Fluids in Space, Shaken Not Stirred
James Bond might be the first to tell you that a well-shaken martini is a vast improvement over one that has settled and separated. A good mixture depends on understanding exactly how much to agitate a drink, as well as how quickly the ingredients will settle and if there are other mediating factors, such as temperature. If Bond really wanted to understand the science of his spirits, he could follow the examples of researchers who sent fluid mixture experiments to the International Space Station
The Selectable Optical Diagnostics Instrument-Influence of Vibrations on Diffusion of Liquids, or SODI-IVIDIL
, investigation addressed the question of fluid physics fundamentals while looking at how heat and particles move through liquids in microgravity. The scientists who conducted the space station investigation from October 2009 to January 2010 were not interested in cocktails, however, but instead wanted to verify current math models to predict liquid mixture behavior.
Information from this study adds to the collective knowledge of fluid physics, advancing that area of science.
"Any research initiative is a small step forward, a venture into a land of unknown, toward a better understanding of nature and the world we are living in," said Valentina Shevtsova, Ph.D., principal investigator for SODI-IVIDIL at the Microgravity Research Center, ULB, Belgium
. "Before this venture is realized, much work is needed to increase the chance of success. And this is where the pre-experimental computer and theoretical studies rule."
Researchers knew that studying reduced convection buoyancy -- the transfer of heat by movement -- aboard the space station could reveal fluid mixture behaviors hidden by gravity in experiments on the ground. Still, they needed to check if there were any side effects from the minor on-orbit tremors, known as g-jitter, such as crew movements or mechanical vibrations that could distort data.
To perform this series of experiments, researchers used the SODI optical instrument, which also helps with other station studies, such as SODI-Colloid
. The European Space Agency, or ESA, built the SODI instrument for use aboard the station for fluids research in the space environment. The crew put the IVIDIL sample cells into SODI for processing and observation. The liquid binary solution samples, which are essentially fluids made up of a two-part mixture -- similar to if Bond had vodka and water instead of his trademark martini -- were then tested for their response to various vibrations.
After 55 repetitions of the experiment, researchers found that only major space station vibrations caused impacts, such as orbital debris avoidance maneuvers or dockings and undockings of spacecraft. The more common minor movements that are part of daily life aboard station did not influence the samples.
"The SODI-IVIDIL experiment clearly showed that onboard jitters do not affect fluid investigations of this type in microgravity, paving the way for future studies with more complex samples," said Shevtsova.
This is the first successful station study to gauge the impact of on-orbit g-jitter, providing benchmark values for future fluid diffusion experiments. These results provide proven numbers for equations to predict movement of liquids, which were not possible to obtain on Earth, due to gravity.
Now that scientists know their numerical models are reliable, they can use them with confidence as a reference point as they move forward with additional research in the area of fluid physics and in physical and life science studies aboard station. This is good news for future station investigations, such as Diffusion Coefficients in MIXtures, or DCMIX, and Vibrational Phenomena In Liquids, or VIPIL, as well as applications for space equipment.
"The studied phenomenon in SODI-IVIDIL allows for the control of fluids in microgravity important for material processing, space-enabling operations and even life support," said Shevtsova. "European scientists expect to obtain bullet-proof benchmark results from future space station studies with three component mixtures, such as DCMIX, to validate ground experimental techniques."
So what does this study mean for those of us on Earth, since we are not likely worried about Bond's quest for the perfect martini in an orbital lounge? These results actually have direct applications to petroleum research.
Data from these space studies may help the oil industry generate formulas to predict correct measurements for the liquid to gas ratio in potential wells. This information aids geophysics and mineralogy experts as they evaluate the capacity of reservoirs -- collections of natural resources that lay hidden in the ground. Using these formulas could prevent costly mistakes during exploration, leading to more accurate and affordable speculation.
"The convection flows created by vibrations in microgravity are similar to the convection created on the ground by buoyancy," said Shevtsova.
While SODI-IVIDIL examined a binary solution, it paved the way for more complex mixture research on orbit by showing that g-jitter would not complicate the results. For instance, DCMIX will look at a three part liquid and other, more complex solutions will follow. DCMIX is scheduled to launch aboard a Russian Progress spacecraft to the space station in the summer of 2013. Since oil is a multicomponent mixture, as this microgravity fluid physics research continues to evolve, so also will the advances made in exploration in space and on Earth.
International Space Station Program Science Office
NASA's Johnson Space Center