ArianeGroup has completed a wet dress rehearsal of its Themis reusable booster demonstrator at the Esrange Space Centre in Sweden, marking a key milestone in the vehicle’s ongoing test campaign.
The rehearsal was carried out on July 23 by teams from ArianeGroup and SSC Space, the operator of Esrange Space Centre, with the company announcing the achievement one week later.
Themis Advances Toward Hop Testing
The test simulated a full pre-launch sequence for the 28-meter-tall demonstrator under cryogenic conditions.
According to ArianeGroup, the one-day exercise included preparations for both the launch vehicle and launch pad, a simulated countdown, and post-flight procedures designed to secure the site following a mock recovery operation.
Rather than using the liquid oxygen and liquid methane that will eventually power the vehicle, engineers circulated liquid nitrogen through the booster’s cryogenic tanks and propellant lines.
The liquid nitrogen recreated operating temperatures and pressures expected during flight, with temperatures reaching approximately -200 degrees Celsius.
Test Campaign Continues
The wet dress rehearsal represents the most significant publicly announced milestone in the Themis program since September 2025, when the T1H demonstrator was erected on its landing legs at Esrange, marking the beginning of integrated testing.
Earlier this year, officials from the European Space Agency noted that winter conditions at Kiruna, where Esrange is located, had delayed parts of the campaign.
ArianeGroup said data collected during the rehearsal will support the next phase of testing as the demonstrator moves toward its first low-altitude hop flight.
“The teams are now working to define the window for the next test,” the company said.
The company has not disclosed a timetable for the upcoming hop test.
