by Roger T. Schappell, Michuel L, Sulis, Ray Mzreller, Lloyd E.

... https://ntrs.nasa.gov/search.jsp?R=19720018867 2017-10-13T06:33:37+00:00Z

s

“3

N A S A CONT-R-

2

E

REPORT

IMPROVEDGUIDANCEHARDWARESTUDY FOR THESCOUTLAUNCH VEHICLE

.:

: !

,,

by Roger T. Schappell,Michuel L, Sulis, Ray Mzreller, Lloyd E . ‘ Best, Albert J. Bradt, RobertHarrison, and John H. Burrell I

Prepared by

MARTIN MARIETTA CORPORATION Denver, Colo. 80201 for LangZey Research Center

NATIONAL AERONAUTICS AND

SPACE ADMINISTRATION

WASHINGTON, D. 6C.

JUNE 1972

".

TECH LIBRARY KAFB, NM

I

1. Report No.

I

NASA CR-2029

2. Government Accssion No.

GUIDANCE HARDWARE STUDY FOR THE SCOUTLAUNCH

3. Recipient's Catalog

I

5. Report Date

I

4. Title and Subtitle

IMPROVED

I VEHI CLE

No.

June 1972 6. PerformingOrganization Code

7. Author(s) Roger T. S c h a p p e l l ,M i c h a e l Dr. A l b e r t J. B r a d t ,R o b e r t

8. Performing Organization Report No.

E. Best, L . S a l i s , Ray M u e l l e r ,L l o y d H a r r i s o n , and John H. Burrell

MCR-71-158 10. Work Unit No.

9. Performing Organization Name and Address Martin Marietta Corporation 11. Contract or Grant No.

Denver, COI 0.

NASI-10504 13. Type of Report andPeriodCovered 12. SponsoringAgency

Name andAddress N a t i o n a lA e r o n a u t i c sa n d Space A d m i n i s t r a t i o n 20546 Washington, D.C.

C o n t r a c t o rR e p o r t 14. SponsoringAgencyCode

15. SupplementaryNotes

16. Abstract

A m a r k e ts u r v e ya n de v a l u a t i o no fi n e r t i a lg u i d a n c es y s t e m s( I n e r t i a l Measurement U n i t s a n dD i g i t a l Computers) were made. Comparisonswere made t od e t e r m i n et h ec a n d i d a t es y s t e m s Launch V e h i c l e .E r r o ra n a l y s i sw e r e made u s i n gt y p i c a lS c o u tt r a j e c t o r i e s . f o r use i nt h eS c o u t l ystem was s i z e df o rt h ef o u r t hs t a g e . The g u i d a n c eh a r d w a r et oS c o u t A React i o nC o n t r o S veh ic1 e i n t e r f a c e was 1 i s t e d .

I

17. KeyWords(Suggestedby

Author(s)) GuidanceHardwareSurvey Computer S i z i n g R e a c t i o nC o n t r o lS y s t e mS i z i n g TrajectoryErrorAnalysis

18. Distribution Statement

Unclassified

I 19. Security Classif. (of this report)

Unclassified

20. Security Classif.

(of this page)

Unclassified

-

Unl i m i t e d

I 21.

I

NO.

of Pages

245

For sale by the NationalTechnical Information Service, Springfield, Virginia 22151

I 22. Rice* $3.00

FOREWORD T h i sr e p o r tp r e s e n t st h er e s u l t s

anee Harciware Study for theScout

of nine-month Improved GuidLaunch VehicZe. I t i n c l u d e s a

s u r v e y of i n e r t i a lm e a s u r e m e n tu n i t sa n dc o m p u t e r s ,c l o s e d - l o o p t r a j e c t o r ye r r o ra n a l y s i sr e s u l t s ,o p e n - l o o pp e r t u r b a t i o na n a l y s i s a p r e l i m i n a r ys i z i n g r e s u l t s ,l u n a rm i s s i o na n a l y s i sr e s u l t s ,a n d of a f o u r t h - s t a g e r e a c t i o n c o n t r o l s y s t e m a n d a n o r b i t a l c o r r e c t i o n s y s t e mf o r t h e S c o u tl a u n c hv e h i c l e . A s a r e s u l t of t h i s e f f o r t , a r e f e r e n c eg u i d a n c es y s t e mc o n f i g u r a t i o n was s e l e c t e d a n d d e t a i l e d f o r f u r t h e ra n a l y s i s .

iii

-

. ..... .....

.._.

..

"

CONTENTS Page

................................. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1

Summary

S c o u tL a u n c hV e h i c l eC h a r a c t e r i s t i c sa n dC o n s t r a i n t s

..........

................. Computer S i z i n g .S u r v e ya n dS e l e c t i o n .................. I n s t r u m e n t a t i oSny s t e m .........................

G u i d a n c eH a r d w a r eS u r v e ya n dS e l e c t i o n

Q

5 13

26

66 87

C l o s e d - L o oE p r r oA r nalysis

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

107

Open-Loop E r r oA r nalysis

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

117

R e a c t i o nC o n t r o S l y s t e mS i z i n g O r b i t a lC o r r e c t i o nS y s t e m

......................... Recommended G u i d a n c ea n dC o n t r o lS y s t e m . . . . . . . . . . . . . . . . . Guidancesoftware . . . . . . . . . . . . . . . . . . . . . . . . . . . . G u i d a n c eH a r d w a r e / S c o u tV e h i c l eI n t e r f a c i n g ............... G u i d a n c eI n t e g r a t i o nP r o g r a m Summary . . . . . . . . . . . . . . . . . . Recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bibliography .............................. L u n aM r ission Analysis

90 102

129 135 137

160 191 199 200

Appendixes A B C L)

E F

. . . . . . . . . . . . UD-213 T r a j e c t o rPy r o g r a m . . . . . . . . . . . . . . . . . . S p a c eT r a j e c t o r yE r r oA r n a l y s iP s r o g r a m( S T E M ) . . . . . . . l s o p r o b a b i l i t yC o n t o u P r rogram ................ G u i d a n c eS t e e r i n gC o n c e p t s .................. C e n t r a l i z e dE x e c u t i v eS y s t e m .................

T r a j e c t o r yE r r o rA n a l y sP r o g r a m

(TEAP)

201 207 216 217 218 230 thru 237

V

.

Figure

1

I s o p r o b a b i l i t yC o n t o u r s

2

ScouG t u i d a n c ea n a

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

4

. . . . . . . . . . . . S t a n d a r dD e v i a t i o n ir: I n j e c t i o nC o n d i t i o n s . . . . . . . . . . . S c o u tF o u r t h - S t a g eE n v e l o p e . . . . . . . . . . . . . . . . . . .

5

P a y l o a dW e i g h tC a p a b i l i t y S . cout

3

6 7

8 9

10

11 12

13 14

15

16 17

18 19 20 21 22 23

24 25

26 27 28

vi

CmtrcL Blo:I..

niagram

. . . . . . . . . . . . . . . L a u n c h eA r i r - C o o l i n ga n dH e a t i n g . . . . . . . . . . . . . . . . S c o u tV e h i c l e S-172C A m b i e n tP r e s s u r eI n s i d e Heat S h i e l d . . . . S c o u tV e h i c l e F o u r tSht a g e

D

S-131 L o n g i t u d i n a l A c c e l e r a t i o n

. . . . . . . . . . . . . . . . S i n u s o i dVa il b r a t i o n . Lateral Axis . . . . . S i n u s o i dV a li b r a t i oTn h. r uA s tx i s . . . . . . Random V i b r a t i o n . A l l Axes ScoO u tu t s i da enI dn s i dTee m p e r a t u r e s .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

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

AlignmentandGyro

Pitchand

1& 15

17 18

19 20 20

21 22 22

23

43 47

54

Bias

. . . . . . . . . . . . . . . . . . . . . . . . . . . DIGS/AGE/Vehicle I n t e r f a c e s . . . . . . . . . . . . . . . . . . . LCEBlockDiagram . . . . . . . . . . . . . . . . . . . . . . . . T o r q u eD i s t u r b a n c e s Due t oF o u r t h - S t a g eM o t o rB u r n . . . . . . . High-LevelandLow-Level Orientation

12

v s Time a f t e r

. . . . . . . . . . . . . . . . . . . . . . . . . . . . S c o u t S-131 FW-4S Motor Temperature No . 2 v s F l i g h t T i m e . E-Section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . KT-70 P r o j e c t e d P r o d u c t i o n . . . . . . . . . . . . . . . . . T a n g e n tP l a n eC o o r d i n a t eS y s t e m DIGS F u n c t i o nBa l o D c ki a g r a m . . . . . . . . . . . . . . . . . . -

11

f o r Various

F o u r t h - S t a g eR o c k e tM o t o rP e a kS k i nT e m p e r a t u r e s Ignition

S t r a p d o w nP r e f l i g h tC o m p u t a t i o n s Calibration

9

v s Time.

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

A x i a lA c c e l e r a t i o nd u r i n gF o u r t h - S t a g eT h r u s t Payloads

3

55 58

60

93

Y a w L o c a t i o na n d

. . . . . . . . . . . . . . . . . . T y p i c a l Blowdown R e a c t i oCno n t rSo yl s t e m . . R e f e r e n c e RCS System . . . . . . . . . . . . . Standard Jet Configuration . . . . . . . . . Canted Approach . . . . . . . . . . . . . . . . . . . . . . . . L o n g i t u d i n a lM l yo u n t eSdy s t e m

. . . . . .

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

55

57

101 102 103

1c4

29

Direction Reversal of One Pair of Longitudinal Jets

30

Vandenberg AFB Wind Profile. 99% Average Annual

31 32 33 34 35 36 37 38 39

40 41 42 43 44 45 46 47

48 49 50 Tab

. . . . . . .

......... IsoprobabilityContours . . . . . . . . . . . . . . . . . . . . . Error vs Time . . . . . . . . . . . . . . . . . . . . . . . . . . Closed-Loop Guidance System Block Diagram . . . . . . . . . . . . Interfacing of Design Requirements . . . . . . . . . . . . . . . Guidance Software On-Pad Operation . . . . . . . . . . . . . . . . . . . . . . Stable Monolith with Precision Indexing Head . Scout Optical Alignment. Method 3 . . . . . . . IMU Installation in Vehicle . . . . . . . . . .

. . . .

. . . .

. . . . . . . . . . . . Gimbal Servoloop . . . . . . . . . . . . . . . . . . . . . . . . Scout Guidance and Control System Block Diagram . . . . . . . . Signal Flow Diagram of KT-70 Missile Guidance System . . . . . Scout/KT-70InterfacingDiagram . . . . . . . . . . . . . . . . Typical KT-70 Missile System Layout . . . . . . . . . . . . . . SystemBlockDiagram . . . . . . . . . . . . . . . . . . . . . . GuidanceIntegrationTimeSchedule . . . . . . . . . . . . . .

.

Scout Optical Alignment. Method 1

. . . .

. . . .

. . . .

. . . .

. . . .

SchematicRepresentationGimbalSystem

. . . .

. . . .

105 123 127 133 142 158 159 163 165 166 168 169 173

. . . .

184

.

198

175 177 179 189

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

AccelerometerMisalignments

203

Program Flow Chart

208

UD-213 ProgramCoordinateSystem

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

209

le

1

Designation of Scout Configurations .

2

Inertial MeasurementUnit Summary

3

Candidate Inertial Measurement Units for Scout

4

Viking Lander Candidate Systems

35

5 6

Candidate Attitude Reference

38

7 8

9 10

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

33

. . . . . . . . .

34

. . . . . . . . . . . . . . . . . Systems . . . . . . . . . . . . . . .

Miniature and Advanced Technology Inertial Systems

........... . . KT-70 Missile System Error Budget. . . . DIGS Guidance System Characteristics . . IMU Selection Matrix

KT-70 Missile System Characteristics

. . . . . . .

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

.. . . . .

.... ....

7

40 42 45 53 57

vii

........

14

........ C o r r e l a t i obne t w e e n Low a nH d i gA h cceleration . ...... Recommended I n s t r u c t iRo en p e r t o i r e Estimates . . . . . Computer S i z i an T ng di m i n g

15

M a tC roiafxn d i d aCt eo m p u t e r s

11

12

13

LN-30 P h y s i cCahl a r a c t e r i s t i c s

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

19

. . . . . . . . . . . . . . . . . . L e a d i nCga n d i d a C t eo m p u t e fr osGri m b a l e d IMU Application .... . . . . . . L e a d i nCga n d i d a tCeo m p u t e rf soSrt r a p d o wAn p p l i c a t i o n T e l e r c eSt ri g yL n iasl t i n g .................... P e r o x i d e RCS Weight Summary . . . . . . . . . . . . . . . . . . .

20

H y d r a z i nRee a c t i oCno n t r S o ly s t eW meight

21

N i t r o g eRne a c t i oCno n t r oSly s t e S mi z i n g

22

Modified W e i g hPt r o f i l feo r

23

E r r oBru d g ef otSriCxa n d i d a tSey s t e m s

24

la TEAP R e s u l t sf o rt h eS i xC a n d i d a t eS y s t e m sf o rt h e1 7 6 Trajectory

16 17

18

25 26 27

. . . . . . . . . . . . . . . . . . . . . . . . . . . KT-70System . . . . . . . . . . . . . . . . . . . . . . . . . . H-478 System . . . . . . . . . . . . . . . . . . . . . . . . . .

34

lo RSS G u i d a n c eE r r o r s

35

V a r i a n c e s and C o r r e l a t i o n C o e f f i c i e n t s T o t a l System - DIGS a nSd c o u t

36 37 38 39 40 41 42

viii

Definitions

Due t o Three-Axis

86

88 98

109

DIGS S y s t e m

a t O r b iItn j e c t i o n

86

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

30 N o n g u i d a n cEer r o r s

31

81

101

33

30

78

. . . . . . . . .

the P e r o x i dSe y s t e m

32

29

74

99

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

Computer Symbol

63

........ ............. Summary

. . . . . . . . . . . . . . N o m i n aTl r a j e c t o r y Parameters a t F o u r t h - S t a gBe u r n o u t . . . . . . . . . . . . N o n g u i d a nSc y e s t eEmr rSoor u r c e s TARS lo E r r B o ru d g e t Numbers . . . . . . . . . . . . . Nominal S t a t e a t O r b Ii tn j e c t i o n . . . . . . . . . . .

28

62

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

99

111

112 113 114

115 117

118 119 124

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

125

. . . . . .

126

Rate P a c k a g e

a t O r b i tI n j e c t i o n .

. . . . . . . . . . . . . . . . . . Parameters . . . . . . . . . . . . . . . . . . . L u nT a rr a j e c t o r y Delta V R e q u i r e fdoLr u n aO r r b iItn s e r t i o n . . . . . . . . . . . C o n t r o l System . . . . . . . . . . . . . Recommended Guidance and ........................ A l i g c mEernrto r s Missile Computer . . . . . . . . . . . . I n t e r f a c i nS g i g n a lfsr o m . . . . I n t e r f a c i n gS i g n a l fsr o mG u i d a n c ae n dC o n t r oEl l e c t r o n i c s I n t e r f a cSei g n a lfsr o m I n e r t i aPll a t f o r m . . . . . . . . . . . .

126

130 130 136 172 178

181 182

51

........... Interface Signals from Rate Gyros . . . . . . . . . . . . . . . . Interface Signals from Power Transfer Switch . . . . . . . . . . Interface between Guidance System and GSE . . . . . . . . . . . . Physical Characteristics and Power Utilization . . . . . . . . . KT-70 EnvironmentalCapabilities ................ TEAP Output of Individual Errors ................ CovarianceMatrixGeneration .................. GuidanceLogicSummary ......................

52

Minuteman I Guidance Logic Data Sheet

53

Titan I1 Guidance Logic Data Sheet

54

Pclaris Guidance Logic Data Sheet

43 44 45 46 47 48 49 50

Interface Signals from DC Power Conditioner

182 183 183 183 185 185 204 205 219

Pershing Guidance Logic Data Sheet

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . .

. . . . . . . .

220

55

. . . . . . . .

56

. Titan IIIC Guidance Logic Data Sheet . Saturn Guidance Logic Data Sheet . . . Atlas ICBM Guidance Logic Data Sheet . Thor ICBM Guidance Logic Data Sheet . .

. . . . .

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224

57 58 59 60

Titan IIIA Guidance Logic Data Sheet

. . . . .

221 222

223

225

226 227

228

ix

.

.

IMPROVED GUIDANCE HARDWARE STUDY FOR THE SCOUT LAUNCH

VEHICLE

By Roger T. Schappell,Michael L. S a l i s , Ray M u e l l e r , L l o y d E. B e s t , D r . A l b e r t J . B r a d t ,R o b e r tH a r r i s o n , and John H. B u r r e l l M a r t i nM a r i e t t aC o r p o r a t i o n

T h i s r e p o r td o c u m e n t st h er e s u l t so f t h e InprovedGuidanceHarhareStudy L,'Lu ..;(:outi,trLu1c/1 V e i l i c l e , C o n t r a c t NAS1-10504.

for

T h eS c o u tl a u n c hv e h i c l er e q u i r e m e n t s ,c o n s t r a i n t s ,a n dg o a l s a r e summarized. They a r eb a s e d on t h e S c o u t D c o n f i g u r a t i o n ,w h i c hc o n s i s t so ft h eA l g o l I11 f i r s t s t a g e ,C a s t o r TI s e c o n ds t a g e ,A n t a r e s 11 t h i r d s t a g e w i t h o u t t h e e x i s t i n g FW-4s m o t o r ,t h e img u i d a n c eh a r d w a r e ,a n dt h ef o u r t hs t a g ec o n s i s t i n go ft h e p r o v e dg u i d a n c es y s t e m ,t h er e a c t i o nc o n t r o ls y s t e m( R C S ) ,a n dt h er e q u i r e d telem e t r ys y s t e ma n db a t t e r i e s . N i n e t y - e i g h tg i m b a l e da n ds t r a p d o w ng u i d a n c es y s t e m s were i n v e s t i g a t e d f o r T h i s i n c l u d e di n e r t i a lp l a t f o r m sa n d p o s s i b l ea p p l i c a t i o nt ot h eS c o u tv e h i c l e . a t t i t u d er e f e r e n c eu n i t s . A l s o t h en i n ep r o p o s e dV i k i n g A R U s , IMUs, a n d V R U s were c o n s i d e r e da n da r es u m m a r i z e d . A s a r e s u l t of t h i se v a l u a t i o n , 8 systems were s e l e c t e d f o r f u r t h e r e v a l u a t i o n a n d a r e summarized i n m a t r i x f o r m a t a n d i n Guidance Hardware Survey and C a n d i d a t eS e l e c t i o n . d i v i d u a l l y .( S e es e c t i o ne n t i t l e d A s a f u n c t i o no fp e r f o r m a n c e ,c o s t ,r i s k ,a n dw e i g h t ,t h r e es y s t e m s were s e l e c t e d f o rf u r t h e re v a l u a t i o na n dt h e i rr e l a t i v e merits a r e d i s c u s s e d .T h e yc o n s i s to f the s t r a p d o w n D I G S , t h eg i m b a l e d KT-70 missile s y s t e m ,a n dt h e LN-30 n a v i g a t i o n s y s t e m . Due t o the e m p h a s i so nc o s ta n dw e i g h ts a v i n g s ,t h e KT-70 missile s y s t e m was s e l e c t e d a s tlle r e f e r e n c e g u i d a n c e p l a t f o r m f o r t h e i m p r o v e d S c o u t c o n f i g u r a tion. O E 100 c o m p u t e r ss u r v e y e d , 35 were s e l e c t e df o rf u r t h e re v a l u a t i o n . A comwas t h e n i n i t i a t e d f o r c o n t r o l l i n g t h e r e f e r e n c e c l o s e d - l o o p putersizingeffort A s a r e s u l to ft h i ss i z i n ge f f o r t ,s e v e r a l g u i d a n c ea n dc o n t r o lc o n f i g u r a t i o n . c o m p u t e r s were s e l e c t e d as c a n d i d a t e s f o r i n t e g r a t i o n w i t h t h e r e f e r e n c e g u i d a n c e I t s h o u l db en o t e dt h a ts i n c et h eg u i d a n c ea n dc o n t r o ll o g i ch a sn o t platforms. case r e q u i r e m e n t s ,b u t b e e nd e s i g n e d ,t h ec o m p u t e rs i z i n gr e s u l t sr e p r e s e n tw o r s t d on o tc o n s t i t u t et h ef i n a lc o m p u t e rr e q u i r e m e n t s .

)

T h ef o u r t h - s t a g er e a c t i o nc o n t r o ls y s t e mh a sb e e ns i z e df o rt h r e et y p e s of fuel h y d r a z i n e ,h y d r o g e np e r o x i d e ,a n dn i t r o g e n .T h et o r q u ed i s t u r b a n c e s were calculatedandthethrust l e v e l s were e s t a b l i s h e d f o r a b i l e v e l s y s t e m r e s u l t i n g i n a 26-pound h y d r a z i n e r e a c t i o n c o n t r o l s y s t e m , a 2 7 - p o u n dh y d r o g e np e r o x i d es y s tem, o r a 42-pound n i t r o g e ns y s t e m .T h r o u g hs u b s e q u e n tw e i g h tt r a d e o f f s , a was u l t i m a t e l y s e l e c t e d . An o r b i t a l 2 0 - p o u n dh y d r o g e np e r o x i d eb i l e v e ls y s t e m 4.3 extrapoundswasalsosizedusingthe RCS j e t s correctionsystemrequiring t o add o r s u b t r a c t v e l o c i t y a f t e r f o u r t h - s t a g e b u r n . This s i z i n g was b a s e d on vernier c a p a b i l i t y o f 5 3 f p s f o r a 322-pound p r o v i d i n g a l a p o s t - b o o s tv e l o c i t y f o u r t hs t a g e . The t o t a l RCS w e i g h tr e q u i r e df o ra t t i t u d es t a b i l i z a t i o na n d p o s t b o o s tv e l o c i t yc o r r e c t i o n i s t h e r e f o r e2 4 . 3p o u n d s .

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were u s e d f o r e r r o r a n a l y s i s s t u d i e s :

(TEAP) was c h e c k e do u tf o rb o t h The t r a j e c t o r y e r r o r a n a l y s i s p r o g r a m g i m b a l e da n ds t r a p d o w n s y s tems , and was m o d i f i e d t o a c c e p t t h e NASAf u r n i s h e dS c o u tt r a j e c t o r yd a t a .B o t hg i m b a l e da n ds t r a p d o w n inertial s y s t e m sa s w e l l as a t t i t u d er e f e r e n c es y s t e m sh a v eb e e nf l o w nf o r h a r d w a r ep e r f o r m a n c ee v a l u a t i o n .T h es e l e c t e dh a r d w a r er e s u l t e di n l o d i s p e r s i o n s on t h e o r d e r o f 16 f p sa n d4 5 0 0 - f o o tp o s i t i o nu n c e r are due t og u i d a n c eh a r d w a r eo n l y ; t a i n t i e s .T h e s ee r r o r s

The s i m u l a t e d t r a j e c t o r y e r r o r a n a l y s i s p r o g r a m ( S T E M ) was u s e d t o AV m a n e u v e r sf o r t a r g e tf i v el u n a rt r a j e c t o r i e sa n dt oc a l c u l a t et h e m i d c o u r s ea n dl u n a ro r b i ti n s e r t i o n .T h er e s u l t si n d i c a t et h a t , Lunar i?l-ission A n a l basedontheassumptionsinthesectionentitled y s i s , t h eS c o u tv e h i c l e i s p o t e n t i a l l yc a p a b l eo fp l a c i n g 80% of i t s p a y l o a dw e i g h ta f t e rt r a n s l u n a ri n j e c t i o ni n t ol u n a ro r b i t ;

a p o i n t mass, 3 - d e g r e e - o f The UD213 t r a j e c t o r y s i m u l a t i o n p r o g r a m , was u s e dt or u np e r t u r b a t i o na n a l y s i sf o rt h eo p e n freedomprogram, l o o pa t t i t u d e - s t a b i l i z e dS c o u tv e h i c l e .T h er e s u l t so ft h i s simulat i o ni n d i c a t et h a tt h es p i n - s t a b i l i z e df o u r t h - s t a g et i p o f fe r r o r sa r e t h ep r i m a r ys o u r c eo fm i s s i o ne r r o rf o ro p e n - l o o pg u i d a n c e . By u s i n g a 3 - a x i s r a t e packagemountedon a n o n s p i n n i n gf o u r t hs t a g e ,t h e err o r s w i l l b er e d u c e db y a € a c t o rg r e a t e rt h a n2 ; An i s o p r o b a b i l i t y c o n t o u r i n g p r o g r a m w r i t t e n f o r t h i s s t u d y ~ 2 . 1i m p l e m e n t e d on t h e1 1 3 0c o m p u t e rw i t h a Cal Comp p l o t t e r . T h e s e i s o p r o b a b i l i t y c o n t o u r s show t h ed i s t r i b u t i o no fp o s s i b l ec o m b i n a t i o n s o fa p o g e e / p e r i g e ed e v i a t i o n sc o n s i s t e n tw i t h a s p e c i f i e dp r o b a b i l i t y were t h u sc o n t o u r e d f o r e a c hc a r i d i d a t e v a l u e .C o n f i d e n c er e g i o n s g u i d a n c es y s t e m f o r t h e p r e s e n t S c o u t c o n f i g u r a t i o n , f2T t h e g y r J a t t i t u d e - s t a b i l i z e df o u r t h - s t a g ec o n f i g u r a t i - o n ,a n d ~ J L ,the c l o s d l o o pg u i d a n c ec o n f i g u r a t i o n . When s u v e r i m p u s z d , as shown i n E i g u r e 1, i t i s a p p a r e n tt h a tt h ec l o s e d - l o o pg u i d a n c ec o n f i g u r a t i o n is. cptimum f r o mt h ep e r f o r m a n c ep o i n t of v i e w .

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3

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recommends t h a t :

S t a t e - o f - t h e - a r tg u i d a n c ea n dc o n t r o lt e c h n o l o g yb ea p p l i e dt ot h e a s i g n i f i c a n ti m p r o v e m e n t S c o u tl a u n c hv e h i c l e .T h i sw o u l dr e s u l ti n i np e r f o r m a n c ea n dm i s s i o nf l e x i b i l i t y .A v a i l a b l em i n i a t u r eg u i d a n c e h a r d w a r ec a nb ea d a p t e dt ot h eS c o u tv e h i c l ea s sho;\rn i n t h i s r e p o r t ;

A f o r mo fc l o s e d - l o o pg u i d a n c eb ei m p l e m e n t e di nt h ef o u r t hs t a g e , a l o n gw i t h a h o t g a s a t t i t u d e c o n t r o l s y s t e m w i t h a p o s t b o o s tv e l o c itycorrectioncapability; S e v e r a lo t h e ra r e a sb es t u d i e dp r i o rt oh a r d w a r ei m p l e m e n t a t i o n ,

10 y e a r s ,

I n v e s t i g a t i n gf u t u r em i s s i o nr e q u i r e m e n t sf o rt h en e x t S e l e c t i n g a g u i d a n c ea n dc o n t r o ll o g i cf o rS c o u t , I n v e s t i g a t i n gr e d u n d a n c ya n dr e l i a b i l i t yr e q u i r e m e n t s , Investigatingtherelative scout ,

merits o f a d i g i t a l a u t o p i l o t f o r

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a g u i d a n c eh a r d w a r el a b o r a t o r ye v a l u a t i o n .

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i s surmnarized i n t h e

Guidmce I n t e g r a t i o n Program Sununary s e c t i o n .A l t h o u g hg u i d a n c el o g i cs e l e c t i o n was b e y o n dt h es c o p eo ft h i ss t u d y ,t h ec o n s i d e r a t i o n sa n dt r a d e o f f sa r ed i s c u s s e di nt h e Guidmee Sofbdare s e c t i o no f t h i s r e p o r t .

4

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INTRODUCTION T h ep r i m a r yo b j e c t i v eo ft h i ss t u d y was t o i n v e s t i g a . t e t h e u s e ofimproved g u i d a n c ea n dc o n t r o lh a r d w a r ei nt h eS c o u tl a u n c hv e h i c l et h a tw o u l dp r o v i d e i m p r o v e dp e r f o r m a n c ea n df u t u r eg r o w t h .T h i s w a s a c c o m p l i s h e dt h r o u g hh a r d w a r e NASA, s u r v e y s ,c o m p u t e rs i m u l a t i o n ,a n dn u m e r o u st e c h n i c a ld i s c u s s i o n sw i t h LTV-MSD, a n dt h ei n e r t i a lc o m p o n e n t sm a n u f a c t u r e r s . T h i sr e p o r tc o n t a i n st h er e s u l t so f a m u l t i t u d eo fs u r v e y s ,s i z i n g ,a n d of i m p r o v e dg u i d a n c ef o rt h eS c o u t a n a l y s i st a s k sp e r f o r m e di nt h ee v a l u a t i o n l a u n c hv e h i c l e . To a i d i n g a i n i n g a b e t t e ru n d e r s t a n d i n go ft h er e p o r tc o n t e n t a summary of t h e s e q u e n t i a l s e c and t o p l a c e t h e v a r i o u s t a s k s i n p e r s p e c t i v e , t i o n sf o l l o w s . The Summary s e c t i o ns u m m a r i z e st h er e s u l t so ft h ei n d i v i d u a lt a s k sa n di n c l u d e st h es t u d yr e c o m m e n d a t i o n s . A s a p o i n t of r e f e r e n c e , t h i s I n t r o d u c t i o n d e s c r i b e st h ec u r r e n tS c o u t i s f o l l o w e d by suma l a u n c hv e h i c l e and i t s o p e n - l o o pg u i d a n c es y s t e m .T h i s mary of t h e s t u d y a p p r o a c h a n d u l t i m a t e g o a l s .

The Scout Launch V e h i c l e C h a r a c t e r i s t i c s and C o n s t r a i n t s s e c t i o n e s t a b l i s h e s t h ev e h i c l ep h y s i c a l and e n v i r o n m e n t a l c h a r a c t e r i s t i c s a n d g u i d a n c e s y s t e m c o n straintsasprovided by NASA a n d b a s e d o n t h e c u r r e n t S c o u t v e h i c l e .

GuidanceHardbareSurvey and C a n d i d a t e S e l e c t i o n summarizes T h en e x ts e c t i o n , pert h ec a n d i d a t eg u i d a n c eh a r d w a r ec o n s i d e r e di nt h i ss t u d y . The p h y s i c a la n d f o r m a n c ec h a r a c t e r i s t i c s a r e t a b u l a t e d a n d t h e s e l e c t i o n r a t i o n a l e is presented. The Computer Sizing Survey and S e l e c t i o n s e c t i o n p r o v i d e s t h e d a t a a n d r a t i o n a l ef o re s t a b l i s h i n gt h ec o m p u t e rr e q u i r e m e n t s . The r e s u l t s of a m a r k e ts u r vey a r e g i v e na n d a c a n d i d a t e s e l e c t i o n i s p r e s e n t e d b a s e d o n t h e e s t a b l i s h e d requirements. T h e I n s t r u m e n t a t i o nS y s t e m s e c t i o n s u m m a r i z e s t h e p r e l i m i n a r y c h a r a c t e r i s PCM i n s t r u m e n t a t i o n s y s t e m f o r S c o u t .

t i c s of anew

S i n c et h ep r e s e n tS c o u tv e h i c l ee m p l o y ss p i ns t a b i l i z a t i o nf o rt h ef o u r t h s t a g e , a new c o n t r o ls y s t e m is r e q u i r e d .T h en e x t two s e c t i o n s , Reaction Cont r o l S y s t e m S i z i n g and OrbitalCorrectionSystem, c o n s i s t of s i z i n g a n a l y s i s of a c o n t r o ls y s t e mf o rf o u r t h - s t a g ea t t i t u d ec o n t r o l and f o r p o s t b o o s t o r b i t a l correctioncapability. T h et h r e ea n a l y s i ss e c t i o n sp r e s e n te r r o ra n a l y s i sr e s u l t sf o r (1) a c l o s e d ( 2 ) m i s s i o ne r r o r sa s l o o pe v a l u a t i o n of t h ec a n d i d a t eg u i d a n c es y s t e me r r o r s , s o c i a t e dw i t ha no p e n - l o o pg u i d a n c ea p p r o a c h( p r e s e n tS c o u t as well a s a n i m p r o v e dv e r s i o nf e a t u r i n ga na t t i t u t d er e f e r e n c ep a c k a g e on a n o n s p i n n i n gf o u r t h s t a g e ) , and ( 3 ) a n a l y t i c a l r e s u l t s of a d e e p - s p a c e e r r o r a n a l y s i s d e s c r i b i n g t h e o f a ni m p r o v e dS c o u tv e h i c l ei nt e r n s o f t h et r a j e c l u n a rm i s s i o nc a p a b i l i t i e s t o r i e si n v o l v e d ,t a r g e t i n gt h a tc a nb ea c h i e v e d ,a n da d d i t i o n a lf u e lr e q u i r e d .

5

Thesesectionsconsist of t h e CZosed-Loop Error Analysis, Open-Loop Error A m Z y s i s , and Lunar Mission Analysis. Thenextsectionsummarizesthe Reconanended Guidance and ControZ System. A l t h o u g hg u i d a x c cl o g i cd e s i g n w a s beyond t h e s c o p e o f t h i s s t u d y , t h e Guidance SoftFL)me s e c t i o n d i s c u s s e a g u i d a n c e l o g i c c o n s i d e r a t i o n s a n d t r a d e o f f s t o b e c o n s i d e r e di ns u b s e q u e n ts t u d i e s .T h i ss e c t i o ni n c l u d e s a d i s c u s s i o n ofsystem a sumr e q u i r e m e n t s ,t h eg u i d a n c ec o n c e p t sa n dl o g i ct h a tr e q u i r ea n a l y s i s ,a n d m a r yo f? r e s e n tc l o s e d - l o o pg u i d a n c et e c h n i q u e s . H a v i n gs e l e c t e d a r e f e r e n c ec o n f i g u r a t i o n ,t h es y s t e mm o d i f i c a t i o n s ,a l o n g with a p r e l i m i n a r yi x t e r f a c i n gd e f i n i t i o n , are o u t l i n e d i n t h e Guidance Hardware/ScoutVehicleInterfacing section. T h en e x t two s e c t i o n s i n c l u d e a d e f i n i t i v e Guidance I n t e g r a t i o n Program Summary t h a t c o n s i s t s o f a n o v e r a l l p l a n f o r a r r i v i n g a t i m p r o v e dg u i d a n c ef o r S c o u t .T h i s i s f o l l o w e db yt h es t u d y Recommendations s e c t i o n . The f i r s t f o u r a p p e n d i x e s i n c l u d e a d e t a i l e d d e s c r i p t i o n of the c o m p u t e r of t h i ss t u d y .A p p e n d i x E presents s i m u l a t i o np r o g r a m su s e di nt h ep e r f o r m a n c e a c r o s s - s e c t i o ns u r v e yo fg u i d a n c ee q u a t i o n sf o rv a r i o u sl a u n c hv e h i c l e s . Append i x F d i s c u s s e s a c e n t r a l i z e de x e c u t i v es y s t e m as a f u t u r e c o n s i d e r a t i o n .

ScoutLaunchVehicle

T h eS c o u tl a u n c hv e h i c l e w a s d e v e l o p e db yt h eN a t i o n a lA e r o n a u t i c sa n dS p a c e a p a y l o a di n t os p a c eo n A d m i n i s t r a t i o n t o p r o v i d ea ne f f i c i e n tm e a n so fb o o s t i n g a p l a n n e dt r a j e c t o r y .S c o u tb e c a m eo p e r a t i o n a li nJ u l y 1 9 6 0 and has b e e nu s e d f o r l a u n c h i n g a v a r i e t y o fp a y l o a d s ,i n c l u d i n go r b i t a l ,p r o b e ,a n dr e e n t r y miss i o n st h a te n c o m p a s s e di n c l i n e d ,e q u a t o r i a l ,a n dp o l a ro r b i t s . It i s a fouro rf i v e - s t a g es o l i d - p r o p e l l a n tb o o s t e rs y s t e m , 7 2 f e e tl o n gw i t h a l a u n c hw e i g h t of 4 6 , 0 0 0 poundsand a l i f t o f f t h r u s t of 1 4 1 , 9 0 0 p o u n d s .T h ef i f t hs t a g e , though n o tc c n s i d e r e di nt h i ss t u d y , is u s e df o rh i g h l ye l l i p t i c a l and s o l a r o r b i tm i s s i o n s .T h er e f e r e n c ev e h i c l eu s e di nt h i ss t u d y i s t h eS c o u t D ( A l g o l II/Alair 1 1 1 )w i t h a 3 4 - i n c h - d i a m e t e rh e a ts h i e l da n de n I I I / C a s t o rI I A / A n t a r e s t i p s . The S c o u tc o n f i g u r a t i o n s a r e summarized i n l a r g e d j e t v a l v e sa n df i n T a b l e 1, w i t hc o n f i g u r a t i o n s B , C , D, and E i nc u r r e n tu s e .T h eS c o u tv e h i c l e i s e q u i p p e d w i t h a p r e p r o g r a m e do p e n - l o o pg u i d a n c es y s t e mw h e r ee a c he x p e n d e d s t a g es e p a r a t e so n a t i m e ds e q u e n c e .T h ef o u r t hs t a g e i s s p i n - s t a b i l i z e dw i t h is a l i m i t i n g n op r o v i s i o n sf o rt h r u s t .t e r m i n a t i o no rv e r n i e rc o n t r o l .T h i s f s c t o r i n terms vf p e r f o r m a n c e2 n df l e x i b i l i t y . A t w o - p i e c eh e a ts h i e l d i s used i.3 p r o t e c tt h ep a y l o a df r o mh i g ht e m p e r a t u r e sd u r i n ga s c e n ta n d is e j e c t e d j u s t L e f o r et h i r d - s t a g ei g n i t i o n . are p r e s e n t l ya v a i l a b l ea tW a l l o p sI s l a n d , Launch f a c i l i t i e s € o r S c o u t A i r F o r c e Base, C a l i f o r n i a ;a n dF o r m o s aB a y A , fricaT . he V i r g i n i a ;V a n d e n b e r g l a t t e r l a ~ l n c h s i t e i s l o c a t e d on p l a t f o r m s i n t h e I n d i a n O c e a n a b o u t t h r e e miles o f ft h ec o a s t o fK e n y a ,A f r i c a .W a l l o p sS t a t i o n i s u s e dp r i m a r i l yf o re a s t e r l y

6

l a u n c h e s ,t h eV a n d e n b e r g AFEi f o r p o l a r a n d h i g h - i n c l i n a t i o n o r b i t a l l a u n c h e s , and t h eS a nM a r c oe q u a t o r i a lr a n g ef o rl o w - i n c l i n a t i o no r b i t a ll a u n c h e s .T h e are: launch s i t e c o o r d i n a t e su s e di nt h i ss t u d y

_____" ."

2)

Vandenberg Air F o r c e Base, C a l i f o r n i a 1 2 0 . 6 2 3 3 " West l o n g i t u d e ;

3)

SanMarcoTower(off-shore,Kenya) 4 0 . 2 1 2 8 " East l o n g i t u d e .

__ "_

-

FI RST-STAGE

-

"

Algol I Algol I Algol I Algol I Algol I Algol I Algol I1 Algol I I Algol I1 AlgolI1 Algol I1 AlgolI1 AlgolI1 Algol I1 AlgolI1 AlgolI11 Algol I11

x-1

X- 1 A x -2 X-2B

X-2M x-3 X- 3A X-3C X-3A X-3M x-4 X-4A A B C 0

E

*

N o r t hl a t i t u d e ,

-

~~

~-

34,6081'

2.2057"

~

Dummy

Castor I Castor I Castor I Castor I Castor I Castor I Castor I Castor 1 Castor I Castor I Castor I CastorI1 CastorI1 CastorI1 Castor I I CastorI1

OTHER REFERENCE DESIGNATIONS: Algol I - A e r o j eSt e n i o r , 33KS-120,000 Algol I1 - 45KS-100,000

Castor I - XM33E5, XM-75 , 27KS-55,000 Castor I 1 - TX354

~

N o r t hl a t i t u d e ,

S o u t hl a t i t u d e ,

~

THI RD-STAGE

SECOND-STAGE

"

L

" "

FOURTH-STAGE

_"

.

An t a r e s I Antares I Antares I AntaresI1 AntaresI1 AntaresI1 AntaresI1 AntaresI1 AntaresI1 AntaresI1 AntaresI1 AntaresI1 AntaresI1 AntaresI1 AntaresI1 AntaresI1 AntaresI1 -- . .

.

"

.

None Altair I Altair I Altair I A l t a i rI 1 M-2

Altair I Altair I None M-2 A l t a i rI 1 A l t a i rI 1 A l t a i rI 1 A l t a i r 111 A l t a i rI 1 1 A l t a i rI 1 1 A l t a i rI 1 1

-. . .

"

FI FTH -STAGE None None NOTs-17 None None None None NOTS-17 None None None NOTS-17 None None BE -3 None BE-3

- ...____

A l t a i r I - X248, XM-69, 40DS-3100 A1 t a Ii r I - X258, XM-94, 24DS-5850 A1 t a i r I I1 - FW4S , XSR-57-UT NOTS-17, XM-78, NOTS100-17, 43K-882

Antares I - X254, XM-70, 38DS-14,000 BE-3, 9.15-DS-5770 Antares 33DS-21,540 ____I 1 - X259, ~". .. "

-

TABLE 1.- DESIGIVATION OF SCOUT CONFIGURATIONS* "

X

"

37.8479'

W a l l o p sI s l a n d ,V i r g i n i a 7 5 . 4 7 3 9 " West l o n g i t u d e ;

:ONFIGURATION -

-

1)

..

.

.

7

Sincethisstudy is c o n c e r n e d w i t h i m p r o v e d g u i d a n c e h a r d w a r e f o r t h e S c o u t vehicle,thecurrentguidanceandcontroiconcept i s b r i e f l y d- :cri.?,els T h eS c o u tl a u n c hv e h i c l eh a sb e e nf l y i n g a trajectorydefinedby 2 preprois i ne f f e c ta n atgrammed t i m e l a t t i t u d ep r o f i l e .S i n c et h eg u i d a n c es y s t e m t i t u d ec o n t r o ls y s t e m ,t h et i m e l a t t i t u d ep r o f i l e i s a c h i e v e db yt o r q u i n gt h e a r e opera:ed a p p r o p r i a t e r a t e i n t e g r a t i n gg y r o si nd i s c r e t es t e p s .T h eg y r o s i n a rate f e e d b a c kl o o pa n df u n c t i o n as a na t t i t u d er e f e r e n c es y s t e m . They respond t o v e h i c l e rates and a r e a l s o t o r q u e d i n r e s p o n s e t o s i g n a l s f r o m t h o i s l o c a t e di nt h et h i r ds t a g e a s shown i n programmer.Theguidancehardware f i g u r e 2 a n d c o n s i s t s of a n o n c o m p u t a t i o n a lt h r e e - g y r os t r a p p e d - d o w na t t i t u d e r e f e r e n c e u n i t ( I R P ) , a r a t e g y r op a c k a g ef o rs e n s i n gv e h i c l e r a t e s , a relz:J ;~rc-ildp l ~r e c i ? ? u n i t f o r powerand i g n i t i o ns w i c c h i n g ,a ni n t e r v a l o m e t e rt o s c h e d u l i n go fe v e n t sd u r i n gf l i g h t , a progr2mwl;~r t o p r o v i d e v o l c a g e s f o r corq u i n gt h ep i t c ha n d yaw g y r o s f o r c h a n g i n g v e h i c l e o r i e n t a t i o n i n f l i g h t , and t h ea s s o c i a t e di n v e r t e ra n db a t t e r y power s u p p l i e s . An e l e c i r o n i cs w i t c h i n g u n i t ( W E ) i s i n c l u d e df o rc o n t r o l l i n gt h e v a l v e s of t h e r e a c t f o x j e t sysLern a c c o r d i n gt ot h ee r r o rs i g n a l sr e c e i v e df r o mt h ea t t i t u d er e f e r e n c e unit.

A p r o p o r t i o n a lc o n t r o ls y s t e mc o n s i s t i n go f j e t vanesandaerodynamiccont r o l s u r f a c e s i s u s e dt oc o n t r o lt h ev e h i c l ed u r i n gt h ef i r s t - s t a g eb u r n .T h e j e t v a n e sp r o v i d et h em a j o rp o r t i o n of t h e c o n t r o l f o r c e d u r i n g t h e thrust p u l s e ,w h e r e a st h ea e r o d y n a m i ct i pc o n t r o l sp r o v i d e a l l t h e c o n t r o l fcrce 2.0-ri n gt n ec o a s tp h a s ef o l l o w i n gf i r s t - s t a g eb u r n o u t .S e c o n d -a n dt h i r d - : ; + a g e c o n t r o l f o r c e s a r e p r o v i d e db yh y d r o g e np e r o x i d er e a c t i o n j e t m o t o r s . 1he f o u r t hs t a g e ,i n c l u d i n gt h ep a y l o a d , i s s p i n - s t a b i l i z e d ,w i t hs p i n n i n gb e i n g i n i t i a t e d a p p r o x i m a t e l y 6 s e c o n d sb e f o r ef o u r t h - s t a g ei g n i t i o n .

StudyApproachandGoals T h eg u i d a n c eh a r d w a r es t u d ya p p r o a c h was t o (1) e s t a b l i s ht h ei m p r o v e d S c o u tv e h i c l eg o a l s , ( 2 ) d e t e r m i n et h ee x i s t i n gv e h i c l ec o n s t r a i n t s , ( 3 ) cond u c t a s u r v e y of g u i d a n c ea n dc o n t r o ls y s t e mh a r d w a r ea n dm i n i a t u r ea i r b o r n e computers,and ( 4 ) c o n d u c t a h a r d w a r ee v a l u a t i o nb yp e r l o r m a n c ea n a l y s i s crcd c o m p u t e rs i m u l a t i o n .A l t h o u g hg u i d a n c el o g i cs e l e c t i o a was beyond t h e s c o p o f t h i ss t u d y ,g u i d a n c el o g i cc o n s i d e r a t i o n s a r e d i s c u s s e di nt h es e c t i o n ent

80

.7 c

0

w

.-a

>

, " o

.6

.5

.4. . . . . . 100 200

. .

m

3 00

. . . . . . . . 400

I n j e c t i o na l t i t u d e ,n .

500

m

I

I

I

600

I

,

,

7 00

mi.

FIGURE 3.- STANDARD DEVIATION I N INJECTION CONDITIONS

11

0 10.00

Limits o f pay1oa.d umbi'i i : a i door 1 0 ~ . jn

1

4" 4 6 '

i'

t, 99.70

A

3

25.00

I

SCOUTLAUNCH

VEHICLECHARACTERISTICS

AND CONSTRAINTS

S i n c et h eS c o u tl a u n c hv e h i c l eh a sb e e nf l y i n gf o ro v e r a decade, its perare w e l l f o r m a n c ea n dp h y s i c a lc h a r a c t e r i s t i c sf o rt h ec u r r e n t - c o n f i g u r a t i o n d e f i n e d .H o w e v e r ,u p o nr e m o v i n gt h ec u r r e n tg u i d a n c ea n dc o n t r o ls y s t e mh a r d ware f r o m t h e t h i r d s t a g e a n d t h e s p i n s t a b i l i z a t i o n h a r d w a r e f r o m t h e t h i r d a n df o u r t hs t a g e s ,a n dt h e ni n s t a l l i n gt h ei m p r o v e dg u i d a n c ea n dc o n t r o ls y s t e m a n u m b e ro fp a r a m e t e r sm u s tb er e d e f i n e da n d esh a r d w a r ei nt h ef o u r t hs t a g e , t i m a t e d .T y p i c a l l y , a t e m p e r a t u r ep r o f i l e i s r e q u i r e df o rt h ef o u r t hs t a g e a new v e h i c l e w e i g h t b r e a k d o w n w i l l resultprovidg u i d a n c es y s t e mc o m p a r t m e n t , i n gd i f f e r e n tf o u r t hs t a g ei n e r t i a s ,p r e l a u n c hv e h i c l ee n v i r o n m e n t a lc h a r a c t e r i s t i c s m u s t b e d e t e r m i n e d ,a n db o o s te n v i r o n m e n t a lr e q u i r e m e n t sm u s tb ed e f i n e d .S e v e r a lo ft h e s ep e r t i n e n tv e h i c l ec h a r a c t e r i s t i c sa n dc o n s t r a i n t s are summarized i n t h i s s e c t i o n . T h e s e d a t a were used i n e s t a b l i s h i n g a r e f e r e n c e f o rh a r d w a r ee v a l u a t i o na n db u d g e t a r yp r i c i n gf o rt h ei m p r o v e df o u r t hs t a g e g u i d a n c ec o n f i g u r a t i o n .

Reference Trajectories The f o l l o w i n g t r a j e c t o r i e s p r o v i d e d b y NASA were used i n M a r t i n M a r i e t t a ' s t r a j e c t o r ye r r o ra n a l y s i sp r o g r a m sf o rg u i d a n c es y s t e mp e r f o r m a n c ec o m p a r i s o n and v e h i c l ea c c u r a c yp r e d i c t i o n : C i r c u l a ro r b i t

176C,

,

a)

Apogee = 6 3 0n .

b)

P e r i g e e = 580 n . m i . ,

c I) n c l i n a t i o n

=

E l l i p t i c a lo r b i t a)

mi.

89.d 9eg; 169C,

Apogee = 1 7 4 2 . 9 8n .

bP ) erigee

mi.,

= 211.1 n. m i . ,

c I) n c l i n a t i o n

=

102.67 deg;

I n j e c t i o nc o n d i t i o n sf o rd i r e c tl u n a ri n j e c t i o nt r a j e c t o r y fromSanMarco, a )V e l o c i t y

=

bP ) osition

= 2 1 , 5 3 5 , 1 9 8f t ,

cE ) ccentricity

3 5 , 8 8 0f p s ,

= 0.9695.

13

T y p i c a lp e r f o r m a n c ec u r v e sf o rr h eS c o u t d i a m e t e rh e a ts h i e l d a r e shown in figure 5 . w e i g h tc a p a b i l i t yf o rc i r c u l a ro r b i t s .

D c o n f i g u r a t i o n w i t h a 34-inchT h e s ec u r v e s i l l r ~ s c r : i t e ;)lyloac!

T h ec u r r e n tS c o u to r b i t a li n j e c t i o nd e v i a t i o n si na l c i i u . i e ,v e l o c i t y ,a n d are shown i n f i g u r e 3 a s a f>,,r.ction f l i g h t p a t h a n g l e a t f o u r t h - s t a g eb t t r r l o u t of i n j e c t i o na l t i t u d e .T h e s ed e v i a c i o n sc a n b e e i t h e rp l u s C J f minaF: m d Ehus d e f i n et h ed e v i a t i o no ne a c hs i d e of t h en o m i n a lv a l u c s h e s t a r d a d deviation i n a z i m u t h a t i n j e c t i o n is + o r -0.625 d e g r e e sa n d i s i n d e p e n d e n t of i n j e c t i o n altitude.

50

100

150

200 250 Payload weight, 1 b

300

350

Note: These curves only valid for 34-inch-diameter heat shields. 42-inch-diameter heat shield reduces payload weight capability 25 l b for a 400 n. mi. circular

-

FIGURE 5.- PAYLOAD WEIGHT CAPABILITY, SCOUT D

14

400

CoolingandThermalControl

P r e l a u n c he n v i r o n m e n t a lc o n t r o l i s p r o v i d e db yp u r g i n gt h ef o u r t hs t a g e p a y l o a da n dg u i d a n c ec o m p a r t m e n t( S e c t i o n E , f i g u r e 4 ) w i t hc o o l e d ,o rh e a t e d , o i l - f r e ea i rt h a th a sb e e nf i l t e r e da n dd r i e db yt h el a u n c h e re n v i r o n m e n t a ls y s tem. T h i ss y s t e mc a ns u p p l y a i r w i t h a maximum h u m i d i t y of 20 p e r c e n t .T h e h e a t i n ga n dc o o l i n gc a p a b i l i t yo ft h ee n v i r o n m e n t a ls y s t e m ,b a s e do n a standard 14.7 p s i a , i s d e f i n e db yt h es h a d e d areas t e m p e r a t u r e of 70°F a n dp r e s s u r eo f o ff i g u r e 6 . T h e s ec o n d i t i o n sa p p l yt ot h e a i r as i t i s s u p p l i e dt ot h eh e a t shield.

E V

m a LL

m

I

I

A

W c,

fu L

TemperatureChangefromLauncherAmbient

-

O F

FIGURE 6 . - LAUNCHER AIR-COOLING AND HEATING P r e f l i g h tH e a t e r

Power

S i n c eg u i d a n c es y s t e m warmup w i l l o c c u ro nt h el a u n c hp a d ,e x t e r n a lp o w e r f r o mt h e AGE p o w e rs u p p l i e s w i l l b e u s e d d u r i n g t h i s p r e l a u n c h p e r i o d .

S t o r a g eL i f e

A s t o r a g el i f eo ff i v ey e a r s

is required.

15

Cooling and Thermal Control Prelaunchenvironmentalcontrol i s providedbypurgingthefourthstage p a y l o a da n dg u i d a n c ec o m p a r t m e n t( S e c t i o n E , f i g u r e 4) w i t h c o o l e d , o r h e a t e d , oil-freeairthathasbeenfilteredanddriedbythelauncherenvironmentalsystem. T h i ss y s t e mc a ns u p p l ya i rw i t h a maximum h u m i d i t y of 20 p e r c e n t .T h e heatingandcoolingcapabilityoftheenvironmentalsystem,based on a s t a n d a r d t e m p e r a t u r e of 7 0 ° Fa n dp r e s s u r e of 1 4 . 7 p s i a , i s d e f i n e db yt h es h a d e da r e a s of f i g u r e 6. T h e s ec o n d i t i o n sa p p l yt ot h ea i ra s i t i s s u p p l i e dt ot h eh e a t shield.

m a

E u

LL

m

I

I

aJ

c, rd

-

-

0

L

0

>

0

W

>

G

Preflight Heater

Power

S i n c eg u i d a n c es y s t e m armu up will o c c u r o n t h e l a u n c h p a d , e x t e r n a l f r o m t h e AGE p o w e r s u p p l i e s will b e u s e d d u r i n g t h i s p r e l a u n c h p e r i o d .

power

StorageLife A storage life

of five y e a r s i s r e q u i r e d .

15

Environmental Thefollowingenvironmentalrequirementsrepresentthe minimum test levels f o r a system i n a v e h i c l e t r a n s i t i o n s e c t i o n a n d d o n o t n e c e s s a r i l y r e p r e s e n t t h e improved guidance hardware qualification levels.

Pressure characteristics.- The p r e s s u r e w i t h i n t h e p a y l o a d h e a t s h i e l d therefore the guidance compartment i s as shown i n f i g u r e 7 .

and

Longitudinal accelerations.- T h e S c o u t a c c e l e r a t i o n p r o f i l e f o r t h e f o u r t h s t a g e i s shown i n f i g u r e 8. Only t h e f o u r t h - s t a g e p r o f i l e i s shown s i n c e i t i s themostsevere.Thesedata are basedon a payload of approximately 45 poundsand r e p r e s e n t t h e m a x i m u m a c c e l e r a t i o n e x p e r i e n c e d t h r o u g h o u t t h e f l i g h t . Figlz-, shows t h ee f f e c t s ofvariouspayloadweights. ShOCn.- The shock requirement for the payload which is l o c a t e d d i r e c t l y abovetheguidancecompartment, is threehalf-sinepulses of 30 g peakamplitudeand 7 t o 13 m i l l i s e c o n d s t o t a l d u r a t i o n . T h i s r e p r e s e n t s t h e i n p u t t o t h e w i l l be located. supporting structure where the guidance hardware

Vibration.- T h e r e q u i r e d v i b r a t i o n t e s t levels are ,shown i n f i g u r e s 1 0 , 11, and12.These are systemoperating t e s t levels andapply a t t h e i n t e r f a c e of i s where t h e g u i d a n c e the forward shoulder of the fourth-stage motor, which hardware w i l l b e l o c a t e d . T h e s i n u s o i d a l v i b r a t i o n tests a n dt h er e q u i r e d l e v e l s are as follows: 1) Q u a l i f i c a t i o n test - Apply onesweep i n each of t h r e e a x e s a t a logarithmic sweep rate n o t g r e a t e r t h a n 2 octaves per minute;

2)

F l i g h ta c c e p t a n c e t e s t - Applyonesweep a logarithmic sweep rate n o t g r e a t e r t h a n

The random v i b r a t i o n t e s t and t h e r e q u i r e d l e v e l s 1 )Q u a l i f i c a t i o n test f o r 2 minutes;

2)

i n each of t h r e e axes a t 4 octaves per minute.

are as f o l l o w s :

- Apply g a u s s i a n random i n each of t h r e e a x e s

F l i g h ta c c e p t a n c e test axes for one minute.

-

Apply g a u s s i a n random i n each of t h r e e

Temperatureenvironment.- The temperature environment w i l l be based on t h e c u r v e s shown i n f i g u r e s 13, 1 4 , and 15.Thesecurvesrepresenttime-varying The guidance temperatureextremes a t t h e i n d i c a t e d p o i n t s i n t h e f o u r t h s t a g e . of s t a t i o n 49 s h a m i n f i g u r e 14.The hardware will b e l o c a t e d j u s t f o r w a r d t y p i c a le x t e r n a lt e m p e r a t u r ec u r v e so ft h ef o z r t h - s t a g em o t o rd u et om o t o rc p e r a t i o n are shown i n f i g u r e 15, and r e p r e s e n t FW4S t w p c r a t u r e s on t h e f o r w a r d dome, motor case middle, and aft motor case from time of i g n i t i o n t o 700 seconds.Thesecurvesrepresent case r a d i a l l o c a t i o n s w h e r e t h e m o s t s e v e r e h e a t ingoccurs.

16

5

-

4

-

2000

1600 .r

ln

n

aJ

b 3

- 5

.a

VI

c

L

1200

ln

5

aJ

c V

9 2

-

n

*E V

800

c

6 1

-

400

0

-

0 10

20

30

6040

50

F l i g h t Time, s FIGURE 7.-

CL U

SCOUT VEHICLE S-172C AMBIENT PRESSURE INSIDE HEAT SHIELD

70

80

0

4

8

12

16

20

24

28

32

26

E l a p s e d time, s

FIGURE 8.-

18

SCOUT VEHICLE 5-131 LONGITUDIllAL ACCELERATION VS T I I K , FOURin STAGE

1

24

Note: 1.

Payload weight i s everything forward o f s t a t i o n 47.77 a s shown i n f i g . 2.

2c

It

li

I

e

4

0

4

8

12

16

Time f r o m f o u r t h - s t a g e i g n i t i o n , FIGURE 9.

I

-

24

20

s

AXIAL ACCELERATION DURING FOURTH-STAGE THRUSTING FOR VARIOUS PAYLOADS

28

3;

-- -

20

30 40

60 80 100

Design q u a l i f i c a t i o n t e s t l e v e l Flight acceptance test level

200

300

500

1000

2000

Frequency, Hz

test i n the l a t e r a l a x i s , t h e a c c e l e r a t i o n a t t h e s p a c e c r a f t center of gravity shall be limited t o +3 g from one-half the f i r s t resonantfrequency o f the spacecraft t o one-and-one-halfthefrequency when vibrated i n e i t h e r of t h e l a t e r a l axes.

N o t e : Duringsinusoidalvibration

FIGURE 10.-

10

20

30 40

SINUSOIDAL VIBRATION,

LATEUL AXIS

60 80 100 200 300 Frequency, Hz

FIGURE 11.- SINUSOIDAL VIBRATION,

20

500

1000

THRUST AXIS

2000

Frequency, Hz

FIGURE 12.- RANDOM VIBRATION, ALL AXES

21

I

Time, s FIGURE 13.-

SCOUTOUTSIDE

AND I N S I D E TEMPERATURES

STA STA STA p49.0-60.0-76.0

-

3

I

200

300

400

500

600

T i m ef r o m i g n i t i o n , FW-4s r o c k e t m o t o r FIGURE 14.-

22

FOURTH-STAGE ROCKET MOTOR P E A KS K I N TEMPERATURES VS T I M EA F T E RI G N I T I O N

700

3

FIGURE 15.- SCOUT 5-131 FW-4s MOTOR TEMPERATURE N0.2 VS FLIGHTTIME,E-SECTION

Wind R e s t r i c t i o n s Wind r e s t r i c t i o n s i m p o s e d on t h e S c o u t l a u n c h v e h i c l e . c o n s i s t o f s u r f a c e w i n d sd u r i n gr a i s i n ga n dl a u n c h i n gt h ev e h i c l e ,w i n d s a t 9 000 t o 1 2 000-foot a l t i t u d e s b a s e d on c o n t r o l a u t h o r i t y l i m i t a t i o n s , a n d w i n d s f r o m 2 7 000 t o 45 000 f e e t b a s e d on m a x i m u m a l l o w a b l eb e n d i n gm o m e n t s .T h e maximum a l l o w a b l e l e v e l sf o re r e c t i o na n dl a u n c h are 4 3 . 5a n d3 5k n o t sr e s p e c t i v e l y ,

F1 i g h t Time A n o m i n a l f l i g h t time of760seconds of b o o s ta n d4 5m i n u t e so fc o a s t u s e di nt h i ss t u d y .D e g r a d e dp e r f o r m a n c ed u r i n gc o a s td u et ot h e r m a lc o n d i t i o n s was c o n s i d e r e da n d w i l l u l t i m a t e l y b e a f u n c t i o no fp a y l o a dr e q u i r e m e n t s .

was

Appl i c a b l e Documents T h ef o l l o w i n gd o c u m e n t s pricing.

were u s e d t o e s t a b l i s h

a referenceforbudgetary

Specifications.Military: MIL-P-llGE( 3) 18 August 1 9 6 7

P r e s e r v a t i o n ,M e t h o d so f

MIL-E-4158C(2) 9 J u l y1 9 6 4

E l e c t r o n i cE q u i p m e n t ,G r o u n d ,G e n e r a l R e q u i r e m e n t s€ o r

MIL-I-6181D 1 June1962

I n t e r f e r e n c eC o n t r o lR e q u i r e m e n t s

MIL-P-7936A Chg 1 7 M P1ra9er6pD c6aherflafoitovrireo rny

Parts Ea qn ud i p mA e netr,o n a u t i c a l ,

MIL-D- 70 32 7 ( 2 ) 2 7 March1962

D r a w i n g s ,E n g i n e e r i n g ,a n dA s s o c i a t e d Lists

24

I1

I

Standards : MIL-STD-129D 28 December 1964

Marking for Shipment and Storage

MIL-STD-130B C/N 1 7 February 1964

Identification Marking of U.S. Military Property

MIL-STD-143A 14 May 1963

Specification and Standards, Order of Procedure for Selectionof

MS33586A 16 December 1958

Metals, Definition of Dissimilar

Pub1 ic a t i o n s :

NASA -: NPC 2 0 0 - 4

August 1964

Hand-Soldering of Electrical Connections, Quality Requirements for

25

--...."-.-"

.. ...

.. -.

GUIDANCE HARDWARE SUR.VEY i\ND SELECTION

T h i ss e c t i o ns u m m a r i z e st h er e s u l t s of t h e i n e r t i a l h a r d w a r e s u r v e y a n d p r o v i d e st h er a t i o n a l e€ o rs e l e c t i n g a r e f e r e n c ec o n f i g u r a t i o n .T h r e ec a t e g o r i e s were c o n s i d e r e d a n d i n c l u d e t h e f o l l o w i n g : o fi n e r t i a lh a r d w a r e I n e r t i a lm e a s u r e m e n tu n i t s l o o pg u i d a n c ec o n f i g u r a t i o n ;

(IMUs) were s u r v e y e d f o r u s e i n

a closed-

A t t i t u d er e f e r e n c eu n i t s (ARU) were s u r v e y e d f o r u s e i n a n o p e n - l o o p guidancescheme similar i n c o n c e p t t o t h e p r e s e n t S c o u t g u i d a n c e s y s t e m w i t ht h ee x c e p t i o nt h a tt h i sh a r d w a r ew o u l db el o c a t e di nt h e f o u r t hs t a g eo fS c o u t ,a l o n gw i t h a r e a c t i o nc o n t r o ls y s t e m as opposed to spin stabilization; D e v e l o p m e n t a ls y s t e m s , i . e . , n e x t - g e n e r a t i o ng u i d a n c eh a r d w a r e i s summ a r i z e df o ri n f o r m a t i o no n l y . I t s h o u l da l s ob en o t e dt h a tf o r comis included. p l e t e n e s s ,t h ec a n d i d a t eV i k i n gi n e r t i a lh a r d w a r e

IMUs, as d i s c u s s e d i n t h i s r e p o r t , are d i f f e r e n t i a t e d f r o m ARUs by t h e f a c t t h a tt h e ya r ec a p a b l eo fp r o v i d i n gv e l o c i t yd a t a as w e l l as a t t i t u d e d a t a , w h e r e a s A R U s p r o v i d ea t t i t u d ed a t ao n l y .A l s o , when d i s c u s s i n gt h eg e n e r i ct y p e of IMUs, p l a t f o r m w i l l b eu s e dt h r o u g h o u tt od e n o t eg i m b a l e ds y s t e m si nc o n t r a s tt os t r a p down s y s tems

.

Approach T h i s e f f o r t was i n i t i a t e d b y f i r s t p r e p a r i n g a n IMIJ q u e s t i o n n a i r e w i t h a p p r o x i m a t e l y 150 d a t ar e q u i r e m e n t s .T h i s was t h e nt r a n s m i t t e dt ot h ei n e r t i a lh a r d w a r e m a n u f a c t u r e r sf o r them t os u m m a r i z e ,i n a c o n s i s t e n tf o r m a t ,t h ec h a r a c t e r i s t i c s o ft h e i rS c o u t - a p p l i c a b l ec a n d i d a t e IMUs. T h en e x ts t e p w a s t oc o n t a c tt h e s e manuf a c t u r e r sa n dd i s c u s st h ea p p l i c a b i l i t y and p r o j e c t e d m o d i f i c a t i o n s o f t h e i r h a r d ware f o rt h eS c o u tb o o s t e r . A s a r e s u l to ft h i ss t u d ya n dp r e v i o u ss t u d i e s , a l i b r a r yc o n t a i n i n gd a t ao n 135 i n e r t i a l s y s t e m s h a s b e e n e s t a b l i s h e d a t t h eM a r t i n Marietta C o r p o r a t i o n .T h i s i s p a r to f a g u i d a n c es y s t e m ,a i r b o r n ec o m p u t e r ,a n d i n e r t i a l c o m p o n e n t sd a t ab a n kc o n t a i n i n gd e t a i l e dd a t ac o n c e r n i n g a l l c u r r e n ta n d The e v a l u a t i o na n df i n a ls e l e c n e x t - g e n e r a t i o ng u i d a n c eh a r d w a r et e c h n o l o g y . t i o n was b a s e d o n t h e l o w e s t e s t i m a t e d c o s t , minimum m o d i f i c a t i o n s and r i s k , minimum w e i g h ta n dp o w e r ,a n dp e r f o r m a n c e .

26

I n p e r f o r m i n gt h i ss t a t e - o f - t h e - a r ts u r v e y b e r of items were c o n s i d e r e d .T h ef o l l o w i n g

of g u i d a n c es y s t e m 11ardware., a numa r e common t oa l ls u b s y s t e m s :

1)

cost;

10)

2)

Weight;

11) s t D a teuvs e; l o p m e n t

3)

Power;

r1e2q) u i rI enm t eernf tasc:e

4)

Size;

13) perM f opar rneluv;flianoccutcsu;r e r ' s

5)

C o o lrienqgu i r e m e n t s ;

14)

6)

T erci hs k n ;i c a l

15) r Se qt ouriar gc ne l e n t s ;

7)

Reliability;.

8)

G r o w tpho t e n t i a l ;

17)

0 J a I i r i c a L i o 1I1I i s L o r v ;

9)

Limitations;

18)

Checkout

Flexibility;

R e q u igrreodsuunpdpe o q r" t

ipnc.nt;

l 1i 6 t e) ; S h e l f

The c r i t e r i a p e c u l i a r t o i n e r t i a l m e a s u r i n g u n i t s

.

are:

A l l of t h e s e items a r e s i g n i f i c a n t i n c h o o s i n g a n IETLI and werc! used i n Llle t r a d e o f fa n dc o s ta n a l y s e s .F u r t h e r m o r e ,t e s td a t a Cram p r o d u c t i o n pro):rams ; ~ n t l t e s t r e p o r t sf r o mo r g a n i z a t i o n ss u c h a s llolloman AFI;, J P L , NASA, C L C ,w e r e I-;](.t o r e di n t ot h ee v a l u a t i o nt oa s s e s st h ea c t u a l IllU p e r f o r m a n c e c n p a h i l i t y . I;oLII IMU a n di n e r t i a lc o m p o n e n td a t a were r e v i e w e d .

Ground r u l e s . - T h eg r o u n dr u l e sa n dg u i d e l i n e s d a t eg u i d a n c eh a r d w a r ef o rt h eS c o u tl a u n c l lv e l l i c l ea r c

usclcI i n CIS

t l l c ~selec,Lion To1low.C;:

1)

1 9 7 1 s t a t e - o f - t h e - a r ht a r d w a r e ;

2)

E s t a b l i s h e dp r o d u c t i o nb a s ep r e f e r r e d ;

3)

No i n e r t i a cl o m p o n e n (t g y r oa n da c c e l e r o m e t e r )d e v e l o p m e n t ;

4)

Minimum p l a t f o r ma n dc o m p u t e rm o d i f i c a t i o n s ;

5)

F l i g h to p e r a t i n g p h a s e (maximum);

or

r;~ncli-

time - 760 s e c o n d sd u r i n gb o o s ta n d4 5 - m i n u t ec o a s t

27

- 50

W e i g h tg o a lf o rc x n p l e t eg u i d a n c es y s t e m

pounds;

Volume g o a l - must f i t w i t h i n 1 8 - i n c h - d i a m e t e r c y l i n d e r , inches long ; Calibrationcycle Location

-

-

9 to 12

90 d a y s o r l o n g e r p r e f e r r e d ;

innonspinningfourthstage;

Linearaccelerationcapability Aximuthalignment Vertical alignment

-

- 30

g alongvehiclethrustaxis;

c body as t h eo r i g i n a ln o m i n a l . The p r o b a b l em a g n i t u d ea n dd i r e c t i o no ft h t ~ ~ i d c o c ~c o s rer e c t i o n deperids on t h ec o n t r o lc o v a r i a n c e b e f o r em i d c o u r s e . If t h e. l i d c o u r s em a n e u v e r were e x e c u t e dw i t h o u te r r o r ,t h e b e e q u a lt ot h ek n o w l e d g ec o v a r i a n c e . c o n t r o lc o v a r i a n c ea f t e r- , l - d c o u r s ew o u l d I n p r a c t i c e ,t h em i d c o u r s r . maneuver' e x e c u t i o n e r r o r m , s t b e a d d e d t o t h e knowl e d g ec o v a r i a F L et oo b t a i i ! the c o n t r o lc o v a r l a n c e . FOUL.p a r a m e t e r s are u s e dt o modelthemidcourse mane1;ver: I

1) R e s o l u t i o ze r r o r - The u n c e r t a i n t y i n d e l t a V r e s u l t i n gf r o m un-c e r z a i n t y in t h r u s t t a i l o f f . A v a l u e of (?.ilC102 km/s, l a , w a s ecsumed;

3)and

4 ) E r r o r j.n t h r u s td i r e c t i o n An 1mcertai.nt.y o f 1 , 5 1!.6;:gr i a l ?:a& o f two o r t h o g o n a l d i r e c t i o n s was assu1i:e:l. L

'

The f i r s t s t e p i n t h e e r r o r a n a l y c i s is t o estah!.i:;:h ;he n w . 1 ::'c~ra midcourse c o r r e c t i o n ,I f no nlidcour.ne is p e r f o r l i . 3 4t h ee r r o r in I: (sqaare r o o t of t h e c' h

maximum e i g e n v a l u e ) was fc_*ILI to h e 20 e!, I !I t r a n s m i t t e r i s recommended i n p l a c e o f tlle c u r r e n ts y s t e m . 'Tot;~l s y s t e mw e i g h t w i l l b e i n tile v i c i n i t y of 12 p o u n d s . T l l i s s y s t e m was s e l e c t e db e c a u s et h ep r e s e n ts y s t e mc a n n o tt r a n s f e r tlle r e q u i r e d a n a l o g ,b i l e v e l ,a n dd i g i t a ls i g n a l sn e c e s s a r yt oi n s t r u m e n t tlle i m p r o v e dg u i d a n c es y s t e m . Tlle r e c o m m e n d e dg u i d a n c ea n dc o n t r o l t a b l e 35.

s y s tern c l l a r a c t e r i s t i c s a r e a s sllowni.n

135

TABLE 38.- RECOMMENDED GUIDANCE AND CONTROL SYSTEM Subsys tern

Weighty Power lb w 15.1 9.7

Characteristics

KT-70 m i s s i l e p l a t f o r m

G . X e! e c t r o n i c s

i r e d for p i c h , roll

1 -purposes memory

>

and yaw 4000 24-bi t

7.0 5.5 1.0 1.5

25.6 75.6

20.0 50.1

50.0

-6.8

20

4. 3 10.1 84.5

167.7

GUIDANCE SOFTWARE A l t h o u g h t h e s p e c i f i c t a s k of d e s i g n i n g t h e g u i d a n c es o f t w a r e is beyond t h e s c o p e of t h i s s t u d y , a g e n e r a l i z e d d e s c r i p t i o n o f t h e n e c e s s a r y p r o c e d u r e s f o r a c o m p l e t eg u i d a n c es y s t e ma p p e a r s t o be q u i t e a p definingtheguidelinesfor propriate.

i s t o c o n t r o l t h e v e h i c l e s t a t e t o satT h ef u n c t i o no ft h eg u i d a n c es y s t e m isiythedesiredfinalconditionswithinprescribedboundsunder normal d i s p e r t h e S c o u t ves i o n si nt h ev e h i c l ep e r f o r m a n c ec h a r a c t e r i s t i c s .T h ea t t i t u d eo f hicleandthefourthstagereactioncontrol j e t s are u s e d a s t h e means of c o n t r o l t oa t t a i nt h er e q u i r e d s t a t e . I n t e l l i g e n c ed e r i v e df r o mt h eg u i d a n c em e a s u r e m e n t u n i ta p p l i e d t o a m a t h e m a t i ca l g o r i t h my i e l d st h er e q u i r e da t t i t u d e st o steer t h e s t a t e . A f t e rt h em o t o r s are d e p l e t e d ,t h eg u i d v e h i c l et ot h ed e s i r e dt a r g e t e d a n c es y s t e mc a nu s et h ec o n t r o l jets t o c o r r e c tf o rv e l o c i t yd i s p e r s i o n s . T h ed e s i g no fg u i d a n c es o f t w a r er e v o l v e sa b o u ts y s t e mi n t e r f a c e s ,g u i d a n c e A l l f a c e t so f a l g o r i t h m st os a t i s f ym i s s i o ng o a l s ,a n dp r e l a u n c hp r o c e d u r e s . t h ev e h i c l es y s t e m ,m i s s i o ng o a l s ,l a u n c h s i t e , a n dE a c i l i t i e sm u s tb e knownand w i l l f u n c t i o ni nt h e a v a i l a b l et oa s s u r et h a tf i n a lg u i d a n c es o i t w a r ed e s i g n p r o p e rm a n n e r .

Requirements The d e s i g np r o c e d u r e is t o e s t a b l i s h t h er e q u i r e r r . e n t sa n de x i s t i n gs y s t e m s for interfacing a n dt h e na p p l yt h i si n f o r m a t i o nt oe s t a b l i s hc l e s i g t lc r i t e r i a w i t h t h e - c o n t r o l s y s t e m , t h eo p e r a t i o n a ls e q u e n c i l l g ,t . e l . c m e t r y ,p r e l a u n c hc h e c k o u t ,a n dm i s s i o na c c u r a c y .T h ea d d i t i o n o f a c l o s e d - l o o pg u i d a n c es y s t e mt h e n i m p o s e sc h a n g e s o f t h ee x i s t i n g . s y s t e m t h a tv o u i d bc, d e f i n e db yt h eg u i d a n c e c o n t r a c t o r a s a change 01- new r e q u i r e m e n t . ;hid g u i d a n c el o g i c i s d e s i g n e d as a f u n c t i o n of t h e c r i t e r i ~ d i c t a t e d b y t h ed e s i g nr e q u i r e m e n t s ,m i s s i o na c c u r a c y , c o s t s ,a n ds u b s e q u e n tr e c u r r i n gc a s t s .

Software design Criteria.T h e g u i d a n c es o f t w a r ed e s i g nr e q u i r e m e n t s a r e de". . ____ ___ r i v e df r o ms p e c i f i c a t i o n s of t h eS c o u tv e h i c l e , i t s m i s s i o n s ,a n da s s o c i a t e d i s u s e da st h eb a s i cg u i d e l i n ef o rt h es p e c i f i cd e s i g n d a t a .T h i si n f o r m a t i o n a n dc h e c k o u tc r i t e r i ao ft h eg u i d a n c es o f t w a r e . ~

~

Mission specification.S p e c i f i c a t i o n so f a m i s s i o n are b a s e d o n t h e r e s u l t s . - . .. . - o f t h ef e a s i b i l i t y of a m i s s i o na n a l y s i s .T h ea n a l y s i si n c l u d e sc o n f i r m a t i o n t h ea p p l i c a b l ev e h i c l et op e r f o r mt h em i s s i o n . T h e s p e c i f i c a t i o n sc o v e r all g e n e r a la r e a sc o n c e r n e dw i t ht h em i s s i o n : "

of

137

V e h i c l et ob eu s e d ; Launch s i t e ; Range s a f e t y c o n s i d e r a t i o n s ; On-pad

t a r g e t i n gr e q u i r e m e n t s ,i fa n y ;

T y p eo fm i s s i o n - - o r b i to rr e e n t r y ; Finalpayload

state;

A c c u r a c yo fr e q u i r e ds t a t e ; Range of l a u n c ha z i m u t h ; P a y l o a do r i e n t a t i o n ; Inflightrequirements. The p r e v i o u ss t a t e m e n t s are g e n e r a l i t i e s a n d o t h e r t y p e s t h a t a r e more s p e c i f i c may b e g i v e n .

o fr e q u i r e m e n t s

misThe m a j o r r e q u i r e m e n t s o f t h e g u i d a n c e e q u a t i o n s a r e d e t e r m i n e d b y t h e s i o ns p e c i f i c a t i o n s . T h et y p e so fm i s s i o n sc o n s i d e r e d are g r o u n d - l a u n c h e do n l y , i nw h i c ht h ef i n a li n j e c t i o n may b e e a r t h o r b i t , r e e n t r y , t r a n s l u n a r , o r o t h e r e a r t h escape o r b i t s . A l t h o u g ht h eg u i d a n c es o f t w a r ee q u a t i o n ss h o u l di d e a l l ya p p l yt oa l lt h e s p e c i f i e dm i s s i o n s ,t h i s i s g e n e r a l l yn o tp o s s i b l eb e c a u s e of t h e d i f f e r e n t a l l missiosls i s t h e m i s s i o n - p e c u l i a rs i t u a t i o n s . T h ep e n a l t yo n ep a y st oc o v e r n e e df o ra nu n n e c e s s a r i l yl a r g ec o m p u t e ru n i tt h a td e g r a d e sv e h i c l ep e r f o r m a n c e p r e d i c t i o n sa n di n c r e a s e sh a r d w a r ec o s t s . T h eo n ee x c e p t i o n i s t h e .lass of m i s s i o n st h a th a st h e same s c h e d u l eo fe v e n t sa n dt h e same t y p e of coi-1.3traints. Forexample, a g u i d a n c es c h e m et h a tp e r m i t s a p a y l o a dt ob el a u n c h e di n t oa n e a r t ho r b i tc a nb es u p p l i e dw i t hc o n s t a n t st ob eu s e df o r a r e e n t r ym i s s i o nt h a t hasnorangeconstraint. The s t a t e - o f - t h e - a r tg u i d a n c ee q u a t i o n sa p p l i c a b l et ot h eS c o u tv e h i c l e are g e n e r a l l y i n two c l a s s e s - - r a n g e - c o n s t r a i n e dr e e n t r ya n do r b i t a lo rs u b o r b i t a l is o n eo ft h e n o n r a n g e - c o n s t r a i n e ds c h e m e s . The t y p eo fm i s s i o n ss p e c i f i e d p r i n c i p a lf a c t o r si n v o l v e di nt h em e t h o do fs E e e r i n gt ob eu s e d . 'The a c c u r a c y r e q u i r e m e n t so ft h em i s s i o n may be s t r i c t enough t o r e n d e r somemethodsunaccepta b l e .I ft h e s er e q u i r e m e n t s a r e t o os t r i n g e n t ,d e v e l o p m e n t time a n dc o s t s will b ei n c r e a s e d . B e c a u s eo fr a n g es a f e t yc o n s t r a i n t so rm i s s i o nr e q u i r e m e n t s , a m i s s i o np r o f i l e may r e q u i r e t h e f l e x i b i l i t y ofdoglegmaneuvers.Thiswouldbeincluded i nt h ed e s i g no ft h es o f t w a r ee q u a t i o n s .

138

k

M i s s i o n st h a t are t a r g e t l t i m e - d e p e n d e n t w i l l r e q u i r et h a tg u i d a n c ep a r a m e ters b e c o n t i n u a l l y u p d a t e d s o t h ep r o p e rt r a j e c t o r yc a nb ef l o w nr e l a t i v et o a r e r e n d e v o u sw i t ho t h e rs o l a r t h e t i m e o fl a u n c h .T h e s et y p e so fm i s s i o n s b o d i e so ro r b i t i n g s a t e l l i t e s . A d d i t i o n a ls o f t w a r e w i l l b e n e c e s s a r y f o r t h i s f u n c t i o n .S i m p l ea n da c c u r a t ep r o c e d u r e sw o u l dp l a c et h es o f t w a r ef o rg u i d a n c e a groundcomputerandinu p d a t ei nt h ea i r b o r n ec o m p u t e rr a t h e rt h a nr e q u i r i n g t e r f a c i n g e q u i p m e n t f o r a c o m p l e xu p d a t i n gp r o g r a m .

Vehiclecharacteristics.A l l ofthevehicleoperatingcharacteristicsmust be known t o i n s u r e p r o p e r i n t e r f a c i n g b e t w e e n t h e v e h i c l e s y s t e m s a n d t h e g u i dance sys tem, including: V e h i c l ec o n f i g u r a t i o nd e s c r i p t i o n ; V e h i c l eo p e r a t i n gs e q u e n c e

of events;

Mass p r o p e r t i e s ; S t r u c t u r a lc o n s t r a i n t s ; H e a t i n gc o n s t r a i n t s ; P r o p u l s i o ns y s t e md a t a ; S t a g i n ga n di g n i t i o nm e c h a n i s m s ; C o n t r o ls y s t e mo p e r a t i o n ; P e r f o r m a n c ec a p a b i l i t y ; Aerodynamic c h a r a c t e r i s t i c s ; P e r t i n e n tv e h i c l ep e r f o r m a n c ed i s p e r s i o n s . T h es e q u e n c eo fe v e n t sa n do t h e re s s e n t i a li n f o r m a t i o nr e l a t i n gt oe a c h of t h eg u i d a n c el o g i c flow. Any d i s c r e t e s t a g e w i l l become a n i n t e g r a l p a r t e v e n ts u c h as a n i n f l i g h t s t a g e i g n i t i o n t h a t i s t ob ec o n t r o l l e db yt h eg u i d a n c es y s t e mm u s tb es p e c i f i e d s o t h ep h y s i c a li n t e r f a c ec a nb ed e s i g n e d .

The g u i d a n c e s o f t w a r e t o i n t e r f a c e w i t h t h e c o n t r o l s y s t e m m i n e db yt h ec h a r a c t e r i s t i c so fe a c hs t a g e ' sc o n t r o ls y s t e m .T h i s is a c h i e v e d . t oa s s u r et h a tt h ep r o p e rv e h i c l ea t t i t u d e

w i l l b ed e t e r w i l l bedone

The v e h i c l e c h a r a c t e r i s t i c s w i l l a l s o b e u s e d i n t r a j e c t o r y s i m u l a t i o n p r o grams t o v e r i f y t h a t c o n s t r a i n t s h a v e n o t b e e n v i o l a t e d a n d t h a t t h e g u i d a n c e p h i l o s o p h yt ob ea p p l i e ds a t i s f i e st h ea c c u r a c yr e q u i r e m e n t sa n d mission r e q u i r e m e n t su n d e ra n ya p p l i c a b l ed i s p e r s e dc o n d i t i o n s .

Guidancehardware.The g u i d a n c e h a r d w a r e i n t e r f a c i n g d a t a i n v o l v e t h e i n e r t i a l m e a s u r e m e n tu n i t ,c o m p u t e ru n i t ,t i m i n gs y n c h r o n i z a t i o n ,a n dp l a t f o r m a l i g n m e n t . The f o l l o w i n gf u n c t i o n sm u s tb ec o n s i d e r e d f o r t h er e s p e c t i v e

139

50bsys L a m :

1)

I n e r t i a l measurementunit, a)

Gimbal axes a l i g n m e n t ,

b)

Gimbalanglemeasurementsystem,

c) Accelerometer measurement system, d)Platform

2)

slew r a t e s ,

e)

Compensable e r r o tre r m s ,

f)

G i m b aal n g l ce o n s t r a i n t s ;

Computer u n i t , I n s t r u c t i o n r e p e r t o i r e, I n s t r u c t i o nc y c l e 8 i ts /words

time,

,

C l o c kf r e q u e n c i e s , A v a i l a b l e memory, D i g i t a l - t o - a n a l c gc o n v e r t e r s , Type of words ( f i x e d , f loatling) ;

140

GuidanceConcepts Theimproved i n e r t i a l p l a t f o r m f o r S c o u t w i l l p r o v i d e a t t i t u d e r e f e r e n c e s r e l a t i v et ot h el a u n c h s i t e when t h e g u i d a n c e s y s t e m g o e s i n e r t i a l , a n d i n t e g r a t i n ga c c e l e r o m e t e r st op r o v i d et h ee f f e c t s of e x t e r n a l f o r c e s a c t i n g on t h e v e h i c l e mass i n the form of t h r e eo r t h o g o n a lc o m p o n e n t s of v e l o c i t y c o u n t s . The known e r r o r s , a n dt r a n s f o r m e dt o a v e l o c i t y terms a r es c a l e d ,c o m p e n s a t e df o r c o n v e n i e n tc o o r d i n a t es y s t e mw h e r e a g r a v i t ym o d e l i s a d d e d .T h e s er e s u l t s are n u m e r i c a l l yi n t e g r a t e di nt h ec o m p u t e ra n dy i e l dp o s i t i o na n dv e l o c i t y a t the measured time. N a v i g a t i o nn e e dn o tb et h i sc o m p l e t e ; i t is s o l e l y a f u n c t i o no f g u i d a n c ee q u a t i o nr e q u i r e m e n t s .

the a t m o s p h e r e The g u i d a n c ea l g o r i t h mu s e dd u r i n gt h ea s c e n tp h a s et h r o u g h may b ed i f f e r e n tt h a nt h a tu s e df o rt h eu p p e rs t a g e s .T h i ss t r i c t l yd e p e n d s on t h e f u n c t i o n a l c h a r a c t e r i s t i c s of t h eu p p e rs t a g eg u i d a n c ep h i l o s o p h y . The g u i d a n c ea l g o r i t h m i s u s e dt oc o m p u t et h ed e s i r e da t t i t u d ea n d p a r e dt o t h e g i m b a la n g l em e a s u r e m e n ti nt h ea p p r o p r i a t ec o o r d i n a t ef r a m e .T h i s s i g n a l i s t h e nu s e dt od r i v et h ev e h i c l ec o n t r o ls y s t e mt oo b t a i nt h er e q u i r e d attitude.

i s com-

i s t of u e ld e p l e t i o n , a n yr e q u i r e dv e l o S i n c et h eS c o u tv e h i c l ef i n a lb u r n c i t y must b e a t t a i n e d by t h e f i n a l s t a g e a t t i t u d e c o n t r o l j e t s . The g u i d a n c e w i l l b e d e s i g n e dt oa u g m e n t t h e b u r n o u t v e l o c i t y by p u l s d u r i n gt h ef i n a ls t a g e ing t h e s ec o n t r o l j e t s i nt h ep r o p e ro r i e n t a t i o n . F i g u r e 33 i l l u s t r a t e st h eg e n e r a li n f l i g h tc l o s e d - l o o pg u i d a n c es y s t e m .

G u i d a n c ee q u a t i o n sa n dl o q i c philosophy.- The s t r u c t u r e of t h eg u i d a n c el o g i c i s d e s i g n e dt ob es y n c h r o n i z e dw i t ht h ev e h i c l eo p e r a t i o n a ls e q u e n c e of e v e n t s .T h i sd o e sn o ti m p l yt h a tt h ev e h i c l es e q u e n c e i s i n d e p e n d e n to ft h e g u i d a n c el o g i c ,o n l yt h a tt h eg u i d a n c es y s t e m w i l l b ec o g n i z a n to ft h es e q u e n c e . The g u i d a n c el o g i c i s u s u a l l y made up i n terms oftwoprimary time c y c l ef r a m e s - are coma m a j o rc y c l ei nw h i c ht h em a i nf r a m en a v i g a t i o na n dg u i d a n c ee q u a t i o n s p u t e d ,a n d a m i n o rc y c l e i n w h i c h a t t i t u d e commands a r e i s s u e d a t a h i g h r a t e , i n s t r u m e n t a t i o nd a t aa r es a m p l e d ,a n dn o r m a l l yt h r u s tt e r m i n a t i o n i s executed. a r e c l a s s i f i e d bytwo c a t e g o r i e s - - e x p l i c i ta n d G u i d a n c es t e e r i n ga l g o r i t h m s i m p l i c i t . The e x p l i c i t form i s b a s i c a l l y a s o l u t i o no ft h et w o - p o i n tb o u n d a r y v a l u ep r o b l e m , i.e., traversing a pathfromaninitial state t o a d e s i r e d f i n a l s t a t e . The s o l u t i o ns h o u l dn o td e g r a d ep e r f o r m a n c et oa n ye x t e n t . The s o l u t i o n i n g e n e r a l i s n o t i n c l o s e df o r m ,b u tr a t h e ra p p r o x i m a t i n gs o l u t i o n s .S i n c e t h e s ea p p r o x i m a t i o n s a r e v a l i d o n l y o v e r s h o r t a r c s , a t t h e commencement of g u i d ancesteeringlargesteeringsignals may r e s u l t b e c a u s e o f t h e i n i t i a l state a n dt h e nc o n v e r g e t o t h ep r o p e rs o l u t i o n as t h ef l i g h tp r o g r e s s e s .T h e s et y p e s o fe q u a t i o n s are n o t t r u l y e x p l i c i t due t ot h ea p p r o x i m a t i o n s .

141

I Gravity mode 1

I I

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1 Guidance logic & equations

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-

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FIGURE 33.-

142

CLOSED-LOOP GUIDANCE SYSTEM BLOCK DIAGRAM

The i m p l i c i t f o r m of g u i d a n c ee q u a t i o n ss o l v e st h et w o - p o i n tb o u n d a r yv a l u e t h r o u g hi n d i r e c tm e a n s .T h em e t h o do fu s i n gt h ea p p l i e de q u a t i o n sd e p e n d so n o t h e rf u n c t i o n st h a t are precomputed. T h e r e are two m a j o r c o n s i d e r a t i o n s i n d e t e r m i n i n g t h e u s e o f a n e x p l i c i t o r i m p l i c i t s e t o fg u i d a n c ee q u a t i o n s .T h ef i r s t i s t h a tt h ei m p l i c i t set generally i s g i v e nb y a smaller s e t of e q u a t i o n st h a nt h ee x p l i c i t s e t . T h i sr e d u c e st h e time t o compute t h eg u i d a n c ef u n c c o r er e q u i r e m e n t so ft h ec o m p u t e r ,t h ec y c l e t i o n ,a n dt h ec o s tb e c a u s e of less c o r er e q u i r e m e n t . I t is a l s os i m p l e rt op r o g r a m .T h es e c o n dc o n s i d e r a t i o n i s t h et a r g e t i n gp r o c e d u r e( g u i d a n c ec o n s t a n t s g e n e r a t i o n )r e q u i r e do fe a c hg u i d a n c et y p e . The i m p l i c i t s e t g e n e r a l l yr e q u i r e s much more e f f o r t t o a r r i v e a t t h e n e c e s s a r y c o n s t a n t s t h a n t h e e x p l i c i t set. T h i si n c r e a s e sr e c u r r i n gc o s t sa n dd o e sn o te a s i l yl e n di t s e l ft of l e x i b l es i t u ations

.

P r o p e rs e l e c t i o no ft h eg u i d a n c ep h i l o s o p h y f l e x i b i l i t y , and complexity

.

is t h u s a t r a d e o f fb e t w e e nc o s t s ,

Guidance Equations

L i n e a r Sine.- The " l i n e a r s i n e ' ' m e t h o d d e s c r i b e d h e r e s a t i s f i e s r a d i a l p o s i t i o na n dv e l o c i t y ,n u l l i n gn o r m a lc o m p o n e n t so fp o s i t i o na n dv e l o c i t yw h i l e simultaneouslysatisfyingtotalvelocity. The p i t c h p l a n e s t e e r i n g

i s d e r i v e d as d i s c u s s e di nt h ef o l l o w i n gp a r a g r a p h s ,

Thetwo-body e q u a t i o n of m o t i o n i n t h e r a d i a l d i r e c t i o n i n p o l a r c o o r d i n a t e s o p e r a t i n gi n a c e n t r a l f o r c e f i e l d :

where

%r -

r

=

radialthrustacceleration,

= g r a v i t a t i o n aa cl c e l e r a t i o n ,

J r = centripetalacceleration. An a s s u m p t i o n is made w i t h r e g a r d t o t h e r a d i a l d i r e c t i o n r e q u i r e d :

143

%r =

A

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+ Bt(' 7

and a

SW

+uv, % J w +w> , , ,+

are a c t u asl e n s e da c c e l e r a t i o n as l o n gt h ied e a l

@wu,

and

$Jv

is a c o n s t a n t m a t r i x f o r a s trapdown system.

202

, U, V , W

are accelerometer misalignment angles

representingmutualnonorthogonalityinradians(Fig.

*C(t)

,

are t h e a c c e l e r o m e t e r b i a s e r r o r s i n ( g )

48).

a gimbaledplatform,but

i s time-dependentfor

Sensitive Axis o f V Accelerometer

U

J

Note:

Misalignments due t o thefactthatthesensitive of theaccelerometerare n o t a1 igned perfectly t o theideal U V W frame.

- axes

Figure 48. - Accel erometer Misal i gnments V acFigure 4 8 d e s c r i b e s t h e ~SJO misalignment angles associated with the is the angle in the VU p l a n e t h a t t h e s e n s i t i v e V a x i s accelerometer. +W c e l e r o m e t e r i s o u t of a l i g n m e n tw i t ht h ed e s i r e d V axis. is t h a t e r r o r i n

+wq

a n g l ei nt h e WJ plane. I t can b e seen t h a t s i x a n g l e s d e s c r i b e t h i s e r r o r . Furtherdefiningcomponents of Eq. ( A 3 ) ,

where

+xo,

and

+zo

t h ei d e a lr e f e r e n c ef r a m e

representthealignmenterroroftheguidancepackageto (XO, YO, ZO) i n r a d i a n s , a n d

SDF is a strapdo1.m f l a g .

203

F$,,

%,

and

Psuy Psv,

qq are

and Psw are t h e g y r o d r i f t

r a t e terms due t o mass imbalancealong

r a t e terms due t o mass imbalancealong

and PIw are t h e g y r o d r i f t

axes o f t h e

theinput

rate terms i n r a d i a n s / s e c o n d ,

U, V, 14 g y r o s , r e s p e c t i v e l y , i n r a d i a n s / s e c o n d / g ,

t h es p i na x e so ft h e

pIu' pIv'

t h en o n - g - s e n s i t i v eg y r od r i f t

clu' clv' clw

U, V, TJ g y r o s , r e s p e c t i v e l y i n r a d i a n s / s e c o n d / g ,

are t h e d r i f t

rate e r r o r s d u e t o m a j o r c o m p l i a n c e ( a n i s o e l a s t i c

effect) i nr a d i a n s / s e c o n d / g 2 ,

DKu, DnJ, BUVY

and DKv are gyrotorquer

em,

evw'

OW'

and

scale f a c t o r e r r o r s i n p e r c e n t a g e ,

eTJv are

and

gyro misalignment angles representing

mutualnonorthogonality.Thesemisalignmentsoccurbecausethesensitiveaxes are n o t p e r f e c t l y a l i g n e d w i t h t h e i d e a l U, V , W frame. of the gyro S i m i l a r l y , as i n t h e a c c e l e r o m e t e r m i s a l i g n m e n t s d e s c r i b e d i n F i g u r e a n g l e s w i l l i d e n t i f y t h e two a n g u l a r e r r o r s o f e a c h g y r o i n p u t a x i s .

. I.$,

$,,

and cp

w

are t h e a c t u a l r o t a t i o n

rates aboutthe

As p r e v i o u s l yd e s c r i b e d t, h e s ee r r o rs o u r c e sd e f i n e to yield velocity error

A:

Al, six

U, V, and W axes. veh '

which i s i n t e g r a t e d

and once again to yield position error.

The outputoftheprogram is formatedtopresentindividual components (X, Y , inertial,ortangential,radial, a n dn o r m a l )o fe a c he r r o rs o u r c e ' sc o n t r i b u t i o n toerrorsinposition a n dv e l o c i t y .T h e s ei n d i v i d u a le r r o r s are root-sums q u a r e dt oo b t a i nt h et o t a l s . The t o t a l s are root-sum-squared f o r b o t h p o s i t i o n a n dv e l o c i t ye r r o rt oo b t a i n one number f o r p o s i t i o n a n d o n e f o r v e l o c i t y . A similar o u t p u t i s p r e s e n t e d f o r t h e a t t i t u d e e r r o r s a s s o c i a t e d w i t h e a c h o f t h e e r r o r s o u r c e s (see t a b l e 4 9 ) .

Z,

TABLE 49

.- TEAPOUTPUT

OF INDIVIDUAL ERRORS

@x0 DB U

cU

n rss from oxo t o n 'rss Prss i rss x rss Yrss Zrss

204

"

" "

A t t i t u d e e r r o r s are p r e s e n t e d as a b o v e e x c e p t e r r o r s formationtoroll,pitch,and yat7 (bodyaxes)

are mapped v i a a t r a n s -

By c a l c u l a t i n g sets o f v e l o c i t y a n d p o s i t i o n e r r o r s f o r e a c h i n p u t s o u r c e e r r o r anddividingeachelementofthe s e t by t h a t i n p u t e r r o r , a m a t r i x ofpart i a l d e r i v a t i v e s may beformed

that yields the errors in the state variablesresultingfrom The s t a t i s t i c a l t r a n s f o r m a t i o n i s t h e n

where

-

= a ( 6 x 6) covariancematrixof

n inputerrorsources

. . .

s t a t e v a r i a b l e s (X, Y , 2, X, Y , Z) and

x-

X

and

= a ( n X 0 ) covariancematrixofinputerrors(includingoff-diagonalcorE state v a r i a b l e sr e s u l t i n g r e l a t i o n terms, i f a v a i l a b l e ) t h a t y i e l d e r r o r s i n t h e frominputerrorsources.

A t t h ee n do fe a c hp o w e r e df l i g h ts e g m e n t ,t h ei n t e g r a t e dv e l o c i t ya n dp o s i t i o n e r r o r s become i n j e c t i o ne r r o r sf o rt h es u b s e q u e n tc o a s tp e r i o d .T h e s e velocity and position errors are p r o p a g a t e d t o l a t e r o r b i t a l times by t a k i n g s p a c e d e r i v a t i v e st h r o u g ht h eK e p l e r i a ne q u a t i o n so fb a l l i s t i cf l i g h t . The STEAP program, which maps t r a j e c t o r y e r r o r s i n deepspace,usesthesecovariancematrices as p a r t of i t s i n p u t ( t a b l e 50).

TABLE 50.- COVARIANCE MATRIX GENERATION

(Individual trajectories) Covariance matrix

B

"2 rl

-

Error coefficients

B-1

20 5

,I

Other outputs generated by the

TEAP program are

(1) The f i n a l t r a j e c t o r y s t a t e r e p r e s e n t i n gs u c ho r b i t a lp a r a m e t e r sa s r a d i u s of p e r i g e e ,r a d i u so fa p o g e e ,v e h i c l ev e l o c i t ym a g n i t u d e , semimajor axis, s e m i l a t u s rectum, e c c e n t r i c i t y ,i n c l i n a t i o n ,p e r i o d , and f l i g h t p a t h a n g l e ;

20 6

2)

The i n d i v i d u a l e r r o r s i n e a c h of t h e a b o v e - s t a t e d o r b i t a l p a r a m e t e r s as a f u n c t i o n of e a c h o f t h e g u i d a n c e h a r d w a r e e r r o r s o u r c e s ;

3)

The a l g e b r a i c sum o ft h e s ee r r o r s ;

4)

The rss o ft h e s ee r r o r s .

APPENDIX B UD-213 TRAJECTORYPROGRAV

Introduction The UD-213 is a p o i n t mass, three-degree-of-freedomtrajectorysimulation a l a r g e v a r i e t y of l a u n c ha n dr e e n t r y program. Its g e n e r a l i z e dn a t u r ea l l o w s vehicles to be simulated in single or multistage modes u n d e r v a r i o u s c o n t r o l l a w s . A s many as 20 phases may b e u s e d t o d e s c r i b e t h e t r a j e c t o r y . E a c hp h a s ec o n s i s t s of a b u r n a n d c o a s t p e r i o d . The program incorporates a s i n g l e a t t r a c t i n g body and general atmosphere model body may beused t h a tc a nb ed e s c r i b e d by i n p u t . A s a r e s u l t , a n y a t t r a c t i n g merely by making t h e a p p r o p r i a t e i n p u t . The equations of motion are s o l v e d i n a p a d - c e n t e r e d i n e r t i a l r e c t a n g u l a r coordinatesystem. The g r a v i t yf o r c e s are c a l c u l a t e di na ne a r t h - c e n t e r e di n e r t i a l s y s t e mt h a t i s p a r a l l e lt ot h ep a d - c e n t e r e ds y s t e m .A u x i l i a r yc a l c u l a t i o n sa l l o w of p o s i t i o n a n d v e l o c i t y i n o t h e r c o o r d i n a t e s y s t e m s a s vel1 forthecomputation as t h e c o m p u t a t i o n o f o t h e r u s e f u l v a r i a b l e s . T h r e e c o m p u t a t i o n a l o p t i o n s may be p o i n t mass, t h r e e - a x i s , o r moment b a l a n c e . used

--

Theprogramhas a s i m u l t a n e o u s i t e r a t i o n f o p t i m i z a t i o n scheme t h a t a l l o w s a s many a s s i x d e p e n d e n t v a r i a b l e s t o b e s a t i s f i e d u s i n g a s many as 12 independent v a r i a b l e s . The g e n e r a l i z e d n a t u r e o f t h e i t e r a t i o n s c h e m ea l l o w st h eu s e rt h e optionofselectingthedependentandindependentvariablesfromanextensive list of available variables. The program flow chart

49.

is p r e s e n t e d i n f i g u r e

Coordinate Systems Theprogram u t i l i z e d s e v e r a l c o o r d i n a t e s y s t e m s t o provideauxiliaryinformat i o n andsuchreferencesystemsforcalculatingoptionaldata as t r a c k e r l o o k a n g l e s , sun-shadows capability,andvariousguidancecontrols.With the a i d of F i g u r e 50, t h e c o o r d i n a t e s y s t e m s are d e s c r i b e d i n t h e f o l l o w i n g p a r a g r a p h s .

xp,

Y p , Z p (plumb line)coordinatesystem.-

5 , Ypr

A rectangular i n e r t i a l coordinate

is e s t a b l i s h e d w i t h i t s o r i g i n s p e c i f i e d by t h e i n i t i a l g e o d e t i c P reference ellipsoid ho. latitude, @ GO ' e a s lt o n g i t u d e X 0' andheightabovethe The Y a x i s is p e r p e n d i c u l a rt o the l o c a l h o r i z o n t a l p l a n e a t l a u n c h ,t h e Xp axis s y s tem

Z

P

207

Start MA1N

1 Yes

CONVERT

No SEARCH

Yes

4

v INITIALIZE TRAJECTORY

BMARKl

I PRINT

I

No

Go t o One o f the Entries o f IIP, Ini ti a1 i ze New

.

f

FIGURE 49.- PROGRAM FLOW CHART 208

N

Legend : XY z x Py P

zP

x;

z;

Y;

Space-fixed inertial coordinate system Launch-centeredgeodetic inertialcoordinate Earth-centered inertial coordinate

'e'e'e 'GM'

OL

'GO

'co

'GM

system

system parallelto

Xp Yp Zp

Earth-centered rotating coordinate systemwith the Xe axis passing t h r o u g h the Greenwich meridian Earth-centeredinertialcoordinate system w i t h the XGM axis passingthroughthe Greenwich mer i d i a n a t launch Flight azimuth measured from true north(deg) Geodetic l a t i tude (deg) Geocentri c 1a t i tude (dcg) Longitude measured e a s t from the Greenwich meridian, (deg)

T

Vernal equinox of Date ~

~

~

~~

FIGURE 50.- UD-213 PROGRAM COORDINATE SYSTEM

~

~~~

209

is inthelocalhorizontalplaneand

Zp axis completestheright-handsystem.

n o r t h ,a n dt h e

u

i s d i r e c t e da l o n ga na z i m u t ho f The

5 , YP

L

f r o mt r u e

p l a n ed e f i n e s

the inertial pitch plane. The equations of motion

the

X;,

Y;,

Zi

$,

Yp,

Z

are s o l v e d i n t h i s c o o r d i n a t e s y s t e m .

- T h i s i n e r t i a l coordinatesystem i s p a r a l l e l t o systemand i s l o c a t e d a t t h ec e n t e ro ft h ee a r t h . I t i s usedto

coordinatesystem.

P calculatethegeocentricradiustothevehicleandtheresultinggravityforce t h a t is requiredtointegratetheequations of motion.

-

X , Y z c o o r d i n a t e S y S tem. To d e f i n e t h e t r a j e c t o r y i n a space-fixedcoordinate system for possible sun-shadow c a p a b i l i t y o r s u b s e q u e n t i n t e r p l a n e t a r y t r a j e c t o r ys t u d i e s ,t h e X, Y , Z coordinatesystem m u s t bedeveloped.Thissystem is a ne a r t h - c e n t e r e di n e r t i a lr e c t a n g u l a rc o o r d i n a t es y s t e m . The X a x i s l i e s i n t h ee q u a t o r i a lp l a n ea n dp a s s e st h r o u g ht h ev e r n a le q u i n o x of d a t e T the Z axis 0' Y axis l i e s i n t h e e q u a t o r i a l p l a n e and passes through the north pole, and the completes the right-hand system. XGM, YGM, ZGM c o o r d i n a t e system.- T h i s c o o r d i n a t e s y s t e m

X axis i n t h e e q u a t o r i a l p l a n e and p a s s i n g Gtl a t launch. The ZGM a x i sp a s s e st h r o u g ht h e

i n e r t i a lc o o r d i n a t es y s t e mw i t ht h e throughtheGreenwich(prime)meridian n o r t hp o l e

and t h e Y

GbI

is a n e a r t h - c e n t e r e d

axis l i e s i nt h ee q u a t o r i a lp l a n ec o m p l e t i n gt h er i g h t - h a n d

s y s tern. Theabove f o u r c o o r d i n a t e s y s t e m s are the fundamental systems used in describingtheequationsofmotion. The f o l l o w i n gc o o r d i n a t es y s t e m s are usedtocompute auxiliary information.

Xey Ye,

-

Ze c o o r d i n a t e system.

The Xey Ye,

and Ze coordinatesystem

is an aux-

i l i a r ys y s t e mu s e dt od e f i n et h es p a c e - f i x e dv e l o c i t yc o m p o n e n t s . The s y s t e m i s e a r t h - c e n t e r e dw i t ht h e X a x i s i n t h ee q u a t o r i a lp l a n ep a s s i n gt h r o u g ht h e Greene and east of wichmeridian a t launch. The Y axis l i e s w i t h i nt h ee q u a t o r i a lp l a n e e t h e X a x i s ,w i t ht h e ze axis d i r e c t e dn o r t ht h r o u g ht h es p i na x i s .T h i sc o o r d i n e ate s y s t e m r o t a t e s w i t h t h e e a r t h .

ZpF coordinatesystem.

'PF''PF'

-

The r a n g e s a f e t y c o o r d i n a t e s y s t e m

earth-fixedy pad-centeredy left-handed coordinate system with the

a t thelaunchpad.

tangenttotheearth from t h en o r t h , from,the

plane.

completesthesystem.

210

%F 'PF axis i s d i r e c t e d a t a n a n g l e

SF

plane u L

axis is p e r p e n d i c u l a rt o ,a n dd i r e c t e do u t w a r d PF The YpF a x i s ,d i r e c t e dt ot h el e f t y andlookingdownrange,

and t h ep o s i t i v e

3F / Y PF

The

is an

Z

-

1, 2 , 3 Body-centered. coordinatesystem. F o r3 - a x i ss i m u l a t i o n s ,a na d d i t i o n a l .o r t h o g o n a lc o o r d i n a t es y s t e m( 1 , 2, 3) is body-fixedwith i t s o r i g i n a t t h ev e h i c l ec e n t e r of g r a v i t y . The l - a x i sc o r r e s p o n d st ot h er o l la x i s ,t h e2 - a x i s correspondstothepitchaxis, and t h e 3-axis c o r r e s p o n d s t o t h e yaw axis.

Planet Model The o b l a t e s p h e r o i d i s c h a r a c t e r i z e d by thesemimajor a x i s , thesemiminor a x i s , the eccentricity of the elliptic section of the oblate spheroid, and t h e r o t a t i o n a l r a t e about i t s s p i n a x i s ( n o r t h p o l e ) . The p o t e n t i a l f u n c t i o n i s c h a r a c t e r i z e d by t h e g r a v i t a t i o n a l c o n s t a n t a t t r a c t i n g body, t h e e q u a t o r i a l r a d i u s , t h e g e o c e n t r i c l a t i t u d e , a n d t h r e e p o t e n t i a l f u n c t i o n terms.

of t h e

The p a r a m e t e r s r e q u i r e d t o d e f i n e t h e a t m o s p h e r i c e f f e c t s are p r e s s u r e r a t i o , d e n s i t yr a t i o ,s p e e do fs o u n d , Mach number,andatmospherictemperature.These p a r a m e t e r s are a f u n c t i o n of a l t i t u d e . Two atmospheremodelsstored i n t h e programusetablelookupstoobtainthe p r e s s u r e andtemperature. The s t o r e dm o d e l s are t h e 624A and1962standardatmospheres. Inthe1963Patrick AFB a t m o s p h e r e , v l h i c h u s e s p o l y n o m i a l s , t h e p r e s s u r e a n d t e m p e r a t u r e are c a l c u l a t e d as f u n c t i o n so fg e o m e t r i ca l t i t u d e .T h e s ep a r a m e t e r s are c a l c u l a t e d i n metric u n i t s a n d c o n v e r t e d t o E n g l i s h u n i t s i f r e q u i r e d .

Numerical Integration The n u m e r i c a l i n t e g r a t i o n which can be selected by input:

i s performedusinganyone

of t h e f o l l o w i n g s c h e m e s ,

1) Predictor-corrector; Fourth-order 4) Runge-Kutta; 2)

Adams-Moulton;

3)

Second-order Runge-Kutta;

5)

Fourth-order modified Runge-Kutta.

211

External Forces Vacuum t h r u s t and p r o p e l l a n t f l o w r a t e may b e i n p u t d i r e c t l y a s a functionof time o r they may b er e p r e s e n t e db y6 t hd e g r e ep o l y n o m i a l s . An o p t i o n a l l o w s t h e axial acceleration to be limited to a specific value. T h e r e a r e two methods f o r c o m p u t i n g n o r m a l f o r c e , d e p e n d i n g o n w h i c h v e h i c l e Themethod f o r computing axial f o r c e o p t i o n( p o i n t mass o r 3-axis) is b e i n gu s e d . is t h e same f o r b o t h o p t i o n s w i t h t h e e x c e p t i o n t h a t t h e axial f o r c e c o e f f i c i e n t may b e i n p u t a s a bivariant function of total angle of attack and Mach number f o r t h e3 - a x i so p t i o n . When u t i l i a i n g t h e 3-axis mode o f s i m u l a t i o n , t h e moment b a l a n c e o p t i o n t h a t calculatestheenginedeflectionsinpitchand yaw r e q u i r e d t o b a l a n c e t h e a e r o dynamicnormaland side forces to produce zero resultant moment c a n b e r e q u e s t e d , The p r e s e n t s i m u l a t i o n a l l o w s f o r a cgandcpoffset i n p i t c h b u t no o f f s e t i n yaw.

Atti tude Control Laws The v e h i c l e a t t i t u d e may b e c o n t r o l l e d u s i n g v a r i o u s c o n t r o l laws for b o t h t h e p o i n t massand t h e 3-axis o p t i o n s . I n t h e p o i n t mass o p t i o n , the v e h i c l e i s instantaneouslyorientedtofollowthespecifiedcontrol law, i . e . , t h e r e are no v e h i c l e rates f o r t h i s o p t i o n e x c e p t f o r i n f o r m a t i o n p u r p o s e s .

i s o r i e n t e d by comnandingbody rates o r Inthe3-axisoption,thevehicle gimbalangle(Euler) rates. For t h i sr e a s o n ,t h ev e h i c l eo r i e n t a t i o n lags t h e commanded o r i e n t a t i o n s l i g h t l y d u e t o c o m p u t a t i o n a l l a g s . The m o u n t of l a g is a f u n c t i o n of t h e s t e p s i z e a n d , f o r m o s t s i m u l a t i o n s , is n e g l i g i b l e . The c o n t r o l laws a v a i l a b l e f o r t h e p o i n t

212

mass and 3-axis o p t i o n are t a b u l a t e d .

POINT MASS

CONTROL LAWS

Vertical fl i g h t Pitchangle of attack6th degree polynomial [ f ( t ) ] Yaw angleofattack,6thdegree polynomial [ f ( t ) ] Zero l i f t ( r e l a t i v e g r a v i t y turn) I n e r t i a l g r a v i t y turn Inertialpitchangleversustime Incremental i n e r t i a1 p i tch angl e Zero i n e r t i a l yaw angle Zero yaw angle o f attack I n e r t i a l yaw angleversus time Incremental i n e r t i a1yaw angle Local horizontalpitchangle THREE-AXIS CONTROL LAWS Vertical fl i g h t Pitchangleofattack6thdegree polynomi a1 [f ( t ) ] Yaw angle of attack, 6th degree polynomial [f ( t ) ] Slideslipangle,6thdegree polynomial [ f ( t ) ] Zero 1i f t ( r e l a t i v e g r a v i t y turn) Inerti a1 gravi ty turn Inertialpitchangleversustime Incremental inerti a1 pitchangle I n e r t i a l yaw angle versus time Incremental i n e r t i a1yaw angle versus time Inertialrollangle Incremental i n e r t i a lr o l la n g l e Constant inertial roll , p i t c h , and yaw r a t e s Local horizontalpitchangle Constantplatform gimbal ansles Local horizontalrollangle

213

Guidance Schemes

An o p e n - l o o p g u i d a n c e o p t i o n t h a t c a l c u l a t e s p i t c h a n d yawcommands basedon c o n s t a n tv a l u e so fp i t c h and yaw g u i d a n c e c o e f f i c i e n t s is a v a i l a b l e . Thecoefficients required to achieve the desired end conditions may b e i t e r a t e d on using the simultaneous iteration scheme. A closed-loopexplicitlinearguidanceoption is a l s o a v a i l a b l e i n t h e 3 - a x i s c o n t r o lo p t i o n . The p i t c ha n d yaw i n e r t i a l a n g l e s are d e f i n e d as l i n e a r f u n c t i o n s of time. The l i n e a r t a n g e n t commands are c a l c u l a t e d by i n t e g r a t i n gf r o mt h e curr e n ts t a g ef o r w a r do v e r a l l s t a g e s and burn times. The s t e e r i n g c o e f f i c i e n t s and time-to-go are determined using a s i m u l t a n e o u s i t e r a t i o n scheme w i t h i n t h e g u i d a n c e logic.

Aerodynamic HeatingCalculations Certainaerodynamicheatingparameterscanbecalculatedandused as dependent v a r i a b l e sf o rt r a j e c t o r y - s h a p i n gp u r p o s e s .O t h e rc a l c u l a t i o n s are performedonly f o ri n f o r m a t i o np u r p o s e s . The f o l l o w i n gh e a t i n gi n d i c a t o r sa r ec a l c u l a t e d :

1) H e a t i n gr a t ef o rz e r ot o t a la n g l eo fa t t a c k ; 2)

Aerodynamic h e a t i n gi n d i c a t o rf o rz e r ot o t a la n g l eo fa t t a c k ;

3)

H e a t i n gi n d i c a t o rf o rn o n z e r oa n g l e s

4)

H e a t i n gi n d i c a t o rf o rl a m i n a rf l o w ;

5)

H e a t i n gi n d i c a t o rf o rt u r b u l e n tf l o w .

of a t t a c k ;

a skin element of area and mass l o c a t e d a t a d i s t a n c e from The temperatureof t h e n o s e of t h e v e h i c l e i s computed f o r Mach numbers g r e a t e r t h a n 1.

Tracking Stations The p r o g r a m c o m p u t e s i n f o r m a t i o n r e l a t i n g t o t r a c k i n g s t a t i o n s l o c a t e d r e f e r e n c ee l l i p s o i d . The t r a c k i n g s t a t i o n l o c a t i o n s a r e s p e c i f i e d i n l a t i t u d e ,l o n g i t u d e ,a n da l t i t u d ea b o v et h ee l l i p s o i d .

on t h e terms of

The s l a n t r a n g e , r a n g e r a t e , and a c c e l e r a t i o n f r o m t h e t r a c k e r t o t h e v e h i c l e is c a l c u l a t e d i n z d d i t i o n t o t h e e l z v a t i o n a n g l e and r a t e , azimuth angle and r a t e , and look angle.

214

Conic Parameters The c o n i c p a r a m e t e r s are c a l c u l a t e d a t t h e end of t h e t r a j e c t o r y o r whenever t h e y are r e q u e s t e db yi n p u t . The f o l l o w i n g c a l c u l a t i o n s p e r t a i n t o b o t h e l l i p t i c and hyperbolic orbits: 1)

E n e r g yp e ru n i t

2)

Eccentricity;

3)

Semimajor a x i s ;

mass;

P e r i g e rea d i u s ;

6)

P e r i g e ev e l o c i t y ;

7)

Angular momentum p e r u n i t

Escapv e elocity;

9)

C i r c u l avr e l o c i t y ;

10)

4) Semilatus rectum;

5)

8)

True anomaly;

1 1O ) r b iitn c l i n a t i o n ; 12)Longitudeoftheascendingnode; 13)

Argument o p f erigee.

mass;

The f o l l o ~ i . n g c o m p u t a t i o n s are a l s o made i f t h e c o n i c Apogee r a d i u s ;

9)

Apogee v e l o c i t y ; Eccentric anomaly;

Mean anomaly ;

is a n e l l i p s e :

Delta V r e q u i r e dt oc i r c u l a r i z e a t perigee;

1 0P) e r i g e p e osition; 1 1 )L a t i t u d e

of p e r i g e e ;

Time t o p e r i g e e ;

Semiminor a x i s ;

Delta V r e q u i r e d t o c i r c u l a r i z e a t apogee;

13)

P e r i g e ea l t i t u d e ;

14)

Apogee a l t i t u d e ;

15)Longitude

at perigee.

I f t h e u n i t is h y p e r b o l i c , the f o l l o w i n g a d d i t i o n a l p a r a m e t e r s 1 )V e l o c i t y 2)

at perigee;

1 2 )R a d i u st ot h es u r f a c e

Period;

are computed:

at infinity;

Time f r o mp e r i g e e .

215

APPENDIX C SPACE TRAJECTORY ERROR ANALYSISPROGRAM (STEAP)

STEM 11 is a series ofthreecomputerprogramsdeveloped by t h e M a r t i n MariettaCorporationforthemathematicalanalysisofthenavigationandguidance o fl u n a ra n di n t e r p l a n e t a r yt r a j e c t o r i e s . The f i r s t series ofprogramsunder this name vas developed under Contract NAS1-8745 for the Langley Research Center and was documented i n two volumes (STEAP User's Manml, STEAP Analytical Mrmuaz) as NASA ContractReport 66818.Under C o n t r a c t NAS5-11795, t h e STEAP series was extensivelymodifiedandexpandedforthe Goddard S p a c eF l i g h t Center. Thissecondg e n e r a t i o n series ofprograms is r e f e r r e d t o ES STEAF 11.

--

STEM I1 i s composed o f t h r e e i n d e p e n d e n t y e t r e l a t e d p r o g r a m s NOMNAL, ERRAN, and SIMUL. A l l t h r e ep r o g r a m sr e q u i r et h ei n t e g r a t i o n of n-body t r a j e c t o r i e sf o rb o t hi n t e r p l a n e t a r ya n dl u n a rm i s s i o n s . The v i r t u a l mass t e c h n i q u e i s t h e scheme u s e d f o r t h i s p u r p o s e i n a l l t h r e e p r o g r a m s , n-body The f i r s t program named NOMNAL is r e s p o n s i b l e f o r t h e g e n e r a t i o n o f nominal t r a j e c t o r i e s ( e i t h e r l u n a r o r i n t e r p l a n e t a r y ) p e r f o r m i n g a number ofdet e r m i n i s t i cg u i d a n c ee v e n t s .T h e s ee v e n t si n c l u d ei n i t i a lo ri n j e c t i o nt a r g e t i n g , m i d c o u r s er e t a r g e t i a g ,a n do r b i ti n s e r t i o n . A v a r i e t y of t a r g e tp a r a m e t e r s are availableforthetargetingevents. The a c t u a l t a r g e t i x g is done i t m a t t v e l p e i t h e r by a modified Newton-Raphson a l g o r i t h m o r b y a scleepest descent-.s,)~jlrgat:a t h e *.,rb.ii:.in.g r a d i e n t s c h e m e .P l a n a ra n dn o n p l a n a rs t r a t e g i e sa r ea v a i l a b l ef o r s e r t i o nc c m p u t a t i o n . A l l maneuvers may b e e x e c u t e d e i t h e r b y a simp!c-? h q J l l l . S t . V e model o r by a pulsing sequence model. ERRAN, thesecondprogramof STEAP I1 is usedtoconduct 3.luea.r ermr analysis s t u d i eas l o n sgp e c i f i tca r g e t e tdr a j e c t o r i e s . t.a:.:ezted t r a j F x t o x y may however b e a l t e r e d d u r i n g f l i g h t b y r e t a r g e t i n g e v e n t s ( c i m p u t c d e j . l : i . . w Ly linear ornonlinearguidance)and by a n o r b i t i n s e r t i o n w e n t . Knocrlsdge and c o n t r o l c o v a r i a n c e s are p r o p a g a t e d a l o n g t h e t r a j e c t o q t h r o u g h a serizs o f measurements andguidanceeventsin a t o t a l l yi n t e g r a t e df e n h i . o n . The h a w l e d g ec o v a r i a n c e is processed through measurements using an optimal Kalman-Schnddi: f i l t e r w i t h a r b i t r a r ys o l v e - f o r f c o n s i d e ra u g m e n t a t i o n .E x e c u i 3 o ne r r o r s a t guidanceevents may b e modeled e i t h e r by an impulsive approximation or by a pulsing sequence model, The r e s u l t i n g knowledgeand c o n t r o l c o v a r i a n c e s may be analyzed by the program a t v a r i o u s e v e n t s t o determine s t a t i s t i c a l d a r a , i n c l u d i n g p r o h a b i l % u t i c midcoursecorrectionsizing and e f f e c t i v e n e s s , p r o b z b i l i t y o f impact, andbiased aimpoint requirements. The t h i r d awl f i n a l program i n t h e STEAP I1 series i s t h e s i m u l a t i o n p r o g r a m SIMJL. SI!liiL is r e s p o n s i b l ef o rt h et e s t i n go ft h em a t h e m a t i c a lm o d e l su s e di n the navigztion and guidance process.

216

APPENDIXD I S O P R O B A B I L I T Y CONTOUR PROGRAM

One method of demonstrating mission accuracy is v i a i s o p r o b a b i l i t y c o n t o u r s . Thesegraphsdepictcertainorbitalparameterdeviationsforvariousprobabilit i e s . I t i s p o s s i b l et op r e d i c tt h eb o u n d a r i e sw i t h i nw h i c he r r o r si nr a d i u s ofperigeeanderrorsinradiusofapogee will f a l l 99.7% of t h e t i m e i f t h e s t a t e c o v a r i a n c e m a t r i x i s kno1.m. a r a d i i - t a n g e n t i a l - n o r m a l (RTN) The H a r t i n M a r i e t t a a p p r o a c h b e g i n s w i t h covariancematrixinposition and velocity (6x6) and a nominal XYZ i n e r t i a l s t a t e v e c t o r (6x1). The RTN c o v a r i a n c em a t r i x i s t r a n s f o r m e dt o i t s XYZ c o u n t e r p a r t v i at h e X Y Z s t a t ev e c t o r . Foreach t r i a l o r b i t , a set o f s i x n o r m a l l y d i s t r i b u t e d random numbers are d r a m from a d i g i t a l randomnumber g e n e r a t o r . T h e s e b a s i c random numbers are u n c o r r e l a t e d w i t h z e r o mean and u n i t v a r i a n c e . P r o p e r s c a l i n g and c o r r e l a t i n g w i t h t h e X Y Z c o v a r i a n c e c o n v e r t s them t o a (6x1)vectorof XYZ p e r t u r b a t i o n s , whereuponthey are added a l g e b r a i c a l l y t o thenominal X Y Z s t a t e v e c t o r t o form a p e r t u r b e d X Y Z s t a t e v e c t o r . Apogee and p e r i g e e r a d i i are t h e n computedfrom thenominalandperturbed XYZ s t a t e v e c t o r s and t h e d i f f e r e n c e s b e t w e e n t h e n o m i n a l a n d p e r t u r b e d r a d i i areformed, The p r o c e s s is r e p e a t e da na r b i t r a r y number of times t oa c c u m u l a t e a s u f f i c i e n t p o p u l a t i o n of p e r t u r b e d r a d i i f o r p l o t t i n g a meaningfulscattergram, theouter'boundaryofwhichformsthe basis f o r a n 0.997 p r o b a b i l i t y c o n t o u r . C o n f i d e n c er e g i o n sa r et h u sc o n t o u r e df o re a c hc a n d i d a t eg u i d a n c es y s t e m ,t h e s m a l l e s t o f which corresponds to the most accurate candidate. The abovemethodhasbeenimplementedon a small IBM 1130 computer with a Cal Comp p l o t t e r and r u n s a t r o u g h l y a 100triallminutecomputing rate.

217

APPENDIX E GUIDANCE STEERING CONCEPTS Thissectionpresents a c r o s s - s e c t i o n s u r v e y of guidance equations used to solve variousmissions.This suLnrey spans a w i d e complexity o f equationsand includes present state-of-the-art algorithms. The g u i d a n c e l o g i c d a t a s h e e t s g i v e i n f o r m a t i o n o n b a s i c g u i d a n c e l o g i c , g u i d a n c er e q u i r e m e n t s ,g u i d a a c ee q u a t i o n s ,a n ds t e e r i n ga n dc u to f fi n tern o ff u n c t i o n a ln o t a t i o n .T h e s ed a t as h e e t s are summarized i n t a b l e 5 1 and det a i l e d in t a b l e s 52 t h r u 60.

are:

The g u i d a n c e l o g i c d a t a s h e e t s a n d a s s o c i a t e d s y s t e m s

1) Minuteman I ;

5)

T i t a n IIIA;

2)

T i t a n 11;

6)

Titan I I I C ;

3)

Polaris;

7)

Saturn;

4)

Pershing;

3)

A t l s ICBM;

9)

Thor ICBM.

The c o n c l u s i o n s t h a t c a n b e d r a x n

from t h e @ d a c e

logicdatasheets

1)ConceptsvaryfromthesimplestQ-guidancetothemost approach) ;

2)

are:

complex ( S a t u r n

Guidanceequationsinclude delta e x p a n s i o n( u pt ot h i r d - o r d e r ) , Qmatrix ( t h e v?ly'!.np,) II aL.d w m i o : ; ~ s x p l . i c l t f o r m u l a t i o n s , Delta and Q are g e n e i d i.;, t.?rw2l+np;ic. A.l.;_ho~!eh S a t u r n has 2 very s o p h i s t l i catedexp?.ici 1 hirnL3tj an P q !.ic-:.L. i q J l e m e n t a t i o n u s i n g a t h i r d orderapprox5mlttng yc'.y.oai a?. is hr?i.ng proposed. This s u g g e s t s t h a t a d e l t a expzmSjGtI of i~*i.~' r i e u t l y h i g h 0rdS-r could pass as an e x p l i c i t

I".

f19

concept.

Q

e1.11011sir:r:e 117

~ ~ ! , . L ' i i ; i t i oi nt is a l i n e a ra p p r o x i n a t i o n ;

3)

The h i g h e s t :;ol-yncw-i.al e x p a n s i o na p p e a r i n gi na n y t h i r d ordcr;

4)

Ste*:r.iag i s gcr:ar-l i 1; ~ ~ ~ ! ~ ~ ~ ~ h( aj t .t i:t u ; di e~ program - ~ c ~ or ~ position i . ~ ~ ~ and vcioci cy erroL' .: 1 '.ti!;) d u r i n g e a r l y s t a g e s , and i n some cases even d u r i n g l a t e r s t 7gr.s; .-c-

5)

of theseconcepts

I

"hebc 5s a d i f f e s e 9 c e i n S p p r o a c ht h a ta p p e a r sb e t w e e ne q u a t i o n sf o r b a l l i s t i c rnlssile a p p : i c a t i o n s arrc? o r b i t a l i n j e c t i o n o r s p a c e m i s s i o n s . -L

In t h eb a l l i s t i ca p p 1 2 c n ~ i o n 9 V

6

i s d e r i v s di t s i n gt h ed e l t ae x p a n s i o n

o r Q-matrix,while i n the s p a c ea p p l i c a t i o n s i n aha: t a l l cs,ses

218

is

_L

V

g

i s d e r i v e de x p l i c i t l y

TABLE 51.- GUIDANCE LOGIC

Guidance equations

Project

SUI*lWARY

Steering equations

Thrust-terninate equations

Guidance requirements

Hinuteman

v

by d e l t a expansion Pitch steering by velocity V component = g pol ynomi a1s (thi rd-order) (second-order) i n a l l stages. Yaw null i n f i r s t and second stages, Vg component yaw steering i n third stage.

o

Rangeand time of f l i g h t

TitanI1

v

Pitch and yaw steering by V component = g velocity and position polynomial (second-order) i n f i r s ts t a g e .P i t c h and yaw steering by V compo9 nentsin second and vernier stages

o

Range and time of f l i g h t

Polaris

v

by delta expansion g(third-order)

by Q-matrix ( l i n e a r timevarying)

Pitch and yaw steering by velocitypolynomials i n f i r s ts t a g e .P i t c h and compoyaw steering by 9 nents i n second stage.

Vg component

=

o

Rangeand time of flight

by Q-matrix (linear)

Pitch and yaw s t e e r i n g by velocity and position e r r o r s i n bothstages.

Vg component

=

o

Range and time of f l i g h t

Pitch and yaw steering by velocity polynomial and nulling in first stage. Pitch and yaw steering using t and e x p l i c i t l y g calculated constants i n second and third stages.

V (nonvectorial) Atti tude,

Pitch and yaw steering by a t t i tude program and nulling i n zero stage. Pitch and yaw steering using t and e x p l i c i t l y 9 calculateconstants i n f i r s t , second, and t h i r d stage.

V (nonvectorial) Atti tude,

Explicit calculus of variationsformulation, with implicit approximatingpolynomial (third-order) implementation

Pitch and yaw steering by a t t i tude programer vel ocity steering in first stage.Pitch and yaw steering by position, velocity,force,time polynomial (third-order).

Use of approxima- Variety of space t i n g polynomial missions w i t h function minimum fuel comsumption

v

Stage I pitch and yawby time programmer and stage I1 vernier constant p i t c ha t t it u d e . component yaw steering.

Pershing

v

TitanIIIA g

V and t (time-to-go) 9

and t

TitanIIIC

Saturn

At1 as ICBM

Thor ICBM

9

(time-to-go)

by d e l t a expansion (second-order)

v9 by Q-matrix

v

-

g = o

velocity,path angleazimuth

9 = 0

V

9

velocity,path anqleazimuth

component = 0

Range and time of f l i g h t

o

Range and time of flight,

vg

Atmospheric phase,timeprogramed a t t i tude. Closed-loopphase,crossproduct steering

V9

component =

219

TABLE 52.- MINUTEMAN I (THREE STAGES) GUIDANCE LOGIC

DATA SHEET

Navigation: Inertial platform Logic: - Velocity and positionsteering Stage I (implicit)

Y (crossrange)

" "

Coordinates

-

Deltawithsteering(implicit) 9 and cutoff Requirements:Totalrange and timeof f l i g h t specified Stage I11

Guidance equations:

i

g

[

T

1

A i A, 2 A, X A, Y A, Z A, xA i ,

AX A Z

1

Ay, A z

A f A, t A, x ,

g[

P 9 [P, Rg] T = 0 a t s t a r t of t h i r d stage on nominal t r a j e c t o r y . 9 presentcondition and nominal condition a t burnout. so

A'S

aredifferences

Steering equations: Stage I Yaw $c [T,

Y]

pitch e,[t, StageI1 Yaw

QCP,Y]

Pitch e

C

= 0,

i,A*,

=

[2, A ,

StageI11 Yaw $c ['g*'/?;. Pitch ec

c

2, A ,

220

= 0.

to' maintain nominal relationship between A , f ;

o 82,

1

X3

same as above;

a t ] same as above; 1 2 , A3

Thrust-terminate equation:

R-

X31

1

same as above.

in

TABLE 53

.- TITAN

11 (TMO STAGES AND VERNIER)GUIDANCELOGIC

DATA SHEET

Navigation: Inertial platform Logic : Stage I - Velocity and p o s i t i o n s t e e r i n g (implicit) Stage I1 and V - Delta w i t h 0 steering 9 ( i m p l i c i t ) and cutoff Requirements:Totalrange and timeof flight s peci f i ed

Y

Coordinates

Guidance equations:

A’S

are differences

i n prestm t condition and nomina 1 condition a t b u r n o u t .

Steering equations: Stage I Yaw qc

E, Y]

= 0,

I -

1

Pitch ec X, Z,

t , 8:z, 21;

StagesI1 and V r

J

Thrust-terminate equation:

t9 = o . 221

TABLE 54.- POLARIS ( T N O SOLID STAGES) GUIDANCLEOGIC

DATA SHEET

Vertical

Davi gati on : Inertial pl atform Logic: Stage I Stage I1

I

-

V2loci.t~steering(implicit) Q-guidancc w i t h steering g ( imp1 ici t) and cutoff Requiremmts:Total range and time of f l i g h t s peci f i ed

(crcssrange) Coordinates hidanceequations:

i s computed continuously, w i t h a special -purp OSk! Yelocity-to-be-gained W 9 IDA, by s o l u t i o n o f theequation -L

Vg

-L

+

. 2

QVg = -aT,

mrith suitableconstraints, where Q i s the(3x3) Q matrix. The elements o f Q are Functions of time,evaluated along the nominal trajectory. By proper orimta.. tion o f the computational coordinate system and trajectory shaping., 3,:1:!y rlre able to perforin each mission by reading i n only t w o elements o f the f)-mI.rix, ,Q , l n d $x a

iteeri ng equati ons : These drive trjo components o f V t o zero sicultaneously w i t h thr*u:;i; termina:ion. 9 Thrust -tcrminate " equati on : " "

"

222

TABLE 55.-

PERSHING (SOLID, TNO STAGES)

GUIDANCE LOGIC DATA SHEET

N a v i g a t i o nI :n e r t i apll a t f o r m Logic:

-

Bothstages

V e l o c i t y and p o s i t i o n s t e e r i n g ( i m p l i c i t ) and Q-matrix with 3 s t e e r i n g and c u t o f f (imp1 i c i t )

Z,5 (crossrange)

Requirements:

g

Total range and time o f f l i g h t specified

Coordinates

Guidance equations:

Vg + Q Vg

A

= -at

Qxy Qxx Q =

Qxz

aVRX aVRX "ax ay

?'RX az

aVRY aVRY aVRY "ax ay

az

QYX

QYY

QYZ

Qzx

Qz,

Qzz

aVRZ

. .

-sg = 5 P ' F

+

ax

aVRZ ay

'E +/(ipi) +

T P

where t h e p - s u b s c r i p t r e f e r s t o

aVRZ az

I

dt]

programmed values.

-

- 3co

T = timp

I,

tco

ri9

= (rip

- :)+

(rip

-

;)dt.

Steering equations: Bothstages Yaw

t]= o

Pitch e c P p

-

:*

Fp- n) dt].

Thrust-terminate equation:

kg =

0.

223

TABLE 56.- TITAN

IIIA (THREE STAGES) GUIDANCE

--

CONCEPT LOGIC SHEET

V

Gx6

N a v i g a t i o n :I n e r t i a pl l a t f o r m Logic:

-

V e l o c i t ys t e e r i n g( i m p l i c i t )

-

E x p l i c i t , based on rocketequation ratherthanKepler's Laws

Requirements:

O r b i ti n j e c t i o n ,b u r n o u ta l t i t u d e , v e l o c i t y , f l i g h t p a t h angle, and azimuth are specified at each aiming point

Stage I Stage I 1 and I11

I

Stage

I

Stages 11 & 111

Coordinates

Guidance equations:

V

9

vg

= Vf

-

V (nonvectorial)

- VL,

where VL i s t h e p r e d i c t e d v e l o c i t y l o s s ( g r a v i t a t i o n a l Time-to-go

t

9

i s obtainedbysolution

v*

=

and aerodynamic)

o f therocketequation m

go I s p

m+mt' g

Steering equations: Stage I Yaw

IJ, =.O.

P i t c h ec [xgf, Zgf] where g f denotes " g r a v i t y - f r e e , v e l o c i t y measurements made by i n t e g r a t i o n o f accelerometer outputs, without gravity corrections. Stages I 1 and I11 Yaw $c = B,

+ B2

t

9 P i t c h ec = AI + A, t

(similartopitch,buta

much simplerproblem).

9'

where AI and A, are a solution to the two-point boundaryvalueproblem of d r i v i n g p r e s e n t v e l o c i t y and radial position to their desired burnout values (aiming point),inthepredicted t g' Thrust-terminationequation: t

!24

9

= 0.

TABLE 57.- TITAN IIIC (FOURSTAGES)GUIDANCE LOGICSHEET

Navigation: Inertial platform Logic:

“.Z

Stage 0

pJv

- Velocitysteering i n yaw and openloop i n pitch

Stages I thru I11

- Explicit,

based on rocketequation rather thanKepler’s laws burnout a1 ti tude, Requirements : Orbit injection velocity, flightpath angle, and at specified are each aiming p o i n t

Stages I , I11 11, azimuth Coordinates

Guidance equations:

V , from a t iteration/integrationprocess. g 9 from an angular momentum i teration/integration process.

%’

AH =

Hd

-

fi(t) d t

Ho =

where Hd i s thedesired, Ho i s thederivativeofangular momentum. The equation for successive predictions of fl(t). is evolved f o r t i n an i t e r a t i v e process g The s t a t e i s integrated (5 points Simpson) to the target points to get the intermediate value of fl( t)

.

Steering equations: Stage 0 Yaw +c = 0. Pitch ec = f ( t ) Stages I t h r u I11 Yaw +, = E,

-k

E,

t (similar to pi ch, b u t a much simplerproblem).

g Pitch ec = A, + A, t

g’

where A, and A, a r e a solution to the two-point boundary value problem of driving present velocity and radial position to their desired burnout values (aimingpoint) i n the predicted t g’ Thrust-terminate equation:

t = 0. 9

225

TABLE 58. - SATURN (THREE STAGES) GUIDANCE LOGIC

x impact Zlunar (crossrange) as Coordinates to

DATA SHEET

Navigation: Inertial platform Logic : Stage I (S-IC) - Time-tilt, minimum-drift program Stages 11, I11 (S-11, S-IVB) - Path-adaptiveguidance mode Requirements: Minimize f l i g h t time (orfuel con sumption) f o r such spacemissions and i n joe rcb- i t tion. Mus t have one-engine-out capability a n d must be adaptable missions a wide of range

IGuidance, s t e e r i n g , and thrust-terminateequations: Stage I Atti tude-time program o r v e l o c i t y s t e e r i n g . Stages 11, I11 Periodically along the trajectory, the two-pointboundaryvalue problem i n the calculus of variations is solved, requiring minimizing the f l i g h t time between the p r e s e n t s t a t e and the desired s t a t e a t mission complenumerition. A steeringfunction and a cutofffunctionaregenerated c a l l y by solving a large number of possible nominal and off-nominal t r a j e c t o r i e s on an IBM 7090. An approximatingpolynomial is used t o i s used, represent the farni lyoftrajectories.Least-squarestechnique Polynomials t h a t have been evaluated and shown to give good r e s u l t s f o r low-orbit inject missions contained terms as h i g h a s t h i r d order:

226

TABLE 59.- ATLAS ICBI-I

(mo STAGESAND

el 5i30g

\d"S

VERNIER) GUIDANCE LOGICDATA SHEET

Navigation:Inertialplatform (Arma) Logic: Stage I - Programmed a t t i t u d e Stage I1 - Delta w i t h 0 steering(implicit) Vernier - Same 9 Requirements: Totalrange and time-of-flight specified

Coordinatesystem ( i n e r t i a l , launchpoint-oriented) Guidance equations:

vgx vgy A'S

=

kx,

AY, A z , A t ,

'I

A i , AZ , asecond-degree

polynomial

= Ai.

are differences between presentvalues and nomial values a t VECO.

Steering equations: Stage I Yaw

I ) ~=

0

Pitch e = f ( t ) - timeprogramer. C

Stage I1 Pitch ec = constant Vernier Yaw where gain

I)C

%

= $nom

+

K1(Vgy

- K2 Vgx)

is chosen t o make K V 2

gx

= V

gY

a ti n i t i a t i o n ofguidance.

Thrust-terminate equation: Stage I1 Vgx = A smallvaluecompatible

w i t h vernier capability,

Vernier

vgx

= 0.

227

TABLE 60.- MOR ICBM

(ONE STAGE AND VERNIER) GUIDANCE LOGIC

DATA SHEET

Navigation:Inertialplatform(Delco) Atmosphericphase - Programmed a t t i t u d e Closed-loopphase - Q-guidance and vernier Requirements: Tota,l range and time-of-flight specified

Coordinates

Guidance equations : -t

V

9

obtainedas

a solution t o theequation

;/hereelementsoftheQ-matrixareevaluatedasfunctions o f timealongthe inaltrajectory, and approximated by constants i n actual use. Steering equations: Atmosphericphase Yaw $c = 0 Pitch ec = f ( t )

-

time programmer,

Closed-loop phase (thru vernier) Yaw = K ( O ~vgZ ~ - Vgz vgX)

JI,

Pitch ec = K 9

(

gx

V

SY

- 0gY

V

gx

1

cross-product steering

Thrust-terminateequations:

228

SECO

-

A

VECO

-

A

V

V

9

9

= A smallvaluecompatible =

0.

w i t h verniercapabil i t i e s ,

nom-

TheScoutvehicleand i t s guidancesoftwareconsiderationsshouldbeanalyzed i n d e v e l o p i n g a s e t of g u i d a n c ea l g o r i t h m s . A S c o u t - o r i e n t e dd e s i g np h a s es h o u l d considerexistinglogicwhilesolvingtheScout-peculiarproblems.

229

APPET\!DIX

r-

Central i zed Executive System The mboard. computer operates i n a complexenvironmentsupporting a number a n r l ,rarir?ty ~1 f~.mc.tions. Thecomplex p r o b l e u sa c s c c i a t e dw i t h tlle computer's dpc.cai3.vualm:&orment, z . c h as s c h e d u l i n g t h e n e x t p r o g r a m f o r e x e c u t i o n , l o a d h g i-he prog:Lsm, 2nd i l l i t i a t i n g machine cmpmenix must Le h a n d l e d i n a n e f f i c i enf mxu1e~~111*~ onboardexecutive sysLern p r o v i d e so v e r a l ls u p e r v i s i o na n do p e r a tiortrl. c o n t r o l (12 the computational r e s o u r c e s a v a i l a b l e , The e x e c u t i v e s y s tern funcr.i.ons dur:'Lng 1 7 ndseion phases t o c o n t m l t h e e x e c u t i o n of a p p l i c a t i o np r o g r a m as cequired,,Representative computer f c n c t i o n s are:

1) N a v i g a t i o r ;

4 ) staging; Separatior! and

2)

Guidm

5)

Attitude csntrol;

3)

Fcloi gnht rLo l ;

6)

Telemetry ;

7)

V e h i c l es t a t u sa n ds e q u e n c i n g .

;

The e n v i r o n m e n t i n v o l v e s f i v e b a s k t y p s n

ofprogramming:

1) M a t h e m a t iccaallc u l a t i o n s ;

3)

Decision making;

2)

4)

ljata m a n i p u l a t i o n ;

5)

Program c o n t r o l .

Message f o r m u l a t i n g ;

The b a s i c p e r f o r m m c e r e q u i r e m e n t s

of t h e e x e c u t i v e s y s t e m

are t o :

1) C e n t z s a l i z ef u n c t i o n st h a tc o n t r o lf l o w o f informationbetweenthe programs and t h e ?starnzl environment; 2)

Manage t h er e s o u r c e so ft h es y s t e mt oo b t a i ne f f i c i e n tu s eo ft h e harclwa-2 and tr? a n s u r e t h e r e s p o n s e r e q u i r e d by t h e a p p l i c a t i o n , and p r o v i d e a s t a n d a r 3 i z e d i n t e r n a l e n v i r o n m e n t t h a t will p e r m i t programs ilo be C C I W L L ~ ~ J Cand ~ ~ ~executed I independently of one another;

5) Each f u n c t i o n is b r i e f l y 3t2SCi-iici

230

j,:

E n v i r o n m e n t ailn t e r f a c e .

t h c 5ollc:aingsEbsections.

.-

ProgramControl The f u n c t i o n o f p r o g r a m c o n t r o l is t o g o v e r n t h e i n i t i a tion,execution,andterminationofscheduledprograms. The m a s t e rc y c l e cont r o l st h eo v e r a l lc y c l eo fp r o g r a m si na c c o r d a n c ew i t ht h es c h e d u l i n ga l g o r i t h m employed. R.70 o p t i o n s may b ep r o v i d e d : 1) The b a s i c c y c l e f u n c t i o n i s r e q u i r e dw i t h a s c h e d u l i n gc a p a b i l i t y a place toprovide a pointofreturnfortheschedulingcycle,and i s no u s e f u l work t o b e d o n e ; to idle if there 2)

With c y c l i c c o n t r o l a limit i s p l a c e d on t h e time a program may exec u t e i n a givenperiod, s o thatthemastercyclefunctionmustbeenl a r g e d t o h a n d l e a program switch.

The b a s i c i n i t i a t i o n / t e r m i n a t i o n p r o c e s s e s r e q u e s t s f o r i n i t i a t i o n a n d A b a s i cs c h e d u l e rp r o v i d e st h es i m p l t e r m i n a t i o no fp r o g r a m sr e s i d e n ti nc o r e . e s t class o f s c h e d u l i n g s e r v i c e , i n w h i c h s e l e c t i o n of t h e n e x t p r o g r a m t o rec e i v e CPU time i s based on a s i n g l e s e r v i c e p r i o r i t y . A m u l t i p l e x i n gs c h e d u l e r i n t e r l e a v e st h ee x e c u t i o no fp r o g r a m s ,t h u sp e r m i t t i n gc o n c u r r e n te x e c u t i o no f a number of programs. Two o p t i o n s may beprovided: 1)

Time c o n t r o lp e r m i t st h ee x e c u t i v et or e g a i n CPU c o n t r o l a t s p e c i f i e d by i n t e r v a l s , e i t h e r as t h e r e s u l t o f v o l u n t a r y r e t u r n o f c o n t r o l o r a st h er e s u l t scheduledprograms a t i n t e r v a l s i n t h e i r e x e c u t i o n , of a p r e s e tc l o c ki n t e r r u p t . The l a t t e rd e v i c ep r e v e n t st h e monopoly of CPU time by a s i n g l e p r o g r a m ;

2)

A d d i t i o n a l service classes p r o v i d et h e means o fa s s i g n i n g CPU time a c c o r d i n g t o a number o f p r i o r i t i e s t o r e s o l v e c o n f l i c t s among competingprocessingrequirements.

Interrupt Supervision.- The f u n c t i o n o f i n t e r r u p t s u p e r v i s i o n is todir e c t s y s t e ma c t i o n a t t h eo c c u r r e n c eo fa na s y n c h r o n o u si n t e r r u p t . The b a s i c purpose i s t o p r o v i d e c o h e r e n t s y s t e m r e s p o n s e t o e x t e r n a l s t i m u l i by i s o l a t i n g theoperationoftheprogramsrespondingtotheinterruptsfromtheoperation of scheduledprograms. The f u n c t i o n sa v a i l a b l e are d e s c r i b e d : Primaryroutinessupplythecodetoperforminitialprocessingof a l l i n t e r r u p t s .T h e s er o u t i n e sa l s op r o v i d et r a n s f e ro fc o n t r o lt o routines performing any additional interrupt processing that might be required; A savemechanism i s r e q u i r e d t o s a v e and r e s t o r e machine conditions, and t or e t u r nc o n t r o lp r o p e r l yt ot h ei n t e r r u p t e dp r o g r a m s .F i x e d areas f o r s t o r a g e a r e r e q u i r e d ; R e e n t r a n c ec o n t r o lp e r m i t s a s e r i a l l y r e u s a b l e codeaccessedbyinterruptroutinestobeoperatedwithminimaldisablingofinterrupts. T h i se n s u r e st h a tt h es y s t e mr e s p o n s er e q u i r e m e n t sc a nb e met i f at a l l possible.

23 1

I/o SUperViSi0n.- The f u n c t i o n of 110 s u p e r v i s i o n i s t o p r o v i d e a l l serv i c e sa s s o c i a t e dw i t ht h eu s eo f 110 devices.Thepurpose of c e n t r a l i z i n g serv i c e s i s n o tm e r e l yt oa v o i dc o d ed u p l i c a t i o n ; i t i s n e c e s s a r yt oa c h i e v ec o r r e c t usageof 110 d e v i c e si nt h ep r e s e n c eo fc o n c u r r e n ti n d e p e n d e n tr e q u e s t s .T h e 1/0 requestprocessorprovidesdevice-independentservices -- b a s i c a l l y q u e u e i n g req u e s t s , i n i t i a t i n g 110 t r a n s m i s s i o n ,a n dm o n i t o r i n gt h ep r o g r e s so fo p e r a t i o n sb y analyzingcompletionconditions.Programexecution i s t h u sc o o r d i n a t e dw i t h 110 e x e c u t i o n and o p t i m a l u s e o f CPU time i s a c h i e v e d w h i l e 110 r e q u e s t s are b e i n g serviced;

System services.- System services p r o v i d e a number o f f u n c t i o n s u s e d i n common by a p p l i c a t i o np r o g r a m sa n de x e c u t i v er o u t i n e s .T h ef o l l o w i n g are two m a j o rf u n c t i o n s : 1)

2)

Timing s e r v i c e sa r er e q u i r e dt os y n c h r o n i z et h eo p e r a t i o no fp r o g r a m s w i t h r e a l time, a)

The b a s i ct i m i n gs e r v i c ep r o v i d e s a programmed real-time c l o c k f o r u s e by anyprogramsand, ifcycliccontrol i s implemented, a routinetocontrolaction 57hen t h e time i n t e r v a l e x p i r e s ,

b)

A timingqueueprovides

a means f o r u s i n g t h e s i n g l e h a r d w a r e i n t e r v a l timer f o r m u l t i p l e - p u r p o s e e v e n t i n i t i a t i o n b a s e d on time ofday;

Message h a n d l e rs e r v i c e sp r o v i d ef o rc o m m u n i c a t i o nb e t w e e nt h e comp u t e r and human s o u r c e s of c o n t r o l . A b a s i cm e s s a g eh a n d l e r i s req u i r e d s o programsandexecutiveroutines Icay i n i t i a t e 1 / 0 o p e r a t i o n s t o t r a n s m i t and receivemessages.

.-

Environmental interface The f u n c t i o n of t h e e n v i r o n m e n t a l i n t e r f a c e i s toprovidefororderlyinitiationandtermination of thesystem,forInonLtoring i t s o p e r a t i o n s ,a n df o rr e c o v e r i n gf r o mc o n t i n g e n c i e si n s o f a r as !-s poss?.ble. Tablesprovideresidenceforsystemparametersandstatusinfomaation, b o t h as a meansof avoidingredundantincorporationofthesedatainindividualroutines and as a msans o fp r o v i d i n gc e n t r a l i z e d access t ok e yi n f o r m a t i o n .C e n t r a l i z a t i o n of e r r o r d e t e c t i o n / r e c o v e r y p e r m i t s a prescribedresponsetosystemand h a r d w a r ee r r o rc o n d i t i o n s commonly e n c o u n t e r e d b y e x e c u t i v e r o u t i n e s a n d a p p l i c a t i o np r o g r a m s .S t a t u sm o n i t o r i n g i s a c h i e v e db yt h ec o l l e c t i o n ,a n do u t p u t on and g e n e r a l demand, of s t a t i s t i c s c o n c e r n i n g t h e e x e c u t i o n o f i n d i v i d u a l p r o g r a m s a s p e c t s of s y s t e mo p e r a t i o n . Its purpose i s t op r o v i d et h ed u a lc a p a b i l i t y of detectingundesirableaspectsofsystemoperationduringsimulation,and of monitoringactualperformance. Use Of executives .- To a s s u r e e f f i c i e n t u s e o f s y s c e m r e s o u r c e s , a n e x e c u t i v e s y s t e ms h o u l db et a i l o r e dt ot h em i s s i o n .T h et a i l o r i n go fe x e c u t i v e sf o re a c h i s a d o p t e d .S p e c i f i cr e q u i r e mission i s s i m p l i f i e d i f a modulardesignapproach ments canbe met by s e l e c t i n g f u n c t i o n a l s u b s e t s f r o m a generalexecutivedesign.

2 32

Scoute%eCutiVefunctions.To determine t h e a p p l i c a b i l i t y of a n e x e c u t i v e system on a S c o u t m i s s i o n , a n a n a l y s i s was made o f t h e t y p i c a l c o m p u t e r p r o g r a m s r e q u i r e d ,w i t he m p h a s i s on p r o g r a mc o n t r o lf u n c t i o n s .T h i sa n a l y s i si n c l u d e d an e v a l u a t i o n of f u n c t i o n a l r e q u i r e m e n t s a n d i d e n t i f i c a t i o n o f p e r f o r m a n c e anddeA t y p i c a ld e s i g nf o r a S c o u te x e c u t i v es y s t e m was e s t a b l i s h e d s i g nr e q u i r e m e n t s . by s e l e c t i n g s p e c i f i c f u n c t i o n s f r o m t h e g e n e r a l f u n c t i o n a l d e s i g n j u s t o u t l i n e d and is l i s t e d : Program control, a)Mastercycle b)

-

b a s i c and c y c l i cc o n t r o l ,

Basic i n i t i a t e / t e r m i n a t e ,

cB) a s iscc h e d u l e r ; I n t e r r u p ts u p e r v i s i o n , a) Primary routines, b)

Save mechanism,

fi.xed a r e a s ;

I/O s u p e r v i s i o n , i n c l u d i n g support;

110 r e q u e s tp r o c e s s o ra n do n b o a r dd e v i c e

S y s t e ms e r v i c e s ,i n c l u d i n gt i m i n gs e r v i c e s ; Environmental interface

,

Taa) b l e s , bE ) r r od r e t e c t i o nr e c o v e r y , cS) t a t um s onitoring. will b e i n t e r r u p t e d p r o v i d e d t h e i n t e r r u p t f u n c Thenormalprogramsequence t i o n is notbeinglockedout.The real-time i n t e r r u p t and t h e e x t e r n a l i n t e r r u p t needto b e p r o v i d e d f o r i n t h e e x e c u t i v e s y s t e m d e s i g n . a genThe i n p u t / o u t p u t s e c t i o n of t h e g u i d a n c e c o m p u t e r w o u l d b e b a s i c a l l y e r a l - p u r p o s ei n t e r f a c ep r o v i d i n gt h ec o m m u n i c a t i o np a t h sb e t w e e nt h ec o m p u t e ra n d t h e controlsystem.Althoughthe 110 system will i n p u ta n do u t p u t a v a r i e t y of d a t at y p e s ,t h em a j o r i t yo fd a t a is one word ( 2 4 b i t s ) o r less i n l e n g t h . T h i s c h a r a c t e r i s t i c and t h e r e l a t e d a d d r e s s i n g c h a r a c t e r i s t i c s d i c t a t e a 1 0 1 - 7 l e v e l of c a p a b i l i t y i n t h ee x e c u t i v ef o r I/O c o n t r o l .

233

I n a complex computer program with distributed control, a simplechange t o onesegmentoftheprogram may i n v o l v e a m a j o r r e c o d i n g e f f o r t . T h e c e n t r a l i z e d e x e c u t i v e p r o v i d e s a means f o r m i n i m i z i n g t h e c o s t of changes by localizing changes t o i n t e r a c t i o n s w i t h t h e e x e c u t i v e . T h e i n i t i a l c o d i n g e f f o r t may a l s o b er e d u c e dw i t h a c e n t r a l i z e d e x e c u t i v e by allowing the application programs to bepreparedinmodular form w i t h a s t a n d a r d i n t e r f a c e w i t h e x e c u t i v e . S c h e d u l i n g andtimingrequirementsfor a l l moduleswouidbesatisfiedinconjunction withthefinaldesignoftheexecutiveprograms. Theprimaryobjectionraisedintheuseofcentralizedexecutivesinspace a p p l i c a t i o n sg e n e r a l l yc o n c e r n st h e amount of memory andexecution time r e q u i r e d t os u p p o r tt h ee x e c u t i v ef u n c t i o n s . Memory i s r e q u i r e dt oc o n t a i nt h ee x e c u t i v e f u n c t i o n s . However, t h e o v e r a l l s y s t e l n s i z e may b er e d u c e db ye l i m i n a t i n g red u n d a n tc o d ef o re x e c u t i v ef u n c t i o n sa n d comnon s u b r o u t i n e s d i s t r i b u t e d t h r o u g h outtheapplicationprograms. A centralizedexecutivesystemalsolendsitselftooptimizationofdata p r o c e s s i n g f u n c t i o n s s o t h e computerdutycyclecanbeminimized. on program control and i n t e r r u p t s u p e r v i s i o n Thedesigneffortconcentrated €oranexecutivesystem.Prograincontrol i s d e s c r i b e di nt h ef o l l o w i n gs u b s e c t i o n and i n t e r r u p t h a n d l i n g i n t h e n e x t s u b s e c t i o n .

.-

Program Control All programs i n t h e s y s t e m , w h e t h e r p a r t t i v e o rw r i t t e nf o ra na p p l i c a t i o n ,o b t a i nc e n t r a lp r o c e s s i n gu n i t oneof two ways:

of t h e execu(CPU) time i n

i s i n i t i a t e d by t h eo c c u r r e n c e o f anevent and r e c e i v e s c o n t r o l d i r e c t l y f r o m a n i n t e r r u p t o r d u r i n g t h e c o u r s e o fi n t e r r u p tp r o c e s s i n g . I t s f u n c t i o n i s t od e f i n et h es y s t e m ' s responsetotheevent;

1)

A n unscheduledprogram

2)

A s c h e d u l e dp r o g r a mr e c e i v e sc o n t r o lu n d e rs p e c i f i e dc o n d i t i o n sa s a r e s u l t of s e l e c t i o n by t h e p r o g r a m c o n t r o l r o u t i n e s of t h e e x e c u t i v e s y stem.

When a ni n t e r r u p to c c u r s i t is f i e l d e d , i d e n t i f i e d , q u e u e d , and a r e t u r n made t ot h ep r o g z a mc u r r c n z l yb e i n ge x e c u t e d .C o n t r o l i s p a s s e dt ot h ep r o p e r p r o g r a mu n i tt op r o c e s st h ei a t r ? r r u p t on a t i m e - a v a i l a b l eb a s i s .T h e s ep r o g r a m u n i t s are calledunscheduledunits.Unscheduledprogramsdefinesystemresponse t o asynchronousevents,whilescheduledprogramsimplementprocessesthatare synchronouswithintheapplicationrequirements. I n t e r r u p t s are u s u a l l y e n a b l e d d u r i n g e x e c u t i o n o f anyprogramtoallow o p t i m a ls y s t e mr e s p o n s et o real-time r e q u i r e m e n t s .T h i s may l e a d t o a n i n t e r r u p t s t a c k of predetermineddepth.Thestack i s p r o c e s s e di n l a s t i n - f i r s t o u t (LIFO) order until the original interrupt processing i s complete. Eachprogram r o u t i n s i-s s t r u c t u r e d s o i t s e x e c u t i o n t i m e doesnotexceed a s p e c i f i e d t i m e i n t e r v a l . CPU r s q u i r e m e n t sa r ee x p r e s s e di n terms of a r e p e t i t i o n rate t h a t d e s c r i b e s t h e nuinber ofprogram u n i t s p e r s e c o n d r e q u i r e d f o r processing.

ThealgorithmanalyzedforScoutmissions i s of t h e " p r e a s s i g n e d iterativecycle"system-typeinwhichrequirements are determined i n advanceofthe m i s s i o na n dt h es y s t e ms t r u c t u r e is t a i l o r e d t o t h e s p e c i f i c m i s s i o n . It i s thereforenecessarythattheexecutiveallocate CPU time t o o p e r a t i n g a p p l i c a missile system.Thescheduler t i o n programsbased on c y c l er e q u i r e m e n t so ft h e p o r t i o n of t h e e x e c u t i v e vi11 g u a r a n t e e t h a t e a c h p r o g r a m u n i t will b e e x e c u t e d w i t h i nt h et i m er e q u i r e m e n t ss p e c i f i e db yt h es y s t e md e s i g n e r . A typicalstructureforspaceborneflightprogramscontrolconsistsof a m a j o rc y c l ed e s i g n e dt oh a n d l et h eg u i d a n c ea n dn a v i g a t i o nf u n c t i o n sa n d a minor c y c l ec o n c e r n e dw i t hv e h i c l ec o n t r o la n ds t a b i l i t y .O t h e rc o m p u t a t i o n a lc y c l e s o fi n t e r e s ta r et h o s ec o n c e r n e dw i t ht e l e m e t r yp r o c e s s i n g ,w h i c hu s u a l l yo c c u r s a t a f r e q u e n c ys i m i l a r t o t h a t of t h em i n o rc y c l e . Also t y p i c a l l y , t h e s p a c e at t h e same frebornecomputersinput and o u t p u tp r o c e s s i n gp r o g r a m so p e r a t e quency as theminorcycle.

The minor cycle processing is accomplished a t a h i g h f r e q u e n c y c o n s i s t e n t w i t ht h ef r e q u e n c yo ft h er e a l - t i m ei n t e r r u p t sa n dv e h i c l es t a b i l i t y .T h em a j o r c y c l e i s performed on a l o w - f r e q u e n c y b a s i s , u s u a l l y b e i n g e x e c u t e d o n c e f o r e v e r y 10 t o 50 minorcycles.Themajorcyclecalculations are g e n e r a l l y computed on a t i m e - a v a i l a b l eb a s i s .T h a t is, theminorcyclecomputationalrequirements are satisfied first, with any time r e m a i n i n g u n t i l t h e n e x t e x e c u t i o n o f t h e m i n o r cyclebeingusedforcomputationofmajorcycleprogramelements.Inthegeneral time a l l o c a t e d f o r o n e c o m p l e t e case,computation will becompletedbeforethe c y c l e .T h e r e f o r e ,t h en e x tl e v e lo fc o m p u t a t i o n s will beexecuted.These may b e e i t h e r s e l f - t e s t programs o r a dummy program t o c a u s e t h e CPU t o i d l e . To i l l u s t r a t e , assume t h a t t h e r e are f i v e m i n o r c y c l e s f o r e a c h m a j o r a t f i x e d i n t e r v a l s are n o t Thenumber o fr e a l - t i m ei n t e r r u p t st h a to c c u r shown b u ta r e assumed.Forexample, f i v e real-time i n t e r r u p tc y c l e s may o c c u r duringeachminorcycle. I t h a sa l s ob e e na s s u m e dt h a tb o t ht h em a j o ra n dm i n o r cycle computations will b e c o m p l e t e d p r i o r t o t h e e n d o f t h e r e s p e c t i v e c y c l e , cycle.

The program control functions govern the scheduling and operation of program u n i t sw i t h i nt h es p a c e b o r n ec o m p u t e r .P r o g r a mc o n t r o l vi11 c o m p r i s e t h e f o l l o w i n go p e r a t i o n s : 1 )I n i t i a t i o no fp r o g r a mu n i t s ; 2)

Scheduling of p r o g r a mu n i t sl e a d i n gt ot h ea c t u a lt r a n s f e r to the program unit selected to receive CPU time;

3)

Termination of programunits.

of c o n t r o l

Scheduledprograms are o r g a n i z e d i n t o a s e t o f i n t e r r e l a t e d c o m p u t a t i o n a l time requirementsandsequencing relac y c l el o o p st h a tr e f l e c tt h ep r o c e s s i n g t i o n s h i p so ft h ep r o g r a m s . The computation time a l l o c a t e dt oe a c hl o o p is termed t h eb a s i cc y c l et i m e . E a c hp r o g r a mh a sa na s s o c i a t e di n t e g e r ,n ,t h a ti n d i c a t e s thefrequencyofloopexecutionandcanalsobethoughtofasrepresentingthe r e l a t i v e p r i o r i t y of programs i n t h a t l o o p w i t h r e s p e c t t o p r o g r a m s i n o t h e r l o o p s .

235

T h ei n t r o d u c t i o no ff r e q u e n c ya n dp r i o r i t yo c c u r sa s a n a t u r a lc o n s e quenceof t h ep r o g r a ms e l e c t i o na l g o r i t h m . A t t h e s t a r t of a b a s i c c y c l e , t h e f i r s t program i nt h eh i g h e s tf r e q u e n c yl o o p is g i v e n CPU time. When t h a t program c o m p l e t e se x e c u t i o n ,t h en e x tp r o g r a mi nt h el o o p i s s e l e c t e d .T h i sp r o c e s s continuesuntiltheloopprogram l i s t i s e x h a u s t e d . When t h a t o c c u r s , and when t h e b a s i c c y c l e time h a s n o t e x p i r e d , t h e n e x t h i g h e s t f r e q u e n c y l o o p is e n t e r e d . The program selected is e i t h e r t h e f i r s t one t h a t h a s n o t y e t r e c e i v e d CPU time forthiscomputationcycleoftheloop,ortheone whoseexecution was suspended b e c a u s e of e x p i r a t i o no f a b a s i c c y c l e t i m e . E n t r y t o a l o o po fg i v e nf r e q u e n c y is n o t made u n t i l t h e CPU r e q u i r e m e n t s f o r a l l h i g h e r f r e q u e n c y l o o p s a r e satisf ied.

i s t o d i s t r i b u t e CPU time toprograms i n The e f f e c t o f t h i s a l g o r i t h m p r o p o r t i o nt ot h e i rc o m p u t a t i o n a lr e q u i r e m e n t s ,w i t h o u tr e q u i r i n gi n d i v i d u a lp r o grams t o b e c o g n i z a n t o f t h e r e q u i r e m e n t s o f otherprograms,scheduledorunscheduled. A t completion of the major cycle computation during a c o m p u t a t i o n a lc y c l e It maybe d e s i r a b l e t o start t h e m a j o r c y c l e o v e r o r s t a r t anotherprogram,such as a d i a g n o s t i co rs y s t e m - i d l ep r o g r a m . A t theendofthecomputationcycle,the system may e i t h e r i g n o r e programs with suspended execution or complete them i n t h e next available slack period.

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

master c y c l e s u p e r v i s o r

canbesummarized

as : 1)

R e t u r ns e q u e n c e sa r er e s p o n s i b l ef o ru p d a t i n gt h es t a t u s gram p r e v i o u s l y i n e x e c u t i o n ;

of t h e p r o -

Thecontinuesubroutine is alwaysexecuted on r e e n t r y t o t h e m a s t e r c y c l e . I t s f u n c t i o n i s t o a l e r t t h es y s t e mt oc o m p u t a t i o nc y c l e o v e r l o a d s( i ft h e yo c c u r )a n dt oi n i t i a t et h es e l e c t i o n of t h e n e x t program. I t a l s os e r v e s as a c o n t r o l p o i n t t o i d l e i f t h e r e i s no program t o e x e c u t e ;

236

3)

The select l e v e l s u b r o u t i n e i s r e s p o n s i b l e f o r t h e p r o c e s s e s n e c e s s a r y t o i n i t i a t e and tocomplete a computationcycleloop, and f o r theselectionoftheloopfromwhichthecurrentprogramshould be chosen;

4)

The s e l e c t program subroutine s e l e c t s a programandexamines its s t a t u sf l a g st od e t e r m i n ew h e t h e r i t s h o u l db ee x e c u t e d .S e l e c t i o n andexaminationcontinuesuntileither a program is chosen o r i t i s d e t e r m i n e d t h a t a new computation cycle loop should be entered;

5)

The d i s p a t c h e r sets up e n t r y c o n d i t i o n s f o r t h e s e l e c t e d p r o g r a m t u r n s CPU c o n t r o l o v e r t o it.

and

Program schedule.- Programscheduling i s t h e s e t offunctionsemployed i n s e l e c t i n g a program t o r e c e i v e CPU time. There are two d i s t i n c t activities: 1 )A c t i v a t i o no fp r o g r a m sr e a d yf o re x e c u t i o n ;

2)

S e l e c t i o n of a p a r t i c u l a rp r o g r a mt o

receive CPU time.

The normal action engendered by this scheduling algorithm i s t o execute a l l programs i n t h e h i g h e s t p r i o r i t y c o m p u t a t i o n c y c l e f i r s t . I f t i m e remains b e f o r et h en e x tc y c l e i s t o s t a r t , t h en e x tl o v e r level i s begun.Thisprocess c o n t i n u e s u n t i l a l l levels are e x h a u s t e d a n d t h e s c h e d u l e d p r o g r a m l o o p i d l e s , oruntiltheexpirationof a b a s i c time c y c l e , w h i c h f o r c e s restart a g a i n a t t h e h i g h e s tl e v e l .I np a s s i n gf r o mo n el e v e lt ot h en e x t , if t h e new l e v e l hasbeen previously completed, i t will n o t b e r e s t a r t e d u n t i l t h e b a s i c c y c l e c o u n t r e a c h e s t h e r e s t a r t v a l u e .F u r t h e r m o r e , a g i v e n l e v e l will n o t b e r e a c h e d u n t i l all h i g h e rl e v e l sh a v ec o m p l e t e dt h e i rc u r r e n tc o m p u t a t i o nc y c l e .

I n t e r r u p t SlJperViSi0n.- The i n t e r r u p t s u p e r v i s o r is d e s i g n e d t o p r o v i d e a coherentsystemresponsetoasynchronousinterruptsbyisolatingtheoperations of p r o g r a m s r e s p o n d i n g t o t h e i n t e r r u p t f r o m t h e o p e r a t i o n o f s c h e d u l e d p r o g r a m s . is e n t e r e d u n d e r u n p r e d i c t a b l e c o n d i t i o n s . The primary interrupt routine To a l l o w t h i s r o u t i n e t o e x e c u t e f r e e l y w i t h o u t s a c r i f i c i n g m i n i m a l d e l a y i n res p o n s eu n d e rn o r m a lc i r c u m s t a n c e s ,t h ei n t e r r u p tc o n t r o lm e c h a n i s ms h o u l d :

1) Minimize t h e time r e q u i r e dt os a v ea n dr e s t o r em a c h i n ec o n d i t i o n s ; l i t t l e as p o s s i b l e ;

2)

Run d i s a b l e da s

3)

P e r m i t m u l t i p l el e v e l so fs t a c k e di n t e r r u p t s ;

4)

P r o v i d er o u t i n e sw i t h they may modify.

a way o f r e s t o r i n g a n y i n t e r r u p t c o n d i t i o n s

Thefollowingfunctionsarerequiredto

meet t h e s e r e q u i r e m e n t s :

1)

A methodofsavingandrestoringmachineconditions;

2)

A m e t h o do fp r o c e s s i n gi n t e r r u p tc o d ea p p r o p r i a t et ot h ei n t e r r u p t typeinbothprimary-andsecondary-levelroutines;

3)

A m e t h o do fc o n t r o l l i n gm u l t i p l e

access t o i n t e r r u p t r o u t i n e s .

T h ep r i m a r yi n t e r r u p t so f interest to the executive system are t h e realtime i n t e r r u p t and t h e e x t e r n a l i n t e r r u p t . O t h e r i n t e r r u p t s a v a i l a b l e o n l y req u i r e a minimum amount o f s e r v i c i n g , p r i m a r i l y t o e n a b l e and d i s a b l e t h e i n t e r r u p t s .P r o g r a ms t a t u s will b e s t o r e d i n a s a v e area on i n t e r r u p t i o n .S a v e areas will be chained to form a last in-first out queue. D u r i n ga ni n t e r r u p t ,m a c h i n ec o n d i t i o n s are s a v e d i n , and r e s t o r e d from, an a r e a c a l l e d a n i n t e r r u p t s a v e area. The i n t e r r u p t s a v e area c o n t a i n s t h e contents of any registers or scratchpad memory a d d r e s s e s t h a t will be used i n t h e i n t e r r u p tr o u t i n e andwhose c o n t e n t sm u s tb es a v e d .I na d d i t i o n ,l i n k a g e st o are s u p p l i e d . boththenexthigherandlowerinterruptlevels

CR-2029

- 21

237