07.10.97

Thursday, July 10, 1997 6 p.m. CDTSTATUS REPORT: STS-94-16s

STS-94 MISSION SCIENCE REPORT # 16S



The study of fire dominated the Microgravity Science Laboratory -1 
investigations in Columbia&rsquo;s Spacelab, today.



This morning Payload Specialist Dr. Greg Linteris completed a run in 
the second phase of the Droplet Combustion Experiment. The run is 
part of a three phase study to map the burning characteristics of 
heptane fuel droplets over a range of atmospheric pressures. The 
first phase --conducted earlier in the mission -- burned fuel 
droplets at one atmospheric pressure, the same as on Earth. The 
second phase burned the droplets at one-half atmospheric, while the 
third will burn droplets at one-quarter atmospheric pressure.



&ldquo;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,&rdquo; said project scientist Dr. Vedha Nayagam of 
NASA&rsquo;s Lewis Research Center in Cleveland, Ohio. &ldquo;On 
Earth, we encounter low combustion scenarios -- for instance, in gas 
turbines -- so it&rsquo;s important to know what happens when 
pressure is reduced.&rdquo;



&ldquo;We wanted to expand our data base at one-half atmospheric 
pressure,&rdquo; said co-investigator Dr. Fred Dryer of Princeton 
University in Princeton, New Jersey, &ldquo;so we combined two of our 
gas bottles that had been slated for one-quarter atmospheric pressure 
studies to yield a one-half atmospheric condition in the test 
chamber.&rdquo; The one-quarter atmospheric runs are scheduled for 
later in the mission.



Linteris burned three sizes of heptane droplets -- 4 mm, 3 mm and 2 
mm. The 4 mm droplet extinguished after burning 5.9 seconds--leaving 
behind a relatively large droplet. The smallest droplet burned about 
nine seconds -- using almost all of the fuel.



&ldquo;The large droplet extinguished early in its burn time due to 
loss of significant combustion energy by radiation,&rdquo; said 
Dryer. &ldquo;The small droplet burned to near completion because 
less energy is lost by radiation as the droplet&rsquo;s initial 
diameter is decreased. We would have received opposite results if 
we&rsquo;d conducted this same experiment on Earth.&rdquo;



Basic knowledge gained by the mapping of these various burning regimes 
will be used by scientists to design better combustion systems, such 
as combustors and propulsion systems, to extract maximum efficiency 
while minimizing unwanted pollutants.



After Linteris completed the series of runs to study burning fuel 
drops, both he and Mission Specialist Dr. Don Thomas took a planned 
half-day break.



Late this morning, a palladium-silicon sample completed an 11-hour 
processing period in the TEMPUS levitating furnace facility. The 
sample went from a solid state to a molten state and then was 
undercooled 16 times. The co- investigator, Bob Hyers of the 
Massachusetts Institute of Technology in Cambridge, Massachusetts, 
said this particular sample was chosen because it is a glass forming 
metal with many industrial applications.



&ldquo;Preliminary results look very promising,&rdquo; said Hyers. 
&ldquo;We got a wide range of temperatures and achieved a reasonable 
amount of undercooling.&rdquo;



A sample of palladium copper and silicon is now processing in the 
levitation furnace. Knowledge gained from this study, led by Dr. Ivan 
Egry of the German Aerospace Research Establishment in Cologne, may 
be used to improve materials processing techniques on Earth, and in 
turn, products manufactured from these processes.



Early this evening Payload Commander Dr. Janice Voss performed a run 
of the flame ball experiment using a 4 percent hydrogen in air fuel 
mixture. &ldquo;The rich fuel mixture matches the lean flammability 
limit of combustion on Earth,&rdquo; said project scientist Dr. Karen 
Weiland of NASA&rsquo;s Lewis Research Center in Cleveland, Ohio.



Voss&rsquo; sparking attempt resulted in eight flame balls. By 
studying flame balls, scientists hope to understand the physics of 
near-limit combustion, thereby leading to the design of 
leaner-burning fuels and improvements in engine efficiency - along 
with reduced emissions. The Structure of Flame Balls at Low 
Lewis-number experiment is led by Dr. Paul Ronney of the University 
of Southern California in Los Angeles.



This afternoon, Payload Specialist Dr. Roger Crouch performed the 
Bubble Drop and Non-linear Dynamics Experiment led by Dr. L.G. Leal 
of the University of California at Santa Barbara. During the 
experiment, Crouch deployed a bubble into the center of a 
water-filled container and then flattened it. On the ground the 
science team measured the bubble&rsquo;s movement as the shape of the 
bubble changed--revealing mechanical properties of the bubble under 
large forces or distortions. Later, Crouch will deploy two bubbles 
and try to create one bubble from the two--shedding light on bubble 
control and manipulation. Results of the bubble experiment could lead 
to techniques that eliminate or counteract the complications that 
bubbles cause during materials processing.



Processing of a germanium sample to study diffusion processes in 
molten semiconductors ended this morning when the control 
thermocouple, or temperature sensor on the sample, malfunctioned. The 
sensor inadvertently told the furnace to heat the sample beyond the 
high temperature limit which caused the Large Isothermal Furnace to 
shut itself off. The furnace is designed to monitor temperature and 
will shut off automatically if a sample reaches a certain 
temperature. The science team on the ground says the Large Isothermal 
Furnace is operating normally, and are assessing the control 
thermocouple which is part of this particular sample run. The orbiter 
crew initiated another scheduled sample run of the experiment at 5:15 
p.m. -- after the furnace had cooled down. This run is proceeding 
normally.



Ahead, Voss will conduct another run of the flame ball experiment and 
Crouch will continue the bubble experiment.



The next scheduled Public Affairs status report will be issued at 
approximately 6 a.m., July 11.

	
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