Airbus Netherlands has delivered the first lightweight Vulcain Aft Bay for Ariane 6 as part of the rocket’s Block 2 upgrades. The total weight reduction, however, appears to be more modest than originally anticipated.
In a 21 October LinkedIn post, Airbus Netherlands President Rob Postma announced that the upgraded structure, designated Flight Model 16 (FM16), was on its way to ArianeGroup in France via Rotterdam. According to Postma, the upgrade is expected to be launched for the first time aboard an Ariane 6 mission in 2027.
The Vulcain Aft Bay is a structural assembly fixed to the base of Ariane 6’s main stage. It supports the Vulcain 2.1 rocket engine and transfers the thrust generated by the engine to the rocket’s main structure. The assembly currently weighs approximately five tonnes.
Postma explained that the redesigned structure is 55 millimetres shorter than its predecessor and 400 kilograms lighter. This appears to be half the weight reduction the company originally expected to achieve.
In July 2024, the Netherlands Space Office reported that the upgraded aft bay would be 800 kg lighter, citing Airbus Netherlands Director of Strategy, Sales and Business Development Frank Meiboom. The agency also identified FM16 as the first flight model expected to incorporate the changes.
By 2025, however, that figure appeared to have already been revised downwards. An article in Leonardo Times, an aerospace magazine published by students at Delft University of Technology, reported that engineers had achieved a weight reduction of more than 550 kg following a visit to the Airbus Netherlands production facility.
Postma’s announcement did not address the discrepancy between the earlier figures and the final stated weight reduction.
The lighter Vulcain Aft Bay is part of the Ariane 6 Block 2 evolution, which also includes the more powerful P160C solid rocket boosters. The upgraded boosters were first used aboard an Ariane 64 rocket in June 2026.
In August, European Spaceflight reported that ESA had identified the lighter Vulcain Aft Bay as one of the remaining upgrades intended to improve Ariane 6’s performance and competitiveness. While another set of upgrades, known as Block 3, had been expected to follow, ESA has since confirmed that it would not pursue them, saying there was “no programme need or justification” for doing so.
