The objective of DCMIX, a set of experiments in SODI, is to determine diffusion coefficients of ternary fluid mixture samples. This could lead to a better understanding of mixtures processes, which have a high scientific and industrial interest. For example, they are important to refine petroleum reservoir models and, as such, to obtain a more efficient extraction of oil resources.

Significant Dates

Expedition 38: Soyuz 36 TMA-10M, Launch: September 25, 2013

First Experimental Run November, 2013 September, 2016
Latest Experimental Run February, 2014 November, 2016

Experiment/Payload description

Diffusive processes play a key role in the fluid mixtures and they can be found everywhere in our daily life. Diffusion is the relative motion of a species with respect to the other and it can be caused by a difference in the concentration, the temperature or by a potential gradient. In any case, a reduced gravity environment is essential for obtaining an accurate diffusion coefficients measurement.

DCMIX experiment is performed in cell arrays, each composed of six cells: five “primary” cells are probed by a movable Mach-Zehnder interferometer at two wavelength, while the “companion” cell is probed at a single wavelength.

The DCMIX purpose is:

  1. To measure diffusion coefficients of ternary systems.

  2. To validate measurement techniques used by industry.

  3. To refine the numerical models of mixtures.

  4. To refine and obtain mixing rules allowing the prediction of diffusion coefficients.

Astronaut Mike Hopkins installing the Cell Array for SODI-DCMIX2

Source: NASA


A new round of the SODI-DCMIX experiment is coming up on the first half of 2018. The scientific objective is the determination of the diffusion coefficients of ternary fluid mixture samples, same as in previous DCMIX experiments, but this time instead of having just one mixture with diverse concentrations, three ternary mixtures will be observed under different conditions. The importance of the results obtained with the DCMIX2 experiment has led to the inclusion of three sample cells with Toluene-Methanol-Cyclohexane, which is the same mixture used in the former experiment. The new concentration mixtures covers some interesting zones already not studied and will complement the previous results. Polystyrene-Toluene-Hexane sample cell will be accompanied by a binary mixture cell of Polystyrene-Toluene; the behaviour of this mixture is expected to provide an easy to analyze and interpret scientific data. Last but not least, this will be the first time the thermal and mass diffusion coefficients for a ternary nanofluid mixture are studied in microgravity, with the use of one sample cell of Tetrahydronaphthalene-Toluene-Fullerene mixture.

The experiment setup will be the same as in previous DCMIX experiments, with Microgravity Science Glovebox (MSG) providing resources to the main SODI hardware, which remains on orbit, and that is used to process the new DCMIX cell array that will be uploaded to the ISS. A new item in MSG, the MSG removable window, will make the installation activities easier for the crew, facilitating the installation of SODI inside the work volume.