DOCUMENT NO. 87SDS-b24 ’ CONTRACT NAS 1 - 18032

MAY 1987

THE MULTI-DISCIPLINARY DESIGN STUDY A LIFE CYCLE COST ALGORITHM

R.R. HARDING, J.M. DURAN, AND R.R. KAUFFMAN

GENERAL ELECTRIC COMPANY - ASTRO-SPACE DIVISION KING OF PRUSSIA, PA 19406

NASA CONTRACTOR REPORT 1781 92

(hASA-CR-178192) THE BULTX-DISCIPLI lABY ~ a 7 - 2 1995 CESIGI STUDY, A L f F E CXCLE COST ALGOI?I?EE (General Electric Co.) 1C7 p Avail: IOTIS EC AOd/MP A01 C S U 22B Unclas

63/18 0071305

G E N E R A L @ E L E C T R I C

I I 1 11 I

I C 1

NASA Contractor Report 178192

The Multi-Disciplinary Design Study A Life Cycle Cost Algorithm

R.R. Harding, J.M. Duran, and R.R. Kauffman

General Electric Company - *4stro Space Division King of Prussia. PA 19406

Contract NAS 1- 18032

May 1 9 8 i

National Aeronautics and Space Ad ministration

Langley Research Center Hampton, Virginia 23665-5225

CONTENTS 1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . 1 2 SUMMARY . . . . . . . . . . . . . . . . . . . . . . 3 3 MDDT PROGRAM FLOW . . . . . . . . . . . . . . . . . 8 3.1 Main Routine . . . . . . . . . . . . . . . . . . . 8 3.2 Non-recurring Cost Subroutine . . . . . . . . . . 8 3.4 Launch Cost Subroutine . . . . . . . . . . . . . 11 3.5 Ground Support Cost Subroutine . . . . . . . . . 12 3.6 Maintenence Cost Subroutine . . . . . . . . . . 13 3.7 Expendables Cost Subroutine . . . . . . . . . . 15 3.8 Software Cost Subroutine . . . . . . . . . . . . 15 3.9 ASC Steady State Pointing Subroutine . . . . . . 16 3.10 Active Control Subroutine . . . . . . . . . . . 16 3.11 Summation Of Costs Subroutine . . . . . . . . . 17 3.12 Print Subroutine . . . . . . . . . . . . . . . . 17 4 MDD STUDY STRUCTURE AND CONTROLS ANALYSES . . . . 28 4.1 Structure . . . . . . . . . . . . . . . . . . . 28 4.1.1.1 Description . . . . . . . . . . . . . . . . 28 4.1.1.2 Assumptions . . . . . . . . . . . . . . . . 28 4.1.1.3 Results . . . . . . . . . . . . : . . . . . 29 4.1.2 Structural Dynamics . . . . . . . . . . . . . 29 4.1.2.1 Description . . . . . . . . . . . . . . . . 29 4.1.2.2 Assumptions . . . . . . . . . . . . . . . . 30 4.1.2.3 Results . . . . . . . . . . . . . . . . . . 31 4.1:3. 1 Description' . . . . . . . . . . . . . . . . . 32 4.1.3.2 Assumptions . . . . . . . . . . . . . . . . 33 . 4.1.3.3 Results . . . . . . . . . . . . . . . 33 4.2 ATTITUDE CONTROL SUBSYSTEM i A C S j ANALYSES . . . 42 4.2.1 Disturbance Torques . . . . . . . . . . . . . 42 4.2.1.1 Description . . . . . . . . . . . . . . . . 42 4.2.1.2 Assumptions . . . . . . . . . . . . . . . . . 42 4.2.1.3 Results . . . . . . . . . . . . . . . . . . 45 4.2.2 Controller Optimization And Design . . . . . . 46 4.2.2.1 Description . . . . . . . . . . . . . . . . 46 4.2.2.2 Assumptions . . . . . . . . . . . . . . . . 49 4.2.2.3 Results . . . . . . . . . . . . . . . . . . 49 5 MDD EXAMPLES . . . . . . . . . . . . . . . . . . . 57 5.1 Solar Array Feathering . . . . . . . . . . . . . 57 5.1.1 Description . . . . . . . . . . . . . . . . . 57 5.1.2 Assumptions . . . . . . . . . . . . . . . . . 58 5.1.3 . Results . . . . . . . . . . . . . . . . . . . 60 5.2 Expendables Orbit Adjust Interval . . . . . . . 60 5.2.1 Description . . . . . . . . . . . . . . . . . 60 5.2.2 Assumptions . . . . . . . . . . . . . . . . . 60 5.2.3 Results . . . . . . . . . . . . . . . . . . . 61 5.3 Monopropellent Vs . Bipropellent . . . . . . . . 61 5.3.1 Description . . . . . . . . . . . . . . . . . 61 5.3.2 Assumptions . . . . . . . . . . . . . . . . . 61 5.3.3 Results . . . . . . . . . . . . . . . . . . . 61 5.4 Active Vs Passive Damping LCC . . . . . . . . . 62

3.3 ACS (Attitude Control System) Design Subroutine 10

4.1.1 Expendables Analysis For Mass Properties . . . 28

4.1.3 Erectable Vs Deployable Truss LCC Trade Study 32

i

5 . 4 . 1 5 .4 .2 5.4.3 6 6 . 1 6 . 2 7

APPENDIX A

APPENDIX B

Description . . . . . . . . . . . Assumptions . . . . . . . . . . . Results . . . . . . . . . . . . .

CONCLUSIONS . . . . . . . . . . . . . Advantages Of MDDT . . . . . . . . . General User Information . . . . . .

REFERENCES . . . . . . . . . . . . . .

SPACE STATION DISTURBANCE SIMULATIONS

DUAL KEEL REFERENCE CONFIGURATION ACS EQUIPMENT CHARACTERISTICS

ii

62 -. 62 64 74 74 75 77 8

I

1 INTRODUCTION

The N u l t i - d i s c i p l i n a r y Design (MDD) Study i n v e s t i g a t e s three

a s p e c t s of manned Space S t a t i o n d e s i g n ; c o s t , subsystem d e s i g n

pa rame te r s , and r e l a t i o n s h i p s between c o s t and des ign parameters .

It is a n t i c i p a t e d that complex s p a c e c r a f t d e s i g n s w i l l be based

on t o t a l system c o s t s over the l i f e of the program. An approach

t o e v a l u a t i n g system d e s i g n f o r t h e complete L i f e Cycle Cos t s

(LCC) i s desirable s o t h a t t o t a l program c o s t s may be assessed

f o r any g iven d e s i g n and, t he reby provide a means t o trade c o s t ,

r i s k , performance, and maintenance du r ing the d e s i g n phase. T h i s

s tudy develops a model which spans these d i f f e r e n t d i s c i p l i n e s i n

e f f o r t t o e v a l u a t e LCC, o r more i m p o r t a n t l y , LCC s e n s i t i v i t i e s t o

d i f f e r e n t d e s i g n s and c r i t i ca l parameters .

F i r s t , t he c o s t f a c t o r s of the system from conceptua l d e s i g n

through on-orb i t o p e r a t i o n s are d e f i n e d s o t h a t c o s t a n a l y s e s can

be estimated w i t h i n t h e accuracy of t h e assumptions. These c o s t

f a c t o r s i n c l u d e nonrecur r ing , s p a r e s , ground s u p p o r t , e tc . which

are t y p i c a l f o r s p a c e c r a f t and can be estimated based on

h i s t o r i c a l data o r eng inee r ing judgement.

Second, the r e l a t i o n s h i p s between Space S t a t i o n subsystem

d e s i g n parameters which d e f i n e the c o n f i g u r a t i o n of the subsystem

are examined. F o r t h i s s t u d y , t he r e l a t i o n s h i p s between t h e

a t t i t u d e c o n t r o l and s t r u c t u r e subsystem d e s i g n s are i n v e s t i g a t e d

by us ing a n a l y s i s t echn iques t h a t have been a p p l i e d t o p r e v i o u s

s p a c e c r a f t d e s i g n s . For example, t h e s t r u c t u r e mass p r o p e r t i e s

affect c o n t r o l l e r momentum s t o r a g e , t o r q u e , and bandwidth

1

requirements which in turn affect hardware and software

requirements .

The final phase of this study combined LCC and subsystem

design parameters into a set of computations implemented in a

single computer program. At this point, the computer program is

truly multi-disciplinary. The Multi-disciplinary Design Tool

(MDDT) is the name of the computer program which contains the

controls It is capable of

performing design studies by evaluating different ACS (Attitude

Control System) and structure designs as a function of LCC.

and structural design and LCC models.

2

2 SUMMARY

T h i s s tudy developed a m u l t i - d i s c i p l i n a r y des ign model,

implemented on the computer, t h a t is used t o e v a l u a t e a t t i t u d e

c o n t r o l and s t r u c t u r e subsystem des igns us ing LCC as a des ign

c r i te r ia . Engineer ing design parameters which d e f i n e ACS

( A t t i t u d e Cont ro l System) and s t r u c t u r e d e s i g n s are i n p u t t o t h e

program and r e s u l t i n g LCC and some performance data are output t o

t h e u s e r f o r e v a l u a t i o n .

T h e M u l t i - d i s i p l i n a r y Design Study has i n v e s t i g a t e d LCC

a s p e c t s of t h e manned Space S t a t i o n a t t i t u d e c o n t r o l and

s t r u c t u r e subsystems des igns . The model adresses the major c o s t

a s p e c t s f o r s p a c e c r a f t i n genera l and the Space S t a t i o n i n

p a r t i c u l a r ( f o r example, cos t s f o r Ex t ra Vehicular A c t i v i t y

( E V A ) , replenishment of expendables, and the la tes t b a s e l i n e

Space S t a t i o n hardware). Several example des ign trades have been

performed using t h e Mul t i -d i sc ip l ina ry Design T o o l which

demonstrate the program v a l i d i t y as w e l l as provide some

i n t e r e s t i n g c o s t sav ing d e s i g n approaches.

A summary of the MDD study e f f o r t s and c o s t program f l o w i s

shown i n Figure 1. It can be seen f rom t h i s t o p l e v e l diagram

tha t s e v e r a l p re l iminary analyses and hardware i n v e s t i g a t i o n s

were ne'cessary t o d e f i n e ACS and s t r u c t u r e des ign parameters as

w e l l as o b t a i n some basic c o s t d a t a . These p re l imina ry

i n v e s t i g a t i o n s r e s u l t e d i n general des ign parameters r e q u i r e d t o

describe ACS and s t r u c t u r e c o n f i g u r a t i o n s as w e l l as

r e p r e s e n t a t i v e hardware costs and c o s t s e n s i t i v i t i e s ( e . g .

3

$/pound, o r b i t decay rates, damping material c o s t estimates,

senso r c o s t s , e t c . )

ACS

T h e MDDT model a r c h i t e c t u r e spans the fo l lowing LCC

c h a r a c t e r i s t i c s f o r the Space S t a t i o n ACS and s t ructure d e s i g n s .

Non-recurring des ign

Launch

Expendable replenishment

P a r t f a i l u r e , rep lacement , and maintenance

Ground suppor t

The a r c h i t e c t u r e of MDDT i n c o r p o r a t e s the above LCC

c h a r a c t e r i s t i c s i n i n d i v i d u a l sub rou t ines . The MDDT main program

is a series of ca l l s t o these subrou t ines s o t ha t t he ACS and

s t r u c t u r e c o s t s can be calculated. Each of the above LCC

cr i te r ia inco rpora t e s a number of sub- leve l c o s t parameters which

can be, and i n many cases are , used i n o t h e r LCC c r i t e r i a

c a l c u l a t i o n s .

R e s u l t s o f s p e c i f i c trade s t u d i e s (as required i n the

Statement of Work) and example LCC des ign trades are summarized

i n t he fol lowing paragraphs .

T h e ACS

( A t t i t u d e Control System) d id not prove c o s t s e n s i t i v e i n t he

pre l iminary a n a l y s i s . I n s t e a d , op t imiza t ion of t he ACS w a s

based on c r e a t i n g a maximum c o n t r o l l e r bandwidth f o r a u s e r

Prelirninarv A t t i t u d e Co n t r o l ODtimizat ion.

4

s p e c i f i e d fundamental s t r u c t u r a l resonant f requency. C o s t of

t he ACS as an op t imiza t ion cri teria was accomplished after the

MDDT model was s o p h i s t i c a t e d enough t o i nc lude a c t i v e

s t r u c t u r a l damping d e s i g n s .

S t r u c t u r a l Resonance S e n s t t i v i t v _ . The c o n t r o l l e d Space

S t a t i o n response t o crew kick-off and STS docking was

performed us ing a f l e x i b l e body s imula t ion of the Space

S t a t i o n . The s t r u c t u r a l response of the lower boom r e s u l t i n g

from these d i s t u r b a n c e s a r e 12 arcseconds and 1860 arcseconds

(0 .52 degrees) of d e f l e c t i o n f o r crew and docking

d i s t u r b a n c e s , r e s p e c t i v e l y .

Prel-rv S t r u c t u r a l OD . The f i v e meter bay - t i m i z a t i o n

t r u s s r e s u l t e d i n s i g n i f i c a n t LCC sav ings over t h e n ine f o o t

bay t r u s s ; approximately $47 m i l l i o n saved f o r the erectable

and $67 m i l l i o n f o r t he for t h e deployable .

. .

~ ~ . a . Feather ing the s o l a r a r r a y s

du r ing umbra i n order t o reduce p r o p e l l a n t expend i tu re s f o r

v e l o c i t y make-up ( o r b i t a d j u s t ) provided a sav ings of $25

m i l l i o n .

O r b i t Adjus t . LCC s e n s i t i v i t y a n a l y s i s t o o r b i t a d j u s t

showed a $21 mi l l i on sav ings by going f rom a 50 day i n t e r v a l

i n t e r v a l t o 10 day i n t e r v a l between o r b i t a d j u s t f i r i n g s .

5

Mono Pronellant - vs. Binropellant R B . The higher Isp of

the bipropellant RCS subsystem netted a LCC cost savings of

$126 million.

Active vs . Passive S tructural Damning. A combination of

active control and passive damping material (e.g. SMERD)

6

yielded significant increase in controller bandwidth and

reducing space station LCC. Adding 160 pounds of passive

damping material resulted in increasing the structural damping

ratio from 0.05% to 5% which reduced the number of controlled

strucural modes and reduced LCC by $12 million.

Figure 1 MDD Top Level Analysis and Program Flow

NASTRAN

FREQUEXCY RESPONSE

U N I T

DATA

I N P U T

WDOT

PROGWM

LAUNCH AND DEPLOYMENT

C 0 5 T E S T I GATES

SAMSO I NON- R i C U R R I N:

COST N O E L i

7

1

.-

GROUND 1 %ORT I I MODEL 1 MAINTENANCE

MODEL

EXPENDABLES r-l COST I-(ODE1

SOFTWARE COST MODEL

PiRFORKANCE CALCULAT i 0 X

!

l i

I

I ' A i

OUTPUT COST AM'

PERFORIGRC

3 MDDT PROGRAM FLOW

3.1 Main Routine

T h e MDDT computer program c o n s i s t s of a main r o u t i n e

(MDDT.FOR) and e l even subrou t ines . A l l i n p u t and output

v a r i a b l e s are de f ined i n t h i s r o u t i n e . A l l i n p u t data i s read i n

through t h i s r o u t i n e , and the subrou t ines are called from here.

A flow diagram of the main r o u t i n e i s p resen ted i n F igure 2.

3.2 Non-recurring Cost Subrout ine

The Non-recurring Cost sub rou t ine (NRC.FOR) c a l c u l a t e s t he

non-recurr ing c o s t of t he of t he ACS ( A t t i t u d e Cont ro l System)

and S t r u c t u r e s subsystems. F igure 3 i l l u s t r a t e s t he f l o w of t he

subrou t ine . A choice of two c o s t c a l c u l a t i o n approaches i s

g iven . Subsystem non-recurr ing c o s t may be c a l c u l a t e d us ing

SAMSO, a parametr ic c o s t model r e l a t i n g c o s t t o subsystem weight

( r e f e r e n c e 1). T h e SAMSO c o s t model i s of the f o r m ,

I- = l O O O . O ( A + B( TT'T)=)

where,

= Subsystem non-recurr ing c o s t y- I

K" = Subsystem w e i g h t

A , B, C = Input empi r i ca l c o n s t a n t s

8

The va lues of t he parameters A , B, and C are de f ined i n

Reference 6 . These v a l u e s may be modified t o reflect h i s to r i ca l

c o s t data. The SAMSO model c o s t s i n c l u d e the c o s t of hardware,

d e s i g n , manufacture , and tes t of t h e given subsystem.

A l t e r n a t i v e l y , non-recurr ing cost can be c a l c u l a t e d by summing

c o s t p e r component times number of components f o r a l l types of

components. I n t h i s case, component d e s i g n , test and

manufactur ing c o s t s should be inc luded i n the component costs ,

and p r o j e c t engineer ing c o s t s f o r t h e des ign phase can be

c a l c u l a t e d by invoking a call from the main r o u t i n e t o the ACS

d e s i g n subrou t ine (ACSDES). The non-recurr ing c o s t is m u l t i p l i e d

by t h e fo l lowing three complexity f a c t o r s f o r bo th c o s t models.

C'I - I n f l a t i o n f a c t o r from 1979 d o l l a r s

c!c! = Complexity factor from the SAMSO model

CAI - Modif ier t o account f o r the d i f f e r e n c e i n c o s t

between unmanned and manned s p a c e c r a f t

For t he examples, the SAMSO model was used t o c a l c u l a t e the

S t r u c t u r e s Subsystem non-recurr ing cost , as SAMSO i s a

time-proven model and l a r g e space s t r u c t u r e data was a v a i l a b l e t o

calibrate the SAMSO model f o r s t r u c t u r e s i n t h i s w e i g h t range .

Valid SAMSO parameters could not be found f o r t h e ACS subsystem,

s o the alternate method of c a l c u l a t i o n f o r ACS non-recurr ing

c o s t s was used i n a l l examples.

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3.3 ACS ( A t t i t u d e Cont ro l System) Design Subrout ine

T h e ACS Design subrou t ine (ACSDES), F igu re 4 , c a l c u l a t e s

t o t a l d e s i g n c o s t f o r the ACS subsystem. Design c o s t i s de f ined

as the t o t a l l abor c o s t of engineer ing pe r sonne l invc lved i n

d e s i g n and support of the subsystem throughout a l l phases of t he

miss ion: i n i t i a l des ign , i n i t i a l on-orb i t development and

check-out and nominal on-orb i t ground suppor t . Engineer ing

pe r sonne l a r e ca t agor i zed as p r o j e c t e n g i n e e r s , subsytem

e n g i n e e r s , component eng inee r s , and a n a l y s t s . The number of

a n a l y s t s needed dur ing the i n i t i a l des ign phase ( i . e . number of

development a n a l y s t s ) i s assumed t o equa l the number of c o n t r o l

modes, a v a r i a b l e which i s i n p u t by the u s e r , while the number of

a n a l y s t s needed dur ing the on-orb i t phase ( i . e . number of

o p e r a t i o n s a n a l y s t s ) i s assumed t o be 20% of the number of

development a n a l y s t s . During the on-orb i t development and

check-out phase, the number of a n a l y s t s drops l i n e a r l y from the

number of development a n a l y s t s t o the number of o p e r a t i o n s

a n a l y s t s .

The number of component eng inee r s r e q u i r e d dur ing the

i n i t i a l phase i s de f ined by the number of t y p e s of ACS

components, and drops l i n e a r l y dur ing the on-orb i t development

and check-out phase t o half that number i n t he f i n a l on-orb i t

phase . The

and remains

number of p r o j e c t eng inee r s i s s p e c i f i e d by t h e u s e r

cons tan t throughout t he miss ion .

10

The number of subsystem e n g i n e e r s , l i k e the number of

component eng inee r s , i s assumed t o drop l i n e a r l y dur ing the

on-orb i t development and check-out phase t o half the number

r e q u i r e d dur ing the i n i t i a l des ign phase. ' The areas under the

cu rves described above are i n t e g r a t e d f o r the a p p r o p r i a t e phase

of t he miss ion , summed, and converted from y e a r s t o manhours of

d e s i g n and p r o j e c t engineer ing .

The number of engineer ing personnel is , of course , dependent

on the s i z e and scope of t h e p a r t i c u l a r program f o r which the

MDDT i s be ing used , and a combination of knowledge of the program

and eng inee r ing judgement should be used i n spec i fy ing i n p u t s

where r e q u i r e d . The numbers used i n the example runs described

i n t h i s r e p o r t (Sec t ion 5) were:

Number of c o n t r o l modes = 15

Number of components = 6

Number of p r o j e c t engineers = 1

Number of subsystem engineers = 2

3.4 Launch Cost Subrout ine

T h e Launch Cost subrout ine (LAUNCH.FOR), F i g u r e 5 ,

c a l c u l a t e s the c o s t of launching a subsystem. Launch c o s t p e r

pound i s c a l c u l a t e d by d iv id ing the c o s t t o launch the boos te r by

11

the maximum weight capability of the booster to the desired

orbit, both user-specified inputs. The total subsystem weight is

then multiplied by the launch cost per pound. The total launch

cost however, also includes the cost of EVA, IVA, and use of the

mobile remote manipulator system (MRMS). For this calculation,

the number of hours of activity required and cost per hour of

activity, user-specified inputs, are multiplied. The total

launch cost is calculated by adding EVA, IVA and MRMS costs to

the booster launch cost. Values used for this study were, for

ACS :

Number of hours of EVA required for assembly on launch = 57

Number of hours of IVA required for assembly on launch = 37

Number of hours of MRMS required for assembly on launch = 35

and for Structures :

Number of hours of EVA required for assembly on launch = 100

Number of hours of IVA required for assembly on launch = 5

Number of hours of MRMS required for assembly on launch = 50

Cost figures used were:

Cost per hour of EVA = $62000 Cost per hour of IVA = $17500

Cost :per hour of MRMS = $22000

3.5 Ground Support Cost Subroutine

The Ground Support Cost subroutine (GSUP.FOR) calculates the

cost of ground support over the life of the mission for the

I # t m 8 II II 1 8

12

structures subsystem based on the user-specified number of

manhours and the user-specified cost per manhour of ground

support. (For the ACS subsystem, ground support costs are

calculated in the on-orbit ground support phase of the ACS Design

subroutine.) For this study, the estimated number of

structure-required ground support hours over the length of the

mission (assumed to be 10 years) was 62000.

3.6 Maintenence Cost Subroutine

The Maintenence Cost subroutine (MAINT.FOR), Figure 6,

calculates the cost of maintaining each subsystem over the life

of the mission (post-initial assembly), including replacement of

parts and regular subsystem inspections. The number of expected

failures for each type of component during the mission is

computed using the formula:

where the user-specified inputs are defined as follows:

1V = number of this type of part or component in subsystem =

i U L .= mission length

f1fTBF = mean time between failure of the part or component

13

As an example, f o r t h i s s tudy , t h e Cont ro l Moment Gyro (CMG)

was assumed t o be one of t he ACS components. For t h e CMG, t h e

use r - spec i f i ed i n p u t s were,

AlTBF = 8 4 . 2 y e a r s

T h e c o s t t o r ep lace a failed p a r t i s calculated by summing the

c o s t of a replacement p a r t ( i n p u t by u s e r ) , t h e c o s t t o l aunch

the p a r t ( c a l c u l a t e d as i n Launch Cost sub rou t ine ) , and the c o s t

of the EVA, IVA and MRMS a c t i v i t y r e q u i r e d dur ing replacement

( i n p u t by u s e r ) . The c o s t of subsystem i n s p e c t i o n s i s computed

f o r f o u r poss ib l e related types of a c t i v i t y , E V A , I V A , MRMS use

and ground suppor t , and the r e s u l t i n g c o s t s summed. I n s p e c t i o n

c o s t pe r component t y p e , per t ype of i n s p e c t i o n a c t i v i t y ( E V A ,

IVA, MRMS o r ground suppor t ) i s obta ined by mul t ip ly ing t h e

number of u n i t s of t h a t type by t h e c o s t of the a c t i v i t y p e r

i n s p e c t i o n of tha t t y p e of component and the t o t a l number of

i n s p e c t i o n s expected over the mis s ion l i f e (miss ion l e n g t h

d iv ided by time between i n s p e c t i o n s , a u s e r - s p e c i f i e d i n p u t ) .

T h e t o t . a l c o s t s over t he mission of replacement and i n s p e c t i o n s

pe r p a r t are summed f o r a l l subsystem components t o o b t a i n the

t o t a l c o s t of subsystem maintenence over the course of the

miss ion .

14

3.7 Expendables Cost Subrout ine

T h e Expendables Cost subrout ine (EXPD.FOR), Figure 7 ,

c a l c u l a t e s the c o s t incur red due t o replacement of expendables

consumed over the mission l i f e . T h i s r o u t i n e r e q u i r e s the u s e r

t o i n p u t an i n i t i a l and f i n a l a l t i t u d e of t he s p a c e c r a f t ( i n

fee t ) , the time ( i n days) over which the o r b i t decay occurred ,

and t h e s p e c i f i c impulse of t h e assumed p r o p e l l e n t . For t h i s

s t u d y , an o r b i t decay from approximately 448 km t o 444.6 km

(assumed nominal a l t i t u d e was 450 k m ) over a per iod of t e n days

was used. (See Figure 2 9 . ) The sub rou t ine t h e n computes t h e

energy loss per o r b i t and w e i g h t o f p r o p e l l e n t used per o r b i t i n

v e l o c i t y makeup. The t o t a l weight of p r o p e l l e n t used over the

m i s s i o n i s then computed, using t h e o r b i t pe r iod and l e n g t h of

the miss ion . Using the inpu t cos t pe r pound of p r o p e l l e n t , t he

c o s t due t o purchase o f replacement f u e l i s computed. The c o s t

t o launch t o replacement f u e l is computed by a ca l l t o the launch

c o s t sub rou t ine . A swi t ch i n the r o u t i n e a l lows the c a l c u l a t i o n

of expendables c o s t f o r either monopropellent f u e l o r using the

u s e r - s p e c i f i e d mixture r a t i o f o r b i p r o p e l l e n t .

3 .8 Sof tware Cost Subrout ine

The Software C o s t subrout ine (SOFT.FOR), F igure 8 ,

c a l c u l a t e s t h e c o s t of subsystem-related sof tware development

us ing e i ther the use r - spec i f i ed number of l i n e s o f code and c o s t

per l i n e of code, o r t h e use r - spec i f i ed number of manhours t o

develop the requ i r ed sof tware and c o s t pe r manhour of sof tware

development. For t h i s s tudy , t he assumed number of manhours t o

15

develop ACS-related sof tware was 83000 a t $80 p e r manhour. There

i s no sof tware development a s s o c i a t e d with t h e S t r u c t u r e s

subsystem.

3.9 ASC Steady State Poin t ing Subrout ine

T h e ACS Steady State Poin t ing subrou t ine (ACSPTG), F igure 9 ,

u s e s t he Bode p l o t produced i n the f requency response a n a l y s i s

(Sec t ion 4 . 2 . 2 ) t o provide a p o i n t i n g e r r o r estimate as a

f u n c t i o n of n a t u r a l f requency of t he s t r u c t u r e , s t r u c t u r a l

damping and d i s tu rbance to rque . C o n t r o l l e r break frequency t o

s t r u c t u r e n a t u r a l f requency r a t i o s were c a l c u l a t e d f o r s i x

p o s s i b l e s t r u c t u r a l damping r a t i o s us ing t h e b a s e l i n e Bode p l o t ,

i n o rde r t o a s s u r e c o n t r o l l e r / s t r u c t u r e s t a b i l i t y . The use r

s u p p l i e s the damping r a t i o (from one of the s ix p o s s i b l e choices :

.1,.05,.01,.005,.001,.0005), s t r u c t u r e n a t u r a l f requency , maximum

expec ted d i s tu rbance t o r q u e , o r b i t rate ( f o r a c i r c u l a r o r b i t a t

t he assumed a l t i t u d e of 450 km, o r b i t ra te i s .00112 rad/sec) and

i n e r t i a s of the s t r u c t u r e . T h e sub rou t ine c a l c u l a t e s t he

c o n t r o l l e r break f r equenc ie s f i r s t , based on the predetermined

r a t i o s and t h e g iven s t r u c t u r a l damping, and from t h e break

f r e q u e n c i e s , t h e c o n t r o l l e r g a i n s are c a l c u l a t e d . T h e

d i s t u r b a n c e torque t r a n s f e r func t ion i s then eva lua ted a t twice

o r b i t fate t o de te rmine the r i g i d body s t e a d y - s t a t e po in t ing

e r r o r .

3.10 Act ive Cont ro l Subrout ine

T h e Act ive Cont ro l sub rou t ine (ACTCON.FOR), F igure 10,

I @ 1 I I 1 R I 8

16

c a l c u l a t e s the a d d i t i o n a l sof tware c o s t s due t o a lgor i thms i n the

f l i g h t sof tware which become requi red f o r a c t i v e l y compensating

t h e a c t u a t o r commands due t o s t r u c t u r a l bending. The r o u t i n e

computes how many s t r u c t u r a l modes are r e q u i r e d t o be c o n t r o l l e d

as a f u n c t i o n of how c l o s e t h e resonant f r equenc ie s are t o the

r i g i d body c o n t r o l l e r bandwith. Addi t iona l sof tware c o s t s are

computed based on numbers of l i n e s of code or computer ope ra t ions

pe r c y c l e us ing empi r i ca l equat ions conta ined i n t h e r o u t i n e .

3.11 Summation Of C o s t s Subrout ine

The Summation of Cos ts subrout ine (SUM.FOR) computes the

l i f e c y c l e c o s t of t h e A t t i t u d e Cont ro l Subsystem and the l i f e

c y c l e c o s t of the S t r u c t u r e s Subsystem by summing the costs

output by a l l of t h e c o s t sub rou t ines .

3.12 P r i n t Subrout ine

The P r i n t sub rou t ine (PRINT.FOR) conver t s the ACS and

S t r u c t u r e s c o s t s output by each c o s t r o u t i n e and the t o t a l l i f e

c y c l e c o s t for each of the two subsystems t o m i l l i o n s of dollars.

T h e sub rou t ine a l s o sums the ACS c o s t s w i t h t h e S t r u c t u r e s c o s t s

f o r each ca tegory (each of t he c o s t sub rou t ines and the t o t a l )

and o u t p u t s i n d i v i d u a l and t o t a l c o s t s i n m i l l i o n s of do l l a r s and

ACS perfomance d a t a from t h e ACS Steady State Poin t ing

s u b r o u t i n e .

17

I- n 2

I N

I I

I I

I I

18

Figure 3

Use SAMSO model?

Subroutine NRC

Yes

Choose either SAMSO method or component cost data method

to calculate nou-recurring cost?

~ - _- - -. - -. ~ _ _ Invalid choice]- -

4

No P

Calculate subsyteiii weight by suiiuiing component weights

L. I Use SARISO m o d q No I ;e:--- C'al'culate non-recurring coct

fr oiii t o t a1 si 11) vs t em weight using SAMSO !

. _ _ _ . .- . .. -

. - t . -

hlitltiply non-recurring cost by coiiiplexity factors

19

Figure 4

i? 1

20

4

J

Figure 4

h

21

- 0 - II VI 4 VI s C bn VI 0, -u M E L 0, 0, E M C

.-

.-

.- w -

Figure 5

Subroutine LAUNCH

START 7

22

Figure 6

No

Subroutine MAINT

START (7 Calculate cost per pound of payload

delivered to orbit

1 1 Calculate cost to launch one I replacement part of this type

(EVA, IVA, MRMS, required to to replace one part of this type

Calculate expected number of this type of part

parte of this type

I calculate LCC of EVA, IVA, MRMS,

required during inspection of a part of this type

23

Figure 7

r

Subroutine EXPD

- - No

START (2

Use biprop mixture ratio ' and cost relation to

determine expendables cost

Yes

Use monopropellent weight and cost data to determine

expendables cost

0 RETURN

24

Figure 8

Subroutine SOFT

START T Calculate software cost

based on number of lines of code

Is cost per line of software input?

Calculate software cost based on number of manhours

25

Figure 9

v

Subr ou t h e ACS P T G

Calculate rigid body steady state point.ing errors due to e m i r onmen t a1 disturbances

START

1 Is damping ratio input one

of the following: .0005, .001, .005, .01, .05, or .l?

Invalid choice of damping ratio

26

Figure 10

f

Subroutine ACTCON

START c?

Calculate active control software costs d 0 RETURN

27

I

4 MDD STUDY STRUCTURE AND CONTROLS ANALYSES

4.1 S t r u c t u r e

4.1.1 Expendables Ana lys i s For Mass P r o p e r t i e s -

4.1.1.1 Expendables Ana lys i s D e s c r i p t i o n -

T h e mass p r o p e r t i e s employed i n the expendables a n a l y s i s are

talren from r e f e r e n c e 2 and c o n s i d e r an I n i t i a l Opera t ing

Conf igu ra t ion ( I O C ) space s t a t i o n similar t o that shown i n

F igu re 11. These mass p r o p e r t i e s r e p r e s e n t a c u r r e n t best

estimate of what the space s t a t i o n ' s mass p r o p e r t i e s w i l l be

d u r i n g the e a r l y phases of o p e r a t i o n . T h i s cor responds t o the

p e r i o d of o p e r a t i o n when f u e l usage w i l l be highest as the space

s t a t i o n ' s b a l l i s t i c c o e f f i c i e n t ( w e i g h t / f r o n t a l area) w i l l be

low. T h i s resul ts i n large drag effects r e q u i r i n g o r b i t a l

c o r r e c t i o n s .

4.1.1.2 Expendables Analys is Assumptions -

These mass p r o p e r t i e s are f o r a f i v e meter bay t r u s s d u a l

keel space s t a t i o n w i t h f o u r crew h a b i t a t i o n modules. No

payloads are inc luded . Various s e r v i c i n g bays are no t i n c l u d e d .

T h e h y b r i d power system ( f o u r p h o t o v o l t a i c a r r a y s and two s o l a r

dynamic e n g i n e s ) i s employed. The space s h u t t l e o rb i te r i s no t

p r e s e n t .

28

I 8 I 8 I I 1

1 a

i 8 8 I I I n I 8 8

4.1.1.3 Expendables Analys is Resul t s -

The mass p r o p e r t i e s employed i n t h i s a n a l y s i s are shown i n

F igure 12. A s can be seen , t h e space s t a t i o n weight used i n t he

expendables a n a l y s i s i s 466354. pounds. The space s t a t i o n a l s o

has very large i n e r t i a s , even du r ing t h e e a r l y bui ld-up phase.

Both t h e mass and i n e r t i a of space s t a t i o n w i l l i n c r e a s e as t h e

c o n f i g u r a t i o n evolves .

4.1.2 S t r u c t u r a l Dynamics -

4.1.2.1 S t r u c t u r a l Dynamics Descr ip t ion -

Simple NASTRAN models of two space s t a t i o n c o n f i g u r a t i o n s

were developed. The two conf igu ra t ions cons idered were a

deployable n ine f o o t bay t r u s s and an erectable f i v e meter bay

t r u s s dual keel space s t a t i o n . T h e models inc luded f o u r crew

h a b i t a t i o n modules and a r e p r e s e n t a t i v e I O C payload compliment. .

T h e geometr ies of the 9-foot and t h e 5-meter bay models are

i d e n t i c a l . F igure 13 p r e s e n t s f o u r views of t h e model. T h e

power system inc luded i n t he NASTRAN models i s comprised of e igh t

p h o t o v o l t a i c s o l a r a r r a y s . The dynamic modes and f r equenc ie s of

t h e two c o n f i g u r a t i o n s were c a l c u l a t e d . T h i s data was employed

t o de te rmine the the A t t i t u d e Cont ro l System ( A C S ) performance

characteristics.

These models were a l s o employed i n a d i s t u r b a n c e response

a n a l y s i s . The f i v e meter bay truss space s t a t i o n model was

e x c i t e d by a crew member k ickoff f o r c i n g f u n c t i o n (See F igure 14)

and a space s h u t t l e o r b i t e r docking f o r c i n g f u n c t i o n (See

29

Figure 15 ) . Selected r e s u l t s of t h i s response a n a l y s i s are

p r e s e n t e d i n Appendix A . F i g u r e s A 1 th rough A 1 0 p r e s e n t t he

r e s u l t s f o r t h e crew k i c k o f f d i s t u r b a n c e . F i g u r e s A 1 th rough A 3

p l o t t h e three o r thogana l d i sp l acemen t s i n r a d i a n s a t the ACS

package through 100 seconds w i t h the ACS i n a c t i v e . F igu re A 4

shows the corresponding Theta y d e f l e c t i o n s a t the t i p of t h e

lower boom. F igure A 5 p r e s e n t s t he cor responding 2 axis l i n e a r

a c c e l e r a t i o n i n g ' s . F i g u r e s A 6 th rough A 1 0 p r e s e n t similar data

w i t h the ACS package a c t i v e . F i g u r e s A l l th rough A 2 0 p r e s e n t t h e

s h u t t l e o r b i t e r docking data i n the same o r d e r as F i g u r e s A 1

th rough A 1 0 .

The angular d e f l e c t i o n f o r u n c o n t r o l l e d the k i c k o f f was on

the o r d e r 60 microrad . T h e c o n t r o l l e r reduced t h i s t o about 40

microrad. The a c c e l e r a t i o n levels a t t h e ACS package were about

180 micro-g 's both w i t h and without the c o n t r o l l e r .

T h e s h u t t l e docking event r e s u l t s i n higher response l e v e l s .

A f t e r 100 seconds, t h e angu la r d e f l e c t i o n f o r the u n c o n t r o l l e d

docking event i s approximately 15000 microrad . The c o n t r o l l e r

reduced t h i s t o 9000 microrad. The a c c e l e r a t i o n l e v e l s a t the

ACS package were about 3000 micro-g ' s b o t h w i t h and t h e

c o n t r o l l e r .

wi thout

4 . 1 . 2 . 2 S t r u c t u r a l Dynamics Assumptions -

There were several assumptions employed i n t h i s a n a l y s i s .

T h e space s t a t i o n t r u s s s t r u c t u r e w a s r e p r e s e n t e d as an

e q u i v a l e n t beam. T h i s w i l l lead t o e r r o r s i n h igher o r d e r

30

I 1 I 8 1 I R I I

eigenvalues and - eigenvectors; however, this beam representation

is sufficiently accurate for preliminary configuration studies.

A l s o , it was assumed that the space station acts as a linear

structure and that the truss joints are rigid. It has been shown

(reference 3) that even small amounts of free play (:bo05 inches)

in the truss joints will result in significant non-linear

behavior (one to three inches of free play in keel). The

non-linear characteristics of the keel must be minimized in order

to have a well defined predictable stucture. Note that it is

more difficult to avoid free play in the joints of deployable

trusses than of erectable ones.

4.1.2.3 Structural Dynamics Results -

The results of this analysis are summarized in Figure 16.

Listed-are flexible mode shape descriptions and the corresponding

frequencies through approximately .6 hz for both models. As can

be seen from .this data, the space station is a highly flexible

structure with high modal density.

The fundamental flexible mode is a solar array mode at

approximately .17 hz. The fundamental flexible keel modes occur

at .197 hz for the nine foot bay configuration and .356 hz for

the five meter bay configuration. The l ow frequencies of the

fundamental keel modes will challenge the ability of the ACS to

meet orbital performance requirements. The high modal density

will also complicate the task of the ACS.

31

4.1.3 Erectable V s Deployable Truss LCC Trade Study -

4.1.3.1 Erec tab le V s Deployable Truss Desc r ip t ion -

A l i f e cycle c o s t (LCC) trade s t u d y was performed between

erectable and deployable t r u s s concepts . A l s o v a r i e d were t r u s s

bay s i z e s . Nine f o o t and f i v e meter bay s i z e s were cons idered .

Thus there were four cases: a n i n e f o o t bay deployable keel, a

n ine f o o t bay erectable keel, a f i v e meter bay deployable keel,

and a f i v e meter bay erectable keel. A l l four cases are d u a l

keel space s t a t i o n s wi th similar o v e r a l dimensions.

r e f e r e n c e 4 g ives the estimated amount (approximately 1

of Extra-Vehicular A c t i v i t y (EVA) r e q u i r e d t o d e p l o y j e r e c t

T h e amount of I n t r a - v e h i c u l a r

( I V A ) and Mobile Se rv ice Center (MSC) a c t i v i t y r e q u i r e d

. w a s estimated f r o m t h e amount of EVA t ime . The number and t y p e s

of p a r t s comprising each case were estimated. A s would be

expec ted , the n ine f o o t bay cases were comprised of more bays and

t h e r e f o r e had s i g n i f i c a n t l y more p a r t s t h a n the f i v e meter bay

cases (3014 p a r t s f o r t h e 9 f o o t bay d e s i g n v e r s u s 1690 f o r t he

f i v e meter des ign ) . A l s o , t he deployable cases requ i r ed v a r i o u s

t y p e s of deployable j o i n t s and t h e r e f o r e r e q u i r e d more t y p e s of

p a r t s t h a n the erectable cases.

hour)

each of the four cases cons idered .

A c t i v i t y

32

4.1.3.2 Erectable Vs Deployable-Truss Assumptions -

It was assumed that the ACS (Attitude Control System)

required by each of the four cases was identical and that they

required the same quantity of expendables. Also, all four cases

were assumed to have the same level of structural damping.

Finally, it is assumed that the values assigned to all parameters

employed in the analysis are correct. Many of the parameters are

poorly defined at this stage in space station's development and

rough order of magnitude estimates are employed. Any cost study

of this nature must be updated as the station's configuration and

characteristics become better defined.

4.1.3.3 Erectable Vs Deployable Truss Results - The life cycle

costs of the four cases are shown in Figure 17. As can be seen,

the five meter bay truss results in significant life cycle cost

savings over the nine foot bay truss. Savings of 47.4 million

dolars were seen for the erectable cases while savings of 67.4

million dollars were seen for the deployable cases. This results

primarily from the reduced number of joints in the larger bay

size cases.

Also evident is that the erectable cases are less expensive

than the deployable ones. Savings of 52.7 million dollars were

seen for' the five meter cases while savings of 72.7 million

dollars were seen for the nine foot cases. This result occurs

even though the erectable cases require more on-orbit manpower to

erect/deploy (reference 4). The savings come from the decreased

complexity and increased reliability of the erectable designs.

Thus, it was found that the erectable five meter bay truss

case had the lowest life cycle cost at 786.5 million dollars

while the deployable nine foot bay truss had the highest life

cycle cost at 906.6 million dollars. This represents a savings

of 120.1 million dollars (fifteen percent) over a ten year

mission.

34

Figure 11 Reference Space S t a t i o n Design DUAL KEEL 5-METER CONFIGURATION 2-Y PLANE

? T

35

Weight (lb) 1nertia(slug-ft**2) IXX IYY IZZ IXY 1x2 IYZ

Figure 12 Weight Properties

466354.

1.1138 5.2237 7.9837 -1.4734 -1.6336 7.80E5

36

Figure 13 Space S t a t i o n NASTRAN Model

DUAL KEEL ANALYTICAL MODEL

37

X > Y

' I

X Lz

I I \

W'

U

Figure 14 C r e w Kickoff Disturbance

25

0

-25

38

Figure 15 Space Shuttle Orbiter Disturbance

0 . I TIME, SEC

2

39

Figure 16 Nine Foot and Five Meter Dual Keel Modal Resul t s

Mode D e s c r i p t i o n

S o l a r Array Mast S o l a r Array Mast S o l a r Array Mast S o l a r Array Mast Solar Array Mast S o l a r Array Mast S o l a r Array Mast S o l a r Array Mast S o l a r Array Mast S o l a r Array Mast S o l a r Array Mast S o l a r Array Mast S o l a r Array Mast S o l a r Array Mast S o l a r Array Mast S o l a r Array Mast Keel P i t c h Bending Module Support/Keel P i t c h Bending Keel Tors ion Transverse Boom Keel R o l l Bending/Transverse Boom Transverse Boom/Array Mast Keel Torsion/Keel R o l l Bending Keel R o l l Bending/Keel Tor s ion /Rad ia to r Radia tor (and Keel Tors ion i n 5 meter) Rad ia to r Rad ia to r Rad ia to r

40

Frequency (hz) Nine Five Foot Meter

.162

.164

.167

.174

.176

.l79

.179

.180

.180

.180

.180

.180

.180

.180

.182

.193

.197

.227

.283

.354

.378 ,383 .405 .415 .518 .521 .523 .577

.I74

.175

.178

.179

.180

.180

.180

.180

.180

.180

.180

.180

.180

.180

.182

.198

.356

.407

.507

.631

.680

.631

.734

.731

.564

.548

.557

.551

I I I I I I I 1 II I I I I I I I I I I

Figure 17 Erectable v s Deployable Truss L i f e Cycle Trade Study

Cost i n M i l l i o n s of D o l l a r s Five F ive Nine Nine Foot Meter Meter Foot

Erectable Deployable Erectable Deployable

Type of Cost Non-Recurring C o s t 153.6 186.0 157.1 195.7 Launch Cost 37.6 40.4 43.1 47.4 Ground Support Cost 20.9 24.8 23.7 29.6 Maintainence Cost 42.0 55.7 73.1 97.3 Expendables C o s t 503.6 503.6 503.6 503.6 Software C o s t 28.8 28.8 33.2 33.2

839.2 833.9 906.6 T o t a l C o s t 786.5

ERECTABLE VS. DEPLOYABLE TRUSS LCC TRADE STUDY

h

v

k-

0 300

200

100

NON-REC GND SUP EXPD TOTAL

LAUNCH M A NT S/W rYPE O F COST

L EG E: N O

5-METER ERECTABLE

5-METER DEPLOYABLE

9 - FOOT ERECTABLE

9-FOOT DEPLOYABLE

41

4.2

4 . 2 .

ATTITUDE CONTROL SUBSYSTEM (ACS) ANALYSES

Disturbance Torques -

4.2.1.1 Disturbance Torque Analys is D e s c r i p t i o n -

The major d i s tu rbance t o r q u e s expe r i enced by low Earth

o r b i t i n g s a t e l l i t e s , such as the Space S t a t i o n , are g r a v i t y

g r a d i e n t to rque and aerodynamic t o r q u e . S o l a r p r e s s u r e t o r q u e

and r e s i d u a l magnetic d i p o l e were found t o be small i n An comparison, and t h e r e f o r e are not cons ide red here.

independent s imula t ion was run t o model these d i s t u r b a n c e s f o r

use i n related ana lyses .

4 . 2 . 1 . 2 Disturbance Torque Analys is Assumptions -

The d i s tu rbance to rque a n a l y s i s assumes t h a t the Space

S t a t i o n conf igu ra t ion i s the Dual K e e l t y p e w i t h no payloads , 2

s a t e l l i t e s e r v i c e / s t o r a g e bays , a hybr id power system ( f o u r

p h o t o v o l t a i c s o l a r a r r a y s and two s o l a r dynamic e n g i n e s ) , two

s o l a r radiators and f i v e modules F igure 11. A nominal a l t i t u d e

of 450 k m i s assumed ( r e f e r e n c e 5 and 6 ) , and mass p r o p e r t i e s are

g iven i n Figure 12. The proposed Torque Equi l ibr ium A t t i t u d e

p o i n t i n g scheme i s not cons ide red , as i t would p r e s e n t

compl ica t ions beyond the scope of t h i s s tudy . It i s assumed

t h e r e f o r e t h a t the Space S t a t i o n i s Ear th-poin ted , and i s flown

w i t h no b i a s a t t i t u d e s . The c o n t r o l l e r i s modeled as a

Proportional-Integral-Derivative ( P I D ) t ype w i t h ,

42

where,

T c = Cont ro l t o r q u e

l<R = Rate g a i n

II'P = P o s i t i o n g a i n

K I = I n t e g r a l g a i n

8 = Poin t ing e r r o r w i t h respect t o Ear th-poin t ing r e f e r e n c e

= Laplace o p e r a t o r

A t o r q u e i s imposed on any E a r t h - o r b i t i n g s p a c e c r a f t due t o

the E a r t h ' s i n v e r s e square g r a v i t a t i o n a l f i e l d . T h i s g r a v i t y

g r a d i e n t t o r q u e i s modeled for Space S t a t i o n i n an independent

ACS ( A t t i t u d e Con t ro l Subsystem) s i m u l a t i o n ( R e f . 10) as

fo l lows :

43

I CJ = orbit rate = 1.12E-03 radlsec

p , = direction cosines of the local vertical in the

spacecraft reference frame

I j , = moment of inertia (ft-lb-see)

Aerodynamic torque results from the impact of the Earth's

upper atmosphere on the surface of the spacecraft. In this

study, aerodynamic force is modeled as a combination of both

absorption of and diffuse reflection of atmospheric molecules off

the surface of the spacecraft (reference 7). The reference Space

Station configuration, Figure 11 was broken down into the

following ten planar surfaces and force and torque components

were computed for each component surface: 2 satellite

storage/service bays, 4 solar array panels, 2 solar concentrators

and 2 solar radiators. The trusswork, which accounts for only a

small percentage of the total frontal area of the assumed

structure, was not considered. The absorptive component of the

aerodynamic force acts only in the spacecraft velocity direction,

and is described by (reference 8).

The diffuse component is given by (reference 81,

I I 1 I 1 I I I I

44

where,

P - Atmospheric d e n s i t y a t 450 km. ( r e f e r e n c e 9)

V = T r a n s l a t i o n a l v e l o c i t y o f component s u r f a c e r e l a t i v e t o

i n c i d e n t a i r s t r e a m

A = Component s u r f a c e area

c ' d = C o e f f i c i e n t of drag = 2.2 ( R e f . 2, 4 and 5)

6 = Unit vec to r i n t h e d i r e c t i o n of the i n c i d e n t airstream

i l - Unit v e c t o r normal t o t h e component s u r f a c e and directed

outward

A t ime-varying a lpha angle ( the a r r a y ang le i n the o r b i t

p lane) and an average beta angle ( ang le the s u n l i n e makes w i t h

the o r b i t p l ane ) of 36.73 deg over t h e o r b i t were assumed f o r t he

aerodynamic to rque c a l c u l a t i o n s .

4.2.1.3. Disturbance Torque Analysis R e s u l t s -

Simulat ion shows aerodynamic to rque t o be t h e most

s i g n i f i c a n t environmental d i s tu rbance f o r the assumed space

s t a t i o n c o n f i g u r a t i o n . A cursory i n v e s t g a t i o n of magnetic d i p o l e

and s o l a r p re s su re to rque confirmed that these d i s t u r b a n c e s are

4 5

r e l a t i v e l y i n s i g n f i c a n t .

18 and 19.

Typ ica l magnitudes are shown i n F i g u r e s

4 . 2 . 2 C o n t r o l l e r Opt imiza t ion And Design -

4.2.2.1 C o n t r o l l e r Opt imiza t ion And Design D e s c r i p t i o n -

The p re l imina ry d e s i g n of t h e ACS i s based on b a s e l i n e ACS

d e s i g n c o n f i g u r a t i o n d e f i n e d i n r e f e r e n c e 5 . (For a l i s t Of

hardware, see Appendix B.) A s a r e s u l t of t h e hardware r e q u i r e d

f o r a classical c o n t r o l d e s i g n and i t ' s c a p a b i l i t y t o handle a

wide range of c o n t r o l l e r bandwidths, the ACS did not prove c o s t

s e n s i t i v e i n t h e p re l imina ry a n a l y s i s . Opt imiza t ion of t he ACS

was based on c r e a t i n g a maximum c o n t r o l l e r bandwidth f o r a u s e r

s p e c i f i e d fundamental s t r u c t u r a l r e sonan t f requency . The

p r e l i m i n a r y op t imiza t ion was, t h e r e f o r e , based on s t e a d y s t a t e

p o i n t i n g and t r a n s i e n t response performance when c o n s i d e r i n g

d i s t u r b a n c e s ( i . e . low f requency , s t e p i n p u t t y p e , and h igher

f requency d i s t u r b a n c e s such as environment , STS docking and crew

motion, r e s p e c t i v e l y ) . Cost of the ACS as an o p t i m i z a t i o n

c r i te r ia w a s accomplished after the MDDT model was s o p h i s t i c a t e d

enough t o inc lude a c t i v e s t r u c t u r a l damping d e s i g n s .

A f requency response a n a l y s i s w a s performed i n o r d e r t o

enab le ,the MDD computer program t o provide a p o i n t i n g e r r o r

estimate as a f u n c t i o n of n a t u r a l f requency o f the s t r u c t u r e ,

s t r u c t u r a l damping and d i s t u r b a n c e t o r q u e . The frequency

response p o r t i o n of an in-house t h r e e - a x i s c o n t r o l system

s i m u l a t i o n (reference lo) was r u n w i t h a v a r i e t y of c o n t r o l l e r

46

break f r equenc ie s u n t i l a Bode p l o t e x h i b i t i n g good s t a b i l i t y

characteristics was generated. The ga in curve s h i f t s i n

f requency as the s t r u c t u r e n a t u r a l f requency i s v a r i e d .

A cons tan t r a t i o i s maintained between the s t r u c t u r e n a t u r a l

f requency and the c o n t r o l l e r break f r equenc ie s . Ra t ios of t h e

c o n t r o l l e r break f r equenc ie s have been c a l c u l a t e d f o r the s i x

assumed va lues of damping r a t i o ; 0.0005, 0.001, 0.005, 0.01,

0.05, 0.1. The ACS po in t ing r o u t i n e accep t s t h e fundamental

f requency va lue and t h e use r supp l i ed va lue of damping f o r that

s t r u c t u r a l mode as i n p u t s . The r o u t i n e computes t he desired

c o n t r o l l e r g a i n s so that c o n t r o l l e r / s t r u c t u r e s t a b i l i t y i s

a s s u r e d .

The r o u t i n e a l s o eva lua te s t h e s t eady state p o i n t i n g

s e n s i t i v i t y t o d i s tu rbance to rques wi th a frequency con ten t a t

two times o r b i t a l rate v i a t h e fo l lowing s e n s i t i v i t y t r a n s f e r

f u n c t i o n .

where,

f7 = s.teady s ta te po in t ing error

Td = d i s t u r b a n c e to rque amplitude

I = moment of i n e r t i a

47

.s = Laplace o p e r a t o r

1I-I2 = rate ga in

1<P= p o s i t i o n ga in

11-1 = i n t e g r a l g a i n

F i g u r e s 20 through 22 are g a i n and phase v e r s u s f requency

p l o t s of po in t ing s e n s i t i v i t y f o r t he roll, p i t c h , and yaw axes

which have been gene ra t ed us ing an in-house l i n e a r system

a n a l y s i s computer t o o l ( r e f e r e n c e 10). MDDT e v a l u a t e s t h e same

p o i n t i n g s e n s i t i v i t y t r a n s f e r f u n c t i o n a t two times o r b i t a l ra te .

S t r u c t u r a l mode s e n s i t i v i t y was a l s o i n v e s t i g a t e d t o

de te rmine the dependence of modal d e f l e c t i o n t o c o n t r o l l e r

bandwidth. Figure 23 shows the f irst s t r u c t u r a l mode s e n s i t i v i t y

t o d i s t u r b a n c e s f o r a r e l a t i v e l y low r i g i d body mode bandwidth

( n o t e t h a t t h e mode shape was largest i n t h i s , roll, c o n t r o l

a x i s ) . Figure 24 i s a p l o t of t he same modal s e n s i t i v i t y t o

d i s t u r b a n c e s w i t h a higher c o n t r o l l e r bandwidth. Both cases

r e s u l t e d in a peak modal s e n s i t i v i t y of approximately -22 db.

The re fo re , s t r u c t u r a l v i b r a t i o n s e n s i t i v i t y i s no t dependent on

classica.1 c o n t r o l l e r bandwidth s e l e c t i o n . T h i s i s expec ted

because the c lass ical c o n t r o l l e r i s des igned not t o e x c i t e the

s t r u c t u r e .

48

4 . 2 . 2 . 2 C o n t r o l l e r Optimizat ion And Design Assumptions -

The c o n t r o l l e r ' op t imiza t ion and des ign a n a l y s i s assumes a

classical c o n t r o l l e r . Evaluat ion of the d i s tu rbance to rque

t r a n s f e r f u n c t i o n does not t ake i n t o c o n s i d e r a t i o n the effects of

f lex ib le modes o r t he t r i p l e l ag f i l t e r used t o roll of f the high

f requency response . T h i s s i m p l i f i c a t i o n of t he t r a n s f e r f u n c t i o n

i s used because the low frequency g a i n s are of i n t e r e s t and the

h igher f requency effects are n e g l i g i b l e f o r t h i s p a r t of the

a n a l y s i s .

4 . 2 . 2 . 3 C o n t r o l l e r Optimizat ion And Design R e s u l t s -

The i n i t i a l c o n t r o l l e r des ign , w i t h r e l a t i v e l y h igh

bandwidth (0.0628 rads/sec) r e s u l t s i n a very low va lue of

s e n s i t i v i t y i . e . -114, -108, and -110 db i n r o l l , p i t c h , and

yaw, r e s p e c t i v e l y as seen i n F igures 20, 2 1 , and 22. The

expec ted s t eady s ta te po in t ing e r r o r ( i n r a d i a n s ) i s obta ined by

mul t ip ly ing these s e n s i t i v i t y va lues by the inpu t d i s tu rbance

t o r q u e ampl i tudes .

A s a r e s u l t of t h i s a n a l y s i s t h e MDDT computer program

provides a means of eva lua t ing a t t i t u d e perfomance f o r vary ing

space s t a t i o n c o n f i g u r a t i o n s . The po in t ing e r r o r s seen f o r the

example . cases run are very small (maximum error equa l s 1.75

arc-sec i n p i t c h wi th 0.0005 s t r u c t u r a l damping) due t o ve ry

small po in t ing s e n s i t i v i t y t o environmental d i s t u r b a n c e s a t twice

o r b i t a l rate.

49

Figure 18

-3.27

2.70 12.0

-0.510

URRS L INEFlR 3 R X I S S / C SIMLN P I 0 CONTROLLER 3.16 DTRQ 1

13.0 DTR02 DTRO3 0.297 D I S T U R B R N C E TORQUES

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

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..., .................................. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ................................................

.

TEST-CRSE: R l C I o BODY ONLY

DRTR TIHES: 0000r00~00~00 .000 TO 0000:07:U8:00.000 DATE PLOTTED: 26-RUG-86 08135101 GARVITY GRADIENT AND REROOYNRHIC

I INPUTJILE: USERSRCS:CHRRDING~CNTRL~.PLTI~ / 26-RUG-1986 08rlf:UU HEAN- 2.93 SGHA- 0.16U 625 POINTS PLOTTEI

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ....................... -_ ..... ... 4 . .._____ L . L .......... c _ I _ L _ . _ ..-. .. ___. ...................... . L ............. - -

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . , . . . . . . . . . . . . . . . . . . . . . . . -. . __ ... - . -- . -_ __ ._--.__I -_-._-_ - ROLL I

0 .

P I T C H 0 .

-13.33

0.80

YAW 0 .

-0. ao

................................................................... --. . , ........ . . , , .

.............. ............... , ,

I . ......................................... - _ / .................................................. _-.--.-. _ _ _ J ..................... / .

, .

I ......................................... ..., .................................... i ......................................... .................................... 1. .......................

.......................................... . . . . . . . . . . ..: .................. 1... . . . . . . . . . . .

, ,

. .

............................................... , .

FTLB HERN=-O.152 SGW 0.280 625 POINTS PLOTTED J

................ ' I ...................... .....,... ........ .....,........ ~ ............ ............ ......... ............... ......... .._.

I I , . . , . . . . . . . . . . . __, ._ . . . . . . . . . . 2 ....... '..: ..... .............. ; ...... i ..................,. A . ....................

I

0. 00 1700.

0000: 00: 00: 00 9100. I M ~ l u l O E * o s 0.1880~*0S 0.2350E*05

SECONDS

50

I I I I I I 1 I I I I I I I I I I I I

Figure#19 Expected Environmental Torques

Gravity GG and Solar

Roll ( f t - l b ) : 1.12E-02 0.00

Max. : 2.93 0.233 3.16

Mean : 2.93 -4.010E-04 2.93

Pitch ( f t - l b ) :

Max. : 6.12 6.90 13.0

Mean : 6.12 6.37 12.5

Y a w ( f t - l b ) :

Max. : 7.8513-05 0.297 0.297

Mean : 1.1233-06 -0.152 -0.152

51

1.03E-02

0.13E-02

Figure 20

120.00

60.00

OPEN-

0. LOOP GAIN ( D E C I B E L S )

-60.00

-120.0

180.00

90.00

OPEN- LOOP PHASE 0. (DEGREES 1

-90.00-

SPFlCE S T R T I O N T H R E E R X I S C N T R L R -1OU. - 1 19. 0 I STURBRNCE TORQUE SENS I T I 79.5 -137.

DATA TIMES: 0000:00:00:38~000 TO 0000:00tU8:20.000 ORTE PLOTTED: 25-RUG-86 15:35:51 I X . I Y , I f , I X Y . I Y Z . I X Z [SLUG-FTMFTI I l.llE+O~.S.22E+~7.7.9aE+O7.O.O.O.U.O.O INPUTJILE: USERSRCS:CHRADING. URRS33800E3. PLTt 205 I 25-RUG-1986 15: 30: 56

67 POINTS PLOTTEI 8S MERN- -110. SGMR- 3.91

EGS MEAN- 19.8 SGMR- 62.9 67 POINTS PLOTTE . . . . . . . . . ................................................... . . ................................................... . . . . . . . .

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

. . . . . . . . . . . . . . . . . . . . . . . . . . ..._. . . . . . . . . . . . . . . . . . . . . . .

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

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

. . . . . . . . . . . . . . . . . . . . . . . - ...................................... -. . . . . . . . . . . .

.- - .... __ .. . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . - 1 -

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

............................................. . _ .___ . . . . . . . . . . . . . . . . . .

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

1 I

0.00 -1.000 -2. 000 FREQUENCY

1.000

LOGHZ

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I I I I I I I I I I I :I I I I I I I I

Figure 21

-97.1 - 1 18. 0 I STURBRNCE TORQUE SENS I T I , 8k$ i 83.5 -161. MRSS PROPS.

I DATA TIMES: OOOOrOOi

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

............................................................................................ I . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

CPEN- LOOP G A I N 0.

....................................................................................................... . . . . . . . . . . . . . . . . . . . . . . . . . . . !DECIBELS) I . . .........................................

-60.00

-120.0a

180.00

90.00

OPEN- LOOP PHASE (DEGREES

0.

-90.00

-18O.OC

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

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

_ _ ~

..... - - - . . . . . . . . . . . . . . . . . . . . . . . . . . .-.-.-.... ................ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

........................................................... ...............,....................... . . . . . . . . . . . .

IEGS MEAN- 18.U SGHA- 68.5 73 POINTS PLOTTED .................................................................................................... ................................................. . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . _.- .............. 1.. ......................... - ................... - ...._........._... ....... . _._.___ . .._.. ............

. . . . . . .

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

....... - . . . . . . . . . .

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

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

............................................... ._ ._____

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

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

-4. 000 -3.000 0000: 00: 00: 00

-2.000 -1.000 0.00 FREQUENCY

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1. 000 LOGHZ

Figure 22

120.00

60.00

GPEN- LOOP GAIN (DECIBELS)

0.

-60.00

-120.0

1eo.00

90.00

CPEN- LOOP PHASE (DEGREES 1

0.

-90.00.

-180. Of

S P R C E STRTION T H R E E RXIS CNTRLR 0 I S T U R B R N C E TORQUE SENS I T I !$! 82.5 -151.

-101. - 1 19.

MRSS PROPS. TEST-CRSE : DATA TIMES: 0000:00:00:27.200 TO 0000~01:03:20.000 DATE PLOTTED: 25-RUG-86 15:rll:30 I X . I Y , 12. I X Y , I Y Z . 1x2 1.1 1E*08,5.22E+07.7.98E+07.0.0,0.0~ 0.0 INPUTJILE: USEflSRCS:CHAflDING.UARS33800E3.PLT:207 I 25-AUG-1986 15:Ul:OZ 3s MEAN- -108. SGHA- U.63

TRN SENSTVTY TO YRW 01.

ISLUG-FTNFTI I

71 POINTS PLOTTED

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

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HERN- 20.0 SGRR- 65.6 71 POINTS PLOTTED EGS ......................................................................................

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

......... . L . . . . . . . . . . . . . . . . . . . . . . . . . - . . . . . . - . . . . . . . . . . . . . . - .. - -. . - . . . . . . . . - .. -

............................................. . . . . . . . . . . . . . . . -. . . . . . . . . . . . . . . . . . . . . . . . . .

. ...................... . . . . . . . . . . . . . . . . . . . . . . . . . . . ........ . . . . . .~ . . . . . . . . . . . . . . . . -.

__ - - - ___- -. . ._

................. ................................ . . . . . . . . . . . . . . . . . . . . . .-.. . . . .

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

................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............... -----_.---- ......... ....-... ..................

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

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(DECIBELS)

-60.00

-120.01

SPRCE STRTION THREE RXIS C N T R L R O I S T U R B R N C E TORQUE R N R L Y S I . Q 1 S E N S T V T Y T O ROLL OISTURBRNCES

T E S T C F\ CJ E : I X . 11.12, I X Y . I Y Z . 1x2

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Figure 24

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Q 1 SENSTVTY TO ROLL OISTURBRNCES TEST-CRSE: BASELINE CNTRLR 0.8388 R/S

ORTR TIHES: 0000:00:01:U6.U00 TO 0003:17:U9:08.063 OATE PLOTTED: 27-RUG-86 201121'46 I X . I Y . 12, I X Y . I Y Z , 1x2 1.11E*08.5.22E*07,7.98E+07,0.0.0.0,0.0 INPUTJ'ILE: USERSRCS:CHRRDING.URRS3~~00E3.PLT~215 / 27-RUG-1986 20: lO: l l 9s

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MEAN- -89.3 SGMFI- 16.5 283 POINTS PLOTTE 120.00 ,

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56

5 MDD EXAMPLES

5 . 1 S o l a r Array Fea the r ing

5 .1 .1 S o l a r Array Fea the r ing Example Desc r ip t ion -

The s o l a r a r r a y f e a t h e r i n g a n a l y s i s was performed i n o rde r

t o de te rmine t h e c o s t s a v i n g s , i f any, r e s u l t i n g from moving the

s o l a r a r r a y p a n e l s i n t o a minimum drag p o s i t i o n du r ing each

o r b i t ' s umbra p e r i o d . The a r r a y s are r o t a t e d about the a lpha

j o i n t s o t ha t t h e y are "edge-on'' t o the v e l o c i t y v e c t o r du r ing

umbra and the rby r e p r e s e n t ze ro area f o r a tmospheric drag

computat ions. T h e MDDT program was run once f o r the case when

t h e s o l a r a r r a y s are f e a t h e r e d i n t o the mimimum drag

c o n f i g u r a t i o n and once f o r the case when the a r r a y s are not

feathered. The c o s t d r i v e r f o r t h i s example i s o r b i t decay ra te .

Greater atmospheric drag r e s u l t s i n a higher o r b i t decay ra te

and , consequent ly , higher p r o p e l l e n t - r e l a t e d c o s t s ( i . e . the

amount of p r o p e l l e n t expended and the c o s t of launching

replacement p r o p e l l e n t ) . The MDDT expendables sub rou t ine

(SUBROUTINE EXPD) c a l c u l a t e s t h e decay rate us ing the

use r - supp l i ed i n p u t s i n i t i a l a l t i t u d e , t i m e a t measurement of

i n i t i a l a l t i t u d e , f i n a l a l t i t u d e , and t i m e a t measurement of

f i n a l a l t i t u d e . For t h i s example, these i n p u t s were d e r i v e d

us ing an in-house 3-degree of freedom s c i e n t i f i c s i m u l a t i o n

( r e f e r e n c e 10). T h i s s imu la t ion was e x c e r c i s e d f o r bo th t he

f e a t h e r i n g case and the no- fea ther ing case w i t h r e s u l t s of t h e

d i f f e r e n t Space S t a t i o n a r r a y c o n f i g u r a t i o n s shown i n F i g u r e s 25

and 26. These p l o t s d e p i c t change i n semi-major axis v e r s u s

57

time, the i n p u t s r e q u i r e d by MDDT, as discussed above, t o

c a l c u l a t e the energy r e q u i r e d t o restore the space s t a t i o n t o i t s

o r i g i n a l o r b i t . T h e energy i s t h e n t r a n s l a t e d i n t o pounds of

f u e l and then i n t o a c o s t f o r launch and rep len ishment .

5 . 1 . 2 S o l a r Array Fea ther ing Example Assumptions -

Some key assumptions were made i n c a l c u l a t i n g the o r b i t

decay us ing the in-house s imula t ion , and these assumptions are

described b e l o w . The only use r - supp l i ed i n p u t s r e q u i r e d by the

MDDT program; however, were i n i t i a l a l t i t u d e , t i m e a t measurement

of i n i t i a l a l t i t u d e , f i n a l a l t i t u d e , and t i m e a t measurement of

f i n a l a l t i t u d e .

Orbi t a l t i t u d e . 450 km. i s used f o r a mean o r b i t a l t i t u d e

A l t i t u d e s may va ry from 400 t o 500 k m . ( r e f e r e n c e 6 ) .

I n c l i n a t i o n . 28.5 degrees.

Mean umbra time. An o r b i t a l computer s imula t ion program was

run f o r t h e base l ine Space S t a t i o n o r b i t . A mean umbra per iod of

2071 seconds i s c a l c u l a t e d . P l o t s of t h e umbra data i s seen i n

F igure 27, U m b r a T i m e ve r sus R i g h t Acsension. The computer

r o u t i n e c a l c u l a t e s the mean va lue and p r i n t s t he mean va lue a t

t h e t o p of the p l o t .

Mean array a l p h a a n a l e . T h e a lpha ang le r o t a t e s completely

around each o r b i t ; however, f o r t h e purposes O f drag

c a l c u l a t i o n s , a lpha i s assumed t o va ry from zero t o 90 degrees as

a s i n e wave. A mean a lpha of 63.64 degrees i s assumed as an RMS

58

I

I I I I I 1

a

I I I I a I 1 I

v a l u e of a s i n e wave. During umbra the average a lpha ang le

becomes 11.7 degrees.

Mean solar beta a n @ l e . A mean s o l a r beta ang le can be

c a l c u l a t e d from geometry o f t h e earth, sun. and o r b i t

i n c l i n a t i o n . The same program which c a l c u l a t e s umbra p e r i o d a l s o

c a l c u l a t e s s o l a r beta a n g l e s . R e s u l t s of a n a l y s i s p r e d i c t a RMS

beta a n g l e of 36.7 derees. The p l o t of beta a n g l e v e r s u s r i g h t

a scens ion over the p e r i o d of a yea r i s shown i n F igu re 28 w i t h a

maximum beta ang le of 52 degrees. As i n the case o f the a lpha

a n g l e , an RMS v a l u e f o r the beta a n g l e i s c a l c u l a t e d as 36.8

degrees. T h i s assumes t h a t beta varies as a s i n g l e s i n e wave

w i t h z e r o mean and peak va lue of 52 .0 degrees.

p a 6 coe f f i c i e n t . A va lue of 2 . 2 i s used f o r t h i s a n a l y s i s .

Drag c o e f f i c i e n t s f o r s p a c e c r a f t a n a l y s i s va ry from one

r e f e r e n c e source t o t h e n e x t . The extremes f o r drag c o e f f i c i e n t

found i n t he l i t e r a t u r e are a low of 2 . 0 t o a h igh of 2 . 6

( r e f e r e n c e s 11, 12, and 13). Values of 2.2 seemed t o be the most

widely used .

O r b i t decav t i m e u e r i o d . O r b i t decay rate i s non- l inear

over extended p e r i o d s of t i m e as seen i n F igu re 29. For the

purposes of t h i s example, a 1 0 day o r b i t a d j u s t i n t e r v a l i s

assumed. -

Hydrazine i s the assumed p r o p e l l e n t . T h e no - fea the r ing case

i s approximated by c a l c u l a t i n g o r b i t decay assuming a f r o n t a l

area c o n s i s t i n g of t h e i n i t i a l r e f e r e n c e s t r u c t u r e w i t h a r r a y s i n

59

the average beta and umbra average a lpha p o s i t i o n . T h e

f e a t h e r i n g case i s approximated us ing the r e f e r e n c e s t r u c t u r e

area wi thout s o l a r a r r a y s . O r b i t a d j u s t s are assumed t o occur a t

10 day i n t e r v a l s .

5.1.3 S o l a r Array Fea ther ing Example R e s u l t s -

T h e a n a l y s i s p r e d i c t s t h a t approximately $25.7 m i l l i o n i n

p r o p e l l e n t cost could be saved by f e a t h e r i n g the s o l a r a r r a y s

du r ing umbra.

5.2 Expendables O r b i t Adjust I n t e r v a l

5.2.1 Expendables Example Desc r ip t ion -

A s t h e frequency of o r b i t a d j u s t maneuvers i n c r e a s e s , o r b i t

decay ra te decreases. Thus, t h e longer t he i n t e r v a l between

o r b i t a d j u s t s , t h e more p r o p e l l e n t i s consumed over the same t i m e

pe r iod . To demonst ra te t h i s e f fec t , one case was run w i t h an

i n t e r v a l of 50 days between o r b i t a d j u s t s rather than the nominal

10 days used i n a l l o t h e r cases.

5 . 2 . 2 Expendables Example Assumptions -

Basel ine case, w i t h t i m e between o r b i t a d j u s t s equa l t o 50

days .

60

R 1 I R I P

I 1 I I I 1 c J 1 I I I

5 . 2 . 3 Expendables Example R e s u l t s -

T h e s a v i n g s r e s u l t i n g from performing o r b i t a d j u s t maneuvers

eve ry 10 days rather t h a n every 50 days i s $21,270,000. During

an i n t e r a c t i v e program r u n , i t was found t h a t t h i s the m a j o r i t y

of t h i s s av ing (about 96%) can be a t t r i b u t e d t o sav ings i n t h e

c o s t of launching the replacment expendables . The sav ing i n

p r o p e l l e n t c o s t a lone i s approximately $82,000.

5 . 3 Monopropellent V s . Biprope l l en t

5 . 3 . 1 Monopropellent V s . Biprope l l en t Example Desc r ip t ion -

Some of the same informat ion used i n t h e s o l a r array

f e a t h e r i n g a n a l y s i s was used t o p r e d i c t the more economic

p r o p e l l e n t , g iven the cho ice between monopropellent hydrazine and

a b i p r o p e l l e n t .

5 . 3 . 2 Monopropellent V s . Biprope l l en t Example Assumptions -

The p r o p e l l e n t s used i n t he comparison are N2H4

(monopropellent hydraz ine : ISP=233) and N2H4/N204 (ISP-310).

5 . 3 . 3 Monopropellent V s . Biprope l l en t Example R e s u l t s -

A s i g n i f i c a n t s av ings i s r e a l i z e d by us ing a b i p r o p e l l e n t i n

p l a c e of monopropellent hydraz ine . Over $126,000,000 i s saved

o v e r a l l , most of which i s due t o launch c o s t s a v i n g s .

Approximately $1 ,850 ,000 i n p r o p e l l e n t c o s t i s saved .

61

5.4 Act ive V s Pass ive Damping LCC

5.4.1 Act ive V s Pass ive Damping Example Desc r ip t ion -

A trade s tudy on t h e l i f e c y c l e c o s t of a c t i v e v s pas s ive

damping of the space s t a t i o n was performed. T h e c o n f i g u r a t i o n

cons ide red i s an erectable f i v e meter bay t r u s s d u a l space

s t a t i o n . Various l e v e l s of p a s s i v e s t r u c t u r a l damping were

cons idered . The amount of a c t i v e c o n t r o l r e q u i r e d f o r equ iva len t

performance a t each l e v e l of pas s ive damping was estimated based

on r e s u l t s ob ta ined from previous Independent Research and

Development r e s u l t s .

keel

5.4.2 Act ive V s Pass ive Damping Example Assumptions -

It was assumed t h a t t he pe rcen t damping of t he s t u c t u r e was

p r o p o r t i o n a l t o the percentage of t he s t r u c t u r a l we igh t comprised

of Visco-Elas t ic Material ( V E M ) . In an a c t u a l s t r u c t u r e t h e

ma jo r i ty of t h e damping occurs i n r eg ions of high s t r a i n . Thus

evenly d i s t r i b u t i n g VEM over a l l p o r t i o n s of t he s t r u c t u r e i s

very i n e f f i c i e n t i n terms of w e i g h t . It i s much more e f f i c i e n t

t o apply VEM o n l y t o e lements exper ienc ing large s t r a i n . T h e

amount of damping r equ i r ed f o r 1% damping i s 1% of the w e i g h t of

t h e treated elements . T h i s i s a crude f i r s t c u t approximation of

t he damping.

F o r the space s t a t i o n model employed, i t i s assumed t h a t

only the d iagonal t r u s s members r e q u i r e d t rea tment w i t h VEM.

T h i s assumption was made i n order t o have an example and i t has

not been v e r i f i e d t ha t t h i s c o n s t i t u t e s an opt imal t r ea tmen t f o r

62

t h e space s t a t i o n . T r e a t i n g on ly members wi th h igh s t r a i n

c e r t a i n e lements reduces t h e weight p e n a l t y imposed by pass ive

damping.

It was assumed that the a c t i v e c o n t r o l of the s t r u c t u r e was

implemented employing the e x i s t i n g ACS hardware. Changes i n the

ACS so f tware c o n t r o l law were employed t o account f o r d i f f e r e n t

levels of a c t i v e c o n t r o l r equ i r ed t o achieve similar performance

f o r d i f f e r e n t l e v e l s of damping. The complexi ty , and t h e r e f o r e

c o s t , of the c o n t r o l law is assumed t o be a f u n c t i o n of the

c o n t r o l system bandwidth, the number of s e n s o r s , the number of

c o n t r o l l e r s , and the number o f s t r u c t u r a l modes t h a t have t o be

c o n t r o l l e d . Informat ion from r e f e r e n c e 14 and F igure 30 was

employed t o deve lop a simple c o s t model of the a c t i v e c o n t r o l

so f tware . T h e a c t i v e c o n t r o l sof tware i s asssumed t o c o n s i s t of

three f u n c t i o n a l l y d i s t i n c t p r o c e s s o r s ; the c o n t r o l l a w , t h e

modal c o o r d i n a t e e s t i m a t o r , and the opt imal c o n t r o l g a i n matrix

c a l c u l a t i o n .

The number of o p e r a t i o n s / c y c l e for the c o n t r o l l a w is

inc luded i n the table f o r i n fo rma t ion purposes . The memory

requi rements f o r the compensation i s used t o de te rmine the c o s t

f o r the c o n t r o l law. The ops / cyc le data i s t a k e n d i r e c t l y from a

l i n e a r q u a d r a t i c c o n t r o l l e r used i n a p r i o r IRD e f f o r t ( I n t e r n a l

Research and Development) which i n v e s t i g a t e d a c t i v e s t r u c t u r a l

c o n t r o l .

63

Both t h e e s t i m a t o r and opt imal c o n t r o l g a i n memory

requi rements are d e r i v e d from similar Landsat-D so f tware memory

requi rements . The memory requi rements shown here have been

scaled from Landsat-D by s imple r a t i o s of number of estimated

s ta tes , numbers o f s e n s o r s , and numbers of a c t u a t o r s . Numbers of

l i n e s code are d e r i v e d by an average 2.5:l r a t i o of l i n e s of

macro code f o r t h e NASA s t a n d a r d p rocesso r (NSSC-1) t o number of

words. Again, number of l i n e s of code i s inc luded f o r

i n fo rma t ion only.

of

Cost has been related t o t h e memory requirement f o r each

p rocesso r . A scale of $600/word i s t y p i c a l and i s assumed f o r

these c a l c u l a t i o n s .

5.4.3 Active V s Passive Damping Example R e s u l t s -

Figure 31 p r e s e n t s t h e weight of VEM (Vi sco -E las t i c

Material) r equ i r ed f o r each l e v e l of damping cons idered . By

t r e a t i n g only the d i agona l t r u s s members t h e we igh t p e n a l t y

imposed i s s i g n i f i c a n t l y reduced. A w e i g h t p e n a l t y of 340.

pounds w a s i ncu r red i n achiev ing a z e t a (pe rcen t of c r i t i ca l

damping) of t e n p e r c e n t .

F igu re 32 p r e s e n t s the r e s u l t s of the l i f e c y c l e c o s t trade

s tudy done on active v e r s e s p a s s i v e c o n t r o l . Note t ha t as the

s t r u c t u r a l damping i n c r e a s e s t h e amount of a c t i v e c o n t r o l

r e q u i r e d t o main ta in the same ACS performance d e c r e a s e s . A s can

be s e e n , a s t r u c t u r e w i t h a z e t a of t e n pe rcen t has a l i f e c y c l e

c o s t of 775.3 m i l l i o n d o l l a r s . T h i s i s 1 1 . 2 m i l l i o n d o l l a r s l ess

- ~~ ~~

64

t h a n t h e c o s t of t h e case wi th z e t a equa l t o .05 pe rcen t . The

sav ings are due t o a reduct ion i n t h e c o s t of t h e a c t i v e c o n t r o l

sof tware and occur i n s p i t e of an i n c r e a s e i n t he c o s t of the

s t r u c t u r e .

65

Figure 25

- - 3683.5

ORBIT DECAY DUE TO DRAG: SOLAR ARRAYS FEATHERED DURING UMBRA

1 I I I I I I I I I

""T

DAYS

66

Figure 26

ORBIT DECAY DUE TO DRAG: NO SOLAR ARRAY FEATHERING

3686.0T

L " 0 D

i i7

t A

I S

x3684.5 -\ ..

i \

f N -84.0 \ 3683.5 1 i I 1 I I I I

1 I I 6 8 10 0 2 4

DAYS

67

Figure 27

2uoo. 00

2300.00

2200. oc

2100.0t

UHBRR ( SECONDS

1900.01

1aoo.o

1700.6

1600.C

3PFICE STRTION SIMULRTION RESULTS- JMBRR L E N G T H u n a m 2 . 1 6 a ~ m I . ~ C I O E * O ~

J M B R R LENGTH v s RIGHT ASCENSION OF ASCENDING NODE 'E ST-C FIS E : NCLINRTION 28.50 HERN RLTITUOE uso.oo

IRTA TIMES: OOdO:O~:OO:OO.OOO TO 0000:01:26:23.000 DRTE PLOTTED: 6-HAY-86 0 6 ~ 5 5 1 3 7

0.00 BO.00 120.0 180.0 2 w . 0 900.0

RIGHT ASCENSION OF ASCENDING NODE DEGREES

68

Figure 28

SPRCE STRTION SIMULRTION RESULTS BETR RNGLE BETA 52.0 -51.9

B f T R R N G L E V S RXGHT ASCENSION OF ASCENDING NODE

T E S T C FI S E : ORTA TIHES: 0000: 00: 00: 00.000 TO 00001 01 :26:23.000 DATE PLOTTED: 6-HAY-86 061 5s: 09 INCLINATION : 28.50 HEAN FlLTITUDE t U50.00

I INPUTJILE: USER~ACS:CFREESLRNO.URRS.OBC.YRHJSS.ORT:l / 6-MY-1986 06rllrS8 I 518U POINTS PLOTTED 80.00 DEGS HEAN- 3.929E-06 SCHA- 25.1

60.00

UO. 00

20.00

0. BETR

(DEGREES 1

-20. I O

-UO.OO

-60.00

-80.00 0. 00 60.00 120.8 180. 0 210.0 300.0

RIGHT ASCENSION OF ASCENDING NODE

. .

69

DEGREES

Figure 29

- 3650

DRAG DECAY

1 I I I I 1 I I 1

3690T S E M I M A J 0

. R A X I S

N M

DAYS

70

I

Figure 30

8 8

b bcz E

. . I

k r. '2

I I I

1 I rn

I I I + 'E

% + F a X H f

U c I

71

Zeta

( P e r c e n t )

F igure 31 Weight of Pass ive Damping Treatment

0.1

0.5

1.0

5 . 0

10.

Weight Pena l ty

(Pounds)

(1.

10.

30.

160.

340.

Weight P e n a l t y

(Pe rcen t of T o t a l S t r u c t u r a l Weight)

0.04

0.20

0.38

2.0

4.3

72

Figure 32 Act ive v s Pass ive Cont ro l L i f e Cycle Trade Study

S t r u c t u r a l Damping (Zeta in percen t )

.05 .1 .5 1. 5. 10.

Type of Cost

Non-Recurring Cos t 153.6 153.6 153.7 153.7 154.3 154.9

Launch Cost 37.6 37.6 37.6 37.6 37.9 38.3

Ground Support Cost 20.9 20.9 20.9 20.9 20.9 20.9

Maintainence C o s t 42.0 42.0 42.0 42.0 42.0 42.0

Expendables Cost 503.6 503.6 503.6 503.6 503.6 503.6

Software Cost 20.0 20.0 24.4 24.4 15.5 15.5

T o t a l Cost 706.5 706.6 702.2 782.3 774.2 775.3

ACTIVE VS. PASSIVE CONTROL LCC TRADE STUDY

LE (3 E N O

.05X C A M P I N G

. I % DAMPING

.5Z DAMPING

1 % DAMPING

0 5% DAMPING

10% DAMPIPJG

NON-REC GND SUP EXPO TOTAL

LAUNCH MAIN1 s/w TYPE OF COST

73

6 CONCLUSIONS

In light of the increasing complexity of spacecraft designs,

a need for a design criterion which can be applied to a broad

range of design disciplines is readily recognized. The MDD Study

investigates the use LCC as a comprehensive design criterion to

interrelated spacecraft subsystems design such as controls and

structures. The Multi-Disciplinary Design T o o l developed as part

of the study, uses the relationships between cost and subsystem

design parameters to provide a means for evaluating LCC

sensitivity to design parameters and, therefore, to different

space system designs.

6.1 Advantages Of MDDT

The MDDT computer program is a useful tool for investigating

LCC sensitivities and for conducting subsystem design trades

using LCC as the design criteria. The examples show that MDDT is

a fully operational program capable of performing such analyses.

The examples also show that LCC is an important aspect of system

design and that analyses such as this one can provide significant

cost savings which may outweigh other design criteria.

A program such as MDDT also formalizes the LCC computations

so that, a variety of system design trades can be accomplished

with a high degree of confidence that the same cost consideration

is given to each set of design parameters for any given subsystem

configuration.

74

Much of t he s tudy was directed toward d e r i v i n g

r e p r e s e n t a t i v e v a l u e s f o r the i n p u t parameters s o t h a t i t i s

p o s s i b l e t o u s e the e x i s t i n g program f o r c o s t s e n s i t i v i t i e s t o

these parameters w i t h s imple changes t o t h e i n p u t f i l e .

T h e a r c h i t e c t u r e of MDDT h a s proven t o be f l e x i b l e and

g e n e r a l . MDDT i s modular i n d e s i g n which a l lows the u s e r t o

change the program flow e a s i l y . T h i s i s e s s e n t i a l f o r modifying

the program t o do LCC s t u d i e s beyond t h e c u r r e n t c a p a b i l i t y of

MDDT. T h i s was e s p e c i a l l y apprec i a t ed when the example cases

were i n v e s t i g a t e d .

6 . 2 Genera l User Informat ion

As w i t h any computer t o o l , t he u s e f u l n e s s of the r e s u l t s

depends on the assumptions of t he programmer and accuracy of t he

model. In t he case of MDDT, care should be t a k e n when

i n t e r p r e t i n g t h e r e s u l t s . In g e n e r a l , assumptions are made i n

the LCC model which t e n d t o degrade the accuracy of t he p r e d i c t e d

c o s t s . This is why t h e major assumptions are e x p l i c i t l y stated

i n t h i s r e p o r t . The u s e r i s f u r t h e r cau t ioned t h a t t he model h a s

o t h e r i n h e r e n t i n a c c u r a c i e s . I n r e a l i t y , the d e s i g n v a r i a b l e s

t e n d t o be coupled s o t h a t a small change i n some v a r i a b l e s

create la rge v a r i a t i o n s i n the f i n a l r e s u l t . I n t he MDDT, all

d e s i g n parameters t e n d t o be dependent on less t h a n two o t h e r

parameters (some of the paramters are independent s o t h a t LCC

w i l l v a r y 1:l w i t h t h a t independent parameter which i s due t o t h e

d i f f i c u l t y i n c r e a t i n g a h igh f i d e l t y model a t t h i s p o i n t of t h e

MDDT's development). The a i m o f t h e MDD s t u d y was t o i d e n t i f y

75

t h o s e r e l a t i o n s where parameter in te rdependence was greatest o r

a t least most obvious.

The i n v e s t i g a t o r s have noted the fo l lowing a d d i t i o n a l comments

which are d i r e c t e d t o t he u s e r o r p o t e n t i a l u s e r .

T h e MDDT program i s r e l a t i v e l y w e l l commented w i t h most

parameters de f ined w i t h i n t he subrou t ines where they are used .

T h e MDDT has numerous i n p u t parameters ; more parameters t han

w e o r i g i n a l l y a n t i c i p a t e d . T h i s seems t o be due t o t he ve ry

broad na tu re of the c o s t a s p e c t s of the LCC des ign c r i t e r i a .

Reducing t h e number of i n p u t parameters would r e q u i r e f u r t h e r

a n a l y s i s t o d e f i n e more comprehensive c o s t r e l a t i o n s h i p s .

Reduction could a l s o be achieved by inc lud ing some form of the

a n a l y s i s t o o l s ( s imula t ions ) which were used t o gene ra t e some

of the parameters .

76

7 REFERENCES

1.

2.

3.

4 .

5.

6.

7.

8 .

Fong, F . K . , e t a l , "Space Div is ion Unmanned Spacecraf t Cost

Model", F i f t h Ed i t ion , Space D i v i s i o n / A C C , June 1981.

Bordano,A., "Space S t a t i o n F l i g h t Mode", P resen ta t ion

a t Lyndon B. Johnson Space Center , February 20, 1986.

Mikulas ,Jr . ,M.M.,et al,"Deployable/Erectable Trade

Study For Space S t a t i o n Truss S t r u c t u r e s " , NASA Techical

Memorandum 87573, Ju ly 1985.

McCutchen, D . K . , "Minutes f o r t h e Structures/

Dynamics Technical I n t e g r a t i o n Panel Meeting", Lyndon B.

Johnson Space Center Memo, January 1986.

"Space S t a t i o n D e f i n i t i o n and Preliminary Design, WP-02,

Preliminary Analysis and Design Document (DR-02), Book 8 ,

Guidance, Navigation, and Con t ro l (Sec t ion 4 . 5 ) " . December

1985.

"Space S t a t i o n 5-meter Truss Conf igura t ion (2-Y Plane V i e w ) " ,

Developed from work done a t General Electric Space Systems

Div i s ion , Valley Forge Space Center , f o r Space S t a t i o n WP-03

Con t rac t .

Foulke, H.F., "DISTOR Equations", Control Systems Engineering,

General Electric Space Systems Div is ion , Valley Forge Space

Center.

Frees land , D . C . , Computer programs "DENVAR.FOR", "UMBRA.FOR",

77

9.

10.

11.

12.

13.

14.

15.

16.

Control Systems Engineering, General Electric Space Systems

Division, Valley Forge Space Center.

Harding, R.R., Duran, J.M, Computer program "SPSTA.FOR",

Control Systems Engineering, General Electric Space Systems

Division, Valley Forge Space Center.

Wertz, James R., editor, "Astrophysics and Space Science

Library: Spacecraft Attitude Determination and Control",

Dordrecht, Holland: D. Reidel Publishing Company, 1985.

Cook, G.E. , "Satellite Drag Coefficients", Royal Aircraft

Establishment, Farnborough, Hants.

Davison, Paul H., "Passive Aerodynamic Attitude Stabilization

of Near Earth Satellites", WADD Technical Report 61-133,

Volume 11, Flight Dynamics Laboratory, Aeronautical Systems

Division, A i r Force Systems Command, Wright-Patterson Air

Force Base, Ohio, July 1961.

DeBra, D.B., "The Effect of Aerodynamic Forces on Satellite

Attitude", The Journal of the Astronautical Sciences.

Gehling,R.N.,"Effect of Passive Damping on Active

Energy Requirements",Work performed under PACOSS Contract

F33615-82-C-3222, March 1986.

Covault , Craig, "Orbiter Crew Restores Solar M a x " ,

Avation Week 8 Space Technology, April 16, 1984.

James, T.R., Computer Program "BOEDT.FOR", Software

78

Engineering, General Electric Space Systems Div i s ion , Valley

Forge Space Center.

17. Miller, John, Computer program "JMFSE1. F O R " , Systems

Requirements and Analys is , General Electric Space Systems

D i v i s i o n , Valley Forge Space Center.

18. "Space S t a t i o n Reference Configuration Descr ip t ion" ,

Systems Engineering and Integrat ion, Space S ta t ion Program

Office, August 1984.

79

E

APPENDIX A

SPACE STATION DISTURBANCE SIMULATIONS

A- 1

SPACE STATION DISTURBANCE SIMULATIONS

Figure A-1: Crew Kickoff, ACS Inactive, ACS X-axis Deflection.

M X

D E F

R A D

A T

A C S

~ 1 0 ~ ~ 0 + 8

0.6

0 t 4

0t2

8t0

-0t2 0 20 TIME(SEC 1

A-2

40 60 80 100 I I I 1 1

SPACE STATION DISTURBANCE SIMULATIONS

Figure A-2: Crew Kickoff, ACS Inactive, ACS Y-axis Deflection.

X

m Y

D E F

R A D

A T

A C S

A-3

SPACE STATION DISTURBANCE SIMULATIONS

Figure A-3: Crew Kickoff, ACS Inactive, ACS 2-axi

SPACE S T A T I O N MDDT DAMPING t.0005 DUAL KEEL, ACS INACTIVE

X ~ O - 5 STUDY ~8 z CREW K I C K O F F M z

Deflection.

I I

E -0.05 F

R A D

A T

A C S

-0.10

-0.15

-0.20

-0 25 0 20 40 .TIME(SEC)

A-4

1 1 I

a 80 100

m Y

D E F

R A D

A T

SPACE STATION DISTURBANCE SIMULATIONS

Figure A-4: Crew Kickoff, ACS Inactive, Lower Boom Tip. Y-axis Deflection.

T * L B

SPACE STATION MDDT DAMPING =.0005 DUAL KEEL, ACS INACTIVE STUDY xxg z CREW KICKOFF

0.6

0 *

0,

-0.

0 20 40 TIME(SEC) "TLB: TIP OF LOWER BOOM

60 80 108

A-5

2

A c C

G S

A T

T * L B

SPACE STATION DISTURBANCE SIMULATIONS

Figure A-5: C r e w Kickoff, ACS Inac t ive , Lower Boom Tip. Z-axis Acceleration.

e * 2 r 1 J

0*1

0 * 0

-0.1

-0 *2 0 20 TIME(SEC1

"TLB: TIP OF LOWER BOOM

A-6

I

40 0 80 100

SPACE STATION DISTURBANCE SIMULATIONS

Figure A-6: Crew Kickoff, ACS Active, ACS X-axis Deflection.

SPACE STATION MDDT ~ 1 0 - 4 STUDY z CREW KICKOFF

- DAFlPING =e0005 DUAL KEEL, ACS ACTIVE fl x D E F

R A D

A T A C S

8 . 4 ' 7

0,

0.

0.

0 .

-8.1 0 20 TIME(SEC)

40 I I

1 E

I 1 8 1 U

A - 7

SPACE STATION DISTURBANCE SIMULATIONS

Figure A-7: Crew Kickoff, ACS Active, ACS Y-axis Deflection.

rl Y

D E F

R A D

A T

A C S

SPACE STATION MDDT

DAMPING =,0005 DUAL I&, ACS ACT x ~ o - ~ STUDY z CREW K I C K O F

0 . 5 , i

0 20 TIME(SEC)

40 I

A-8

a 80 100 I I B I 8 1

SPACE STATION DISTURBANCE SIMULATIONS

Figure A-8: Crew Kickoff, ACS Active, ACS Z-axis Deflection.

M 2

D E F R A D

A T

A C S

SPACE STATION MDDT

DAMPING p.0005 DUAL KEEL, A C S ACT XI@-5 STUDY x x x z CHEW KICKOFF

0.10 - I - - -

0.05 - - - -

0*08

-0 05

-0.10

-0.15 0 20 TIME(SEC1

A-9

40 c

VE

80 100

r4 v D E F R A D

A T

L B 7"

SPACE STATION DISTURBANCE SIMULATIONS

Figure A-9: Crew Kickoff, ACS Active, Lower Boom Tip. Y-axis Deflection.

0.4

0 * 2

0.0

1 i I 0 I

. T I M E ( S E C 1 40 60 E

"TLB: TIP OF LOWER BOOM

A-10

1

1

SPACE STATION DISTURBANCE SIMULATIONS

Figure A-10: C r e w Kickoff, ACS Active, Lower Boom Tip. Z-axis Acceleration.

SPACE STATION MDDT XIO-3 STUDY x m ~ z CREW KICKOFF

A - DAMPING = * 0 0 0 5 D U A L KEEL, ACS ACTIVE W * d

z I I I

A C C

C S

A T

L B T "

0*1

0 * 8

-0.1

I -0.2 I I I

0 20 40 60 80 100 TIME(SEC 1

*TLB: T i p OF LOWER BOOM

A-11

I SPACE STATION DISTURBANCE SIMULATIONS

Figure A-11: Shuttle Docking, ACS Inactive, ACS X-axis Deflection.

A-12

I I

I I SPACE STATION DISTURBANCE SIMULATIONS

Figure A-12: Shuttle Docking, ACS Inactive, ACS Y-axis Deflection. I

A-13

I 100

SPACE STATION DISTURBANCE SIMULATIONS

Figure A-13: Shuttle Docking, ACS Inactive, ACS Z-axis Deflection.

N z D E F R A D

A T

A C S

S P A C E STATION MDDT ~10-3 STUDY mxx z DOCKING

D A M P I N G z.0005 DUAL KEEL 1 A C S I N A C T I V E 0 . 5 ' 1

I I

0 20 TIME(SEC 1

A-14

40 60

I 1

100 1 1 8 I I I

SPACE STATION DISTURBANCE SIMULATIONS

I N I

Figure A-14: Shuttle Docking, ACS Inactive, Lower Boom Tip. Y-axis Deflection.

M Y

D E F

R

SPACE STATION MDDT Xl0-I STUDY %;Xt Z DOCKING 0 025 DAMPING =e0005 DUAL KEEL, ACS I N A

0 000

A - 0 . m D

A -0.050 T T * B-0.075 L t

t -0.100

-0.125 0 t 3 40 E

*TLB: T I P OF LOWER BOOM

T I V E

-\

I 80 100

A-15

SPACE STATION DISTURBANCE SIMULATIONS

Figure A-15: Shuttle Docking, ACS Inactive, Lower Boom Tip. Z-axis Acceleration.

I 1 I

z A c c G 5

A T

L E T "

1 SPACE S T A T I O N MDDT DAMPING 0,0005 DUAL KEEL, A C S INACTIVE

X10-2 STUDY X%% Z DOCKING I i 1 1

0.2

0.0

-0 *2

-0.4

A-16

SPACE STATION DISTURBANCE SIMULATIONS

Figure A-16: Shuttle Docking, ACS Active, ACS X-axis Deflection.

M X

D E F

R A D

A T

A c S

-0

-0

-0

-0

-0 25 I I I

0 20 TIME(SEC 1

A-17

I I

40 60 80 100

SPACE STATION DISTURBANCE SIMULATIONS

Figure A - 1 7 : S h u t t l e Docking, ACS Active, ACS Y-axis D e f l e c t i o n .

M Y

D E F

R A D

A T

A C S

I

0 i0 40 60 : TIMEtSEC 1

A - 1 8

80

I I 1

SPACE STATION DISTURBANCE SIMULATIONS

Figure A-18: Shuttle Docking, ACS Active, ACS Z-axis Deflection.

M Z D E F

R A D

A T

A C S

SPACE STATION MDDT

DAMPING =.0005 DUAL KEEL, ACS ACTIVE X10-4 STUDY $ X % 2 DOCKING

0.4

0.2

0.0 I -0.2 T

0 20 L

TI f lE(SEC1 3 60 80 100

A - 1 9

SPACE STATION DISTURBANCE SIMULATIONS I Figure A-19: Shuttle Docking, ACS Active, Lower Boom Tip.

Y - a x i s Deflection.

X

fl Y

E F R A D

A T

T *

T I f lE(SEC)

*TLB: T I P OF LOWER BOOM

A-20

I I I I 1 I I I I I

I I

z

I I

A C c G S

SPACE STATION DISTURBANCE SIMULATIONS

Figure A-20: Shuttle Docking, ACS Active, Lower Boom Tip. Z-axis Acceleration.

SPACE STATION MDDT X10-‘ STUDY X X X 2 DOCKING

DAMPING =*0005 DUAL KEEL, ACS ACTIVE

a T

T L B

* 0.0

- 0 * 2

-0,4 0 20

-. T IME(SEC1 4 0 60 E 0

I 100

I

*TLB: TIP OF LOWER BOOM

A - 2 1

APPENDIX B

1 DUAL KEEL REFERENCE CONFIGURATION ACS EQUIPMENT CHARACTERISTICS

B- 1

I I I I I I I I I I I I I I I I I I I I I I I I I I I I I

0 0 0 0 0 o o m . r r r o @ o I rd oooom o o m m o 0 1 -

omooru ' 0 0 m m 0 ~ 0 I O - l n N N h c h t b - I Q

. . . . . . . . . . 4 . I d

N cc F.c* I O N

I &I-& I ! I

0 0 0 0 0 0 0 0 0 0

Q N O O N O r N O 0. FF

* -

. . . . . 1 - I N I I

0 0 0 0 0 0 0 I O O O O O O I O I

8 0 0 0 0 N O 0 0 0

C ? O O ~ e . - * O h 4 . - 0

. . . . . I I I

. . . . . . . OQ-U I

0 4 0 0 ~ 6 0 I I

I bl - . N v) YI

t I I I I 1 I I I I

z z m , O W Q u w o

I

I I I I I I I 1 I I I I i I I 1 I I I I t I I I I I I I I I I I I I I I I I I 1 I I I I I I I I I I I I I I I

m v u i

I I I

I I I

I I ..

.-I I m w a 3 W H E

I I I

I I I l e 1 - I Y Z

I I I I I I I I I

i a

m 1 < W W V X

< < < < e . . . . . . . . . .

NNNNN N ( U N ( V N

. . e . . m m m m m . . . . . N C V N N N

0 . 0 . .

C I - C C I I . . . . . c - - r -

p: W E $ 1

I I I I I I I I I I

B- 2

I I I I I I I I I I I I I I 1 I I I I

. Report NO. NASA CR-178192

Standard Bibliographic Page

2. Government Accession No. 3. Recipient's Catalog No.

. Author(8)

R.R. Harding, J.M. Duran, R.R. Kauffman

~~

. Title and Subtitle 15. Report Date

8. Performing Organization Report No. 87SDS 0 2 4

6. Performing Organization Code The Multi-Disciplinary Design Study - A Life Cycle Cost Algorithm

. Performing Organization Name and Address General Electric Company - Astro Space Division 230 Goddard Boulevard King of Prussia, PA 19406

2. Sponsoring Agency Name and Address

National Aeronautics and Space Administration Washington, D.C. 20546

10. Work Unit No.

11. Contract or Grant No.

NAS1-18032 13. Type of Report and Period Covered

Contractor Report 14. Sponsoring Agency Code

19. Security Classif.(of this report) 20. Security Classif.(of this page) unclassified Unclassified

5. Supplementary Notes

Langley Technical Monitor: Final Report

James L. Williams

21. No. of Pages 22. Price 105

.6. Abstract

Life-cycle cost (LCC) is investigated as a comprehensive design criterion for two major interrelated spacecraft subsystems, Controls and Structures. A Multi-Disciplinary Design Tool (MDDT) is developed to evaluate the sensitivity of LCC to subsystem design parameters. Major costs addressed are: non-recurring; launch: ground support: maintenance: expendables: and software. Examples and results from the MDDT are described, including a structural optimization study between different truss designs; a solar array feathering trade for a minimal drag configuration during umbra: and the cost of active control of a flexible structure is compared against t h e cost of passive damping using visco-elastic material.

17. Key Words (Suggested by Authors(s))

Life-cycle cost, Multi-Disciplinary Design, design criterion, cost sensitivity, attitude control sub- system, structures subsystem, space station

18. Distribution Statement

Unclassified - Unlimited