Connova Group Composite Landing Legs Carry Full Load in Themis Reusable Rocket Rehearsal

Source | ESA, SSC Space – Mattias Forsberg

On July 23, the European Space Agency’s (ESA, Paris, France) Themis T1H demonstrator completed its first wet dress rehearsal at Esrange Space Center in northern Sweden — the first time that four carbon fiber-reinforced polymer (CFRP) landing legs built by Connova Group (Villmergen, Switzerland) carried the full weight of a fueled stage under operational conditions. ArianeGroup (Paris, France) and the Swedish Space Corp. (SSC, Solna, Sweden) ran a complete countdown and post-flight sequence on the pad, loading the stage with several tonnes of liquid nitrogen chilled to -200°C, which is close to the real propellants in temperature and density, but neither flammable nor explosive.

Themis is Europe’s reusable launcher demonstrator. Initiated by ESA and developed under ArianeGroup leadership, the flight campaign runs within the EU-funded SALTO project with 25 partners from 12 countries. Its purpose is to show, for the first time in Europe, that a full-scale launcher stage can lift off vertically and land again. Standing on its legs, the T1H configuration (“Themis-1 engine Hop”) measures 30 meters tall and 3.5 meters in diameter, powered by the reignitable, throttleable liquid oxygen/methane Prometheus engine. Connova Group produced the four landing legs as manufacturing partner to Almatech SA (Lausanne, Switzerland), a space engineering firm.

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Why the use of composites? On a reusable stage, landing legs contribute nothing during ascent — every kilogram saved goes directly to payload capacity and cost per launch. The Themis system, therefore, pairs filament-wound CFRP tubes with high-precision machined aluminum and steel fittings. Against an all-metal solution, the hybrid approach saves roughly 25-30% in mass.

The CFRP tubes were filament wound at Connova’s German site in Klipphausen near Dresden, while the metal fittings were machined in Villmergen. The components were joined by match drilling — holes driven through CFRP/steel/aluminum stack-ups at micrometer-level precision, so that load introduction sits exactly right at every interface.

According to Connova, wall thicknesses in the centimeter range pushed filament winding to the limits of the process. Added to that was the tight carbon fiber supply situation of 2022, a final manufacturing window of only a few weeks and the requirement to hit industrial New Space cost targets rather than classic institutional space budgets. First components shipped in Q3 2022, and flight hardware was delivered between January and May 2023. That exact configuration is what stands on the pad today — no modifications have been required since.

Next milestone: The hop test

The next step is the hop — a short vertical flight followed by a controlled landing — which will deliver final validation of the legs’ maximum design loads. The touchdown maneuver is decisive: At the planned deceleration, loads stay inside the design envelope, while an excessive sink rate at touchdown would abruptly overload the structure. It is precisely this load case the legs were sized for, with reserves. Series production is currently targeted for 2027/28, subject to the results of the flight campaign.

“If the test succeeds, Europe becomes the third player worldwide, after the U.S. and China, with reusable launcher technology,” says Thomas Leschik, managing director of Connova Deutschland GmbH. “That puts Connova Group not only in the current Ariane 6 supply chain, but already gives us a CFRP foot in the future of the European space industry.”