The European Space Agency (ESA) and ArianeGroup have confirmed that Prometheus engine tests conducted in Lampoldshausen in October were carried out independently of preparations for the long-delayed inaugural flight of the Themis reusable booster demonstrator.
In a 6 November press release, ArianeGroup announced that it had completed a series of hot-fire tests of the latest iteration of the Prometheus rocket engine at DLR’s P5 test bench in Lampoldshausen on 29 October.
“The successful hot fire test conducted on [the] P5 test bench in Lampoldshausen increases engine operations maturity,” an ArianeGroup spokesperson told European Spaceflight. “The tests were conducted independently of Themis flight preparations.”
An ESA spokesperson added that the operating profile for Themis’s inaugural flight had already been tested using the same engine configuration as the one currently mounted on the demonstrator.
One of the objectives of the late-October test campaign was to validate the performance of a new combustion chamber produced using a Cold Gas Spray additive manufacturing process. The process is intended to allow the engines to be produced faster and more cheaply than with traditional manufacturing methods.
In its 6 November press release announcing the completion of the latest Prometheus hot-fire test campaign, ArianeGroup revealed that it is now preparing an improved version of the Prometheus engine, known as Mark 2, for a forthcoming test campaign.
This upgraded version of the engine will power a subsequent variant of the Themis reusable rocket demonstrator known as Themis 1E. The vehicle will feature upgraded structures and propellant tanks, allowing it to undertake longer flights at higher altitudes.
Themis remains grounded
During an ESA press conference in January 2026, Toni Tolker-Nielsen, then acting Director of Space Transportation, explained that teams were “waiting for spring” to conduct Themis’s inaugural flight test from the Esrange Space Centre in Sweden. ESA Director General Josef Aschbacher added that the agency was targeting the first quarter of 2026 for the flight.
Spring came and went, as did summer and autumn. Now, with winter returning to northern Sweden, Themis remains stuck on the launchpad as snow once again threatens to bring testing at Esrange to a halt.
Speaking at an ESA press conference on 22 October, the new Director of Space Transportation, Géraldine Naja, acknowledged uncertainty over whether the first hop could be completed before the end of 2026. She explained that ArianeGroup and SSC Space, the operator of the Esrange facility, would decide by the end of November whether to attempt an inaugural flight this year.
