NP-119 Science in Orbit: The Shuttle & Spacelab Experience, 1981-1986

 

Chapter 3

Studying Materials and Processes in Microgravity: Materials Science

 


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aft view of the space shuttle cargo bay with the earth in the background.


 

[27] Materials science includes such diverse processes as converting sand to silicon crystals for use in semiconductors, producing high-strength, temperature-resistant alloys and ceramics, separating biological materials into valuable drugs and chemicals, and studying the basic phenomena that influence these processes. Materials processing is melting, molding, crystallizing, and combining or separating raw materials into useful products. The history of science and civilization goes hand in hand with advances in materials science and technology.

In some cases, progress in materials science on Earth has been limited: materials will not mix to form new alloys; crystals have defects that limit their performance; biological materials cannot be separated well enough to form some ultra-pure substances needed for medicine; crystals clump together instead of forming distinctly; glasses are contaminated by processing containers. Many of these problems are related to a constant force on Earth- gravity.

The presence of gravity has been counteracted in low-gravity aircraft flights and drop tubes, which offer about 30 seconds and 4 seconds of microgravity, respectively. Although the period of microgravity is brief, these test facilities are beneficial for research in preparation for spaceflight. The pull of gravity cannot be escaped at any altitude; at a 322 kilometer (200 mile) orbit, it is still 90 percent as strong as at the Earth's surface. However, its effects can be virtually cancelled by remaining in "free fall," that is, by remaining in orbit around the Earth as a satellite does. Spaceflight offers extended periods of low gravity; long duration is important for most solidification experiments, especially crystal growth. It is impossible to sustain a comparable microgravity environment on Earth.

NASA's microgravity science program uses spaceflight to eliminate or counteract gravity-induced problems that hamper materials scientists on the ground: buoyancy-driven convection in liquids, contamination from vessels that contain samples, and induced stresses that cause defects in crystals. Dramatic improvements in material properties have been achieved in recent microgravity experiments as our ability to control temperature has improved. Similar improvements can be expected in the future as our understanding of the effects of mass transport increases along with our ability to control convective flows.

Pioneering experiments from 1969 to 1975 aboard Apollo-era spacecraft and the Skylab space station led the way to microgravity science payloads developed for the Space Shuttle in the late 1970s. The Shuttle/Spacelab has proven useful for carrying many new automated and manually controlled facilities developed for materials science research.

Automated systems are appropriate for simpler experiments that need less crew involvement but still require the return of samples and equipment to the ground for analysis. The automated Materials Experiment Assembly (MEA) combined low-cost sounding rocket techniques with the extended microgravity duration of the Shuttle. This carrier supports three or four experiment modules in the payload bay.

 


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Crewmembers on board Spacelab can continuously monitor and adjust experiments.

Crewmembers on board Spacelab can continuously monitor and adjust experiments.

Crewmembers on board Spacelab can continuously monitor and adjust experiments.

 

For more sophisticated experiments requiring intense observation and crew control, facilities have been developed for the shirt-sleeve laboratory environment of the Spacelab module and for the Shuttle middeck. Spacelab offers scientists a place to do exploratory work such as attempting new processing techniques or testing basic theories. Scientists serve as crewmembers to observe and control experiments.

 

Thinking in Terms of Microgravity:

Because gravity is a dominating factor on Earth, it is difficult to think in terms of reduced gravity. Results from the early Shuttle/Spacelab missions prove that scientists are meeting this challenge as they develop techniques and attempt experiments that are affected by gravity in laboratories on the ground.

The first space product is now on the market: monodisperse latex spheres, precision microspheres that can be produced in space with improved uniformity. These spheres, which were produced in an apparatus in the Shuttle middeck during five missions, have been recognized as a calibration standard for microscopy.

Many of the experiments accomplished to date are not aimed at production but seek to discover more about the fundamental physics and....

 


Latex spheres processed in space.

Latex spheres processed on Earth.

.

.

Latex spheres processed in space.

Latex spheres processed on Earth.

 

[29] ...chemistry of materials processes on Earth. In microgravity, space scientists can use techniques to improve measurement accuracy and to try to observe phenomena that are not detectable on Earth. Analyses of samples produced in microgravity allow scientists to determine how gravity affects materials processing. For example, convection and sedimentation dominate the transport of heat and matter in many systems, but in space the effects of weaker forces such as surface tension are unveiled. Clarification of these phenomena may lead to better processing techniques on Earth and result in the discovery of materials with novel and commercially interesting properties.

The types of materials processed aboard the Shuttle/Spacelab include crystals and electronic materials, metal alloys and composites, glasses and ceramics, fluids and chemicals, and biological materials.

 


Many of the Shuttle/Spacelab experiments examine the fundamental physics influencing all materials processes.

Many of the Shuttle/Spacelab experiments examine the fundamental physics influencing all materials processes. A Spacelab 3 payload specialist did experiments on the basic behavior of liquid drops levitated in microgravity.

 

Crystals and Electronic Materials:

Crystals have achieved far greater value as electronic materials than they ever had as gems. Man has improved on nature's offerings but has been halted by bottlenecks that prevent some crystals from reaching their theoretical performance limits. Before crystal growth can be improved, scientists must determine what factors are responsible for crystal defects and learn how to control them.

Striking results were obtained with experiments on mercury iodide, a soft crystal valued for its potential as a nuclear radiation detector because it operates at room temperature without a bulky cooling system. Controlling the growth of a large mercury iodide crystal in microgravity was demonstrated with the Spacelab 3 Vapor Crystal Growth System. For the first time, crewmembers on the Shuttle and scientists on Earth monitored a crystal as it grew in microgravity. Images were relayed to the ground via television, and the crew viewed the crystal through a microscope imaging system. This allowed the growth of the crystal to be tracked through each stage, and scientists changed parameters such as temperature to adjust the growth and reduce defects, much as they do in ground-based laboratories.

A seed crystal mounted on a small, cooled finger (sting) at the base of the ampoule was a condensation point for material evaporated from a source at the top. The crystal grown in space for 100 hours was comparable to the best terrestrial crystals. The crystal quality, seen by reflecting X-rays, appeared to be better than the ground-based crystal used as a standard. Gamma ray tests showed the interior quality to be better than terrestrial mercury iodide crystals.

During the Spacelab 3 mission, more basic knowledge about crystal growth in microgravity w as obtained by growing triglycine sulfate (TGS) crystals in the Fluid Experiment System. Triglycine sulfate has potential as an infrared radiation detector at room temperature. This crystal has not met expected standards because, when grown to useful sizes, it develops defects which limit its performance.

For this experiment, TGS crystals were grown from solution with liquid TGS fluid solidifying on a seed crystal. The crystal and fluid are transparent, which makes it possible to record images of fluid motions. The growth chamber was in the center of a precision optical system which allowed photography by three techniques: shadowgraphy; schlieren, by which variations in fluid density make flow...

 


Scientists used video images of mercury iodide crystal to track its growth and adjust parameters, much as they do in ground-based laboratories.

Scientists used video images of mercury iodide crystal to track its growth and adjust parameters, much as they do in ground-based laboratories.

 

[30] ...patterns visible; and interference holography, using lasers to record density variations near the sample.

The TGS crystals shed light on how defects are formed and what role convection plays in creating defects, something that is not well understood. At the beginning of growth, a portion of the seed crystal is dissolved to form a smooth growth surface. In Earth-grown crystals, there is always a visible line where the seed crystal stops and the new growth begins; this introduces defects into the crystal. In the space-grown crystals, this line was not detected. This indicates that in the absence of convection the transition is smoother between the seed and the start of new growth.

A Spacelab 1 crystal growth experiment examined insoluble crystals (calcium and lead phosphates) that grow quickly to form plate-like crystals which are easily studied by X-ray techniques. Large crystals were grown, and the portions of the crystals grown in microgravity were free of defects. Defects were evident in portions of the crystals grown as the Shuttle landed, suggesting that defects are reduced in microgravity.

Another Spacelab 1 experiment studied processes linked to the distribution of dopants (trace elements) that give crystals desired electrical properties. For example, the conductivity of semiconductors is dramatically changed by adding dopants. However, nonuniform distribution of these dopants can interfere with the operation of electrical devices that use crystals. For most applications, the semiconductors produced on Earth are adequate, but for some highly specialized applications more uniformly doped, defect-free crystals are needed. Earlier experiments determined that convection that varies over time caused dopant striations in crystals.

The Mirror Heating Facility (Spacelab 1 ) modeled float-zone Earth-processing methods to determine whether the troublesome convective flows were produced by buoyancy or surface tension. Two experiments were done in an attempt to grow defect-free, single crystals of silicon. However, the space-grown crystals had the same marked dopant striations seen in Earth-grown crystals, confirming that Marangoni convection (flow driven by surface tension) may be a dominant cause of the defects on Earth and in space.

In ground-based experiments after Spacelab 1, the silicon seed crystal was coated with a thin oxide layer to prevent Marangoni flow as the crystal grew. The striations were eliminated, indicating that this is a successful technique for reducing the effects of Marangoni flow. For Spacelab D1, the experiment was repeated using this technique, and striation-free crystals also were grown in space.

 


Right [above]: Scientists used this black and white image showing density profiles in the fluid surrounding the triglycine sulfate crystal to generate a color computer map of fluid concentrations.

Right [above]: Scientists used this black and white image showing density profiles in the fluid surrounding the triglycine sulfate crystal to generate a color computer map of fluid concentrations.

 

Far Right [above]: The crystal was growing when this image was made; blue denotes the area near the crystal surface which has the least fluid concentration.

Far Right [above]: The crystal was growing when this image was made; blue denotes the area near the crystal surface which has the least fluid concentration.


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Mercury Iodide Crystal.

Mercury Iodide Crystal.

 

On the MEA-A1 mission, germanium selenide crystals were formed inside heated quartz ampoules. The size of the crystal and the location of crystal formation were far different than expected. On Earth, the crystals were small and formed a crust around the ampoule walls. In space, larger crystals nucleated in the middle of the ampoule away from the walls. The crystals were almost flawless, with strikingly improved surface qualities. The experiment was repeated on the MEAA2 mission (flown with Spacelab D1), and similar results were obtained. This indicates that the vapor-transport technique may be an excellent way to produce crystals in space.

 


Silicon crystals grown in the Mirror Heating Facility (Spacelab 1) had striations similar to crystals grown on Earth.

Silicon crystals grown in the Mirror Heating Facility (Spacelab 1) had striations similar to crystals grown on Earth. This led scientists to the conclusion that flows driven by surface tension, present in both 1-g and 0-g, rather than gravitational convection, caused the striations.


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A payload specialist inserts a sample into the Gradient Heating Facility.

A payload specialist inserts a sample into the Gradient Heating Facility.

 

This eutectic and copper processed in space (left) has a finer structure than the sample processed in the same facility on the ground (right).

This eutectic and copper processed in space (left) has a finer structure than the sample processed in the same facility on the ground (right).

 

 

Metals, Alloys, and Composites:

Scientists continue in their quest to improve metallurgical processes, to form better and novel alloys, and to test theories of metal and alloy processing. This type of processing is so complex that it is difficult to measure and model and even more difficult to control. In space, gravity-related phenomena such as convection are reduced, thus eliminating one complex mechanism for mass and heat transfer and simplifying processes for study.

Perhaps the most fundamental advances made in this area on the Shuttle were in understanding how liquified metals diffuse through each other. Diffusion is the movement of atoms past each other; each material has an inherent diffusion coefficient which describes the ability of atoms to move past each other in that material. Gravity-induced convection complicates diffusion measurements on Earth. Spacelab 1 results indicate that space may be the only place where accurate measurements of the coefficients can be made.

Spacelab 1 experiments showed that pure diffusion can be measured so well in space that thermomigration, also called Soret diffusion, is clearly evident. In a binary mixture in which a temperature gradient is maintained, thermomigration causes the constituents to separate according to their atomic weights. The heavier components will migrate toward the cool end of a furnace and the light components will migrate toward the hot end.

For one Spacelab experiment studying thermomigration, the Gradient Heating Facility, which had hot and cold ends to force a physical process to move in a given direction, provided a temperature drop of 648 degrees Fahrenheit from one end of the sample to the other. A sample of tin containing 0.5 percent cobalt was processed. Due to convective mixing, samples processed on the ground were evenly mixed; however, those processed in flight had double the cobalt concentration at the hot end of the ampoule. The accuracy of these measurements was 300 times better than ground-based experiments had achieved. This experiment may influence research to separate isotopes of metals with greater efficiency.

A similar experiment using common isotopes of tin measured its diffusion coefficient with an accuracy 10 to 40 times greater than the best ground-based experiments. Radiation analysis showed how much of the trace quantity of tin-124 had migrated into the tin-112 making up the bulk of the sample. Because isotopes are chemically identical, any movement of one into the other must be caused purely by diffusion instead of any chemical effect. Several tubes with different diameters were used to isolate variations caused by the walls. A striking [33] result was the high accuracy, unmatched in ground tests, of data indicating that the diffusion coefficient was much smaller than indicated by ground-based experiments. Accuracy in this figure will greatly improve the ability to model metal-mixing experiments both on the ground and in space, and the improved precision of diffusion measurements at different temperatures will help scientists establish the mechanism by which diffusion takes place in liquid metals.

A large number of alloys belong to an interesting class called eutectics. A eutectic material is a mixture of two materials that has a lower melting point than either material alone. In the liquid phase the two materials that form a eutectic are completely miscible, but in the solid phase they are almost completely immiscible. Therefore, as two materials that form a eutectic solidify, they go from a single liquid phase to two distinct solid phases. Because many alloys are eutectics, scientists are interested in understanding the distribution of the immiscible solid phases. If a eutectic alloy is directionally solidified, long rods or lamella (sheets of one phase sandwiched between another phase) are formed; the alloy may have desirable properties, such as added strength or higher magnetic performance in one direction.

As a result of space experiments, scientists are reexamining a classical theory on the formation of eutectics. The theory assumes there is no convection in the melt when the eutectic materials are processed in space. The theory works quite well on Earth, but an earlier rocket experiment produced a eutectic with rod spacing quite different than what was predicted by the classical theory. This was puzzling, but when the experiment was repeated in ground laboratories where a magnetic field was used to damp convection, experimenters got the same results. Scientists were faced with a paradox: a theory based on no convection worked fine when convection was present, but the theory did not work when convection was absent.

For the Spacelab 1 mission, the same experiment was repeated with other eutectic systems. Some of them had smaller rod spacing than predicted, others had the predicted rod spacing, and others even had larger rod spacing than predicted by the theory. Apparently, space experiments have revealed some unidentified effect that controls rod spacing in eutectic systems. More space samples will have to be processed to determine if the classical theory on convection in eutectic processing needs revision.

 

Glasses and Ceramics:

Optical engineering is being revolutionized by new glasses, crystals, and other materials that surpass conventional substances in quality. However, production of these superior materials is difficult, because some glasses have chemical mixes that are highly reactive with containers while others are extremely sensitive to contamination levels of even a few parts per billion. For example, certain fluoride glasses are of great interest for their infrared transmission properties. These glasses can be made on Earth, but trace contaminants from processing containers have prevented them from reaching their theoretical performance level.

Containerless processing, in which a sample is suspended and manipulated without touching contaminating containers, is an attractive solution to these problems. Containerless processing on massive samples can only be done in microgravity where the acoustic and electromagnetic forces used for suspension and manipulation are not overwhelmed by gravity. Currently, there is only a limited amount of data on how materials might be processed in this manner, but experiments such as the Spacelab 3 Drop Dynamics Module (DDM), which demonstrated that liquid drops could be levitated and manipulated acoustically in microgravity, will help scientists develop instruments and techniques for containerless processing of glasses and other materials. (The DDM results are discussed in the Fluid and Chemical Processes section of this chapter.)

For the first time, a glass sample was levitated, melted, and resolidified in space in the Single Axis Acoustic Levitator experiment carried aboard MEA-A2. This sample, a spherical glass shell containing an air bubble, was similar to fuel containers for inertially confined fusion experiments. These fusion experiments require that the glass shell have extremely smooth inner and outer surfaces and that the wall of the shell be perfectly uniform in thickness. The perfection in surface smoothness, wall thickness, sphericity, and concentricity required for large diameter glass shells that are inertially confined fusion targets is essentially impossible to maintain on Earth due to gravity-induced distortion; however, it might be possible to obtain this perfection by reprocessing the glass shell using containerless processing techniques in microgravity. When this experiment was conducted in space, [34] the sample melted and remained suspended. However, just before it resolidified, the air bubble inside migrated to the surface and broke through the outer wall, leaving a solid glass sphere. Bubble migration in the absence of gravitational convection is of great interest to materials scientists, and they are analyzing this experiment to determine why the bubble reacted in this unexpected fashion.

 


The Drop Dynamics Module provided the first opportunity to answer 300-year old questions about the behavior of drops. Drops such as this one were accoustically suspended and manipulated.

The Drop Dynamics Module provided the first opportunity to answer 300-year old questions about the behavior of drops. Drops such as this one were accoustically suspended and manipulated.

 

Two other samples were levitated and melted during the MEA-A1 and MEA-A2 missions, but when the samples were cooled, the levitation became unstable and the samples became attached to the sample confinement cage. More experiments are needed to study containerless processing of glass and other types of samples.

 

Fluid and Chemical Processes:

In microgravity, it is possible to observe fluid movement and behavior that are masked by gravity-driven flows on Earth. Fluid physics research may give scientists insight into crystal growth, glass processing, and other material processes.

The goal of the Spacelab 1 Fluid Physics Module experiment was to investigate fluid processes in microgravity. Two-inch-wide disks were used to support a column of liquid with free cylindrical surfaces. Because gravity does not collapse the liquid column in space, the disks were pulled apart to create a bridge almost 3 inches long (8 centimeters). (On Earth, 1/8th inch or 0.3 centimeters is the greatest possible height for columns of this fluid.) The disks were rotated together and in opposite directions and heated unevenly so that the behavior of the fluid under forces other than gravity could be observed.

One experiment used a fluid column to study Marangoni convection, which occurs when temperature gradients change the surface tension of a molten material, making the liquid surface move. By suspending tracers in the liquid bridge, scientists were able to observe fluid flows attributed to Marangoni convection in a fluid column that was almost 25 times bigger than any ever studied on Earth. Although detailed studies of Marangoni convection have been done on a small scale in terrestrial laboratories, it had never been studied in such a large sample. Scientists are analyzing films of this large fluid column to study detailed processes that occurred without the gravitational distortions that complicate measurements on Earth.

The Spacelab 3 Drop Dynamics Module provided the first opportunity to answer scientific questions that had been asked for more than 300 years. These fluid physics theories could not be studied experimentally because gravity precludes levitation of liquids without introducing forces that significantly mask the phenomena being studied. In microgravity, sound waves were used to levitate and manipulate drops of water and glycerin. As the principal investigator controlled the experiment, the drops were photographed.

The experiments confirmed that some of the age-old assumptions about drop behavior in relatively simple situations were correct. Other results were unexpected. The bifurcation point when a spinning drop takes a dog-bone shape in order to hold itself together came earlier than predicted under certain circumstances. In another case, a rotating dog-bone drop returned to a spherical shape and stopped rotating....

 


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Via video links between Spacelab and the ground, scientists on the ground were able to watch drop experiments.

Via video links between Spacelab and the ground, scientists on the ground were able to watch drop experiments.

 

These images made in space show patterns of fluid convection cells and wavy disturbances as observed in the Geophysical Fluid Flow Cell (GFCC).

These images made in space show patterns of fluid convection cells and wavy disturbances as observed in the Geophysical Fluid Flow Cell (GFCC). This experiment modeled basic fluid flows as well as those that might be found in planetary and stellar atmospheres. Gravity distorts similar studies made in ground-based laboratories.

 

....quickly rather than slowly, apparently from differential rotation on the inside. By analyzing the physical processes inside drops suspended in microgravity, scientists have the opportunity to experimentally test basic fluid physics theories that have applications in other areas of physics.

The drop experiments also demonstrated a potentially valuable processing technique. By suspending glasses and other materials inside a processing chamber so that the material does not touch container walls, scientists may be able to process purer specimens than those produced on Earth. The value of having an expert scientist to conduct space experiments was evident as well. The principal investigator was a part of the crew, enabling him to repair the instrument when it developed a problem on orbit, make valuable real-time observations, and adjust the experiment parameters to view subtle changes in drop behavior.

For another Spacelab 3 experiment, the Geophysical Fluid Flow Cell, a rotating spherical system was used to model patterns of convection and other interesting fluid motions that are found in stellar and planetary atmospheres. Fluid physicists are interested in the flow characteristics of the fluids themselves, and meteorologists, planetologists, and astrophysicists are interested in the large-scale circulation of fluids under the influence of rotation, gravity, and heating.

The thermally driven motion of a fluid in a spherical experiment is similar to that in a thermally driven rotating, shallow atmosphere or in a deep ocean on a spherical planet. It is very difficult to do controlled experiments with this type of system in an Earth-based laboratory, because terrestrial gravity distorts the flow patterns in ways that do not correspond to actual planetary flows. In space, gravity is reduced and electrostatic forces can be used to mimic gravity on a scale appropriate for the model. A 16-mm movie camera photographed global flow patterns as revealed by dyes and schlieren patterns resulting from fluid density changes.

 


Computer plots of fluid flows were made from the GFFC images.

Computer plots of fluid flows were made from the GFFC images. The yellow reveals upward flow and the blue represents downward flow.

 

More than 50,000 images were recorded in 103 hours of simulations. Some expected features such as longitudinal banana-shaped cells like those which may exist on the sun were observed. Other images are being compared to current models of atmospheric [36] flow patterns for planets such as Jupiter and Uranus. Space is the only place where these models can be tested accurately.

A Spacelab 2 experiment investigated the basic properties and behavior of a material that is not yet well understood but may be useful for new technology. Liquid helium is of interest as a coolant for infrared telescopes and detectors that operate at extremely low temperatures. Below 2.2 degrees Kelvin (-456 degrees Fahrenheit), liquid helium is transformed into superfluid helium, which moves freely through pores so small that they block normal liquid and conducts heat about 1,000 times better than copper. Because superfluid helium is an entirely different state of matter from conventional, fluids, it is being studied in space to improve our fundamental understanding of the physics of matter. Many subtleties of superfluid helium behavior are unknown because gravitational effects disturb the superfluid state, where the laws of quantum mechanics predominate over the laws of everyday existence.

Future space experiments are planned for which the temperature of the helium must be constant to a few millionths of a degree. Spacelab 2 experiments showed that the helium temperature does remain constant and stable. The large-scale motions of liquid helium also are important because they could disturb the attitude control systems essential for pointing telescopes of large helium-cooled observatories planned for the 1990s. A Spacelab 2 bulk fluid motion experiment measured the amplitude and decay of the sloshing motion caused by small orbiter motions. It appears the motions are so small that they will not affect the ultrasensitive telescopes and experiments.

 


The Continuous Flow Electrophoresis System is used to separate and purify biological cells and proteins.

The Continuous Flow Electrophoresis System is used to separate and purify biological cells and proteins.

 

Biological Processing:

Biological materials such as cells, proteins, and enzymes can be processed to create valuable medical and pharmaceutical products. Before many of these materials can be used for medical purposes, they must be separated from other substances. Convection and sedimentation on Earth make it difficult to separate these biological substances in ultra-pure forms and high concentrations.

The Continuous Flow Electrophoresis System (CFES) is used to separate and purify biological cells and proteins in space. This instrument has been flown six times, and after each flight the instrument and technique have been refined for more effective processing. Investigators have been able to increase the concentration of material separated and purified during a given period. For two proteins, the throughput of desired product was 500 times greater than achieved on the ground in the same instrument. The space-produced substances are being evaluated by a pharmaceutical company.

Materials and life scientists also share an interest in protein crystals. Single crystals of sufficient size and perfection are needed to analyze the molecular structure of numerous proteins and enzymes. Knowledge of the structure is a prerequisite for optimal utilization of the proteins for medical, pharmaceutical, and bioengineering applications.

These crystals can be grown by the simultaneous counter-diffusion of a protein and salt solution into a buffer solution. As the proteins start to crystallize on Earth, the different densities of the crystal and the solution result in convection, which can lead to a large number of small, imperfect crystals. Thus, one of the great limitations in protein crystal, research has been the inability to produce large, pure crystals for analysis.

[37] Fortunately, preliminary experiments aboard the Shuttle and Spacelab indicate that much larger and higher quality crystals can perhaps be grown in space where convection is reduced and crystals float freely in solution. During the Spacelab 1 mission, crystals of Iysozyme (a basic protein) and betagalactosidase (a key genetic ingredient) were produced of sufficient size and perfection for X-ray structural analysis. The crystals were several times larger than those produced in the same facility on the ground.

The successful Spacelab 1 experiment sparked a united effort by a team of scientists who developed an apparatus that uses vapor diffusion to grow protein crystals. Several proteins have been processed in this developmental apparatus; many of the space crystals were large, and indications are that the quality is high. The crystals also formed more distinctly, rather than clumping together. In the case of one protein, a new crystal form was identified and has since been produced in ground laboratories. Based on these preliminary results, a larger facility with a more controlled environment is being developed.

 


These lysozyme crystals processed during Spacelab 1 were several times larger than those produced in the same facility on the ground.

These lysozyme crystals processed during Spacelab 1 were several times larger than those produced in the same facility on the ground.


It is possible to define the structure of single protein crystals using X-ray crystallography, but the ability to do this depends on the size and perfection of the crystal. These space-processed canavalin crystals indicate the potential of growing high quality protein crystals in space.

It is possible to define the structure of single protein crystals using X-ray crystallography, but the ability to do this depends on the size and perfection of the crystal. These space-processed canavalin crystals indicate the potential of growing high quality protein crystals in space.


Computer-generated model of a protein structure.

Computer-generated model of a protein structure.

 

[38] Gaining Experience to Shape the Future:

These first-generation space experiments have proven the feasibility of a variety of materials processing techniques in space. These experiments have provided some valuable fundamental knowledge, revealing the nature of phenomena that are masked or not easily observed on Earth. A second generation of experiments with more clearly defined objectives and better instrumentation is needed to quantify results.

Spacelab has proven that crewmembers acting as operators and observers will be extremely important for experimentation, because unanticipated results can only be spotted by the trained eye, and a simple adjustment may rescue or change the nature of an experiment. On the Space Station, with crewmembers to observe experiments and equipment for analyzing samples in orbit, it will not be necessary to return all specimens to Earth for characterization before running the next experiment in space. Productivity will be enhanced by the additional power and space for experiments on the Space Station The Space Station will use sophisticated data systems to display real-time data to investigators in space and on the ground. This will make collaboration between scientists more practical. Data will be archived so that each experiment can build on results from previous studies.

The Space Station will permit long duration experiments in an environment more similar to terrestrial laboratories. A dramatic increase in experiment time over the few tens of hours performed to date will occur. Experiments in microgravity will stretch over periods comparable to those on Earth, greatly increasing the types of materials that can be processed to full term. This will be a great advantage to experiments in areas such as solution and vapor crystal growth which require 15 to 30 days of con sinuous growth to produce crystals of the desired size.

It may be that experiments that do not need a pressurized module or frequent human intervention can be attached outside on the station or flown on free flyers. Free flyers will have a more stable microgravity environment that is not disturbed by crew motions and other Space Station activities. They will be ideal for mature manufacturing facilities where processing is routine and products only need retrieval. Teleoperated or remote vehicles may be used to retrieve and replace samples.

The Shuttle/Spacelab has helped train both investigators and crewmembers for future materials processing experiments. Scientist crewmembers and investigators on the ground have learned to work together, observing and adjusting parameters to improve experiment results.

The upcoming International Microgravity Laboratory (IML) missions will give scientists around the world an opportunity to coordinate research. Some experiments from previous missions, such as the Spacelab 3 crystal growth experiments, will be reflown and some new experiments will be attempted. This mission will provide valuable research opportunities to U.S. scientists and to their international partners who will work with them aboard the Space Station. Aboard the Spacelab J mission, the Japanese will do their first manned materials processing experiments in space.

NASA continues to examine ways to improve Shuttle/Spacelab research. In the future it may be possible to extend missions, providing longer periods for research. This will allow a larger experiment base to be developed and contribute to the evolution of more mature hardware to take advantage of long-term stays aboard the Space Station.

 


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The Space Station will give scientists around the world an opportunity to coordinate research in materials and life sciences.

The Space Station will give scientists around the world an opportunity to coordinate research in materials and life sciences.

 

[40] Materials Science Investigations

OSS-1/STS-3

Monodisperse Latex Reactor System
J. W. Vanderhoff, Lehigh University
Bethlehem, Pennsylvania

 

STS-6

Continuous Flow Electrophoresis System.
D. Clifford, McDonnell Douglas Aerospace
St. Louis, Missouri

 

Materials Experiment Assembly-A1 (MEA A1)/STS-7

Gradient General Purpose Rocket Furnace
Vapor Growth of Alloy-Type Semiconductor Crystals
H. Wiedemeier, Rensselaer Polytechnic Institute
Troy, New York
 
Isothermal General Purpose Rocket Furnace
Liquid Phase Miscibility Gap Materials
S. H. Gelles, S. H. Gelles Laboratories, Inc.
Columbus, Ohio
 
Single Axis Acoustic Levitator
Containerless Processing of Glass Melts
D.E. Day, University of Missouri
Rolla, Missouri

 

Materialwissenschaffliche Autonome Experimente Unter Schwerelosigleit (MAUS)/STS-7

Solidification Front
H. Klein, DFVLR
Cologne, Germany
 
Stability of Metallic Dispersions
G.H. Otto, DFVLR
Cologne, Germany

 

Spacelab 1/STS-9

Materials Science Double Rack-

 

Fluid Physics Module

Capillary Forces in a Low-Gravity Environment,
J.F. Padday, Kodak Research Laboratory
Harrow, England
 
Coupled Motion of Liquid-Solid Systems in Near-Zero Gravity
J. P. B. Vreeburg, National Aerospace Laboratory
Amsterdam, The Netherlands
 
Floating Zone Stability in Zero-Gravity
1. Da Riva, University of Madrid, Spain
 
Free Convection in Low Gravity
L.G. Napolitano, University of Naples, Italy
 
Interfacial Instability and Capillary Hysteresis
J.M. Haynes, University of Bristol, United Kingdom
 
Kinetics of the Spreading of Liquids in Solids
J.M. Haynes, University of Bristol, United Kingdom
 
Oscillation of Semi-Free Liquid Spheres in Space
H. Rodot, National Center for Scientific Research
Paris, France

 

Gradient Heating Facility

Lead-Telluride Crystal Growth
H. Rodot, National Center for Scientific Research
Paris, France
 
Solidification of Aluminum-Zinc Vapor Emulsion
C. Potard, Center for Nuclear Studies
Grenoble, France
 
Solidification of Eutectic Alloys
J.J. Favierand J.P. Praizey
Center for Nuclear Studies
Grenoble, France
 
Thermodiffusion in Tin Alloys
Y. Malmejac and J.P. Praizey
Center for Nuclear Studies
Grenoble, France
 
Unidirectional Solidification of Eutectics
G. Muller, University of Erlangen, Germany

 

Isothermal Heating Facility

Bubble-Reinforced Materials
P. Gondi, University of Bologna, Italy
 
Dendrite Growth and Microsegregation of Binary Alloys
H. Fredriksson, The Royal Institute of Technology
Stockholm, Sweden
 
Emulsions and Dispersion Alloys
H. Ahlborn, University of Hamburg, Germany
 
Interaction Between an Advancing Solidification Front and Suspended Particles
D. Neuschutz and J. Potschke
Krupp Research Center
Essen, Germany
 
Melting and Solidification of Metallic Composites
A. Deruyttere, University of Leuven, Belgium
 
Metallic Emulsion Aluminum-Lead
P.D. Caton, Fulmer Research Institute
Stoke Poges, United Kingdom
 
Nucleation of Eutectic Alloys
Y. Malmejac, Center for Nuclear Studies
Grenoble, France
 
Reaction Kinetics in Glass
G.H. Frischat, Technical University of Clausthal, Germany
 
Skin Technology
H. Sprenger, MAN Advanced Technology
Munich, Germany
 
[41] Solidification of Immiscible Alloys
H. Ahlborn, University of Hamburg, Germany
 
Solidification of Near-Monotectic Zinc-Lead Alloys
H. F. Fischmeister, Max Planck Institute
Stuttgart, Germany
 
Unidirectional Solidification of Cast Iron
T. Luyendilk, Delft University of Technology
The Netherlands
 
Vacuum Brazing
W. Schonherr and E. Siegfried
Federal Institution for Material Testing
Berlin, Germany
 
Vacuum Brazing
R. Stickler and K. Frieler
University of Vienna, Austria

 

Mirror Heating Facility

Crystallization of a Silicon Drop
H. Kolker, Wacker-Chemie
Munich, Germany
 
Floating Zone Growth of Silicon
R. Nitsche and E. Eyer
University of Freiburg, Germany
 
Growth of Cadmium Telluride by the Traveling Heater Method
R. Nitsche, R. Dian, and R. Schonhok
University of Freiburg, Germany
 
Growth of Semiconductor Crystals by the Traveling Heater Method
K. W. Benz, Stuttgart University, and
G. Muller, University of Erlangen, Germany

 

Special Equipment

Adhesion of Metals in UHV Chamber
G. Ghersini
Information Center of Experimental Studies, Italy
 
Crystal Growth by Co-Precipitation in Liquid Phase
A. Authier, F. Le Faucheux, and M.C. Robert
University of Pierre and Marie Curie, Paris, France
 
Crystal Growth of Proteins
W. Littke, University of Freiberg, Germany
 
Mercury iodide Crystal Growth
R. Cadoret, Laboratory for Crystallography and Physics
Les Cezeaux, France
 
Organic Crystal Growth
K.F. Nielsen, G. Galster, and 1. Johannson
Technical University of Denmark
Lyngbyg, Denmark
 
Selfdiffusion and Interdiffusion in Liquid Metals
K. Kraatz, Technical University of Berlin, Germany

 

Spacelab 3/51-B

Crystal Growth Facility

Mercury iodide Crystal Growth*
R. Cadoret and P. Brisson
Laboratory for Crystallography and Physics
Les Cezeaux, France

 

Drop Dynamics Module

Dynamics of Rotating and Oscillating Free Drops
T. Wang, NASA Jet Propulsion Laboratory
Pasadena, California

 

Fluid Experiment System

Solution Growth of Crystals in Zero Gravity System
R. Lal, Alabama A&M University
Huntsville, Alabama

 

Geophysical Fluid Flow Cell

Geophysical Fluid Flow Cell Experiment
J.E. Hart, University of Colorado
Boulder, Colorado

 

Vapor Crystal Growth System

Mercuric iodide Growth
W.F. Schnepple, KG&G, Inc.,
Goleta, California

 

Spacelab 2/51-F

Properties of Superfluid Helium in Zero-Gravity
P. V. Mason, NASA Jet Propulsion Laboratory
Pasadena, California
 
Protein Crystal Growth****
C. E. Bugg, University of Alabama in Birmingham, Alabama

 

Spacelab D1/61-A

Materials Science Double Rack-

 

Cryostat

Protein Crystals*
W. Littke, University of Freiburg, Germany

 

Fluid Physics Module

Capillary Experiments*
J.F. Padday, Kodak Research Laboratory
Harrow, United Kingdom
 
Convection in Nonisothermal Binary Mixture
J.C. Legros, University of Brussels, Belgium
 
Floating-Zone Hydrodynamics*
I. Da Riva, University of Madrid, Spain
 
Forced Liquid Motions*
J. P. B. Vreeburg, National Aerospace Laboratory, Amsterdam, The Netherlands
 
[42] Marangoni Convection
A.A.H. Drinkenburg, University of Groningen, The Netherlands
 
Marangoni Flows *
L.G. Napolitano, University of Naples, Italy
 
Separation of Fluid Pha.
R. Naehle, DFVLR
Cologne, Germany

 

Gradient Heating Facility

Cellular Morphology in Lead-Thallium Alloy
B. Billia, University of Marseille, France
 
Dendritic Solidification of Aluminum-Copper Alloys
D. Camel, Center for Nuclear Studies
Grenoble, France
 
Doped Indium Antimonide and Gallium Indium Antimonide
C. Potard, Center for Nuclear Studies
Grenoble, France
 
Ge-Gel4 Chemical Growth
J.C. Launay, University of Bordeaux, France
 
Ge-I2 Vapor Phase
J.C. Launay, University of Bordeaux, France
 
Thermal Diffusion
J. Dupuy, University of Lyon, France
 
Thermomigrabon of Cobalt in Tin
J. P. Praizey, Center for Nuclear Studies
Grenoble, France

 

High Temperature Thermostat

Self- and Interdiffusion*
K. Kraatz, Technical University of Berlin, Germany

 

Isothermal Heating Facility

Homogeneity of Glasses*
G.H. Frischat, Technical University of Clausthal, Germany
 
Liquid Skin Casting of Cast Iron *
H. Sprenger, MAN Advanced Technology
Munich, Germany, and
l.H. Nieswagg, Delft University of Technology
The Netherlands
 
Nucleation of Eutectic Alloys*
Y Malmejac, Center for Nuclear Studies
Grenoble, France
 
Ostwald Ripening*
H.F Fischmeister, Max Planck Institut
Stuttgart, Germany
 
Particle Behavior at Solidification Fronts
D. Langbein, Battelle-lnstitute
Frankfurt, Germany
 
Separation of Immiscible Alloys *
H. Ahlborn, University of Hamburg, Germany
Skin Technology*
H. Sprenger, MAN Advanced Technology
Munich, Germany, and
l.H. Nieswaag, Delft University of Technology
The Netherlands
 
Solidification of Composite Materials*
A. Deruyttere, University of Leuven, Belgium
 
Solidification of Suspensions*
J. Potschke, Krupp Research Center
Essen, Germany

 

Mirror Heating Facility

Floating Zone Growth of Silicon*
R. Nitsche, University of Freiburg, Germany
 
Growth of Cadmium Telluride by the Traveling Heater Method*
R. Nitsche, University of Freiburg, Germany
 
Growth of Semiconductor Crystals by the
Traveling Heater Method*
K. W. Benz, University of Stuttgart, Germany
 
Melting of Silicon Sphere*
H. Kolker, Wacker- Chemie
Munich, Germany

 

Materials Science Experiment Double Rack for Experiment Modules and Apparatus-

Gradient Furnace with Quenching Device

Aluminum/Copper Phase Boundary Diffusion
H.M. Tensi, Technical University, Munich, Germany
 
Solidification Dynamics
S. Rex and P R. Sahm, RWTH
Aachen, Germany

 

High-Precision Thermostat

Heat Capacity Near Critical Point
J. Straub, Technical University Munich, Germany

 

Monoellipsoid Heating Facility

Indium Antimonide-Nickel Antimonide Eutectics
G. Muller, University of Erlangen, Germany
 
Traveling Heater Method (PbSnTe)
M. Harr, Battelle-lnstitute, Frankfurt, Germany
 
Vapor Growth of Cadmium Telluride
R. Nitsche, University of Freiburg, Germany

 

[43] Process Chamber-

Holographic Interferometric Apparatus

Bubble Transport
A. Bewersdorff, DFVLR
Cologne, Germany
 
GETS
A. Ecker and P R. Sahm, RWTH
Aachen, Germany
 
Phase Separation Near Critical Point
H. Klein, DFVLR
Cologne, Germany
 
Surface-Tension Studies
D. Neuhaus, DFVLR
Cologne, Germany

 

Interdiffusion Salt Melt Apparatus

Interdiffusion
J. Richter, RWTH
Aachen, Germany

 

Marangoni Convection Boat Apparatus

Marangoni Convection
D. Schwabe, University of Giessen, Germany

 

Materials Experiment Assembly-A2 (MEA-A2)/61-A*****

 

Gradient General Purpose Rocket Furnace

Semiconductor Materials
R.K. Crouch, NASA Langley Research Center
Hampton, Virginia
 
Vapor Growth of Alloy-Type Semiconductor Crystals
H. Wiedemeier, Rensselaer Polytechnic Institute
Troy, New York

 

Isothermal General Purpose Rocket Furnace

Diffusion of Liquid Zinc and Lead
R.B. Pond, Marvalaud, Inc.
Westminster, Maryland
 
Liquid Phase Miscibility Gap Materials
S. H. Gelles, S. H. Gelles Laboratories, Inc.
Columbus, Ohio

 

Single Axis Acoustic Levitator

Containerless Melting of Glass*
D.E. Day, University of Missouri
Rolla, Missouri

 

Materials Science Laboratory-2 {MSL-2)/61-C*****

Automated Directional Solidification Furnace

Orbital Processing of Aligned Magnetic Composites
D.J. Larson, Grumman Aerospace Corporation
Bethpage, New York

 

Electromagnetic Levitation Furnace

Undercooled Solidification in Quiescent Levitated Drops
M.C. Fleming, Massachusetts Institute of Technology
Cambridge, Massachusetts

 

Three-Axis Acoustic Levitator

Dynamics of Compound Drops
T. Wang, NASA Jet Propulsion Laboratory
Pasadena, California

 

Physical Phenomena in Containerless Glass

Processing Model Fluids
R. S. Subramanian, Clarkson University
Potsdam, New York
 
 

* Reflight
** 5 flights completed (STS-3, -4, -6, -7, and -11)
*** 6 flights completed (STS-6, -7, -8, 41-D, 51-D, and 61-B)
**** 4 flights completed (Spacelab 2, 51-D, 61-B, and 61-C)
***** MEA-A2 is sometimes referred to as MSL- 1; The MSL-2 mission was the first MSL flight


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