On Monday February 28, 2022, a new experiment called PASTA will be installed on the International Space Station by ESA astronaut Matthias Maurer, under the guidance of the Belgian control centre B.USOC. The B.USOC operators will then control PASTA from the ground, in order to collect data on the formation of emulsions in weightlessness for transfer to the experiment’s science team. This will enable the development of better theoretical modelling of emulsions, with a wide array of applications in the food, cosmetic, pharmaceutical and manufacturing industries.
What are emulsions?
The inventor(s) of mayonnaise - whoever it may be - probably knew very little about the physics that makes this tasty sauce even possible, for mayonnaise is actually an emulsion. This is what we call a mixture of two liquids that normally do not mix and for which you need to add things like surface-active agents and emulsifiers in order to keep them happy together. Other examples of emulsions are to be found in food (milk, dough, candy…), cosmetics, pharmaceutics (including vaccines), as well as many types of industry (oil, chemicals…).
Like the cooks who discovered the first recipe for mayonnaise, modern industrial processes are generally based on trial and error. It is only with the better understanding of science and the development of computer technology that more advanced and complex theoretical models can be created. However, theoretical models need to be tested in the real world, and for this, calibration and validation is necessary as part of extensive experimental research.
Emulsifying liquids in microgravity
In-depth studies of physical mechanisms are often very difficult to do here on Earth, because of a dominating force called “gravity”. Many phenomena at play are hidden by this force, both in amplitude (the phenomena are so small they are invisible) and time (the phenomena are extremely short-lived). Here is where microgravity research platforms, such as the International Space Station (ISS), prove their value by allowing us to focus on these phenomena with more accuracy and for extended periods of time.
The PArticle STAbilised emulsions experiment - PASTA for short – placed inside the Fluid Science Laboratory (FSL) in the European Columbus module of the ISS, will be studying the stability of different emulsion compositions in microgravity. Previously, FSL already allowed for the study of phenomena such as:
- the geological mantle-crust interaction in a miniature model of Earth in the Geoflow experiment
- the dynamics of granular material in the CompGran experiment
- the boiling processes in microgravity with the RUBI experiment
- and the ageing of wet foams in FOAM-C
Technical details of the mission
Launch and installation
On February 19, 2022, an Antares rocket launched the Cygnus NG-17 cargo mission to the ISS, carrying a retrofitted Soft Matter Dynamics (SMD) experiment container and about 16 PASTA sample cells, containing a variety of mixtures of oil and water with different surfactants (compounds that lower the surface tension between two liquids to allow them to mix more easily). It was decided to retrofit the engineering model of SMD that was used on the ground for operations support and make it flight ready, because the flight model of SMD that has been used successfully since 2018 for CompGran and FOAM-C started showing signs of ageing, making it difficult to fulfill scientific requirements.
Matthias Maurer, the German ESA astronaut currently onboard the ISS will be installing SMD and the PASTA sample cells in FSL on rack on February 28, 2022, starting at 10:00 (GMT+1), before handing over control to the Belgian User Support and Operations Centre (B.USOC) for the day-to-day science operations. The complex crew activity will be live-streamed on the B.USOC YouTube channel. You can also follow B.USOC on Twitter.
The PASTA experiment
Each PASTA sample cell is fitted with a piston that allows us to agitate the mixture within the cell at various frequencies and durations to emulsify the mixture. The sample cells are grouped four by four in sample cell units that can be fitted on a carousel inside SMD. This carousel allows us to place each individual sample cell in the diagnostics position of SMD, where it can be observed with the SMD sensors.
An overview camera takes microscope image sequences in black and white of the sample cell, while a combination of a laser, a line camera and 2 CorrTectors allow for novel diagnostic methods such as Diffusing-Wave Spectroscopy (both transmission and backscattering) and Speckle-Visibility Spectroscopy (allowing Time Resolved Correlation). FSL provides power and data resources to SMD for tele-operations and transmits the images and scientific data to the ground.
The teams & funding
The PASTA science research is made possible through selection and financing of the European Space Agency. The Science Team is led by the Consiglio Nazionale Delle Ricerche (CNR) in Genoa, Italy, with support teams from the University of Parma and several other universities in Italy, France, Germany, Greece, USA, Russia, Japan and several commercial entities.
Part of the science team is Dr. James Ferri, a chemical engineering professor at Virginia Commonwealth University College of Engineering. Ferri has been working since 2010 on formulations to improve the stability of emulsions, which is essential to developing pharmaceuticals, agricultural chemicals and a world of consumer products.
The SMD and sample cell hardware was developed and built by Airbus Friedrichshafen in Germany. Thales Alenia Space Italy in Turin was prime contractor for FSL.
The Belgian User Support and Operations Centre (B.USOC), hosted by the Royal Belgian Institute for Space Aeronomy in Brussels and supported by Space Applications Services, is responsible for the implementation of select European payloads on board the International Space Station (among them FSL, SMD and PASTA), on behalf of the European Space Agency (ESA). It acts as the link between scientists and the ISS environment, and is responsible for preparing and operating those experiments as well as distributing the raw science data from the experiment to the Science Team. B.USOC operators are in contact with other ground control stations across Europe in order to make sure that these experiments are executed as expected, and according to the needs of the scientists.