Search Marshall


Text Size

Fact sheet number: FS-2004-01-02-MSFC
Release date:

Miscible Fluids in Microgravity (MFMG) Investigation

Experiment Name: Miscible Fluids in Microgravity (MFMG)

Mission: Uses onboard apparatus and materials to conduct an experiment during International Space Station Expedition 8 and/or Expedition 9

Experiment Location: Destiny Laboratory Module

Principal Investigators: Dr. John Pojman, University of Southern Mississippi, Hattiesburg, Miss., Co PI: Vitaly Volpert, Université Lyon I, Hermann Wilke, Institute of Crystal Growth, Berlin, Germany

Project Scientist: Mark Paley, NASA Marshall Space Flight Center, Huntsville, Ala.

NASA Managers: Melanie Bodiford and Ron Young, NASA Marshall Space Flight Center


On Earth and in space, fluids are essential for most living things and for making materials and operating machines. But fluids do not behave the same on Earth and in the low-gravity, or microgravity, environment inside the orbiting International Space Station.

In space, processes usually masked by Earth's gravity become much more evident -- playing a bigger role in the process of mixing fluids to make materials.

This experiment studies how miscible fluids -- those that completely dissolve -- interact without the interference of gravity.

Studying the interactions between molecules that make up liquids is important for improving numerous processes ranging from making plastics to manufacturing medicines.

Experiment Operations

Immiscible fluids, like oil and water, exhibit "interfacial tension" or surface tension. Oil and water are made of different types of molecules that pull on each other -- preventing the two substances from remaining mixed together -- even after stirring.

On the other hand, when miscible fluids -- like the honey and water -- are mixed on Earth, they dissolve and combine easily because they are made of similar types of molecules.

This experiment will test a 100-year-old-theory impossible to confirm on Earth. In the mid-1800s, Dutch scientist Diedrick Korteweg predicted that until the molecules of miscible fluids like honey and water diffuse together and become a uniform solution, these fluids would act like immiscible fluids.

In microgravity, if a stream of one immiscible fluid is injected into another, the stream will break into drops. This happens because of a surface-tension-driven-phenomenon called Rayleigh-Tomotika instability. This test will determine if the same breakup occurs with two miscible fluids by injecting honey into water and observing if the honey stream breaks into drops.

Gravity prevents this experiment on Earth. Because the honey is denser than water, the honey sinks in the water. Also in microgravity, a drop of immiscible fluid injected into another fluid will always become spherical. For this experiment, the crew will inject a drop of water into honey to see if it behaves the same way.

Another interesting phenomenon that a drop of an immiscible fluid can exhibit is droplet migration. An immiscible drop can move in weightlessness when it is placed in another fluid that has a variation in a temperature - a temperature gradient. Using honey and water, the crew member will test if a drop of water in honey and a stream of honey in water will migrate in a temperature gradient.

To conduct this experiment, astronauts will use equipment already on board the Space Station: honey used to sweeten tea and syringes used for life sciences experiments.

For the first experiment, astronauts will use a syringe to inject dyed honey into water. Within 2 seconds, they will create a stream of honey 2 centimeters long. Under normal gravity, the stream would sink. In weightlessness, the stream can be formed but it is not known if the stream will break up like a stream of oil in water would do - an effect known as the Rayleigh-Tomotiak instability.

In the second part of the experiment, astronauts will inject an aspherical drop of dyed water, approximately 0.5 milliliters (0.02 fluid ounces) into the honey for 5 seconds. The process will be videotaped for 30 seconds to determine if the aspherical drop of water will spontaneously assume a spherical shape-which is what a drop of water would do in oil.

To test for thermal migration of miscible fluids, the syringe will be attached to the Commercial Generic Bioprocessing Apparatus (CGBA), maintained at body temperature, 37 °C. This will create a temperature variation across the fluid in the syringe. When the drop of water or the stream of honey is injected, video will reveal its migration and show the direction of its movement.

Investigators on the ground will be able to watch video of the experiments as they are conducted in space. The results will be compared to computer simulations performed by Vitaly Volpert and Nick Bessonov at the Université Lyon I in France.


Demonstrating the existence of an effective interfacial tension in miscible fluids will open up a new area of study in materials science. These fluid flow processes may affect the way many polymers are made. This research could help scientists improve the way plastics and other polymers are produced on Earth and in space.

More Information

More information on this experiment and other Expedition Eight experiments is available at: