STS-94 MSFC
Science Report # 09s
Monday, July 7, 1997 7 a.m. CDT

  After short breaks in their busy schedules, crew members of the
Microgravity Science Laboratory mission are back to business, working
around the clock to fulfill the objective of their mission --
fundamental scientific research in space. Most of the last 24 hours
focused on combustion and materials science investigations in space.

  Aboard Columbia Sunday, crew members completed three runs of the
Laminar Soot Experiment -- a combustion investigation that could lead
to a more environmentally friendly fuel burning engine.  Using
ethylene gas, Payload Specialist Dr. Greg Linteris completed one run
in the morning, Payload Specialist Dr. Roger Crouch completed one in
the afternoon and Payload Commander Dr. Janice Voss completed one late
Sunday evening.

  Lead scientist Dr. Gerard Faeth of the University of Michigan at Ann
Arbor reported to the crew that the flames so far have been "super"
and that the science team is very pleased with experiment data it has
gathered. "We've learned that as we increase pressure, the amount of
soot in the flame and the amount of soot it emits increases,"
explained Faeth.  "It's probably one of the reasons that high pressure
combustion processes -- such as what goes on in a bus engine -- tend
to emit a lot of soot."

  Two samples of the experiment analyzing diffusion in liquid
Lead-tin-telluride were processed in the Large Isothermal Furnace over
the last 24 hours.  Linteris initiated the first sample shortly before
his shift ended at noon Sunday and Crouch initiated the experiment's
second run early Sunday evening. Early this morning, Mission
Specialist Dr. Donald Thomas initiated a third run, and it is
continuing to process in the facility.

  The study, led by Ms. Misako Uchida of Ishikawajima-Harima Heavy
Industries in Tokyo, Japan, is aimed at determining the diffusion
coefficient -- a fundamental quantity which describes the diffusion
process -- of liquid lead-tin-telluride. Diffusion is the process by
which liquid metals mix without stirring -- similar to how food
coloring disperses in a glass of water without stirring. Liquid
lead-tin-telluride is a potential material for use in manufacturing
infrared detectors and lasers. Uchida reported the completed runs were
"very good."

  On Sunday, science teams determined that the Large Isothermal
Furnace has been using more helium than expected. The furnace, a
vacuum-heating facility that is designed to uniformly heat large
samples, uses a helium purge to rapidly cool the samples.  The science
team is assessing the helium consumption rate, but estimates that it
is not likely the facility will run out of helium before testing is
completed.

  In the German levitating furnace, known as TEMPUS, a sample of a
glass-forming metallic liquid performed just as planned, according to
principal investigator Dr. William Johnson of the California Institute
of Technology in Pasadena. This experiment is measuring the
thermophysical properties -- heat capacity, thermal conductivity,
nucleation rates, surface tension, viscosity and thermal expansion --
of a complex alloy of titanium, zirconium, copper and nickel. "This is
the first time that some of these fundamental measurements have been
ever been taken," said Johnson.
 
  Early this morning, Thomas activated another experiment in the
TEMPUS facility which studies how glass forms in zirconium-based
alloys. Zirconium is an element found chiefly in ceramic and
refractory compounds. This study is led by Dr. Hans Fecht of the
Technical University Berlin in Germany. Results from TEMPUS
investigations could lead to improved techniques for processing
metallic alloys and in turn better products.

  Voss completed another series of runs of the Droplet Combustion
Experiment Sunday. That marked the beginning of the second of three
phases of the study to map the burning characteristics of heptane fuel
droplets over a range of atmospheric pressures. The first phase burned
the fuel droplets at one atmospheric pressure, the same as on
Earth. This phase is burning the droplets at one-half atmospheric
pressure. "In each phase, we are keeping the pressure the same and
slowly reducing the oxygen to see if the fuels can still burn and if
so, how they burn," said project scientist Dr. Vedha Nayagam of NASA's
Lewis Research Center in Cleveland, Ohio. "On Earth, we encounter low
combustion scenarios -- for instance, in gas turbines -- so it's
important to know what happens when pressure is reduced."

  In one atmospheric pressure the flame burned out, leaving a residue
of fuel. At the lower pressure, the flame is larger so the same
results were expected, but the flame collapsed back on the droplet,
completely consuming it. "It's surprising to see the droplet burn out
completely," said Nayagam. "This tells us something about the
extinction mechanisms."

  Linteris attempted to conduct another test this morning but the
droplet did not ignite. The science team is reviewing data to
understand why it didn't. Also, the Droplet Imaging Camera, which
records information about droplet size, is not working. The science
team is proceeding with experiment runs while it assesses the problem.

  Sunday, Crouch conducted an investigation that could result in an
improved understanding of the mechanisms leading to the unstable
operation and sometimes failure of specialized heat transfer devices
in space operations. In space, capillary-pumped loops are used to
transfer heat away from electrical devices to space radiators.  These
devices are not always reliable.  However, they are very attractive
because they require no power to operate, and are very economical in
terms of weight, an important consideration in satellite design.

  According to investigator Dr. Kevin Hallinan of the University of
Dayton in Dayton, Ohio, the experiment is providing researchers with a
better understanding of the mechanisms behind the unstable operation
and occasional failure of these devices. "The experiment has shown us
that the device is failing for reasons we didn't expect, which
provides new insight into potential failure mechanisms that may have
not been considered before. We're quite pleased with the results so
far."

  Sunday evening, Voss successfully rebooted an electronics unit of
the EXPRESS Rack -- powering it down then back up -- to restore the
facility's communication and telemetry capabilities. The EXPRESS Rack
is designed for quick and easy installation of hardware and
experiments on the International Space Station. Two experiments -- the
Physics of Hard Spheres Experiment and the ASTRO/Plant Generic
Bioprocessing Apparatus -- are being conducted in the EXPRESS Rack to
test its design, development and adaptation.

  The facility was experiencing problems relaying housekeeping
information -- temperature, air pressure and water flow -- to the
ground and receiving ground commands. The Physics of Hard Spheres
science team is now able to send up commands, but the ASTRO/Plant
Generic Bioprocessing Apparatus science team is still unable to
command from the ground and is continuing to troubleshoot the
problem. Crew members are able to command the experiment from the
Spacelab, so there is no impact to science. Restoring housekeeping
data functions would require rebooting the entire system which would
interrupt science, so the EXPRESS Rack team is relying on other,
indirect methods of gathering this information.

  Ahead, Linteris will complete the series of runs under way in the
Droplet Combustion Apparatus. Thomas will work in the Middeck Glovebox
to conduct a study of techniques used to control the position and
motion of free drops of liquid in low-gravity. Linteris will complete
another test of the soot experiment, and Thomas will begin the first
of six runs to study the diffusion process of tracers, or impurities,
in melted germanium, an element widely used as a semiconductor and
alloying agent.

The next scheduled Public Affairs status report will be issued at
approximately 6 p.m., July 7.