ArianeGroup has completed a wet dress rehearsal of the Themis reusable booster demonstrator at the Esrange Space Centre in Sweden, providing the first substantive update on the vehicle’s test campaign in more than ten months.
The rehearsal was conducted on 23 July by teams from ArianeGroup and SSC Space, the commercial entity that manages the Esrange Space Centre. The milestone was announced by ArianeGroup on 30 July, a full week after it occurred.
During the test, the 28-metre-tall demonstrator underwent a simulated pre-flight sequence under cryogenic conditions. According to ArianeGroup, the simulated operations were conducted over one day and included preparations for both the vehicle and launch pad, the countdown itself, and procedures to make the site safe following a simulated flight and recovery.
The test did not use the liquid oxygen and liquid methane that will be used during powered testing. Instead, liquid nitrogen was circulated through the vehicle’s cryogenic tanks and lines. The liquid nitrogen reproduced temperatures and pressures representative of flight operations, with temperatures falling as low as -200°C.
The wet dress rehearsal represents the most significant publicly announced milestone in the Themis test campaign since September 2025, when the T1H demonstrator was erected on its four landing legs at Esrange, marking the start of combined testing. In January 2026, then-director of ESA’s space transportation programme explained that Kiruna, where Esrange is located, was under snow and that they were “waiting for spring.”
It is not yet clear when the next milestone in the test campaign will take place. ArianeGroup said the rehearsal provided data that will support the next stages of the campaign as Themis moves towards its first low-altitude hop test. “The teams are now working to define the window for the next test,” the company said.
