IML-2 Status Report #19 IML-2 Public Affairs Status Report #19 6:00 p.m. CDT, July 17, 1994 9/6:17 MET Spacelab Mission Operations Control Marshall Space Flight Center Today, IML-2 crew members assisted science teams with ground-commanded materials experiments, attempted to repair the Free Flow Electrophoresis Unit, and got a few well-deserved hours of rest. NASA Administrator Dan Goldin surprised the crew with a telephone call from Mission Control in Houston. He praised their hard work, saying it would help lay the groundwork for future space exploration. Payload Commander Rick Hieb volunteered two blocks of his free time today to perform maintenance procedures on the Japanese space agency's Free Flow Electrophoresis Unit. Assisted by Pilot Jim Halsell this morning, Hieb twice replaced all the distilled water in the unit's fluid cooling system to flush out air bubbles in the line. The unit reached its normal activation state and ran well for an hour and 20 minutes, then automatically shut off. Not willing to give up, Hieb tried the procedure for a third time just before his pre-sleep period. Thus far, the unit continues to operate within specifications. If this remains to be the case, the blue shift crew will prepare for a chromosome DNA separation experiment in the unit. Payload Specialist Chiaki Mukai worked closely with ground controllers to perform a run of Dr. Klaus Leonartz' solidification study in the NIZEMI slow- rotating centrifuge. A transparent, two-component material which mimics the behavior of metal alloys was melted, then slowly resolidified, as the centrifuge turned to simulate various levels of gravity. The NIZEMI microscope gave Mukai and experiment scientists a clear view of the point where the liquid was turning into a solid, called the solidification front. "Using the NIZEMI, we can observe fluid flows and detect the gravity levels at which they begin," explained Leonartz. "We can also determine the effect of the fluid flow on the solid. If we can learn how to make semiconductors or metals more homogenous, we can improve their properties. By determining gravity thresholds, we can learn how to use other methods, such as electromagnetic forces, to surpress fluid flows during processing on Earth." Another fluid-flow experiment was conducted in the Bubble, Drop and Particle Unit this morning. An experiment container holding three layers of immiscible (non-mixing) fluids was heated from the top and the bottom. Dr. Jean-Claude Legros of Brussels, Belgium, watched downlinked video as resulting tension differences where the fluids contacted one another began to create flows within the layers. The team will use the observations to verify numerical calculations they had made to predict the velocity and direction of the fluid flows in the middle layer. "The rough data we received from our remote support center in Belgium seems to match our predictions," said Legros. The calculations could help researchers develop methods for controlling fluid flows during the manufacture of sophisticated materials, such as silicon and metal alloys for the electronics industry. The current Bubble, Drop and Particle Unit experiment, which continues until late tonight, uses vapor bubbles in a liquid refrigerant to study the process of evaporation and condensation where the liquid and vapor form common surfaces. It should provide a better understanding of boiling processes and the behavior of fluids at a liquid-vapor interface. Principal investigator for the experiment is Dr. Johannes Straub of the Technical University of Munich, Germany. The TEMPUS electromagnetic containerless processing facility levitated, melted and solidified an aluminum-copper-cobalt alloy this morning. After the mission, investigators will study the preserved sample to determine its atomic arrangement. They will be looking for "quasicrystals," a recently discovered atomic structure that can give materials a high degree of hardness, as well as novel electrical and physical properties. The study aims for a better understanding of how and why quasicrystals form. The flight crew suspended orbiter thruster firings for a short period this afternoon, providing the most stable environment possible as the TEMPUS facility melted a sphere of pure zirconium. The strong, ductile metal was heated to more than 3,600 degrees Fahrenheit (2,000 degrees Celsius), several hundred degrees higher than any for any previous melt in space. The sample was levitated for about 10 seconds, then cooled down and solidified. The Japanese space agency's Large Isothermal Furnace processed two cartridges of tungsten-nickel-iron alloys for Dr. Randall German's liquid phase sintering experiment. The material was heated so the iron and nickel formed a liquid, surrounding the uniformly dispersed powered tungsten. The method is used extensively on Earth to combine dissimilar materials, but researchers suspect gravity plays a role in distorting the microstructure of such alloys. German, of Pennsylvania State University, will compare seven different compositions of the space-processed alloy, heated for different periods of time, with similar alloys processed on Earth. He will look for differences in shape, texture, density and high-temperature strength. Mission Specialists Don Thomas and Leroy Chiao will each get four hours off tonight. The assignments during work hours include NIZEMI, Biorack and TEMPUS experiments. NASA issues four status reports daily on STS-65/IML-2 activities: science operations reports from Spacelab Mission Operations Control in Huntsville at approximately 6 a.m. and 6 p.m., and orbiter operations reports from Mission Control in Houston at approximately 8 a.m. and 5 p.m.