AUTH space experiment over the Atlantic – In zero gravity conditions

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The “Low-g emulsions” experiment was successfully completed

An experiment in weightless conditions was performed by a scientific team of the Aristotle University of Thessaloniki.

Over the Atlantic and starting from Bordeaux, France, a specially configured airplane (Airbus A310) performing 93 consecutive steep ascents and descents following a flight path in the shape of a parabola gave the Multiphase Systems Dynamics team of the AUTH Chemistry Department, led by the Chemistry professor Thodoris Karapantsio, the ability to check in weightless conditions (like in space) the accuracy of what he had studied and designed in the university laboratory.

The ‘Low-g emulsions’ experiment was successfully completed on 27 October. It was carried out as part of the Parabolic Flights campaign of the European Space Agency and concerned the study of phenomena that determine the stability of emulsions, which are widely used in a variety of applications (insecticides, polishes, lubricants, paints, varnishes but also in food, drugs, pesticides).

The experiment was purely Greek both in the design and construction of the experimental device and in the scientific team that operated the device inside and outside the aircraft during the flights. The experiment was carried out in the context of the participation of the AUTH team in a very large research program for the study of emulsions (SMD-PASTA) of the European Space Agency, which has been ongoing for months on the International Space Station in orbit around the earth with the participation of teams from Universities and Research Institutions from USA, Germany, France, Italy and Japan.

“The experience of the AUTH team with a 5-hour stay in weightlessness”

The AUTH team is considered one of the most experienced in Europe, having flown in a total of nine parabolic flight missions of the European Space Agency with a total time spent in zero-gravity conditions of over 5 hours. In this Parabolic Flight Campaign, the AUTH flying team apart from Mr. Karapantsiou consisted of the flight operators Dr. Sotiris Eugenides (Chemist) and Angeliki Chondrou (PhD candidate, AUTH), and from the ground support team, Mr. Margaritis Kostoglou (Professor of the Chemistry Department, AUTH), and Mr. Triantafyllos Tsilipiras (Technician, AUTH).

“The Greek mission, with its participation in a cutting-edge research program, conveys a strong message to the scientific – and not only – community inside and outside the borders: That Greece has the appropriate specialized scientific potential to perform demanding experiments and produce high-quality scientific work. But at the same time, the message is also given to our young people, that Greece has not lost the ability to be a place of opportunities and this has a strong symbolism as a means of stopping the wave of flight of scientific capital that our country has been experiencing in recent years”, he told APE-MPE Mr. Karapantsios.

Describing the feeling of weightlessness, as it is caused in parabolic flights, he explained that the element of hyperintensity dominates both during and after the flight is completed. All the groups participating in these experiments receive special training, as well as preventive medication for the side effects that the sudden change in gravity conditions can cause to the human body.

“Participating teams are selected by the European Space Agency after an evaluation based on strict scientific criteria, while the technical specifications and safe operation of each experiment are checked by specialized personnel who visit the teams in their laboratories throughout their preparation”. noted Mr. Karapantsios.

The goal of each experiment participating in parabolic flights is to take advantage of the 25 seconds of zero gravity in each of the 93 parabolics performed in total over the 3-day flights, so as to study the natural phenomenon of interest. And if the average person will wonder what someone manages to observe within these 25 second intervals, Mr. Karapantsios assured that the time is more than enough for the study of phenomena related to the interaction of drops and bubbles in dispersion and that also in this mission the team gained valuable information for their research project.

Each parabolic flight campaign involves approximately 10 Scientific Teams and each campaign consists of seven days of final testing of the experiments followed by three days of flights. The previous participation of the AUTH team in a parabolic flight mission took place in May 2017, while the next one in which it will participate is scheduled for October 2023.

“The importance of the experiment”

Regarding the importance of the AUTH team’s experiment, Mr. Karapantsios pointed out that “in principle, it lies in the scientific significance of the results collected in zero-gravity conditions. In particular, the experimental results showed the mechanisms by which emulsions of particular stability can be prepared even with the use of a small amount of chemical substances (surfactants), as long as the appropriate emulsification conditions are chosen”.

The experiments in the experimental set-up of the AUTH concerned the study of the dynamic behavior of organic liquid drops (oily phase) within a continuous aqueous phase. Emulsion is defined as the dispersion of droplets of one liquid in another liquid, with the two liquids not mixing with each other.

In earth gravity conditions, due to the difference in density of the two liquids of the emulsions, the buoyancy leads to the rapid separation into two distinct layers, one of oil and one of water, as a result of which it becomes impossible to study the movement and interaction of the drops. Conversely, in zero gravity the gravitational effects are eliminated. This allows the study of the dynamic behavior of droplets and their interactions (droplet coalescence and aggregation), which contributes to a better understanding of emulsion destabilization mechanisms and will lead to new data that will improve the quality of industrial products in emulsion form.

In the APTH experiments, one of the three parameters is changed each time: 1) concentration of emulsifier (surfactant), 2) oil-water phase ratio and 3) frequency and duration of movement of the piston that causes emulsification. All of the above affect the size distribution of the oil droplets of the produced emulsions and consequently their stability.

Three diagnostic techniques were used in the experiments: a high-speed video recording camera with the ability to record in milliseconds the collisions of neighboring drops, a high-resolution photographic camera with the ability to automatically capture images at prescribed time intervals, an electrical impedance spectroscopy device to monitor the evolution in time of the volume fraction of the dispersed phase (oil phase droplets).

RES-EMP

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