STS-94 Mission Science Report # 10s
Monday, July 7, 1997, 7 p.m.CDT
The Microgravity Science Laboratory -1 crew aboard Columbia and science teams on the ground kept up a solid pace of experiment activities today.
Payload Specialist Dr. Greg Linteris, and Payload Commander Dr. Janice Voss each conducted a series of Droplet Combustion Apparatus experiments. Linteris also corrected a glitch with the droplet imaging camera that hung up during one of the experiment runs. Researchers report that the brief glitch had no scientific impact on the experiment.
Today’s droplet combustion experiments were part of the second of a three phase study to map burning characteristics over a range of atmospheric pressures. The first phase, completed earlier in the mission, was conducted at one atmospheric pressure, the same as on Earth. In the second phase experiments are being conducted at one-half the Earth’s atmospheric pressure. The third phase will use one-fourth Earth’s atmospheric pressure.
Characterizing the results from today’s experiments, scientist Dr. Forman Williams of the University of California in San Diego said: “The crew had a tougher time igniting the droplets at this lowered pressure -- we expected that But, when the fuel droplets did ignite, they burned stronger and more vigorously than we expected.”
During the experiment an n-heptane fuel droplet is burned in an atmosphere of helium and oxygen. The droplet is formed and deployed in the apparatus. Igniter wires are brought close to the sides of the droplet then retracted to create a free burning droplet.
Investigators are gathering information on burning rates of flames, flame structures and conditions under which flames are extinguished. Results of the investigation will provide researchers with a better understanding of the combustion process and may lead to cleaner, safer ways to burn fossil fuels as well as more efficient methods of generating heat and power on Earth.
Mid-morning, Mission Specialist Dr. Donald Thomas initiated another materials experiment in the Large Isothermal Furnace. The experiment, led by Dr. David Matthiesen of Case Western Reserve University in Cleveland, Ohio investigates the diffusion process in molten semiconductors.
This experiment will measure accurately the diffusion of dopants, deliberately added impurities, into germanium, which could lead to improved processing techniques for high quality metal alloys and products.
Later, Thomas conducted the Internal Flows in a Free Drop experiment in the Glovebox. He deployed free single liquid drops of water and water and glycerin of varying sizes and then positioned the spinning drops using sound waves or acoustic manipulation. Tracer particles inside the drops give scientists the ability to map the internal flows taking place as the drops are manipulated by sound waves.
“We had expected the rotation control to be easier with the second sample, the water-glycerin sample, but in reality it had a stronger torque, or twist, so the power had to be turned down,” explained the lead scientist Dr. Satwindar S. Sadhal of the University of Southern California in Los Angeles. Acoustic positioning is an important technique used in the containerless processing of materials. This investigation will allow researchers to assess the potential for a containerless, non-contact mixing method that could lead to improvements in chemical manufacturing, petroleum technology, cosmetics and food sciences.
This morning, Linteris performed an ethylene-fueled run of the soot experiment -- providing researchers with more information than they were hoping for.
“We were able to get information about the condition when the flame begins to emit soot,” explained lead scientist Dr. Gerard Faeth of the University of Michigan at Ann Arbor. “After the flame was adjusted, we got a flame configuration that did not emit nearly as much soot,” he continued. “We got two for one data; one flame provided information on two different soot emitting conditions -- something that is not possible on Earth.”
Payload Specialist Dr. Roger Crouch performed the next to last run of the soot experiment this afternoon which explored the effect of increased pressure on flames. “During our experiment runs, we’ve gotten interesting difference from anything we’ve observed on Earth; we’ve gotten fairly large flames that are easy to study and we’re certainly able to make observations onboard the shuttle that we couldn’t make on Earth,” said Faeth. The soot experiment will conclude about 9:30 p.m. after its final scheduled run; and the Combustion Module 1 will be readied for a series of flame ball experiments
An experiment which studies how glass forms in zirconium-based alloys completed a 14 hour processing period in the German levitating furnace, known as TEMPUS around, 4:00 p.m. The results of this study, led by Dr. Hans Fecht of the Technical University Berlin in Germany, could lead to improved techniques for processing metallic alloys and in turn better products.
Ahead, Voss and Crouch will continue conducting combustion experiments in the Spacelab. Crouch will conduct another series run of the Droplet Combustion Experiment and Voss will perform the final soot experiment before reading the Combustion Module -1 for the flame ball experiment. Shortly before midnight, Crouch is scheduled to change out a camera in the TEMPUS facility.
The next scheduled Public Affairs status report will be issued at approximately 6 a.m., July 8.
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