LG-1997-02-449-HQ
ABOUT THE PICTURE
IML-2 Mission Specialist Carl E. Waltz has just floated through
the tunnel that connects Columbia's cabin to the Spacelab module.
The module has all the equipment necessary for conducting the
IML-2 experiments.
IML MISSION SERIES
The International Microgravity Laboratory (IML) mission series
was planned to be a cooperative project involving scientists,
astronauts and engineers from 13 countries. NASA, the European
Space Agency (ESA), and the space agencies of Canada, France,
Germany and Japan agreed to share resources for conducting science
experiments in microgravity and to share the results of those
experiments.
NASA furnished the spacecraft for the IML series, the Space
Shuttle Columbia. ESA provided Spacelab, a module that fits inside
the shuttle's cargo bay and offers an enclosed and pressurized
workspace in which astronauts conduct experiments. The other
partner countries contributed equipment for conducting
experiments. The first mission in the series, IML-I, took place in
January 1992, and IML-2 flew in July 1994. All the countries
involved in the series declared it a great success. By pooling
resources, scientists were able to gather more data, space
agencies were able to save time and money, and countries learned
to work together in space.
This lesson in cooperation will be important for operations on the
International Space Station, which will be built and shared by the
United States, Europe, Canada, Japan and Russia. It will be used
as a permanent microgravity laboratory by scientists from all the
participating countries.The first module of the station will be
put in orbit in the fall of 1997. Its projected completion date is
2003.
SCIENCE HIGHLIGHTS
CRITICAL POINT TRANSITIONS:
During the IML series, scientists investigated the liquid/vapor
critical point transition. At a specific temperature and pressure,
the gas phase of a substance can become the same density as the
liquid phase. When this happens, it is very difficult to tell
whether the substance is a liquid or a gas because it has
properties of both. A substance near this critical point will also
experience a change in the way it carries heat. This change
particularly interests scientists, but to study the transition on
Earth is difficult because gravity distorts results. In
microgravity, scientists are able to make more accurate
observations.
ELECTROPHORESIS: Biological solutions
are used to make pharmaceutical drugs. Improving a solution's
purity by separating and removing unwanted molecules improves the
drug's effectiveness. IML scientists explored a method of
separation that uses electricity to charge and attract particular
molecules. This process, called electrophoresis, is limited on
Earth by the strong force of gravity. In microgravity, however,
the process is more successful.
FLUID PHYSICS: On Earth, gas bubbles
in a liquid rise because the gas is less dense than the liquid.
IML experiments helped to predict how bubbles would behave in
microgravity, where the bubbles and the liquid are weightless.
Bubbles in fluid systems designed for space can cause problems.
IML results may be used to improve fluid systems on spacecraft,
such as fuel, oxygen and water systems.
MATERIALS SCIENCE: Metal alloys are
made by combining several metals. On Earth, combining metals of
different densities is difficult because the heavier metals sink
when they are melted together. This settling process, called
sedimentation, causes layers to form as the metals cool into a
solid. In microgravity, sedimentation is reduced, and IML
scientists were able to form alloys of metals that are almost
impossible to combine on Earth.
PROTEIN CRYSTAL GROWTH: IML
scientists grew larger crystals of proteins and viruses in
microgravity than they can on Earth. The larger crystals make it
easier for scientists to determine the molecular structure of the
proteins and viruses, and this information can be used to design
disease-fighting drugs. Crystals grown on the IML missions
included the protein human serum albumin (which is found in the
human circulatory system) and the tobacco mosaic virus (which
affects plants).
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://microgravity.msad.hq.nasa.gov/
http://www.ksc.nasa.gov/shuttle/missions/sts-65/mission-sts-65.html