STS-75 Day 11 Highlights

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On Sunday, March 3, 1996, 6 a.m. CST, STS-75 Payload Status Report # 16 reports: (9/15:42 MET)

As "telescience," or remote controlled, operations for the third United States Microgravity Laboratory (USMP-3) continue, the crew has been actively conducting combustion experiments. While the four primary USMP-3 investigations depend on remote commanding from the ground, the three combustion investigations require, and benefit from, intensive crew involvement. To ensure safety, these are conducted in the enclosed Middeck Glovebox work area.

Combustion plays a key role in energy production, air pollution, transportation, propulsion, global environmental heating, materials processing and waste incineration. Two experiments -- the Radiative Ignition and Transition to Spread Investigation (RITSI) and the Forced-Flow Flamespreading Test (FFFT) -- study how fires behave in the low-gravity environment of space, so that they can be prevented and controlled. The third experiment -- Comparative Soot Diagnostics (CSD) -- is designed to determine how soot produced by flames in microgravity can be detected by on- board fire detectors. CSD may also help researchers better understand this major industrial byproduct.

Many space experiments require human interaction but contain irritating substances or potentially hazardous conditions. The Marshall-managed Middeck Glovebox provides a controlled and safe work environment for these operations. Project Scientist Dr. Donald Reiss, of NASA's Marshall Space Flight Center, says that scientists use the Glovebox to simulate experiments done in their ground-based laboratories but that their experiment samples behave quite differently than they do on Earth. The facility also provides power, light, data collection, air and particle filtration, and sensors for gas, temperature, air pressure and humidity. The microgravity environment of the Space Shuttle is itself an essential tool

RITSI principal investigator Dr. Takashi Kashiwagi, of the National Institute for Standards and Testing, got a boost in science return thanks to the help of Mission Specialist Maurizio Cheli. During the first RITSI run on Friday, Cheli was able to speed up a relatively long process and complete half of a second run ahead of schedule. This frees up a valuable time period for possible additional runs. Early results from RITSI dramatically illustrate that flames produced in space are quite different from those produced on Earth. "They were upside down, completely the reverse of flames one usually sees," Dr. Kashiwagi explained. On Earth, warm air rises, and cool air falls due to buoyancy-driven convection. In microgravity, the convective process is virtually eliminated.

The Forced Flow Flamespreading Test (FFFT) studies how air motion affects flame spreading to be able to better prevent or control fires. When a fire starts on Earth, flames spread due to the movement of air around and through the flames. Air motion also supplies oxygen to the fire, removes combustion products and controls how heat is released and the flame is distributed. Dr. Kurt Sacksteder and his investigator team from NASA's Lewis Research Center watched closely as flat paper and cellulose cylinder fuel samples were heated and ignited. The FFFT low-speed wind tunnel creates air movements of one to four inches per second, much slower than can be properly studied on Earth, where normal gravity causes air flows of at least ten inches per second.

As Pilot Scott Horowitz conducted an FFFT run, he adjusted the Glovebox's camera angle and focus to give the science team a better view of what he termed a "blue ball moving down the tube," referring to the cylindrical ashless paper sample he had lit up. Horowitz also reported seeing a "yellow flame inside the blue flame that is quite spectacular. I've never seen anything like this." Dr. Sacksteder said that the information his science team already has gathered will take months to fully analyze.

Dr. David Urban, also of the Lewis Center, is principal investigator for the Comparative Soot Diagnostics experiment. He worked through the Crew Interface Coordinator at Marshall who, in turn, sent up voice commands to Commander Andrew Allen to "tweak" various parameters such as fan speed and the ignition setting. Dr. Urban explained that "microgravity is quite different from the laboratory on Earth where we use models to guess the power it will take to ignite a material. In orbit, we realized that we could reduce the ignition power settings."

Over the next 24 hours, dedicated microgravity operations will continue with both MEPHISTO experiment teams, at the French Space Agency in Toulouse, France, and at the University of Alabama in Huntsville, Alabama, processing real-time data from their furnace's tin and bismuth alloy sample. The sample is again undergoing longer, slower melting and re-solidification cycles to take advantage of the best possible crystal growth conditions. Later today, the Advanced Automated Directional Solidification Furnace (AADSF) team will solidify their third lead-tin-telluride crystal. Meanwhile, the Critical Fluid Light Scattering Experiment continues cooling its xenon sample ever closer to its critical temperature. Also, tomorrow morning, the Isothermal Dendritic Growth Experiment (IDGE) team will shift its main remote control and data collection activities to the Rensselaer Polytechnic Institute, the first time that a campus site has ever sent remote commands to the Space Shuttle.

On Sunday, March 3, 1996, 8 a.m. CST, STS-75 MCC Status Report # 20 reports:

Flying 180 miles above the Earth, Columbia continues to provide a stable platform for the experiments comprising the United States Microgravity Payload mission with all orbiter systems performing well.

Science investigations continued through the night without interruption. Among the activities, crew members worked with an experiment called the Forced Flow Flamespreading Test which studies how flames react in the absence of gravity.

This morning, Commander Andy Allen had some time to relax while Pilot Scott Horowitz, Mission Specialist Maurizio Cheli, and Payload Specialist Umberto Guidoni talked with Voice of America about the progress of the flight so far. Later in the day, Horowitz, Cheli and Guidoni will have a break from their payload activities while Allen continues the scientific investigations.

The Blue Team will wake for its next shift at shortly after 3 p.m. Central. Columbia continues to orbit the Earth in smooth fashion at an altitude of 180 miles, completing one revolution of the Earth every 90 minutes.

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