LG-1997-02-454-HQ
ABOUT THE PICTURE
This illustration shows the Spacelab module in the cargo bay of
the space shuttle. Crewmembers use the tunnel as a passageway
between the shuttle's cabin and the science laboratory where
microgravity experiments are conducted.
MSL MISSION SERIES
The Microgravity Science Laboratory (MSL) mission series was
designed to build on the successes of previous microgravity
missions and to explore new ways to observe and measure gravity's
effect on chemical and physical processes. NASA chose Spacelab.
which is a module built by the European Space Agency to fit inside
the shuttle's cargo bay, as the microgravity laboratory for the
MSL series. Spacelab is enclosed and pressurized to provide a
comfortable workspace tor astronauts to conduct experiments. To
reach the Spacelab from the main decks in the front of the
shuttle, astronauts must float through a narrow tunnel connecting
the two areas.
Some of the experiment equipment that will be installed in the
Spacelab for the MSL series has been used before on other
microgravity missions and will give scientists a chance to probe
previous results that were surprising or interesting. Other MSL
experiment facilities are new and will allow scientists to observe
the behavior of some types of fluids and flames in microgravity
for the first time.
For the first MSL mission, a Glovebox and a Protein Crystal Growth
Facility will be installed in the shuttle's middeck, which is in
the lower front portion of the shuttle. A Glovebox is a small box
that can that can be tightly sealed and has gloves attached to it
for the astronauts to reach the experiment inside. The Glovebox
protects astronauts from any hazardous experiment byproducts. The
Protein Crystal Growth Facility, also a small piece of experiment
equipment, has temperature controls to regulate the growth of
protein and virus crystals. The first MSL mission, MSL-I, is
planned for launch in the spring of 1997.
SCIENCE HIGHLIGHTS
BIOTECHNOLOGY: Scientists grow
crystals of proteins and viruses to understand their molecular
structure. This knowledge helps in designing disease-fighting
drugs and producing plants with greater nutritional yield. On
Earth, gravity interferes with the growth of the large crystals
needed for molecular studies. During the MSL series, scientists
will use several methods tor growing crystals of many protein and
virus samples.
COMBUSTION: Combustion, or burning,
is often difficult to study on Earth because gravity causes
turbulent flows around the flame. Heated gas rises from the top of
the flames and cool gas is rapidly drawn in at the bottom to
replace it. In microgravity, these flows are absent, allowing
scientists to study the combustion process with less interference.
MSL scientists will investigate how flames spread over a droplet
of fuel; they will measure how much soot a flame produces; and
they will observe the formation of flameballs, which occur when a
flame breaks up into small balls of fire. Understanding these
basic aspects of combustion may lead to more efficient engines and
less air pollution on Earth.
FLUID PHYSICS: A colloid is a mixture
of particles of one substance finely dispersed within another. An
aerosol spray is an example of a colloid mixture because it is a
gas that has liquid particles mixed in it. MSL scientists want to
know how the particles affect a colloid mixture as it changes from
a liquid to a solid. On Earth, gravity pulls the particles to the
bottom of the liquid, which causes the top layer of liquid to
behave differently trom the bottom. In microgravity, the particles
will stay evenly dispersed throughout the liquid, so the whole
sample will behave the same way as it changes to a solid. MSL
scientists predict that the particles will cause the liquid's
molecules to line up in a more ordered way.
MATERIALS SCIENCE: On Earth,
the walls of a container often interfere with metals as they
solidify. Melted metals will first form crystals wherever the melt
touches the container. This contact influences the structure of
the solid metal and what properties it will have. During the MSL
missions, scientists will use the microgravity conditions to
levitate, or lift, materials in order to process them without a
container. The substance will form crystals at the same rate
throughout the sample because there are no container walls.
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 fall 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://liftoff.msfc.nasa.gov/spacelab/msl/welcome.html
http://microgravity.msad.hq.nasa.gov/