Matthieu Sacher and Laurent Mortier, lecturers and researchers at ENSTA and members of CIMO and IngéBlue, are working on reducing the impact of maritime transport and marine observatories. They will present a summary of their work at the international conference “One Ocean Science Congress” from June 2 to 6.
There is only one ocean
An essential resource for human prosperity and well-being, the ocean plays a crucial role in regulating the climate and sustaining the livelihoods of three billion people, the vast majority of whom live in developing countries.
Climate change, overfishing, pollution, and conflicts over use are all threats to the ocean. It urgently needs decisive, rapid, and unified efforts to address its critical situation and maximize the solutions it offers.
Preserving the ocean, a key issue at the OOSC scientific congress and the United Nations Ocean Conference UNOC3
The third United Nations Ocean Conference (UNOC3) will be held in Nice from June 9 to 13, 2025. All stakeholders—scientists, the business community, associations, and political decision-makers—will come together to initiate and implement concrete actions for the “conservation and sustainable use of marine and coastal ecosystems” in line with SDG 14, the UN's 14th Sustainable Development Goal, which is the least funded of all the SDGs.
In the run-up to and in support of this event, the CNRS and Ifremer, together with their partners, including ENSTA, have been tasked with organizing the One Ocean Science Congress (OOSC) in Nice from June 3 to 6, 2025, dedicated to science, in order to provide heads of state and government, as well as society as a whole, with comprehensive scientific information on the health of the ocean and its future trajectory. Science-based decisions should enable the conservation and sustainable use of the ocean, optimize the solutions it offers, and safeguard the services and benefits it provides to humanity.
Two ENSTA researchers advocate multidisciplinary and collaborative research to quickly achieve significant goals
The Interdisciplinary Center for Marine and Ocean Research (CIMO), Ifremer, CNRS, ENSTA and the schools of the Institut Polytechnique de Paris are conducting multidisciplinary research to preserve the ocean, measure its changes, reduce the carbon footprint of maritime transport and produce sustainable marine energy by networking more than 200 researchers from the six engineering schools of IP Paris and national research organizations, primarily Ifremer and CNRS.
ENSTA is also the leader of the French maritime engineering institute “IngéBlue,” which brings together 15 institutions (schools, universities, and public expert organizations).
Matthieu Sacher and Laurent Mortier are lecturers and researchers at ENSTA and members of CIMO and IngéBlue. At the ENSTA campuses in Brest and Paris-Saclay, their research focuses on reducing the impact of maritime transport and marine observatories.
Matthieu, Laurent, what are the objectives of your presentations at the OOSC?
Matthieu Sacher (lecturer and researcher in mechanical sciences, hydrodynamics, and marine engineering, teaching naval architecture. He will be speaking at the OOSC on June 5):
“The dynamism of multidisciplinary scientific networks is a prerequisite for effective applied research that will more quickly deliver the knowledge and innovation capabilities expected. I am taking advantage of the OOSC to convey this message and illustrate it with a few research projects we are conducting with our colleagues from other engineering schools and research laboratories for the decarbonization of maritime transport.”
Laurent Mortier (lecturer and researcher in oceanography, teaching ocean dynamics and playing an important role in the development of the global ocean observation system):
"In situ ocean observation relies on a large number of players, including researchers with diverse motivations, and coordinating their activities remains a complex and costly issue. Halfway through the Decade of Ocean Science, the OOSC provides an appropriate framework for advancing the issue of research infrastructure. Their role in consolidating the ocean observation system and ensuring its sustainability is now better recognized, but raises the issue of resource sharing and coordination with operational agencies. A session of the OOSC is devoted to this issue, as is a town hall meeting, in which my European colleagues and I will give presentations, and I will moderate.
Matthieu, your work aims to model the performance conditions of new ship propulsion systems in order to reduce fuel consumption and environmental impacts. Who are you working with on this and how is the team progressing?
These projects receive French public funding through the Defense Innovation Agency, as their applications concern both maritime transport and naval defense platforms.
We obtained this funding by bringing together teams from ENSTA (IRDL research laboratory, CNRS UMR), the Naval Academy, Ifremer, and ENSM. We are all part of the IngéBlue network, which facilitated our response to the AID call for projects. Wind propulsion is a promising solution for decarbonizing maritime transport.
However, its integration into ships poses challenges in terms of maneuverability and steering. At the ENSTA mechanics laboratory, we are developing physical models to evaluate and optimize the energy performance of ships equipped with rigid or semi-rigid sails, kite wings, or rotors. These models will be integrated into a 3D simulator by the ENSM to train sailors.
The addition of sails changes the behavior of the ship, influencing the hull and the propulsion chain. The choice of shipping routes is also more dependent on weather conditions, requiring new routing systems. Since January 2024, the SOMOS project, led by ENSTA and ENSM, has been working to understand and optimize these interactions. We are developing physical models to simulate the complex forces and interactions between the sail propulsion system and the ship.
A navigation simulator, developed by ENSM, will integrate the physical models to assess the operational impacts of sailing systems. Fuel consumption estimates, routing algorithms, and international navigation rules will be tested using human-machine interfaces. Expertise in CFD modeling ensures the optimization of the ship's aerohydrodynamic coupling.
These IT tools will be available on an online platform accessible to academics and industry players to promote collaborative innovation.
Matthieu, your research also focuses on vertical axis ship propellers (SHIVA and SAWASP projects). Fantasy or reality, how can the performance of such an innovation be guaranteed?
Measuring and predicting the conditions for the success of such an innovation is precisely the role of the research projects we are conducting.
The SHIVA project, funded by the AID and led by ENSTA, the École Navale and Ifremer, aims to optimize the performance of an all-electric vertical axis marine propulsion system. It is capable of generating 360° steerable thrust using blades that move around two axes, thereby partially or totally compensating for the drift effect that slows down the ship's forward motion. Multi-model optimization approaches aim to maximize propulsive efficiency. This propulsion system is promising for wind-assisted ships.
Unlike a conventional propeller optimized for a single operating point (a given speed and rpm), this all-electric propulsion system with vertical adjustable blades allows the thrust to be continuously adjusted according to the sailing conditions. This allows for optimal hydrodynamic efficiency, even under sail, which significantly alters the balance and operating point of the propulsion system.
It is with this in mind that ENSTA, the École Navale, Ifremer, and Georgia Tech Europe have launched the SAWASP project, with financial support from the Carnot ARTS and MERS institutes. The objective is to study the optimal aerodynamic coupling of a hybrid ship demonstrator combining a rigid sail and two all-electric vertical propellers. This demonstrator, a 6-meter-long ship, is currently under development.
An initial thesis has already optimized the propeller's hydrodynamic performance. Tank tests, which will be carried out at Ifremer's facilities, are scheduled for November 2025. The first sea trials, in Brest harbor, are scheduled for summer 2026.
Laurent, what are the main scientific guidelines and objectives to be achieved in terms of ocean observation, from the deep sea to the coastline?
In many ways, ocean observation has shaped the current organization of climate observation.
While observing in order to discover—the exploration of the unknown always draws on the same forces—and understand phenomena, data must be collected in a very systematic way to help societies and economies cope with hazards, climate change, and the necessary exploitation and preservation of resources.
From the deep sea—where there is much talk today about mineral exploitation—to the coastlines—where half of the world's population lives within a few dozen kilometers of the sea and the EEZ concentrates a very large part of the resources exploited— in-situ observation, supplemented by the integrated but partial view provided by satellites, enables us to understand the extremely complex interactions between these environments, from physical processes to marine ecosystems, which have always fascinated mathematicians. But it also makes it possible to create indicators that can be used in maritime policy, to manage fishing permits, to combat illegal activities, etc.
The goal today is to stabilize the operation of the many ocean observation systems, coordinate them better, and above all improve their efficiency, as they are very costly (or relatively modest in relation to the benefits of these observations and knowledge).
Laurent, how do you address these issues in your work as a teacher and researcher?
As a teacher, I first tried to convey the absolute necessity of observation, whereas modeling—an area in which our engineering schools excel—has tended to overshadow it somewhat, at least in France.
Every year, we take students from the ENSTA campus in Paris-Saclay on oceanographic expeditions in the Mediterranean, and they come back transformed. This is also one of the areas of expertise (hydrography and oceanography, category A) at the ENSTA campus in Brest.
For the OOSC and UNOC, ECOPs, as they are known – Early Career Ocean Professionals – are an absolute priority. But it's true that for almost 20 years, I have been primarily an activist for research infrastructure.
EU funding programs have stimulated the construction of an ecosystem of infrastructures that play a central role in Europe, particularly in organizing marine observation, and which, in a domino effect, could be said to also structure organization at the national level and, increasingly, at the global level.
I started with the issue of automated observation by drones. This is an important trend, because observation by research vessels has many limitations, not to mention the necessary decarbonization that is prompting us to review the complementarity of observation methods.
