Science in Orbit the Shuttle and Spacelab Experience 1981-1986

8/7/2019 Science in Orbit the Shuttle and Spacelab Experience 1981-1986

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Science in Orbit

Prepared byMarshall Space Flight CenterHuntsville, Alabama1988

NationaiAeronautlcs andSpace Administration


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Foreword~ "I-"-"" --

eviewing th e record of the Space Shuttle's first five years in service, one isR mpressed by the varied program of onboard research in space science andapplications. Th e Shuttle has hos ted hu ndr eds o f investigations in astronomy,atmos pheric science, Earth ob servations, life sciences, materials science, solarphysics, space plasma physics, technology, an d o the r scientific disciplines -investigations developed by scientists around the world. Equipped with th eSpacelab elements provided by the Europe an Space Agency, the Shutt le offersboth an enclosed laboratoly and an exp osed platform for investigations in space;crewmembers conduct o r moni tor the exper iments in a m anner s imi lar to work-ing in a laboratoly o n th e grou nd. T he S hutt le is a valuable addi t ion to t h e co m -plement of balloons, aircraft, sounding rockets, and expendable launch vehiclesthat are already available to space scientists.Individual new s releases and journa l articles have reported results of Shu ttle-era research o n a case-by-case basis, bu t this rep ort is a comp rehen sive overviewof significant achievements across all the disciplines and m issions in the first gen-erat ion o f Shutt le f l ights.

Altho ugh the act ivit ies reviewed and summarized in this report precede mytenure as Associate Administrator at NASA, i t is a pleasure for m e to acknowledgehere the dedicat ion and enthusiasm of the m any individuals in o ur gove rnmen tand academ ic insti tutions, as well as their many support co ntractors and interna-tional associates, wh o have ma de these successes possible. As we re turn theShutt le to spaceflight, I look fonvard not only to the renewed vigor of an activescience and applications program using th e Shutt le bu t also to the evolut ion ofspace science tow ard a new research capability - Space Stat ion.

L.A. FiskAssociate Ad min ima tor oySpace Science and ApplicationsJune 1988

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Prologuee are participating in a tremendously exciting and intellectually rewardingW ndeavor - he m erger of laboratory science and manne d spaceflight in the

adventure of mann ed space science.NASAs history flows in two main streams of activity - science and ma nnedspaceflight. These two streams ran in paral lel throu gho ut the 1960s, with thelaunch of many scienti fic satel l ites , on the on e ha nd, a nd, o n the other, thespaceflights that culminated in visits to the m oo n. T he s treams merged briefly inthe S kylab missions of 1973-1974, our highly successfd first experience in anorbi tal laboratory. Now, the Space Shutt le an d Spacelab bring science andmanned spaceflight togeth er in a union that com plements the scient i fic act ivi t iesof unman ned satell i tes and sets the s tage for m anned space science in a perma-nent Space Stat ion.

Science in the Shuttle era is a cooperative intern ational venture . Scientistsaroun d the world part icipate togeth er in planning, experiment dev elopmen t ,mission operations, an d resultant data analysis. A Spacelab mission is a multi-national forum of investigator groups dedicated to acquiring new kn owledge ina variety of science disciplines.an instrum ent o n a satel li te; science becomes m ore personal . Interact ionbetween scient ists on the gro und and the o nboa rd crew in cond yct ing experi-ments adds a new dimension to a science mission. It transforms th e mission froma focus on machines, electronics, and nameless bits of data to a human adventure.By mon itoring the experiment data s t ream, talking to the crew, and watching livetelevision fiom orbit, scientists on the g rou nd virtually work side-by-sid e withtheir col leagues in space. This close interact ion enables scientis ts on the groun dor in space to respond t o experiment results as they happen, adjust the experi-men t if appropriate, and m aximize the scientific retur n. M ann ed space science is avery special bridge that transports the scientist on the ground to space in a wayno t possible by other research methods .part icipate. T he emotional l if t of the launch, the rush of act ivi t ies during themission, and th e intensely personal col laborat ion w ith the onbo ard crew allcombine in to a unique experience, a high po int in our careers . This exhilaratingexperience affirms the importance and success of cooperative internationalmissions in manned space science.fession might be to take o ur research laboratories int o space and do our workthere. Th at is no t just an appealing p ossibility; i t is n o w a reality.

Doing science in the Shuttle and Spacelab is a different experience than having

Shuttle/Spacelab science is thrilling for all of us wh o have the oppo rtunity to

In my early years as a scientist, I speculated that the next big s tep in o u r p ro-

C.R ChappellAssociate Directorfo+ ScienceMarshall Space F&ht Center

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li_x -Skylab experience to develop experi-ments and equipme nt for flights o n the

SCienCe Missions: Half of the 24Shuttle flights from 1981 into 1986 - n d v&"a&,,es forSDaceShu ttle. carried major scientific payloads, 4 f ~~~ I _.^_1

Th e Shuttle/Spacelab combina tionoffers an alternative to the limitationsof unmanned spacecraft and an excit-ing variation o n th e Skylab concept.By perm itting scientists to serve ascrewmembers (payload and missionspecialists) and by providing variousexperiment accommodations, as in theSkylab era, NASA has merged sciencewith manned spaceflight. Interactive,"hands on" involvement is againpossible as the crewme mbers performexperiments, mon itor and respond toresults, and repair equipment whennecessary.With access to space via the Shuttle,scientists hope to accelerate the pace o fresearch. Instrume nts can be carriedinto space for 7 to 10 days, returned,modified and refined, and reflown onano ther mission. Reflight allowsinvestigators to use what they havelcarned from o ne mission to plan thenext. Furthermore, scientists can now

them Spacelabs, with more than 200investigations. The early sciencemissions were named after the NASAoffice that sponsored the payload (suchas the Office of Space Science/OSS)and o ften carried a payload with variedexperiments that tested th e Shuttle'scapabilities for doing space science.While not all Shuttle missions havebeen dedicated to science, scientificexperiments have been done on almostevery mission.Experiments have been successfiillyconducted in disciplines as diverse aslife sciences, materials processing, fluidmechanics, solar-terrestrial physics,astronomy a nd astrophysics, atmo s-pheric science, Earth observations, a ndbasic technology. Early results fromthese missions sugge st that the spec-trum of possibilities for scientificresearch in space is virtually unlimited.Du ring m ost of these missions, .experiment progress was monitored

Onboard experts who conduct and monitor ex-periments, maintain equipment, serve as testsubjects, evaluate data, and make decisions inmuch the same way that scientists work inlaboratories and observatories on the ground-Enough time in space to do significantmicrogravity experiments and accumulate dataAn experiment site in the ionosphere, allowingthe environment to be sampled and probeddirectlyAn obsewatoly base for a g/obal view of Earthand an unobscured view of the universe

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E#m-The ability to retrieve and return experimentsamples and equipment for ana/ysis on theground and possible reflightUse of larger; more capable instruments andnew techniques in spaceOpportunibes to perform pint experimentswith separate but complementaly instruments

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- - __Ww~-concentrate on w hat they do best -develop ing and perfecting investiga-tions - without also having to build aspacecraft to carry them .

instantaneouslv, In ''real time," byaudio and video communications withthe on board crew and by data trans-mitted to the ground.Scientists On

A testbed for new equipment and researchtechniquesE m w o r k between scientists in space and onthe ground through live voice and data linksbetween the Shuttle and the PayloadOperations Control Centel:Different experiments and different fieldscapitalize on one or more of these advan-tages to explore the unknown and extendknowledge beyond present limits, to learn bydoing and refining.

yr -*w /x *mm

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grou nd were able to begin immediateanalysis of the d ata from space, andthey participated actively in cond uctin gtheir experiments. It wa s not uncom-m on to hear cheers and applause in thePayload Operations Control Cen ter asresults came stream ing in with hints o fdiscovery.For a weck or more, excitementbuilt as teams of scientists an d m issionsupport personnel on the groundworked with the orbiter crew to takeadvantage of the unique researchopportunities in space. Th e onbo ardspecialists conc entrated o n ge tting themaximum yield from every preciou sminute. By the end o f a mission, milesof videotape, dozen s of samples, humdreds o f photographs , and millionsupon millions of bits of data wereaccumulated for study.O n the S huttle and Spacelab, scien-tific research has even greater imm edi-acy and intensity than that experiencedin a laboratory on the groun d. If an

experiment does not proceed as antic-ipated, scientists can interve ne, changeprocedures, adjust equipm ent, andrespond to the situation at hand. Thiscapability, not available since theSkylab era, gives LIS a new chance tomake discoveries that are beyond ourreach on Earth.Many scientists have invested a largepart of their careers in developingexperiments fo r flight. After flight, theyreap the rewards of a well-deservedperiod of analysis to glean new unde r-standing from the mass of dataacquired o n their mission. With ex pect-ancy, painstaking study , occasionaldisappointment, and eventual revela-tion, they are using space as th eultimate laboratory and observatory.significant results from Spacelab andother science missions on the Shuttledur ing its first 5 years in service. Tocreate a coherent picture, the resultsare discussed by discipline rather than

This report summarizes some of the

by mission; thus, an investigation maybe seen in the conte xt of similar orrelated investigations for a clearer senseof the aims and accomplishments ineach research field.These results herald the advancesthat are expected when scientists re-sume experiments o n th e Space Shuttleand later attain a perma nent presencein space on the Space Station.


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Spacelab and Other Major Science Payloads on the ShuttlePayload Flight DateApplications- 1 (OSTA- 1)Office of Space Science-1 (OSS-1) 5t5-3 Mar. 22-30, 1982Office of Space & Terrestrial 5t5-2 NOV. 12-14, 1981

OSTA 2Materials Experiment Assembly-A 1 5t5-7 Jun. 18-24, 1983(MEA-A 1)MA USSpacelab 1Office ofAeronautics & SpaceTechnology-1 (OAST- 1)

$acelab 3Spartan 1

-- --.OSTA-3

Spacelab 2

5t5-941-041-G51-651-G51-F

Spacelab D1 61-A

Nov. 28-Dec. 8, 1983Aug. 30-Sep. 5, 1984Oct. 5-13, 1984Apr. 29-May 6, 1985Jun. 17-24, 1985JuI.2 9 - A ~ g .6, 1985Oct . 30-NOV. 6, 1985Materials Expe riment Assembly-A2

AS /ACCESS 61-B Nov. 26-Dec. 3, 1985Materials Science Laboratory-2 (MSL- 2) 67 -C Jan. 12-18, 1986Goddard Hitchhiker- 1 (HH-G1)Middeck experiments, student experiments, Get-Away-Specials, and Detailed SupplementaryObjectives are not included in this list, but they have contributed to the body of scienfific dafa andhave stimulated {deas and tested equipment and techniques for expanded investigations.

(MEA-A2)

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Chapter 2

Living andWorking inSpace:Life Sciences

esearch in space has given usR antalizing glimpses into the na tureof life and the influence of gravity onliving things. In space, scientists havebeen able to examine how life adaptsto a different environment and therebygain new knowledge about basic lifeprocesses on Earth.Early life sciences experiments inorbit raised many questions about howthe interrelated systems of the humanbody and oth er living organisms reactto microgravity. How does the humanbody adjust as microgravity causes fluidto shift toward the head? D o musclesand bones degrade without the forceof gravity to work against? Wh at causessome people to experience symptomssimilar to motion sickness during thefirst few days in space while others haveno symptoms? How do plants behavewhen there is no u p or down? Do cellsreproduce and synthesize materialsnormally in space? Wh at are the conse-quences o f these reactions? If responsesto the space environment are undesir-able, how can we prevent or controlthem?Th e Shuttle/Spacelab facilities havegiven scientists increased op portu nitiesto explore these and many otherquestions. Investigators are studyingdiverse life forms from cells to wholeorganisms, including the human bodywith its many complex systems. TheSpacelab module offers enough roomfor various experiment apparatus andan environment with regulated tem-peratures and pressure. To maximizescientific return, the space laboratolyequipment includes modified standardmedical tools, multipurpose reusableminilabs, and plant and animalhabitats.module accommodates a stiff ofMost importantly, the Spacelab

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trained scientists. Life science researchin space deman ds heavy crew involve-me nt as expert investigators, test su b-jects, and laboratory technicians.Crewmembers draw and process bloodsamples, record their ow n physiologicalsymptoms, set up and participate in avariety of experiments, tend plant andanimal experiments, and carry on theirwork m uch as they d o in laboratorieson th e grou nd. Detailed research inthis field was very limited until theShuttle and Spacelab made a mannedlaboratory in space possible.to date have synergistic results. Physi-ology experiments o n various parts ofthe body, such as the heart, muscles,and bones, are all related becausechanges in one part of th e body cause aripple effect inducing changes else-where. The human and animal studiesoften parallel each other as scientistsattempt to determine whether thechanges occu rring in animals are simi-lar to those observed in humans. Ifanimals can be used as models forpeople, the number and type of studiescan be increased because more subjectswill be available.Oth er experiments explore funda-mental questions in biology by study-ing life - rom single cells to complexorganisms - n the microgravity

Many of the experiments performed

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Living and Working in Space

environment. This knowledge can betransferred to the m edical and biologi-cal communities to improve the qualityof life on Earth. If cells can reprod uceand synthesize materials normally orbett er in weightlessness, som e of theirproducts that are ofcommercial andpharmaceutical importance may beproduced in purer forms in orbit.Many important biological moleculeshave never been structurally analyzedbefore, but in microgravity it may bepossible to produce protein crystals,for example, that are large and pureen ou gh for m ore precise analysis.This vigorous inquiry into the na-tu re o f life meets NASAs major goals:


to ensure the safety and comfo rt ofpeople living and working in space,enabl ing even long er stays in space,an d to explore the fiindamental natureof life in the universe. Sh uttle exp eri-ments have begun to confirm somegenerally held hypotheses a nd also havesurprised investigators with unexpectedresults. At this point, we have gleanedonly nugg ets o f information, pieces ofa puzzle that must be worked o utduring future comprehensive investiga-tions. T he harvest of life sciences datafrom the Shuttle and Spacelab missionscontains the seeds for more complex,long-term experiments aboard th eSpace Station.

PhySiQlQgy:M e r m o re t h an 25 yearsof spaceflight, life scientists remaineager to study the body and its healthybut somew hat changed functioning inspace. Th roug h centuries of evolution,the hum an body has adapted togravitys deman ds in countless su btleways. In the absence o f gravity, thebody undcrgoes noticeable physiologi-cal changes: blood and body fluids areredistributed, affecting the circulatoryand endocrine systems; muscles andbones begin to deteriorate; and somesensory signals are scrambled.Scientists are seekin g to understandthe various bodily responses to space-flight. Many Shuttle/Spacelab experi-ments attempt to test o r confirmtheoretical explanations of how thebody reacts in space and why. Inmicrogravity, the body is in a state offree fall and reacts as if there is nogravity. According to one current hy-pothesis, th e absence o f gravity results

in a redistribution o f fluids to th eupper body ; this adversely affects thehomeostatic mechanisms that co ntrolthe cardiovascular, endocrine, andmetabolic systems. A reduction offorces on the body niay explain themuscle an d bone degradation that hasbeen observed in space crews andanimal test subjects.spaceflight tha t remains a mystery isthe discomfort similar to motion sick-ness that about half of space crewsexperience d uring their first few days i n

Another physiological response to

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space. Scientists theorize th at norm alsensory and m otor cues from the ves-tibular system in the inner ear, theeyes, and the nervous system are al-tered in microgravity an d may conflict.For example, the eyes may send onemessage about body orientation whilethe inner ear sends another. As th eperson adapts to microgravity, thebrain learns to reinterpret or ignoreconfusing signals.Non e of the findings to da te provesthat the bodys responses are patho-logical. Som e appear to be appropriateand effective ways to adapt to a newenvironment. Othe rs such as the im-mune response and muscle and b onedegradation must be studied in greaterdetail duri ng long er missions. Scientistsmust not only identify detrimentalresponses bu t also find ways to preventsuch responses so tha t crews can bequalified for long -term space missionsaboard the Space Station and th roug h-ou t the solar system.card~OVaSCu/arm e m ; On Earth,the parts of th e cardiovascular system(the heart, lungs, and blood vessels)work together in a stable state of equi-librium. In weightlessness, blood andoth er fluids are redistributed to th ehead and upper body. In response tothe fluid shift, the bodys normalhomeostatic mechanisms appear toadjust the operation of the heart andother parts of the body.Fo r Spacelab research, an instru -me nt was developed t o record changesas the heart adjusts to microgravity.Called an echocardiograph, the instru-men t generates two-dimensionalimages by interpreting high-frequencysound waves directed at the heart. It

was tested during Shuttle mission 5 1-Din April 1985 when real-time images offour crewmembers hearts revealedmajor cardiovascular adjustments dur-ing the first day of spaceflight. The leftside of th e heart (which propels bloodthrough the circulatory system)reached its maximum size, as did th eblood volume it pumps, o n the firstday; the right side of the heart (whichcollects blood returning from the restof the body) was smaller than whenimaged preflight. By the second dayof the mission, the entire heart wassmaller and subsequent changes pro-gressed more slowly. Th e reduction inthe left heart volume remained un-changed for at least 1 week after returnto Earth.From these observations, investiga-tors concluded that the cardiovascularsystem adjusts quickly to fluid shiftsand blood volume loss during space-flight. Results from a French echocardi-ograph flown o n the 51 G missionconfirmed the U.S. observations on the51 -D mission. Mo re extensive tests areneeded to determine if the decrease inheart volume is associated with anyreductions in heart performance. AU.S. echocardiograph is scheduled to

be flown again with com plementaryinstruments on a mission dedicated tolife sciences research.be linked directly to fluid shifts, it isimportant to track the time course offluid shifts in microgravity. One way tomeasure changes in the amo unt of fluidin the upper body is to measure corre-sponding changes in the circulatorysystem. As fluid volume increases, sci-entists have predicted that more pres-sure than usual should be exerted onthe up per body veins; as upward fluidflow decreases, the p ressure sho uldequalize. Spacelab 1 investigators triedto determine the degree and rapidity ofthe fluid shift by measuring centralvenous pressure in th e arm veins offour crewmem bers. Before this mis-sion, no direct m easurements of ve-nous pressure were available to test thehypothesis.Surprisingly when venous p ressurewas measured 22 hours into the mis-sion, it was lower, not higher, thanpreflight measurements. On e hourafter landing, ven ous pressures werehigh for all four crewmembers, indicat-ing fluid shifts associated with thebodys readaptation to Earth.

Since changes in th e heart appear to

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1ving and Working in Space

This experiment was repeated usingfour different subjects on the SpacelabD1 mission with measurements madeas early as 20 minutes after launch.Even with early measurements, thevenous pressure was still lower than thepreflight measurements, confirmingthe Spacelab 1 results. The investigatorwas astonished at th e low pressu re levelso early in the mission before anydehy dratio n was possible.From these results, investigatorsconcluded that the fluid shift is ahighly dynamic process that may occureven before launch when crewmembers

spend about 2 hours seated in theShuttle on the launch p ad. To confirmthis hypothesis, investigators want tomake measurements d urin g this wait-ing period alon g with measurements ofhormones that regulate fluid balance.A novel device for noninvasively meas-uring venous pressure may help clarifyth e profile of fluid shifts by enablingmore frequen t and convenient meas-urements. Limited m easurements withthe device, which was tested on the61-C mission, confirm the Spacelab 1and Spacelab D1 results.

Hematology and Immunology: Re dblood cells, which are th e focus of thehematology studies, transport oxygenthroughout the body. Spaceflight stud-ies indicate th at red blo od cell mass isreduced in microgravity. Several th eo -ries as to why this happens have beendeveloped. On e of the mos t generallyaccepted is that bone marrow hn ct io nis inhibited; this results in the su ppres-sion of erythropoietin, a hormone thatstimulates red blood cell creation.A Spacelab I investigation studiedthe relationship between decreases inerythropoietin an d red bloo d cell massby analyzing bloo d samples from fourcrewmembers taken before, during ,an d after flight. While there was a sig-nificant decrease in red blo od cell massand reticulocytes, erythropoietinseemed n ot to vary significantly. Mo restudies are needed to determine if thebody destroys red b lood cells or ifothe r mechanisms influence red b loodcell counts.An othe r important type of cell,lymphocytes (white blood cells), mayalso be altered in microgravity. Lym-phocytes help the body resist infectionby recognizing harmful foreign agentsand eliminating them . Some evidencefrom previous space studies suggeststhat the nu mber and effectiveness ofwhite blood cells are reduced in spacecrews, and thus the ability to fight in-fection is altered. However, astronautshave no t shown an increased suscepti-bility to disease, and lym phocytecounts return to normal a few weeksafter landing.An experiment flown o n Spacelab 1and repeated o n Spacelab D1 contrib-uted substantially to the understanding

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,s, :_ of the imm une system's operation inspace. Before white blood cells canrecognize a harmful substance andmultiply to eliminate it, the cells gothrough a process called activation inwhich they identifi the foreign sub -stance, differentiate to enable the pr oduction of.the appropriate antibody,AG- 7 6 at410


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and finally proliferate to produce suffi-cient amou nts of the antibody.Imm une cells cultured du ringSpacelab 1 lost almost al l ability torespond to foreign challenge. Culturesgrown in space and controls grown onthe ground were injected with mito-gen, an agent that causes lymphocytesto activate and reproduce rapidly tofight infection. Proliferation of th eflight lymphocytes was less than threepercent of that for grou nd lympho-cytes. Althou gh the flight cells wereclearly alive, they did not activate andrespond to the stimulus.This experiment was repeated onthe D 1 mission with cultures exposedto microgravity, cultures o n a 1 g cen-trifuge, and with blood taken from thecrewmembers during the mission.Cultures grown on the 1- g centrifuge,which simulates terrestrial gravity, wereimportant controls because other fac-tors besides microgravity (such asradiation) were still candidates for al-tering th e cells' response. The samplestaken from the crew were importantbecause only cultures of lymphocyteshad been studied during Spacelab 1.Th e Spacelab D1 results confirmedthe Spacelab 1 results: cell activation inthe cultures exposed to microgravitywas depressed when compared to

1 g centrifugecultures

control cultures o n th e centrifuge ando n the ground. Since cells on the 1 -gcentrifuge responded normally, itappears that microgravity is the d omi-nant factor inhibiting cell activation inspace. In ad ditio n, activation of lym-phocytes from th e crewmembers wasmarkedly depressed in samples taken inflight as well as in sam ples drawn anho ur after landing; the activation proc-ess in crewmembers' wh ite blood cellsdid not fully return to normal until 1to 2 weeks after landing.that microgravity almo st completelyinhibits the process of lymphocyteactivation. In co njunction with otherSpacelab D1 results indicating in-creased proliferation and antibioticresistance of bacteria in microgravity,these results suggest a risk o f infectiousdisease, which must be taken seriouslyin planning spaceflights. Th e next stepis to discover which stage of th e activa-tion process is affected and determineif the effect can be prevented.men t indicates that immunoglobulins(key antibodies) appear to functionnormally in space. In blood samplesfrom four crewmembers, only minorfluctuations in quantity were measuredwith n o significant effects recordeddurin g the 10-day flight. From theseresults, one might conclude thatactivated lymphocytes continu e toproduce antibodies during prolongedweightlessness and are not affected bymicrogravity. However, microgravitymay impair the lymphocyte activationprocess, altering the im mun e system'sability to respond to challenges.

These two experiments made it clear

A complementary Spacelab 1 experi-

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Musculoskeletal System: T hemuscles and bones, the support struc-ture of the body, evolved under t heinfluence o f gravity an d now requiregravity for normal functioning. In theabsence of gravity, muscles may dete-riorate and bones may become smallerand weaker. Previous space crews haveshown loss of lower body mass, es pe-cially in the calves, decreases in m usclestrength, and negative calcium bd-ances. The process occurrin g in spaceresembles the initial phases of som ebone diseases o r the wasting away ofmuscle and bone observed in bedrestpatients. Thus, a better un derstandingo f this process in space also will aidresearch on Earth.Durin g the Spacelab 2 mission,investigators measured vitamin Dmetabolites, which regulate calcium inthe bones and blood stream. Threevitamin D metabolites were measuredin blood samples taken from fou r

crewmembers before, during, and afterflight. Levels of two metabolitesremained essentially unchanged. How-ever, the level of a third m etaboliteunderwent an interesting pattern: therewas a rise in the level in blood samplescollected early in the mission, whichdrop ped in samples taken o n missionday six and returned to normal post-flight. Measured values remainedwithin a normal range a t all times, butthe pattern exhibited in all four crew-members needs further examination.Durin g the Spacelab 3 mission, 24rodents and 2 squirrel monkeys alsooccupied the spacecraft. They residedin a n animal habitat de signed especiallyfor space and were retu rned to Earthunstressed and in good health, butsome physiological changes attributedto weightlessness were observed.Spacelab 3 studies of the rodent mus-culoskeletal system confirmed some ofthe changes, such as reduced muscle

mass in the legs, that also have beenreported by astronauts. Some of themost notable phenomena measured inthe rode nts were a dramatic loss ofmuscle mass, increased bone fragility,and bo ne deterioration. As withhum ans, the lon g gravity-sensitivemuscles in the rod ents legs and spinesseemed to be most affected; some legand neck muscles lost up to 50 percentof their mass.

A horm one change measured in therode nts may be associated with th eobserved loss of muscle and retardedbone development. Although th epituitary glands of these animalsshowed an increase in grow th hormo necontent, the release of the horm oneappeared to be impaired. This resultedin substantially lower grow th ho rmon esynthesis for flight rats than for gr oundcontrols. Such indications of a responseto microgravity at a cellular level areintriguing and require furtherinvestigations.

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Neufovestirbu/af sysfem: The neu-rovestibular system, which includes ou rreflex, vision, an d balance organs,appears to be very sensitive to gravity.Space motion sickness, which has af -fected ab out half of al l space travelers,may be a result of this sensitivity.Symp toms of space sickness includelack of appetite, nausea, and vomiting.Symptoms are similar to motion sick-ness, bu t scientists are unsure if thestimulus is the sam e because crew-members who are susceptible tomotion sickness o n Earth may no t ex-perience space sickness and vice versa.There is still no go od m odel for pre-dicting whether individuals will experi-ence discomfort as they adapt to space.Luckily the body adapts quickly,and the most severe symptoms occurduring the first days of spaceflight.Although some medications have beenused successhlly t o reduce the symp-toms, n o treatm ent eliminates thesediscomforts. Experiments have focusedon identifying the underlying causes ofthe problem a nd ways to treat it.

During th e Spacelab 1 mission, agroup of complementary experimentssponsored by American, Canadian, andEuropean scientists studied the ves-tibular system from a variety of anglesto determine how the sensory moto rsystem adapts to weightlessness. Th isresearch focused o n the inner earorgans (especially the oto liths) whichsense gravity and linear acceleration.Th e experiments also examined theinterrelated hnctioning of the innerear, vision, and reflexes - all of w hichhelp us orient ourselves.Before the mission, investigatorsproposed a sen soy conflict theory:in microgravity, information sent to th ebrain from th e inner ear and othersenses conflicts with the cues expectedfrom past experience in Earths 1-genvironment, resulting in disorienta-tion associated with space adaptationsyndrome.

of brarn B& l i E Y r &%Wy 2nd E&? agrd h ~ ~ r im o v m e n h . &strlfs irrdicets ~ P Ce& n i o ~ e -mmts and ~ i w g l ~ ~ ~ f ~ ~ ? ~ i ~ ~ ~ ~fov&z spc?nothion s k k m s .During the Spacelab 1 mission,three of fo ur subjects developed spacemotion sickness. Th e astronauts m adedetailed reports on the time course ofsymptoms while their head movementswere monitored with accelerometers.These reports were the first detailedclinical case histories of space sicknessavailable for study. As expected, headmovements were reported to provokeepisodes of space sickness, bu t th eSpacelab 1 crew also documented theimpo rtant role played by vision in theadaptation process. Crewrnembersfrequently experienced a spontaneouschange in perceived self-orientation ifthey reinterpreted the location of vari-ou s static landmarks or if another crew-member came within view in anunfamiliar orientation. As with headmovem ents, these visual reorientationepisodes provoked space sickness.These findings fit the sensory conflict

theory, which predicts confusion overactual versus expected sensory cues.Ot her experiments examined differ-ent outputs to reveal how the centralneivous system adapts to microgravityA rotating dome, a drum with dotpatterns that fits around the face andproduces a sensation of bodily motion,

was used to stimulate eye movementsand body reactions. Subjects reportedstron ger visual effects in space than o nthe g roun d, which suggests a greaterreliance on vision while signals fromthe otoliths are ignored or reinter-preted,O n th e 41-G and Spacelab 1 mis-sions, subjects experienced some visualillusions as they performed prescribedmovement tests. Other tests measuredthe subjects changes in perceptionwhen blindfolded in weightlessness.When crewmembers viewed varioustargets and the n pointed a t them whileblindfolded, their perception of targetlocation was very inaccurate in flightcompared to similar tests on th egrou nd. I n a test of the ability to per-ceive mass in microgravity, subjectswere much more inaccurate in predict-ing masses in weightlessness than inpredicting weights and masses inpreflight tests.The hop and drop experimentsstudied the otolith-spinal reflex whichnormally prepares one for landing froma fall. Surface electrodes over th e calfmuscles recorded neuromuscularsignals du rin g simulated falls (accom -plished in weightlessness by attaching

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elastic cords to the crewman to pullhim downward). The normal reflex wasinhibited when tested early in flight,declined fiirther as the flight pro-gressed, but returned to normal duringtests conducted immediately after land-ing. Again, this suggests that in micro-gravity the brain ignores or reinterpretsotolith signals.Spacelab 1 experiments studying thevestibulo-spinal reflex mechanismsmeasured c hanges in th e spinal reflexesand posture associated with the ves-tibular system. Th e subjects' physio-logical responses to standard postureand reflex tests were reco rded. Resultsof these tests indicate that posture ismodified dramatically in weightless-ness, and t he individuals whose centra lnervous systems are better able tomodify response patterns may experi-ence less severe sym ptoms of spacemo tion sickness. A related French ex-periment o n the 51- G mission revealedrole of vision durin g postural control.Prc- and postflight Spacelab 1 testsusing a sled to accelerate subjec ts alonga linear path indicated that subje cts hadan increased ability to perceive linearmotion after exposure to niicrogravity;this seems to indicate that signals sentfrom the o toliths, which sense bothgravity and linear acceleration, come tobe interpreted by the brain as on lylinear motion.

To increase the number of subjectsfor statistical studies, som c of th eSpacelab 1 experiments were m odifiedand reflown aboard the Spacelab D1mission. The se included the spacemotion sickness studies, the rotatingdom e experiment, and the hop anddro p experiment. Although theSpacelab D1 results are still being an a-lyzed, they generally confirm theSpacelab 1 findings.

Ichanges '11 muscle movement and th e sm$s 2n d ;j fjfi'insaracccj2raifofi $1,~centa7i;islcQir 'nlodrr~r?~rj arbit for the f j r i ; iifne.

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ORIGINAL PAGPQ P'-'?TClr YAPH

A sled developed by the Europ eanSpace Agency was flown in space forthe first time o n the D1 mission. Whe nsubjects were accelerated on the sled inflight, with out t he influence o f gravity,they had smaller increases in sensitivityto linear motion than the investigatorsexpected. Postflight D I sled experi-ments confirmed the earlier Spacelab 1postflight sled tests, with subjec ts con-tinuing to show slight increases insensitivity to linear accelerations.Spacelab 3 results indicated thatothe r mammals may also experiencespace motio n sickness. Th e two mon-keys flown o n th e m ission were care-fully observed by trained biologists.Th e monkeys' patterns of food intakeand behavior indicated th at while oneanimal reacted normally throughoutthe mission, the oth er had low foodconsump tion for the first four days offlight followed by recovery during thelast three days of the mission. Bo thmonkeys' behavior and food consump-tion were normal u pon landing. Thissuggests tha t squirrel monkeys mayserve as good surrogates for studyingspace mo tion sickness.Another Spacelab 3 experimenttested the effectiveness of the com-bined use of autogenic and biofeed-back training as a countermeasure tospace motion sickness. Preflight, twocrewmembers were trained to gainvoluntary control of their heart rate,skin tempe rature, a nd finger pulserates. Two othe r crewmembers whoserved as controls did not receive train-ing. During the flight, each of the fourcrewmembers wore an undergarme ntequipped with electrodes and sensorsfor measuring heart rate, body tem-perature, skin response, and breathingrate. For the first time during a Shuttlewere recorded continuously during theastronauts' working hours.

i flight, these physiological parameters

Alth ough the statistical sample issmall, postflight analysis of crew logsand physiological d ata indicate tha t onecrewmember who learned to controlthe m otion sickness symptoms withautogen ic feedback training preflightwas able to use these skills to controlminor symptoms experienced in flight.This crewmem ber never developed anysevere symptoms du ring th e mission.Th e othe r crewmembcr who dcm on-strated less skill with t he au togenicfeedback training technique reportedone severe episode of space motionsickness. The two control subjects(wh o took anti-motion sickness medi-cation) reported multiple symptomepisodes durin g the first day of themission. Sym ptoms for all four subjectssubsided after th e first day in space.Mo re subjects need to be tested, butinitial results seem to indicate tha tpreflight improvements in motionsickness tolerance can be used to pre-dict success in contro lling symptomsin flight.

Microgravity also enabled investiga-tors to make a discovery abou t theinne r ear. Since th e last century, it hasbeen known that irrigation of the earcanals with water at a tem peraturehigher or lower than body temperaturecauses nystagmus - apid involuntaryeye movements. This test is importantfor the clinical diagnosis of sensoryproblems. According to previous the-ory, these eyc movements are causedprimarily by therma l convection influid in the semicircular canals of th einner ear. In space, it is possible to testthis hypothesis since thermal convec-tion is inhibited by the virtual absenceo f gravity. Wh en the test was done withtwo subjects during Spacelab 1, bothresponded with eye movements. Thus,the presence of caloric nystagm us inmicrogravity demonstrates that mec ha-nisms other than thermal convectionare involved.

ORlGlNAL PAGE

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Fundamental Biology: By study ing lifein a microgravity environm ent, scien-tists can see functions that are maskedby gravity o n Earth . Space is a go odlaboratory for determining what rolegravity plays in certa in basic life proc -esses. These experiments contributesignificantly to our understanding oflife as well as to the fundamental bankof biological and medical knowledge.Celhlaf Functions: The functions andprocesses of single cells as well as trans-actions between cells often lead tochanges on a larger scale in an organ -ism. This was evident in th e whiteblood cell experiments described ear-lier, which suggested that responses bythese cells to microgravity m ay alterthe human immune systems ability to

fight infection. Even the study of thesimplest life forms such as bacteria candemonstrate how cells respond tomicrogravity and other conditions ofthe space environ ment. Spacelab isideally suited for cellular studies be-cause samples are small enou gh to beobserved and manipulated in relativelylarge numbers, and they can be pre-served and returned to Earth fordetailed analysis.Th e Spacelab D1 Biorack experi-ments have provided striking evidenceof th e effects of gravity on bacteria,unicellular organisms, an d white bloodcells. Fourteen cell and developmentalbiology experiments were carriedaboard the Biorack, a reusable facilityequipped with incubators, coolers/freezers, and a glovebox for safely

preserving specimens in orbit. T he D1mission was the first Spacelab missionin which specimens were Yixed inorbit; this fixation allows specimens tobe preserved while they are und er theinfluence o f microgravity an d elimi-nates influences such as accelerationsdurin g landing and adaptation uponreturn to Earth. To further isolate theeffects of microgravity from o the rspace conditions (radia tion , vibrations,launch, and landing), most of the D 1experiments used controls in 1-g cen-trifuges that simulate terrestrial gravity;thus, effects seen in microgravity speci-mens that are no t seen in 1- g speci-mens may be more strongly linked togravity.Several Spacelab D 1 exp erimentsstudied bacteria, the simplest life formon Earth. U nder favorable conditions,these single-celled organisms, no tmuch more than one thousandth of amillimeter in length, reproduce rapidlyby repeated cell divisions. This rapidreproduction makes bacteria excellentfor studying cell development andproliferation.an observation made on several previ-o u s flights: bacteria reprod uce morerapidly in space. Thi s finding suggeststhat in space humans may be exposedto greater risks of infection. This addi-tional risk also is suggested by anotherD 1 experiment with E. coli, a commonpathogenic organism. Under micro-gravity conditions, the bacteria showedan increased resistance to antibiotics.influence bacteria reproduction alsomay prove useful. Some bacteria have aprimitive form of sexual behavior inwhich two cells exchange genetic mate-

Two Biorack experiments confirmed

Th e fact that microgravity seems to

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rial through a physical bridge betweenthem. A laboratory techniqu e derivedfrom this phenom enon can be used tointroduce human genes - or example,genes needed for insulin production -into bacteria that then can synthesize auseful product. A Spacelab D1 experi-ment showed that this transfer of genescan occur three t o four times faster inmicrogravity than in 1-g ; in space,bacteria may be able to produce bio-logical products more rapidly.Cell differentiation, the process bywhich originally similar cells acquire

differen t capabilities, was studiedaboard Spacelab. In higher organisms,this process leads not only to the pro-duc tion of cells as different as skin andnerve cells but also to the productionof cancer cells from normal cells.Under certain conditions, manybacteria become dorm ant by formingspores, which are genetically identicalto the active form but fimction differ-ently. This makes sporulation a simplemodel for studying cell differentiation.A Spacelab D1 experimen t observed areduction in sporulation and thus dif-ferentiation for bacteria. However, th e1- g centrifuge co ntrol for this experi-ment failed, and therefore the experi-ment needs to be repeated to deter-mine whether the reduction was due tomicrogravity or othe r space conditions.Many organisms o ther than bacteriaconsist of single cells, but the cells aremuch larger (10 to 100 times the sizeof bacteria) and more complex, pos-sessing a variety of internal stru ctu resthat perform most o f the functions ofthe organs of higher animals andplants. Like bacteria, many o f theseorganisms proliferate via repeated celldivision. Tw o experiments, one with

paramecia and one with green algae,revealed that, as with ba cteria, micro-gravity increased the rate of cell prolif-eration . In microgravity, the parameciaincreased four times faster than thecontrols. The investigator hyp othe-sized that since the paramecium is aswimming cell, it may use less energyfor movement in microgravity and usethe extra energy for other activitiessuch as cell proliferation.Developmental ~ ~ O C e s s e S :Micro-gravity may affect the development oflife from embryo to adult. O ne Biorackexperiment with the m uch-studiedfruit fly revealed th at m icrogravityreduced the rate of development ofeggs to 10 percent of the normal rate.Surprisingly, the total num ber of eggslaid was higher, but the hatching anddevelopm ent rates were reduced. Thelifetime of each fly also was measured.While th e female flies had th e same lifespan as th e control g roups, the lifespan of th e m ale flies was reduced byone-third. This phenomenon needs tobe studied more to determine whethersho rter lives may be related to the gen-eral speeding -up of vital processes ob -served in u nicellular organisms.Developm ent also seemed to beinhibited in suck insect eggs. Duringdevelopment, this insect passesthrough several stages differing inradiation sensitivity. Layers of eggs atfive different stages of developmentwere sandwiched between radiationdetectors so that investigators coulddetect heavy ions of high energy andcharge as they penetrated an egg. Thisallowed investigators to study the ef-fects of microgravity and radiation ondevelopment.

The response to the spaceflightenvironment varied depending on thestage of development of the eggs.When eggs at late stages o f develop-ment were hit by a radiation particle,they tended to develop normally.However, a significant reduction ordelayed hatching occu rred in eggs thatwere in an early developmental stagewhen hit by a particle. Developmen twas impaired t o a lesser extent in thoseeggs that were developed in micrograv-ity but were not hit by a particle.Hatch ing was normal for both hit andnon-hit eggs on the 1-g centrifuge,indic ating a difference in radiationresponse de pend ing o n gravity envi-ronment. During development of thelarvae, additional damage - uch asreduced life span and increased bodyabnormalities - was observed in indi-viduals hatched from radiation-exposedeggs in the microgravity samples.Another experiment studied thedevelopment of the vestibular systemin tadpoles hatched in space. On Earth,most species develop organs to orientthemselves in a gravitational field andcoordinate movements. Tadpoleshatched from frog embryos flownaboard th e Spacelab D 1 missionshowed pronounced alteration inswimm ing behavior upon return toEarth. They swam in small circlesaroun d tixed centers until their behav-ior normalized two days after landing.Later examination of the mo rphologyof the tadpoles vestibular gravityreceptors revealed n o structural de -formities, indicating that the vestibularsystem developed normally for theembryos in space. These results corre-spond with earlier experiments onamphibians and rod ents.

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Circadian Rhythms: O n Earth, mostorganisms have behavior patterns thatcorrespond to 2 4- ho ur cycles. Debatecontinues over whether these circadianrhythms are regulated by internal bio-logical clocks o r by outsid e influencessuch as day-n ight cycles, seasonalchanges, gravity, or the Earths ro ta-tion. For a spacecraft orbiting Earth,there are 16 sunrises and sunsets in a24- hou r period, the Earths rotationand seasons are eliminated, and there isvirtually no gravity. This gives scientiststhe opportunity to examine circadianrhythms in the absence of normalexternal cues.

During Spacelab 1, the biologicalclock theory was tested by examininggrowth patterns of neurospora, a com -mon hn gu s. If cultures of neurosporaare transferred from constant light toconstant darkness, a distinct bandedgrowth pattern is evident that indicateswhen vegetative spore formation oc-curs. This experiment produced som econfusing but interesting results. Thepattern of cultures grow n in space wasvisibly different from the culturesgrown o n Earth. Grow th rates andcircadian rhythms varied among theseven cultures grown in space, and th eclarity of the banding pattern wasreduced. H owever, after the cultureswere moved for marking and exposedto light, robust rhythms were evidentin all the sample tubes. The clear pat-tern seen in all cultures after the tubeswere marked proves that the rhythmcan persist in space. The dam ping o utof the pattern d uring the first 7 days ofthe mission indicates that outside fac-tors probably d o influence the biotogi-cal clocks expression.Tw o Spacelab D 1 experiments con -firmed the observation that the clockworks in a low-gravity environmentfree of terrestrial signals. In an experi-men t with green algae, the algae con-tinued to display patterns in a specificrhythm while in microgravity; however,unlike the Spacelab 1 neurospora, thepatterns werc more prominent in lowgravity and damped ou t more slowly.In another experiment, investigatorsrecorded the movements of a single-celled slime mold that moves withregularly timed oscillations on Earth.In space, the protoplasm of the slime

mold moved with the same biologicalperiodicities, indicating the operationof the biological clock, but the behav-ior was somewhat altered with thevelocity of the protoplasm increasing inmicrogravity.p/anb: From preliminaly Shuttle/Spacelab expe riments, b iologists havelearned about the fundamental behav-ior of plants and how to grow andmaintain them in orbit . Sunflowerswere th e first plant to be flown aboardthe S huttle; on ST S-2 and STS-3, sun-flowers were grown to test a new plantgrowth apparatus and at the same time

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ORIGINAL PACTCOLOR PHOTOGRAPH

confirm that water delivery to plants isbasically the same in microgravity as onEarth.For the Spacelab 1 mission, sun-flowers were studied again to resolve aque stion ab out a peculiar circulargrowth movement called nutation.As plants grow on Earth, their tipsdescribe a helix aroun d a central axis.Plant physiologists have wond eredwhether this movement depends o ngravity or o n an internal grow th m ech-anism. Theories predicted that nuta-tion would virtually cease in micro-gravity. During Spacelab 1, plants wereobserved by time-lapse video, and thenutation proceeded. Although thenutation of the microgravity plantsvaried somewhat from the groun d co n-trols, the fact that nuta tion occurredsuggests that t he response is influencedby other mechanisms rather thantriggered by gravity alone.oats, and pine seedlings were con-ducted o n two Shuttle flights (STS-3and Spacelab 2) . These experimentsstudied the ability of plants to synthe-size lignin, a structural fiber that plantsuse to grow upright against gravita-tional force. Lignin, though useful fo rrigidity, is difficult to digest and isdetrimental in some industrial proc-esses such as making paper. Scientiststhink that if lignin content could bereduced in some plants, the plantswould make better food and industrialproducts.During the S TS-3 mission, pineseedlings and oats grown o n theShu ttle showed n o significant decreasein lignin, but mung beans had an aver-age 18 percent less lignin than groun dcontrols. When the experiment wasmodified slightly and repeated aboardSpacelab 2 with oats, mung beans, andsome more mature pine seedlings, allthree species showed significant reduc-tion in lignification. For the pine seed-lings and mung beans, there was adecrease in enzymes associated with

Plant experiments with mu ng beans,

1

iI#

M

lignin synthesis as well as a slight over-all growth reduction for the stems andleaves. To see if this trend continues oris enhanced with plant development,this experiment should be repeatedwith more mature plants.Interesting plant behavior was alsoobserved: many of the mu ng beans andoats had roots emerging upward o ut ofthe soil. This indicates th at, in th eabsence of gravity, plant growth maybe disoriented. The mechanism bywhich plants know which way to growis still a matter o f controversy. In aSpacelab D 1 experiment, lentil seedswere germinated in microgravity andon a 1-g centrifuge. Th e microgravity-grown roots grew down in to the soilbut were no t oriented correctly. Ho w-ever, the plants demonstrated that theability to sense gravity-like accelera-

tions was not permanently lost. Whenplaced on a 1-g centrifuge, the plantsoriented their roots in alignment withthe accelerations.For maximum benefit, tissues fromthe sunflowers, oats, and m ung beanswere shared with oth er scientists forsome interesting genetic and structuralstudies. Chrom osomal studies of thesunflower and o a t root tips showedseveral abnormal chromosomes anddepressed cell division. Plants growno n the ground had twice as many cellsin division as the plants g rown inflight. The oats had broken and frac-tured chromosomes more severe thanany in ground controls. These resultsindicate that microgravity and/orother spaceflight conditions, such asradiation, may damage the cell'sgenetic material.

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Living and Working in Space W A C PAGEPHOTOGRAPH

aspects of thc space environment suchas high radiation and vacuum aftect lifein space. Th e hazardous environmentof space includes unfiltered u ltravioletradiation, X-rays, gamma rays, andhigh-energy particles (electrons, neu-trons, protons, and heavy ions ) that dono t reach Earth's surface because theyarc either detkc ted by the geomagneticfield or absorbed in the atmosphere.

Heavy particles with high encrgies andcharges (HZEs),which are relativelyrare but vety penetrating and da mag-ing, arc of special interest because theyare poorlv understood and can pene-tnte spacecraft shielding.

To measure radiation eftccts onliving organisms, a Spacelab 1 experi-ment used biostacks, sin gle layers oforganisms sandwiched bcnveen thinfoils of nuclear track detectors. A vari-


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w ""s

ety of organisms tha t differed in size,position in the stack, organizationallevel, developmental stage, an d radia-tion sensitivity were flown. Theseincluded single cells, developing eggs,spores, and seeds. Som e biostacks wereplaced inside the Spacelab modu le an dothe rs were directly exposed to spaceo n the pallet. By comparing the tracksof high-energy particles on the detec-tors with t he biological samplesthro ugh which they passed, investiga-tors could correlate the effect of radia-tion o n a single cell. Results indicatetha t single high-en ergy particles caninduce dramatic changes in individualcells, such as genetic dam age anddeath.with stick insect eggs sandwichedbetween biostack particle detectorsindicated that the H Z E particles pro-duced different degrees of damage a tvarious development stages. Interest-ingly, the effects of the radiation wereenhanced in eggs exposed to micro-gravity and less damaging in eggs kepton a 1- g centrifuge.

In other radiation measurements,several detectors both inside and out-side the Spacelab 1 module measureddoses o f radiation three times higherthan those measured during othe rShuttle missions. Although the radia-tion dose was relatively benign and didnot endanger the crew, investigatorsattributed the higher radiation level tothe higher inclination orbit. (Spacelab1 was the first mission with a 57 degreeinclination rather than the 28 to 40degree orbits for previous missions.)Scientists had predicted that therewould be higher electromagnetic andparticle radiation fluxes a t higher incli-

A related Spacelab D1 experiment

nation orbits. F urthe r study is war-ranted before we embark on long-termmissions at higher altitudes andinclinations.Th e effects of vacuum and ultravio-let radiation w ere also studied o nSpacelab 1. Spores exposed outside onthe pallet formed 50 percent fewercolonies and had 1 0 times more muta-tions than samples grown under normalatmospheric conditions.Biological Processing In Space:Life sciences research not only preparesus to live and work in space bu t alsomay improve life on Eart h. Bioproc-essing in space is a new discipline ofgrowing importance. It is closely re -lated to understanding how cells func-tion in gravity since many of these cellsmake useful produ cts. Early experi-ments have focused on developing theapparatus and technique s for processingbiological substances.Protein crystal growth in space hasbeen especially interesting because ofthe potential applications for determin-in g the three-dimensional structure ofproteins. Many of th e molecules essen-tial for living organisms - especiallyproteins a nd nucleic acids - have ex-tremely complicated three-dimensionalstructures, many of which areunknown. To decipher these structures,crystallographers coax biological mole-cules to organize symmetrically intocrystals big enou gh to study and thenbombard the crystals with X-rays tocreate patterns which computers cananalyze.mation to understand the complexfunctioning and interrelationshipsamong biological materials and organ-

Molecular biologists need this infor-

isms. Knowing the exact architectureof hormones, enzymes, and other pro-teins enables scientists to bypass yearsof tedious trial-and-error experimenta-tion in efforts to design new and moreeffective drugs and to produce im-proved synthetic proteins for industrialapplications.Currently, X-ray crystallography isthe o nly technique available forelucidating the atomic arrangementswithin complicated biological mole-cules, and this method requires well-forme d, large, single crystals of thecompounds being studied. O n Earth,convection and turbulence du ringcrystal formation disrupt the internalcrystalline structur e, and sedimen tationcauses crystals to clump together in-stead of forming distinctly. On e of thegreat bottlenecks in protein crystallog-raphy has been the inability to producelarge, pure crystals for analysis.Fortunately, experiments aboard theShu ttle and Spacelab missions indicatethat much larger and higher qualitycrystals can be grow n in space wheremicrogravity inhibits conve ction an dcrystals float fieely in so lution ratherthan clump together. In a Spacelab 1experiment, two enzymes were crystal-lized: beta-galactosidase (a key geneticingredient) and lysozyme ( a basic pro-tein that is well-studied). In bot h cases,the crystals grown in orbit were muchlarger and purer than those grown inthe same apparatus on th e groun d.united effo rt by a team o f scientistswho developed an apparatus for grow-ing pr otein crystals in space. Proteincrystals have been grown o n fourShuttle flights by a vapor diffusiontechnique. During the most recent

This successful experiment sparked a

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expcrimcnts aboard the 61-C mission,crystals were grow n of these protein s:lysozyme, a protein from hen egg\\.hire with a well-known structure thatcan be used t o compare the quality o fgro und - and spacc-gro\vn crystals; bac-terial purine nucleoside phosphorylase(INP), a protein (with an unknownstructure) used for synthesis o f anti-cancer drugs; huinan


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fascinating pattern: all living organismsfrom microbe to man are influenced bygravity. It is built in to o u r very cells,tissues, and organ s in myriad ove rt an dsubtle ways. Discrete experimentsflown aboard the Shuttle can be inte-grated aboard th e Space Station so thatscientists can collaborate to studyorganisms as a whole and determinehow gravity influences an organismthrou gh its entire life and in subse-quent offspring.Aboard the Sp ace Station, lifescientists will team up with materialsscientists, Earth scientists, and astro-physicists to explore life from themicro to macro level. Materials scien-tists will develop better protein crystalsand purer biological specimens, whichlife scientists can analyze to determinethe structure of life.With photographs and infraredmaps from Earth-orbiting platformsand satellites, biologists can understa ndthe interaction o f Earth and its envi-

ronment on a global scale. They cancorrelate biological, geological, chemi-cal, and oce anographic data to deter-mine how changes (increased industri-alization, land clearing, oil spills, etc. )propagate to neighbor ing areas in thebiosphere.The Space Station will offer lifescientists, chemists, and astrophysicistsa chance to d o unique experiments inexobiology, the study of the origin,evolution, an d distribution o f life inthe universe. Astronomers already havedetected the essential biochemicals(carbon, nitrogen, oxygen, phospho-rus, sulfur, et c.) light-years away fromEarth. T he Space Station will have anunobstruc ted view of the solar system,comets, meteorites, and asteroidswhich may contain molecules andchemical fragments of biological sig-nificance. Contin uous viewing of theuniverse from the Station and o rbitalobservatories increases our chances offinding other planets and perhaps otherlife in th e universe. T he S tation can beused as a platform for huge cosmicdust collectors, alloinring biologists toexamine particles from interstellarspace for biogenic e lements and m aybeeven simple organisms.Th e study of life in ou r solar systemwill be augmented by manned andunmanned planetary expeditions.Through NASAs Controlled Ecologi-cal Life Suppo rt System (CE LSS ) pro-gram, scientists are working to developlife support systems for spacecraft that

can process wastes, recycle air andwater, a nd supp ort the cultivation ofplant and animal food sources. Thistype o f spacecraft, which will be usedfor long-du ration missions whereresupply from Earth is impractical orimpossible, will make deep space acces-sible to human exploration.Space must be a comfortable andproductive w orkplace. We are stilllargely ignorant of the m echanismsand limits of hum an adaptation to pro-longed spaceflight. Scientists mustdetermine how humans and otherorganisms adapt to the space environ-men t and develop sound countermea-sures to detrimental effects. Humanfactors and physiological experimentswill be con ducted to design the SpaceStation as well as other space worksta-tions for safety, efficiency, and comfort.The re is still much to be accom-plished before space becomes ourhome and workplace. Th e Shuttle willcontinue to be a testbed for advancedequipment. A series of dedic atedSpacelab Life Sciences (SLS) missionsstaffed by expert biologists is alreadyplanned for the next decade. By dedi-cating a mission to one discipline, it ispossible to integrate experiments andexplore a spectrum of related data. Aseries of International MicrogravityLaboratory ( IM L) missions shared bymaterials and life scientists will carryvaluable experiments and has alreadyenabled an international w orkinggrou p of scientists to establish a solidbase for sharing ideas and results.Results from the Shuttle andSpacelab missions have blazed th epaths of exploration, and we are begin-ning to make space an extension of lifeon Earth.

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t

f

-",,_I- *- I lnm

^' 11*

OSTA-1BTS-2Heflex Bioengmeermg Test IA.H Brown, Unwerslty of PennsylvanlaPh/ladelohra,Pennsvlvan/aOSS-lBTS-3Heflex Bioengineering Test I /A. H. Brown, University of PennsylvaniaPhiladelphia, Pennsylvania

J.R. Cowles, University of Houston, Texaslnfluence of Weightlessness on Lignification in Plant SeedlingsSpacelab 1BTS-9Advanced Biostack Experiment

Circadian Rhythms during Spaceflight: NeurosporaH. Buckel; DFVLR, Cologne, West GermanyFM. Sulzman, NASA HeadquartersWashington, D.C.A. Cogoli, Swiss Federal Institute of TechnologyZurich, SwitzerlandE. W Voss, University of Il linoisUrbana, IllinoisC.S. Leach, NASA Johnson Space CenterHouston, TexasMass Discrimination during WeightlessnessH.E. Ross, University of Stirling, ScotlandMeasurement of Central Venous Pressure and Hormones

Effect of Weightlessness on Lymphocyte Proliferation

Humoral Immune Response

lnfluence of Spaceflight on Erythrokinetics in Man

in Blood Serum during WeightlessnessK. Kirsch, Free University of Berlin, West GermanyG. Horneck, DFVLR, Cologne, West GermanyMicroorganisms and Biomolecules in the Space Environment

Nutation of Sunflower Seedlings in Microgravity *A.H. Brown, University of PennsylvaniaPhiladelphia, PennsylvaniaPersonal Electrophysio logical Tape RecorderH. Green, Clinical Research Center, Harrow, EnglandCrystal Growth of ProteinsW Littke, University of Freiburg, West GermanyRadiation Environment MappingE.v:Benton, University of San Francisco, CaliforniaRectilinear Accelerations, Optokinetic and Caloric StimulationsR. von Baumgarten, University of Mainz, West GermanyThree-Dimensional Ballistocardiography in WeightlessnessA . Scano, University of Rome, ItalyVestibular ExperimentsL.R. Young, Massachusetts Institute of TechnologyCambridge, MassachusettsM I Reschke, NASA Johnson Space CenterHouston, TexasVestibulo-Spinal Reflex Mechanisms

- - - ~ . , llll.," ~OSTA-3/41-C0 National Research Council of Canada Vestibular nvestigationsD. Watt, McGill Univers i(v, Montreal, Canada

,-I," .. ...... .... . ~ ~ l " " l _.. ..... " - . " ~ l ~ l l l - " " .Spacelab 3/51 BAutogenic Feedback TrainingPS. Cowings, NASA Ames Research CenterMoffett field, Californiat? Callahan and C. Schatte, NASA Ames ReseaKh CenterMoffett Field, CaliforniaH. Schneidel; NASA Johnson Space Centel; Houston, Texas

Research Animal Holding Facilities

Urine Monitoring Investigation"x"" . ~ - . ........... ......................5 1 4 Aggregation of Human Red Blood CellsL. Dintenfass, Kanematsu Institute, University of Sidnex Australia

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51-0 American Flight EchocardiographM.w1 Bungo, NASA Johnson Space CenterHouston, TexasContinuous Flow Electrophoresis System * *D. Clifford, McDonnell Douglas Aerospace CompanySt. Louis, MissouriC.E. Bugg, University of Alabama in Birmingham, AlabamaProtein Crystal Growth Experiment

ll___-..lSpiiC818b2b1-FGravity Influenced Lignification in Higher Plants *Protein Crystal Growth ExperimentVitamin D Metabolites and Bone Demineralization

J. R. Cowles, University of Houston, TexasC. E. Bugg, University of Alabama in Birmingham, AlabamaH.K. Schnoes, University of WisconsinMadison, Wisconsin

51-6 French Echocardiograph ExperimentFrench Postural ExperimentL Pourcelot, University of Tours, FranceA. Berthoz, National Center for Scientific Research, Paris, France

. . ~~51-J BIOSS.L. Bonting, University of Nijmegen, The NetherlandsAntibacterial Activity of Antibiotics in Space ConditionsR. Tixador; University of Toulouse, FranceBody Impedance MeasurementF: Baisch, DN LR, Cologne, West GermanyCell Cycle and Protoplasmic StreamingV : Sobick, DN LR, Cologne, West GermanyCell Growth and Differentiation in SpaceH.D. Mennigmann, University of Frankfurt, West GermanyCell ProliferationH. Planel, University of Toulouse, FranceCentral Venous PressureK. Kirsch, Free University of Berlin, West GermanyCircadian Rhythm under Conditions Free of Earth GravityD. Mergenhagen, University of Hamburg, West GermanyDeterminationof the Dorsoventral Axis in Developing Embryos

I__S$&elab OlBl-A

of the AmphibianG.A. Ubbels, University of Utrecht, The NetherlandsM. Hoschek and J. Hund, DFVLR, Cologne, West GermanyR. R. Theimel; University of Munich, West GermanyR. Marco, University of Autonoma, Madrid, SpainH. Bucker; DFVLR, Cologne, West Germany0. iferri, University of Pavia, Italy

Determination of Reaction TimeDifferentiation of Plant CellsDistribution of Cytoplasmic DeterminantsDosimetric Mapping Inside BiorackEffect of Microgravity on Interaction between Cells

j1

Embryogenesis and Organogenesis under Spaceflight ConditionsFrog StatolithsGeotropismGesture and Speech in MicrogravityGraviperception of PlantsHuman Lymphocyte Activation *

H Buckel; DNLR, Cologne, West GermanyJ Neubert, DNLR, Cologne, West GermanyJ Gross, University of Tubingen, West GermanyA D Friederici, University of Nijmegen, The NetherlandsD Volkmann, University of Bonn, West GermanyA. Cogoli, Swiss Federal lnstitute of TechnologyZurich, SwitzerlandMammalian Cell PolarizationM Bouteille, University of Paris, FranceMass Discrimination in WeightlessnessH E Ross, University of Stirling, ScotlandProtein Crystals*W Littke, University of Freiburg, West GermanySpatial Description inSpaceA D Friederici, University of Nymegen, The NetherlandsStatocyte Polarity and Geotropic ResponseG Perbal, University o f Par is, FranceTonometerJ Draeger; University of Hamburg, West GermanyVestibular ResearchL R Young, Massachusetts Institute of TechnologyCambridge, MassachusettsR von Baumgarten, University of Mainz, West GermanyVestibular Research

_lll ~ - - -61-6 Continuous Flow Electrophoresis System * *D Clifford, McDonnell Douglas Aerospace CompanySt Louis, MissouriEffects of Weightlessness and Light on Seed GerminationA J Peluyera, National Consumer lnstitute, Mexico Citx MexicoElectropuncture in SpaceF Ramirez y Escalano, MexicoProtein Crystal Growth ExperimentCE Bugg, University of Alabama in Birmingham, AlabamaTransportation of Nutrients in a Weightlessness Environment1. Ortega, Institute of Physics,_ Cuernavaca, Mexico

Noninvasive Estimation of Central Venous Pressure61-c Using a Compact Doppler Ultrasound SystemJ B Charles and M W Bungo, NASA Johnson Space CenterHouston, TexasC E Bugg, University of Alabama in Birmingham, AlabamaProtein Crystal Growth Experiment-

* Refhght6mas~onscomp/efed(STSB 7 -8 41-0 51-0 61 B)

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Chapter 3aterials science includes suchM iverse processes as conv ertingsand to silicon crystals fo r use in semi-conductors, producing high-strength,temperature-resistant alloys and ceram-StudyingMaterials andProcesses in ics, separating biological materials intovaluable drug s and chemicals. and,studying the basic phenomena thatinfluence these processes. Materialsprocessing is melting, molding, crystal-lizing, and combining or separatingMateiiais- _ raw materials into useful Droducts. Thehistory o f science an d civilization goeshand in hand with advances in materi-

als science and technology.In some cases, progress in m aterialsscience on Earth has been limited:materials will not mix to form newalloys; crystals have defects that limittheir performance; biological materialscannot be separated well enough toform some ultra-pure substancesneede d fo r medicine; crystals clumptogether instead of forming distinctly;glasses are co ntamin ated by processingcontainers. Many of these problems arerelated to a constant force on Earth -gravity.T he presence o f gravity has beencounte racted in low-gravity aircraftflights and drop tubes, which offerabout 30 seconds and 4 seconds ofmicrogravity, respectively. Althoughthe period of microgravity is brief,

these test facilities are beneficial forresearch in preparation for spaceflight.Th e pull of gravity cannot be escapedat any altitude; a t a 32 2 kilometer(200 mile) orbit, it is still 90 percent asstrong as a t the Earths surface. How-ever, its effects can be virtually cancel-led by remaining in free fall, that is,by remaining in orbit around the Earthas a satellite does. Spaceflight offers

...,,,., __Science

extend ed periods of low gravity; longduration is important for most solidifi-cation experiments, especially crystalgrowth. It is impossible to sustain acomparable microgravity environmento n Earth.NASAs microgravity science pro-gram uses spacefight to eliminate orcounteract gravity-induced problemsthat hamper materials scientists on theground: buoyancy-driven convection inliquids, contam ination from vesselsthat contain samples, and induce dstresses that cause defects in clystals.Dramatic improvements in materialproperties have been achieved in recentmicrogravity experiments as OUTabilityto control tem perature has improved.Similar improvements can be expectedin the future as our understanding ofthe effects of mass transport increasesalong with our ability to control con-vective flows.Pioneering experiments from 1969to 1975 aboard Apollo-era spacecraftand the Skylab space station led theway to microgravity science payloadsdeveloped for the Space Shuttle in thelate 1970s.The Shuttle/Spacelab hasproven useful for carrying many newautomated and manually controlledfacilities developed for materials scienceresearch.Automated systems are appropriatefor simpler experiments that need lesscrew involvement but still require thereturn of samples and equipm ent tothe ground for analysis. The au tomatedMaterials Experiment Assembly (MEA)combined low-cost sounding rockettechniques with the extended micro-gravity duration of the Shuttle. Thiscarrier supports three o r four experi-ment modules in the payload bay.

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Studying Materials andProcesses in Microgravity

For m ore sophisticated experimentsrequiring intense observation and crewcontro l, facilities have been developedfor th e shirt-sleeve laboratory environ-men t of the Spacelab module and forthe Shu ttle middeck. Spacelab offersscientists a place to d o exploratorywork such as attempting new process-ing techniques or testing basic theories.Scientists serve as crewmembers toobserve and control experiments.Thinking in Terms of Microgravity:Because gravity is a dom inati ng factoro n Earth, it is difficult to think interms of reduced gravity. Results fromthe early Shuttle/Spacelab missionsprove that scientists are mee ting thischallenge as they develop techniquesand attemp t experiments th at areaffected by gravity in laboratories onthe ground.Th e first space produ ct is now o nthe market: monodisperse latexspheres, precision microspheres thatcan be produced in space with im-proved uniformity. These spheres,which were produced in an apparatusin the Shuttle middeck during fivemissions, have been reco gnized as acalibration sta ndard for m icroscopy.Many of the experiments accom-plished to date are not aimed at pro-duction but seek to discover moreabout the fund amental physics and

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ORIGINAL' PAGECOLOR Pi '3TOGRAPH

chemistry o f materials processes o nEar th. In microgravity, space scientistscan use techniques to improve meas-urement accuracy and to t ry to observephenomena that are not detectable o nEar th, Analyses of samples produced inmicrogravity allow scientists to deter-mine how gravity affects materialsprocessing. F or example, convectionand sedimentation dominate thetransport of heat and matter in manysystems, but in space the effects ofweaker forces such as surface tensionare unveiled. Clarification of these ph e-nomena may lead to better processingtechniques on Earth and result in thediscovery of materials with novel andcommercially interesting properties.Th e types of materials processedaboard the Shuttle/Spacelab includecrystals and electronic materials, metalalloys and composites, glasses an dceramics, fluids and chemicals, and bio-logical materials.

D""

Crystals and Electronic Materials:Crystals have achieved far greater valueas electronic materials than they everhad as gems. Man has improved onnature's offerings but has been haltedby bottlenecks th at prevent som e crys-tals from reaching their theoreticalperformance limits. Before crystalgrow th can be improved, scientistsmust determine what factors are re-sponsible for crystal defects a nd learnhow to control them.Striking results were obtain ed w ithexperiments on mercury iodide, a softcrystal valued for its potential as anuclear radiation detector because itoperates at room temperature withouta bulky cooling system. Controllingthe growth of a large mercury iodidecrystal in microgravity was de mo n-strated with the Spacelab 3 VaporCrystal Growth System. For the firsttime, crewmembers on th e Shuttle andscientists on Earth monitored a crystalas it grew in microgravity. Images wererelayed to th e ground via television,and the crew viewed the crystalthrough a microscope imaging system.This allowed the growth of the crystalto be tracked through each stage, andscientists changed parameters such astemperature to adjust the growth andreduce defects, much as they do inground-based laboratories.

A seed crystal mounted on a small,cooled finger (sting) at the base of th eampoule was a condensation point formaterial evaporated from a source a tthe top . Th e crystal grown in space for100 hours was comparable to the bestterrestrial crystals. The crystal quality,seen by reflecting X-rays, appeared tobe better tha n the ground-based crystalused as a standard. Ga mma ray testsshowed the interior quality to be betterthan terrestrial mercury iodide crystals.During the Spacelab 3 mission,more basic knowledge about crystalgrowth in microgravity was obtainedby growing triglycine sulfate (TGS)crystals in the Fluid E xperiment Sys-tem . Triglycine sulfate has potential asan infrared radiation detector at roomtemperature. This crystal has no t metexpected standards because, whengrown to useful sizes, it developsdefects which limit its performance.For this experiment, TGS crystalswere grown from solution with liquidTGS h i d solidifying on a seed crystal.Th e crystal and fluid are transparent,which makes it possible to recordimages of fluid motions. The growthchamber was in the c enter of a preci-sion optical system which allowedphotography by three techniques:shadowgra phy; schlieren, by whichvariations in fluid density make flow

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patterns visible; and interference ho lo-graphy, using lasers to record densityvariations near t he sam ple.T he TGS crystals shed light o n ho wdefects are formed and what role con-vection plays in creating defects, som e-thing that is not well understood. Atthe beginning of growth, a portion ofthe seed crystal is dissolved to form asmooth growth surface. In Earth-gro wn crystals, ther e is always a visibleline where th e seed crystal stops andthe new grow th begins; this introducesdefects into the crystal. In the space-grown crystals, this line was no tdetected. This indicates that in theabsence of convection the transition issmoother between the seed and thestart of new grow th.ment examined insoluble crystals(calcium and lead phosphates) thatgrow quickly to form plate-like crystalswhich are easily studied by X-ray tech-niques. Large crystals were grow n, an d

A Spacelab 1 crystal growth experi-


the portions of the crystals grown inmicrogravity were free of defects.Defects were evident in portions of thecrystals grown as the Shuttle lan ded,suggesting that defects are reduced inmicrogravity.Another Spacelab 1 experimentstudied processes linked to the d istri-bution o f dopants (trace elements) thatgive crystals desired electrical proper-ties. For example, the conductivity ofsemico nductor s is dramatically change dby adding dopants. However, nonun i-form distribution of these dopants caninterfere with the operation of electri-cal devices that use crystals. For mostapplications, the semiconductors pro-duced o n Earth are adequate, but fo rsome highly specialized applicationsmore uniformly doped, defect-freecrystals are needed. Earlie r experimen tsdetermined that convection that variesover time caused dopant striations incrystals.T he Mirror Heating Facility

(Spacelab 1) modeled float-zoneEarth-processing methods to deter-mine whether the troublesome convec-tive flows were produced by buoyancyor surface tension. Two experimentswere done in an attempt to growdefect-free, single crystals of silicon.However, the space-grown crystals hadthe same marked dopant striations seenin Earth-g rown crystals, confirmingthat Marangoni convection (flowdriven by surface tension) may be adominan t cause of the defects on Earthand in space.In ground-based experiments afterSpacelab 1, the silicon seed crystal wascoated with a thin oxide layer to pre-vent Marangoni flow as the crystalgrew. Th e striations were eliminated,indicating that this is a successful tech-nique for reducing the effects ofMarangoni flow. For Spacelab D1, th eexperiment was repeated using thistechniqu e, and striation-free crystalsalso were grown in space.

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t58erciiry Odide Grysl"al

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On the M EA-A1 mission, germa-nium selenide crystals were form edinside heated quartz ampoules. Thesize of the crystal and the location ofcrystal formatio n were far differentthan expected. On Earth, the crystalswere small and formed a crust aroundthe amp oule walls. In space, largercrystals nucleated in the middle of theampoule away from the walls. Th ecrystals were almost flawless, with strik-ingly improved surface qualities. Theexperiment was repeated on the MEA-A2 mission (flown with Spacelab D l ) ,and similar results were ob tained. Thisindicates that the vapor-transporttechniq ue may b e an excellent way toprodu ce crystals in space.

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Metals, Alloys, and Composites:Scientists continue in their quest toimprove metallurgical processes, toform better a nd novel alloys, and totest theories of m etal and alloy process-ing. This type of processing is socomplex th at it is difficult to measureand model and even more difficult tocon trol. In space, gravity-relatedphenomena such as convection arereduced, thus eliminating one complexmechanism for m ass and heat transferand simplifying processes for study.Perhaps the m ost fundamental ad-vances made in this area on the Shuttlewere in understanding how liquifiedmetals diffuse throu gh each other.Diffusion is the mov ement of atom spast each other; each material has aninheren t diffusion coefficient whichdescribes th e ability of atoms to movepast each other in that material. Grav-ity-induced convection complicatesdiffusion measurements on Earth.Spacelab 1 results indicate tha t space

may be th e only place where accuratemeasurements of the coefficients can bemade.Spacelab 1 experiments showed thatpure diffusion can be measured s o wellin space that thermomigration, alsocalled Soret diffusion, is clearly evident.In a binary mixture in which a tem-perature gradient is maintained,thermomigration causes the constitu-ents to separate according to theiratomic weights. T he heavier compo-nents will migrate toward the cool endof a furnace and the light comp onentswill migrate toward the hot end.For o ne Spacelab experiment study-ing thermomigration, the GradientHeating Facility, which had hot andcold ends to force a physical process tomove in a given direction, provided atemperature drop of 648 degrees Fahr-enheit from one e nd of the sample tothe other. A sample of tin containing0.5 percent cobalt was processed. Dueto convective mixing, samples proc -

essed on the ground were evenlymixed; however, those processed inflight had doub le the cobalt concentra-tion at the hot end of the ampoule.Th e accuracy of these measurementswas 300 times better than ground-based experiments had achieved. Thisexperim ent may influence research toseparate isotopes of metals with greaterefficiency.A similar experiment using comm onisotopes of tin measured its diffusioncoefficient w ith an accuracy 10 to 40times greater than the best grou nd-based experiments. Radiation analysisshowed how much of the trace quamtity of tin-12 4 had migrated into thetin- 12 making up the bulk of thesample. Because isotopes are chem i-cally identical, any movement of oneinto the other must be caused purelyby difhsion instead of any chemicaleffect. Several tubes with differen tdiameters were used to isolate vari-ations caused by the walls. A striking

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result was the high accuracy, un -matched in groun d tests, of data indi-cating that the d if is io n coefficient wasmuch smaller than indicated byground-based experiments. Accuracy inthis figure will greatly improve th eability to model metal-mixing experi-ments both on the ground and inspace, and the improved precision ofdiffusion measurements at differenttempe ratures will help scientists estab-lish the mechanism by which difhsiontakes place in liquid metals.A large numbe r of alloys belo ng toan interesting class called eutectics. Aeutectic m aterial is a mixture o f twomaterials that has a lower melting poin tthan either material alone. In the liquidphase the two materials that form aeutectic are completely miscible, bu t inthe solid phase they are almost com-pletely immiscible. Therefore , as twomaterials that form a eutectic solidify,they go from a single liquid phase totwo distinct solid phases. Becausemany alloys are eutectics, scientists areinterested in understanding the distri-bution of the immiscible solid phases.If a eutectic alloy is directionally solidi-fied, long rods or lamella (shee ts ofone phase sandwiched betweenanother phase) are formed; the alloymay have desirable properties, such asadded strength or higher magneticperformance in one direction.As a result of space experiments,scientists are reexam ining a classicaltheory o n the formation of eutectics.Th e theory assumes there is n o convec-tion in the melt when the eutecticmaterials are processed in space. Th etheory works quite well on Earth, butan earlier rocket experiment produceda eutectic with ro d spacing quite

Documents

Science in Orbit the Shuttle and Spacelab Experience 1981-1986