apollo-soyuz pamphlet no. 8 zero-g technology

8/8/2019 Apollo-Soyuz Pamphlet No. 8 Zero-g Technology

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Apollo-SoyuzPamphlet No. 8:Zero-GTechnology

iNAL PI QUALITY

(NASA-EP-140) APOLLO-SOYOZ PAMPHLET NO. 8: N78-27153ZERO-G TECHNOLOGY (National Aeronautics andSpace Administration) 68 p MF A01; SOD HCset of 9 volumes CSCL 22A OnclasG3/12 24995

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Apollo-SoyuzExperimentsSpace

This is one of a series of ninecurriculum-related pamphletsfor Teachers and Studentsof Space ScienceTitles in this series ofpamphlets include:EP-133 Apol lo-Soyuz Pamphlet No. 1: The FlightEP-134 Apol lo-Soyuz Pamphlet No. 2: X -Rays, Gam ma-RaysEP-135 Apol lo-Soyuz Pam phlet No. 3: Sun, Stars, In BetweenEP-136 Apol lo-Soyuz Pamphlet No. 4: Gravitational FieldEP-137 Apo l lo-Soyuz Pam phlet No. 5: The E arth from O rbitEP-138 Apollo-Soyuz Pamphlet No. 6: Cosmic Ray DosageEP-139 Apollo-S oyu z Pamph let No. 7: Biology in Zero-GEP-140 Apol lo-Soyuz Pamphlet No. 8: Zero-G Tech nologyEP-141 Apo l lo-Soyu z Pam phlet No. 9: General Sc ience

On The Cover Four-Second Grow th Layers in a Germanium CrystalGrown in Zero-g. Magnified x 50


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Apollo-SoyuzPamphlet No. 8:Zero-G TechnologyPrepared by Lou Will iams Page and Thornton Page FromInvestigators' Repor ts of Exp er imenta l Resu l tsand Withthe Help of Advising Tea chers

IH f t lM U , C5ITA1ISC O L O R lussnomeii*

IWNSANational Ae ronau t ics andSpace Administ ra t ionWashington, D.C. 20546October 1977


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For sale by the Superintendent of Documents,U.S. Government Printing Office, Washington, D.C. 20402(9-Part Set; Sold in Sets Only)Stock Number 033-800-00688-8


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Preface

T he Apo llo-S oyuz Test Project (AS T P), w hich f lew in Jul y 1975, arousedconsiderable public interes t; f i rs t , because the space r ivals of the late 1950'sand 1960's w ere w orking together in a joint endeavor, an d second, becausetheir mutu al e f f or ts inc luded developing a space res cue s ys tem. T he AST Palso included signif icant scientif ic experiments , the results of which can beused in teaching biology, physics , and mathematics in schools and colleges.

This series of pamphlets discussing the Apollo-Soyuz mission and experi-rrfents is a set of c urr i c u lum suppl em ents designed for teachers , supervisors ,cu r r icu lu m specialists, and textbook writers as w el l as for the genera l pub l ic .N e i t h e r textbooks nor courses of s tudy , these pam phlets a re inten ded toprovide a r ich source of ideas , examples of the scientif ic method, per tinentreferences to s tandard textbook s, and clear descriptions of space experime nts .In a sense, the y may be regarded as a pioneering form of teaching aid. Seldomhas there been such a for thright ef for t to provide, directly to teachers ,c u r r i c u l u m - r e l e v a n t reports of curren t s c ien t i f ic res earch. H igh s choolteachers who reviewed the texts suggested that advanced s tudents who areinteres ted mig ht be assigned to s tudy one pam phlet and report on i t to the restof the class. A f te r class discussion, s tud ents mig ht be assigned (wit hou taccess to the pamphlet) one or more of the "Questions for Discussion" forforma l or informal answers , thus s tressing the application of what waspreviously covered in the p a m p h l e t s .

T he au thors o f thes e pamphle ts are D r . Lou Wil l iam s Page, a geologist, andDr. Thornton Page, an as tronomer. Both have taught science at severaluniversi t ies and have published 14 books on science for schools, colleges, andthe general reader , i n c l u d i n g a recent one on space science.

Technical assis tance to the Pages was provided by the Apollo-SoyuzP rogram S cien t is t , D r . R. T homas G iu l i , and by Richard R. Bal dw in ,W . Wils on Lauderdale , an d S u s a n N . M o n t g o m e ry , m e m b e r s o f th e group att he N A S A L yn do n B . Johnson Space Center in H ous ton w h ich organized t h esc ien t i s t s ' par t ic ipa t ion in the A S T P an d publ is hed t h e i r reports of e x p e r i m e n -t a l res u l ts .

Selected teachers from high schools and universi t ies t h r o u g h o u t the U n i t e dSta tes review ed t he p a m p h l e t s in d r a f t f orm. T hey s ugges ted changes inw o r d i n g , the addi t ion of a glossary of terms u n f ami l i a r t o s t u d e n t s , andi mprove me nts i n diagrams . A list of the teachers and of the scient i f ic inves-t ig a to r s w ho review ed t he t e x t s f or accuracy f o l low s th is P ref ace.T h i s set of A p o l l o - S o y u z p a m p h l e t s w as ini t ia ted an d coordinated by Dr.Frederick B. T ut t l e , Director of Educ atio nal Programs, and was supported bythe N A S A A p o l l o - S o y u z P r o g r a m O f f i c e , by Leland J. Cas ey , Aeros paceE n g in eer fo r A S T P , an d b y W i l l i a m D . N i x o n , E d u c a t i o n a l P r o g r a m sOff icer , a l l of N A S A H e a d q u a r t e r s in W a s h i n g t o n , D . C .

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Ap p r ec ia t io n is expressed to the scientif ic investigators and teachers w horeviewed the draf t copies; to the N A S A specialis ts who provided diagramsand photographs; and to J. K. H olcomb, H eadquar ters D irec tor of A S T Poperations , and C h e s t e r M . Lee, ASTP Program Director at H eadquar ters ,whose interes t in th is educat ional endeavor made th is pub l ica t ion possible.

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TeachersAnd Scientific InvestigatorsWho Reviewed the Text

Harold L. Adair, Oak Ridge National Laboratory, Oak Ridge, T enn.Lynet te Aey,N o r w i c h F r e e A c a d e m y , N o r w i c h , C o n n .J. V e r n o n B a i l e y , N A S A L y n d o n B . J ohns on Space Center , H ous ton , Tex.Stuar t Bow yer , U nivers ity o f Ca l i f ornia a t Berkeley , Berkeley , C a l i f .Bi l l Wes ley Brow n, Cal i f ornia S ta te U nivers i ty a t C hico , Chico , C a l i f .Ronald J. Bruno, Creighton P repara tory School , O maha, Nebr .T . F . Budinger , Un ivers ity of Cal i f ornia at B e r k e l e y , B e r k e l e y, C a l i f .Robert F. Collins , Western States Chiropractic College, Portland, Oreg.B. Sue Cris w el l , Bay lor Co l lege of M e d i ci n e , H o u s t on , Tex.T . M . D o n a h u e , U n i v e rs i t y of M i ch i ga n , A nn A r bo r, M i c h .D avid W . Eckert , G reater Latrobe S enior H igh School, Latrobe, Pa.Lyle N . Edge, Blanco High School , B l anco , Tex.V ictor B . Eichler , Wichi ta S ta te U nivers i ty , W ichi ta , Kans .F arouk El-Baz , Sm i ths onian I ns t i tu t ion , Was hing ton , D.C.D . J erome F is her, E mer i tus , U niversi ty of Chicago , P hoenix , Ar iz .R . T . G i u l i , N A S A L y n d o n B . J ohns on Space C enter , H ous ton , Tex.M . D . Grossi, Sm iths onian A s trophysica l O bs ervatory , C ambridge , M as s .W e n d y H i n d i n , N o rt h S h or e H e b r e w A c a d e m y , G re a t N e c k , N.Y.T i m C . I ngo lds by , W es tside H igh School , O maha, N ebr .Robert H . J o h n s , A c a d e m y of the New C h u rc h , B ry n A t h y n , P a.D. J . Larson, Jr., G rum man A eros pace , B ethpage, N.Y.M . D . Lind , Rockw el l I n terna t ional Science C enter , T hous and O aks , Ca l i f .R . N . L i t t l e , U n i v e r s it y o f T e x as , A u s t i n ,Tex.S a ra h M a n l y , W a d e H a m p t o n H i g h S c h oo l , G r e e n v i l l e , S.C.K a t h e ri n e M a y s , B ay C i t y I ndependent School D is t r ic t , B ay C i t y ,Tex.J a n e M . O p p e n h e im e r , B r y n M a w r College, B r y n M a w r , P a .T . J . P e p i n , U n i v e r si t y of W y o m i n g , L a r a m i e , Wyo.H . W . S c h e l d , N A S A L y n d o n B . J o h n s o n S p a ce C e n t e r, H o u s t o n , Tex.S e t h S hul ma n, Naval Res earch Labora tory , Was hing to n , D.C.J ames W. S kehan , Bos ton C ol lege , Wes ton , M as s .B . T . S l a t e r, Jr., T e x a s E d u c a t i o n A g e n c y , A u s t i n , Tex.Robert S . S n y d e r, N A S A G e org e C . M a r sh a l l S p a c e F l i g h t C e n t e r , H u n t s v i l l e , Ala.Jacqueline D. Spears , Port Jefferson H igh School , P or t Jefferson S t a t i o n , N.Y.Robert L . S tew ar t , M ont ice l lo H i g h S c h o o l , M o n t i c el l o , N.Y.A l e t h a S t o n e , F u l m o r e J u n i o r H i g h S c h o ol , A u s t i n , Tex.G . R . T a y l o r , N A S A L y n d o n B . J o h n so n S p a ce C e n t e r , H o u s t o n , Tex.Jacob I . T r o m b k a , N A S A R o b e r t H . G oddard S pace F l igh t C enter , G reenbel t , M d .F . O . V o n b u n , N A S A R o b e rt H . G o dd ar d S p ac e F l i gh t C e n t e r , G r e e n b e l t , M d .D o u g l a s W i n k l e r , W a d e H a m p t o n H i g h S c h o o l , G r e e n v i l l e , S.C.


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Contents

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Section 1 Introduction: The. Valu e of Several .Space Technotogies 1A. "Housekeeping" technoJogy = . . ' . ; . J_.. . , - . ' . ; ; , . . ; , 2B. Biological and Medical Technology . ' . " ' . . * . ' . . . . . " 2C. C h em ic al T ec hno lo gy . . . . . . . . . . T ? 3D. Metallurgical T-eQhnpipgy ......".-...' ,.-.,-?,...:. 3E. Power Technology in'Spaice ~ ~ . . '.. ? V! '"'..". 4

Section 2 The Behavior of Liquids in Zero-g 7A. The Chemical-Foam Demonstrat ion 7B. The Liquid-Spreading Demonstration 9C. The Wick D emo nstrat ion 10D. Questions for Discussion (Foam, W ett ing, Wicks) 11

Section 3 High-Temperature Processing of Metals and Salts in Zero-g 13A. The MA-010 Mult ipurpose Furnace 13B. Lead-Zinc and Aluminum-Antimony Al loys Produced inthe MA-044 Exp eriment 16C. Melt ing of Aluminum, Tungsten, Germanium, and Sil iconin Zero-g 21D. Diffusion of Gold Into Molten Lead 22E. Magnetic Al loys Formed in Zero-g 23F. Transp arent Fibers From a Eutectic 26G. Questions fo r Discussion (Heat Transpo rt, Te mp erature, Al loys,Eutectics) 30

Section 4 Growing Large, Nearly Perfect Crystals in Zero-g 33A. Growth of Large Germanium Crystals 33B. Growth of Crystals From Vapor 37C. Growth of Crystals From Solution 40D. Questions fo r Discussion (Cleavage Planes,Crystal Growth 45Appendix A Discussion Topics (Answers to Questions) 46Appendix B SI Units and Powers of 10 50Appendix C Glossary 53Appendix D Further Reading 59

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Figures

Figure 2.1 Chemical Reaction Speed in Foam 82.2 Liquid Spreading in Zero-g 92.3 Wick Act ion in Zero-g 10

Figure 3.1 MA-010 Mult ipurpose Electric Furnace 133.2 Diagram of Furnace Control System 153.3 Diagram of MA -044 Ca rtridge for Al loys 173.4 Temperature Versus Time in MA-044 Cart r idges 183.5 Photographs of Lead-Zinc Ingots in Zero-g and One-g 193.6 M icrostructure of Al-S b Al loy Formed in Zero -g and One-g 203.7 Temperature Versus Time in the Soviet MaterialsMelt ing Experiment 213.8 Diagram of MA-07 0 Cartridge for Ma gnetic Al loys 243.9 Fibers in Magnetic Eutect ic From Experiment MA-070 253.10 Diagram of MA-131 Cartridge for NaCI-LiF Eutectic 263.11 LiF Fibers at the Unmelted Salt Boundary in Experiment MA-131 273.12 Parallel LiF Fibers Formed in Zero-g an d One-g 283.13 Cross Sections of Fibers in NaCI-LiF Eutec t ic 29

Figure 4.1 Diagram of MA-060 Cart r idge fo r Germanium Crystal Growth 354.2 Interface Dem arcat ion Lines in Germ anium Crystal Grownin Zero-g 364.3 Rate of Germanium Crystal Growth in Zero-g 374.4 GeSe Crystals Formed From Vapor in a Quartz Tube 394.5 GeSe Crystals Formed in One-g and in Zero-g 404.6 Diagram of the MA -028 Re actor for Forming Crysta lsin Solutions 414.7 The Six MA -028 Rea ctors for Apo l lo-Soyuz 424.8 Crystals of Calcium Tartrate and Calcite Grown inExperiment MA-028 44

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1 Introduction

The Value of Several Space TechnologiesA f t e r 4 years of preparation by the U.S. Nat io n a l Aer o n au t ics an d Sp aceA d m i n i s t r a t i o n ( N A S A ) a n d t h e U . S . S . R . A c a de m y of Sci en ces , t h e A p o l l oan d So y u z sp acecr a f t w er e lau n ch ed o n J u l y 1 5 , 1 9 7 5 . Two d ay s la te r a t 16:09Gr een wich m ean t im e o n J u l y 17, af ter Apoll o ma neuve red in to the same orbitas S o y u z , the tw o spacecraf t were docked. T he as t r o n au ts and co sm o n au tsth en me t for the f irst in te r n a t io n a l h an d sh ak e in space , an d each crew enter-tained the o ther crew (onea t a t im e) a t a m eal o f ty p ica l A m er ican o r R u ssianfood. T h e s e activi t ies and the physics of reaction motors , orbi ts around theEar th , and weight lessness (zero-g) are described more f u l l y in Pam p h le t I ,"The Sp acecr a f t , Th ei r Orbits , an d Docking" ( E P- 1 33) .

T h i r t y - f o u r ex p er im en ts wer e p er fo r m ed wh i le Ap o l lo and So y u z wer e inorbi t : 23 b y as t r o n au ts , 6 b y co sm o n au ts , an d 5 jo in t l y . T h e s e ex p er im en ts inspace were selected from 1 61 proposals from scientists in n i n e di f ferentcpun t r i es . Th ey are listed by n u m b er in Pamphlet I and groups of two ormore ar e described in detail in Pamphlets I I through IX (EP-134 throughEP-141, respectively) . Each experiment w as directed by a Principal Inves-t igator , assisted by sev er a l C o - In v es t ig a to r s , a nd the detai led scient i f ic r e s u l t shave been published by N A S A in two reports: t he Ap o l lo - So y u z Tes t Pr o jec tP r e l im i n a ry S c i en ce R ep or t ( N A S A T M X - 5 8 1 7 3 ) and the A p o l l o - S o y u z TestP ro je ct S u m m a r y S c i e n ce R e p or t ( N A S A S P - 4 1 2 ) . T h e s i m p l i f i e d a c c o u n t sgiven in th ese p am p h le ts h av e b een r ev iewed by the Pr in c ipa l I n v es t ig a to r s orone of the Co - In v es t ig a to r s .

T o m o st people , space technology means t he r o ck e ts , th r u s te r s , and co n tr o lj e t s and the general s tructure of spacecraf t described in P a m p h l e t I . A c t u a l l y ,sp ace tech n o lo g y a lso in c l u d es th e E ar th o b ser v a t io n s ( g r av i ty an o m al ies ,surface f e a t u r e s , and a tm o sp h er ic f ea t u r es ) described in P a m p h l e t s IV a nd V,the o b ser v a t io n s of n ear - E ar th r ad ia t io n d e ta i led in P a m p h l e t VI, and some ofthe biological and m ed ica l tech n iq u es cov ered in Pam p h le t VI I . Fu tu r e sp acetech n o lo g y w i l l in c lu d e v ar io u s su r v ey s of the E ar th ; p h o to g r ap h y and m a p -pi ng o f the surface; mo n i t o r i n g of the atmosphere and i ts aero so ls ; m o n i to r in gof cosmic rays, w hic h are af fected b y th e E ar th ' s m ag n e t ic f i e l d ; and elec-trophoresis s eparatio ns in zero-g. Several new te chn iqu es are expected to bedeveloped f or c h e m i s t r y , m e t a l l u r g y , and solar power in space. There are atleast f ive dif ferent space technologies: "housekeeping," b io lo g ica l an d m ed -ica l , ch em ica l , m e ta l lu r g ica l , and power. Three of th ese tech n o lo g ies areco v ered in Sec t io n s 2 , 3 , an d 4 o f th is p am p h le t .


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A "Housekeeping" TechnologyDuri ng a nd a f te r the l a unc h o f A pol lo , o r S oyuz , or a ny o the r spa ce c ra f t ,react ion m otors are used to push and turn the vehic le (see Pamphl e t I ) . This isa basic technology largely developed by the Germans for long-range m il i t a r ymissi les in World War I I . When the spacecraf t is in orbi t and no reac t ionmotors are being f i red, i t is in the condi t io n of f ree f a l l or zero-g,1 an dev er y t h i n g inside the spacecraf t is weight less. This weight less condi t ionrequires specia l design technology, such as te ther l ines , handholds , andVelcro anchors t o keep too ls an d a s t rona u ts at the places where they areneeded. O ne part icular problem is the h a n d l i n g of l iquids (such as water) intanks. In zero-g, w a t e r does not s tay a t the "bottom" of a pa r t ly f i l l ed t a n k .For the A pol lo-Soyuz mi ss i on , se ve ra l "science de mons t ra t i ons" on theh an d l i n g of l iquids in zero-g were planned by R. S. Snyder and f ive C o-Inve s t i ga tors f rom t he N A S A G e o r g e C . M a rsha l l Spa ce F l i gh t C e n te r( M S F C ) i n H u n t s v i l l e , A l a b am a . Th ese de mons t ra t i ons a re described inSection 2.

Biological and Medical TechnologyScientis ts specula te tha t some biolog ica l processes may tak e place fas ter inzero-g than in one-g on Ea r th (a l though one f u n g u s carried on A p o l l o - S o y u zgrew slower; se e P a mphle t VII). I f so , there may be a new t e c hnology toproduce vaccines and other medicines more ef f i c i en t ly i n spa c e . On A pol lo-S o y u z , the process of separa t ing ce l ls by elec trophoresis w as shown to bemore precise in zero-g than in one-g on the ground (Pamphle t VII) . Thisdiscovery could lead to a t leas t one import ant space te chn iqu e tha t wou ldaccelera te the p roduction of u rok inase for the vic t ims of heart disease an dothe r c ondi t i ons .

A nothe r spe c u la t i on is t h a t t h e h i g h e r i n t e ns i t y o f cosmic rays an d h i g h -energy protons a t a l t i tu des from 3 00 to 3000 ki lome t e rs (P a mp hle t s I I and VI )mi g h t be used to prepare muta t ions of l iv ing c e l l s f o u n d on Ea r th . T hi s c ou ldlead to a new t e c hnology of "breeding" c e l l s tha t w e need and of discoveringnew breeds of bac teria tha t we mus t defend against wh en they appear onEarth. (A similar technology has a lready been developed in ground-basedlaboratories.)

"'Project Physics," second e d i t i o n , H o l t , R i n e h a r t an d W i n s t o n , 1975, Sees. 4.6, 4.7;" P h y s i c a l Science S t u d y C o m m i t t e e " ( P S S C ) , f o u r t h e d i t i o n , D . C . H e a t h , 1976,Sees. 12-6,1 2 - 1 2 .


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The metal lurgical experiments on Apollo-Soyuz were based on a special lydesigned electric furnace located in the D o c k in g M o d u l e ( D M ) . I t could heatsamples to as high as 1423 K (1150 C) , as described in Sect ion 3. Sixexperiments on spheres , al loys , and eutectics , as well as two of the threeexper iments on crystal growth, were done in th is f urnace.

Exper iment M A-010 , the M ultipurpose Electric Furnace f ac i l i t y , de-veloped a t M SF C under the s upervision o f A . Boese, w as highl y succes s f u l .Exper iment M A -044 , M onotec t ic and Syntectic Alloys , showed that theu n i f o r mi t y of a l u m i n u m - a n t i m o n y (A l-Sb) a l loys produced in zero-g w asm u c h bet ter than the u n i f o r mi t y of those produced in one-g on Ear th . T h e t w oP rincipal I nves t iga tors w ere C . Y . Ang and L. L. Lacy o f M SF C .

E x pe ri m en t M A - I S O , M u l ti pl e Material M el t ing , w as a jo in t exper imentdesigned by I . I vanov of the Sovie t I n s t i t u t e f or M e t a l lu r gy in M o s co w . H ewas assis ted by several Russian and two American Co-Investigators . Thezero-g formation of a l u m i n u m s p h e re s an d two al loys ( a l u m i n u m - t u n g s t e nan d g e r m a n i u m - s i l i c o n ) w as compared w i t h f o r m a t i o n in one-g on Ear th .Experiment M A -041, Surface-Tension-Induced C onvec tion, measured t hesm al l a m o u n t of mater ia l f low produced by surface tension in m o l t e n l e ad an dgold. T he P r incipa l I nves t iga tor w as R. E. Reed o f O ak Ridge Nat ionalLaboratory in Tennessee.Experiment M A -070, Zero-g Processing of Magnets, w as supervised byD. J. Larson, J r . , of Grumman Aerospace Corporation in New York. T heex p er im en t showed t h a t bet ter magnet ic eu tec t ics of m a n g a n e s e - b i s m u t h canbe produced in zero-g t h an in one-g.

E x pe ri m en t M A - I 3 1 , Halide Eutec t ic G row th , s how ed t h a t l o n g , t h i nfibers of l i t h i u m f lu oride (LiF) form in s o d iu m c h l o r i d e (N a C l ) w h e n the twosa l t s are melted togeth er and cooled rapidl y, s tar ting at one end . The PrincipalIn v es t ig a to r w as A. S . Yue o f the U n i v er si t y o f C a l i f o r n i a a t L o s A n g e l e s( U C L A ) ; h e was assisted b y two Co-I nves t iga tors .

p Power Technology in SpaceA l t h o u g h the A p o l l o - S o y u z e x p e r i m e n t s did not relate to solar power, itshould be noted that power technology is expected to develop rapid ly in the1980's. T he w or ld w ide pow er s hor tage has increased the impor tance of solarpower. Professor Gerard O'Neil l of Princeton U n i v er s i t y has suggested thatspace colonies should be b u i l t w here orbi t ing s o lar-pow er s ta t ions cou ld bema nufa c ture d more cheap ly and more q u i ck l y t h an on Ear th . Some o f th em a n y ar t ic les on space colonies an d o r b i t i n g s o lar -pow er s ta t ions are re-viewed in a book en t i t led "Space Science and A s t r o no m y " ( M a c m i l l a n C o . ,1976). The proposed solar-power s ta t ions w o uld be huge co l lec tors (40 to 50


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k i lo m eter s across) in geosynchronous orbit 36 000 kilometers above theEquator . In this kind of orbi t , the sta t ions woul d a lways be over the same pointon Ear th an d could beam 10 or 20 th o u san d m eg awat ts of power by micro-waves (very short radio waves) to a ground receiving station in the so u th wes t -er n U n i t ed S t a t e s or elsewhere at low la t i tu d e .T h e su n l ig h t m ig h t be conver ted t o electr ici ty w i t h s i l ico n ce l l s th a t NA S Adeveloped in the 1960's for the solar-power panels on spacecraft. An o th erpossibi l i ty is to use the sunlight to heat a gas that would dr ive turboelectr icgenerators as in a regular electric powerplant on E ar th . E i th er way , a newtechnol ogy mus t be developed to handle such high electr ical power o u t p u t onan orbi ter and to conver t i t to microwaves aimed at the ground receiver .


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2 The Behavior of Liquidsin Zero-g

A

T he behavior of l iqu ids anyw here depends on their boundary surfacesthatis , wh er e th ey come in contact wit h so lids or gases. A t t he boundary of a l iq u idan d a sol id, two kinds of force are in com peti t ion: cohesive force p u l l in g thel iquid molecules together and adhesive force pul l in g the l iquid m oleculestoward the so lid . I f the adhesive force is larger, the l iquid wil l wet the so lidsmoothly. I f the cohesive force is larger, sm al l am o u n ts o f l iq u id w i l l formli t t le droplets on the so lid surface, l ike water on greasy hands. On Ear th , o fcourse, th er e i s a th i r d fo r ce g r av i ty th a t p u l l s th e l iq u id d o wn war d .Gra vi ty pulls the water down into the bot tom of a cup and keeps i t fromw e t t i n g far up the sides. Oil , however , has a large adhesive force with metalan d w i l l stay spread all over a metal surface in one-g.Detergents , l ike soap, change the surface of l iquids such as water , so thatbubble s on the surface of soapy wat er last for several min ut es in one-g.Gravity f i n a l l y p u l l s th e wa ter d o wn th e sides of the bubbles, and the bubblesget so thin that they break (because of the motions of the water molecules) .L i qui ds in bubbl es or foam are import ant in several w ays: they are used inf ight ing f ires, in m ak in g l ig h tw eig h t p las t ics an d fo am r u b b er , and in speed-in g up some chemical reactions between gases an d l iq u id s .

Wicks move l iquids against gravi ty when there is a s trong adhesive forcebetween the l iqu id and the so lid f ibers in the wick. For instance, the w ick of acandle pul l s molten w ax up about 5 m il l im eters , where i t burns easi ly in thecandle f lame. A towel acts as a wick when i t l i f ts water off a surface to dry it.I n zero-g , wicks can be used instead of pum ps to transpor t l iquids from tanksto wherever they are needed in a spacecraft.

Space engineers hav e learned to handle several l iquids in zero-gw ater ,propel lant f u e l , l iq u id o x y g en , o i l , an d waste. They have d i f f i c u l t y in measur-in g adhesive and cohesive forces on Earth because the one-g gravity forceinterferes. W h en th ey t ry to measure the chemical reaction t ime in a fo am inone-g , f or e x a m p l e , t he foam col lapses af ter a few m in u tes . Th er e fo r e ,d em o n st r a t io n s o f ch em ica l fo a m in g , l iqu id spreading on a solid surface, andl iqu id m o t i o n in a wick were photographed an d t i m e d by the as t r o n au ts onA p o l l o - S o y u z .

The Chemical-Foam DemonstrationThree che mic als were added to water in a small p last ic bot t le , wh ich was thencorked and shaken vigorously to make a foam. Thymol b lue, a detector thattu rns p in k in an acid so lu tion ( l ike l i t m u s paper), had been added to the w a t e r .The chemicals were sodium su l f i t e ( N a S O 3) , sodium hydrogen su l f i t e( N a H S O 3 ) , an d fo r m ald eh y d e ( H C H O) . Th r ee r eac t ion s to o k place , y i e l d i n gS O 3 ~ ~ io n s wh ich tu r n ed the fo am pink in less than 2 0 seconds and the rest of


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the solution pink in about 1 minu te (F ig. 2 .1 ) . T his demons tra t ion s how s tha tin zero-g a comple x chem ical reaction can be speeded up in foam . The samereaction would also be speeded up in one-g i f the f o a m w o u l d l a s t , but itcollapses in less than 20 seconds.

Figure 2.1 Chemical reaction speed in foam. Just after mixing and shaking the threechemicals in water, the foam began turning pink (top photograph). After 60seconds, the reaction was completeand the foam was dark red (bottom photo-graph).

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The Liquid-Spreading DemonstrationIn zero-g, a small amou nt of l iquid wets more than the bottom of a cup; i t w etsthe entire cup. This w as demons tra ted on A pol lo-Soyuz by s quirt ing a s mal lam o u n t o f blue-colored oil into the bot tom of a cubica l p las t ic cu p. Th e o i lq u ick ly spread over the bottom and then up the s ides. The adhesive forcebetw een oil and plas tic is s tronger tha n the cohesive force o f th e oi l . B lue oilcollected in the corners of the cubical cup because the sharp corner al lowedthe cohesive force t o w ork more near ly w i t h t he adhes ive f orce there(Fig. 2.2). When red-colored water w as later added on top of the oil, it f ormedround drops because the adhesive force between water and oil is m uc h smal lerthan the cohesive force of water. The speed of oi l spreading in zero-g wasmeasured f rom motion p ic tures taken by the as t ronauts , and th is zero-gsurface tens ion helps us to u n d e r s t a n d t he l iquid spreading of s o lder , mol tenm eta ls , an d insecticides in one-g on Ear th .

Liquid spreading in zero-g. Blue-colored oil rapidly spreads up the sides of the Figure 2.2cubical plastic cup. (This photograph was taken during a zero-g airplane flight,not on Apollo-Soyuz.)

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c The Wick DemonstrationWic ks are very ef f ic ient in zero-g because the f luid being "pulled up" has now e i g h t . Four wicks, each 1 0 cen t im eter s lo n g and 1 centimeter wide, wereheld in a frame so th at each w ick dipped into a plast ic cup at one end. T hree ofthe wick s were made of s tain less-steel wire in terwoven in diff erent ways. T hef o u r t h wick was made of nylon. Blue-colored soapy water and b lue-coloredsilicone oil were squirted into the cu p s , and the motion of each f lu i d up thewick s w as t im ed . Bo th the oi l and the water moved up the wick s m u ch fas te rtha n expected , and the oi l moved faster than the water (Fig. 2.3). T i m i n gshowed that the stain less-steel wick with the Plain Dutch weave was mostef f icient in zero-g.

Figure 2.3 Wick action in zero-g. Three of the wicks can be seen between columns of thesupporting frame. When colored water and oil were squirted into the cups atthe lower ends of the wicks, the motion of the liquids up the wicks waswatched andtimed. (This photograph was taken during a zero-g airplane flight,not on Apollo-Soyuz.)

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Questions for Discussion(Foam, W ett in g , W ick s)1. I t has been suggested that s tyrofoam and o ther hardened p lastic foam s

could be strengthened by adding strong metal f ibers to the foam before itsol idi f ied. Co m p ar e how such a process wo u ld wo r k in zero-g an d on e-g.

2. Wha t happens to the oil when i t gets to the top of the open-cube cup inzero-g?

3. Wh at forces account for oi l movin g faster t h an water a long a wick inzero-g?

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3 High-TemperatureProcessing of Metals andSalts in Zero-gA n elect ric furnac e designed and b u i l t by Westinghouse had been used to mel tm e t a l s on the lo n g Sk y lab m iss io n s in 1973-74. T he M A - 0 1 0 f u r n a ce u se d onApollo-Soyuz was basical ly the same as the Skylab furnace, w i t h improve-m e n t s t o shorten the heating and cooling t imes. T he m ajo r r eq u i r em en t w asf l e x ib i l i t y so that the furnace could be used for seven di f ferent ex p er im en ts ,five of w h i c h are described in th is sect ion.

A The MA-010 Multipurpose FurnaceThe mater ia ls to be heated in the furnace were enclosed in standard-sizecar tr idges, each 2.1 centimet ers in diamet er and 20.5 cent imet ers long. Th reesuch cartridges could be f i t ted in s id e th e v acu u m - t ig h t f u r n ace case sh o wn o nth e right side of Figure 3.1 . El ectr ic current thro ugh resistors w as used to heat

APOLIOSOYUZMA OIO FXPFRIMINT

The MA-010 multipurpose electric furnace. The furnace is the cylinder on theright, about 22 centimeters high and 9 centimeters indiameter. There arethreeopenings in the top for inserting the three cartridges to be heated. The centerbox contained helium and the controls for releasing small amounts into the fur-nace for cooling. Thecontrol box on the left hasdials andswitchesto set auto-matic heatup and cooldown rates and soak times.

Figure 3.1

1 3IN G P A G E B LA N K N OT


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the ma te r i a l s in each cartridge. T he c urre n t w as control led by the box s h o w non the le f t side of F i gure 3 .1 . T he t e mpe ra ture c ou ld be made to rise as rapidlyas 400 K / h r (400 C / h r ) or it c o u l d b e h e l d c o n s t a n t . C o o l i n g w asaccomplished by t u r n i n g of f the e lec tric current an d i nj e c t i ng he l i um gas intothe furna c e . T h i s al lowed heat to escape f rom the hot c a r t r i dge s , whi c h hadbeen wel l insula ted in vacu um during the period of high tempera t ure . T hetempera ture dropped f rom i t s ma xi m um of 14 2 3 K (11 50 C ) to 4 2 3 K (150C) in about 3 h o u r s . ( W i t h o u t t he h e l i u m c o n d u c t i o n of he a t , the cooldownwou ld have taken 20 hours.) The mid dle box in Figure 3.1 contain ed thehe l i um a nd thre e va l ve s for c on t ro l l i ng the sma l l a mount (0 .16 c ubi c c e n t i m e -ter) released int o t he furna c e case. T he e nt i re e xpe r i me nt w as fas tened to theinside wal l o f th e D o c ki ng M o d u l e ( D M ; see P a m p h l e t I ).

T o ge t ra p i d he a t i ng w i t h m i n i m u m h e a t loss, W e st i nghouse use d n i c ke lwires around graphi te in c onta c t w it h th e "hot end" o f th e cartridges to behe a te d . T he n i c ke l he a t i ng wi re s we re c overe d wi th a lu mi n a (A 1 2O 3) c e me nt .Every possible h ea t loss from each in sula t ed cartridge w as reduced so t h a tonly 1 0 wa t t s of the 205 -wat t heater power were lost through heat conduction.T hi s he a t - loss re duc t i on w as possible because t he heated cartridges wereisola ted in a vacuum in the furnace case. Before the hea ter was s tar ted, thesea led furnace case w as e va c ua te d through a t u b e to the v a c u u m of spaceoutside t h e D M .

A sc he ma t i c d i agra m of the M A -010 furna c e c ont ro l box i s shown i n F i gure3.2. T h e di a gra m shows tha t t h e a s t rona u t or cosmonaut could se lec t t h etempera ture requested by the Principa l Invest iga tor for each furnace experi-me nt . T he te mpe ra ture w a s the n a u toma t i c a l ly c on t ro l le d by two the r-mocouples (e lec tric thermometers) , one at the "hot end" o f th e e xpe r i me ntcartridge (bot tom of the case in Fig. 3.1) and one a t the cool e nd. (B othtempera tures were recorded as a f unc t ion of t i m e . ) T he "soak period" o f 1 to6 hours wa s the t i me dur i ng whi c h the furna ce re ma i ne d a t ma x i m um te mpe ra -ture to homoge ni z e t he materia l . T he c oo ldown ra te , whi c h c ont ro l le d t het i m i n g a n d t h e a m o u n t o f h e l i u m c o o l i n g , w a s a l so se t . From t h et e mpe ra ture -ve rsus- t i me c urve s fo r th e two e nds of each experiment car-t r i dge , the P r i nc i pa l Inve s t i ga tor kne w e xa c t ly h ow hi s a l loy , e u te c t i c , o rcrysta l h ad been hea ted, s oaked , and cooled.

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Diagram of the M A - O I O furnace control system.The "Temperature select" atthe left is a dialon the control boxshown inFigure 3.1 that is set by the astro-naut. "Soak period selection" on the right is a similar dial. The indicator lights("Indication function," lower left) showed whether the furnacewas heatingup,soaking, or cooling. The heater (far right) was automatically turned off forcooling or if a breakdown occurred.

Figure 3.2

oV Breaker Voltageregulator

O O O Q O O Q O

Heater

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Q Lead-Zinc and Aluminum-Antimony AlloysProduced in the MA-044 ExperimentT he M A - 04 4 cartridge for the electr ic furnace is sh o wn in Figure 3.3. Each ofthree car tr idges contained t w o sm al l "ampoules" inside a stain less-steelc y l i n d e r w i t h a "Fiberfrax" i n s u l a t i o n l in ing in the m i d d l e and h ea t - lev e l in ggraphite a t the ends. By using this desi gn, the Principal Investigat ors got onesam p le , in A m p o u l e A , heated to 1423 K ( 1 1 5 0 C ) a nd the other , in A m p o u l eB, heated to 1 12 3 K (850 C ) . A f te r a 3 -h o u r 20- m in u te h ea tu p p erio d, b o thsamples w ere soaked for 1 hour , t he n cooled down for 6.5 hours. The coppersurrounding A mpou le B kept a l l o f that ampoule a t the same tem perature,ev en th o u g h th er e was a d i f fe r en ce in t em p er a tu r e b e tween the hot end and thecool end of the furnace.

T he m ixt ure of lead (Pb) and zinc (Zn) was chosen because these twometals have very di f f e r e n t d e n si t y ( 1 1 . 3 5 g m / c m 3 f o r P b a n d 7 . 1 4 g m / c m 3 f orZn) and can n o t be m i x e d w e l l in o n e- g . T he sm al l in g o t in A m p o u l e B wa smade in the laboratory by put t in g 0.33 cubic centim ete r (3.9 gram s) of purePb on top of 0.66 cubic centim eter (4.7 grams) of pure Zn and heat ing i t in afurnace to 1 1 2 3 K (above the m e l t i n g p o in ts of Pb and Zn) for 10 m i n u t e s .Gravity (one-g) pul led the denser Pb down into the Zn but did not mix themwel l . I t was expected that the hour- long soak at 11 23 K in zero-g would mixth em m u ch better.Before th e Ap o l lo - So y u z f l i g h t , three sim il ar cartridges had been preparedand heated in a furnace identical to the one on Apollo-Soyuz. Th ese labora-tory tests showed exact ly what the t em p er a tu r es in A m p o u l e s A a nd B werefor each set of recorded temperatures a t the ends of the M A -044 car tr idge.T emperat ure- t ime p lo ts are shown in Figure 3.4.

A s sh o wn in Figure 3.5 , the m o l t e n Pb did not mix w i t h the m o l t e n Zn inzero-g. Both in zero-g and in o n e- g , the in ter face between Pb and Zn remainedsh arp . C ar e fu l ch em ica l tes ts and e lec t r ica l m easu r em en ts sh o wed v ery l i t t l edif fusion of the lead in to the zinc. The di f f us ion had been expected to be muchlarger. Th ese resul ts show errors in one-g laboratory work on di f f us ion inm o l ten m eta ls . Th e Pr in c ip a l In v es t ig a to r s co n sid er that there is a need forf u r t h er e x p e r i m e n t s in zero-g , where di f f us ion can be m easu r ed accu r a te ly .T he a l u m i n u m ( A l ) and a n t i m o n y ( S b ) m ix fo r m s an ac tu a l co m p o u n d ,a l u m i n u m a n t i m o n i d e ( A l S b ) , w h i c h has t ech n o lo g ica l im p o r tan ce because itis a very good m ater ia l f or solar ce l l s t h a t co n v er t sun l igh t in t o electr ic power.In f a c t , the c o m p o u n d A l S b s h o ul d be 30 to 50 percent more e f f ic ie n t t ha n thesi l icon t ha t has been used in solar ce l l s on m a n y N A S A s p a c e c r a f t and onSo y u z ( b u t not on A p o l l o ; see P a m p h l e t I ) . T he d i f f i c u l t y is in m i x i n g A l(densi ty 2.7 gm/cm 3 ) perfect ly w i t h Sb ( d en si t y 6 .62 g m / cm 3 ) in one-g.

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Diagram of MA-044 cartridge for alloys. Ampoule A at the hot end (bottom offurnace in Fig. 3.1) reached the highest temperature. Ampoule B near thecenter reached a lower temperature because the temperature decreased romleft to right along the cartridge. The copper around Ampoule B is a good heatconductor and served to keep the entire ampoule at the same temperature.Ampoules A and B and their contents are shown in more detail in the diagramsat the bottom.

Figure 3.3

wmPb-Zrro&vS *~vtf".y v.-.y ;:.-T 9.9mmI [ |Stainless steel.l* i-mm-thick walls[ IGraphite crucible,1-mm-thick wallsAmpoule A (AlSb)

19.0 mm

Ampoule B (Pb-Zn)

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He injection

00 200 300Time, min

400 500

Figure 3.4 Temperature versus time in the MA-044 cartridges. The top curve is for Am-poule A (at the hot end in Fig. 3.3); the lower curve is for Ampoule B; and thebottom curve is for the cool end of the cartridge. The horizontal arrows showthe melting points of the four metals, the AlSbcompound, and the Pb-Zn alloy.

I f they are not perfec t ly mixed, the a l loy can have three d i f fe ren t s truc tures:(1 ) pure A l S b wi t h a n e le c t r ic a l re s i s t i v i ty o f a bou t 30 f l -c m (30 ohms res is -ta nc e for 1-squa re c e n t i me te r cross sec t ion per cent imet er of lengt h), (2) a mixo f A l w i t h A lS b wi t h a re s i s t i v i ty o f a bou t 1 0 5 f l -cm, or (3) a mix of Sb w i t hA l S b w i t h a re s i s t i v i ty o f a bou t 1 0~ 5 f l -c m. P oc kets o f the l a s t two s t ruc tu re sw o u l d "short out" t h e desired solar-ce l l charac teris t ic .

A mpoul e A c onta i ne d 1 .5 c ubi c c e n t i me te rs o f A l and Sb m i xe d in propor-t i ons t o gi ve e xa c t ly 5 0 percent A l a toms an d 5 0 percent S b a toms (1 .2 6 gra msof A l a n d 5.74 gra ms of Sb) . T hi s a mpoule fo l lowe d the hi ghe r t e mpe ra ture -t ime curve on Figure 3.4, soaking for 1 .5 hours at 1423 K . Figure 3.6 s how s

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microscopic views o f th e res u l t ing a l loy: the top photograph is the f l ightsample cooled in zero-g and the lower photograph is a s ample cooled in one-g .T he red color shows the desired s tructure 1 , pure Al S b, and the blue colorshows pockets of s tructures 2 and 3. M any other photographs like Figure 3.6w ere taken , and the area of b lue (s t ruc tures 2 and 3) was measured on each. I nthe f l ight s amples , t he pockets averaged 2 percent o f th e area, w hereas theA l S b cooled in one-g averaged 1 0 percent. (I n Figure 3.6, these areas are 1percent and 25 percent . ) Accura te chemical and x-ray analys es conf i rmedthese measured areas, indica t ing a f ivefo ld increase in the c o m p o u n d A l S bcooled in zero-g over that cooled in o n e - g . M e a s u r e m e n t s o f th e electr icalresist ivi ty averaged 1 2 O-cm in the f l ight s amples an d 0 .0 1 H - c m in the one-gsamples.T he P rincipa l I nves t iga tors conclude tha t hea t ing and c o o l in g A l - S b m i x -tures in zero-g can produce much more uni f orm AlSb compounds than inone-g and tha t this procedure m ay lead to commercia l product ion o f th e A l S bcompound in space.

Photographs of lead-zinc ingots. In both zero-g (left) and one-g (right), the Figure 3.5lead and zinc have not mixed.

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Figure 3.6 Microstructure of AlSb formed in zero-g and one-g. These enlarged photo-graphs of polished cross sections of the AlSb ingots cooled in zero-g (top) andone-g (bottom) have been colored red for pure AlSb and blue for mixed struc-tures. The defective (blue) areas total 1 percent of the area shown in the topphotograph and 25 percent of the area shown in the bottom photograph.

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Q Melting of Aluminum, Tungsten, Germanium,and Silicon in Zero-gJoint E x p er im en t M A - 1 5 0 was d esig n ed b y th e R u ssian Prin cip al In v es-t ig a to r, I . I v an o v , an d used th e Am er ican M A - 01 0 f u r n ace in th e DM . T h erewere three ident ical car tr idges, each cont aining three ampou les, and al l threecar tr idges were returned to the U . S . S . R . on S o y u z . O ne am p o u le co n ta in eda l u m i n u m powder that was melted (a t 973 K, or 700 C) in an a t tem p t toproduce perfect spheres when the melt was cooled. Spheres were produced,bu t al um inu m oxide inf l uenced their formation and they were not perfect; theywere about the same as spheres produced in one-g.

The temperature- t ime p lo t selected by the Russians for the hot ends of thethree car tr idges is s h o w n in Figure 3.7. T he ampoule that received the f u l l14 2 3-K temp erature f or an hour- lo ng soak contained tu ngs te n spheres anda l u m i n u m . I n o n e- g , t he u n m el ted tu n g s ten sph eres wo u l d s in k to the b o t to m .In zero-g , they remained in place, and the R u ssian sc ien t i s t s m easu r ed the ra teof formation of t u n g s t e n - a l u m i n u m a l lo y s d u r in g th e 1 - h o u r so ak .

1473(1200)

Temperature,K CC)

Cartridgestransferredto Apollo

Cartr idgesloaded infurnace

0

1423K (1150 ' C )

"Furnaceswitch-on

I

Cartridgesremovedfrom furnace

10I !_,

Cartridgestransferredto Soyuz

Time, hrTemperature versus time in the Soviet materials melting experiment. The am-poules at the hot end produced an aluminum-tungsten alloy. Other ampoulesreached lower soak temperatures and produced germanium crystals andaluminum spheres.

Figure 3.7

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D

T he m id d le am p o u le r each ed so m ewh at lo wer tem p er a tu r e . I t co n ta in edge rma ni um "doped" w i t h 2 percent of si l icon atomsa semiconductor usedin electronic circui ts. T he m e l t sol idif ied d ir ec t io n a l ly , f r o m the cool en dtoward the hot end of the car tr idge. T he Russ ians consider these germaniu msilicon crystals to be better than those made in one-g.

Diffusion of Gold Into Molten LeadT he dif fusion of one l iqu id m e t a l into an o th er is im p o r tan t f or m e t a l l u r g i c a lengineers w ho make al loys. I n o n e- g , m easu r em en ts of how fast one l iquidme ta l spreads through another are complicated by convection currents. Thehotter par ts have lower densi ty , so they r ise. The cooler par ts of the l iquidshave higher densi ty and so th ey f a l l . I n zero-g, this type of co n v ec t io n doesnot occur, but other forces (Sec. 2 A ) m a y cause currents in l iqu id m eta ls .Cohesive forces of di f f e r e n t materia ls produce surface tension, wh ich cancause motion of the l iquids at an interface between tw o l iquids. Adhesiveforces produce wett ing , w hich can cause mot ion of a l iqu id along i ts in ter facew i t h a so l id . T h e o b ject iv e o f th e M A - 041 E x p er im en t was to m easu r e b o ththese motions in the absence of g r av i ty - p r o d u ced co n v ec t io n .

T he M A - 0 4 1 sc i en t i st s at the Oak R id g e Na t io n a l L ab o r a to r y had ane f f e c t ive m e t h o d f or m easu r in g t he a m o u n t of g ol d ( A u ) t h a t had m o v ed intothe l iquid lead (Pb) before it cooled an d so l id i f ied . T he sm al l in g o ts r etu r n edf rom Apollo-Soyuz were p laced in the nucl ear reactor at Oak R id g e , wh er ethey were bombarded by slow neut rons. S low neut rons cause a nuclea rreaction whereby 1 97 A u atoms (ordinary gold) become radioactive 1 9 8A ua t o m s , wh ich in turn emit beta rays of 0.96-megaelectronvolt energy. T hehal f - l i fe of 1 98 A u is 64.8 h ours , suf f ic ient ly long to a l low measurements ofA u atoms that had moved various distances in to the Pb. T he small ingots werecut in half , polished, and irradiated w i t h n eu tr o n s . T he f la t faces were thenplaced on photographic p la tes w ith a special em ulsion t hat is sensi t ive to the0.96-megaelectronvolt e lectrons emit t ed by the I 9 8 A u a to m s. W h en th e pla tew as developed, it s densi ty (b lackness) showed just h ow m a n y 198Au a to m swere at each place in a th i n l ay er of the specimen. Because the range (distanc et r av e led ) o f th e 0 .9 6- m eg ae lec t r o n v o l t e lec t r o n in Pb i s ap p r o x im ate l y 0 .4m i l l i m e t e r , o n l y t h e A u co n cen t r a t io n in this 0 . 4 - m i l l i m e t e r - l a y e r t h i c k n e s s isdetected.

T w o s m a l l i n g o t s of lead 3 cen t im eter s lo n g w i t h a 3 - m i l l i m e t e r p l a te ofP b - A u a l lo y at the end were carried in each of t h re e M A - 0 4 1 c a r t r id g e s for theM A - 0 1 0 f u rn a ce . O ne ingot w as placed at the hot end and soaked at 923 K(650 C) for 1 h o u r . T he second w as placed h a l f w a y d o w n the car tr idge,wh er e the t em p er a tu r e r each ed 723 K (450 C ) , for the 1 -hou r soak. (Lead

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m el ts at 600 K, or 327 C.) I n the first cartridge, the lead ingots weresurrounded by steel that was wetted by molten Pb; in the other two cartridges,the lead w as surrounded by graphite that was not wet ted by m o l ten Pb. Asimilar set of three cartridges was heated in the same way at Oak Ridge inon e-g.

M easu rem en t o f th e zero-g specimens showed that the Au atoms hadmoved more than 1 cen t im eter in the lower temperature zone (723 K) andmore t h a n 2 cen t im eter s in the highe r tem peratu re zone (923 K ) . T h e A uatoms m oved t he entire lengt h of the Pb in the one-g specimens. In the zero-gampoules, the motion was m ainl y down the center ; there w as less motion nextto the w a l l s . T he motion o f th e Au atoms in to the Pb was caused by di f fus ionand by currents due to surface tension. Fur ther experiments are needed toseparate these two types of motion. The A u move ment in the one-g specimensw as m o st ly due to convection.

In zero-g, the ef f ec t of wett ing the steel ampoule was less than expec ted;that is , the motion of the Au in to the Pb was very similar to that in thenonwetting graphi te ampoules. I n on e-g, there was a smal l wetting effect , buti t w as much less than predicted. T he m an y m easu r em en ts in zero-g seem toindicate that l iqu id m eta l "slipped" along both the graphite and the steel w al lsan d did not wet the s tee l wa l l s .

Magnetic Alloys Formed in Zero-gPhysicists have f o u n d t h a t magnets are made up of many small magnetic"domains," each wi th a nor th and south magnetic pole . In an ordinary bar ofiron, these magnetic domains are pointing every wh ich w ay (and tend tocancel each o ther 's magnetic f ie lds) ; however , i f the bar is put in to a s trongmagnetic f ield (close to another magnet or in a coi l o f wire carrying direct-current e lectr ici ty) , the domains are a l igned and the iron bar is magnetized.For a permanent magnet , the doma ins must remain aligned , held there byforces in the m ater ia l . I n a pure iron bar, such forces ar e very small , and thed o m ain s lose their a l ig nm ent as soon as the outside magnet ic field is removed.H owever , some al loys have been show n to have much larger in te rnal forces tohold magnetic a l ignment. The force holding the domains in l ine is measuredby the magnetic- fie ld strength necessary to turn them around. T h i s is calledthe "coercive force." I t is low for iron, which indicates how easi ly thema gne t i c a l i g n m e n t can be changed in iron. Coercive force is very high insome magnetic a l loys.O ne objective of Experiment M A -070, Zero-g Processing of M a g ne t s , w asto m ak e m ag n e ts of very high coercive force by fo r m in g lo n g , t h in fibers ofmagnetic mater ia l a l igned in a "matrix" of some other mater ia l , such as

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b i s m u t h , which surrounds the f ibers. The idea was that the f ibers would be ast h i n as the m ag n et ic d o m ain s th ey co n ta in . W h en t he d o m ain s are a l ig n edalong the f ibers, the matr ix would tend to hold them that way.

T h i n f ibers are formed along the temperature gradient (direction from coolto hot) wh en cer tain molt en a l loys are cooled progressively from one end to theother . Figure 3.8 shows how this was done in the M A -01 0 f urnace. The threeM A - 0 70 car tr idges each contained three ampoules. Ampoule 1 a t the hot endw as surrounded by a graphite "heat leveler." T he am p o u le w as heatedu n i f o r ml y (no temperature gradient) and contained a mix of 50-percentb i s m u t h (B i) a toms and 50-percent manganese (M n) a toms. A mpoules 2 and 3were in a s trong temperature gradient of 30 K/cm(30C/cm)down to thelow er temperature a t the cool end of the cartridge. A mpoule 2 was f i l l ed with am ix o f copper an d co p p er - co b a l t - cer iu m ( Cu - ( Cu Co ) .Ce) , and A m p o u l e 3w as f i l led w i t h a mix of b i s m u t h m a n g a n e s e -b i s m u t h ( B i - M n B i ) .

T he t em p er a tu r e at the hot end of the M A - 07 0 cart r id g e (A m p o u le 1) wa sraised to 1348 K (1075 C) and kept there for 45 minutes. The furnace wasthe n a l lo wed to cool slowly to 673 K (400 C ) o v er 10.5 hours to sol idi fy them i x , and then cooled quickly by in ser t in g h e l iu m gas.T he temperatures inA mpou les 2 and 3 were lower but fo l lowed the same pat tern. T he high of 1323K (1 05 0 C) in Am p o u le 2 an d 1123 K (850 C) in Am p o u le 3 m el ted th e i rco n ten ts . T he cooling w as from r ight to lef t in order to produce fibers alongthe axis in A m p o u l e s 2 and 3.

Gradient section Heat extractorrp v \ \ \ \ \ \ \ \ \ \ \ _ v \\u\\uiIAmpoulel;1 I'uwuuuffv Ampoule 2 T\ V U \ \ \ M ="V

Thermal insert(graphite)

l \ \ \ \ \ \ \ \ \ \ \ \ V \ \ \ \ \ \ \ \ , vAmpoule 3 > t? v l\\\\\\\\\\\\\\\VA\\\\

\\ o/ X r v"tainless-steel Insulation Thermal insertsupport tube (graphite)X Thermocouples

Figure 3.8 Diagram of MA-070 cartridge for magnetic alloys. Theheat leveler at the left isat the hot (bottom) end of the MA-010 furnace, and the heat extractor at theright is at the cool (top) end. The three ampoules contained different mixes forheating and cooling, Ampoules 2 and 3 in strong temperature gradients. Thedirectional cooling was intended to form eutectic fibers in Ampoules 2 and 3.

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O R I G I N A L P A G E IS?OOR Q UA LI T Y

T he m e l t in A m p o u l e 1 cooled in zero-g to p r od u ce la rg e , u n i f o r m M n B icrysta ls. ( In one-g , most of the M n r ises ( f loats) to the top, and the fewcrysta ls produced are small .) T he array of separate M nB i cryst a ls showed thatthere was a temperature gradient durin g the cooling from t he edge t o the centerof the c y l i n d r i c a l a m p o u l e . A s a r e s u l t , the magnetic proper ties of the M n B iare comp lex, show ing both low and high coercive forces.

In A m p o u l e 2 , the C u - ( C u C o ) _ C e m ix reacted with t he am p o u le wa l l s(made of boron nitr ide) and solidified in long crysta ls exten ding inw ard fromthe wal ls . T he coercive force was not increased in the zero-g samples.

Near th e co ol en d o f A m p o u le 3 , th e M n B i f ib er s were n o t we l l a l ig n ed , b u tas the cooling f ront proceeded toward the hot e n d , the f iber a l i g n m e n t s t e a d il yi m p r o v e d , as s h o w n in Figure 3.9.T he coercive strength of these samples w as87.6 x 10 4 am p er es / m eter ( 1 .1 X 1 0 4 oersteds)more th an tw ice as high asmeasured in M n B i - B i eu t e c t ic f or m e d in one-g. This is an im p o r t an t r esu l t andm ay lead to a new technology of m a n u f a c t u r i n g m ag n ets .

Fibers in magnetic eutectic from Experiment MA-070. No fibers were formedin the large "chunks." The thin white lines at the top are MnBi fibers in bismuth,which shows as mottled gray in this photograph of a polished cross section.

Figure 3.9

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p Transparent Fibers From a EutecticT rans paren t f ibers ha ve an important use as "light pipes" in the new t e c hnol -ogy of f iber optics . A n experiment on S ky lab produced long fibers of sodiumf luoride (N a F ) i n sodi um c h lor i de (N a C l , c ommon sa l t ) whe n a mi x o f thesetwo substances was mel ted a t about 1143K (870 C) and then cooledprogressive ly from one end of the cartridge to the o t h er . E x p e ri m e n t M A - 1 3 1tried to produce a s imil ar eutec t ic made of l i t h i u m f luor i de (L i F ) i n N a C l onA p o l l o - S o y u z .

T he M A -1 31 sc i e n t i s t s c ons t ruc te d n i ne c a rt r i dges w i t h the d i me ns i onsshown in Figure 3.10. T he sa mple w as 29-percent LiF and 7 1 - p e r c e n t N a C l ,me l te d an d sol idi f ied in a l a bora tory , the n c a re fu l ly cut to fi t i ns i de a gra phi tec y l i n d e r , w h i c h w as encased in a s ta inless-s tee l cyl inder 1 1 1 m i l l i m e t e r s o n gand 9.6 m i l l i m e t e r s in di a me te r . T he re was a 4 3-m i l l i m e te r e mpty sec t ion( f i l led o n l y w i t h inert gas) at the hot end to a l low for therm al expansion du ringh e a t i n g . The hot end was heated to 1293 K (1020 C) in the M A - 0 1 0 f u r n a ce .A t tha t po i n t , the re was a t e mpe ra ture gra di en t o f 5 0 K/cm (50C l e m ) d o w nthe cartridge toward the cool end, and the las t 1 2 mil l im ete rs of sa l t mix a t thecool e n d w a s u n m e l t e d because the tempera ture there was less t h a n 1073 K(800 C) , the me l t i ng poin t of N a C l . A s t h e m i x cooled (at 0.6 K / m i n , or 0.6C /mi n) , f i be rs of LiF grew out i n to the m o l t e n m ix because L iF "freezes" at1 1 4 3 K. Th ese f ibers grew s teadi l y a t a ra te of about 2 /A m/sec dur ing the next2 0 hours . B a c k on Ea r th a f te r the mi ss i on , the so l i d i f i e d N a C l -L i F e u te c t i cwas analyzed for f iber length, diameter , spacing, and optica l propert ies.

9.6 mm outside dimeter 43 mm

Stainless steel container

Hoien d

Graphite liner8.9 mm outside diameter7.9 mm inside diameter 6.3 mm

Figure 3.10 Diagram of MA-131 cartridge for NaCl-LiF eutectic. There was a strong tem-perature gradient of 50 K/cm from the hot end at the left to the cool end at theright. Fibers of LiF grew from the cool end toward the hot end.

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O R I G I N A L P A G E ISO F P O O R Q U A L I T Y

Th r ee of the M A - 1 3 1 c a rt r id g es w e r e f low n on A p o l l o - S o y u z to be m el tedan d re frozen in zero-g. Three o ther car tr idges w ent through the same temp era-tures at Westinghouse Laborator ies in one-g , an d three were kept by theM A - 1 31 sc ien t i s t s a t U C L A . T h e m ain r esu l t s wer e a co m p ar iso n b e tween th efirst tw o setsthe fibers grown in zero-g and those grown in one-g. Figure3 . 1 1 sh o ws t he zero-g fibers at the place where the sal t m ix was u n m el ted( lef t ) . There was a s l ig h t b u lg e in t h i s u n m el ted su r face , and the fibers grewp er p en d icu lar to th e su r face , b o win g o u twar d r a th er th an g r o win g s t r a ig h td o wn the cartridge as in tended. Figure 3.12 sh o ws the LiF f ibers far therdown, where the temperature gradient was more uniform and the f ibers aremore near ly paral le l . The zero-g fibers in Figure 3.12 ( top) are long (moretha n 1 m i l l i m e t e r ) , w h e r e as the one-g fibers (bot tom ) are sh o rt ( 0 .05 m i l l im e-ter and less). Figure 3.13 s h o w s t he r em a r k ab l y r eg u lar sp ac in g a nd4- m icr o m eter d iam eter o f th e L iF f ib er s .

T h e N a C l - L i F e u t e ct i c w i l l b e usefu l fo r o p t ica l wo r k wi t h in f r a r ed l i g h t .The LiF f ibers transmit infrared l ight of wav elen g th s f r o m 3 to 12 m icr o m e-ters. T he long fibers grown in zero-g are about twice as ef f ic ien t f or infrared

LiF fibers at the unmelted salt boundary in Experiment MA-131. The unmelted Figure 3.11salt is on the left side.

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Figure 3.1 2 Parallel LiF fibers formed in zero-g and one-g. The fibers formed in zero-g(top) are more than 1 millimeter long in this photograph of a lengthwise cutthrough the eutectic bar, enlarged 56 times. Fibers formed in one-g (bottom)are less then 0.05 millimeter long in this 210-times enlargement.

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O R I G I N A L PA G E ISOF POOR QUALTTY1

Cross sections of fibers in NaCI-LiF eutectic. The fibers are regularly spacedboth in the one-g (top) and zero-g (bottom) samples. The 1 900-times enlarge-ment of the zero-g sample shows the remarkable uniformity of fiber sizes.

Figure 3.13

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G

f iber opt i c s as the shorter one-g f ibers. When infrared l ight goes t h r o u g h t heeut ectic crosswise (perpendicu lar to the fibers) , i t is scattered and polarized bythe f ibers; tha t is , i n f ra red w a ve s osc i l l a t i ng in the direct ion of the fibers ge tt h r o u g h more easi ly than t h e waves osci l la t ing across t he fibers. T h e N a C l -L iF eutec t ic pla tes , cut so t h a t the f ibers are para l le l to the faces , can be usedas infrared polarizers ( lik e Polaroid is used for visib le ligh t).

Questions for Discussion(H e a t T ra nspor t , T e m pe ra ture , A l loys , Eu te c t i c s )

4. I f th e M A -010 furna ce use s 2 0 5 w a t t s and t a ke s 3 hours t o reachm a x i m u m t e mp e ra ture , w ha t a m ount o f e nergy i s added to the c on te n ts o f thefurnace? Where did the heat go d u r i n g the cooling of the furnace?

5 . I f th e cartridge used in one e xpe r i me nt we re twi c e as massive as thec a rt r i dge use d i n a no the r e xpe r i me nt , how would the he a tup t i me s d i f fe r? T hec ooldown t i me s?

6 . W h i c h furna c e e xpe r i me nts re qui red a t e mpe ra ture gra d i e n t in the i rsa mple s? W hi c h re qui re d uni form te mpe ra ture ?

7 . H o w can th e cartridge design give a hi ghe r or a lowe r t e mpe ra turegra di e n t?

8 . H o w m u c h p o w er w as re qui re d for the e le c t r i c furna c e du r i ng t he soakperiods at c ons ta n t t e mpe ra ture ?9 . H o w does a v a c u u m in the M A - 0 1 0 f u r na c e case reduce hea t loss?

10 . W ha t shou ld c a use dif fusion of one l iqu id me ta l i n to a no the r whe rethey are in c onta c t at h i gh te mpe ra ture in the M A - 0 1 0 f u rn ac e?

1 1 . In a 50/50 mix of the a toms o f two e le me nts , w ha t ra t i o of masses m u s tbe used?1 2 . Th e physica l propert ies of an isotropic substance do not va ry wi thdirec t ion. By what means were nonisotropic (anisotropic) substances formed

in t h e M A - 0 1 0 f u r n a ce ?1 3 . H o w w o u l d it be possible to get more detailed da ta on the mot i ons of

gold through l iquid leadmore l ike a mot i on p i c ture tha n t he beta-raypi c ture s of Expe r i me nt M A - 0 41 ? (Remember tha t radioac t ive 1 9 8 A u has aha l f - l i f e of 64.8 hours an d tha t furnace hea tup an d cooldown t imes are at least3 hours . )

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1 4 . L o n g , co n t in u o u s LiF fibers were important in E x p er im e n t M A - 1 3 1 .Were long fibers of M nB i needed in Experiment M A - 0 70 for permanentm ag n e ts?

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4 Growing Large,NearlyPerfect Crystals inZero-g

Cr y s ta ls ar e solids in w h i c h most o f th e atoms ar e arranged in a regular patternl ike a stack of bricks. A s a crysta l grows, in teratomic forces ideal ly addanother layer of "bricks" precisely placed on the on es already there. Crysta lscan be grown by combin ing substances in a so lu tion, by freezing a l iquid , orby condensing a vapor on a solid. For instance, you can see salt crystals formin salt wat er as it dries or ice crystals form in freezin g wat er. T ruly perfectcrysta ls probably do no t ex is t . T he solu tion, or m e l t , or vapor is u su a l lystirred, or is not u n i f o r m , or is moving irregular ly so th a t a growing crysta lbecomes u n ev en and a j u m b l e of small crysta ls resul ts. Even when one crystalgrows to a fa ir ly large size, it general ly develops imperfections in i ts layerswhe n some other kind of atom is deposited like an oversize brick in a stackof br icks. Then the regular layers of br icks get out of s tep with the layersbeneath , and there is a "structural d e f e c t " in the crysta l .

Cr y s ta ls h av e become important in modern technology. For instance, thehardness of diamonds (carbon crysta ls) makes them valuable for use in dri l lbits , and germ anium crysta ls are used in detect ing gam ma rays (see P amphl etI I ) . M any other crysta ls are used in e lectronics crysta l osci l la tors, so lid-sta te recti f iers , and o ther semicondu ctors. Scientists and engineers have m adegreat progress in grow ing large cryst als und er car e f u l l y contro l led condit ions,bu t co n v ec t io n cu r r en ts in one-g often produce changes in the r eg u lar i ty ofg r o w t h . T h e s e changes resul t in composi t ional an d s t r u c tu r a l d e fec ts . F or th isr easo n , c r y s t a l - g r o w th ex p er im en ts w er e m ad e in zero-g on Sk y lab in 1973,an d the resul ts were so promising that three experiments were scheduled onA p o l l o - S o y u z , t w o o f th em in the M A - 0 1 0 f u rn a ce .

Growth of Large Germanium CrystalsExpe r i me nt M A - 060 fo l lo w ed a S k y l ab ex p er im en t th a t p ro d u ced cr y s ta ls o find ium a n t i m o n i d e ( I n S b ) t ha t were more nearly perfect t h an any produced onE a r t h . T h e s c i en t i s t s a t M I T w a n t e d t o d e ter m in e wh e t h er o th er m o t io n s due tosurface t en s io n o r we t t in g wo u l d d iso r g an ize g er m an iu m ( Ge) c r y s ta l g r o wthin zer o - g , ex ac t ly how fast such crysta ls grow, and wh at h ap p en s wh en thege rma ni um i s "doped" w i t h the 1 percent of g a l l i u m (Ga) needed f orelectronics use. They had developed a m eth o d of " in te r face d em ar ca t io n " tocheck growth rate. A lay er of a to m s a t th e crysta l surface w as ' ' marked ' ' every4 seconds by sending a pulse of e l ec t r i c i t y ( 30 am p er es fo r 9 0 m i l l i seco n d s)f rom t he g r o win g cr y s ta l ( +) in to t h e m o l t e n G e (-) . S l ices of the cr y s ta l wer ela ter e tched w i t h strong acids (nitric acid, H N O 3 , an d hydroflu oric acid , H F) ,which showed a f ine l ine where the crystal interface was at the t im e of eachelectric pulse. (See Fig. 4.2.)

PRECEDING PAGE BJ.AN K NOT FILM ED< 133


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T he M A - 0 6 0 car tr idge containing a 1 0- cen t im eter cy l in d er of G e dopedw i t h Ga in a quar tz tube is shown in Figure 4.1 . At each end of the Ge weret i g h t l y f i t t ing graphite caps at tached to electrical leads for the pulses ofelectr ici ty . On A pollo-S oyuz, the hot en ds of three of these cartridges wereheated in the M A -01 0 furnace to 1393 K (11 20 C ) so that the Ge was melt edd o wn to about 3.5 cen t im eter s from the cool en d s. T he cartridges were keptth is way ("soaked") for 2 hours. Then the temperatu re was l owered at the ra teof 2.4 K/min (2.4 C/min) for more than an hour to grow the Ge crysta ls a tabout 5 / j .m/sec. The furnace current was then switched off , which al lowed asomewhat faster cooling rate for another hour. Then helium was inser ted forfast co o ld o wn .

A f t e r the miss ion, the car tridge w as opened at M IT . T he Ge crysta l s l ippedeasi ly out of the quar tz tube, w h i ch sh o ws th a t Ge does not wet quar tz inzero-g. F or some reason, t h i s is a change from on e-g, wh er e l iquid G e doeswet quar tz and adheres t o i t as i t so lidifies. In one cartr idge, where the Ge waspacked with one f lat crysta l surface across the quar tz tube a t the cool en d ,there was a single a lmost perfect crysta l , 6 .5 cen t im eter s lo n g , fo r m ed f r o mthe melt . ( In ground-based experiments, the longest single crysta l obtainedwas 3 centimeters. Beyond that length , the crysta l grew in "grains," w i t h it sma i n axis in a di f ferent direction in each grain.)

T he crysta ls were cut lengthw ise in to 1 -mil l imet er s l ices. One face of eachslice was polished f la t and then etched w i t h acid. Figure 4.2 shows the coolend of the first car tr idge w ith unme lte d Ge at the top , a narrow region wherethe melting was par t ia l , and the smooth crysta l a t the bot tom. The f ine l in esare demarcations of the crysta l surface, produced by the current pulses a t4- seco n d in te r v a ls . M easu r em en t o f th e spaces between these l ines gives thecrysta l growth in 4-second in te r v a ls . Th e g r o wth was sm al l a t f irst butincreased rapidly. A s Figure 4.3 shows, th e growth rate leveled o f f a t about 9or 10 /*m/sec.

A l t h o u g h there are sti l l some unc er tain ties about the eff ects of Ga "dop-ant" and i ts spread through out the Ge crysta l , the M A - 06 0 resul ts show t h a tlarge, near ly perfect crysta ls can be grown from a m el t in zero-g, and thegrowth rate of germa nium in directional so lidif ication was m easured.

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Diagram of MA-060 cartridge for germanium crystal growth. The germaniumwas inside a quartz tube with graphite "cups" at the ends for electrical con-tacts. One platinum wire for the electric pulses runs below the quartz tube tothe hot end and inside the tube to the graphite cup.

Figure 4.1

Heat-levelecregion Heat-extractionregion

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Figure 4.2 Interface demarcation lines in germanium crystal grown in zero-g. A length-wise slice of the crystal, polished and etched with acid, shows a line markingthe crystal surface at the time of an electric current pulse. The lines are closenear the unmelted germanium at the top, showing that crystal growth startedslowly.

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1.2 1.6Distance grown, cm

20 2. 4 7 8

Rate of germanium crystal growth in zero-g. The growth in 4-second intervalswas measured from Figure 4.2, converted to growth rate in micrometers persecond, andplotted against the distance grown (downward rom the top of Fig.4.2).

Figure 4.3

Growth of Crystals From VaporSmall crysta ls were formed at the cool end of a quartz tube from a solid( u n m e l t e d ) source a t the hot end by using chemical vapors as "transportagents." This technique had been tr ied on Skylab in 1973 u sin g g er m an iu mselenide (GeSe) an d g er m an iu m te l l u r id e ( GeTe) as the source mater ia ls andgermanium iodide gas ( GeI 4 ) as the transpor t agent. T h e solids (s ) were notvaporized by high tem perat ure. Instead, they reacted w ith the gaseous (g )transpor t agent a t 873 K (600 C ) to g iv e two o th er g ases , wh ic h d i f fu sedd o w n the tu b e to release G e S e or GeTe as crysta ls at 773 K (500 C ) . T h ech em ica l eq u a t io n s are

2 G e S e (s) + 2 G e I 4 (g) at 873 K 4 G e I 2 + S e_2 G e S e crysta ls + 2 G e I 4 (g) at 773 K

2 G e T e (s) + 2 G e I 4 (g) at 873 K 4GeI., + Te22Gefe cr y s ta ls + 2 G e I 4 (g) a t 773 K

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T he a m o u n t of materia l carried by the t ransport agent w as measured bywe i ghi ng the sma l l c rys ta l s a t the cool end of the tube when i t was re turnedto the RP I l a bora tory . T he a m oun t wa s foun d to be une xpe c t e d ly l a rge.Because pure crysta ls of c omple x ge rma ni um c ompounds are needed f ore le c t roni c s , th i s va por growth is an i mpor ta n t t e c hnology. T he c rys ta l sproduced in zero-g are larger and more nearl y perfect t ha n those produ ced bythe same process in one-g.

A p o l l o - S o y u z E x p e r i m e n t M A - 0 85 c o nf i rm e d t h e S k y l a b r e s u l t s u n d e rsome w ha t d i f fe r e n t c ondi t i ons . T hre e s ta i n le ss -s te e l c ar t r i dge s for theM A -010 e le c t r i c furna c e c onta i ne d sea led qua r tz tube s 15 c e n t i me t e rs long .A t the ho t e nd , e a c h qua r t z tube ha d two t h i n silica rods tha t he ld the sourcema te r i a l . A f te r a 2 -hour he a tup pe r i od , the ho t e nd wa s a t 877 K (604 C )and the cool end a t 780 K (507 C ). Th ese t e mpe ra ture s we re he ld c ons ta n tfor 16 hours. T hen the furn ace was turned off and hel ium was inserted tocool th e c a r t r i dge s ra p i d ly .T h e source materia ls used in E x p e r i m e n t M A - 0 8 5 w e r e G e S e an dg e r m a n i u m su l f ide ( G e S ) , a nd the transport agents were GeI 4 and g e r m a n i u mc hlor i de gas ( G e C l 4 ) . T he cartridges, labeled A , B , a n d C , were loaded beforet he mi ss i on as f o l l o w s .

Cartridge Source material Transport agent PressureA 1 .5 grams GeSe 0.123 gram G eI 4B 1 .5 g r a m s G eS 0.059 gram G e C l 4C 1 . 5 grams G eS 0.062 gram GeCl4

70.9 kN/m 295.2 kN /m 2Pressurized w i t hargon to 290.8k N / m 2

Th e pressures in the f irst two cartridges (A and B) were somewhat less th ana tmosphe r i c pre ssure .2 T h e third cartridge ( C) was a t a lmos t thre e t i me satmospheric pressure in order to tes t the ef fec t of ga s de ns i ty on the d i f fu s i o nof the chemical vapors. In B and C, the chemical reac t ions vtere2GeS (s) + 2 G e C l 4 (g) at 877 K.^ 4 G e C l2 + S . ,-* 2GeS crystal 's + 2 G e C l 4 (g) a t 780 KT he GeCL, and S, are gases at 773 K (500 C) and a b o v e .

-One a t mosphere or 760 torr is equal to 101 kN /m 2 .

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W h e n the three cartridges were returned to R PI a f te r t he A p o l l o - S o y u zm iss io n , t he M A - 085 sc ien t is t s fo u n d th e q u ar tz tu b e s t i l l sealed and there ma i ni ng source material still f i r ml y at tached. The small crysta ls that hadformed at the cool en d were loose, as sh o wn in Figure 4.4. They were

Germaniumselenitic crystals formed from vapor in a quartz tube. The MA-085quartz tube was in a cartridge heated to 877 K (604 C) at the left (hot) endand 780 K (507 C) at the cool (right) end. The GeSe at the hot end reactedwith the Gel4 transport agent to formGel2 gas and Se2 gas, which later com-bined to form GeSe at the cool end.

Figure 4.4

co l lec ted , weig h ed , and an a ly zed by x-ray di f f ract ion, wh ich sho wed that t hecr y s tals wer e n ear ly p er fec t . M o s t o f th em wer e l i t t l e p la tes , m ix ed w i t h a fewneedle shapes, as shown in Figure 4.5. T he to ta l mass transpor ted in 16 hoursf rom the hot source to the cool end of the quar tz tube was twice the predicteda m o u n t in Car tr idges A and B and more t h an th r ee t im es in Car t r id g e C.

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I * /Figure 4.5 Germanium selenide crystals formed in one-g and zero-g. Enlarged photo-

graphs of the small crystals formed in the MA-085 Experiment show that thecrystals formed in one-g (left) were larger and more irregular than the crystalsgrown in zero-g (right).

Q Growth of Crystals From SolutionT h e M A - 0 2 8 C r y st a l G r o w t h E x p e r im e n t di d no t u s e t h e M A - 0 1 0 e l e c t ri cfurna c e . In s tead , th r ee k in d s of crysta ls were grown in a water so lu t io n at theApollo cabin temperature (288 to 297 K, or 15 to 24 C ) . T he idea, a new onein zero -g c r y s ta l fo r m at io n , was to release two chem icals in t o opposite sideso f a co m p ar tm en t f i l led w i t h w a t e r . Th ese so lu b le ch em ica ls di f f use to war deach other in the wat er . W hen they meet , they react to produce an insol ubl esubstance that forms a crysta l in the w a t e r . O n E ar th , in one-g , each new l i t t l ecr y s ta l f a l l s to the bottom of the co n t a in er . Sc ien t i s t s h av e t r ied t o p r ev en t th isby p u t t i n g a gel in the w a t e r to keep t he sm al l c r y s ta ls f r o m f a l l ing an dc l u m p i n g to g e th er . T h e so lu b le ch em ica ls can d i f fu s e t h r o u g h t he gel, al -t h o u g h the gel s l o w s t h e m . H o w e v e r , the gel a lso tends t o isolate new cr y s ta lsso th a t n o n e o f th em grows very large. In zero-g , the crysta ls don' t f a l l ;th er e fo r e , no gel is needed and the crysta ls ca n grow to larger sizes.

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A diagram of the three-compar tment container for crysta l grow th in zero-gis shown in Figure 4.6. Co m p ar tm en t A w a s f i l led wi th p u r e wa ter and wasseparated f rom C ompartm ents B and C by v a lv es . (I n Figure 4.6, the v a l v e toC o m p ar tm en t B a t th e l e f t is open; the other v alve is c losed. ) Co m p ar tm en ts Band C were for the chemicals . O n A pollo -Soy uz, w hen al l was quiet in zero-g

Fill port caps (3)Valves:Closed.Open

Clamp ringValve handle

Compartment ACompartment C

Diagram of the MA-028 reactor for forming crystals in solutions. Before Figure 4.6launch, three compartments were filled through the "fill ports" on top. Crystalsformed in Compartment A.

(when there w as no thruster acceleration or to r q u in g ) , the tw o valves t oCo m p ar tm en ts B and C were opened by twis t in g the handles. Then thech em ica ls di f f use d s l o w l y t h r o u g h the w a t e r to m eet in C o m p a r t m e n t A wh er ecrysta ls formed. Figure 4.7 sh o ws six of these "reactors," each made oft ra nspa re n t Lexan (a p last ic) so t h a t the crysta ls could be seen and photo-g r ap h ed as th ey fo r m ed . In fo u r o f th e r eac to r s , Co m p ar tm en t A was 5.08centimeters long and 3.5 centimeters wide. I n the other tw o reac tors , C o m -p ar tm en t A w a s o n ly 4 .1 9 cen t im eter s lo n g , a lm o st 1 cen t im eter sh o r te r . E achcompartment had a hole covered w i t h a scr ewcap so th a t th e co m p ar tm en tc ou ld be f i l led before l aun ch. T he reactors were a l l bol ted to a locker on thew a l l o f t h e A p o ll o C o m m a n d M o d u l e (see Pam p h le t I ) .

T he f o l l o w i n g three kin ds of cryst a ls were chosen f or grow th in zero-g. A l lof t h e m had b een s tu d ied ex ten siv e ly in laborator ies on E a r t h .

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1 . C a l c i u m t a r t ra t e ( C a C 4H 4O 6 4H 2O) forms large crystals in a gel.2. C a l c i u m c a rb o n at e (CaCO3) crystals (calci te) are used in opt ica l equip-m en t because of their double refrac t ion, which s epara tes components ofpolarized l i g h t .3. Lead sul f ide (P bS) crys ta ls are needed f or e lec t ronics .

Figure 4.7 The six MA-028 reactors for Apollo-Soyuz. Made of transparent Lexan(plastic), they were bolted to a locker in the Apollo Command Module andphotographed every 1 2 hours after the valveswere opened. Thereactors werereturned to the Principal Investigator after splashdown.

T he reac t ions invo lv ed tw o "reactant" chemicals in each case, one inC o m p a r t m e n t B and the o t h e r in C o m p a r t m e n t C :React ion (I)CaCl2 + N a H C 4 H 4 O 6 -I - 4H2O- C a C 4H 4O 6-4 H 2O crys ta ls + N a C l + H C lReaction (2 )C a C l2 + (N H 4 ) 2 C O 3 - CaCO3 crystals + 2 N H 4 C lReaction (3)C H 3C S N H 2 + P b C l2 + H2O -> PbS crystals + C H 3 C O N H 2 + 2 H C 1(Thioacetamide) (Acetamide)

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Each of these reactions was conducted in two di f ferent reactors: reactions(1 ) and (2) in both "long" (5 .08 cen t imeters ) an d "short" (4.19 centimeters)C o m p a r t m e n t s A , a n d reaction (3) in the l o n g C o m p a r t m e n t A w i t h t he valueof the wat er pH (acid ity) adjusted to 1.0 in one reactor and to 0.5 in the otherreactor by adding hydrochloric acid (HC1). These two tr ials of each reactionwere made in order to learn what effec t the leng th o f Com par tment A or theacidity of the water would have on the formation of crystals.

On the f i f th day of the A p o l l o - S o y u z f l i g h t , the valves were opened in allsi x reactors , and color photo graphs of each reactor were taken every 12 hoursw i t h a N ikon 35-mi l l imeter camera. T hes e phot ographs s how tha t no th ing h adleaked before the experiments s tar ted and tha t crys ta ls f ormed s low ly in eachC o m p a r t m e n t A d u r i n g the r e m a i n i n g 1 1 6 hours of zero-g f l i g h t . I n reactors(1 ) an d (2) , th e chemical reaction had gone to compl e t ion bef ore s p las hdow n;th a t is , no more crystals were being formed. In reactor (3) , PbS c rysta ls weresti l l formi ng jus t before splashdown and PbS s ediment cont inued to form inone-g .

T he calc iu m tar t rate crys ta ls produced by reaction (1) are s h o w n in the topphotograph in Figure 4.8. Some of the crysta ls are 5 m i l l im eters long. T heyar e larger than crystals produced in gel at one-g, and more of t h e m ar e pla teshaped rather than prism shaped. The smaller calci te crystals of reaction (2)are s how n in the bo t tom phot ograph. M any of these crys ta ls are about 0 .5m i l l i m e t e r on an edge and of rhombohedral shape. The PbS crystals were al lsm al l ( less than 0 .1 m i l l i m e t e r ) .

T h e M A - 0 2 8 E x p e r i m e n t w a s t he first at tem pt to grow crys ta ls f romchemical s o lu t ions in zero-g. I t is hoped t hat reactor design and tempera turecontro l can be i m p r o v e d so tha t larger crystals can be g r o w n in fu turesp acef l ig h ts .

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Figure 4.8 Crystalsof calcium tartrate andcalcite grown in ExperimentMA-028. Some ofthe calcium tartrate crystals (top) are as long as 5 millimeters. The calcite(calcium carbonate) crystals (bottom) are about 0.5 millimeter across.

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D Questions for Discussion(Cleavage Planes, Crysta l Growth)1 5 . C rys ta l s of ma ny mi ne ra l s sp l i t a long "cleavage planes," w h i c h are

f la t or offse t para l le l surfaces tha t ru n s tra ight through the crysta l para l le l tothe layers of a toms. I n the analogy of a stack of bricks (Sec.4), how w o u l d t hecleavage planes run? H ow does th i s ma tc h th e "cubic s t r u c t u r e " of a salt(N a C l ) c rys ta l?

1 6 . W a te r does n o t we t a greased cup but i t does wet an a l u m i n u m cup.I fyo u f reeze water in both these c u p s , w i l l the ice stick or come out easi ly?

1 7. P l a t i n u m w i re w as used for the electrical leads in the M A-060 cartridgef o r m e l t i n g g e r m a n i u m . W hy w a s n ' t a cheaper wire used?

1 8 . Figure 4.3 shows tha t the germanium crysta l s tar ted growing verys lowly a f te r t h e M A - 0 1 0 f u r n ac e w as tu rne d o f f , the n speeded up . W h y ? H owwould you expect the growth ra te to change whe n the fast cooldown w ass tarted la ter o n?

1 9. W h e n moi s t wi nd s b low across f re e z i ng mounta i n peaks , long crysta lsof ice form on cold rocks facing the w i n d . H ow does th i s forma t i on of c rys ta l sfrom vapor di f f e r f rom Expe r i me nt M A - 0 8 5 ?

2 0 . T h e M A -085 sea led qu a r tz tube s c on ta i ne d t he source materia l , t het ransport gas, and the sma l l c rys ta l s forme d at the cool e n d . T he tube s we ntthrough 3-g de c e le ra t i on dur i ng A pol lo re e n t ry and s p l a s h d o w n , as w e l l ase xpe r i e nc i ng c onsi de ra b le v i bra t i o n . How mi g ht th i s t re a tm e nt a f fe c t the l a te rm e a s u r e m e n t s o f th e mass of c rys ta l s forme d?

2 1 . H o w m i g h t you get the c rys ta l s forme d f rom c he mi c a l va por in theM A - 0 8 5 E x p e ri m e n t t o grow in one place so tha t the y wo uld form la rgercrysta ls?

22. W h a t c o u l d be changed in the M A-028 reac tor to grow PbS c rys ta l s at afaster rate?

23. C rys ta l s forme d f rom c he mi c a l so lu t i ons in a gel ge ne ra l ly showstruc tura l defec ts . What could cause this?

2 4 . A fe w sma l l bubb le s (proba b ly a i r) we re i na dve r te n t ly lef t in one of theM A -02 8 re a c tors . T he y ha d l i t t l e e f fe c t on the forma t i on o f c rys ta l s , bu t the i rmot i ons we re fo l low e d on the pho togra phs ta ke n e very 12 hours . W ha t c ou ldbe learned from these motions?

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Appendix A

Discussion Topics (Answers to Questions)1 . (Sec. 2D) If s trong meta l f ibers w ere added to foa m in one -g , the

weight of the f ibers would probably col lapse the foam. I n zero-g, the foam h asto bear no gravi ty forces , but there is a problem in dispersing the f i be rsthroughout the foa m. A nothe r poss i b i l i ty is to ma ke foa ms of mol te n me ta l san d gas in zero-g. T he solidified metal foam could be a strong structuralmateria l o f lo w de ns i ty .

2 . (Sec. 2D) In zero-g, the oi l w e t t i n g the cup w i l l go over the top edgean d d o w n t he outside of the cup u n t i l it covers the entire surface.

3. (Sec. 2D) Th e adhesive force between the oi l and the wick f ibers iss tronger than the adhesive force be tween the water and the wick f ibers.

4. (Sec. 3G) One w a t t is 1 jou le / s ec . T h e r e are 10 800 s econds in 3 hours.T h u s , 205 w a t t s for 3 hours i s 205 x 1 0 800 = 2 .2 1 x 1 0 6 j o u l e s . Duri ngcool ing of the M A - 0 1 0 f u r n ac e , t h i s h e at escaped