Themis reusable rocket demonstrator completes second wet dress rehearsal at Esrange, Sweden
The European Space Agency said ArianeGroup and SSC Space completed a second wet dress rehearsal of the Themis reusable rocket demonstrator on 29 September, using liquid nitrogen cooled to around -200°C instead of propellant. The test also exercised robotic ground systems meant to locate, connect to and drain the vehicle after landing. The EU-funded SALTO project, which has a budget of €42.8 million, will fund two low-altitude hop tests, the first reaching up to 100 metres.
Bottom line — Teams are now defining a window for the next test, and at least one more rehearsal is expected before any hot-fire of the Prometheus engine.
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ESA's own account of the first rehearsal, on 23 July, described it as practising countdown and post-flight procedures, with liquid nitrogen chosen because it is not flammable or explosive.
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ArianeGroup said the rehearsal refined the 'synchronized sequence', the final automatic phase of the countdown, and used a fleet of robots to secure the vehicle after landing.
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Spacechannel.eu reported that the first rehearsal was announced a week after it took place, and that it was the most significant public milestone since T1H was erected on its landing legs in September 2025.
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Spacechannel.eu quoted ArianeGroup saying the demonstrator is 28 metres tall, and quoted a January 2026 ESA comment that the team was 'waiting for spring' while Kiruna lay under snow.
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The SALTO consortium is coordinated by ArianeGroup and brings together 25 partners from 12 EU countries, with the project managed by the EU executive agency HaDEA.