AERO-ASTRODYNAMICS CONS IDERATIONS FOR - · PDF filea nasa technical memorandum n.g4 tm x-...

A NASA TECHNICAL MEMORANDUM

N . G 4 TM X- 53500

A w l s t 8, 1966

A E R O - A S T R O D Y N A M I C S C O N S I D E R A T I O N S F O R T H E A P O L L O T E L E S C O P E M C U N T By Robert E. Lavender

Aero-Astrodynamics Laboratory

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TECHNICAL MEMORANDUM X-53500

AERO-ASTRODYNAMICS CONSIDERATIONS FOR THE APOLLO TELESCOPE MOUNT

BY

Robert E. Lavender 4

George C. Marshall Space F l i g h t Center

Huntsv i l le , Alabama h

27p1 -. F, ABSTRACT ,; - d

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This r e p o r t p resents the r e s u l t s of prel iminary ana lyses which have been conducted by the Aero-Astrodynamics Laboratory r e l a t i v e t o the Apol lo Telescope Mount (A'IM). The ATM is an experimental package cons i s t ing of a group of sensors i n the v i s u a l , u l t r a v i o l e t (UV), extreme u l t r a v i o l e t (XUV), and X-ray s p e c t r a l regions , and the neces- s a r y experimental support equipment t o o b t a i n s c i e n t i f i c d a t a by solar observa t ions from e a r t h o r b i t . The ATM package is considered t o be hard-mounted t o the Lunar Module (IN). Mission a n a l y s i s , o r b i t a l aerodynamics, aerodynamic torque, o r b i t a l l i f e t i m e , dynamics and con t ro l are discussed. Prel iminary mission t imel ines are included.

NASA - GEORGE C. MARSHALL SPACE FLIGHT CENTER

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NASA - GEORGE C. MARSHALL SPACE F L I G H T CENTER

Technical M e m o r a n d u m X-53500

August 8, 1966


BY

R o b e r t E . Lavender

TECHNICAL AND S C I E N T I F I C STAFF AERO-ASTRODYNAMICS LABORATORY

ACKNOWLEDGEMENTS

This r epor t has been prepared wi th the s u b s t a n t i a l ass is tance of var ious colleagues from the Aero-Astrodynamics Laboratory. The most notable include T e r r e l l Deaton, Doris Chandler, Thomas T e l f e r , Joe Cremin, Roy Lester and Ethel Bauer f o r m a t e r i a l on mission a n a l y s i s and t ime l ines s ; J i m Ballance on o r b i t a l aerodynamics with a s s i s t a n c e from B i l l S i m s , Lockheed Miss i l e and Space Company (HREC); E . F. Fleischman f o r da ta on o r b i t a l l i f e t i m e s ; and Larry Kie f l ing and B i l l Davis f o r material on dynamics and con t ro l cons ide ra t ions .

TABLE OF CONTENTS

Page

.............. I. INTRODUCTION............................ 2

11. M I S S I O N ANALYSIS. . . . . . . . . . . . . . ........................ 2

111. ORBITAL AERODYNAMICS... ............................... 13

IV. AERODYNAMIC TORQUE .................................... 18

v. ORBITAL LIFETIME.. . . . . . . . . . . . . ........................ 29

VI. DYNAMICS AND CONTROL.... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

V I I . CONCLUSIONS... ........................................ 41

APPENDIX A: P r e l i m f n a r y Time1 ine A n a l y s i s f o r C r e w T r a n s fer E v e r y T w e l v e Hours... . . . . . . . . . . . . . . . . . . . . . . . . . . 43

APPENDIX B: P re l imina ry T ime l ine A n a l y s i s f o r C r e w Transfer E v e r y Seven D a y s ............................... 6 3

iii

.. LIST OF ILLUSTRATIONS

Figure

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T i t l e

Mission Analysis Data Flow Timeline .............. Mission P r o f i l e w i th LM Phasing E l l i p s e .......... Mission P r o f i l e with CSM Phasing E l l i p s e ......... Mission P r o f i l e with LM Phasing E l l i p s e and CSM Transfer Maneuver ................................ Docked LMICSM Axial Force Coef f i c i en t ............ Docked LMICSM Normal Force Coef f i c i en t ........... Docked LM/CSM Drag Coef f i c i en t ................... Docked LM/CSM Center of Pressure ................. LM Axial Force Coef f i c i en t ....................... LM Normal Force Coef f i c i en t ...................... LM Drag Coef f i c i en t .............................. LM Center of Pressure ............................ Reference S t a t i o n s f o r Center of Pressure Data ... ATM Lifetime vs A l t i t u d e f o r the 14-Day Broad- s i d e . 3 Month Tumbling Mode ...................... ATM Lifetime vs A l t i t u d e f o r t he 14 Day Broad- s i d e . 6 Month Tumbling Mode ...................... ATM Lifetime vs A l t i t u d e f o r the 28 Day Broad- s i d e . 3 Month Tumbling Mode ...................... ATM Lifetime vs A l t i t u d e f o r the 2 8 Day Broad- s i d e . 6 Month Tumbling Mode ...................... ATM (LM/CSM) Lifet ime vs A l t i t u d e f o r t he 14 Day Broadside. 3 Month Tumbling Mode .................

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F i g u r e

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LIST OF ILLUSTRATIONS (Continued)

T i t l e Page - ATM (LM/CSM) L i f e t i m e vs A l t i t u d e f o r the 14 Day B r o a d s i d e , 6 Month Tumbling Mode .......... 36

A'IM (LM/CSM) L i f e t i m e vs A l t i t u d e fo r the 28 Day B r o a d s i d e , 3 Month Tumbling Mode... ....... 37

ATM (T.,M/CSM) L i f e t i m e vs A l t i t u d e f o r the 28 Day B r o a d s i d e , 6 Month Tumbling Mode.. ........ 38

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DEFINITION OF SYMBOLS

Svmb o 1

a

E r

E W

H

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m

M

n

N i

D e f i n i t i o n

s emi-ma j or a x i s

a t t i t u d e con t ro l gain

a t t i t u d e r a t e con t ro l ga in

reference a r e a

a x i a l fo rce c o e f f i c i e n t

drag f o r c e c o e f f i c i e n t

normal fo rce c o e f f i c i e n t

e c c e n t r i c anomaly

i n c i d e n t energy t ransported by molecules t o a u n i t s u r f a c e i n u n i t time

energy t ransported by r e f l e c t e d molecules away from a u n i t s u r f a c e i n u n i t time

energy t ransported by r e f l e c t e d molecules away from a u n i t s u r f a c e i n u n i t t i m e i f molecules were re-emitted a t the temperature of the s u r f a c e

angular momentum of c o n t r o l moment gyro

moment of i n e r t i a

orb i t a1 i n c l i n a t i o n

molecule mass

aerodynamic moment

mean o r b i t a l angular v e l o c i t y

number of molecules i n c i d e n t on a u n i t s u r f a c e i n u n i t time

dynamic pressure

c i r c u l a r o r b i t r ad ius

v i

Symbol

R

S

E

L e

DEFINITION OF SYMBOLS (Continued)

Def in i t i on

gas constant

molecular speed r a t i o

temperature of incident molecules

temperature of r e f l e c t e d molecules

wal l temperature

v e l o c i t y of spacecraf t r e l a t i v e t o r o t a t i n g atmosphere

center-of-pressure loca t ion

center-of-gravi ty loca t ion

angle of a t t a c k ; a l so , thermal accommodation c o e f f i c i e n t

o r b i t e c c e n t r i c i t y

cont ro l damping c o e f f i c i e n t

angle between v e l o c i t y vec to r and body s u r f a c e element

g r a v i t a t i o n a l constant f o r the e a r t h , Gb&

atmospheric mass dens i ty

cont ro l frequency

r o t a t i o n a l r a t e of the ea r th ' s atmosphere

v i i

.- TECHNICAL MEMORANDUM X-53500


SUMMARY

a e l i m i n a r y ana lyses have been conducted on the Apollo Telescope Mount (A'IM) mission assuming the ARI t o be hard-mounted on a Lunar Module (IN). age.

The LM is assumed t o be modified t o accept the ATM pack-

Mission a n a l y s i s is discussed and s e v e r a l mission p r o f i l e s a r e considered. R e s u l t s a r e presented which show t h a t t he launch window f o r t he second launch can be extended by the use of a phasing e l l i p s e . Two pre l iminary t imel ines a r e included corresponding t o docking the LM t o the Command Service Module (CSM) every twelve hours or every seven days.

Resul t s of o r b i t a l aerodynamics ana lyses a r e shown. The f r e e - molecule flow drag and normal fo rce c o e f f i c i e n t s and center of pressure l o c a t i o n a r e shown as funct ions of angle of a t t a c k f o r both the LM a lone and docked CSM-LM configurat ions. These r e s u l t s a r e used i n sub- sequent ana lyses of aerodynamic torque d is turbance and o r b i t a l l i f e t i m e s . O r b i t a l l i f e t i m e s have been obtained f o r s e v e r a l modes of mission dura- t i o n and o r b i t a l s torage .

Dynamics and cont ro l a r e b r i e f l y discussed.

I. INTRODUCTION

The Apollo Telescope Mount (ATM) is a n experimental package cons i s t - ing of a group of sensors i n the v i s u a l , u l t r a v i o l e t (W), extreme u l t r a - v i o l e t (XUV) , and X-ray s p e c t r a l regions, and the necessary experimental support equipment t o ob ta in s c i e n t i f i c da t a by s o l a r observat ions from e a r t h o r b i t . I n i t i a l NASA planning f o r the ATM experiments considered mounting the ATM package t o the Apollo Service Module through a gimbal arrangement. More r e c e n t l y , considerat ion has been given t o ope ra t ion of t he ATM experiments with the ATM package hard-mounted t o the Lunar Module (LM) and the e n t i r e s p a c e c r a f t aimed toward the sun by use of con t ro l moment gyros (CMG'S).

The purpose of t h i s r e p o r t is t o document the prel iminary analyses which have been made by the Aero-Astrodynamics Laboratory r e l a t i v e t o the LM-All4 mode of operat ion. It i s intended t h a t t h i s r e p o r t w i l l supplement and support the Marshall Space F l i g h t Center ' s p r o j e c t development plan for the ATM. p r o j e c t . The preliminary analyses have been d i r e c t e d toward t h e i n i t i a l ATM mission (ATM-A) considering a dual launch of AAS 211/212. Two a d d i t i o n a l missions (ATM-By ATM-C) may fol low on l a t e r f 1 igh t s .

The LM spacec ra f t used f o r the ATM mission cons i s t s of e i t h e r an LM a s c e n t s t age and an LM descent s t a g e which has been modified t o accep t t he ATM experiments and experiment support equipment, o r a n LM ascen t s t a g e wi th an a t t ached rack holding the experiments and experiment sup- p o r t equipment. P a r t of the support equipment is a s e r i e s of con t ro l moment gyros f o r f i n e a t t i t u d e con t ro l . Nei ther the a s c e n t nor descent propuls ion engines a r e p re sen t f o r the LM-ATM conf igu ra t ion b u t t he LM r e a c t i o n control system (RCS) remains and i s used f o r momentum dump of t he CMG's.

11. MISSION ANALYSIS

The pacing item of a l l missions is t h a t of the instrument u n i t ( I U ) . A s long as the I U "milestones" a r e met, t h e launch can proceed with a predicted schedule. Mission Defining Document (MDD) about 15 months p r i o r t o launch. This is used t o e s t a b l i s h the b a s i c l o g i c f o r the f l i g h t computer, "size"the com- pu te r , s c a l e the parameters, e t c . The next input i s t h a t of t he F ina l Mission Defining Document (FMDD) about e i g h t months p r i o r t o launch. This was designed t o be a f i n e tuning and update f o r t he prescr ibed m i s - s i o n ; however, major changes can be made a t t h i s time. The l a s t program- ming input for the I U is f i v e months p r i o r t o launch a t which time minor

The f i r s t input t o the development of the I U is the

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C

. changes (constants of the same magnitude) can be made. is c o n t r a c t con t ro l l ed , and any dev ia t ion from t h i s t imel ine must be the r e s u l t of a change board a c t i o n .

This t i m e sequence

To accomplish a program with the g r e a t e s t degree of success r e q u i r e s that the mission be w e l l defined and tha t mission o b j e c t i v e s , tes t r equ i r e - ments, and c o n s t r a i n t 9 be known by about f i v e months before the MDD due d a t e (about 20 months p r i o r t o launch). This is necessary s o t h a t a n accep tab le f l i g h t p r o f i l e can be e s t ab l i shed that w i l l comply completely wi th the mission ob jec t ives and c o n s t r a i n t s . i n the same t i m e Frame, propuls ion and MSS da ta (best a v a i l a b l e ) a r e necessary t o s t a r t the t r a j e c t o r y study.

Four months p r i o r t o the MDD due da te , i t i s necessary t o s t a r t the complete t r a j e c t o r y s tudy based on b e s t a v a i l a b l e data . This lead time is necessary as t r a j e c t o r y shaping m u s t be done as we l l as s a t i s f y - ing t h e va r ious mission c o n s t r a i n t s and requirements. This s tudy can take up t o e i g h t weeks depending on the complexity and o r i g i n a l i t y of t he mission. Since other cen te r s a r e involved, an i n t e r f a c e must be e s t a b l i s h e d and close working r e l a t i o n s h i p maintained such t h a t a l l par t ies are i n complete agreement and can " t i e " t h e i r s t u d i e s together . An output from t h i s t r a j e c t o r y study is t a r g e t i n g parameters which are an inpu t f o r the guidance equation study.

Three months p r i o r t o the MDD date, a s tudy should be i n i t i a t e d t o i n v e s t i g a t e a l l poss ib l e a b o r t and a l t e r n a t e mission c a p a b i l i t i e s . the Sa tu rn IB, the s tudy is l imi t ed t o one engine out . The completion of t h i s s tudy is necessary two months be fo re the MDD due d a t e as it i s necessary input f o r t he guidance equation study.

With

Two months before the MDD due d a t e , four s t u d i e s should be s t a r t e d , two having a d i r e c t input t o the MDD, and the o the r two r e l a t i n g t o the completion of the a b o r t and a l t e r n a t e mission s tudy ,a s the b a s i c informa- t i o n becomes a v a i l a b l e . F i r s t , t h e guidance equat ion s tudy must be s t a r t e d as i t has d i r e c t i npu t t o the I U . This s tudy must include as much of the t o t a l mission l o g i c as possible . This, then, allows the com- pu te r designers t o e s t a b l i s h how much computer space w i l l be a v a i l a b l e f o r purposes o the r than guiding t h e f l i g h t . The s tudy could las t up t o s i x weeks depending upon mission complexity. Second, the r i g i d body a n a l y s i s must be s t a r t e d t o s e e i f the f l i g h t p r o f i l e s e l e c t e d demands maneuvers beyond the s t r u c t u r a l c a p a b i l i t y of t h e veh ic l e . This a l s o has a d i r e c t inf luence on the IU design. Third, w i t h the completion of t h e t r a j e c t o r y s tudy, i t is possible t o e s t a b l i s h an experiment t imel ine. Fourth, a t t h i s same time, a complete s tudy of l i f t - o f f and sepa ra t ion can b e i n i t i a t e d . This w i l l s i g n i f y any r econ tac t problems which could e x i s t and the p r o b a b i l i t y l e v e l lowered by r e t r o maneuvers of spent s t a g e s if any problem is detected. Once the experiment t imel ine has been

3

e s t a b l i s h e d , i t is necessary t o v e r i f y t h a t t he v e h i c l e has the c a p a b i l i t y t o perform these experiments. Therefore, i t is necessary t o determine what power sources a r e a v a i l a b l e and t o what e x t e n t they can be used t o f u l f i l l t he des i r ed mission. Another s tudy which l o g i c a l l y follows the experiment t imeline i s t h a t of the t r a n s m i t t a l of accumulated da ta . . This can be somewhat of a problem s i n c e the v e h i c l e i s i n r a d i o contact w i th a given s t a t i o n f o r a given time durat ion. e s t ab l i shed f o r each r ece iv ing s t a t i o n such that co l l ec t ed da ta can be properly t ransmit ted and received.

A time p r i o r i t y base must be

This completes the b a s i c a n a l y s i s which must be performed on any mission. The r e s t of the time is spent on refinement of d a t a , the updating of s t u d i e s , and s i m p l i f i c a t i o n of methods used. The only unrelated s tudy i s the f l e x i b l e body s tudy which is i n i t i a t e d a t the FMDD due da te . This s t u d y includes bending dynamics and f i l t e r design check.

A t yp ica l da t a flow i s presented i n Figure 1. It should be noted t h a t a t launch minus th ree months the I U i s t o be de l ive red t o KSC f o r f i n a l f l i g h t checkout. The t imel ine is referenced i n months p r i o r t o launch.

The mission a n a l y s i s f o r the i n i t i a l ATM (ATM-A) considering the d u a l launch of AAS 211/212 is s imi l a r t o t h a t of t h e AS 207/208 mission i n t h a t both a r e dual launches and r e q u i r e a rendezvous of the Command Service Module (CSM) with an unmanned Lunar Module (LM). The two m i s - s i ons have b a s i c a l l y the same launch v e h i c l e powered f l i g h t p r o f i l e so t h a t much of t he AS 207/208 s t u d i e s can be app l i ed t o the i n i t i a l ATM mission. One major d i f f e r e n c e i s t h a t the ATM mission is c u r r e n t l y planned f o r a nea r -c i r cu la r 200 n.m. o r b i t . This i s t o be accomplished with the use of the CSM a f t e r rendezvous a t lower e a r t h o r b i t .

Three mission p r o f i l e s have been considered f o r the dual launch. The p r o f i l e s a r e summarized i n Figures 2 through 4. A l l t h ree cases have considered t h a t the CSM would be launched f i r s t (AAS 2 1 1 ) , followed approximately 24 hours l a t e r by the launch of t he unmanned LM payload with AAS 212. The f i r s t p r o f i l e , Figure 2 , considers t he CSM is launched i n t o a 120 n.m. c i r c u l a r o r b i t followed by launch of t he LM i n t o a n e l l i p s e wi th 80 n.m. per igee and v a r i a b l e apogee depending on launch time. Af t e r one o r more o r b i t s , the CSM t r a n s f e r s t o the LM e l l i p s e and docks. Table 1 shows the time t o achieve rendezvous p o s i t i o n as a func t ion of the number of phasing o r b i t s . The remaining docking time, considering a 7 1 / 2 hour S-IVB s t a b i l i z a t i o n l i f e t i m e , is a l so shown. The LM off-load versus launch window d a t a shows the decrease i n payload weight required f o r increase i n launch window time. A f t e r docking, t he CSM c i r c u l a r i z e s i n t o a 200 n.m. o r b i t using Service Propuls ion System (SPS) burns.

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TABLE 1

Summary Table fo r LM Phasing E l l i p s e

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Number of

Orb i ts

1 114

1 314

2 114

2 314

3 114

3 314

Time t o Achieve Rendezvous Pos i- t i o n (hrs)

Payload vs Launch Window

J,M OFF Launch Window Load

(Ibs 1 (min)

1.87

0 3.6

300 4.7

I 1000 I 6.8

2.63

0 7.2

0 I 7.3

3.37 I 300 1 9.2

1000 13.2

0 11.0

4.13

4.88

1000 19.6

0 14.5

5.63

Docking Time Remaining

(hrs 1

5.63

4.87

4.13

3.37

2.62

1.87

7

The second p r o f i l e , Figure 3 , considers the CSM is launched i n t o a 120 n.m. c i r c u l a r o r b i t followed by launch of t he LM i n t o the same o r b i t . The CSM then brakes a t per igee i n phase with LM and docks. ing, the CSM c i r c u l a r i z e s i n t o a 200 n. m. o r b i t using SPS burns. Table 2 shows the launch window a v a i l a b l e as a funct ion of CSM phasing o r b i t apogee. Time to achieve rendezvous and remaining docking time f o r a 7 1 / 2 hour S-IVB s t a b i l i z a t i o n l i f e t i m e a r e a l s o shown as a func t ion of the number of o r b i t s f o r the phasing maneuver.

The CSM then burns i n t o a v a r i a b l e apogee t o phase with LM. Afte r dock-

The th i rd p r o f i l e , Figure 4 , considers t he CSM t o be launched i n t o a 100 n.m. c i r c u l a r o r b i t followed by the LM launched i n t o an o r b i t with 120 n.m. perigee and v a r i a b l e apogee depending on launch time. The CSM then i n i t i a t e s the t r a n s f e r maneuver, matches the v e l o c i t y of LM i n the e l l i p s e , a n d docks. A f t e r docking, t he CSM c i r c u l a r i z e s i n t o a 200 n.m. o r b i t . Table 3 shows the corresponding launch window and docking time d a t a f o r t h i s p r o f i l e . Of these p r o f i l e s , t h e f i r s t one discussed with LM e l l i p t i c a l phasing appears most a t t r a c t i v e a t t h i s time s i n c e the LM i n i ts ATM conf igu ra t ion is not a t a l l weight c r i t i c a l and con- s i d e r a b l e f l e x i b i l i t y can be maintained i n choosing the LM phasing e l l i p s e apogee. The LM-ATM conf igu ra t ion is est imated t o be 11,500 t o 19,000 pounds from References 1 and 2 , r e s p e c t i v e l y .

The CSM has been considered t o be launched f i r s t because of the l imi t ed S-IVB s t a b i l i z a t i o n l i f e t i m e f o r the unmanned LM payload and the assumption t h a t t he CSM w i l l dock t o the LM and e f f e c t t he LM/S-IVB sepa ra t ion . For the ATM mission,however, t h e r e may be v a l i d reasons f o r launching the unmanned payload f i r s t , a c t i v a t i n g LM subsystems and e f f e c t i n g separat ion from the S-IVB p r i o r t o the manned launch. The ope ra t ion of the LM-ATM spacecraft , including proper a t t i t u d e hold capa- b i l i t y f o r the CMG system, may be des i r ed before committing the manned launch. Of course, i f the LM-ATM payload i s sepa ra t ed from t h e S-IVB s t a g e before CSM docking, then the s h o r t S-IVB s t a b i l i z a t i o n l i f e t i m e i s no longer a problem. It i s recommended t h a t cons ide ra t ion be given t o t h i s mode of operat ion.

Two preliminary t imel ines f o r the Apollo Telescope Mount mission a r e presented i n Appendices A and B y r e f l e c t i n g the assumption of crew t r a n s f e r every twelve hours o r every seven days, r e s p e c t i k e l y . Shown i n the t imelines a r e crew scheduling of experiment and housekeeping d u t i e s , and the geometric considerat ions of ascending and descending node posi- t i o n s , major l a n d masses, day-night per iods, and t r ack ing . The l i s t of assumptions accompanies the t imel ines i n Appendix A. Another p o s s i b l e mode of operation i s i n the docked CSM-LM conf igu ra t ion during the e n t i r e 14 days. T h i s mode has s e v e r a l advantages and disadvantages r e l a t i v e t o the undocked mode and w i l l r e q u i r e a n a l y s i s .

8

.

.

U

C n L * n

ZE a3

i -I c c .- L Q) en 0 r CL

0

W W CT 0 CL 0

c

m

9

TABLE 2

Summary Table f o r CSM Phasing E l l i p s e

I Al t i tude of Apogee (HA) vs Launch Window

Launch HA Window

Docking Time Rem ining

(hrs 1

400 5.6 5.25

520 7 .6

350 8.8 400 11.3 3.75

520 15.3

350 13.3 400 1 7 . 1 2.25

5 20 23.3 I I

-1.

" 1 / 2 o r b i t a l l oca t ed f o r o r b i t determination.

10

I . CSM launched into a I00 n mi circular orbit and tracked.

3. CSM opt ica l ly tracks LM and initiates transfer manuever.

F16. 4 . M I S S I O N P R O F I L E

2. LM launched into a 120 n mi perigee and variable apogee el l ipse, depending on the launch t ime.

4. CSM matches velocity o f LM in e l l ipse and docks.

W I T H L M P H A S I N G E L L I P S E AND CSM T R A N S F E R M A N E U V E R

11

TABLE 3

Summary Table f o r LM Phasing E l l i p s e and CSM Transfer Maneuver

LM Off Load (1bs 1

300

Time t o Achieve Rendezvous Pos i- t i o n (h r s )

Launch Window (min)

1.5

2100

2800

2.25”

6.2

8.3

2100

2800

300

1000

1700

2100

2800

3.75

12 .3

16.6

4.4

8.5

15 .3 2.25

18 .4

24.8

1700 10.1

5.25

Docking Time Rema i n ing

(hrs 1

5.25

3.75

-9-

An a d d i t i o n a l 112 o r b i t has been-a l loca ted f o r t h e t r a n s f e r maneuver.

1 2

111. ORBITAL AERODYNAMICS

The o r b i t a l aerodynamic c h a r a c t e r i s t i c s of the o r b i t i n g veh ic l e s t o be considered i n the A'IM program have been determined by s tandard ca l cu la t ions . explained i n t h i s s ec t ion .

The approach and assumptions used f o r t h i s a n a l y s i s a r e

A s p a c e c r a f t passes through the atmosphere a t o r b i t a l a l t i t u d e s . Tne aerodynamic c h a r a c t e r i s t i c s of t h i s c r a f t depend on f a c t o r s such as shape, s i z e , speed, and su r face condi t ions as we l l as the p rope r t i e s of the atmosphere such as dens i ty , temperature, and composition. The most no tab le f e a t u r e of t h i s f l i g h t is t h a t the dens i ty is so low that cor- puscular behavior occurs. This means that the incoming molecules ( r e l a - t i v e t o the spacec ra f t ) which co l l i de wi th the body a r e not influenced by molecules which have a l r eady co l l i ded and a r e rebounding. This type of flow is ca l l ed f r e e molecule flaw and occurs normally when the mean f r e e pa th of t h e molecule ( the average d i s t ance that a molecule t r a v e l s between success ive c o l l i s i o n s wi th other molecules) is 10 or more times g r e a t e r than the c h a r a c t e r i s t i c body dimension. The b a s i c parameter used t o desc r ibe var ious flow regimes is the Knudsen number, G, which is t h e r a t i o of the mean f r e e path t o the c h a r a c t e r i s t i c dimension.

Since the inc iden t flow t o a body i n the f r e e rcolecule regime is undisturbed by the presence of that body, the equi l ibr ium v e l o c i t y d i s t r i b u t i o n of the inc ident molecule is changed only by molecule-body c o l l i s i o n s . Therefore, the e f f e c t s of the inc iden t and r e f l e c t e d mole- cu les can be analyzed separa te ly .

I n f r e e molecule flow, the forces and moments on a body a r e funct ions of on ly th ree parameters and the geometric conf igura t ion of that body. One parameter, t he molecular speed r a t i o , is def ined a s ,

.\, 2RTi

where Vr is the v e l o c i t y of the body of i n t e r e s t , Ti is the average tem- p e r a t u r e of the inc iden t molecules and is the second parameter; R is the gas cons tan t of t he p a r t i c u l a r gas of i n t e r e s t . i s t h e average temperature of t he molecules r e f l e c t e d from the body s u r - f ace . temperature r a t i o , T , / T ~ .

The t h i r d parameter, Tr ,

Tr and T i a r e commonly used a s the r e f l ec t ed - to - inc iden t molecular

13

The forces and moments a c t i n g on a body i n f r e e molecule flow a r e a funct ion of the molecule-surface i n t e r a c t i o n . This i n t e r a c t i o n i s considered i n two parts, the momentum t r a n s f e r r e d t o the s u r f a c e and the energy t r ans fe r r ed t o the su r face . The momentum which is imparted t o the surface depends on the type of r e f l e c t i o n ; e i t h e r specu la r (when the angle of r e f l e c t i o n equals the angle of incidence) o r d i f f u s e (when the molecule s t r i k e s the su r face and is re-emitted i n a random d i r e c - t i o n ) . The f r a c t i o n of t he inc iden t molecules which a r e d i f f u s e l y r e f l e c - ted i s known as the r e f l e c t i o n c o e f f i c i e n t . Specular r e f l e c t i o n i s no t considered i n present c a l c u l a t i o n s s i n c e molecule-surface i n t e r a c t i o n experiments conducted t o da t e on o r b i t a l v e h i c l e type su r faces i n d i c a t e an almost completely d i f f u s e r e f l e c t i o n . Thus, the assumption of com- p l e t e l y d i f f u s e r e f l e c t i o n i n the flow f i e l d model introduces only a s l i g h t e r r o r i n the fo rce c o e f f i c i e n t values . I n the case of d i f f u s e l y r e f l e c t e d molecules, momentum i s t r a n s f e r r e d t o the body s u r f a c e only i n a normal d i r e c t i o n (zero t angen t i a l momentum).

The degree of thermal equi l ibr ium a t t a i n e d between the molecule and body su r face before re-emission of the molecule is measured by t h e energy o r thermal accommodation c o e f f i c i e n t , a, defined as

E i - Er

Ei - Ew a =

where

E . i s the t o t a l i nc iden t energy t ransported by the molecules 1 t o a u n i t su r f ace a r e a i n u n i t time,

E, i s the t o t a l energy t ransported by the r e f l e c t e d molecules away from a u n i t s u r f a c e a r e a i n u n i t time, and

E, i s the t o t a l energy the r e f l e c t e d molecules would t r a n s p o r t away from a u n i t s u r f a c e area i n u n i t time i f they were re-emitted a t the temperature of the su r face .

It w i l l be shown l a t e r t h a t T , / T ~ e n t e r s i n t o the r e s u l t a n t fo rce coef- f i c i e n t equations as a measure of t h i s energy e f f e c t . The assumption of complete thermal accommodation, where T, = Tw and a = 1 . 0 , i s not as wel l founded as the assumption of d i f f u s e r e f l e c t i o n . The thermal accommoda- t i o n c o e f f i c i e n t m u s t be obtained experimental ly o r es t imated based on previous data f o r s imilar su r faces and i n c i d e n t molecular p r o p e r t i e s . It is a function of molecule weight, s u r f a c e temperature, the m a t e r i a l , f i n i s h , age, and h i s t o r y of the s u r f a c e , and, when the molecules possess a l a r g e mass motion, the h i s t o r y of the molecular speed r a t i o and the

14

d i r e c t i o n cosines between the surface and the d i r e c t i o n of mass flow. Experimental values of t he thermal accommodation c o e f f i c i e n t obtained t o d a t e f o r su r faces and impinging molecules t y p i c a l of those a t o r b i t a l a l t i t u d e s have the range 0.7 5 a S 1.0. The e r r o r introduced i n f r e e molecule f o r c e c o e f f i c i e n t values by assuming a = 1.0 w i l l be discussed la ter .

The equat ion f o r t he f o r c e on an element of a r e a i n f r e e molecule flow may be computed using k i n e t i c theory r e l a t i o n s h i p s and a Maxwellian v e l o c i t y d i s t r i b u t i o n . Since the e f f e c t s o€ t he inc iden t and r e f l e c t e d molecules can be analyzed sepa ra t e ly , t h e t o t a l f o r c e on t h e element of area is obtained by summing t h e force due t o t h e i n c i d e n t molecules and that due t o t h e r e f l e c t e d molecules. A geometric assumption made here is that the element of area is located on a f l a t o r convex surface. A concave s u r f a c e would produce a force on the element of area due t o the molecules t h a t have been r e f l e c t e d from o the r p a r t s of the body, which is n o t taken i n t o account i n the following equation. The fo rce equation i s der ived i n Reference 3 . The nondimensional f r e e molecule fo rce coef- f i c i e n t equation r e s u l t i n g from t h i s d e r i v a t i o n i s

where

k , a , t a r e d i r e c t i o n cosines between the l o c a l x , y , and z (with r e spec t t o a n element of su r f ace , y i s t h e inward d i r ec t ed normal and x and z a r e tangent t o the s u r f a c e ) axes and the des i r ed fo rce d i r e c t i o n ,

€ 9 Y, 7 are d i r e c t i o n cosines between t h e l o c a l x , y, and z axes and the r e l a t i v e v e l o c i t y vec to r .

This equation is exact w i t h i n the physical assumptions of k i n e t i c theory, f r e e molecule flow, d i f f u s e r e f l e c t i o n , and non-concave su r faces . Shadow- ing on one po r t ion of a p a r t i c u l a r shape by another po r t ion of t h a t shape and t h e e f f e c t of t he random thermal motion of t he molecules a r e included i n t h e equation. Shadowing by one body on another i s no t included.

15

. To examine the e f f e c t of thermal accommodation c o e f f i c i e n t s , w e

look a t equation (2) , where one may w r i t e f o r d i f f u s e l y r e f l e c t e d mol e cu l e s

Er = 2m Ni RTr

Ew = 2m N i RT,

and

where

Solving equation ( 2 ) f o r E, g ives

E = (1 - a) E i + a Ew. r

Subs t i t u t ing f o r E i , E,, and E, g ives

(7)

Simplifying and introducing equat ion (1) g ives

and

16

For a body sur face normal t o the r e l a t i v e v e l o c i t y , Vr, and wi th S > 5, which is the case f o r o r b i t a l a l t i t u d e s of a t l e a s t 1000 km o r l e s s , e = 90" and p(S,e) + 0; then

Tr m CS2 + $1 + a - TW . - - Ti - 2 Ti

For a body s u r f a c e parallel t o the r e l a t i v e v e l o c i t y , Vr, and f o r any value of S, e = 0" and @(S,Q) ' 0 0 ; then,

TW

Ti - - Tr - [ s 2 + 2 ] + a - .

- 2 Ti

It is seen, therefore , that fo r p r a c t i c a l o r b i t a l a l t i t u d e s (S > 5), equations (10) and (11) have e s s e n t i a l l y the same value. This i nd ica t e s t h a t the r e f l ec t ed - to - inc iden t temperature r a t i o , T r / T i , is p r a c t i c a l l y unaffected by s u r f a c e o r i e n t a t i o n .

Now, w h a t i s the e f f e c t of body s u r f a c e temperature, Tw, on T r / T i ? Consider a body i n a 200 n.m. o r b i t , T i = 1470"K, wi th a s u r f a c e tem- p e r a t u r e of 300°K ( the sur face temperature p re sen t ly assumed f o r a l l o r b i t i n g bodies when determining the aerodynamic force c o e f f i c i e n t s f o r that body). For a temperature v a r i a t i o n over the sur face of 5 0 " K , the r a t i o of T, /T~ v a r i e s from 0.170 t o 0.238. Then, f o r a = 1, the assump- t i o n i n the p re sen t flow f i e l d model, T,/Ti = T r / T i , and the r a t i o is d i r e c t l y a f f e c t e d by the sur face temperature v a r i a t i o n . 50°K v a r i a t i o n w i l l then produce a 40 percent v a r i a t i o n i n Tr /T i . However, the con t r ibu t ion of the r e f l e c t e d molecules t o the force c o e f f i c i e n t values i s an order of magnitude l e s s than t h a t of the i n c i d e n t molecules so t h a t t he a c t u a l e f f e c t of sur face temperature v a r i a t i o n on the force c o e f f i c i e n t magnitudes is l e s s than 2 percent . With a < 1 and S > 5, as is the ac tua l case, the e f f e c t of sur face tem- pera tu re v a r i a t i o n on T r / T i i s considerably l e s s , becoming l e s s than 1 percent as a decreases below a value of 0.75. The e f f e c t on force c o e f f i c i e n t magnitudes is then negl ig ib le .

The assumed

F ina l ly , what is the e f f e c t of the thermal accommodation coef- f i c i e n t , a, on T r / T i , thus, on the force c o e f f i c i e n t magnitudes? Look- ing aga in a t equations (10) and ( l l ) , we see t h a t as a v a r i e s from 1 t o 0, T r / T i is r a d i c a l l y a f f e c t e d and w i l l vary from l e s s than 0.2 t o a va lue of 50 o r g r e a t e r , depending upon the value of S. Since the

17

con t r ibu t ion of the r e f l e c t e d molecules i s mul t ip l i ed by (Tr/Ti)'/*, t h i s con t r ibu t ion t o the fo rce c o e f f i c i e n t magnitudes can be increased from an order of magnitude l e s s than t h a t of the inc iden t molecules t o the same order of magnitude as a + 0. Therefore, v a r i a t i o n s i n a can s i g n i f i c a n t l y a l t e r the fo rce c o e f f i c i e n t magnitudes.

Using the approach ou t l ined above, o r b i t a l aerodynamic character- i s t i c s fo r the CSM docked with the LM and f o r the LM a lone have been calculated. Figures 5 through 1 2 present the a x i a l fo rce c o e f f i c i e n t , normal force c o e f f i c i e n t , drag c o e f f i c i e n t , and cen te r of pressure f o r these configurat ions f o r a 200 n a u t i c a l mile o r b i t . Figure 13 shows the reference pos i t i ons f o r t he center of pressure da t a . The coef- f i c i e n t s a r e based upon a r e fe rence a r e a of 33.47 square meters. These r e s u l t s were computed assuming t h a t b a t t e r i e s supply power f o r the 14-day mission i n a "brute force" approach. The use of s o l a r c e l l a r r a y s complicates the determination of the f r e e molecule flow aerodynamic c h a r a c t e r i s t i c s which has no t been performed a t t h i s time pend- ing more d e f i n i t e information concerning the s o l a r a r r a y designs. For the case where ATM is placed i n o r b i t a l s to rage a t the end of the 14-day mission and then r e a c t i v a t e d a t a l a t e r time, the b a t t e r y approach i s no t acceptable .

I V . AERODYNAMIC TORQUE

The free-molecule drag and normal fo rce c o e f f i c i e n t s presented i n the previous s e c t i o n have been used f o r o r b i t a l l i f e t i m e analyses and aerodynamic torque considerat ions. The o r b i t a l l i f e t i m e r e s u l t s a r e discussed in the next s ec t ion . This s e c t i o n presents the aerodynamic torque ana lys i s necessary f o r con t ro l analyses and CMG angular momentum considerat ions.

The mass dens i ty of the upper atmosphere can be computed from a s e r i e s of equations given by Smith [4] . The maximum mass d e n s i t y , h, that can be expected a t 200 n.m. a l t i t u d e i n the l a t e ' 68 o r e a r l y '69 time frame is obtained as 1.58 x 10-l' kg/m3. This value f o r mass d e n s i t y i s subsequently used f o r the c a l c u l a t i o n of dynamic pressure.

Neglecting terms of the order (Qe/n)', Sterne [5] shows that the r e l a t i v e ve loc i ty of the s p a c e c r a f t with r e s p e c t t o the r o t a t i n g atmosphere can be expressed by

L

1 - E C O S E cos i 1 + E cos E

18

Axial Force Coefficient, C A

t 2.0

1.6

1.2

.8

.4

0

-.4

-. 8

-1.2

-1.6

-2.0 0 20 40 60 80 100 120 140 160 180

F16. 5 . D O C K E D L M / C S M A X I A L F O R C E C O E F F I C I E N T

19

c

c

23

W

2 9

L. 0 z

c

a 0 L

24

I -

I -

-

25

W

3 M M Y a e

y. 0

a W c L W 0

a

L 4

N - cm y. -

26

I I

LL 0

pc 0 LL - L 0

c c - - W u L W pc W LL W CL

For a c i r c u l a r o r b i t , t h i s reduces t o

I

where the f i r s t term i s the i n e r t i a l v e l o c i t y f o r a c i r c u l a r o r b i t .

The r e l a t i v e v e l o c i t y has been obtained f o r a 200 n.m. a l t i t u d e and found t o be 7260 km/sec from the above equation, where

p = GMe = 0.3986 x 10' km"/sec2

r = 6378 + 370 = 6748 km

Re = 7 . 2 9 2 x r a d / s e c

n = (p/r3)1/2 = 1.139 x 10'" r a d / s e c

cos i = cos 29.5" = 0.8704.

The dynamic pressure, q , i s then obtained:

q = ( 1 / 2 ) p V2 = 4.164 x lom3 N/mz (8.697 x l b / f t 2 ) . m r

From t h e previous s e c t i o n , the maximum normal f o r c e c o e f f i c i e n t is 1.36 for LM alone and 3.04 f o r the docked CSM-LM conf igu ra t ion . The corresponding center of p re s su re i s 101 inches from the LM docking c o l l a r fo r LM alone and 318 inches from the SM nozzle e x i t plane f o r the CSM-LM veh ic l e .

Current es t imates from Propulsion and Vehicle Engineering Laboratory place the center of g r a v i t y a t LM S t a t i o n 187 f o r LM alone and a t LM S t a t i o n 390 f o r the CSM-LM docked configurat ion. I n the docked con- f i g u r a t i o n , the nozzle e x i t plane of the SM i s 387 inches from the docking c o l l a r where the docking c o l l a r corresponds t o LM S t a t i o n 312.5. From these r e s u l t s , the cen te r of p re s su re is 24.5 inches c l o s e r t o t h e docking c o l l a r than the cen te r of g r a v i t y f o r t he LM a lone . For the docked CSM-LM v e h i c l e , the cen te r of p re s su re i s 8.5 inches c l o s e r t o the docking c o l l a r than the cen te r of g r a v i t y . Considering the "nose" t o be the opposite end from the SM nozzle and a "nose-up" moment as p o s i t i v c , the aerodynamic torque from these r e s u l t s would be p o s i t i v e (nose-up) fo r the CSM-LM v e h i c l c and nega t ive (nose-down) f o r the LM a l o n e configurat ion. The magnitude of t he maximum aerodynamic moment i s as follows:

28

8

IM Alone

= (1.36)(4.164 x N/m2)(33.47 m2)(0.62 m)

= 0.118 N-m (0.087 f t - lb ) .

CSM-LM

= (3.04)(4.164 x N/m2)(33.47 m2)(0.22 m)

= 0.093 N-m (0.069 f t - l b ) .

Thus, i t is observed t h a t t h e aerodynamic d i s tu rbance torque i s about t he same magnitude f o r both configurat ions.

V. ORBITAL LIFETIME

The o r b i t a l l i f e t i m e f o r proposed configurat ions and modes of ope ra t ion are presented i n t h i s s ec t ion . I n consider ing the l i f e t i m e s a s s o c i a t e d wi th the va r ious o r b i t i n g conf igu ra t ions and modes of opera- t i o n , t he masses, drag c o e f f i c i e n t s , a l t i t u d e s , and atmospheric d e n s i t y are the most c r i t i ca l parameters. A l l the l i f e t i m e s a r e t h e r e f o r e p r e - sented as a func t ion of a l t i t u d e . The atmospheric d e n s i t y , which is probably the most c r i t i c a l of parameters a s soc ia t ed wi th p red ic t ing o r b i t a l l i f e t i m e , is d i r e c t l y associated wi th s o l a r a c t i v i t y . That is , as s o l a r a c t i v i t y increases , the densi ty of t he atmosphere increases , and hence, t he higher t he s o l a r a c t i v i t y the lower the o r b i t a l l i f e t i m e . The l i f e t i m e s t u d i e s were based on a la te 1968 launch which is predicted t o be the period of maximum s o l a r a c t i v i t y . The s t a t i s t i ca l dev ia t ions , +2a, a r e based on predicted v a r i a t i o n s i n t h e p re sen t s o l a r cycle which w i l l a t t a i n i t s maximum i n l a t e 1968 o r e a r l y 1969.

The four modes of ope ra t ion which were inves t iga t ed a r e as follows:

(a) Fourteen days broadside, t h ree month tumbling.

(b) Fourteen days broadside, s i x month tumbling.

29

(c) Twenty-eight days broadside, t h ree month tumbling,

(d) Twenty-eight days broadside , s i x month tumbling . These modes r ep resen t cycles of operat ion time during which the re occur fourteen or twenty-eight days of o r b i t a l experimentation and th ree o r s i x months of LM o r b i t a l s to rage . These cycles of operat ion were assumed to r ecu r throughout the o r b i t a l l i f e t i m e . Although the r e s u l t s have been obtained f o r the broadside mode during the a c t i v e mission per iods, the v e h i c l e w i l l a c t u a l l y be i n e r t i a l l y o r i en ted toward the sun. A s the v e h i c l e emerges from the e a r t h ' s shadow, i t w i l l be a l igned f a i r l y well with the v e l o c i t y vec to r . A t noon the veh ic l e is t r a v e l i n g broadside, and a t dusk i t is e s s e n t i a l l y a l igned aga in with the v e l o c i t y vec to r . This assumes t h a t the ATM spa r is along the v e h i c l e ' s center- l i n e . The broadside assumption f o r l i f e t i m e a n a l y s i s gives conservat ive r e s u l t s for the LM and CSM-LM configurat ions without s o l a r c e l l a r r a y s . With s o l a r c e l l s , the drag c o e f f i c i e n t w i l l i nc rease appreciably a t l o w angle of a t t a c k . The broadside drag w i l l not i nc rease s i n c e the s o l a r panels a r e edge on t o the v e l o c i t y vec to r .

Figures 14 through 1 7 present r e s u l t s of the l i f e t i m e s t u d i e s f o r the LM configurat ion. the tumbling drag c o e f f i c i e n t is 1.31, the l i f e t i m e s f o r t he four o r b i t - ing modes a r e e s s e n t i a l l y the same. The conf igu ra t ion mass assumed is 8182 kg (18,000 lbm). These r e s u l t s a r e based upon the previous drag data presented which do not include s o l a r panels .

Since the broadside drag c o e f f i c i e n t is 1.34 and

Figures 18 through 2 1 show the corresponding r e s u l t s f o r the CSM-LM configurat ion. The broadside drag c o e f f i c i e n t is 3.04, and a mass of 18,182 kg (40,000 lbm) was assumed. For the o r b i t a l s t o r a g e pe r iods , the LM tumbling drag of 1.31 and LM mass were used. These r e s u l t s can be considered q u i t e app l i cab le f o r the CSM-LM v e h i c l e with s o l a r panels s i n c e i t i s estimated t h a t the v e h i c l e drag a t low ang le of a t t a c k (with s o l a r panels broadside) i s l e s s than the v e h i c l e broadside drag used. For o r b i t a l s t o r a g e , the panels a r e s t o r e d about the LM v e h i c l e i n such a way t h a t the tumbling drag with panels may not exceed the tumbling drag without panels .

More extensive a n a l y s i s i s needed r e l a t i n g t o o r b i t a l aerodynamics with s o l a r panels s i n c e these panels w i l l shade o the r po r t ions of t he veh ic l e a t var ious angles of a t t a c k and s i d e s l i p and complicate the a n . a l y s i s . When these more d e t a i l e d aerodynamic c h a r a c t e r i s t i c s a r e a v a i l a b l e , more d e t a i l e d aerodynamic torque d i s tu rbance and o r b i t a l l i f e t i m e analyses can be conducted.

.

30

.

F16.

Lifetime (day)

Altitude (n mi)

14. ATM LIFETIME VS ALTITUDE FOR THE 14 D A Y BROADSIDE, 3 MONTH TUMBLIWG MODE

JJ.

Lifetime (day)

F I G . 1 5 . A T M L I F E T I M E 1 V S ALTITUDE FOR THE 14 D A Y BROADSIDE, 6 MONTH T U M B L I N G M O D E

3 2

Lifetime (day)

'" 120 140 160 180 -

200 Altitude (n mi)

F l 6 . 16. ATM L I F E T I M E V S ALTITUDE FOR THE 28 DAY BROADSIDE, 3 M O N T H TUMBLING MODE

33

Lifetime (day)

103

102

10 ’

140 160 180 200 loo

120 Altitude (n mi)

a l

FIG. 17. A T M L I F E T I M E V S ALTITUDE FOR T H E 28 D A Y BROADSIDE, 6 M O N T H T U M B L I N G M O D E

0

c

.

34

.

Afttime (day)

140 160 180 200 220 240 260 Altitude (n

F16. 18. A T M (LM/CSM] L I F E T I M E V S A L T I T U D E F O R T H E 14 D A Y B R O A D S I D E ,

3 M O N T H T U M B L I N G MODE

-

mi)

35

,if

I04

103

IO2

IO’ 1

ime (day)

mil

F I G . 19 . A T M [ L M / C S M ] L I F E T I M E V S A L T I T U D E FOR T H E 1 4 D A Y B R O A D S I D E ,

6 M O N T H T U M B L I N G M O D E

Li fe t ime (day)

io4

lo3

I O 2

26 Alti tude (n

IO’ 140 160 180 200 220 240

A T M [LM/CSM] L I F E T I M E V S A L T I T U D E F O R T H E 28 D A Y B R O A D S I D E ,


F16. 20.

10 mil

37

F I G . 21 . A T M ( L M / C S M ] L I F E T I M E V S A L T I T U D E FOR T H E 2 8 D A Y B R O A D S I D E ,


VI. DYNAMICS AND CONTROL

Several of t he dynamic, s t a b i l i t y , and con t ro l problems and the a n a l y t i c a l methods f o r t h e i r so lu t ion a r e ou t l ined below. i n genera l , a r e ve ry similar t o those f o r the Saturn veh ic l e s and o the r spacec ra f t analyzed previously. The methods now used should be su f - f i c i e n t , w i th few except ions, f o r ana lys i s of t he ATM. s p e c i f i c computer programs now used a r e , of course, h ighly s p e c i a l i z e d f o r g r e a t e r e f f i c i ency . f o r t he A'IM would depend on the number of conf igura t ions t o be analyzed and poss ib ly t h e need t o include e f f e c t s now neglected.

These problems,

Some of t he

The amount of spec ia l i zed methods t o be developed

The f r e e v i b r a t i o n ana lys i s would probably be s t ra ight forward bu t could r equ i r e a moderately l a rge manpower e f f o r t i f a d e t a i l e d s t r u c - t u r a l model is needed. An energy method would be most l i k e l y , probably something s i m i l a r t o the VISA program now used f o r t he uprated Saturn I veh ic l e . This superimposed normal mode technique has been found t o be accu ra t e , convenient, and economical. Of course, t he exact technique cannot be determined u n t i l a f t e r a s tudy of t he s t r u c t u r e . The present knowledge of p a r t of t he s t r u c t u r e should be very usefu l and reduce the t o t a l e f f o r t requi red .

The above d iscuss ion has considered the s t r u c t u r e t o be l i n e a r . This would need t o be v e r i f i e d . would g r e a t l y complicate the ana lys i s . An ana lys i s would probably need t o be s p e c i a l l y developed.

The presence of l a r g e n o n l i n e a r i t i e s

The s t r u c t u r a l damping would probably be very similar t o that of p re sen t veh ic l e s f o r e a r t h environment. The changes due t o space environment would need t o be c a r e f u l l y examined, e s p e c i a l l y s i n c e a long l i f e - time is des i r ed . This l abora to ry has sponsored damping s t u d i e s i n the p a s t and is c u r r e n t l y examining l i t e r a t u r e on space environmental e f f e c t s .

P rope l l an t s l o s h dynamics would need t o be analyzed. Low-g s l o s h a n a l y s i s methods a r e now f a i r l y well developed and progress toward b e t t e r understanding of the phenomenon is good. A usefu l s l o s h a n a l y s i s f o r t he AIM should be poss ib le .

Current con t ro l system s t a b i l i t y and response analyses should be t o t a l l y adequate f o r the ATM system i f no n o n l i n e a r i t i e s occur. Present equat ions would r equ i r e very l i t t l e or no change. A system wi th non- l i n e a r i t i e s would r equ i r e more ana lys i s . Present ly , a system of com- pu te r programs is used f o r t hese analyses . The f i r s t genera tes the c o e f f i c i e n t of t he matr ices f o r the system. This program may need some minor modi f ica t ion s i n c e the input format could depend on the method of s t r u c t u r a l v i b r a t i o n ana lys i s . The s t a b i l i t y program could probably be used without a l t e r a t i o n . The response program may r e q u i r e a d d i t i o n

39

of a d i f f e r e n t forcing func t ion t o s imulate crew movements. The crew movements and the crew's physical movement r eac t ions t o v e h i c l e motions would be p a r t of the feedback loop and t h e i r random movements would need t o be known. These programs a r e used as a system,and da ta handling is done by magnetic tape t o reduce chance of human e r r o r .

One of the f i r s t items t o be s tud ied should be docking dynamics. This would include r i g i d and f l e x i b l e body s t a b i l i t y a n a l y s i s of the con t ro l system during coupling, s l o s h dynamics , and coupling fo rces . Analyses f o r these items a r e now under development. Dynamics and con- t r o l analyses while i n the docked configurat ion a l s o w i l l r e q u i r e exten- s i v e s t u d y i f a docked mode of ATM ope ra t ion is choosen.

It i s e a s i l y shown t h a t i f the con t ro l frequency and damping of the LM with CMG con t ro l i s 1.3 cycles per second and 0.7, r e s p e c t i v e l y , then when the CSM docks, the con t ro l frequency and damping a r e reduced about one-half with the LM holding the con t ro l gains constant . For example, the approximate equations [ 2 ] f o r the con t ro l frequency and damping a re

w = k IT- c 3

5, = (2/3) (al/ao)

When t h e CSM docks, the t o t a l conf igu ra t ion moment of i n e r t i a , I, may inc rease by a f a c t o r of about f o u r , thus e f f e c t i n g the r educ t ion of con- t r o l frequency and damping. the combined veh ic l e i s a t l e a s t 1.3 cycles per second, then the re w i l l be a one octave o r more frequency d i f f e r e n c e between the f i r s t s t r u c t u r a l mode and the con t ro l frequency. No a d d i t i o n a l s t a b i l i t y problems would be a n t i c i p a t e d t h a t were no t a l r e a d y inhe ren t i n the LM-CMG system. However, the response time of the docked v e h i c l e would be twice as long, and the disturbances would r e q u i r e a longer time t o damp ou t compared t o the LM configurat ion.

If the f i r s t mode s t r u c t u r a l frequency of

If the con t ro l sensors a r e located near t he sources of appl ied moment, then the s t r u c t u r a l bending modes a r e usua l ly phase s t a b i l i z e d . Although the bending i t s e l f is s t a b l e , t he system wi th f l e x i b l e dynamics w i l l no longer possess the same des i r ed dominant r o o t c h a r a c t e r i s t i c s as the s i m p l i f i e d r i g i d body system. by r o o t locus, and the con t ro l gains ad jus t ed t o produce the des i r ed

u s u a l l y the system m u s t be analyzed

40

r e s u l t s . located near the CMGs w i l l produce p h a s e stable s t r u c t u r a l modes without a d d i t i o n a l compensation by f i l t e r s . However, as i n booster con t ro l w i th point-of-force sensing, the system w i t h f l e x i b l e dynamics must be analyzed and the con t ro l ga ins adjusted t o produce the des i r ed dominant r o o t l o c a t i o n i n the complex plane.

The con t ro l system of the docked IM and CSM w i t h sensors

I n conclusion, a n a l y s i s programs have a l r e a d y been developed i n the areas of s t r u c t u r a l - f r e e v i b r a t i o n , vehicle s t a b i l i t y , and v e h i c l e response. The docking dynamics mode is a s t r a igh t fo rward extension of these methods. The damping and low-g s l o s h problems may s t i l l r e q u i r e some s t a t e -o f - the -a r t development. Progress i s now being made i n these a r e a s , e s p e c i a l l y i n low-g s l o s h , where much advanced work is being sponsored by t h i s laboratory. The presence of n o n l i n e a r i t i e s would c m p l i c a t e b u t would not b a s i c a l l y change the s o l u t i o n of the problem.

V I I . CONCLUSIONS

1. More d e t a i l e d mission ana lys i s is necessary t o f i rmly de f ine the mission. This r e p o r t assumes a dual launch wi th the CSM launched f i r s t , rendezvous a t low e a r t h o r b i t w i t h use of t he CSM f o r t r a n s f e r tcj the higher o r b i t , and ope ra t ion of the LM i n a n undocked mode.

2. More d e t a i l e d t imel ine analyses must be performed when b e t t e r information i s a v a i l a b l e r e l a t i v e to experiment requirements. This r e p o r t assumes four experiments, several of which may n o t be compatible w i t h the f l i g h t schedule. Early s e l e c t i o n of experiments f o r the f i r s t ATM m i s s ion must be made.

3. More d e t a i l e d a n a l y s i s of t he aerodynamic dis turbance torques about a l l t h ree body axes is needed as the v e h i c l e o r b i t s about t he e a r t h i n an i n e r t i a l l y f ixed a t t i t u d e point ing toward the sun. d a t a w i l l then provide time h i s t o r i e s of t he aerodynamic dis turbance t o be considered wi th g r a v i t y g rad ien t dis turbances f o r a n a l y s i s of t he c o n t r o l moment gyro dumping requirements.

These

4 . Detai led free-molecule flow a n a l y s i s i s needed throughout t h e e n t i r e p i t c h and yaw angle-of-attack regions using the f l i g h t conf igura- t i o n t o be used f o r the ATM mission. I f s o l a r panels are to be used, they must be included i n the analysis . Whether o r not the mission is performed i n a docked o r undocked mode w i l l inf luence these r e su l t s .

41

5. Additional l i f e t i m e s t u d i e s may be required, e s p e c i a l l y if the LM with s o l a r panels i s used i n the undocked mode. These s t u d i e s cannot be performed, however, u n t i l the free-molecule drag character- i s t i c s a r e computed f o r t h i s configurat ion.

6 . Extensive dynamics and con t ro l analyses w i l l be required t o properly a s ses s the c a p a b i l i t y of the s p a c e c r a f t t o perform the ATM f i n e a t t i t u d e con t ro l requirements. This is e s p e c i a l l y t r u e i f the mission i s performed i n the docked mode.

7. Many a r e a s of i n t e r e s t t o t h i s l abora to ry have no t been touched upon. example. The MSFC F l i g h t Evaluation Working Group w i l l provide post- f l i g h t engineering eva lua t ion support f o r t he mission. More d e t a i l e d planning of experimental d a t a r e t r i e v a l can be made when the r equ i r e - ments a r e b e t t e r defined.

The proper processing and d i s p o s i t i o n of telemetered da ta a r e an

42

APPENDIX A

Prel iminary Timeline Analysis f o r Crew Transfer Every Twelve Hours

A prel iminary t imel ine is presented here in f o r the ATM mission t o i n v e s t i g a t e s p e c i f i c s o l a r f e a t u r e s in d e t a i l wi th a complement of i n s t r u - ments measuring i n the white l i g h t , u l t r a v i o l e t , extreme u l t r a v i o l e t , and X-ray regions of t he spectrum. would be t o inves t iga t e a c t i v i t y regions on the s o l a r . d i s k or i n the corona t o determine the c h a r a c t e r i s t i c s of s p e c i f i c phenomena. Four experiments a r e considered f o r t h i s mission:

The major emphasis of such experiments

a. U l t r a v i o l e t Spectrometer, Harvard College Observatory, (HCO),

b. U l t r a v i o l e t Spectrograph, Naval Research Laboratory, (NRL).

c. Extreme UV/X-ray Spectroheliographs, Goddard Space F l i g h t Center (GSFC) .

d. White Light Coronagraph, High A l t i t u d e Observatory, (HAO).

The t imel ines r e f l e c t the following assumptions: e

a. Mission dura t ion of 14 days.

b. Launch was se l ec t ed t o be from Cape Kennedy i n the e a r l y morning i n t o a 200 n.m. o r b i t wi th an i n c l i n a t i o n of 29 .5" -

c. The veh ic l e model cons i s t s of the CSM and the LM i n which the te lescopes a r e mounted. The LM is re leased from the CSM during the experiments; the CSM must rendezvous and dock with the LM f o r change of crew, A t o t a l of 1 1 / 2 hours was a l l o t t e d f o r rendezvous, docking and crew t r ans f e r .

d. Two crew members remain i n the CSM while the o the r performs

No as t ronau t w i l l remain i n the LM f o r a period of longer than the experiments i n the IM f o r a 12-hour dura t ion . A l l crew members r o t a t e . 12 hours.

e. Observing requirements f o r t he four s tudy experiments conducted i n the IM a r e presented i n Table 1A. Three modes of experiment observing a r e defined by these requirements.

(1) P a t r o l mode: Experiments i n standby condi t ion wi th course-sun o r i e n t a t i o n , and as t ronaut may monitor s o l a r a c t i v i t y . N o da t a a c q u i s i t i o n performed. This mode is represented i n the t imel ines

43

(2) Standard mode: Scheduled observations of s o l a r regions f o r da t a a c q u i s i t i o n periods of 1 t o 10 minutes.

(3) A c t i v i t y mode: Observations of a c t i v e s o l a r regions f o r da t a a c q u i s i t i o n periods of 20 minutes o r g r e a t e r . This mode is designated i n the t imel ines by the AM i n the upper r i g h t of t he experiment scheduled .

f . An EVA, Extra-Vehicular A c t i v i t y , occurs on the seventh and f i n a l days f o r da t a r e t r i e v a l .

g . Sleep periods precede and follow a LM tour of duty. A nap may occur i n the LM. Astronauts a r e scheduled a t l e a s t seven and one-half hours of s l e e p per day.

Astronauts do no t n e c e s s a r i l y s l e e p simultaneously.

h. There w i l l be two ho t meals of 45 minute du ra t ion each, and one snack of 30 minutes each day. A t r a n s f e r of a food supply i n t o the LM occurs each t h i r d day as snacks may occur i n the LM.

i. Two personal hygiene periods per day f o r each a s t r o n a u t i s assumed.

j . 1 2 hour +1 hour, w i th a t o t a l of 3 checks per day. is designated by CSM.

There w i l l be a CSM system check of 30 minute du ra t ion each A CSM system check

k. The LM r equ i r e s a 10 minute systems check performed s i x times each day. A LM check occurs as each a s t r o n a u t e n t e r s the LM, another during the shutdown procedure following an ope ra t iona l labora- t o ry period. A LM systems check i s designated by LM. ,

1. Thi r ty minutes i s assumed f o r LM checkout and a x i s a l i g n - ment upon enter ing the LM.

m. Each a s t r o n a u t w i l l perform a five-minute s a f e t y check of h i s personal equipment each 13 hours o r l e s s .

The t imelines contain the following information:

a . Mission time i n hours from launch i s marked on top of the t ime 1 ine .

b. C 1 , C2, and C 3 l i n e s r ep resen t t he a c t i v i t i e s of each crew member.

. '

I - . - c. Following the crew a c t i v i t i e s is a row designated "node."

The 'ID" and "A" s i g n i f y the descending nodal c ross ing and ascending nodal crossing, r e spec t ive ly , a t the times shown.

I -

d. This mission is independent of a s t r i c t launch time; however, a r ep resen ta t ive day-night s c a l e is given.

e. The row designated "land" shows when the spacec ra f t is over major land masses and s p e c i f i e s which land mass by the code r e f e r - enced i n the l i s t of sybo l s .

f . Tracking s t a t i o n coverage is shown on the last l i n e . The indiv idua l s t a t i o n s a r e abbreviated and a r e def ined i n the l i s t of symbols.

45

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LIST O F SYMBOLS

Crew m e m b e r 1

Crew m e m b e r 2

Crew m e m b e r 3

Descending node

Ascending node

Means vehic le in sunlight

P e r s o n a l hygiene

Safety package check

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United St at e s

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47

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High Altitude Observa tory

Coddard Space Flight Center

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Naval R e s e a r c h Labora tory

Astronauts go f r o m L,EM t o CSM and vice v e r s a

CSF C experiment operating

HA0 experiment operating

P a t r o l mode:

and astronaut monitoring s o l a r activity.

No da ta activity p e r f o r m e d .

Extravehicular activity

Control moment gyro spin UP

Standby condition with c o u r s e sun or ientat ion

NOTE: Madrid, Canber ra , and Goldstone have 85-foot d i shes and cannot t r a c k in ear th orb i t . t racking s i tes not included h e r e a r e White Sands, P a t r i c k , Eglin, KSC, P t . Arguello, Grand Bahama Island, and Grand Turk Island. F u t u r e updating of t hese t ime l ines will take th i s into account.

They a r e for deep space t racking. Other avai lable

48

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c-1

c-2

c-3

MpERlMENT

NODE

LAND

DAY-NIGEF

TRACKWC

c- 1

c-2

c-3

EXPERIMErn

NODE

ULND

DAY-KIGm

TRACKING

SLFEP

. _. NRL, GSFC, Hco HA0 GSFC -

HA0 I

a2 84 I I I

- I

. DAY 1

A6 00

c-1

c-2

c-3

MPERIMENT

NODE

LAND

DAY-NIGEF

T R A C r n G

c - 1

c-2

c- 3

EXPERIMENT

NODE

LANI)

DAY-NIGFI'

TRACKING

52

I : DAY A

I .

.

~

c- 1

c- 2

c- 3

EWERMENP

?K)DE

LPJYI,

DAY-mGm

mamc

DAY 4

e-1

c-2

c-3

EwERIMElvp

x m UN?J

DAY-XIGBr

TRACWJG

53

DAY I-

C-1

c-2

c-3

ExmRmw

NODE

LAND

DAY-NIGD

TRACKING

c- 1

c-2

c-3

EXPERD4ENT

:!ODE

m m

DAY-,KIG€FI

TRACICING

c-1

c-2

c-3

ExmRmEpp

NODE

LAND

DAY-KIGm

TRACKING

c- 1 c-2

c- 3

E3[PERDEI']T

PTODE

mrn DAY-I<IG€FI

m A C K t N G

6

I 144

I 1140 192 I

SLEEP ___ _____ FER MEAL PH

54

#-

a

c- 1

c-2

c-3

3 x P E m

XJDE

XAm

DAY-NIGBP

TRACKING

DAY -h

55

DAY 1

MEAL

170 172 174

CSM SLEEP

c-1 c-2

c-3

MPERIMENT

NODE

LUm

DAY-NIGT

TRACKING

c- 1

c-2

c- 3

EXPERIMENT

NODE

LAND

DAY-PIGET

TRACKING

G r n - H A 0 E4 IEI 4 IL D A D A D A D I

. DAY -1-

c- 1

c-2

c- 3

EXPERIMENT

NODE

LAND

DAY-NIG,T

TRACKING

c-1

c-2

c- 3

EWERDEW

NODE

LAM)

DAY-NIGHT

TRACIUNG

56

DAY

2u) 212 216.

57

22.2 216 218 220 I I I 1 - ,

/ I g I N p $ M 13 3 ~ TRANSFER MEAL PH SIEEP " - - i CSM a MEAL PIi

222 224 226 228

DAY P

c-1

c-2

c-3

EYJ'ERrnPrr

NODE

L>JD

DAY-KIGT'

TIliiCKIIiC

I 296 I 2?8 I 240

CSM 121 MEAL SLEEP .

58

DAY 246

1 -

*

I

1 -

c- 1 c-2

c-3

mm ::3ilE

LATD

3.4S-TiiIGY2

T I l A l r W J G

DAY 2

c-1

c-2

c-3

5 9

DAY -LL 7a 266

c-2

c-3

MpERlMENT

NODE

LvD

DAY-NIGZ

TRZCKING

c- L

C-2

c-3

E X P E B p E P P

::ow

60

DAY 2

l -

1

I

' -

DAY 2 2 -

c- 1 c-2

c- 3 M P E R m

nom um

DAY-1:IG.W

3 K C i U l ? G

6 1

12 I 3i4 I 316 I

/ & I CSM - n I I 8 TRANSFER J

0

A I M OAOAC'AOA GSFC-HAD C A ' I 181 I @ I - PH - 813 i3 TRANSFER ' MEAL PH SLEEP

930 I 3 7 I 3 F I 336 - V m CSM CHECKOUT

- AND REFaTRY INTO

- ATLANTIC OCEAN

- , I 1 I - A D A D A D A D

62

APPENDIX B

Preliminary Timeline Analysis for Crew Transfer Every Seven Days

The a t t ached t imel ine is f o r use wi th the t e x t of Appendix A. This t imel ine d i f f e r s from the other t imel ine i n the assumption that two as t ronauts may remain i n the LM fo r a period of seven days. This assump- t i o n e l imina tes the need f o r frequent rendezvous, docking, and crew t r a n s f e r shown i n the other t imeline. Other assumptions remain the same, w i th experiment scheduling according t o Table lA shown i n Appendix A.

c

63

DAY P

0 . u 2.1 - -

LAUNCH, ESTABLISH

AND CONFIRM O R B I T ;

- -

I(ENDEZV0US AND DCCKWG

- . -. ~~ _. - D A D A D

c-1

c-2

c-3

m m m m NODE

LvD

DAY-x'IG:pP

TRZCKrNG

SLEEP

SLEEP

I ' DAY I I DAY I 1 DAY I I

64

Y

c- 1

c-2

c-3

EWERIl.E\T

::mE

LATD

24S-?iXB'

TflAcKING

DAY

c-1 c-2

c- 3

= m R m

Born

Ljrm

DAY-AKKXJ?

TRZCIUNG

c- 1

c- 2

c-3

EXPERDLUiT

PJ3DE

LPm

DAY-BXE

l ? 7 A C m G

65

DAY 2

c- 1

c-2

c- 3

MI*ERIMENT

NODE

mm DAY-NIGm

TRACICING

Y

DAY L

c

66

c-1

c-2

C- 3

M F E R m

NODE

LmE

DAY-IXGXT

m c m i c

I I I 120 114 u6 118 I 1 -,, ,

.

.

68

c- 1 c-2

c- 3

EilmIMENT

NODE

mID

DAY-BICm

r n C K I N G

67

DAY 6 144 148

152 156

L

70

c-1

c-2

c- 3 ExFERlMENT

NOD6

LArlD

DAY-NIGIEP

TRACKING

c-1

c-2

c-3

m I M E N T

NOD6

WiD

DAY-NIGIEP

TRACKING

C- L

C-2

c- 3

EXPERIMEIiT

:!ODE

LAND

D A Y - K I G Z

TRACKING

DAY -$-

DAY 2

6

6 9

c-1

c-2

c-3

GcFERlMENT

rim

u.rm

3AY-KIGXT

TRACKING

DAY -6-

DAY 8

c-1 c-2

c- 3

MFERDrnNT

NODE

w m

DAY-JIGm

TRACKING

72

c- L

c-2

c-3

ECPERDG:A

::ODE

w3 DAS-KKT

TRACKUG

DAY IL

c-1

c-2

c- 3

mmmm NODE

WIT

DAY-RICXP

TRACKIIiC

c- L

c-2

c- 3

ECPERINEIJT

.'iODE

71

DAY -1Q 242 244 246

I I I I

.

.

74

c

DAY P

c - 1 c-2

c-3

216 218 2m 222

C- 1

c-2

c-3

FXPERD4WV

!;ODE

W . D

DAY-IXGE

TRACKING

DAY 9,

c- 1

c-2

c- 3

EXFERIMEEPT

NODE

wrm DAY-KIGX?

T R A C r n G

C- 1

c-2

c-3

EXPERIME3T

NODE

w m

DAS-EIGHT

l?UlCKDiG

73

DAY

, - I I I I I I I I D A D A D A n A

4 I

.

76

DAY 2

c -1 c-2

c- 3

ExrERmm

NODE

um DAY-IWXF

TPACKUIC

DAY 2 276 278 280 282

SLEEP I SLEEP I

- _ _ _ ~ . ._-_._ __ . I I

A D A D A A I b I if-- -

NODE

75

REFERENCES

1. "Study of AIM I n t e g r a t i o n i n t o AAL - Preliminary D e f i n i t i o n Study of U t i l i z a t i o n of IM," Report 378C-6, Grunrman Aircraft Engineering Corporation, August 10, 1966, Contract NAS9-4983, Addendum 11.

2. "Apollo Telescope Mount Preliminary P ro jec t Development Plan," MSFC, J u l y 25, 1966.

3. Sentmon, Lee H., "Free Molecule Flaw Theory and Applicat ion t o the Determination of Aerodynamic Forces," Report LMSC-448514, Lockheed Missiles and Space Company, October, 1961.

4. Smith, Robert E., "Space Environment Criteria Guidelines f o r U s e i n Space Vehicle Development," NASA IM X-53273, May 27, 1965.

5. Sterne, T. E.; "Effect of the Rotation of a P lane ta ry Atmosphere Upon t h e Orb i t of a Close S a t e l l i t e , " ARS Journa l , Vol. 29, No. 10, October 1959.

78

D A Y

c- 1 c-2

c- 3

EXPERIMENT

NODE

L?m

D A Y - F I G 3

TRACKIIJG

c- L

C-?

c-3

WERnE;!?

::ODE

DAY 3

c- 1

c-2

c- 3

wmmm NODE

LV$D

DAY-FIGm

m c m c

77

D I S T R I B U T I O N

I INTERNAL

~

D I R - D r . von B r a u n D r . R e e s

I - D I R G e n . 0' C o n n e r

, I R-DIR -

Mr . Weidner D r . M c C a l l

R- RP - D r . Stuhl inger M r . H e l l e r M r . B u c h e r M r . Hudson M r . D o w n e y (3)

R-ME - M r . C r u m p t o n

R-QUAL M r . C l e m e n t s

I- S I A A M r . B e l e w M r . R e i n a r t z M r . Ise (3)

R-P&VE D r . Lucas M r . Palaoro M r . G o e r n e r M r . A b e r g M r . G r u b b s M r . Marmann M r . K e l l e r (5)

R-ASTR D r . Haeussermann M r . Horton M r . Hargrove M r . Lelous Wood M r . Lewis Wood

R-ASTR ( C o n t ' d ) Mr. C o u n t e r Mr. G i l i n o (3) M r . Marrero M r . D i g e s u M r . D u n g a n (3)

R-AERO D r . G e i s s l e r M r . Jean M r . Few D r . H. Krause M r . V a u g h a n M r . M c N a i r M r . H o r n D r . M c D o n o u g h M r . D e a t o n Mr . R y a n M r . Rhe inf u r t h M r . D a h M r . Ballance Mr. Lindberg Mr . H i l l Mr . B a k e r Mr. Thomae Mr. Lavender (5) D r . F. K r a u s e

MS- I P M S - I P L (8) HME-P cc-P EXTERNAL

NASA H e a d q u a r t e r s C o d e M, D r . M u e l l e r C o d e S , D r . N e w e l 1 C o d e SG, M r . M i t c h e l l C o d e SG, M r . Forsythe (3) C o d e ML, Mr. Jones C o d e MLD, M r . D i s h e r C o d e MLA, M r . Taylor C o d e MLA, D r . L u n d h o l m C o d e MLA, Mr. A n d r e w s (3)

I

.

80

APPROVAL NASA X-53500

By Robert E . Lavender

The information i n t h i s r e p o r t has been reviewed f o r s e c u r i t y c l a s s i f i c a t i o n . Defense or Atomic Energy Commission programs has been made by the MSFC Securi ty C l a s s i f i c a t i o n Of f i ce r . This r e p o r t , i n i t s e n t i r e t y , has been determined t o be u n c l a s s i f i e d .

Review of any information concerning Department of

This document has a l s o been reviewed and approved f o r technical accuracy.

E. D. Ge i s s l e r Director , Aero-As trodynamics Laboratory

CONCURRENCE :

B kbZC! &wd bwH. J. Horn U

Chief , Dynamics & F1 i g h t Mechanics Divis ion

M i e f F1 i g h t Test Analysis Divis ion

Chief Aerodynamics Divis ion 79

EXTERN

Manned

DISTRIBUTION (Continued)

L (Cont'd)

Spacecraft Center

Code ET23, M r . R. Davidson Code RL, Mr. W. Davidson

Houston, Texas

Goddard Space Flight Center Greenbelt, Md.

Code 613, Dr. Milligan

Scientif ic and Technical Information Facility (25) P. 0. Box 5700 Bethesda, Md. Attn: NASA Representative (S-AK/RKT)

81

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