Ariane 6 Lightweight Upper Stage, Future Upgrades Cancelled
For several years, ArianeGroup, the builders of Europe’s Ariane 6 rocket, have been working on a future upgrade known as the Innovative Carbon Ariane Upper Stage, or ICARUS. Preceded by a technology demonstrator named Phoebus, it aimed to create a new upper stage for Ariane 6 with tanks made out of carbon composite. This would significantly reduce the mass of the stage and enable greater payloads to Low-Earth Orbit, the lunar surface, and interplanetary destinations. However, evidence now indicates that this upgrade has been cancelled following the 2025 ESA Ministerial Council.
At the 2026 International Planetary Probe Workshop, an annual gathering of US and European planetary scientists, engineers, and mission members, an update on the European Space Agency’s L4 mission to orbit and land on Enceladus revealed that the mission had to be re-architected due to a launch vehicle change. The project had been informed that Ariane 6 Block 2 would be the last major version of the rocket, ruling out a more powerful version known as “Ariane 64 Evo” that they had planned to use. Block 2, which has been partially implemented for Arianespace’s early launches of Amazon’s Leo constellation, consists of upgraded P160C solid rocket boosters, a higher-thrust version of the Vinci upper stage engine, and various first stage improvements.
According to an internal ESA document reviewed by Space Scout, Evo is the same as Ariane 6 Block 3, which includes the ICARUS upper stage. However, Block 3’s development would likely require a greenlight and funding allocations at ESA’s triennial Ministerial Council, the meeting of ministers from all ESA Member States that set the agency’s budget and priorities for the next three years. The 2025 Ministerial Council (also known as CM25) significantly underfunded the Human and Robotic Exploration directorate. A large portion of Block 3’s use-case was in supporting deep space exploration, such as increasing payload for the agency’s Argonaut lunar lander to 1,800 kg. With significant setbacks to its primary user, and virtually all existing near to medium term customers being satisfied by Block 1 or Block 2, it is likely that this underfunding led to the shelving of Block 3, and with it ICARUS.
Another contributing factor could be Arianespace’s recent calls for funding to increase Ariane 6’s launch cadence in response to constellations such as Amazon Leo and future systems such as the European Commission’s IRIS2 and the German military’s independent system. Subsequent to CM25, Phoebus has proceeded with its testing campaign but it is unclear what the eventual fate of it will be, or if ArianeGroup will try to continue further upgrades at some point in the future.
Space Scout has reached out to ArianeGroup for comment.
