[Congressional Record Volume 140, Number 112 (Friday, August 12, 1994)]
[Senate]
[Page S]
From the Congressional Record Online through the Government Printing Office [www.gpo.gov]


[Congressional Record: August 12, 1994]
From the Congressional Record Online via GPO Access [wais.access.gpo.gov]

 
    ACHIEVEMENTS IN MICROGRAVITY: TEN YEARS OF MICROGRAVITY RESEARCH

 Mr. GLENN. Mr. President, I ask that the article entitled 
``Achievements in Microgravity: Ten Years of Microgravity Research'' be 
made a part of the Record.
  The article follows:

    Achievements in Microgravity: Ten Years of Microgravity Research

   (By S.J. Graham and R.C. Rhome, NASA Headquarters, Washington, DC)


                                abstract

       An overview of microgravity research in space supported by 
     the National Aeronautics and Space Administration during the 
     period 1983 to 1993. Selected activities in the areas of 
     biotechnology, combustion, fluid physics, and material 
     science are discussed. The paper is not intended to be a 
     comprehensive assessment of scientific experimental results.


                            i. introduction

       In 1992, the National Aeronautics and Space 
     Administration's (NASA) Microgravity Science program 
     conducted more peer reviewed, hands-on United States 
     microgravity science research in space than performed 
     cumulatively in all prior years since Skylab (1973-74). This 
     was accomplished through the use of the European Space 
     Agency's (ESA) Spacelab and the considerable capabilities 
     offered by NASA's Space Shuttle. The period between Skylab 
     and the present has seen a wide array of basic and applied 
     microgravity research in ground-based and suborbital 
     facilities, as well as orbital flight. The conduct of such 
     experimentation has not been continuous over this period. The 
     hiatus in flight opportunities following the 1986 Challenger 
     tragedy resulted in a slowed evolution of in-space research. 
     The ground-based program did provide steady advances during 
     the late 1980s as preparations were made for the resumption 
     of Shuttle and dedicated Spacelab flights, resulting in the 
     flurry of research activity in 1992. This discussion of ten 
     years of Microgravity research is an overview of selected 
     activities in the broad range of microgravity science 
     disciplines supported by NASA during the period 1983-1993 and 
     is not intended to be a comprehensive assessment of specific 
     results.\1\
---------------------------------------------------------------------------
     Footnotes at end of article.
---------------------------------------------------------------------------
       Many experiments using the space environment have tested 
     fundamental theories of physics, chemistry, and other 
     disciplines. Data from these experiments have begun to deepen 
     our understanding of these theories. A second class of 
     experiments uses the scientific method to carry out 
     investigations in areas where theories are incomplete. Space 
     research has provided data that challenges our understanding 
     of a particular phenomenon, paving the way for new research. 
     Finally, research in preparation for space experiments has 
     led to significant advancement in the way a large class of 
     experiments are done here on the ground. Such studies lead to 
     new techniques and technologies which can substantially 
     change science and applications research in their respective 
     fields.


                         ii. program evolution

       NASA's Office of Life and Microgravity Sciences and 
     Applications (OLMSA) is responsible for planning and 
     executing the scientific research activities associated with 
     the Agency's goals.\2\ Within OLSMA, the Microgravity Science 
     and Applications Division undertakes the study of important 
     physical, chemical and biological processes in a microgravity 
     (ug) environment. Initial research into the effects of 
     microgravity began in the early years of the space program, 
     including space experiments conducted during the Apollo, 
     Skylab and apollo-Soyuz programs. The advent of the Space 
     Shuttle program enabled the development of microgravity 
     research instruments that could be flown, modified, and re-
     flown, allowing scientists to design experiments based on the 
     results of previous investigations. The microgravity research 
     program is divided into two realms of experimental work; 
     experiments that are in refinement stages (ground-based) and 
     experiments that are considered ready and worthy of a space 
     flight opportunity. The ground-based program is intended to 
     select and foster research for those hypotheses that require 
     reduced gravity for an ultimate experimental test. In the 
     early 1980s, the presumption of the appropriateness of a 
     NASA-sponsored research program was the ultimate need for 
     space flight. Less than fifty Principal Investigators were in 
     the NASA-sponsored microgravity research program, almost 
     exclusively working towards a space flight opportunity. As 
     the program has evolved, however, it has become more apparent 
     that there are a broad range of hypotheses in which gravity 
     is the experimental parameter that can and are being 
     addressed by means other than space flight. The ground-based 
     program has grown to become the intellectual underpinning of 
     the flight program, with more than seventy-five percent of 
     the 180 NASA-funded microgravity science Principal 
     Investigators involved in ground-based research. It is 
     anticipated that the ratio of ground-based to space flight 
     investigators will continue to grow as the program heads for 
     a 1998 projected research establishment supporting over 340 
     NASA-sponsored microgravity research Principal Investigators.
       The Microgravity Science and Applications Division is 
     responsible for guiding a comprehensive research program, 
     currently concentrating on biotechnology, combustion science, 
     fluid dynamics and transport phenomena, materials science, 
     and selected studies in gravitational and condensed matter 
     physics. The Division seeks out and coordinates an 
     interdisciplinary science community to conduct the research 
     and to disseminate the results of its science program. It 
     also supports the science community's research through the 
     development of suitable experiment instruments and by 
     choosing the space carrier most suitable for its experiments. 
     The results of the investigations, some of which are reported 
     here, are used to challenge and validate contemporary 
     scientific theories, to identify and describe new physical 
     phenomena that can be uniquely explored in a microgravity 
     environment, and to engender the development of new theories 
     as a result of unexpected or unexplained discoveries often 
     the most exciting part of the research.


                      iii. biotechnology research

                         Protein Crystal Growth

       Protein crystal growth (PCG) has been a promising area of 
     microgravity research ever since early work by Walter Littke 
     (University of Freiberg) aboard Spacelab-1 (1983) indicated 
     that significantly larger and higher quality protein crystals 
     could be grown in a low gravity environment. Now ten years 
     later, with over 70 different proteins flown in orbit, this 
     area of research has emerged as one of the most notable 
     success stories of NASA's microgravity program. (Table 1)
       Proteins are basic elements of life. These complex chains 
     of amino acids not only form the physical substance of living 
     organisms but also play an essential role in every 
     biochemical process governing the body. Scientists seek to 
     determine the molecular structures of proteins, and the 
     relationship between protein structure and function. This 
     information will provide a better understanding of living 
     systems and help develop new drugs for medical treatments. 
     The technique used to determine protein structure, X-ray 
     diffraction, requires the use of relatively large, high 
     quality crystals of the protein being studied. Quite often 
     however, in spite of years of research in academic and 
     industrial laboratories, crucial proteins fail to adequately 
     form the needed crystals on Earth. In many cases this failure 
     can be attributed to the effects of Earth's gravity, which 
     not only generates fluid flows which may damage growing 
     crystals but also causes the crystals to sediment to the 
     bottom of their growth container. Once the protein crystal 
     has settled on a container surface the protein solution can 
     no longer reach all sides of the crystal and further growth 
     can be severely distorted. It was these constraints which led 
     early crystal growers to a low gravity environment where 
     buoyancy driven flows could be eliminated and crystals could 
     grow freely suspended in solution.
       The first protein crystallization flight experiment was 
     flown by Drs. Littke and John aboard Spacelab-1 in 1983 using 
     two proteins of widely differing weights, betagalactosidase 
     and lysozyme.\3\ In microgravity these proteins respectively 
     yielded crystals 27 and 1000 times larger than the ground 
     control experiments. The publication of the results generated 
     many new questions about the fundamental mechanisms of 
     protein crystal growth and led to the organization of the 
     first International Conference on Crystallization of 
     Biological Macromolecules in 1986 at Stanford University. 
     Prior to this, most scientists carrying out protein crystal 
     growth research had grown crystals without great concern for 
     the physics involved, using a primarily trial-and-error 
     approach. The findings of this conference revolutionized 
     thought among investigator in the field and resulted in a 
     redirection of effort in a number of ground-based labs to 
     understand and control the growth of protein crystals and to 
     use the space environment as a means to gain insights into 
     the growth process as well as a method of obtaining better 
     crystals.

                    Table 1: Proteins grown in space

                          STS-51D--April 1985

       Bugg--Human Purine Nucleoside Phosphorylase (PNP)--Protein 
     for Immunosuppressive and anticancer drugs
       Bugg--Lysozyme--Model Protein degrades bacterial cell walls
       Bugg--Scorpion Toxin
       Bugg--Sea Anemone Toxin
       Suddath--Lectin--Binds blycames of glycoproteins on cell 
     surfaces
       Suddath & Delucas--Human Serum Transferrin--Iron transport 
     to hemoglobin synthesizing red blood cells
       Nagabhushan--Interferon alpha-2b--Stimulates immune system
       Bugg--Bacterial PNP--Protein for immunosuppressive and 
     anticancer drugs
       Laver--Neuraminidase-Antibody Complex--Surface protein of 
     the influenza virus
       LU--Synthetic DNA--Artificial Model of DNA
       Delucas & Volanakis--Human C-Reactive Protein--Plays a 
     central role in the human immune system
       Ward--Green Fluorescent Protein--Protein found in marine 
     bioluminescent jellyfish
       Hogle--Fab--Antibodies with specificity to antigens that 
     occur on cell surfaces
       Arnone--Human Nuclear TRNA--Associated with protein 
     synthesis

                         STS-26--September 1988

       McPherson--Canavalin--Major reserve protein of leguminous 
     seeds
       Nagabhushan--Gamma Interferon--Antivital agent, stimulates 
     immune system
       DeLucas--Human C Reactive Protein--Plays a central role in 
     the human immune system
       Bugg--Purine Nucleoside--Degrades anticancer drugs
       Carter--Human Serum Albumin--Binds and transports drugs and 
     other materials
       Weber--Isocitrate Lyease--Target enzyme for fungicides
       Einspahr--Phospholipase--Interacts with phospholipids 
     associated with cell membrane functions
       Navia--Porcine Elastase--Involved in lung disease such as 
     emphysema
       Einspahr--Renin--Involved in controlling high blood 
     pressure
       Krenitsky--Reverse Transcriptase--Enzyme essential to the 
     AIDS virus
       Weber--Synthetic Peptide (alpha helicin)--Involved in human 
     cell regulation of electrolytes

                           STS-29--March 1989

       Carter--Alcohol Oxidase--Enzyme involved in cellular 
     metabolism
       Eggleston--Aridicin Aglycone--Industrial antibiotic
       McPherson--Canavalin--Major reserve protein of leguminous 
     seeds
       Rubin--Diacetinase--Glycerol ester hydrolase from bacillus 
     subtilis
       Nagabhushan--Gamma Interferon--Stimulates immune system
       Jones--Human Growth Hormone--Used in treatment of unusually 
     small children
       Weber--Isocitrate Lyase--Target enzyme for fungicides
       Lu--Lec Repressor--Regulates the expression of lactose 
     operon in e. coli
       Fontecilla--Lectin--Binds glycames of glycoproteins on cell 
     surfaces
       Laver--Neuramindase--Surface protein of the influenza virus
       Navia--Porcine Elastase--Involved in lung disease such as 
     emphysema
       Elnspahr--Renin--Involved in controlling high blood 
     pressure
       Yonath--Ribosome--Plays major role in protein processing in 
     cell
       McPherson--Satellite Tobacco Mosaic Virus--First virus 
     crystallized

                          STS-32--January 1990

       Voet--12 Base Pair DNA--A segment of DNA which helps 
     control protein synthesis
       DeLucas--Aldose Reduciase--Enzyme connected to diabetic 
     complications
       Eggleston--Aridicin Aglycone--Industrial antibiotic
       McPherson--Canavalln--Major reserve protein of leguminous 
     seeds
       McPherson--Catalase--Detoxifying enzyme
       Weber--Cyanobacterium--Photosystem 1 Complex Membrane 
     protein complex involved in light-drive electron transfer
       Weber--Cyclosporin A-Cyclophillin complex--Used to suppress 
     immune rejection during organ transplant
       Rubin--Diectinase--Glycerol ester hydroiase from bacilus 
     subtillis
       Senadhi--Gamma Interferon--Antiviral agent, stimulates 
     immune system
       Jones--Human Growth Hormone--Used in treatment of unusually 
     small children
       Carter--Human Serum Albumin--Binds and transports drugs and 
     other materials
       Suddath--Human Serum Transferrin--Iron transport to 
     hemoglobin synthesizing red blood cells
       Weber--Isocitrate Lyase--Target enzyme for fungicides
       Lu--Lac Repressor--Regulates the expression of Lactose 
     operon in e. coli
       Fontecilla--Lectin--Binds glycames of glycoproteins on cell 
     surfaces
       DeLucas--Lysozyme--Model protein
       Laver--Neuraminidase--Enzyme connected with influenza virus
       Einspahr--Phosphollpase--Interacts with phospholipids 
     associated with cell membrane functions

                           STS-31--April 1990

       Birnbaum--anti-HPr FAB Fragment--Provides picture of 
     antibody blinding site
       McPherson--Canavalin--Major reserve protein of leguminous 
     seeds
       Rubin--Carboxyl Ester Hydrolase--Catalyzes the breakdown of 
     carboxylic acid exters like those found in fats
       DeLucas--Factor D--Enzyme responsible for activation of the 
     complement system
       Reichert--Gamma Interferon--Antiviral agent, stimulates 
     Immune system
       Carter--Human Serum Albumin--Binds and transport drugs and 
     other materials
       Suddath--Human Serum Transferrin--Iron transport to 
     hemoglobin synthesizing red blood cells
       Weber--Isocitrate Lyase--Target enzyme for fungicides
       Einspahr--Malic--Enzyme Enzyme Isolated for a parasitic 
     nemalode
       Navia--Procine Elastase--Involved in lung disease such as 
     emphysema
       Ward--Porcine Pancreatic Phospholipase--Protein involved in 
     rheumatoid arthritis and septic shock
       Fonteoilla--Turkey/quail Lysozyme--Model protein
       Meyer--Type IV Collegenase--Enzyme obtained from snake 
     venom

                          STS-43--August 1991

       Long--Bovine insulin

                         STS-48--September 1991

       Delbaere--anti-HPr FAB Fragment--Provides picture of 
     antibody binding site
       Weber--Apostreptavidin--Binds the vitamin blatin
       Ward--Bacterial Luciferase--Protein responsible for 
     bioluminescence in open oceans
       Knox--Bets-Lactemese--Enzyme that destroys antibiotic
       Navia--Bovine Proline Isomerase--Drug target for anti-
     rejection treatments
       McPherson--Canavalin--Major reserve protein of leguminous 
     seeds
       Birnbaum--Fab YST9-1 of Brucella--Antibodies that have 
     specificity to antigens that occur on cell surfaces
       Nagabhushan--Interleukin-4--Potential antitumor agent
       McPherson--Satellite Tobacco Mosaic Virus--First virus 
     crystallized
       Navia--Themolysin--Used in potential method for producing 
     aspartame
       Einspahr--Two-Domain CD4--Product being tested as AIDS 
     treatment

                       STS-42/ML-1--January 1992

       Albara--Lysozyme--Model protein
       Einspahr--2 Domain CD4:FAB--Product being tested as AIDS 
     treatment
       Delbaere--anti-HPr FAB Fragment--Provides picture of 
     antibody binding site
       Weber--Apostrepavidin--Binds the vitamin blatin
       Navia--Bovine Proline Isomarase--Target enzyme for immuno-
     suppressive agents
       McPherson--Canavalin--Major reserve protein of leguminous 
     seeds
       Voet--DNA 12-MER Segment of Lac Operator--DNA sequence 
     recognized by lac operon
       Birnbaum--FAB YST9-1 from Brucella--Antibodies that have 
     specificity to antigens that occur on cell surfaces
       Stanmers--HIV Reverse Transcriptase--Chemical key to 
     replication of AIDS virus
       Arnold--HIV Reverse Transcriptase Complex--Chemical key to 
     replication of AIDS virus
       Carter--Human Serum Albumin--Binds and transports drugs and 
     other materials
       Ward--Recombinant Bacterial Luciferase--Protein responsible 
     for bioluminescence in open oceans
       Frankel--Recombinant Ricin A Chain--Component in immunotixs 
     used as therapeutic drugs
       Yonath--Ribosome-30S subunits--Ribosome subunit where 
     genetic code is translated to proteins
       McPherson--Satellite Tobacco Mosaic Virus--First virus 
     crystallized

                            STS-49--May 1992

       Long--Bovine Insulin

                        STS-50/USML-1--June 1992

       Eggleston--Aridicin Aglycone--Industrial antibiotic
       Ward--Bacterial Luciferase--Protein responsible for 
     bioluminescence in open oceans
       Knox--Beta Lactamase--Enzyme that destroys antibiotics
       McPherson--Canavalin--Degrades anticancer drugs
       Knox--DD-Ligase from e. coli--Enzyme which biosynthesizes 
     bacterial cell walls
       Knox--DD-Ligase from S. tymp--Enzyme which biosynthesizes 
     bacterial cell walls
       Sundaralingam--DNA Dodecamer CGTTTTAAAACG--DNA sequence of 
     interest in fundamental research
       Sundaralingam--DNA Dodecamer: CGAAAATTTTCG--DNA sequence of 
     interest in fundamental research
       DeLucas--Factor-D--Enzyme responsible for activation of the 
     complement system
       Sundaralingam--Flavodoxin--Involved in biological oxidation 
     and reduction reactions
       Carter--gp 41 antibody of HIV-1--Antibody recognizes 
     component of AIDS virus
       Ward--Green Flourescent Protein--Protein found in marine 
     bioluminescent jellyfish
       Arnold--HIV Reverse Transcriptase Complex--Responsible for 
     copying genome of the AIDS virus
       Navia--HIV-1 Protease--Drug target for HIV treatment
       Meehan--Horse Serum Albumin--Most abundant serum protein
       DeLucas--Human Aldehyde Reductase--Enzyme implicated in the 
     development of diabetic complications
       Weber--Human alpha-Thrombin--Serine protease involved in 
     coagulation
       Navia--Human Proline Isomerase--Drug target for anti-
     rejection treatments
       Carter--Human Serum Albumin--Binds and transports drugs and 
     other materials
       Suddath--Human Transferrin--Major iron transport protein in 
     serum
       Nagabhushan--Interferon Alpha-2b--Potential antiviral and 
     anticancer agent
       Nagabhushan--Interleukin-4--Potential antitumor agent
       Voet--Lac Operator DNA--Sequences involved in DNA 
     expression
       Lu--Lac Repressor--Regulates the expression of lactose 
     operon in e. coli
       Nauman--Lysozyme--Model protein
       Elnspahr--Malic Enzyme--Enzyme isolated fro a parasitic 
     nematode
       McPherson--Mouse Monoclonal Antibody--Antibody against dog 
     lymphoma

                      STS-47/SL-J--September 1992

       Betzel--Epidermal Growth factor Receptor--Growth factor 
     receptor associated with tumors
       DeLucas--Factor D--Enzyme responsible for activation of the 
     complement system
       Albara--Lysozyme--Model protein
       McPherson--Mouse Monoclonal Antibody--Antibody against dog 
     lymphoma
       Albara--Peroxidase--Enzymes that catalyze oxygen
       Yang--TRP-RS-IRNA TRP Complex--Plays role in protein 
     formation

                          STS-52--October 1993

       Long--Interferon alpha-2b--Potent antiviral and anticancer 
     agent
       Frankel--Recombinant Ricin-A Chain--Component in immunotixs 
     used as therapeutic drugs
       Carter--Recombinant Serum Albumin--Binds and transports 
     drugs and other materials
       Naumen--Thermolysin--Model protein
       Navia--Thermolysin--Used in potential method for producing 
     aspartame
       Einspahr--Two domain CD4--Product being tested as AIDS 
     treatment
       Meehan--Urease--Urease inhibitors might have agricultural 
     applications
       DeLucas--Lysozyme--Model Protein
       Lu--Lac Repressor--Regulates the expression of lactose 
     operon in E. coli

                           STS-57--June 1993

       Carter--Human Serum Albumin--Binds and transports drugs and 
     other materials
       Cook--Interferon alpha-2b--Potent antiviral and anticancer 
     agent
       DeLucas--Lysozyme--Model protein
       Naumann--Ribonuclease S
       Einspahr--Malic Enzyme--Development of anti-parasite drug
       Long--Human Insulin--Facilitates the incorporation of 
     glucose into cells
       Weber--Human alpha-Thrombin--Serine profese involved in the 
     final step of the coagulation cascade

                        STS-51--September, 1993

       Long--Interferon Alpha-2b--Potent antiviral and anticancer 
     agent
       After Spacelab-1, simple hand held devices were used by 
     Charles Bugg (University of Alabama at Birmingham) and his 
     collaborators to subsequently grow crystals on a series of 
     space shuttle flights (1985-1986). These experiments 
     contained only a fraction of a milliliter of growth solution 
     and had no temperature control but excellent crystals were 
     obtained for human serum albumin, human C-reactive protein, 
     canavalin, and con-canavalin B, which appeared to diffract to 
     higher resolution than those grown on Earth. The hardware 
     developed and repeatedly refined for these experiments 
     utilized the vapor diffusion crystal growth technique, a more 
     technically difficult method than the liquid/liquid diffusion 
     technique of Littke's experiment. These was an important 
     evolutionary step for the microgravity protein program. Since 
     most ground investigators also used the vapor diffusion 
     technique, space results could now be directly compared to 
     the extensive protein data already collected from Earth 
     laboratories.
       While these early exploratory experiments indicated that 
     larger protein crystals could be grown in space, the 
     scientific community was not yet convinced that these space 
     crystals exhibited significantly improved internal order. 
     This resistance was due, in part, to the lack of a rigorous 
     theoretical framework for understanding protein crystal 
     growth in general and interpreting the spacelab results in 
     particular. During the hiatus following the 1986 Challenger 
     accident, an increased emphasis was placed on developing a 
     fundamental understanding of protein crystal growth 
     mechanisms. The field had also begun to attract the attention 
     of investigators with considerable experience in fluid 
     mechanics and crystal growth theory, and substantial advances 
     were made in ground research during this period. As a result 
     of lessons learned at the 1986 Stanford conference, many 
     investigators suspected that temperature might be an 
     important control parameter for PCG. This concern led to the 
     search for a phase diagram and an in-depth study of 
     temperature's influence over solubility. In 1987, Ed Mechan 
     et al. at the University of Alabama published a landmark 
     paper of the phase diagram of lysozyme including salt 
     concentration, pH, and temperature as parameters.\4\ This 
     work illustrated that changes in temperature could alter the 
     solubility of proteins under the right conditions. Mechan's 
     work with lysozyme generated a great deal of interest in 
     using temperature shifts to control protein crystallization 
     and a later generation of flight hardware was designed to 
     take advantage of this technique.
       When PCG flights resumed in September 1988 aboard STS-26, 
     the experiment hardware had been redesigned to allow it to be 
     accommodated in a constant temperature incubator during the 
     flight. The unprecedented success achieved in growing large, 
     high quality protein crystals on that mission convinced many 
     formerly skeptical protein investigators of the utility of 
     the microgravity environment. In the STS-26 experiment, 
     microgravity-grown crystals of gamma-interferon D, porcine 
     elastase, and isocitrate lyase were larger, displayed more 
     uniform morphologies, and yielded diffraction data to 
     significantly higher resolutions than the best crystals of 
     these proteins grown on Earth.\5\
       By 1989 the microgravity protein growth program had 
     undergone considerable expansion, with a large number of co-
     investigators from academia and industry participating. These 
     investigators contributed a wide range of biological 
     molecules that could be used for evaluating the effects of 
     microgravity on protein crystal growth and for developing 
     more advanced techniques for crystal growth in space. This 
     trend has continued to the present time with over 50 co-
     investigators involved in the 1992 flight of USML-1.
       Changes have also continued in the refinement of both 
     flight hardware and crystal growth techniques as greater 
     experience is gained on each mission. For example, the malic 
     enzyme protein had repeatedly failed to crystallize in 
     microgravity prior to 1992. Through a combination of ground 
     and flight testing it was determined that, despite the mixing 
     protocols used, complete mixing of the viscous experiment 
     solution was not occurring in orbit. Then on USML-1 a hands-
     on technique, allowed by the presence of a glovebox and the 
     abilities of the highly skilled protein cystallographer Larry 
     DeLucas as Payload Specialist, enabled the growth of large 
     high-quality crystals of malic enzyme. More recent 
     modifications to the syringes used in the crystal growth 
     hardware will produce more turbulent on-orbit mixing of 
     experiment solutions, thus expanding flight opportunities for 
     proteins requiring the use of viscous solutions.
       Since 1988 ground research on proteins has continued to 
     complement the findings of flight experiments in several 
     ways. Knowledge gained from the space results has been used 
     by investigators to develop more successful methods of 
     growing proteins on Earth, and at the same time ground work 
     has yielded new insights into the underlying mechanisms of 
     crystal growth. The latter includes research such as that 
     headed by Marc Pusey at the Marshall Space Flight Center on 
     the nucleation and pre-nucleation stages of crystal growth, 
     and by Franz Rosenberger (University of Alabama at 
     Huntsville) on the temperature dependence of protein 
     solubilities. Much of the ground-based work on the mechanisms 
     of protein crystallization has been performed at the 
     University of Alabama's Center for Macromolecular 
     Crystallography which was established by NASA's Office of 
     Commercial Programs in 1985 in order to promote commercial 
     research in protein crystallography. As a result of ground 
     and flight studies, a number of theoretical models have been 
     developed to explain the beneficial effect of low gravity on 
     protein crystal growth. Hardware planned for future missions 
     will test some of these theories by allowing direct 
     observation of crystal nucleation and dynamic control of 
     crystal growth conditions.
       Over the course of the last ten years, many more proteins 
     have been flown aboard the shuttle and/or studied on the 
     ground than can be discussed here. These range from an iron 
     transport protein called human serum tranferrin, to 
     antibodies expressed against the AIDS virus. American Bio-
     Technologies Inc., the major world supplier of synthetic HIV 
     proteins, recently signed a cooperative agreement with NASA 
     to conduct structure oriented AIDS related research. The 
     structural biology research group at MSFC, which recently 
     published the first structure of a human antibody that 
     recognizes the AIDS virus, will use its expertise to grow 
     crystals and perform structural analysis on the storehouse 
     of HIV proteins provided by American Bio-Technologies. A 
     few examples of other proteins for which exceptional 
     results have been obtained, are given below.
       Porcine elastase. A number of well-formed elastase crystals 
     in the range of 0.5 to 2.1 mm were obtained from six 
     crystallization experiments flown on STA-26 in 1988. 
     Comparison of data for a space-grown crystal with Earth-grown 
     crystals revealed that the space crystal yielded 
     significantly more data at all resolution ranges. This data 
     allowed significant improvements to be made in the 
     understanding of the protein structure, which in turn has led 
     to the use of porcine elastase in current research on a new 
     class of inhibitors for treating emphysema.
       Gamma interferon D. Two crystals of this protein were 
     obtained from STS-26 which were larger than the best that had 
     ever been produced on the ground; one was approximately 50% 
     larger than the largest crystal that had been obtained 
     previously. These large space-grown crystal also displayed an 
     increase in resolution data, revealing that the space grown 
     crystal did indeed have a higher internal molecular order, 
     and allowing the protein structure to be determined for the 
     first time. Pharmaceutical companies are interested in using 
     gamma-interferon as a possible drug for cancer therapy.
       Isocitrate lyase. On STS-26, these proteins formed prisms 
     as large as 0.4 X 0.25 X 0.04 mm which yielded better 
     intensity data throughout the resolution range than any 
     previous Earth crystal.\6\ The understanding gained from 
     these results was used to redesign ground experiments, and 
     the more compact protein crystals of isocitrate lyase seen in 
     space have now been replicated on Earth by using vapor 
     diffusion cells which limit the area available for 
     evaporation.
       Human Serum Albumin. The work done with human serum albumin 
     (HSA), which is the most abundant protein in the circulatory 
     system, provides a good example of knowledge evolving through 
     the ground and flight programs. In 1986 high quality HSA 
     crystals were grown aboard STS-24. In 1989, growth techniques 
     developed in preparation for that flight resulted in the 
     growth of similar crystals on the ground that allowed the 3-
     dimensional molecular HSA structure to be determined to a 
     resolution of six angstroms. At a recent mission review Dr. 
     DeLucas reported that exceptionally high quality crystals of 
     HSA grown were grown aboard IML-1 in 1992, and the results 
     have allowed the protein's structure to be further refined. 
     The published results of this work, led by Daniel Carter at 
     MSFC, are considered a breakthrough in rational drug design 
     due to the potential utility of HSA for the transport of many 
     biological and pharmaceutical molecules in the bloodstream. 
     The structures of a number of other albumins have also been 
     refined and comparisons of these structures are revealing 
     a wealth of information regarding the evolution and 
     chemistry of those important macromolecules.
       Satellite Tobacco Mosaic Virus (STMV). STMV is a common 
     plant pathogen and one of the smallest viruses known. In 
     1992, crystals of STMV were grown aboard IML-2 and according 
     to the investigator, Alexander McPherson (University of 
     California, Riverside) they yielded the ``best resolution 
     data obtained on any virus crystal, by any method, 
     anywhere''. The STMV crystals obtained were 15 times the 
     volume of any seen in the laboratory and their morphology 
     indicated that growth was still incomplete at the end of the 
     eight day mission. Analysis of these crystals not only 
     greatly extended the structural resolution of the virus but 
     also allowed visualization of the nucleic acid contained in 
     STMV for the first time. Some STMV crystals grown at 4 deg.C 
     in the Vapor Diffusion Apparatus formed hexagonal plates (a 
     habit rarely seen in the laboratory) of exceptional size (1.5 
     mm) and quality. The results of the canavalin and STMV 
     experiments were published in Protein Science, Oct. 1992.
       Malic enzyme. Malic enzyme, which has potential use in the 
     development of antiparasitic drugs, was among the proteins 
     benefiting from the program's evolving understanding of how 
     to optimize conditions for space PCG. After unsuccessful 
     attempts to grow crystals of this protein on two previous 
     flights, the 1992 flight of USML-1 yielded the best malic 
     enzyme crystals ever grown.
       Factor D. The longest crystal ever seen of factor D, was 
     also grown on this mission. By combining data from USML-1 and 
     ground-grown crystals, investigators have now successfully 
     determined the three dimensional molecular structure of this 
     protein. This represents the first structure of a type of 
     immune system protein known as a complement protein, ever 
     determined at atomic resolution.
       Ten years of spacelab experiments have clearly established 
     that protein crystals of superior size and quality, capable 
     of providing increased structural data, can be grown in 
     microgravity. Some investigators believe that the higher 
     quality of the crystals grown in microgravity is linked in 
     part to the slower rate of growth that is possible there. The 
     improving technology and methods used in orbit have allowed 
     investigators to make good use of the opportunities available 
     on spacelab in the past. Aboard Space Station the much longer 
     growth periods, and ability to perform continuing adjustments 
     between experimental series, will provide the opportunities 
     needed for the evolution of this science.
       Tissue Culturing. Cell culturing, the growth of cells 
     outside the body, allows many tests and studies that cannot 
     be conducted on whole organisms. Concentrations of drugs that 
     are toxic for the test animal as a whole can be readily 
     studied in cultured cells, where the delicate physiology of 
     the entire animal is not present to hinder or complicate the 
     drug study. Separate cell types can also be examined in 
     culture to isolate and characterize cell function.
       Work on cell culturing systems during the last decade at 
     Johnson Space Center (JSC) has led to a breakthrough in 
     bioreactor technology that is advancing the state-of-the-art 
     in growing normal and cancerous mammalian tissues. Through 
     studies on the effect of fluid flow on tissue cultures, NASA 
     scientists have developed a ground-based bioreactor that 
     attempts to simulate microgravity's effects on growing 
     tissues by randomizing the gravitational vector. This 
     rotating bioreactor keeps cells suspended in a culture medium 
     without the turbulence associated with standard cell 
     culturing techniques, while still maintaining an adequate 
     flow of oxygen and necessary nutrients. The low-shear 
     culturing environment provided by the bioreactor promotes 
     cell aggregation and differentiation, allowing the formation 
     of three-dimensional tissue which more closely resembles in 
     vivo tissue than cells grown using conventional culturing 
     methods.
       The NASA bioreactor is composed essentially of a 
     cylindrical, hollow vessel that is filled with cells and 
     microcarrier beads. This cylinder is continuously rotated 
     around a horizontal axis. The liquid inside the vessel is 
     coupled by viscosity to the rotating wall and begins turning 
     with the wall as a single mass. The cells and carrier beads 
     in the liquid media are carried along with the rotating 
     liquid mass, and this randomizes the gravity vector 
     experienced by the cells. This prevents them from sedimenting 
     out, and they are maintained in a homogeneous suspension 
     throughout the growth media without the use of shear-inducing 
     impeller blades. The end result of this design is that very 
     little shear stress is applied to the cells and beads so that 
     the only residual shear forces in the culture vessel arise 
     from the motion of microcarriers in the media and the contact 
     that the microcarriers occasionally make with the wall and 
     each other.\7\
       Although a variety of other research cell culturing 
     technologies currently exist, such as static matrix 
     culturing, roller bottles and stirred suspension cultures; 
     these technologies generally suffer from one or more serious 
     limitations. These include monolayer cell cultures, limited 
     diffusion of nutrients, difficult cell recovery, or excessive 
     cell agitation. In contrast, the fluid dynamic principles 
     upon which the bioreactor operates offer the advantages of 1) 
     co-location of cells, including those with different 
     sedimentation rates, 2) extremely low fluid shear stress and 
     turbulence, 3) three-dimensional spatial freedom and 4) 
     effective gas and nutrient transfer to the cells.\8\
       The patent for the basic rotating wall vessel (RWV) design 
     of the JSC bioreactor was issued to NASA in 1991. Additional 
     patents have also been issued for a number of modified RWV 
     designs, technologies incorporated in the RWV, and RWV 
     culturing techniques. Investigators credited with important 
     roles in the development of bioreactor designs include Ray 
     Schwarz, Tinh Trinh and Thomas Goodwin of Krug Life Sciences 
     Inc., astronaut David Wolf, J. Jessup of Harvard Medical 
     School, and Mary Pat Moyer of the University of Texas at San 
     Antonio. In recent years Glenn Spaulding of JSC has overseen 
     further development of the bioreactor and the refinement of 
     the associated cell culturing techniques in collaboration 
     with a number of outside investigators.
       Investigators performing medical research have been quick 
     to recognize the enormous potential of the rotating wall 
     vessel and have suggested a wide range of uses. In addition 
     to the more standard cell studies, these have included the 
     growth of large tissue masses for transplant, the cultivation 
     of normal and cancerous cells together in 3-dimensional 
     environment in order to observe their interactions, isolation 
     of tissue specific growth factors, and the investigation of 
     cellular signaling mechanisms. Since the development of the 
     RWV a number of investigators have entered into 
     collaborations with NASA in order to take advantage of the 
     technology's unique features, and a wide range of cell types 
     have been successfully cultivated. Some of the cell culturing 
     accomplishments reported by JSC in 1991 were: (1) First in 
     vitro Norwalk viral culture, (2) First normal human intestine 
     culture, (3) First 80-day normal human lung culture and the 
     (4) First advanced glioma culture.
       Over the last few years investigators have used the RWV to 
     study an increasing variety of cell lines ranging from skin 
     tissue to brain cancer. The results of a few of these 
     investigations are discussed below.
       Glioma. Glioma cell culturing is one of the early successes 
     with the rotating wall bioreactor. Glioma cells are cancers 
     of the tissue which surround nerve cells in the brain. In 
     1991 JSC investigators Garry Marley and Steve Gonda of JSC 
     and Mary Lou Ingram of Huntington Beach Medical Center in 
     Pasadena, reported that a three dimensional model of a human 
     glioma had been reproduced in a modified version of the NASA 
     bioreactor.\9\ In previous research with in vitro human tumor 
     cultures, the features of a fully developed tumor, such as a 
     central hypoxia, had failed to develop. However, when the 
     NASA bioreactor was utilized, the spherical aggregates of 
     cells (up to 2.5mm in diameter) achieved were at least 10 
     times the volume of previously reported cultured glioma 
     colonies. When these spheres were sectioned, at least three 
     different cell morphologies were discovered and the central 
     hypoxia, characteristic of tumors, was evident.\10\
       Skeletal Tissue. Large cartilage tissue masses (1 cm) have 
     been grown in the NASA bioreactor, exceeding the previous 
     limit of about 3mm obtained with conventional culturing 
     methods.\11\ Growth of mouse limb cells in the RWV have 
     resulted in the formation of aggregates which continue to 
     increase in size over the 65-day culture period. Of 
     particular interest in those experiments, was the observation 
     of cell characteristics that previously had only been seen in 
     space-grown cells. This lends support to the argument that 
     the RWV creates conditions similar to microgravity, and 
     therefore may provide an opportunity to use a relatively 
     simple, low maintenance system to study certain changes 
     produced in microgravity. In the case of skeletal tissue, 
     such a system would be especially useful since the human 
     skeleton is profoundly affected by gravitational changes 
     during space flight. Bone, Cartilage and ligaments of 
     space-flown rats have shown significantly altered 
     differentiation and bone demineralization; and negative 
     calcium balance is observed in astronauts. Other 
     investigators are studying the use of the RWV as a culture 
     system to grow large cartilage tissue masses for implants. 
     Cartilage implants would be created by growing cartilage 
     from a patient on biodegradable scaffolding, and then 
     implanting the final tissue mass back into the 
     patient.\12\
       Ovarian Cancer. Cancer of the ovary is the leading cause of 
     death from gynecologic malignancy and investigators consider 
     the development of in vitro models critical to its study.\13\ 
     Satisfactory culture systems for ovarian tumor cells have 
     been limited in the past because of the poor survival of 
     patient tumor cells grown in primary culture. In contrast to 
     the results obtained from conventional culture methods, 
     ovarian tumor cells cultured in a RWV formed three-
     dimensional cellular aggregates that were composed of 
     multiple cell types, such as existed in the original tumor 
     specimen. Findings from this RWV study were judged to have a 
     fundamental impact on the theory of mullerian tumor 
     development.
       Intestinal and Colon Tissue. Perhaps the most successful 
     culturing attempt to date has been the culture of intestine 
     cells. Prior to the NASA RWV, all attempts to generate small 
     intestine from normal primaries and get fully differentiated 
     tissue had failed. However intestine cells grown in the RWV 
     have exhibited a highly organized structure, including 
     microvilli and crypts characteristic of this tissue. 
     Appropriate biochemical markers were present as well. Two 
     human colon adenocarcinoma cell lines, HT-29 and HT-29KM, 
     grown in this culture system developed three-dimensional 
     tissue masses 1.0-1.5 cm in diameter. Investigators reported 
     that the masses displayed glandular structures, apical and 
     internal glandular microvilli, tight intercellular junctions, 
     desmosomes, cellular polarity, sinusoid development, 
     internalized mucin, and structures akin to normal colon crypt 
     development.\7\
       While the RWV offers many advantages to cell growers, it 
     can mimic the beneficial effects of microgravity only to a 
     certain extent. After a maximum of perhaps three months, cell 
     aggregates in the RWV become too large to remain suspended in 
     solution. To address this issue, miniaturized flight versions 
     of the RWV have been developed for use in the microgravity 
     environment, where the decreased shear forces may allow even 
     more extensive tissue development than on Earth. The only 
     requirement for rotation in space is to drive the 
     distribution of oxygen and nutrients to the cells, allowing 
     the shear forces acting on the cells to be reduced by orders 
     of magnitude. To date, space experimentation has consisted of 
     test flights for the purpose of calibrating the bioreactor 
     for use in a low gravity environment. In the future the 
     bioreactor will be used to grow a variety of tissues in a low 
     gravity environment where tissue masses may grow to sizes 
     and cell differentiation far beyond what can be achieved 
     on the ground.


                         iv. materials research

       The goals of materials research in space during the last 
     ten years have been to use the unique characteristics of the 
     space environment to better understand the processes by which 
     various materials are produced and to manipulate the 
     properties of those materials. The role of gravity-driven 
     convection in materials processing has been studied for a 
     wide range of materials (Table 2), including electronic and 
     photonic materials, metals, alloys, composites, glasses, 
     ceramics, and polymers.
       Interest in materials processing in space began to evolve 
     in the late 1950's from a number of different disciplines. In 
     considering the likely behavior of liquids and solidification 
     processes in the low-gravity environment of an orbital 
     spacecraft it was recognized that this environment might be 
     useful for a variety of unique processes. This prompted a 
     number of experiments utilizing drop towers, research 
     aircraft flying parabolic trajectories, and small ``carry on 
     experiments'' on the last several Apollo flights. The 
     knowledge gained from these early experiments was used to 
     develop the more sophisticated investigations which later 
     flew on Skylab, Apollo-Soyuz and Spacelab.\14\
       The materials-processing flight experiment program began in 
     1971 with a set of demonstration experiments performed on the 
     Apollo 14 lunar mission.\15\ During the trans-Earth coast 
     period of that flight, a set of experiments was performed 
     which verified that, in low gravity, mixtures of materials of 
     different densities remain separate in their combined liquid 
     state and during solidification. In other words, the 
     materials do not settle into different layers because of 
     sedimentation as they do on Earth. This set of experiments, 
     referred to as the composite casting demonstration, is of 
     special interest because it was conducted in the first space 
     processing furnace, a precursor to some of the Skylab 
     apparatus.\14\
       Drop tower tests also proved to be of considerable value in 
     the verification of experimental concepts and the development 
     of apparatus flown on Skylab in the early 70's. One 
     experiment for example, involved the dispersion and 
     solidification, in a drop tower, of the two normally 
     immiscible elements gallium (Ga) and bismuth (Bi).\14\ The 
     experiment produced a solid mixture, of finely dispersed Ga 
     and Bi particles, which exhibited a unique temperature 
     dependence of the electrical resistivity quite unlike that 
     found in the pure materials. These results suggested that 
     immiscible materials processed in space could form an 
     entirely new class of electronic materials and led to the 
     development of similar Skylab experiments. The longer periods 
     of microgravity achieved in parabolic aircraft flights (10-20 
     seconds) permitted investigators to verify the functioning of 
     many Skylab experiments as they were being developed.

                                       TABLE 2: MATERIALS FLOWN SINCE 1982                                      
----------------------------------------------------------------------------------------------------------------
           Date                        Mission                    Instrument                   Material         
----------------------------------------------------------------------------------------------------------------
3/22/82....................  STS-3......................  Monodisperse latex reactor  Monomer: styrene, water   
6/27/82....................  STS-4......................  Monodisperse latex reactor  Polymer                   
4/4/83.....................  STS-6......................  Monodisperse latex reactor  Monomer: styrene and water
6/1/83.....................  SPAR 10....................  Casting Furnace...........  Aluminum-copper           
6/1/83.....................  SPAR 10....................  Low-Gravity exothermic      Cu-Cu2O-O                 
                                                           heating cooling apparatus.                           
6/1/83.....................  SPAR 10....................  Automated directional       Manganese-bismuth         
                                                           solidification system.                               
6/18/83....................  STS-7......................  Single axis acoustic        Al2O3, Ga2O3-CaO-SiO2,    
                                                           levitator.                  Ga2O3-CaO, Na2O-B2O3     
6/18/83....................  STS-7......................  Gradient general purpose    GeSe, Xe                  
                                                           rocket furnace.                                      
6/18/83....................  STS-7......................  Monodisperse latex reactor  Monomer: styrene and water
2/3/84.....................  STS 41-B...................  Monodisperse latex reactor  Monomer: styrene, water   
2/3/84.....................  STS 41-B...................  Acoustic containerless      ZrF4, BaF2, LaF3          
                                                           experiment system.                                   
4/29/85....................  Spacelab 3.................  Vapor crystal growth        Mercury-iodide            
                                                           system.                                              
4/29/86....................  Spacelab 3.................  Fluid experiment system...  Triglycine sulfate        
6/17/85....................  STS 51-G...................  Automated directional       Bismuth-manganese         
                                                           solidification furnace--1                            
                                                           (low temperature version).                           
10/30/85...................  STS-61A....................  Single axis acoustic        Al2O3, Ga2O3-CaO-SiO2,    
                                                           levitator.                  Na2O-B2O3, Ga2O3-CaO     
10/30/85...................  STS-61A....................  Gradient general purpose    GeSe, Xe                  
                                                           rocket furnace.                                      
10/30/85...................  STS-61A....................  Gradient general purpose    Lead-tin-telluride        
                                                           rocket furnace.                                      
1/12/86....................  STS-61C....................  Automated directional       Colbalt-samarium eutictics
                                                           solidification furnace--2   and peritectics          
                                                           (high temperature                                    
                                                           version).                                            
1/12/86....................  STS-61C....................  Electromagnetic levitator.  Nickel-Tin                
9/29/88....................  STS-28.....................  Automated directional       Manganese-bismuth         
                                                           solidification furnace--2                            
                                                           (high temperature                                    
                                                           version).                                            
6/5/91.....................  SLS-1......................  Gallium arsenide furnace..  Selenium doped gallium    
                                                                                       arsenide                 
1/22/92....................  IML-1......................  Vapor crystal growth        Mercuric iodide           
                                                           system.                                              
1/22/92....................  IML-1......................  Fluids experiment system..  Triglycine sulfate        
                                                                                       solution                 
1/22/92....................  IML-1......................  Fluids experiment system..  Water, ammonia chloride   
3/24/92....................  STS-45.....................  ..........................  Gallium arsenide          
6/25/92....................  USML-1.....................  Zeolite crystal growth      Aluminum and silicon      
                                                           furnace.                                             
6/25/92....................  USML-1.....................  Crystal growth furnace....  Cadmium-zinc-telluride    
6/25/92....................  USML-1.....................  Glovebox..................  Dow 200 silicone oils with
                                                                                       varying surface tensions 
6/25/92....................  USML-1.....................  Crystal growth furnace....  Mercury-cadmium-telluride 
6/25/92....................  USML-1.....................  Crystal growth furnace....  Mercury-zinc-telluride    
6/25/92....................  USML-1.....................  Crystal growth furnace....  Selenium doped gallium    
                                                                                       arsenide                 
6/25/92....................  USML-1.....................  Glovebox..................  Water, tellon             
10/22/92...................  USMP-1.....................  MEPHISTO..................  Bismuth and bismuth-tin   
----------------------------------------------------------------------------------------------------------------

       In broad terms, one very important outcome of the numerous 
     materials processing experiments performed on Skylab, was the 
     realization that microgravity experiments were sensitive to a 
     host of secondary and tertiary factors that were not normally 
     significant in a one gravity environment. Space experiments 
     have demonstrated that when the manifestations of 
     gravitational forces (such as sedimentation and gravity-
     driven convection) are reduced other forces such as surface 
     tension and the wetting characteristics of the materials for 
     their containers become predominant. Since those early 
     experiments, the improvements made in analytical techniques, 
     theoretical treatments and experimental hardware, are 
     allowing investigators to explore those sensitivities 
     quantitatively.
       During the last decade much of the materials science 
     research sponsored by the Microgravity Science and 
     Applications Division has been directed at improving material 
     properties and creating new materials through an improved 
     understanding of materials processes. Results from 
     microgravity experiments have acted to focus attention on 
     determining the importance of surface tension driven 
     convection in industrially important processes, such as 
     Czochralski crystal pulling, and the floating zone 
     configuration for growing semiconductor single crystals. 
     Virtually all of the world production of silicon produced in 
     single crystal form is produced by these two techniques.
       A portion of MSAD research is also funded to carry out 
     investigations in areas where theories are incomplete. As a 
     result of NASA sponsored research, present theories and 
     models are extended to encompass a wider range of problems. 
     For example, new algorithms and mathematical techniques were 
     developed by Julian Szekeley of the Massachusetts Institute 
     of Technology to model the behavior of metallic melts that 
     will be electromagnetically levitated in microgravity. They 
     have subsequently been applied in the metals and 
     semiconductor industries for the purpose of equipment design 
     and quantitative prediction of important materials processing 
     parameters in induction furnaces, induction stirring 
     processes, continuous casting of metal alloys, magnetic 
     damping of turbulent convection in high temperature 
     semiconductor melts, and cold crucible processing of 
     materials with highly corrosive melts.

                           Metals and Alloys

       Dendrites are tiny crystalline structures formed from 
     molten materials during solidification. The size, shape, and 
     orientation of the dendrites determine to a major extent the 
     strength and durability of metallic systems including steel, 
     aluminum, and superalloys. Because many industrially 
     important metal alloys solidify by dendritic processes, 
     enhancing the basic understanding of dendritic solidification 
     is essential to improving industrial production techniques. 
     During the 70's and 80's Martin Glicksman et., al. of 
     Rensselaer Polytechnic Institute performed extensive work 
     with succinonitrile (SCN), a transparent analog to metals, in 
     order to test current theories of dendritic growth. In the 
     course of this research such a large historical database was 
     compiled that SCN has arguably become the best studied 
     dendritic system in the literature and the reference standard 
     for almost all other work on dendritic growth. Findings from 
     the ground-based work demonstrated the limitations of 
     prior growth models, which did not adequately account for 
     the effects of gravity driven convection. Unfortunately it 
     is only at small undercoolings, where gravity effects 
     dominate, that kinetic conditions are suitable for 
     checking dendritic growth theories (Fig. 6). The 
     Isothermal Dendritic Growth Experiment (IDGE) was 
     developed over the last several years in order to study 
     the effect of undercooling or dendritic development in the 
     absence of gravity-driven fluid flows. The space 
     experiment, scheduled for March 1994 on the second flight 
     of the United States Microgravity Payload series, should 
     provide the critical test of these theories.
       Other model materials for metals, such as ammonium chloride 
     (NH4Cl), have also proven useful to investigators studying 
     solidification behavior. Angus Hellawell (Michigan 
     Technological University) used this system to study the 
     formation of channels of low density materials during casting 
     that produce ``freckling'' in metals, collecting considerable 
     information on the interaction of dendritices with the mushy 
     zone. The occurrence of freckling in commercial materials, 
     such as stainless steel and super-alloys, tends to limit the 
     useful composition range of many alloys. Mary Helen McCay and 
     Dwayne McCay (University of Tennessee Space Institute) have 
     also performed extensive optical studies of the liquid-solid 
     interface region during alloy solidification by using NH4Cl. 
     Experiments aboard suborbital rockets and parabolic aircraft 
     flights revealed that the spacing of dendrite arms varies 
     with g-level, indicating that gravity affects the 
     concentration fields immediately adjacent to the dendrite 
     arms. In order to better study solidification without the 
     masking effects of gravity, the system was flown aboard IML-1 
     in 1992 as the Casting and Solidification Technology 
     experiment. The growth rates of dendritic fronts were 
     generally observed to be much faster in microgravity (factor 
     of 2) and the dendrites developed a much finer, longer 
     structure than seen on the ground. In fact the tip growth 
     occurred at nearly the isotherm translation rate. Preliminary 
     analysis of the results has indicated that, in microgravity, 
     only shrinkage and solute diffusion effects cause mass flow. 
     The enormous amount of data collected from the IML-1 
     experiment is still being sifted and comparison with ground-
     based studies is expected to yield considerable insight into 
     the solidification process, including the phenomena which 
     produce freckling.

                          Electronic materials

       Non-silicon based materials often have unique properties 
     not exhibited by the more mature, elemental semiconductor 
     technologies. Examples include, bandgaps which allow direct 
     conversion between light and energy, higher electron 
     mobilities, and improved thermal and radiation tolerance. 
     Much of the materials research sponsored by NASA's 
     microgravity program during the last ten years has been 
     concentrated in areas based on these newer materials, which 
     include various Group III-V compounds (e.g. gallium arsenide) 
     and Group II-VI compounds. However these compound 
     semiconductors still retain stringent requirements for 
     purity, uniformity and perfection. The results of numerous 
     space experiments appear to confirm the expected advantages 
     of growing semiconductor crystals in space, which include 
     improved homogeneity, greater purity, and greater structural 
     perfection.
       Germanium Compounds. One area of long term interest in 
     electronic materials research has been the study of vapor 
     transport to grow semiconductor crystals. Herbert Wiedemeier 
     of the Rensselaer Polytechnic Institute grew germanium 
     selenide (GeSe) and germanium telluride (GeTe) crystals by 
     chemical vapor transport on Skylab and Apollo-Soyuz, and by 
     physical vapor transport on STS-7 in 1985 and STS-61A in 
     1985.\16\ The space grown crystals generally showed greatly 
     improved surface morphology and were nearly free of growth 
     defects, leading to the conclusion that gravity-driven 
     convection has a powerful influence on surface morphology. 
     These experiments were among the earliest flight 
     investigations to clearly demonstrate the superiority of 
     spacegrown crystals over those grown on Earth.
       Mercury Cadmium Telluride (HgCd(Tel). The results of Dr. 
     Wiedemeier's early experiments were incorporated into further 
     ground research using simpler model materials, which led to 
     the development of a flight experiment using a material of 
     technical interest, Hg0.8Cd0.2Te. HgCd(Te is 
     important for its use in infrared detectors and thermal 
     imaging arrays. The first direct measurement of Hg-vacancy 
     concentrations in HgTc. Hg0.8Cd0.4Te and 
     Hg0.6Cd0.4Te was accomplished in the course of the 
     ground work. Such information is valuable for understanding 
     and controlling the formation of defects during the crystal 
     growth process. A layer about 80 micrometers thick of HgCdTe 
     was successfully grown on a CdTe substrate during the 8 hour 
     growth period for the primary sample aboard USML-1 in 1992. 
     Preliminary analysis has revealed a greater than expected 
     improvement in the surface structure of the flight samples 
     compared to ground specimens, and also considerable 
     improvement in both the crystalline perfection and chemical 
     uniformity was measured.
       HgCdTe was also used in solidification studies, such as 
     those performed by Sandor Lehoczky and Frank Szofran of 
     Marshall Space Flight Center, who studied methods of growing 
     homogeneous HgCdTe crystals by solidification from bulk 
     melts. Ground work greatly increased the understanding of 
     gravitational limitations in the growth of bulk semiconductor 
     materials such as HgCdTe. This knowledge was carried over to 
     studies of materials with similar optoelectronic properties 
     such as mercury zinc telluride. (HgZnTe) and mercury zinc 
     selenide (HgZnSe). Zinc substitution appeared to stabilize 
     the crystalline lattice and had the potential to lower 
     defects densities in growing crystals. This work led to a 
     directional solidification experiment, using 
     Hg0.84Zn0.16Te, aboard USML-1 in 1992. Though this 
     experiment was terminated prematurely, 5.5 mm of growth were 
     achieved and this material is currently being analyzed.
       Mercuric Iodide (HgI2). Mercuric iodide, a nuclear 
     detector material capable of allowing radiation levels to be 
     measured over a range of wavelengths, is produced by a 
     physical vapor transport process. Its utility as a room 
     temperature, solid-state detector has generated a great deal 
     of interest among agencies such as NASA and the Department of 
     Energy, as well as private corporations. Potential uses cited 
     by Lodewijk van den Berg of EG&G Energy Measurement Inc. 
     include environmental monitoring and cleanup, detecting lead 
     in the paint of old buildings, tracking radioactive isotopes 
     in physiological tests, and the construction of large array 
     x-ray and gamma ray telescopes. Thus far the use of HgI2 
     has been limited by poor performance factors, such as low 
     charge carrier mobilities and lifetimes, which are related to 
     the structural perfection of the crystal. Research\17\ prior 
     to 1985 had indicated the HgI2 crystal quality was 
     degraded by the effects of gravity (mechanical deformation 
     and irregular convection) during the vapor transport growth 
     process. By growing HGI2 in space it was hoped that 
     higher quality crystals, with improved performance, could be 
     obtained. Another goal of the experimental work led by Dr. 
     van den Berg was to develop a system which could be used in 
     space to perform critical vapor transport measurements, with 
     the quality of the crystal serving as a test of the system's 
     reliability.
       Dr. van den Berg first grew a HgI2 crystal in space 
     about SL-3 in April 1985 using physical vapor transport. The 
     initial characterization of the SL-3 crystal indicated a very 
     high internal order and the measured charge carrier 
     mobilities were at least a factor of two higher than Earth-
     grown crystals at that time. Detector efficiency was better 
     than the best Earth=grown crystal by a factor of seven. As a 
     result of the SL-3 experiment, investigators also learned 
     that precise control of the temperature profile was extremely 
     critical during the growth process. This knowledge was 
     incorporated back in the ground-based work and in subsequent 
     years considerable progress was made in improving the methods 
     used to grow HgI2, resulting in Earth-grown crystals 
     comparable in quality to that obtained from SL-3. Advances 
     were also made during that time in various crystal 
     characterization techniques, such as synchrotron x-ray 
     diffraction imaging. In 1991, a National Institute of 
     Standards and Technology report was published on the use of 
     this technique to re-evaluate several space-grown crystals, 
     including HgI2. The measurements indicated that lattice 
     regularity might be of less importance to the performance of 
     HgI2 than the suppression of additional phases in the 
     crystal. The report concluded that these results were so 
     interesting that, ``extraordinary efforts to thin samples of 
     this material and to support them in innovative ways seems 
     now to be justified.''
       A second HgI2 experiment, performed on IML-1 in 1992, 
     yielded a crystal of higher quality than crystals grown on 
     the ground under the same conditions. Large improvements were 
     also soon in the charge carrier lifetime and mobilities, 
     helping to confirm the SL-3 results. The superior crystals 
     obtained from the two space experiments and the more 
     recent ground work, have recently led to requests by two 
     commercial laboratories to transfer the crystal growth 
     technology to the private sector for use in commercial 
     apparatus development.
       As a result of the IML-1 mission it was also confirmed that 
     convective effects are created by gravity during the vapor 
     transport growth process of HgI2, Previously fluid 
     dynamicists had not believed that such convection could exist 
     due to the extremely low pressures involved. This finding has 
     important ramifications to the field of vapor transport 
     processing in general, and is also expected to lead to 
     further improvements in HgI2 crystal growth techniques 
     used on the ground.
       Magnetic Dampening, In some instances, research in 
     preparation for space experiments in materials science has 
     led to significant leaps forward in the way a large class of 
     experiments and industrial processes are conducted here on 
     the ground. The best known example of this is the use of 
     magnetic damping to retard convective flows during the growth 
     of electronic materials. August F. Witt and Harry C. Gatos at 
     the Massachusetts Institute of Technology developed and 
     applied this technique to an industrially important process 
     for growing semiconductor single crystals (the Czochralski 
     technique) while studying the potential effects of processing 
     crystals in microgravity. Use of this technique by a number 
     of American and Japanese electronic materials companies has 
     brought a new dimension to industrial crystal growth 
     research. It is considered by some to be the primary advance 
     in terrestrial crystal growth research in the last two 
     decades.


                       v. combustion research\19\

       The major objectives of the MSAD combustion research 
     program during the last decade have been to develop 
     understanding of, and define means of controlling and 
     optimizing, combustion processes. Included in the program are 
     studies of premixed gas combustion, gaseous diffusion flames, 
     liquid fuel droplet combustion, particle cloud combustion, 
     flame spread across liquid or solid fuel surfaces, smoldering 
     combustion, and use of combuision processes to produce novel 
     materials. To date, most of the NASA-supported activities 
     have been ground-based, involving analytical modeling studies 
     and testing in microgravity drop towers (2 and 5 seconds of 
     available test time) at Lewis Research Center and in aircraft 
     (LearJet and KC-135) flying parabolic trajectories to produce 
     up to 20 seconds of reduced gravity. However, Robert 
     Altenkirch's (Mississippi State University) Solid Surface 
     Combustion experiment, which requires test times in excess of 
     those which can be achieved in these facilities has been 
     flown several times on the shuttle in order to gather a 
     series of data points required for testing of modeling 
     hypotheses. In those experiments flame spread was studied 
     by igniting paper and plastic in a specially developed 
     chamber and filming the resulting flame shape and 
     propagation. Several other experiments to be flown on 
     shuttle and/or in sounding rockets (which can produce 
     micro-gravity test times of up to 12 minutes) are also in 
     the development phase.
       Microgravity combustion research has demonstrated major 
     differences in structures of various types of flames in 
     microgravity versus normal gravity environments. Significant 
     differences in the sooting characteristics of diffusion 
     flames under these two limiting gravity conditions (of major 
     interest as regards pollutant production from everyday 
     combustion devices) have been observed. Major differences 
     have been documented between the ignition and flame-spreading 
     characteristics of liquids and solids (e.g., plastics, wood, 
     foams, pools of liquid fuels) in microgravity and normal 
     gravity, of major importance as regards fire safety. Besides 
     the immediate practical implications of these results as 
     regards combustion efficiency (energy conservation), 
     pollutant production (environmental considerations) and 
     characterization of materials in terms of flammability (fire 
     safety), these studies have established that better 
     mechanistic understanding of individual processes making up 
     the overall combustion process can be obtained by comparison 
     of result gathered in microgravity vs. normal gravity tests. 
     Potentially, this could lead to major redesign of combustion 
     processes and combustor hardware to yield higher energy 
     conversion efficiency, reduced pollutant production, and 
     increased fire safety on Earth as well as in space.
       Work to date has generated significant interest in the 
     academic combustion community. Numerous publications 
     generated under MSAD funding have been accepted in such 
     prestigious journals as Combustion and Flame, Proceedings of 
     the International Symposium on Combustion, and Combustion 
     Science and Technology. Researchers have some to realize that 
     they can obtain a much better understanding of combustion 
     fundamentals through the extra ``degree-of-freedom'' afforded 
     by experimentation at gravity levels other than normal; and 
     through elimination of a major factor (buoyancy) which tends 
     to obscure some of the more important fundamental phenomena 
     under normal gravity experimentation.
       Specific accomplishments of fundamental and widespread 
     scientific interest and/or practical benefit under the 
     Microgravity Combustion Research activity include:
       (1) Between 1986 and 1991 several new phenomena related to 
     droplet combustion were found in testing in the NASA Lewis 
     drop tower. These included a new slow burning regime for 
     droplets and disruptive burning in pure fuel droplets. 
     Droplet combustion has been termed the most fundamental 
     heterogeneous combustion problem by the combustion science 
     community and is of longstanding interest,
       2) Multiple discoveries, attainable only via microgravity 
     experiments, related to premixed gas combustion (relevant to 
     hazard control and the most basic combustion science) were 
     made between 1986 and 1993. These include self-extinguishing 
     flames, flame balls, flame cylinders, and dilution-enhanced 
     flammability. These discoveries open a new recognition of the 
     stabilization and extinguishment possibilities associated 
     with combustion reactant absorption and product radiation.
       3) The first low-gravity data on Burke-Schumann gas jet 
     diffusion flames (a classical flame configuration treated in 
     virtually all combustion textbooks) were obtained and 
     analyzed in 1991. These data represent the first true 
     verification of this zero-gravity theory available since its 
     original development in 1928.
       4) The first data on turbulent and transitional (from 
     laminar to turbulent) gasjet flames in microgravity were 
     recently obtained (1993) through droptower testing. Leading 
     university researchers believe this type of microgravity 
     investigation offers the most promising path toward 
     development of understanding/prediction of turbulent 
     combustion, of widespread practical interest since most 
     commercial combustors operate in the turbulent regime.
       5) A non-intrusive diagnostic instrument developed over the 
     last three years, for the purpose of determining chemical 
     species concentrations in drop-tower microgravity combustion 
     experiments, has been modified for use in monitoring ammonia 
     concentrations in power-plant smokestacks, an important 
     environmental application.
       6) Microgravity experiments (1988) revealing ``chattering 
     flame propagation'' in freely suspended fuel particle clouds 
     have led to theoretical developments regarding flame-acoustic 
     interactions which have since been revealed to apply to 
     triggering of acoustic instabilities in practical gas 
     turbines.
       7) Initial microgravity data were obtained in 1988 on 
     smoldering combustion and air flow effects on solid and 
     liquid material flammability and flame spread (both of great 
     interest in the fire safety area) revealing a new extinction 
     mechanism (radiative quenching) and a lesser-than-assumed 
     margin of safety in acceptance criteria for use of flammable 
     materials in microgravity environments. These data expand 
     significantly the understanding of material ignition and 
     flamespread phenomena.
       8) A decades-old question about the ability of a candle to 
     burn in near zero-gravity and the nature of the flame in that 
     environment was addressed in a 1992 Shuttle experiment aboard 
     USML-1. Surprising results included the observation of 
     spontaneous flame oscillations prior to extinguishment.
       (9) The first data on soot production (primary and 
     aggregate soot sizes and quantities) in microgravity 
     diffusion flames were collected in 1992; these data represent 
     initiation of new studies on the effects of various 
     parameters on soot generation, growth, and oxidation 
     processes. The understanding which will be obtained from 
     these studies has great potential practical benefits in 
     combustor design and in many manufacturing processes such as 
     carbon-black and carbon-fiber matrix production, and 
     generation of new exotic materials such as fullerenes.


                           yn. fluid physics

       The objective of the microgravity fluid physics program 
     during the last decade has been to improve the understanding 
     of fluid dynamics and transport phenomena where fundamental 
     behavior is limited or affected by the presence of gravity. 
     The study of fluid physics in microgravity encompasses a 
     broad range of topics dealing with such fluid behavior as 
     interfacial phenomena, multiphase flow, and drop dynamics.
       Fluid physics is often considered to be the central science 
     with respect to microgravity research since nearly all 
     processes studied or performed in low gravity involve a 
     liquid phase and must manage liquid behavior. Thus the 
     principles of fluid physics provide the foundation for most 
     type of research performed in a low gravity environment. This 
     includes biotechnology fields such as protein crystal growth, 
     separation sciences, and cell culturing in space, which all 
     involve the motion of either fluid buffers or electrolytes. 
     Materials processing also relies extensively on melting and 
     solidification processes, and these procedures generate 
     complex fluid flows that affect the quality of the final 
     product. Since gases are also fluids, combustion and fire 
     safety in space requires a full understanding of fluid flow 
     and transport. In addition to research considerations, the 
     use of liquid fuels in space propulsion systems means that an 
     understanding of the positions and motion of these fuels in 
     tanks is critical for insuring proper spacecraft functioning. 
     the development of future space technologies will also rely 
     on improved understanding of fluid behavior. Welding in space 
     and energy storage systems relying on solid-liquid 
     transitions involve complex fluid flow issues that are not 
     well understood.\20\ In the future, efficient energy transfer 
     and storage devices will require an understanding of how 
     vapor-liquid systems flow and carry heat, and this requires 
     improved understanding of multiphase behavior in liquids.
       Although the surface forces in space are usually 
     overshadowed on Earth, these forces remain important even at 
     1-g, making the field of interfacial phenomena in fluid 
     physics highly significant for Earth-based processing 
     activities. Welding and crystal growing from the melt on 
     Earth are significantly affected by surface-tension forces 
     which can effectively be studied only in space. Theoretical 
     understanding of convection and mass transport behavior 
     around growing crystals on Earth is also incomplete, and 
     requires insights provided by space research into fluid flow.
       Fundamental and applied studies on the effects of gravity 
     on static and dynamic liquid-gas interfaces have provided 
     information necessary to design and develop propellant 
     management systems that can function effectively in a reduced 
     gravity environment. For example, an Apollo 7 fluids 
     experiment demonstrated that capillary forces could be used 
     to move fluids in fluid management systems in space. This 
     helped prove that scaling laws worked an could be 
     extrapolated to design systems for fluid management which 
     could only be tested on very small scales in 1-g. The use of 
     this knowledge to design propellant systems such as that used 
     in the Centaur vehicle, was considered it to be a major 
     accomplishment of the early space program. While gaps in 
     knowledge still require the use of conservative designs, the 
     successful on-orbit operation of most propellant management 
     systems in vehicles and satellites are directly dependent on 
     many years of low-gravity fluids research.
       Drop Dynamics. An area of fluids research which is 
     particularly difficult to study on Earth is the behavior of 
     free drops. Scientific interest in drop dynamics stems from 
     the many scientific and technological areas in which liquid 
     drops play a role, from studies of rain in the atmosphere to 
     chemical processes. Some early work performed in this area at 
     the Jet Propulsion Laboratory during the latter half of the 
     80's used drop tubes in order to study spherical shell 
     formation, particularly methods of centering bubbles in 
     liquid drops. Techniques were developed for forming shells 
     from glass and plastics and a number of applications were 
     suggested for such shells, including polymer cell 
     encapsulation and bonding to form lightweight, energy 
     absorbing structures. In 1988 a Center for Microgravity 
     Research and Applications was established at Vanderbilt 
     University to further the study of free liquid drops. Taylor 
     Wang of the Jet Propulsion Laboratory (later at Vanderbilt 
     University) performed preliminary experiments aboard SL-3 in 
     1985, using acoustic levitation to suspend and manipulate 
     drops. These experiments were successful in conforming 
     classical theoretical assumptions about drop behavior, but 
     investigators were also intrigued by some of the results 
     which were not expected. For example, under certain 
     conditions, the bifurcation point (when a spinning drop takes 
     a dog-bone shape to hold itself together) occurred earlier 
     than had been predicted. In order to resolve some of the 
     differences seen between experiment and theory, a series of 
     drop experiments were conducted in the more advanced Drop 
     Physics Module flown aboard USML-1 in 1992. The USML-1 
     results agreed well with theory under static conditions and 
     allowed previous flight and ground experimental results to be 
     reconciled with theory as well. Dr. Wang also reported that 
     the USML-1 experiment had produced new insights into other 
     centering mechanism, of spinning compound drops, needed for 
     encapsulating cells. While difficulties with the drop 
     injection system prevented full success from being achieved 
     on this mission, further investigations using somewhat 
     modified hardware are being pursued aboard USML-2 in 1995.
       Surface Tension Driven Convection. Variations in surface 
     tension along the free surface of a liquid, caused by uneven 
     temperature distribution, creates a flow in the bulk liquid 
     known as thermocapillary flow. Since the 1970's most of the 
     advances in understanding the phenomenon of thermocapillary 
     flow resulted from research sponsored by MSAD. Much attention 
     has been given to the study of themocapillary flow in recent 
     years due to its important role in such applications such as 
     crystal growth from melts, two-phase flows with heat transfer 
     and themocapillary migration of bubbles and droplets.\21\ It 
     is known that thermocapillary flow becomes oscillitory under 
     certain conditions but its cause is not completely 
     understood. A number of studies performed during the last 
     decade by Simon Ostrach et. al. of Case Western University 
     have focused on this phenomenon. The results of that 
     experimental work suggested that free surface deformability 
     played an important role in the oscillations. Dr. Ostrach has 
     since described the oscillation as a three-way coupled flow 
     that is among the most complex fluid phenomena yet 
     understood. In order to test these theories, experiments were 
     designed for flight aboard USML-1 and USML-2. The highly 
     successful Surface Tension Driven Convection Experiment, 
     flown on USML-1 in 1992, studied the velocity and temperature 
     fields in detail in non-oscillatory thermocapillary flows. 
     STDCE represented a milestone experiment in NASA's fluid 
     program; using state-of-the-art diagnostics as part of the 
     first combined theoretical, numerical, and experimental study 
     of the thermocapillary flow phenomenon. Preliminary analysis 
     indicates that the temperature data is in good agreement with 
     the Dr. Ostrach's numerical predictions, and data collected 
     during this mission also allowed a complete description of 
     fluid flows which remained steady over an extended period of 
     time.
       Laser Light Scattering. A laser light scattering instrument 
     specifically developed for space experiments on colloidal 
     fluids (liquids containing small particles, such as paint, 
     milk, drilling fluids used in the oil industry, and other 
     suspensions or slurries) has been demonstrated to provide 
     accurate, non-invasive measurement of the size distribution 
     of protein molecules in the human eye. Such distributions are 
     believed to be a direct indicator of the progressive stages 
     of cataract development.

                                  TABLE 3: FLUIDS EXPERIMENTS FLOWN SINCE 1983                                  
----------------------------------------------------------------------------------------------------------------
           Date                        Mission                   Instruments               Experiment title     
----------------------------------------------------------------------------------------------------------------
6/1/83.....................  SPAR 10....................  Acoustic levitation space   Containerless Processing  
                                                           processing rocket           Technology               
                                                           instrument.                                          
6/18/83....................  STS-7 (MEA-A1).............  Isothermal general purpose  Liquid Phase Misability   
                                                           rocket furnace.             Gap: Gradient Cooling    
                                                                                       Experiment & Isothermal  
                                                                                       Plunger Experiment       
1/24/85....................  STS 51-C...................  Storable fluid management   Storable Fluid Management 
                                                           demonstration.              Demonstration            
4/29/85....................  STS-51B (Spacelab 3).......  Geophysical fluid flow      Geophysical Fluid Flow    
                                                           cell.                       Cell Experiment          
4/29/85....................  STS-51B (Spacelab 3).......  Drop dynamics module......  Dynamics of Rotating      
                                                                                       Oscillating Free Drops   
7/29/85....................  STS-51F (Spacelab 2).......  Super fluid helium          Super Fluid Helium        
                                                           experiment package          Experiment               
                                                           cryostat and support                                 
                                                           electronics.                                         
10/30/85...................  STS-61A (MEA-A2)...........  Isothermal general purpose  The Diffusion of Liquid   
                                                           rocket furnace.             Zinc and Lead            
10/30/85...................  STS-61A (MEA-A2)...........  Isothermal general purpose  Liquid Phase Miscibility  
                                                           rocket furnace.             Gap Materials            
1/12/86....................  STS-61C (MSL-2)............  Three axis acoustic         Dynamics of Compound Drops
                                                           levitator.                                           
1/22/92....................  IML-1......................  Critical point facility     Investigation of the      
                                                           with critical fluid         Thermal Equilibrium      
                                                           thermal equilibration       Dynamics of SF6 Near the 
                                                           cell.                       Liquid-Vapor Critical    
                                                                                       Point                    
6/25/92....................  USML-1.....................  Glovebox..................  Nucleation of Crystals    
                                                                                       from Solutions in a Long-
                                                                                       g Environment            
6/25/92....................  USML-1.....................  Drop physics module.......  Science and Technology of 
                                                                                       Surface Controlled       
                                                                                       Phenomena                
6/25/92....................  USML-1.....................  Glovebox..................  Interface Configuration   
                                                                                       Experiment               
6/25/92....................  USML-1.....................  Glovebox..................  Osciliatory Dynamics of   
                                                                                       Single Bubbles and       
                                                                                       Agglomeration in an      
                                                                                       Ultrasonic Sound Field in
                                                                                       Microgravity             
6/25/92....................  USML-1.....................  Glovebox..................  Marangoni Convection in   
                                                                                       Closed Containers        
6/25/92....................  USML-1.....................  Surface tension driven      Surface Tension Driven    
                                                           convection experiment       Convection Experiment    
                                                           apparatus.                                           
6/25/92....................  USML-1.....................  Glovebox..................  Oscillatory               
                                                                                       Thermocapillary Flow     
                                                                                       Experiment               
6/25/92....................  USML-1.....................  Glovebox..................  Directed Orientation of   
                                                                                       Polymerizing Collagen    
                                                                                       Fibers                   
6/25/92....................  USML-1.....................  Astroculture flight         Astroculture              
                                                           hardware.                                            
6/25/92....................  USML-1.....................  Glovebox..................  Solid Surface Wetting     
                                                                                       Experiment               
6/25/92....................  USML-1.....................  Drop Physics Module.......  Drop Dynamics Experiment  
6/25/92....................  USML-1.....................  Drop Physics Module.......  Measurement of Liquid-    
                                                                                       Liquid Interracial       
                                                                                       Tension and the Role of  
                                                                                       Gravity in Phase         
                                                                                       Separation Kinetics of   
                                                                                       Fluid Glass Melts        
8/12/92....................  STS-47 (Spacelab J)........  Get away special..........  Nucleate Pool Boiling     
10/22/92...................  USMP-1.....................  Lambda point experiment...  Heat Capacity Measurements
                                                                                       Near the Lambda Point of 
                                                                                       Helium                   
6/21/93....................  STS-57 (Spacelab-1)........  Get away special..........  Pool Boiling Experiment   
11/10/93...................  STS-60 (Spacelab-2)........  Get away special..........  Pool Boiling Experiment   
----------------------------------------------------------------------------------------------------------------

                                                                                       The advanced technology 
     development activities which enable much of this research 
     is exportable to the U.S. economy. The National Institute 
     of Health is currently considering how to modify this 
     instrument for field tests by medical researchers.
       Modeling Studies. As NASA investigators worked to solve 
     increasingly complex problems in terrestrial and low gravity 
     fluid behavior over the last decade, a need was created for 
     highly sophisticated models of fluid behavior. Since 1986 a 
     great deal of this fluid modeling work has been carried out 
     at the Computational Research Lab at Lewis Research Center in 
     support of various areas of both fluid dynamics and materials 
     research. The lab frequently participates in technology 
     transfer efforts as well, such as a recent consortium formed 
     with B.F. Goodrich Aerospace Inc. and the University of 
     Akron. The computational lab contributed is expertise on gas 
     flows in physical vapor transport systems to a process 
     improvement study on carbon/carbon brakes, which are an 
     important export commodity of the U.S. Aerospace industry. In 
     another recently concluded collaboration, this time with 
     General Electric, the Lewis computational lab performed the 
     necessary modeling for the growth of single crystal sapphire 
     filaments. This work built on computational techniques 
     initiated during the 1980's and currently being extended 
     through MSAD sponsored research. The lab also serves as a 
     source of in-house modeling expertise for other NASA or 
     Government agencies which lack computational groups. From 
     1990 to 1993 the lab provided the training needed for 
     research on silicon carbide as a replacement material for 
     silicon in computer chips. Silicon carbide has higher 
     temperature tolerances than silicon and has potential 
     integrated circuit and sensor applications for use in 
     airplane and high performance auto engines.


                      vii. summary and conclusion

       Ten years of ground-based and in-space research in 
     biotechnology, combustion science, fluid physics and 
     materials science has allowed NASA's Microgravity Science 
     Research Program to work toward preserving U.S. preeminence 
     in critical aspects of space science, technology, and 
     applications.
       As a result of support and direction by the MSAD, a new 
     paradigm for scientific investigations has been fostered in 
     the microgravity science research community. It has been 
     recognized since the days of Skylab that many of the key 
     issues under investigation require an interdisciplinary 
     approach to research. The close and coordinated efforts of 
     investigators in materials science, fluid physics, chemistry, 
     control systems, and a broad spectrum of engineering 
     disciplines, bring to bear the rigor and expertise that is 
     necessary to successfully address these problems in a 
     meaningful way.
       With the efforts of the past decade as a firm foundation, 
     NASA's Microgravity Science and Applications Division will 
     continue to seek to use the microgravity environment of space 
     as a tool to advance knowledge; to use space as a laboratory 
     to explore the role of physical phenomena, contributing to 
     progress in science and technology on Earth; and to study the 
     role of gravity in technological processes, building a 
     scientific foundation for understanding the consequences of 
     gravitational environments beyond Earth's boundaries.\22\
       The authors would like to acknowledge the efforts of David 
     Vu in collecting reference material for this paper and also 
     give special thanks to Luisa Palting and Kristen Youngman for 
     their assistance in document preparation.


                               references

       1. The Program Task Report and Bibliography for the 
     Microgravity Science and Applications Division program (1987-
     1992) contains the full range of experiment descriptions and 
     published result citations.
       2. Prior to April 1993 this function was performed under 
     the auspices of NASA's Office of Space Science and 
     Applications.
       3. W. Liuki, and C. John, ``Protein Single Crystal Growth 
     Under Microgravity.'' Science, 225 (1984) 203.
       4. Rosenberg, F, and Meehan, E, ``Control of Nucleation and 
     Growth in Protein Crystal Growth.'' J. Cryst. Growth 90, 74 
     (1988).
       5. Delucas, L., Smith, et. al. ``Proteins Crystal Growth in 
     Microgravity,'' Science. vol. 246. Nov. 3, (1989). p. 651-
     654.
       6. Fichtl, G. Galloway, P., and Dowling, D. ``Overview of 
     U.S. Microgravity Science Instrumentation.'' AIAA. (1993).
       7. Goodwin, T., Jessup, J., Wolf, D. ``Morphological 
     Differentiation of Colon Carcinoma Cell Lines HT-29 and HT-
     29KM in Rotating-Wall Vessels.'' In Vitro Cell. Dev. Biol. 
     28A (Jan. 1992). p. 47-60.
       8. Goodwin, T., Prewell, D., Wolf, D., and Spaulding, G. 
     ``Reduced Shear Stress; A Major Component in the Ability of 
     Mammalian Tissues to Form Three-Dimensional Assemblies in 
     Simulated Microgravity.'' Journal of Cellular Biochemistry. 
     61:3. (1993). p. 301-311.
       9. Beardsley, T. ``Shear Bliss.'' ``Scientific American. 
     (February 1992), p. 27.
       10. Diamond, P. ``NASA Completes Tissue Model in a 
     Microgravity Bioreactor,'' Genetic Engineering News, (April 
     1991). p. 24-25.
       11. Duke, P., Daarie, E., and Montufar-Solis, D. ``Studies 
     of Chondrogenesis in Rotating Systems,'' Journal of Cellular 
     Biochemistry, 51:3. (1993). p. 274-282.
       12. Freed, L. Vunjak-Novakovic, and Langer, R. 
     ``Cultivation of Cell-Polymer Cartilage Implants in 
     Bioreactors,'' Journal of Cellular Biochemistry, 51. (1993). 
     p. 257-264.
       13. Becker, J., Prewett, T., Spaulding, G., and Goodwin, T. 
     ``Three Dimensional Growth and Differentiation of Ovarian 
     Tumor Cell Line in High Aspect Rotating Wall Vessel: 
     Morphologic and Embryologic Considerations.'' Journal of 
     Cellular Biochemistry, 51:3. (1993), p. 283-289,
       14. Naumann, R., ``Materials Processing in Space; Early 
     Experiments.'' U.S. NASA Government Printing Office, 
     Washington, D.C. (1980).
       15. Hazelrigg, G., and Reynolds, J. (Editors), and 
     Summerfield, M. (Series Editor). ``Opportunities for Academic 
     Research in a Low-Gravity Environment, Progress in 
     Astronautics and Aeronautics.'' Vol. 108, AIAA. (1986).
       16. ``NASA Microgravity Science and Applications Division: 
     A Program Overview'' 1986-87, Washington D.C. (1988).
       17. L. van den Berg, W.F. Schnepple, ``Growth of Mercuric 
     Iodide in Spacelab III,'' 19th International SAMPE Technical 
     Conference (1987).
       18. B. Steiner, R. Dobyn, H. Burdette, et al, ``High 
     Resolution Diffraction Imaging of Crystals Grown in 
     Microgravity and Closely Related Terrestrial Crystals Grown 
     in Microgravity and Closely Related Terrestrial Crystals.'' 
     NIST Technical Note 1287 (1991).
       19. Based on information supplied by Lewis Research Center.
       20. Naumann, R., ``Materials Processing in Space: Review of 
     the Early Experiments.'' Marshall Space Center, Preprint 
     Series: 84:113. (February 1984).
       21. Komotani, Y. and Ostrach, S., ``A Thermocapillary 
     Convection Experiment in Microgravity.'' HTD-Vol. 269, Heat 
     Transfer in Microgravity. ASME (1993).
       22. ``NASA Microgravity Science and Applicants Program: A 
     Strategic Plan for the 90's.'' Washington D.C. (June 
     1993).

                          ____________________