A weightlessness experiment

Cédric Giraudet and Fabrizio Croccolo in weightlessness

A Weightless Flight to Study CO₂ Storage

In the fall of 2021, the CO2 EX project team lived an extra-ordinary experience, in the literal sense of the word: floating in weightlessness. The objective was to study chemical dissolution behaviors that cannot be reproduced on earth because of gravity.

Bordeaux-Mérignac airport, at dawn. Eleven teams of scientists from all over France and even Germany are about to embark on the “Vomit Comet,” nickname given to zero gravity airplanes. As a preventive measure, they have just been given a shot of scopolamine, an anti-emetic.

And here we go for three hours of giant roller coaster, on board an Airbus A310, accelerating and decelerating. A total of 31 “coasts” (parabolas), for barely 20 seconds of weightlessness each time. And again the next two days. “I was disappointed that no one vomited,” laughs Cédric Giraudet, the CO2 EX project manager (left on top picture).

This was the second session of parabolic flights for the CO2 EX team, but the most important one, the one where measurements were made. It was co-prepared within the framework of a thesis of a 3rd-year student of University of Pau and Pays de l’Adour, Emma Lisoir, who was present on board (picture below).

The first session, one year earlier, had been used as a test for the settings of the device. Will there be a third session? “Not for the moment, says Cédric Giraudet. In an airplane there are many vibrations, which is not ideal for our measurements.” Moreover, preparing a parabolic flight takes a lot of time and energy (see below). The next objective, however, is the International Space Station (ISS), scheduled for 2025-2030.

The CO2 EX Research Project

“CO2 Storage EXperiment,” led by Cédric Giraudet, post-doctoral fellow at LFCR, is a sub-project of the E2S UPPA research chair “CO2 Enhanced Storage,” headed by Fabrizio Croccolo. Carbon dioxide is an important greenhouse gas, and one of the ways to protect the planet could be to store it in deep saline aquifers, i.e. under the groundwater table.

The CO2 EX project involves a series of experiments to understand the mechanisms that generate the convective dissolution of supercritical – i.e., heated and compressed – CO2 when it comes into contact with salt water. The team is studying the evolution of non-equilibrium fluctuations that, on Earth, are amplified by gravity and generate the convection phenomenon. The weightlessness thus allows to develop theories describing the evolution of the system under the effect of gravity. And therefore to validate or invalidate the durability of the CO2 storage process in the earth's subsoil.

In a broader way, the determination of these properties will allow to optimize industrial processes which involve solutions with at least two chemical compounds, in particular in the pharmaceutical, energy, cosmetic and food fields.

The Team


Location: Anglet, Montaury campus

The Device

A light beam, provided by a super luminescent diode, passes through the thermodiffusion cell. In this cell, variations of optical index diffract the light which is observed with a camera placed in near field.

The cell is filled and installed on the experimental device. A temperature difference (thermal gradient) between the top and bottom of the cell of 20 °C is applied. Due to the Soret effect, the thermal gradient induces a concentration gradient which is responsible for the appearance of intense non-equilibrium fluctuations, on several temporal and spatial scales. The relaxation times provide information on the transport properties of the studied mixture.

To analyze these fluctuations, the team uses quantitative dynamic umbroscopy, based on the spectral study of image differences, and a very powerful image processing algorithm.

Parabolic Flight: A Long Preparation Time

These flights in weightlessness imply a long and meticulous preparation time, representing several months of full-time work for 4 people, because of the drastic safety rules on board.

Each element of the technical device, entirely manufactured by the team, must be able to resist nine times its own weight ("9g") in all directions. There must be no risk of explosion or cut. Potential human error must also be eliminated, therefore no electrical cables can be accidentally pulled out. But the primary risks are flying objects. A screw that is not tightened properly, for example, can easily be propelled into someone’s eye. A person on board is in charge of catching any floating object, sometimes even the researchers if they are not well attached.

The teams must provide Novespace, the flight operator (a subsidiary of CNES), with a document of nearly 100 pages detailing the electrical diagram of the device, the flammable products used and confirming that each element has been checked. Thus each screw must be tightened with the same force, and a small red mark is made on the varnish to be able to easily visualize when it starts to loosen. For some tests like waterproofing, videos must be sent.

As far as the physical preparation is concerned, it remains light: a medical file to be filled out and electrocardiograms to be performed, plus of course the sanitary rules of the Covid times.

During the flight campaign, it is necessary to spend two weeks in Mérignac: the first to prepare the aircraft, the second for the flights.

Parabolic Flight: How Does It Work?

To obtain the effect of weightlessness, the aircraft must fly a parabolic trajectory. The three pilots make the plane climb at about 45° then cut the engines and let it come down before going back on the throttle. The weightlessness lasts about twenty seconds (dark blue part on the diagram).

Parabolic Flights - A Brief History

1950  Idea launched by two German scientists who emigrated to the United States

1959  First parabolic flight in the United States

1961  Creation of the National Center for Space Studies (CNES) in France

1975  Creation of the European Space Agency

1984  First parabolic flight operated by the European Space Agency and CNES

1997  Novespace, a subsidiary of CNES, takes over the operation of the flights

2004  First parabolic flights open to the general public in the United States

2014  The Airbus A300 Zero-G is replaced by a better equipped A310


“CO2 Enhanced Storage” Research Chair Partners