Caroline during combined test for Ariane 6
Caroline Aussilhou, Launch System Engineer in the Ariane 6 architect team, part of the Space Transportation Directorate of ESA, seconded from France’s space agency CNES during the combined test loading test 2.1 at Europe's Spaceport in French Guiana.
On 24 October 2023, a team of CNES, ESA, Arianespace and ArianeGroup personnel, including Caroline, completed a full-scale wet rehearsal of the new Ariane 6 rocket that was fuelled and then drained of its fuel. The test lasted over 30 hours with three teams working in shifts of 10 hours each.
The goal was to increase the robustness of the launch system and to test emergency safety procedures with an interruption of the countdown from simulated anomalies.
The wet rehearsal – called combined test loading, abbreviated to CTLO2.1 – was the third time the Ariane 6 ground teams practiced a full launch countdown, after a first rehearsal on 18 July 2023 and a first ignition of the main engine on 5 September 2023. The CTLO2.1 test concentrated on system robustness and how well Ariane 6 and the teams handle situations at the edge of the operational parameters. This time, the operations were performed at night to test operations in cooler ambient temperatures, while the July and September tests were run in daylight.
Ariane 6 uses liquid oxygen and hydrogen as its fuel to power into space. These power-dense liquids are great fuels but need to be chilled to extreme temperatures below -250°C, making them hazardous to work with. At these temperatures the liquids will instantly expand if it heats up and can cause condensation or even ice on the rocket as it cools down in the surrounding tropically humid air.
Ariane 6 tanks hold 180 tonnes of propellant, which is why fuelling and then draining operations take so long – it took over seven hours to drain the liquid hydrogen from its tanks alone. Engineers are constantly adapting flow rate and monitoring temperatures, pressure in the tanks and pipes, and the ground systems underground pipelines that extend through hundreds of meters to transport the fuel to the rocket.
