Hubbry Logo
Prometheus (rocket engine)Prometheus (rocket engine)Main
Open search
Prometheus (rocket engine)
Community hub
Prometheus (rocket engine)
logo
8 pages, 0 posts
0 subscribers
Be the first to start a discussion here.
Be the first to start a discussion here.
Prometheus (rocket engine)
Prometheus (rocket engine)
Prometheus (rocket engine)
View on Wikipedia
from Wikipedia

Prometheus
Model of the Prometheus rocket engine, featured at IAC 2022.
Country of originFrance
European Union
DesignerArianeGroup
ManufacturerAriane Group
Associated LVThemis · Ariane Next · Maia
Liquid-fuel engine
PropellantLOX / CH4
CycleGas-generator
Performance
Thrust, sea-level980 kN (220,000 lbf)
Throttle range30% to 110%
Chamber pressure100 bar (10,000 kPa)

The Prometheus rocket engine is an ongoing European Space Agency (ESA) development effort begun in 2017 to create a reusable methane-fueled rocket engine for use on the Themis reusable rocket demonstrator, Ariane Next, the successor to Ariane 6, possibly a version of Ariane 6 itself,[1] and the Maia reusable launch vehicle. [2]

Prometheus is a backronym from the original French project designation PROMETHEE, standing for "Precursor Reusable Oxygen Methane cost Effective propulsion System", and for the Titan Prometheus, from Greek mythology, creator of humanity, and god of fire, known for giving fire to humanity in defiance of the gods.

The engine is aimed to be reusable with substantially lower costs than traditional engines manufactured in Europe. The cost goal is to manufacture the Prometheus engine at one-tenth the cost of the Ariane 5's first-stage engine.[3][4]

By 2020, the program was funded and is under development by ArianeGroup.[4] By 2025, the engine had completed two successful test firing campaigns including four successive ignitions in a single day.[5]

General characteristics

[edit]

The engine is planned to have the following features:

  • Methane–oxygen propellant.
  • Extensive use of metal 3D printing (up to 50% of the engine).[4]
  • Open gas-generator cycle.[6]
  • 980 kN of thrust (~100 tonnes), variable from 30% to 110% thrust.[6]
  • 100 bar (10,000 kPa) chamber pressure.[6]
  • 360 s specific impulse (Isp).[citation needed]
  • Reusable 5 times.[7]
  • Around 1 million euros production cost.[6]

History

[edit]

The European Space Agency (ESA) began funding Prometheus engine development in June 2017 with €85 million provided through the Future Launchers Preparatory Programme, 63% of which came from France.[1]

By June 2017, Patrick Bonguet, lead of the Ariane 6 launch vehicle program at Arianespace, indicated that it was possible the Prometheus engine could find a use on a future version of the expendable Ariane 6 launcher. In this scenario, a "streamlined version of Vulcain rocket engine called Vulcain 2.1 would have the same performance as Vulcain 2". The expendable Ariane 6 was then expected to make an initial launch in 2020.[3]

By June 2020, the ESA was on board with this plan and had agreed to completely fund the development of the Prometheus precursor engine to bring the "engine design to a technical maturity suitable for industry". The objective of the overall program as stated in June 2020 was to utilize Prometheus technology to eventually "lower the cost of production by a factor of ten of the current main stage Ariane 5 Vulcain 2 engine".[4] In 2021, ESA invested an additional €135 million in the project,[8] including €30 million from DLR.[9]

The engine was started up in Nov 2022. It had a successful 12 second test firing in June 2023, at the THEMIS test stand in Vernon, France.[10] An additional successful hot fire test was reported at the end of 2024.[11] The second test campaign for Prometheus in Vernon finished in June 2025 after a second model of the engine performed a series of repeated hot-firing tests under various thrust profiles. On 20 June 2025, the engine successfully demonstrated 4 consecutive ignitions, a first in Europe for this type of engine. A third model of Prometheus will be tested at DLR's Lampoldshausen test site.[5][12]

See also

[edit]

References

[edit]
[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Prometheus (rocket engine)

View on Grokipedia
from Grokipedia
The Prometheus is a reusable, developed by under the European Space Agency's (ESA) Future Launchers Preparatory Programme (FLPP), utilizing and as propellants to enable low-cost, sustainable access to through reusable launch vehicles. Designed as the first of a new generation of high-thrust engines for medium- and heavy-lift , it features a , multiple ignition capability, and deep throttling from 30% to 110% of nominal to support precise and ascent maneuvers. Development of the Prometheus engine began in 2017 as part of ESA's efforts to enhance Europe's competitiveness in space transportation by adopting additive manufacturing techniques, which reduce production costs to approximately one-tenth those of traditional engines like the Vulcain 2. The project is funded by ESA member states including , , , , the , and , with leading the effort in collaboration with partners such as GKN Aerospace and Safran Aero Boosters. A parallel liquid oxygen-hydrogen variant is also under development to broaden compatibility with existing European launcher architectures. Key technical specifications include a sea-level thrust exceeding 100 metric tons (approximately 1 MN), an intelligent on-board control system for autonomous operation, and digitized diagnostics for rapid iteration in a "test-and-learn" methodology. The engine is engineered for reusability of 3 to 5 flights per unit, incorporating 3D-printed components to minimize mass and manufacturing time while ensuring reliability for main stage applications. Major milestones include the first hot-firing tests in 2022 at ArianeGroup's Vernon facility in , followed by a full ignition demonstration on June 22, 2023, marking Europe's initial success with a throttleable, methane-fueled engine of this scale. Additional tests in late 2024 advanced ignition reliability, culminating in a second hot-fire campaign in June 2025, where the prototype achieved four successive ignitions in a single day—a European first for a 100-tonne-class reusable . As of November 2025, a third engine prototype is slated for extended-duration tests at the P5 bench in Lampoldshausen, , to validate performance under simulated flight conditions. The engine powers the demonstrator, a 28-meter-tall, 3.5-meter-diameter reusable first-stage prototype that arrived at ESA's site in for integration and testing in mid-2025, with plans for a 20-meter hop flight by late 2025 to demonstrate recovery technologies. By enabling reusable propulsion, Prometheus supports ESA's broader vision for next-generation , fostering independent European access to amid global competition.

Development History

Origins and Funding

The Prometheus rocket engine project originated in 2015 as a collaborative effort between France's Centre National d'Études Spatiales (CNES) and ArianeGroup to explore innovative propulsion technologies for future European launchers. In 2017, the initiative was integrated into the European Space Agency's (ESA) Future Launchers Preparatory Programme (FLPP), marking its transition to a broader European endeavor focused on developing low-cost, reusable liquid rocket engines using liquid oxygen and methane propellants. This shift was approved at ESA's Ministerial Council in December 2016, aiming to enhance Europe's independent access to space by addressing rising competition from commercial providers like SpaceX. ArianeGroup, a France-based between and , serves as the primary developer, leveraging its expertise from the Ariane series while incorporating contributions from European partners including in , GKN Aerospace in , and Aero Boosters in . The core motivation was to drastically cut production costs for high-thrust engines, targeting approximately €1 million per unit—about one-tenth the cost of the Vulcain 2 engine used on —through advanced manufacturing techniques and reusability features, thereby enabling more affordable and sustainable space transportation for . Initial funding came from ESA member states via the FLPP, with ArianeGroup receiving a €75 million in to build and test engine demonstrators. , as ESA's largest contributor through , provided the majority of this support, reflecting its leadership in European development. In May 2021, ESA expanded the program with an additional €135 million to , which included provisions for testing facilities at Germany's DLR Lampoldshausen site to advance reusability validation. This funding aligns with ESA's overarching goals for reusable systems, as seen in parallel initiatives like the demonstrator.

Key Milestones

The development of the Prometheus rocket engine originated in conceptual studies initiated by the French space agency in 2015, with formal funding and a contract from the (ESA) commencing in 2017 to explore low-cost, reusable propulsion technologies. This phase laid the groundwork for a methane-fueled engine demonstrator, progressing through initial and feasibility assessments toward detailed by 2019, when the successfully completed its review, greenlighting construction of prototype hardware. A pivotal occurred in May 2021 with ESA awarding a 135 million contract to advance the demonstrators, enabling the startup of hot-fire test hardware manufacturing in 2022 and the initiation of preliminary hot-firing tests at ArianeGroup's Vernon facility in . The first full hot-fire test followed on June 22, 2023, achieving a 12-second burn that validated ignition sequencing and short-duration performance. In 2024, assembled the second engine model and began subsystem qualification efforts, coinciding with the installation of a engine onto the reusable stage demonstrator at the Les Mureaux site in October. These advancements were bolstered by a new ESA contract signed in June 2024 for further engine maturation. The second test campaign culminated in June 2025 at Vernon, highlighted by a June 20 firing that achieved four consecutive ignitions in one day, confirming reliable restart functionality essential for reusability. Following the tests, the Themis demonstrator arrived at ESA's Esrange site in Sweden in June 2025 for final integration, was fully assembled, and placed on the launch pad in September 2025 to prepare for wet-dress rehearsals. Looking ahead, a third engine model is slated for testing at the German Aerospace Center's (DLR) Lampoldshausen facility to expand qualification scope. Overall, these milestones advance the project from early concept toward full integration with the Themis demonstrator, targeting a maiden hop flight in early 2026.

Design and Technology

Engine Cycle and Components

The Prometheus rocket engine utilizes (LOX) and liquid (LCH₄) as propellants, selected for their high , cryogenic storability at moderate temperatures compared to , reduced soot formation relative to kerosene, and potential for in-situ resource utilization on Mars through the Sabatier process combining atmospheric CO₂ with water-derived . The engine employs an , in which a small portion of the LOX and LCH₄ is diverted to a separate for combustion, producing hot gases that drive a connected to the turbopumps, with the turbine exhaust then vented overboard to simplify the design and reduce development costs relative to staged-combustion alternatives. This cycle configuration supports reliable startup sequences, including a required chill-down phase of 2–3 hours to condition the cryogenic components prior to ignition. Key subsystems include a single-shaft assembly that handles both propellants, leveraging the comparable densities of and LCH₄ to enable a compact, ~10 MW power unit with integrated pumps for oxidizer and fuel flows, controlled via dedicated valves for precise mixture ratios. The igniter system relies on pyrotechnic or spark-based mechanisms to initiate methane-oxygen in both the and main chamber, facilitating multiple restarts essential for reusability targets. is achieved by routing LCH₄ through channels in the and walls to absorb heat, maintaining structural integrity under operational temperatures before the fuel enters the combustion zone. The operates at a nominal pressure of 100 bar, promoting efficient mixing and energy release within the and chamber geometry. Throttling capability spans 30% to 110% of nominal , enabled by electronic regulation of valve positions and speeds for ascent trajectory control and potential landing maneuvers. The features a bell-shaped, converging-diverging profile optimized for sea-level operation, with an exit pressure of approximately 400 mbar to maximize in atmospheric conditions while providing sufficient for enhanced vacuum performance during upper-stage-like ascent phases. This design, combined with metallic regenerative-cooled extensions, ensures durability across multiple missions.

Manufacturing Innovations and Reusability

The Prometheus rocket engine incorporates extensive additive manufacturing (AM), with approximately 70% of its mass produced using metal techniques such as . This approach enables the fabrication of complex, integrated components like impellers, disks, housings, valves, and the full assembly, significantly reducing the parts count from traditional methods and cutting assembly time by allowing net-shape production of intricate geometries. For instance, the and thrust chamber demonstrator (PROMETHEE GG) were entirely AM-built using powder on large-scale machines, demonstrating over 2,000 hours of printing for prototypes. The further simplifies manufacturing by avoiding the complexity of staged combustion systems. High-temperature alloys, particularly superalloys, form the primary materials for the engine's and , selected for their durability under extreme loads. with liquid (LCH4) circulates through the chamber walls, leveraging methane's properties to reduce gradients and minimize structural stress compared to hydrogen-based coolants, thereby enhancing longevity. This cooling strategy, combined with standard off-the-shelf materials where possible, supports the engine's lightweight integration into reusable stages without compromising performance. Reusability is a core design goal, with the engine targeted for at least five flights per unit through features like robust seals, wear-resistant components, and non-destructive inspection protocols. A Health and Usage Monitoring System (HUMS) enables real-time diagnostics to assess engine condition post-flight, justifying reuse without major refurbishment. Deep throttling from 30% to 110% of nominal , along with multiple restart capabilities, facilitates precise control for vertical landing maneuvers on recoverable stages. Cost reduction strategies emphasize a simplified using the , which lowers development and production complexity relative to full-flow staged combustion engines. Modular elements, such as swappable assemblies and standardized interfaces, allow for rapid refurbishment and high-volume manufacturing at rates of 50–100 units per year, aiming for a recurrent below €1 million. These innovations, driven by a "design-to-cost" methodology, position as a precursor to engines ten times cheaper than predecessors like the Vulcain 2.

Testing and Performance

Early Test Campaigns

The first hot-fire test of the Prometheus engine prototype occurred on 30 September 2022 at ArianeGroup's Vernon facility in , marking the initial ignition of the reusable methane-fueled engine. Subsequent testing advanced to a 30-second burn with re-ignition on 20 October 2023, also at Vernon, which demonstrated improved combustion stability and subsystem performance over longer durations. The inaugural full integrated engine test followed on 22 June 2023 at the same facility, integrated with the demonstrator ground model. This 12-second burn operated at partial thrust levels within the engine's 100-tonne nominal capacity, confirming stable ignition, combustion stability, and effective cooling across the engine components. The firing utilized ArianeGroup's high-bay test stand optimized for short-duration hot-fires. Key outcomes from these early tests included successful execution of start-up sequences, with data informing refinements to the injector design and enhancing reliability. These campaigns established proof-of-concept for operations, laying groundwork for reusability validations.

Recent Advancements and Verification

A key hot-fire test on 19 December 2024 at the PF20 bench in Vernon achieved a 41-second burn at 100% nominal using and biomethane, confirming engine reliability and accumulating operational cycles to de-risk future missions. In June 2025, conducted the second test campaign for the engine at its Vernon facility in , culminating in a significant hot-fire test on 20 June that achieved four successive restarts within a single day. This series accumulated longer cumulative burn time than prior campaigns, verifying the engine's range of 30% to 110% and high restart reliability for reusable operations. During these operations, the engine delivered a sea-level thrust of 980 kN, with a of approximately 310 seconds (sea-level) and steady chamber pressure at 100 bar, aligning with design targets for the . Verification relied on high-speed to monitor vibrations, temperatures, and exhaust plume characteristics in real time, complemented by post-test inspections that confirmed no material erosion or structural degradation. A third Prometheus engine model is scheduled for extended-duration hot-fire tests up to 100 seconds at the DLR P5 facility in , as of November 2025, to simulate complete mission profiles and further validate reusability. These tests build on resolutions to early challenges, including ignition delays in /methane mixtures and turbopump efficiency, addressed through iterative software updates to control systems.

Applications and Future Prospects

Integration with Themis Demonstrator

The Themis demonstrator is a 30-meter-tall, 3.5-meter-diameter reusable first-stage prototype developed by under the European Space Agency's (ESA) SALTO program to validate recovery and technologies through suborbital vertical take-off and landing () flights. Powered by a single Prometheus engine, the vehicle employs cryogenic liquid methane and liquid oxygen propellants, with the engine integrated directly to the stage's tankage structure to enable deep throttling for precise landing control. Integration of the Prometheus engine into Themis involves mating the throttleable, restartable engine to the cryogenic tankage, which utilizes autogenous pressurization for the oxygen tank and a hybrid approach for to maintain structural integrity during flight. The stage incorporates systems in the Flight Control Bay for autonomous operations, including real-time engine throttling to achieve soft landings, supported by four deployable landing legs. This configuration allows the demonstrator to perform short-duration burns while demonstrating the engine's reusability features, such as rapid restart capability. The primary test objectives for focus on validating powered vertical landing in a real flight environment following a 2–3 minute burn, emphasizing reusability through low-altitude hops that simulate ascent, separation, and recovery phases. The is planned for 2026 from Space Center in , after completion of combined ground tests—including cryogenic loading and interface validations—beginning in late 2025. As of November 2025, combined ground tests are underway at , with the still anticipated in 2026. These efforts aim to confirm the integrated system's performance under dynamic conditions, paving the way for advanced demonstrators. As of November 2025, the Prometheus engine has been qualified for Themis integration following extensive ground hot-fire tests at ArianeGroup's PF50 facility in Vernon, France, ensuring compatibility with the stage's structures and systems.

Role in Ariane Next and Other Launchers

The Prometheus engine plays a pivotal role in the Ariane Next program, Europe's initiative to develop a partially reusable heavy-lift launcher as the successor to Ariane 6, with operational flights anticipated in the early 2030s. As a methane-fueled, reusable first stage propulsion system, it enables efficient orbital insertion and potential stage recovery through its re-ignitable design and deep-throttling capabilities. Configurations envision clustering 7 to 9 Prometheus engines to achieve a total vacuum thrust of approximately 8,400 to 10,800 kN, supporting the stage's reusability for over 10 missions while maintaining precise gimbaling for attitude control. Beyond , the engine's versatility extends to smaller launchers like , a reusable small-lift vehicle developed by MaiaSpace, an subsidiary. Maia employs three Prometheus engines for its first stage and a vacuum-optimized variant for the second stage, targeting low-Earth orbit payloads with a debut flight around 2030. This setup leverages the engine's low-cost manufacturing and bio-methane compatibility to enable rapid turnaround and frequent missions for small satellite deployments. Looking ahead, Prometheus's architecture as the precursor to a broader family supports scalability for super-heavy lift vehicles or in-space applications, potentially through higher-thrust variants. Its adoption is expected to drive down European launch costs to approximately €35 million per mission by 2030, with reusability advancements projecting further reductions to €20–30 million by 2035, enhancing competitiveness against global providers. Recent testing campaigns have validated the 's readiness for these launcher integrations.

References

  1. https://www.esa.int/Enabling_Support/Space_Transportation/Future_space_transportation/Prometheus
  2. https://ariane.group/en/equipment-services/for-launchers/propulsion-systems-for-launchers/
  3. https://www.nasaspaceflight.com/2025/07/european-update-07082025/
  4. https://ariane.group/en/news/prometheus-reusable-engine-reached-a-major-milestone/
  5. https://www.eucass.eu/doi/EUCASS2017-537.pdf
  6. https://www.eucass.eu/doi/EUCASS2019-0743.pdf
  7. https://spacenews.com/esa-kickstarts-prometheus-reusable-engine-with-first-funding-tranche/
  8. https://3dprintingindustry.com/news/75-million-contract-signed-esa-ariane-groups-3d-printing-enabled-rocket-engine-126282/
  9. https://ariane.group/en/news/prometheus-development-accelerates-with-new-contract-from-esa/
  10. https://ariane.group/en/news/prometheus-demonstrator-of-future-engine-passed-its-definition-review/
  11. https://spaceflightnow.com/2023/06/28/first-hot-fire-test-of-europes-reusable-prometheus-rocket-engine/
  12. https://www.esa.int/ESA_Multimedia/Images/2024/11/Prometheus_engine_for_Themis_flight_model_during_assembly
  13. https://ariane.group/en/news/arianegroup-signe-lesa-contrat-futur-moteur-prometheus/
  14. https://www.esa.int/Enabling_Support/Space_Transportation/Future_space_transportation/Prometheus_fires_up_once_again_and_again
  15. https://www.esa.int/Enabling_Support/Space_Transportation/Future_space_transportation/Themis_the_journey_of_Europe_s_first_reusable_rocket_has_begun
  16. https://phys.org/news/2025-09-themis-pad-fully.html
  17. https://www.dlr.de/en/ra/research-transfer/projects/esa-projects/prometheus
  18. https://www.mobilityengineeringtech.com/component/content/article/53943-europes-reusable-rocket-prepares-for-first-flight
  19. https://theses.hal.science/tel-02888841v1/file/85901_PEREZ_ROCA_2020_archivage.pdf
  20. https://www.metal-am.com/arianegroup-tests-prometheus-reusable-engine-for-space-launcher/
  21. https://www.sciencedirect.com/science/article/pii/S0094576523002011
  22. https://cnes.fr/en/projects/prometheus
  23. https://europeanspaceflight.com/prometheus-completes-30-second-hot-fire-test/
  24. https://press.ariane.group/arianegroup-a-teste-pour-la-premiere-fois-un-etage-complet-de-lanceur-spatial-reutilisable-8915
  25. https://www.esa.int/ESA_Multimedia/Images/2023/06/Prometheus_full_ignition_ArianeGroup_test_centre_Vernon_France_22_June_2023
  26. https://www.nasaspaceflight.com/2023/06/themis-prometheus-hot-fire-test/
  27. https://europeanspaceflight.com/arianegroup-completes-key-prometheus-hot-fire-test/
  28. https://cerfacs.fr/wp-content/uploads/2023/10/Phd_Mouze-Mornettas_TH_CFD_23_141.pdf
  29. https://www.esa.int/Enabling_Support/Space_Transportation/Future_space_transportation/Themis_stands_on_the_launch_pad
  30. https://ariane.group/en/news/europes-reusable-rocket-prototype-themis-is-installed-on-its-launch-pad/
  31. https://www.diva-portal.org/smash/get/diva2:1591806/FULLTEXT01.pdf
  32. https://www.esa.int/Enabling_Support/Space_Transportation/Future_space_transportation/Signing_secures_next_steps_for_reusable_rocket_demonstrations
  33. https://europeanspaceflight.com/arianegroup-completes-themis-integration-ahead-of-combined-tests/
  34. https://www.sciencedirect.com/science/article/abs/pii/S0094576520300631
  35. https://ariane.group/en/space-transportation/maia/
  36. https://www.maia-space.com/news/prometheus-engine-mock-up/
  37. https://www.eucass.eu/doi/EUCASS2019-0949.pdf
Add your contribution
Related Hubs
User Avatar
No comments yet.