STS-75 Day 15 Highlights
Back to STS-75 Flight Day 14 Highlights:
- On Thursday, March 7, 1996, 6 a.m. CST, STS-75 Payload Status Report # 20
reports: (13/15:42 MET)
- As the STS-75 mission nears the finish line, the prize for the third
United States Microgravity Payload (USMP-3) research teams is data as
diverse as their experiments. "USMP-3 has given scientists a richness
of information about the space environment, plus real-time interaction
that now extends from a university environment into space," said
USMP-3 Mission Scientist Dr. Peter Curreri. Referring both to overall
mission success and the first remote commanding of a Space Shuttle
microgravity science instrument from a U.S. college campus, he added,
"these accomplishments give us the sense that orbital space is ours to
manipulate to further our knowledge."
- The Critical Fluid Light Scattering Experiment, known as ZENO, is
providing data about today's final approach to the xenon sample's
critical point. A fluid's critical point is the precise temperature
and pressure at which it exists as both a liquid and a gas. At
"supercritical temperatures," fluids make remarkable solvents and have
other applications, such as the use of carbon dioxide at its critical
point to extract caffeine from coffee beans. Near the critical point,
the normally clear xenon sample undergoes some dramatic physical
changes, going from clear to cloudy as the fluid fluctuates between
vapor and liquid states.
- To determine the precise point where this phenomenon occurs, the
Zeno team relies on over 100 channels of data from their experiment,
updated every second, to plot statistical curves that point to the
sample's critical temperature. These plots, known as correlograms,
show the relationship between temperature and pressure to give
researchers clues as to exactly when the critical point is reached.
- "When you get way up near the top of Mount ZENO, everything has to
move very slowly, like climbing through the low-oxygen environment of
a mountain at high altitudes," explained Principal Investigator
Dr. Robert Gammon of the University of Maryland, referring to his
desired slow approach to the critical point. As the sample's
temperature is nudged downward through ever-smaller steps, the ZENO
light-scattering equipment measures the xenon's cloudiness, caused by
variations in density near the critical point. In addition to these
real-time measurements, the ZENO team will further analyze the set of
correlograms, along with light- scattering measurements, to gain
insight into this unusual state of matter.
- Early this morning, the joint U.S./French MEPHISTO experiment began
solidifying its final crystal samples to be brought back to Earth for
post-flight analysis. Using a high-temperature furnace and three
samples of a tin-bismuth alloy, representative of mixtures used for
semiconductors and metal alloys on Earth, MEPHISTO studies the point
at which materials change from the melted to solid state. This is
done by selectively heating and cooling the material, while making
noninvasive electronic measurements -- readings that do not interfere
with the actual crystallization process.
- With help from the Space Acceleration Measurement System, the
MEPHISTO team again adjusted their sample's growth rate in response to
Shuttle maneuvers. This knowledge could lead to the development of
furnaces that compensate for unavoidable acceleration effects in
future space experiments. Today, the team will "flash-cool" a portion
of one of their final samples to preserve the crystal's shape for
- Yesterday, crew members prepared the Middeck Glovebox, a versatile
facility for hands-on lab work in space, for landing. They also ran
procedures to gather engineering data comparing checkout steps
performed in low gravity with similar procedures conducted on the
ground. This gives better assurance that such procedures will work
when this facility flies later this year on the Russian space station
Mir and in the future on the International Space Station.
- Using the Glovebox over the course of the mission, crew members
burned 65 samples, ranging from paper to TeflonŠ, while researchers
closely observed how these samples reacted in low gravity, free from
the effects of rising hot air and falling cool air found on Earth.
The combustion researchers gathered more than 125 percent of planned
scientific data, in the form of video and photographs, in order to
better understand how to control and prevent fires. Other data from
the Glovebox include soot and ashes, as well as particles trapped in
the facility's filters.
- Having completed primary science collection for the Rensselaer
Polytechnic Institute's (RPI) Isothermal Dendritic Growth Experiment
(IDGE), scientists at RPI in Troy, N.Y., and at Spacelab Mission
Operations Control in Huntsville, continue analyzing the dozens of
video images they have been collecting from on board Columbia. The
images will reveal, in greater detail than ever before possible, how
microscopic dendrites grow free from the sedimentation and convection
effects experienced on Earth. As most molten materials solidify, they
form tiny crystals, or dendrites, that look like frost on a cold
window. The size, shape and direction of these crystals dictate the
final properties of the resulting solid materials.
- "Now, we're using our 'telescience' capabilities to probe the effect
of our sample container on solidification," explains IDGE Research
Scientist Dr. Matthew Koss. "This is important because, eventually,
every metal product is affected by the container it's in." After
landing, the IDGE team will use a series of photographs, taken from
two 90-degree angles, to compose three-dimensional images of these
- Over the next 18 hours, the MEPHISTO, ZENO and IDGE experiments will
be deactivated in preparation for Columbia's landing.
- On Thursday, March 7, 1996, 4 p.m. CST, STS-75 MCC Status Report # 28
- Columbia's astronauts have readied their ship to return to Earth
after a journey of more than 6 million miles. Landing at the Kennedy
Space Center is targeted for 7:52 a.m. central time, the first of two
opportunities to KSC tomorrow.
- Early this morning, during the standard pre-landing check of
Columbia's flight control system, one of four data channels
failed. The command path involved is one of four that commands an
actuator to move flight control surfaces during reentry. The command
path is considered "failed", but the three remaining command paths
remain healthy and in position to support tomorrow's planned landing.
- Throughout the night, the reentry flight control team will continue
to review weather conditions at the primary landing site at KSC, as
well as the alternate landing site at Edwards Air Force Base in
- Flight controllers opted to forego an earlier KSC landing
opportunity at 6:16 a.m. central time, because of forecast low clouds
and the possibility of rain and gusty winds. Weather conditions are
expected to improve later in the morning to support the two KSC
- The first landing opportunity would see a deorbit firing of
Columbia's engines at 6:49 a.m. central time, with a landing on
Runway 33 at 7:52 a.m. The second opportunity, one orbit later, has a
deorbit burn at 8:25 a.m., followed by landing at 9:27 a.m.
- If weather precludes a landing at KSC, there are two opportunities
for a Friday landing at Edwards Air Force Base. The first would see a
deorbit burn of Columbia's engines at 8:15 a.m. central time, with
landing on Runway 22 at 9:27 a.m. The second opportunity, has a
deorbit burn at 9:54 a.m. central time with landing at 10:54 a.m.
Weather in California is predicted to be acceptable to support
- If Columbia remains in orbit an additional day due to weather
conditions, there are three landing opportunities available on
Saturday at KSC and three at Edwards.
Go to STS-75 Flight Day 16 Highlights: