Project progress
- Building momentum
The SALTO project consortium continues to achieve critical advancements, driving innovation and moving closer to its goals with every step.
Project’s Kick-off
The SALTO project, funded by the European Commission under Horizon Europe, has officially started. Its goal is to accelerate the development of Europe’s first reusable launchers, with ArianeGroup coordinating the effort. A kick-off meeting was held online, providing an opportunity for all consortium partners to align on upcoming activities and ensure effective project coordination. The project will conduct two test campaigns in Sweden to validate the vertical landing phase of the Themis reusable launcher stage prototype, a critical step towards reducing space launch costs and enhancing Europe’s strategic autonomy.
Systems Engineering
ArianeGroup defined and gathered the requirements for the SALTO T1H launch system, including the associated verification and validation logic. Specifications for the main subsystems and technologies were issued, ensuring their integration and operation. The SALTO T1H functional and physical architecture was established using Model Based System Engineering tools, with data and interface management closely monitored. Reliability, Availability, Maintainability and Safety (RAMS) analysis was performed to ensure the safety and reliability of the SALTO T1H demonstrator.
Virtual model of the Ground segment Concept of Operations
SALTO consortium partner CNES prepared a Virtual Model of the Ground Segment Concept of Operations (CONOPS) to be used by all consortium partners. This model facilitated the design activities for the future Kourou (Sweden) reusable rocket and ensured alignment on operational sequences across teams. The CONOPS will guide the Ground Systems definition, ensuring consistency with the project’s cost and environmental goals.
Aerodynamics / Aerothermodynamics & Flying Qualities
The aerodynamic shape of the T3 vehicle was defined and designed. Following iterations of details of the design were performed. An extensive parametric study was performed on the design of the aerodynamic control surfaces, the grid fins, of the vehicle. A further extensive numerical simulation campaign aimed at determining the thermal loads on the structure during the ascent and reentry phase of the T3 configuration. Particular attention was paid to the retro-propulsion phase as it is particularly critical for heat fluxes on aerodynamic control surfaces.
Furthermore, first versions of the Aerodynamic Databases were computed and the first version of the Aerothermal Database for the aerothermal and structural design of the vehicle was created by DLR. Based on the vehicle design by Ariane Group and the Aerodynamic Database by DLR, DEIMOS started the mission analysis and flying qualities assessment of the configuration, to evaluate the capability of the T3 vehicle to fly the desired flight profile and to identify the design drivers that steer the representativeness of the T3 flight experiment with respect to the operational condition of a full scale reusable launcher. Iterations were also performed in cooperation of DLR and MT Aerospace on the aerodynamic design of the landing legs.
In addition, the DLR designed and partly manufactured three wind tunnel models for the aerodynamic tests of the vehicle configurations in the remainder of the project.
Technology Assessment and evaluation for applicability to future launchers
It is aimed to assess the scalability of the technologies developed for the demonstrators to full scale flight vehicles. In this frame the mathematical background was built, to understand the design of vertically landing launcher stages in detail. Furthermore, first concepts for the structural integration of control surfaces and landing legs in the launcher structure and a compendium of available aerothermal data were compiled.
Health and Usage Monitoring System (HUMS) Technologies
In the frame of SALTO several health monitoring technologies are developed allowing in-flight monitoring and pre-flight launcher control and revalidation operations, as the knowledge of the health state is indispensable for the repeated flight of the same vehicle. ONERA, INCAS, IRT Jules Verne and SABCA have worked together with Ariane Group on the implementation of a structural health monitoring system in the T1H demonstrator. For this aim, sensors have been validated for the use in extreme conditions, material samples have been tested and simulated in lab conditions, and detection algorithms have been developed. Additionally, a monitoring concept for the vehicle was defined and is being implemented at the moment. A health monitoring for actuator systems is being developed in joint work of SABCA and DLR. Furthermore, an autonomous flight termination system is being developed by Thales Alenia Space and is going to fly on T1H.
Thales Alenia Space in Belgium is developing a range of flexible products suitable for the Flight Safety Systems (FSS) of European Launchers : the Safety Controller Unit (SCU), in charge of driving flight termination actuators from a range of potential causes, and the GNSS Receiver Unit (GRU), in charge of launcher localization. Autonomous Decision (aka AFTS) is a new feature that shall be demonstrated via a hardware and software extension of the existing SCU and GRU, in the context of SALTO T1H flight.
Landing legs
MTA successfully implemented an integral design for the rocket's landing legs, combining aerocovers and load. The design, originally developed by MTA, was revived and improved for this project. MTA transferred concepts from RETALT to compare with other landing leg designs, aiding in the study of their structural integration into the launcher.
Touchdown demonstrator droptest campaign with a sub-scale model
As part of the SALTO project, a touchdown demonstrator droptest campaign with a sub-scale model was done by the DLR Institute of Space Systems, Bremen. The primary objective behind this test campaign was to investigate the influence of sloshing liquid on the landing behaviour of a vertically landing vehicle. To achieve this, a lander engineering model was equipped with an acrylic glass tank and a series of drop tests was conducted in the Landing and Mobility Test Facility LAMA. Different filling levels and different vertical and horizontal landing velocities were tested. The acquired data is used to validate a touchdown simulator, which in turn is used to simulate the landing behaviour of the full-scale THEMIS vehicle.
Flight Safety System – Software and Hardware Design
New business models for launch vehicles demand lower costs, higher launch rates, and greater operational flexibility, necessitating the reduction of ground infrastructure. Traditional Autonomous Flight Safety Systems (AFSS) rely on ground-based radar and telemetry to issue termination commands, but this approach is becoming obsolete for New Space requirements. The shift towards reusable launch vehicles requires real-time, autonomous safety assessments and the ability to neutralize multiple stages, which current systems cannot support. Therefore, a robust and Autonomous Flight Safety System (AFSS) is essential
to meet the demands of modern orbital launch operations.
Themis: Europe’s reusable rocket stage demonstrator passes key integration fit-check
In December 2024, Europe’s groundbreaking reusable rocket first stage, Themis, reached a significant milestone with a successful ‘full fit-check’ at ArianeGroup’s facility in Les Mureaux, France.
The fit-check verified the mechanical connections and interfaces between key sections of the rocket, including the engine bay, fuel tanks, flight control bay and the upper structure. This successful integration ensures that the rocket’s parts fit and function together as intended, paving the way for further testing and development.
SALTO first results – webinar
On March 20, 2025, the SALTO consortium hosted its first project webinar, bringing together professionals to share updates on the project's progress and technological developments. The session featured insights into the latest advancements, details about the test facilities where the hop test will be conducted, and updates on the technology maturation process. Read the full summary of each speaker’s presentation to learn more.
Réaltra, announces delivery and installation of HD camera and Ethernet network switch
Project SALTO consortium partner, Réaltra, delivered two technologies including a HD camera featuring a global shutter and a space-ready Ethernet network switch. The HD camera is poised to deliver high-definition images of the hop test demonstration and it has been shipped to ArianeGroup at the Les Mureaux site in France where it has been successfully integrated into the Themis demonstrator.
Themis, a reusable first-stage rocket prototype, getting closer to its first hop-test
The assembly and final preparations of the Themis (T1H) reusable first-stage rocket demonstrator are nearing completion at ArianeGroup’s site in Les Mureaux, France. The vehicle will soon be ready for its upcoming hop test campaign at the Esrange Space Center in Kiruna, Sweden, marking a major milestone in Europe’s path toward reusable launch systems.
Themis arrives to Esrange Space Center in Kiruna, Sweden for hop test preparation
Themis, Europe’s first full-scale reusable rocket demonstrator, has arrived at its test site, SSC’s Esrange Space Center in northern Sweden, marking the beginning of the SALTO project’s ground and flight test campaign preparations.
It has reached its temporary home at “Launch Complex 3”. Over the coming weeks, teams from ArianeGroup and the Swedish Space Corporation (SSC) will finalize integration procedures inside a newly constructed facility tailored to support Themis operations.
Themis will then undergo several key steps known as “combined tests” where joint operations of launcher and launchpad will be conducted, allowing engineers to validate the performance of the vehicle and of its ground-handling systems, including autonomous cable reconnection procedures.
Final integrations at Launch Vehicle Integration Building (LVIB)
The SALTO consortium partners have been working on a range of activities to complete the integration procedures in preparation for transferring the T1H to the launch area. This final integration phase incorporates innovative technologies developed within the SALTO project, which will be validated during the test campaign. The campaign will also include a series of fluidic verification tests.
ArianeGroup lead the final integration process, with the support of other SALTO partners in integrating the specific technologies to be tested: National Institute for Aerospace Research “Elie Carafoli” (INCAS), German Aerospace Center (DLR), Thales Alenia Space (Belgium), Safran Electronics & Defense and Safran Data Systems, Deimos Engineering and Systems, Réaltra.
Verticalisation of the Themis
The vehicle transported the T1H from the Launch Vehicle Integration Building (LVIB) to a dedicated stand designed to support the integration of the 4 landing legs.
To achieve this, 2 cranes are used to lift the T1H into a vertical position and place it onto the support structure.
Themis on the Launch pad and its landing legs
The T1H (Themis-1 engine-Hop) demonstrator is now standing tall on its launch pad at the Esrange Space Center, equipped with all four landing legs for the first time. With the installation complete, the vehicle is fully assembled and ready to undergo its next set of tests that are required before the Hop Test.
SALTO project team's visit to Esrange Space Center
The SALTO project team had the pleasure of being warmly welcomed at Esrange Space Center, where our consortium partner SSC provided a guided tour of the test facilities. During the visit, the team had the unique opportunity to see the T1H standing proudly on its own landing legs on the launch pad. This visit offered an excellent occasion to discuss upcoming test activities and further preparations for the Hop Test campaign, strengthening collaboration and alignment within the project team.
Themis reusable launcher first stage prototype conducts a flight chronology rehearsal
The reusable stage demonstrator Themis conducted a flight chronology rehearsal. This rehearsal, also called wet dress rehearsal, marks a key milestone in the development of the launch system, comprising the Themis demonstrator and the ground infrastructure deployed at Esrange Space Center in Sweden.
The objective of the test was to simulate launch operations under cryogenic conditions, including pre-flight preparation of the demonstrator and its launch pad, as well as the system passivation that will be carried out after post-flight recovery.