Europe has just accomplished the primary successful hot-fire test of its reusable Prometheus engine integrated with the Themis first-stage demonstrator on the ArianeGroup site in Vernon, France. The new-fire test consisted of Prometheus performing a 12-second burn on the Themis demonstrator on June 22, 2023.
The 2 components are a part of a broader European launch program, called Ariane Next, which is targeted on developing a fleet of reusable rockets that can enter into service within the 2030s. This system is a joint effort between the European Space Agency (ESA) and the French Space Agency (CNES) with ArianeGroup because the prime contractor.
Initial Testing Begins
The Prometheus engine is powered by oxygen and methane, but to align with ArianeGroup’s environmental innovation endeavors, the primary hot-fire test included a bio-methane fuel. ArianeGroup said in a statement that carrying out these tests with Prometheus and Themis indicated the behavior of the components operating together inside an prolonged mission profile.
“Yesterday’s test reached all of the test objectives (operating points, duration) and is a vital milestone on the long approach to an operational product, confirming a viable product,” Jérôme Breteau, Head of the Future Space Transportation systems at ESA, told NSF.
“Further activities are planned to enhance and complete the engine. For instance, the engine configuration doesn’t incorporate nozzle extension, and a few combustion element manufacturing technologies are developed in parallel and never yet embarked.”
Prometheus engine testing is scheduled to proceed at the top of 2023 on the German Aerospace Center (DLR) test bench in Lampoldshausen, Germany.
![](https://www.nasaspaceflight.com/wp-content/uploads/2023/06/Prometheus_and_Themis_test_ArianeGroup_1.png)
Prometheus and Themis hot-fire test lasted 12 seconds. (Credit: ArianeGroup)
Ariane Next – Europe’s Future Fleet
Ariane Next forms the constructing blocks of Europe’s ambitions to develop reusable launch vehicles, and Themis and Prometheus are among the first concepts to be tested and developed.
Between 2015 and 2017, CNES and ArianeGroup conceived the concept of Prometheus, a reusable rocket engine powered by oxygen and methane. Then, following ESA’s Space19+ Ministerial Conference in 2019, which focused on proposing ‘next generation’ launch technologies, Themis was born.
One among the fundamental differences between Prometheus in comparison with the oxygen and hydrogen-powered Vulcain engine that powered the Ariane 5 — and Vulcain 2.1 that can power the Ariane 6 — is that Prometheus will burn oxygen and methane. The transition to methane is basically since it is taken into account cheaper, easier to handle, and keeps liquid at the same temperature as oxygen.
In response to CNES, the engine will likely be reusable as much as five times and may deliver variable thrusts of as much as 100 tonnes. Although the engine will provide lower thrust than the Vulcain 2.1, which delivers 130 tonnes in a vacuum, methane is six times denser than hydrogen and can enable “more compact” rocket stages which might be easier to get better. The Prometheus is re-ignitable, which makes it suitable for core, booster, and upper-stage application. The engine could also function a precursor for Vulcain 2.1 improvements, Breteau said.
🔥We just successfully accomplished the primary Hot Firing Test campaign of THEMIS a totally reusable space launcher stage in Vernon! https://t.co/LtTJ1xV9I1 @esa @cnes #RocketsMakers #SpaceEnablers #SIAE #lebourget #aerospace #ParisAirShow #Themis #ArianeGroup pic.twitter.com/8QHSTKu1EE
— ArianeGroup (@ArianeGroup) June 23, 2023
“From an economic perspective, Prometheus is aiming to cut back production costs tenfold with respect to the Vulcain engine—which has a unit cost of €1 million—due to a distinct architecture, extensive use of 3D printing, and a production rate of fifty engines per 12 months,” CNES says.
“From a schedule perspective, the goal is to equip the lower (with the Themis demonstrator) and upper stages of Europe’s future range of launchers—from micro-launchers to Ariane Next—by 2030.”
Marking the primary real progress for Prometheus, the engine accomplished its first successful thrust chamber ignition in November 2022 in preparation for future hot-fire tests.
For Themis, ESA began its first step in developing the reusable rocket stage in December 2020, after inking a contract with ArianeGroup for €33 million to start the ‘Themis Initial Phase.’ ESA has said its aim with this system is to finish tests early on in the event cycle through an “agile and cost-driven” approach.
In response to ESA, the ‘Themis Initial Phase’ follows a project timeline from 2020 to 2025. The initial timeline estimated that in 2020, basic stage testing composed of tank filling and ground support equipment tests can be accomplished, followed by Prometheus engine testing in 2021. In 2022, low-altitude hop tests for the Themis demonstrator were expected to occur, followed by initial flight and loop tests in 2023 and 2024 from the Esrange Space Center in Kiruna, Sweden. In 2025, ESA expects to perform a full flight envelope test.
![](https://www.nasaspaceflight.com/wp-content/uploads/2023/06/Themis_demonstrations_pillars.jpg)
Themis reusable rocket timeline. (Credit: CNES)
This series of hop tests will likely be like SpaceX’s Grasshopper and Falcon 9R-Dev demonstrator vehicles, which performed smaller scale vertical-takeoff-and-landings and provided insight into the performance of the boosters during a controlled landing.
While Themis accomplished tanking tests in December 2021, the most recent hot-fire test is barely behind schedule in keeping with the project timeline, but Breteau asserts Prometheus will likely be application-ready by the top of 2025.
“Prometheus is an agile and success-oriented demonstrator programme, and solving technical issues, while inherent to those cutting-edge activities, take a while and can’t be planned upfront, and is liable for some delays,” Jérôme Breteau said.
“The programme has been also impacted by the commonality of means and teams with Ariane 6, corresponding to P5 test bench.”
The subsequent test campaign for Themis in Sweden is an element of a European Union (EU) Horizon Europe program, called SALTO (reusable strategic space launcher technologies and operations). In July 2022, ArianeGroup was chosen by the EU to oversee each the SALTO project and the ENLIGHTEN (European iNitiative for Low price, Modern & Green High Thrust Engine) project, which is designed to develop and produce reusable engines following on from Prometheus.
Europe’s Steps Towards Sustainable Space
With Europe’s plans to change into carbon neutral by 2050, ESA has also taken steps to cut back its carbon footprint, and the reusability of rocket stages has been hailed as a powerful approach to reducing the environmental impacts of the launch industry. While there remains to be possibly a decade until Ariane Next vehicles enter into service, the technology will provide Europe with the obligatory competition between other reusable options.
Europe’s space industry can be taking a look at other ways to support a sustainable sector. In 2020, ESA and CNES announced the agencies would work together to change to renewable energy sources on the Centre Spatial Guyanais (CSG) in Kourou, French Guiana. The energy transition would cut costs and reduce reliance on the French Guiana grid. ESA announced it will construct solar fields and two biomass units, which could save as much as 50 GWh per 12 months, reducing the carbon footprint by about 45,000 tonnes of carbon dioxide (CO2).
![](https://www.nasaspaceflight.com/wp-content/uploads/2023/06/Prometheus_and_Themis_test_ArianeGroup_2.png)
The engine burned oxygen and bio-methane. (Credit: ArianeGroup)
In February 2023, France began lobbying the EU for subsidies that may enable the nation to construct biomass power plants in French Guiana, despite strong opposition from environmental organizations.
Most recently, ESA announced a Zero Debris Charter initiative through the Paris Air Show, supported by Airbus Defence and Space, OHB, and Thales Alenia Space. The initiative is targeted on encouraging member states to implement a “Zero Debris approach for its missions.”
ESA and CNES have also worked on other reusability projects, including FROG and CALLISTO. FROG was a small demonstrator mission to check the vertical landing of a rocket stage. The two.5-meter rocket performed a series of test flights in 2019, mostly focused on testing GNC (Guidance, Navigation, and Control) software.
CALLISTO (Cooperative Motion Resulting in Launcher Innovation in Stage Toss-Back Operations) is a fully-reusable, 15-meter-high rocket that is about to fly as a demonstrator rocket, mostly focused on testing the technologies of returning a launcher to Earth. The mission is at the side of the Japan Aerospace Exploration Agency (JAXA) and the German space agency (DLR) and was presupposed to fly in 2022, but there have been no further updates.