Ariane 6 upper stage visits ESA’s temple of boom

The upper stage for Europe’s newest rocket Ariane 6 passed its final tests at ESA’s facilities in the Netherlands last week, qualifying the upper stage for a launch on the most powerful, four-booster, variant of the Ariane 6 rocket.

Five tests at different acoustic levels confirmed the upper stage is ready for a launch on Ariane 6 with four boosters. The tests were carried out by ArianeGroup teams at ESTEC—ESA’s European Space Research and Technology Center in the Netherlands—using the upper stage hot-fire test model, which was used for the hot-fire test campaign at the German aerospace center, DLR, test site in Lampoldshausen, Germany, between 2022 and 2024.

Rocket launches are loud—even when standing several kilometers from the launch pad. The rocket itself takes the largest brunt of the acoustic attack and so the upper stage test model of Ariane 6 was subjected to the sounds of a rocket launch at Europe’s loudest sound system, the Large European Acoustic Facility (LEAF) at ESA’s technical heart in the Netherlands.

Ariane 6 is a rocket that can be launched in different configurations, including with two boosters or four, adapting its power to the destination required and the weight of the satellites it launches. Ariane 6’s inaugural flight was a perfect launch to orbit in July 2024 with two boosters. When Ariane 6 launches with four boosters from 2025 onward, they will create almost double the thrust at liftoff but the upper stage will also endure 60% more acoustic pressure.

Sitting at the top of the launcher, about 34 m above the rocket engines, the upper stage for Ariane 6, technically known as the Upper Propulsion Liquid Module (UPLM), was designed to withstand a four-booster launch, far exceeding the sound levels experienced on its first, two-booster, launch.

In advance of the full power of an Ariane 6 liftoff with four boosters, the UPLM has now been subjected to a week of tests reenacting the acoustic vibrations it will endure. More than 6 meters tall, the upper stage is the heaviest and largest object ever to be tested inside LEAF.

The upper stage was tested upright as it would be on liftoff in the LEAF. Its propellant tanks that are filled with liquid hydrogen and oxygen on flight were filled with water and glycerine to increase the accuracy of the test. Two hundred sensors recorded the structure’s reaction to the acoustic waves. The black covers used for testing recreated the intertank structures and acoustic protection provided by the main stage of the rocket on the launch pad.