LG-1997-02-450-HQ
ABOUT THE PICTURE
LMS astronauts Susan J. Helms and Terence T. Henricks prepare a
furnace sample to study how metals solidify in microgravity.
THE LMS MISSION
The Lite and Microgravity Spacelab (LMS) was not only a mission to
gather new scientific information about microgravity, but was also
a practice mission for the future International Space Station. The
space station laboratory will include both microgravity and life
science experiments. Using the station plan as a model, LMS
combined microgravity science experiments (which investigated how
microgravity affects physical and chemical processes) and life
science experiments (which investigated how microgravity affects
human processes).
Although the two groups of experiments had different goals, they
made a good match on LMS. The microgravity science equipment used
a lot of space in the shuttle and large amounts of the shuttle's
power supply but needed little attention from the crew. The life
sciences equipment required less space and power but involved the
astronauts as subjects.
Scientists from 10 countries participated in LMS experiments. NASA
furnished the spacecraft, the Space Shuttle Columbia, and the
European Space Agency supplied Spacelab, a module that fits inside
the shuttle's cargo bay and provides a pressurized workspace for
astronauts to conduct experiments. In addition, six European
countries, the U.S. and Canada contributed experiment equipment
and crew to the LMS mission, which flew in June 1996.
To keep all the LMS partners in touch with each other and the
shuttle during the mission, monitoring and control stations were
set up in Italy, Belgium and France, in addition to the Payload
Operations Control Center in Alabama. The new ability to control
flight experiments remotely will be important when scientists need
to monitor their experiments aboard the completed international
Space Station tor months at a time.
SCIENCE HIGHLIGHTS
BIOTECHNOLOGY: On LMS, scientists
grew crystals of viruses and proteins. Crystals grown in
microgravity are generally larger than those grown on Earth.
Gravity causes flows in the solution that disturb crystal
formation, but in microgravity, these flows are greatly reduced,
which allows the crystals to grow bigger. Scientists will examine
the space-grown crystals using x-rays to determine their molecular
structure. LMS scientists also videotaped the formation of the
crystals on the shuttle so that they could carefully study the
growth process. Clues about structure gained from the crystals
will aid in the design of disease-fighting drugs and plants that
can resist damaging viruses.
FLUID PHYSICS: During LMS, scientists
learned about controlling liquids with electric fields. In
microgravity, a column of liquid can be contained with
electricity, but on Earth the force of gravity is too strong and
the column of liquid breaks. Results of the LMS experiment may
help engineers to design micropumps. which are tiny pumps that use
electricity to control liquid flows LMS scientists also learned
about how bubbles in a liquid behave in microgravity. where
bubbles do not necessarily rise. This information may help
engineers to design more efficient fuel, oxygen, and water systems
on spacecraft as well as to improve space experiments that involve
liquids.
MATERIALS SCIENCE: Particles are
often added to metals to make them stronger. On Earth, when these
particles are added to a melted metal, they settle to the bottom
or rise to the top because they are a different density than the
liquid. This settling into layers is called sedimentation. In
microgravity, sedimentation is reduced, so that when the melted
metal cools, particles are evenly distributed throughout the
metal, improving its strength. On LMS, scientists not only
successfully mixed particles into metals, they also observed what
would happen to the particles if the melted metal containing them
was cooled very slowly. They found that the particles were pushed
out of the metal as it cooled, instead of being captured in it.
The results of the particle "pushing" experiment will help
scientists to understand problems such as frost heaving, which
occurs when water that has seeped into the ground freezes very
slowly and pushes out the particles of dirt.
WHAT IS MICROGRAVITY?
The force of Earth's gravity extends far into space. You would
have to travel 6.37 million kilometers (almost 17 times farther
away from the Earth than the Moon) to reach a point where the
strength of Earth's gravity is one-millionth of what it is on
Earth's surface. Why, then, do astronauts and objects float in the
space shuttle as if they were weightless? Weight is the force with
which a body is attracted to the Earth. If an object is falling
due only to the force of gravity, its apparent weight (that which
could be measured while in freefall) is nearly zero. Any object in
a state of freefall experiences microgravity, or near
weightlessness. An orbiting spacecraft is actually falling around
the Earth. The spacecraft's altitude and speed cause its tall to
match the curvature of the Earth, so that it never hits the Earth
but continually orbits the planet. All objects carried by an
orbiting spacecraft are also in a state of freefall.
To learn more, try these Internet addresses:
http://microgravity.msad.hq.nasa.gov/
http://liftoff.msfc.nasa.gov/spacelab/lms/welcome.html