LG-1997-02-452-HQ
ABOUT THE PICTURE
During the shuttle docking with Mir in September 1996, astronaut
Thomas D. Akers guides a protein crystal growth experiment trom
the shuttle to the core module of the Russian station.
NASA/MIR MICROGRAVITY
PROGRAM
NASA has formed a partnership with the European Space Agency and
the space agencies of Japan, Canada, and Russia to build a space
station to be used as a microgravity laboratory. Scientists from
all the partner countries will conduct experiments in the station,
where they can study forces that are always present on Earth but
are hidden by the stronger force of Earth's gravity.
Although NASA has used the space shuttle as a science laboratory,
the shuttle can stay in orbit tor 17 days at most. On a station,
experiment equipment will be in orbit for years, and experiments
can be run for months at a time. This will give scientists more
time to collect important data, but NASA will face new challenges
in supporting such long-term operations. To gain space station
experience, NASA approached Russia about conducting experiments on
the Russian Space Station Mir (Mir means "peace" in Russian).
The core module of Mir was launched into orbit in 1986. This
module consists of living quarters and lite support tor
cosmonauts. Later, more modules were added to Mir to provide space
tor scientific research. Atter a decade of use, Mir is nearing the
end of its lifetime, but Russia has learned important lessons
about conducting long-term space missions.
In 1994, Russia agreed to allow the U.S. to use Mir to gain
experience for the International Space Station, which is projected
to be completed in 2003. NASA calls this agreement "Phase 1" of
the International Space Station era. In exchange tor installing
equipment on Mir and having an astronaut onboard the Russian
station to conduct experiments, NASA provided funds to help add
another science module to Mir. The NASA/Mir microgravity program
includes nine dockings of the shuttle with Mir to carry
experiments and crew to and from the station.
SCIENCE HIGHLIGHTS
COMBUSTION: The Mir combustion
investigations will focus on how flames burn in microgravity and
how quickly flames will spread in different air flow conditions
and over curved and flat surfaces. Results may help improve fire
prevention and control on spacecraft and on Earth.
FLUID PHYSICS: In microgravity, there
is no up or down, and this makes fluids (liquids and gases) behave
very differently than they do on the ground. Mir experiments will
explore how fluids slosh in containers and how they will behave in
containers of different shapes. Knowledge of fluid flows in
microgravity is important tor designing fuel, water and oxygen
systems on spacecraft.
MATERIALS SCIENCE: Several
experiments on Mir will explore gravity's effect on how metals
solidify. Through these experiments, scientists will learn to
better control the formation of metal crystals to produce metals
with more desirable properties.
PROTEIN CRYSTAL GROWTH: Scientists
seek to understand the molecular structure of proteins and
viruses. This knowledge helps in designing disease-fighting drugs.
On Earth, gravity interferes with the growth of the large protein
and virus crystals needed for these molecular studies. For the Mir
experiments, scientists are able to study proteins and viruses
that take longer than 17 days (the shuttle's limit) to
crystallize.
TISSUE CULTURE: For the NASA/Mir
program a bioreactor will be installed onboard Mir. A bioreactor
is a facility used for growing living cells. Outside the body (in
vitro), cells tend to grow in flat two-dimensional formations.
NASA's rotating bioreactor suspends the cells in fluid. allowing
them to grow three-dimensionally as they do inside the body (in
vivo). Using the bioreactor in microgravity should enhance this
three-dimensional growth. The first sample to be grown in the
bioreactor on Mir will be cartilage tissue. This experiment will
help scientists discover ways to grow tissue tor replacement of
damaged cartilage in humans.
WHAT IS MICROGRAVITY?
The force of Earth's gravity extends far into space. You would
have to travel 6.37 million kilometers (almost 17 thnes 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 stalling
due only to the force of gravity, its apparent weight (that which
could be measured while in freetall) is nearly zero. Any object in
a state of treefall experiences microgravity, or near
weightlessness. An orbiting spacecraft is actually falling around
the Earth. The spacecraffs 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 Intcrnet addresses:
http://shuttle-mir.nasa.gov/
http://www.osf.hq.nasa.gov/mir.html
http://microgravity.msad.hq.nasa.gov/