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Press Release 94-16
 
 
Immediate
Mary Ann Peto
(Bus: 216/433-2902)

NASA Lewis Research Center Microgravity Experiements Prime Customer of STS-62 Shuttle Mission

Cleveland, OH -- When the space shuttle Columbia (STS- 62) is launched in March 1994, the Lewis Research Center will be its prime customer.

For STS-62, Lewis is providing and managing:
  • three of the four major microgravity science experiments;
  • two of the six in-space technology experiments;
  • samples for the Limited Duration Candidate Exposure Experiment; and
  • three acceleration measuring devices to characterize the microgravity environment during flight.
Nestled in Columbia's payload bay are Lewis' microgravity experiments in which the Principal Investigators are seeking a better understanding of materials science and fluid physics in a reduced gravity environment. With a greater understanding of what happens when metals, alloys and electronic materials are melted and then solidified in a reduced gravity environment, the future of manufacturing technology could be enhanced and is therefore of interest to metal and electronic component producing companies.

Also part of the Columbia manifest are the technology experiments which are seeking validation of design concepts and processes for improved electrical power systems for the next generation of spacecraft and satellites.

Prior to being flown in space for long term exposure, extensive ground-based research must be conducted to define and support the microgravity science endeavors. At Lewis, low-gravity ground-based facilities such as drop towers and a Learjet aircraft which flies parabolic trajectories, are often used to provide limited low-gravity experiment time.

During the STS-62 mission, the experiments will operate primarily by remote control from either the Marshall Space Flight Center in Alabama, the Goddard Space Flight Center in Maryland, or from the new User Operations Facility at the Lewis Research Center.

Lewis' payloads flying aboard STS-62 are:
Isothermal Dendritic Growth Experiment (IDGE)--its primary objective is to test fundamental assumptions concerning dendritic solidification of molten materials. Dendrites are tiny branching structures that form inside molten metal alloys when they solidify during manufacturing. The size, shape and orientation of the dendrites have a major effect on the strength, ductility and usefulness of an alloy.


Using a dendrite model, manufactured by Scale Models of Hiram, Ohio, STS-62 crew members will demonstrate via a shuttle downlink the importance of flying the IDGE package.


Critical Fluid Light Scattering Experiment, dubbed "Zeno" by the principal investigator in honor of the Greek philosopher who first pondered the paradox of infinity, will analyze the behavior of xenon under microgravity conditions near its critical point. A fluid's critical point occurs at the highest temperature where liquid and vapor phases can co-exist. Using laser light scattering, experimenters can measure fluctuations in the density of the xenon sample near its critical point a hundred times closer to its critical point than is possible on Earth. Because critical point phenomena are common to many different materials, researching behavioral characteristics of matter near the critical point can shed light on a variety of fundamental physics problems.

Both the IDGE and Zeno experiments are considered to be "world-class science."

Of importance to the semiconductor industry, which supplies the solid-state components, such as integrated circuits, for the manufacture of electronic equipment, is the Bismuth-Tin Crystal Growth Experiment also known as the In-Situ Monitoring of Crystal Growth Using MEPHISTO Experiment. This experiment is one part of a multi-mission collaborative U.S. and French investigation of the fundamentals of crystal growth. In this experiment, rods of pure bismuth and bismuth with very small additions of tin are inserted in a furnace and will be heated and then cooled to study the formation of flat faced crystals.

This experiment will yield a large amount of information concerning growth rate, interface shape and interface supercooling. Such information will be used to understand the relationship between the generation of imperfections and the redistribution of the chemical elements in the crystal. Both of these things affect the quality of crystals and the performance of electronic devices that use them.

The Space Acceleration Measurement System (SAMS) measures the very slight acceleration forces on the shuttle orbiter as it drifts in space. These forces are typically only one one-thousandth of the gravitational force on Earth. SAMS will measure, record and downlink disturbances caused by crew activity, equipment operation and thruster firings. By measuring and analyzing microgravity disturbances, scientists hope to determine how these disturbances influence experiment results. Working in conjunction with SAMS, is the Orbiter Acceleration Research Experiment (OARE) which will record small accelerations caused by atmospheric drag on the orbiter, residual gravity gradient forces and other frequency disturbances. This will be the ninth flight of the SAMS hardware.

The Solar Array Module Plasma Interactions Experiment (SAMPIE) was designed by Lewis engineers and scientists to gather key environmental interaction data to support the design and construction of high-voltage photovoltaic space power systems for operation in low Earth orbit. Specifically it will investigate and quantify the potentially damaging interactions between the space plasma (gases) found in low Earth orbit and the solar array surfaces. Over the years Lewis has conducted ground-based plasma tests to simulate low-Earth orbit conditions. However, testing has shown that arc rates in space were quite different and generally higher than in ground tests, therefore, necessitating suitable in-space testing.

The Thermal Energy Storage (TES) Experiment is designed to provide data for understanding the microgravity behavior of salts as they expand and contract during melting and freezing. Information obtained from the TES experiment has direct application to using on-orbit solar dynamic power systems which will store solar energy by melting a thermal energy salt such as lithium fluoride. This stored heat is later drawn out of the salt to drive a turbine engine and generator. Such systems are helping to establish a solar dynamic power system for use in Earth orbiting spacecraft such as the international Space Station.

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