.

OPTION11 OPTION2 OPTION 13PTION4 OPTIONS OPTIONS

TRADE NUMBER

OPTIONS DESCRIPTION ELECT. POWERLOA13MOT MATERIALSTRANSFERMOT INTEflSUBSYSFAILUPB INTERSUBSYS REDUNDANT MAINiERANUF STARTUP

ISOLATION PATHSEL SCHEOULERIGT INTEGRATION

FREQUENCY OFDSE OFTEN TQCONT1NUOUSBECAUSE OFTEN TD CONTINUOUS BECAUSE BECAUSE T}IEOCCUR R£NCkSDF YfDULDB£ USED INEARLY OCCASIONAL TDOFTEN THIS 

FUNCTION 

WO0LD8ECALlE

SPACE STATION ORDWS ' OFSPACESTATIONGROWTHAND FAILURES ARE SO-AEWHAT STATIO It AFTER OFTION 3 BECAUSE THE ADJUSTMENT OF UPMUCH ASTHE OPTION 3 AND

EXPERIMENTS CHANGESOPOWER EXPERIMENTAL CHANGES UNPREDICTABLE, 7EHSFUNCTION FUNCTION HAD BEEN USED. MAINTEHANCESCHEOULE DFAON4FUNCTIONSWOULDRE

UNBALANCES WILL POP UP ALSO THIS FUNCTION 19 nEEOSTQSECONTINUOUSLY LATERTHIS MIGHT BECOME COULD BE PUT OFFUNTILA CALLED UP. THIS FUNCTION.

FREOUENTLY. FAILURESALSO AFFECTED BY LOCATIONAL AVAILABLE BUT PERHAPS NOT AUTONG MOOS AND THEN IT GUIST PERIOD EXISTED FOR HOWEVER.WOULD NOT BEA

CAUSE UHBALANCEDPOWER CHAHOES AROUND THESPACE ON LIRE UNTIL THE SUBSYSTEM WOULD HE OR LINE. THE COMPUTER. LIKELY CANDIDATE FOR

USETDSUPFLY. STATION OF CREW OR FAI LURE isINOICATEO- CONTINUOUSLYASWOULO AUTOMATION - OCCASIONAL

EXPERIMENTS. OCCASICNALUSE- OPTION 3.

CONTINUOUSLY AVAILABLE

RANKING t t = ! 4 3

AUTONOWUS PROCESSING , ASTRONAUTSWOULOPROBABLY THISWOULD ALSO BE A GOOD EARLY ONTHISIVOULDIE AGAIN ASTRONAUTSWUULU ASTRONAUTSWILLWANT7I115 THISWILLIE KTERACTIVEAND

LIKE IRIS TOIEAUTONOMOUS CANDIDATE FOR AUTONOMOUS INTERACTIVE, ASTRONAUTS FROSABLY Pit EFERTHATTHIS TUItEIHTIRACTIVE. AST IDNAUT:PRUSABLYWILL

IMPLEMENTATION WOULD PRORAILYLIKETGAt EVENTUALLY S'EAUTOMATIC AOREEADViSED AFTER THE FACT WITHAM ADVISORY UUTPGT.

RANKING 1 1 2 2 4 3

ESSENTIAL FOR SAFETY THIS FUNCTION HAS A SOMMHAT RELATEO TO SAFETY , THIS FUNCTION IBAISOLUTELY THIS FUNCTION ISALLIOSTAS NOT PARTICULARLY RELATED IONEWAT RELATED TO

SECONDARY RELATIONSHIP TO

NEEDEDFURAC F$

ESSENTIAL ASOFTION3. TOSAFETY. SAFETY.

SAFETY BSYI EMS

RANKING 2 2 1 1 5 4

DETERMINISTIC PRO CESSIN13 HASA RELIANCE ON SOMEWHAT MORE GETERMINISTIC LARGELY KNOW41OW DAIED ABOUTTHE2AMEAS OPTION 3 TOM ONE WILL BEJUDGMENTAL THIS ONESHOULD BECOME

KNOWHOWAT LEAST FOR THAN OFT I AT FIRST-MAY BECOME BUT WILL ALLOW FOR MD RE UETERHHHSTICRATHER

EARLY SPACE STATION DETERMIRISTICIVITH FXPERIENCI DATA COLLECTIOHBECAUSE RAPID LY BUT USEWILL DROP

SAME AS OPTION} TIME FOR OECISIGNSI$GREAT OFFTOO.

RANKING 23 2

2 4

;

OUfl PROBABLY W1tLTAKEALONG 'LIKE IBXCEPTTHATTIMEFOR WILL 00AWAYSOONERTHANI SOMEWHATLESZVURAILE PROIAILYPNLLtIE TRILDNE SHOULD 00AWAY

TIME BEFORE THIS FUNCTION DECISIONSISGREATERSOMORE BECAUSEEFFONTWILLALtWAY2 THAN3 AROUNDASLON6AS FAIRLY RAPIDLY ONCE THE SPACE

WILLGOAWAY•-BECAUSE OF DATA CAN BE GATHERED IS GREAT TO ELIMINATE SPACE STATION It STATION SETTLESDOWNALITTLE

THE C}IANG INO STATION CRITICAL FAILU PZ MO DEB. EVOLVING

RANKING 1 2 3 4 3 1

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Figure 2,6-10 Trade of Integrating Controller Functions
DISO-27935-1

These comparisons indica-ce that the start-up integration and maintenance schedule management are of lower priority than the other four functions. This seems somewhat reasonable because the space station would need the first four for smooth and safe operation, while the last two would be more like convenience functions.

In general, trade on architecture favor a dirtributed system where the requirements for

computing capacity indicated by the function do not dictate extremely large units, which

would be practical to duplicate on board the space station.

The comparison of a fully automatic system versus one where the astronauts interact

thru a computer terminal involves human preferences. In many cases the astronauts

would prefer not to be bothered with routine diagnosis and corrective action but in

others such as scheduling and logistics the astronauts would want to maintain control. In

a few cases such as attitude control or some power control the diagnosis and corrective

action could require faster response than that which is consistent with human capability

and that would favor the fully automatic approach. Finally, the acquisition of a knowledge base to develop the integrating controller system will benefit by the interactive

experience of astronauts during the early missions. All of this indicates that the early

space station will be characterized by a great emphasis on interactive controllers but as

the station matures many functions will become fully automatic.

2.5.4 Cost and Benefits Analysis

Based on the integrating controller characterization developed in this study and the

trade study considerations identified above, an update of the cost and benefits for advancing the expert systems technology can be established. In section 4.1.8 of volume II of

the Advanced Platform Systems Technology Study Final Report, a cost and benefits

estimate was made for the expert systems technology for an integrating controller. In

the current study, we have developed a more detailed description of the functions of the

controller and have focused on the programmatic trades with respect to those functions

and that allows a more realistic estimate of costs and benefits.

The following assumptions are established for the cost update of this current study.

1. Six expert system functional elements plus one expert system selection element

will be considered.

95

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D180-27935-1

2. Each element is equivalent to one R1 expert system program (850 rules) except the

intersubsystem failure isolation element, which is assumed to be 2,000 rules (see

section 5.3.6). This gives a total of 7,100 rules for the integrating controller

expert systems.

3. Based on the productivity reported in section 5.3.6 1 each rule requires 2 days of

labor to develop. This is better than the productivity rate of 5 labor days per rule

used in the previous study. We will assume the more conservative 5 days per rule

rate.

4. Assume a labor rate of $400.00 per-man day for expert systems software development (this is nearly double the rate assumed for the last study).

5. Assume $IM for verification of each element for a total of $7M.

6. Based on the estimate of one general processor for each online function plus one

for the expert system selector, we can estimate that at least three onboard general

processors would be needed to implement the system. Assuming $IM for each we

have $3M for additional hardware.

Based on the above assumptions a cost figure for the expert systems development and

implementation is $24.2M. This includes approximately $12M for establishing flight

resident software and for a set of flight computers.

For the benefits estimate we will consider a phased introduction of the integrating controller expert systems. This means that the yearly savings assumed in the previous study

would be reduced.

The following assumptions apply to the benefits estimates for this study.

1. The labor to monitor the space station systems would be phased out as the integrating controller is phased in as follows:

a. For year 1: six ground-based mission controllers plus Yz time astronaut

(full coverage)

b. For year 2 thru 5: one ground-based mission controller plus Yz time

astronaut. (Reduction of five ground-base mission controllers for 4

years.)

C. For year "6 thru 10: 1/10 time ground-based mission controller plus 1/10

time astronaut. (Reduction of 5.9 mission controllers and 0.4 astronaut

for 5 years).

^/,

96

i

f,

1
DI80-27935-1

2. Mission controller labor rate is $1500 per 24-hour day or $550,000 per year for each

controller

3. Astronaut labor rate is $77,000 per 24-hour day or $28,2000 000 per year.

4. Resupply and maintenance cost savings due to the integrating controller are estimated as $25M over a 10-year mission due to more efficient use of resources

onboard and more managed maintenance operations.

5. Half of the above benefits of an integrating controller can be attributed to use of

expert systems.

Based on the above assumption the benefits of the expert systems part of an integrating

controller are estimated at $54.OM.

The resulting cost to benefits ratio then is 0.44. This is a significant movement from the

0.098 ratio estimate of the previous report but still leaves the expert system development with all the associated unquantified benefits as an attractive technology for

advancement.

2.5.5 Conclusions

The conclusion from this study are:

1. The integrating controller has real and useful functions on a space station.

2. The implementation of the controller would profit from expert systems

programming.

3. The implementation will be phased and updated during the early years of the space

station operations.

4. The costs are high but so are the benefits.

5. This technology advancement is essential if the space station autonomy/automation

philosophy is to be implemented.

2.5.5 Technology Advancement Plans

The integration of automated control systems for space station housekeeping subsystems,

such as the electrical power subsystem, life support, and thermal control, would provide

cost savings as well as safety, efficiency, and maintainability benefits to space station

design aril operation.

97
Table 2.5-6. F5184, RTOP Submissions Related to Technology Applicable to

The Space Station Integration of Automated Housekeeping

System Advancement

Center Title Objectives Benefits

Ames Advanced Concepts for o Development of basic computer o Use of these tools in autoResearch Center Knowledge-Based Expert science tools required for know- mated expert systems will

Systems ledge-based expert systems. Will result in more scientific

provide the impetus for automated return per unit dollar and

spacecraft, space platforms, minimum labor-intensive tasks.

scientific instruments, and ground

based stations.

Langley Automation Systems o Develop and support the o Enhance man's capabilities

Research Center Research technology base required to design, for future space activities

develop, and automate teleoperator including servicing, mainand robotic systems. tenance and repairing, structural assembly, and space

manufacturing.

Lyndon B. Automations Technology o Develop automation technology as o Certain systems, when the

Johnson Space for Manned Space Systems _ applied to manned space transports- present level of technology and

Center tion and space station systems. existing manned transportation

complexity as extrapolated from

systems to those of the future

and that required by the space

station, will be entirely

impractical unless it is

automated.

Jet Propulsion Autonomous Spacecraft o To develop expert systems o Autonomous operations will

Laboratory Systems Technology Program for a manned space station have several benefits including

reducing the on-orbit work load

of the space station crew.

and reducing the number of ground

support personnel and resources required to support SS dedication:

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X184-27935-1

A survey of related RTOP's for FY 84 (table 2.5-6) indicates that the technology base is p'

being developed in this area but that base should be expanded to meet the needs identified by this study. While the specific goals of this plan are unique, the integratioi of

automated housekeeping functions impacts not only the subsystems mentioned but the

data management area as well. The architecture of space station data management

a

must support the design requirements imposed by these developments. The plan for the

technology advancement associated with integration of automated housekeeping is prerented by the schedule and resource information of figure 2.5-11 and table 2.5-7,

respectively.

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99
t "'

y

YEARS FROM ^ ATP

TASK 7 2 3 4 S 6 7 8 S 10

MILESTONES

(1) SYSTEM DEFINITION

(2) DEFINE EXPERT SYST12M DECISIONS

} (3) INITIAL KNOWLEDGE BASE

w (4) PROGRAM INTEGRATING CONTROLLER

1

Co

o FUNCTIONS

; I (5) UPDATING EXERCISES

}I (6) ESTABLISH BASELINE FLIGHT"

SOFrWARE

(7) VERIFY BASELINE FRIGHT

' SOFTWARE

4 I, (8) 'UPDATE KNOWLEDGE BASE

(9) IDENTIFY INTEGRATING CONTROLLER*

FUNCTIONS FOR AUTOMATION

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A REQUIREMENT REVIEW 0 DESIGN REVIEW 0 FINAL, REVIEW V SPACE STATION 100

j *SCHEDULED TASKS RELATE FLIGHT SYSTEM DEVELOPMENT AND UPDATING

Figure.? 6-11 Schedule for Integrating Controller Technology Advancement Program

'f
'• Table 2.5-7 Resources for Integrating Controller Technology Advancement Program

0

YEARS FROM ATP

TASK

1 2 3 4 5 6 7 8 S

 _

10 TOTAL

FIGURES IN $1000 (1988)

(1) SYSTEM DEFINITION 200 200

(2) DEFINE EXPERT SYSTEM 100 100 200

DECISIONS

(3) -INITIAL KNOWLEDGE BASE 300 200 BOO

(4) PROGRAM INTEGRATING Soo 1000 1500 3000

CONTROLLER FUNCTIONS

(5) UPDATING EXERCISES 500 5100 100©

(6) ESTABLISH BASELINE* 2000 4800 680 ?

SOFTWARE

(7) VERIFY BASELINE FLIGHT* 2000 4GDO 6000

SOFTWARE

(8) UPDATE KNOWLEDGE BASE * SDO 500 1000

(9) IDENTIFY INTEGRATING* 500 1000 1000 2600

CONTROLLER FUNCTIONS

FOR AUTOMATION

TOTAL 300 400 700 1500 60003 2800 500 1D00 10[ 0 100 0 21200

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0

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Y

*RESOURCES USED FOR FLIGHT SYSTEM DEVELOPMENT AND UPDATING