STS-73 Day 11 Highlights
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- On Monday, October 30, 1995, 8 a.m. CST, STS-73 MCC Status Report # 20
- On its eleventh day on orbit, the Space Shuttle Columbia continues to
provide the United States Microgravity Laboratory-2 with a stable
platform above the Earth for the astronauts to conduct a myriad of
- Flying at an altitude of 170 miles, Columbia is positioned with its
tail pointing toward the Earth and its port wing pointing in the
general direction of travel. This "gravity gradient" attitude
is maintained with only minimal thruster firings. The orbiter will
stay in this position until around midnight tonight when Columbia will
begin a 14-hour thermal conditioning period with its belly pointed
toward the sun.
- On Monday, October 30, 1995, 6 a.m. CST, STS-73 Payload Status Report # 16
reports: (9/21:07 MET)
- Drop physics studies and Glovebox investigations dominated crew
activities during the tenth day in orbit for the United States
Microgravity Laboratory-2, while the mission's many remotely
controlled experiments collected valuable data as well.
- Geophysical Fluid Flow Cell (GFFC) experiment runs yesterday seem to
validate predictions in a mathematical model of planetary and solar
fluid flows designed by Co-Investigator Dr. Tim Miller. GFFC
scientists saw different heat-driven, or thermocapillary, flow
patterns when the same conditions were initiated at different rates.
For instance, voltage, temperature and rotation speed parameters
applied slowly to the experiment's silicone-oil-filled hemispheres
produced one thermocapillary fluid flow, and a different flow resulted
when the same parameters were applied to the experiment quickly.
- "These particular flows are relevant to cases where you might have a
planet with a core that's still moving around -- still convecting --
and also planets with atmospheres that are rotating very slowly," said
Miller. The experiment facility, which simulates fluid flows in
oceans, planets and stars, is operated from the ground with only
occasional adjustments and monitoring by the crew. Research in
thermocapillary flow phenomena could one day aid in forecasting ocean
flows and weather patterns.
- The Crystal Growth Furnace finished melting its second gallium
arsenide semiconductor sample yesterday afternoon, then began slowly
moving the furnace module down the length of the sample cartridge to
solidify the crystal. Early this morning, the experiment team changed
the furnace translation rate from seven one hundredths of an inch (1.8
millimeters) per hour to seven tenths of an inch (18 millimeters) per
hour. This ten-fold increase will help Principal Investigator
Dr. David Matthiesen determine whether the solidification rate
influences the formation of bubbles in semiconductor crystals.
Gallium arsenide crystals promise important advantages for electronic
applications, operating at high speeds and using less power than
traditional silicon semiconductors.
- Over the past 24 hours, Payload Commander Kathy Thornton, Payload
Specialist Al Sacco and Mission Specialist Cady Coleman conducted a
series of Drop Physics Module experiment runs for Dr. Robert Apfel of
Yale University. The experiment examines the influence of chemicals
called surfactants on the behavior of liquid drops. Surfactants are
substances that migrate toward the free surfaces of liquids, resulting
in a reduction of surface tension, or a weakening in molecular
"skins." For instance, soap contains surfactants which makes water
"wetter." The various crew members levitated different sized drops
containing surfactants, then squeezed them with sound waves. Drop
Physics Module team members observed the drops' oscillations and
surface distortions from two perspectives, both of which were
transmitted to the ground simultaneously by Hi-Packed Television.
- Dr. Apfel used results from related USML-1 experiments to confirm
and adjust theoretical models. This mission's experiments will help
him refine these theories, which apply to processes as widespread as
the production of cosmetics to the recovery of oil spills and
- Sacco performed operations for the Colloidal Disorder-Order
Transition investigation, a Glovebox study which seeks to answer
fundamental questions about how liquids become solids. Tiny spheres
suspended in a fluid were clustered together in crystallized
formations, in a model of how atoms arrange themselves to transition
from liquid to solid states. Research of this type could lead to
improvements in materials processing on Earth, such as developing
micromachines or better surgical tools. The science team expects to
get at least a 90 percent return on science from their data, despite
time lost troubleshooting several equipment problems.
- Payload Specialist Fred Leslie followed up on two Glovebox studies
which delve into fundamental factors of fluid behavior. He
photographed the position of red fluid inside a mathematically
designed, transparent container for the Interface Configuration
Experiment. The study examines how angles within a container affect
the way fluids shift within it.
- Leslie also completed the mission's second run of the Oscillatory
Thermocapillary Flow Experiment, heating the surface of silicone oil
in a container whose depth equaled its diameter. The run successfully
pinpointed the transition between steady and unsteady heat-induced
fluid flows. The investigation duplicates the Surface Tension Driven
Convection Experiment (STDCE), but uses containers with different
depths to provide additional insight into the fluid-flow phenomenon.
According to Project Scientist Alex Pline, results were consistent
with STDCE results from earlier in the mission. The team is building
an extensive catalogue of data on these subtle fluid motions which can
affect materials processing on Earth.
- Leslie was unsuccessful in several attempts to coax fuel drops onto
a fiber in the Glovebox Fiber Supported Droplet Combustion
investigation. The heptane fuel stubbornly adhered to deployment
needles, probably due to degradation of the needles' non-stick
coating. The Glovebox team is comparing notes with members of other
experiment teams and USML-2 payload controllers to identify other
non-stick substances aboard which might be substituted.
- On Monday, October 30, 1995, 5 p.m. CST, STS-73 MCC Status Report # 21
- Columbia will remain in the "gravity gradient" attitude, with its
tail pointing toward the Earth and its port wing in the line of
travel, until about midnight tonight when the orbiter will begin a
14-hour thermal conditioning period with its belly pointed toward the
Sun. That change in attitude will mark the second of four scheduled
thermal conditioning periods designed to warm up some portions of the
orbiter that, in the gravity gradient attitude, have been exposed to
the extreme cold of space for long periods of time. The thermal
conditioning is necessary to warm the orbiter's tires to levels
necessary to support landing.
- The Red Team handed over science operations to their colleagues on
the Blue Team at 2:38 p.m. CST. The Blue Team will be on duty until
2:38 a.m. Tuesday when the Red Team returns to work.
- On Monday, October 30, 1995, 6 p.m. CST, STS-73 Payload Status Report # 17
reports: (10/09:07 MET)
- The USML-2 Crystal Growth Furnace experiment team today successfully
grew a crystal of gallium arsenide with a dopant, or impurity, added.
Later, the crystal will be tested to determine if the dopant was
evenly distributed during the crystal's growth. Slightly more than
one-inch (7 centimeters) in length, the semiconductor crystal grew for
12 and one half hours. To produce high-quality gallium arsenide
crystals, scientists need to understand the processes by which
chemical impurities are introduced, whether intentionally or
unintentionally. Electronic devices made from these crystals operate
at higher speed and use less power.
- After setting up the Surface Tension Driven Convection Experiment
this morning, Payload Specialist Al Sacco stepped aside and surface
tension experiment team members on the ground were able to run the
experiment's heater power by remote commanding. Team members observed
the experiment performance via a multi-channel digital television
link. The remote commanding capability gave the team a chance to get
extra data on their experiment, while Sacco and Mission Specialist
Kathryn Thornton were working with other investigations. The surface
tension experiment studies the transition between steady fluid flows
to oscillatory, or unstable, fluid flows.
- Today's surface tension experiment runs featured a test cell with a
spacer disk inserted into the bottom of the chamber. This cut the
chamber's depth in half, thereby lowering the amount of fluid in the
cell. An increase in power was necessary to push the fluid flows to
the transition point, giving the experiment team even more data for
discussion and post-mission analysis. Studying surface tension-driven
fluid flows holds valuable applications in areas of materials
processing such as the production of high-tech crystals, metals,
alloys and ceramics.
- Dr. Robert Apfel with Yale University, whose experiment studies the
effect of surfactants, or chemicals, on the surface of a liquid drop
in the Drop Physics Module, says the drops' large oscillations, caused
by sound waves, have revealed detailed motions in the sample during
the experiment runs. Data he has thus far received on his experiment
is clear, concise and definitive, allowing him to measure specific
oscillation points. He will use this information in post-mission
analysis, comparing it to his numerical predictions.
- Crew members continue to keep an eye on a Spacelab VCR which
experienced a brief problem while recording Drop Physics Module data
early this morning. The VCR is up and running, and the drop physics
team believes all their data was captured on the experiment film
magazine when the problem occurred.
- Sacco spent about two hours this afternoon photographing and filming
the progress of experiments in the Commercial Generic Bioprocessing
Apparatus, a facility which is used for a wide variety of life-science
experiments. The development of the tiny brine shrimp living in the
facility are of interest to investigators, as they could shed light on
the importance of gravity in human development and aging. The
different stages of the growing protein crystals within the facility
were also recorded in today's photo session. Proteins are molecules
which serve biological functions. Understanding the structure of
these molecules gives scientists an idea what other molecules would
interact with the protein and change the way it functions, for
instance to help cure or treat an illness.
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