Toulouse, June 10, 2025 – At the 55th International Paris Air Show, Ascendance, a European pioneer in decarbonized aviation, announced the launch of the STERNA Hybrid Pack, its proprietary hybrid-electric propulsion system. This modular solution natively integrates a propulsion battery designed specifically for hybrid-electric aviation, an energy management system, and an electrical distribution unit. The system is engineered to combine performance, energy efficiency, and compliance with stringent aviation certification requirements.
To develop this high-performance battery, Ascendance partnered with EXOES, a leading French specialist in thermal systems and batteries for mobility.
This strategic partnership is based on a shared vision to accelerate the industrialization of certifiable, hybrid-electric propulsion solutions manufactured in France that meet the demanding standards of the aerospace and defense sectors.
Hybrid-Electric: The Pioneering Choice for Decarbonizing Aviation
Since 2018, Ascendance has been convinced that hybrid-electric technology is the most realistic and effective way to reduce aviation’s carbon footprint in the short and medium term. Unlike all-electric solutions, which are limited by range and charging constraints, and unlike hydrogen, which is not yet mature, hybrid systems can reduce emissions while maintaining operational flexibility.
When combined with sustainable aviation fuels (SAFs), hybridization optimizes environmental performance by reducing SAF consumption and lowering operating costs for operators while easing pressure on alternative fuel production. This pragmatic solution is designed for a credible transition.
EXOES, a committed player in decarbonizing mobility, views hybrid-electric aviation as a strategic means of combining safety, energy performance, and emissions reduction while creating new industrial opportunities in France and abroad.
Ascendance and EXOES have formed a key industrial partnership focused on performance.
Leveraging their respective areas of expertise, Ascendance and EXOES have joined forces to design and produce batteries tailored specifically for the needs of hybrid-electric aviation.
These unique batteries power the STERNA Hybrid Pack, which offers a comprehensive hybrid-electric propulsion solution. This partnership is a significant milestone for Ascendance, demonstrating its ability to produce and industrialize hybrid-electric propulsion systems in France.
Ascendance is responsible for the system architecture, the Hybrid Energy Management System, onboard control and safety devices, and the Hybrid Core Unit, ensuring performance and compliance with aviation certification standards.
EXOES contributes cutting-edge expertise in cell assembly, advanced thermal management, and extreme testing to guarantee robustness, reliability, and compliance with aviation requirements.
“This partnership with EXOES demonstrates the consolidation of our hybridization strategy. Since Ascendance’s founding in 2018, we have developed and tested our hybrid technologies in order to build a decarbonized, certifiable hybrid aviation industry. The Hybrid Pack is not a transitional technology; it is the foundation of a new generation of propulsion.”
— Jean-Christophe Lambert, CEO of Ascendance
“Since 2017, EXOES has specialized in designing and manufacturing high-performance batteries with enhanced safety. Aerospace and defense are our top-priority markets. This partnership with Ascendance has already attracted our first customers, and we are eager to accelerate the market launch of our joint products and services.”
— Arnaud Desrentes, CEO of EXOES
An integrated system ready for multiple markets!
Unveiled exclusively at the Paris Air Show, the STERNA Hybrid Pack, owned by Ascendance, represents a major technological breakthrough. It is designed to meet the operational, economic, and environmental needs of tomorrow’s aviation.
It is modular and compact and can be easily integrated into a wide range of platforms, including VTOLs like ATEA, long-range drones, light helicopters, and regional aircraft, to boost range, reduce emissions, and enable a gradual transition to cleaner aviation.
Designed for constrained environments, the STERNA Hybrid Pack offers dual charging capabilities:
• In-flight for time savings and total independence from ground infrastructure
• On the ground, to leverage existing networks when available
This operational flexibility enables a wide range of real-world use cases, such as medical or surveillance missions in remote areas, regional connections on short runways, and logistics or tourism services in non-electrified regions. These markets all seek immediately deployable, certifiable solutions.
About Ascendance
Founded in 2018 by Jean-Christophe Lambert, Thibault Baldivia, Clément Dinel and Benoît Ferran, Ascendance is an industrial startup with a mission to decarbonize aviation. Founded in 2020 in the heart of Toulouse, the European aeronautics capital, it develops and commercializes two solutions: an innovative hybrid-electric propulsion system called STERNA and a vertical take-off and landing (VTOL) aircraft equipped with this technology called ATEA.
Press Contacts – Kalamari Agency – Kelly Wright / Natacha Favry – ascendance@kalamari.agency
About EXOES
Founded in 2009 in Gradignan by Rémi Daccord and Arnaud Desrentes, EXOES specializes in advanced battery systems and thermal management solutions. The company brings deep expertise in the design, manufacturing, and testing of high-performance batteries, optimizing energy storage, thermal efficiency, and safety. Active in several sectors—including automotive, rail, defense, and aerospace—EXOES stands out for its mastery of cooling technologies, particularly with E-Mersiv, its patented immersion cooling system. This technology has been successfully applied in the development and validation of numerous battery concepts designed for fast charging and enhanced safety.