Source | MT Aerospace AG

The Cost-Optimized Sandwich Technology for Large-scale Structures (COSTELAS) project has reached a new milestone in the development of a more efficient, higher-performing Ariane 6 upper stage, MT Aerospace AG (Augsburg, Germany) reports. Since passing critical design review in September 2024, the company’s carbon fiber-reinforced polymer (CFRP) composite intertank structure also passed preliminary design review in December 2025.

With this achievement, MT Aerospace confirms its capability and readiness to take next steps toward high-performance and cost-efficient composite upper stages for Europe’s launch vehicles. The upper stage tank’s segmented sandwich panel architecture has been achieved through automated fiber placement (AFP) and one-shot curing for enhanced industrial efficiency. MT Aerospace reports significant mass reduction — translating to a 1:1 payload increase.

Learn more about the Ariane 6 rocket.

Since 2018, the ESA-funded Launchers Preparatory Program (FLPP) has been working to optimize the Ariane 6 rocket’s upper stage, and thus reusable launcher systems generally, using cutting-edge technologies (read “PHOEBUS project makes progress on CFRP liquid oxygen, hydrogen upper stage tanks”). COSTELAS is actively aiming for this goal through its use of carbon fiber composites. 

COSTELAS’ 2 × 3-meter composite structure passed critical design review in September 2024. Partner Applus+ IMA (Dresden, Germany) handled a series of static tests on the CFRP sandwich structures, with positive results.