The first Ariane 6 rocket to launch into space went through its last full ‘wet dress rehearsal’ at Europe’s Spaceport in French Guiana late last week, providing a sneak peek of what’s to come, stopping just a few seconds before engine ignition lift-off.
“The rocket, the launch pad and teams from ESA, CNES and ArianeGroup, all put in a great performance, and everything went smoothly."
Pier Domenico Resta, ESA
Similar to rehearsals carried out with a test rocket during combined test campaigns, this time the real flight model, its payloads, the launchpad and teams on the ground went through every step of launch operations; from pumping 180 tonnes of propellant – liquid oxygen and liquid hydrogen – into the waiting Ariane 6, the rollback of the mobile gantry, running all of the ground control software and more.
“The wet dress rehearsal is the very final milestone before launch,” says ESA’s Guy Pilchen, Ariane 6 launcher project manager “allowing teams to fine-tune the delicate operations required up until liftoff, using the real rocket’s actual flight hardware and software for the first time.”
One of the first steps was to roll back the colossal 90-meter (≈295 foot) tall Ariane 6 mobile gantry building about 400 feet away from the launch pad – the first moment the complete rocket stood free.
Pumping fuel into the Ariane 6 then took about 3.5 hours, as technicians at the control center first began by slowly cooling the pipes, valves, tanks and engines from the tropical temperatures in French Guiana of about 30 degrees Centigrade down to the super-chilled temperatures of the soon-incoming cryogenic fuels.
As much an art as engineering, the propellants used by Europe’s new rocket Ariane 6 are supercooled to –180°C for the oxygen and –230°C for the hydrogen fuel. At these temperatures, any humidity already in the pipes would immediately freeze and could lead to blocked valves. To avoid this, any hint of air or moisture from the atmosphere was flushed out of the system by the inert (unreactive) gas, nitrogen, before fueling began.
Once the tanks were full, teams continued topping them up as the liquid fuels would gradually boil away in the Sun. The rocket was subsequently drained of fuel in preparation for launch.
“The rocket, the launch pad and teams from ESA, CNES and ArianeGroup, all put in a great performance, and everything went smoothly – I couldn’t be prouder,” says ESA’s Pier Domenico Resta, “after all these years of preparation we are very close to launch.”
Data from the rehearsal is now being analyzed with results expected on 26 June which will confirm the launch date when Ariane 6 will go through the same process, except finally igniting and completing the last few seconds – taking off from Earth for the first time.