The new SALTO (ReuSable StrAtegic Space Launcher Technologies & Operations) project will strengthen Europe’s independence and competitiveness in space. The work programme will improve European reusable launch technology while significantly reducing launch costs. Meanwhile, the complete reusable space launcher precursor stage has been successfully tested for the first time in recent days.

What are the key objectives of the SALTO project?

The main objectives of the SALTO project are to:

  1. Increase the maturity of Europe’s first reusable launch vehicle technology.
  2. Achieve a significant reduction in launch costs.
  3. Drive progress in environmental sustainability and strengthen Europe’s competitiveness in critical space missions.

SALTO aims to validate the landing phase, which is essential for the recovery of the launcher. This phase is highly complex and requires a real learning curve through situational tests in order to build up European expertise in this technology. The target vehicle, which incorporates several technologies developed by the Ariane Group and its partners, will pave the way for even more ambitious launches.

SALTO project and its partners

The SALTO project under Horizon Europe is led by ArianeGroup and involves a collaborative effort of 25 Consortium Partners and 1 Affiliate Partner. Each partner brings unique skills and expertise to the project. By integrating various technologies developed by ArianeGroup and its partners, the project aims to create a target vehicle capable of emulating the high energy trajectory observed during actual operational launches. This achievement will lay the groundwork for future demonstrations of even greater ambition. The SALTO project unlocks a wealth of experience, expertise, and the power to harness project outcomes for breakthrough innovation. It enhances the reputation of the partners and shines a spotlight on the brilliance of start-ups and SMEs.

The Themis programme in SALTO

Themis is a project that builds on the decisions taken at Space19+ and the progress made in European re-use technologies. It adopts a more agile and cost-effective development approach. The initial phase of Themis will focus on the preparation of spacecraft technologies, the establishment of a test bed and static launch demonstrations at Vernon, France. In addition, the ground segment at the Esrange Space Centre in Kiruna, Sweden, is being prepared for the first “jump” tests and possible vehicle modifications. Themis is 30 metres high and 3.5 metres in diameter. The single-stage vehicle demonstrator is equipped with three aligned Prometheus engines, fuelled by a remarkable 130 tonnes of liquid oxygen and methane.

PROMETHEUS®, the engine that will be used

The European Space Agency (ESA), in collaboration with the French Space Agency (CNES) and supported by the German Aerospace Agency (DLR), is developing the revolutionary next-generation liquid methane-oxygen engine known as Prometheus®. Designed for future launch vehicles, this engine will be exceptionally efficient and economical. By using methane and liquid oxygen as fuels instead of traditional fuels such as hydrogen, Prometheus® promises a huge cost reduction. When completed, the Prometheus® engine is expected to have a thrust of about 100 tonnes, slightly less than the 130 tonnes of the Vulcain 2.1 engine used in vacuum configuration. However, the thrust of Prometheus® will be similar to that of the Vulcain 2.1 in the atmospheric flight configuration, which also produces 1 tonne of thrust.

The advantages of the new engine in SALTO project launchers

The new Prometheus® engine, which uses methane and oxygen instead of hydrogen and oxygen, promises many advantages. As well as being lighter and easier to build, it is also designed to be reusable. Although methane is not the direct cause of this feature, its higher density compared to hydrogen allows the use of smaller stages, which in turn facilitates reuse. Prometheus® can probably be reused at least five times, with thrusts ranging from 30% to 110% of its nominal 100-tonne thrust. This revolutionary engine will play a key role in future missions, including commercial satellite launches. To succeed, this technological challenge requires a new approach and the use of highly integrated design and innovative resources, in particular the extensive use of manufacturing such as 3Dprinting.

Esrange Space Center: where the launch tests will take place

The prototype of the reusable Themis launcher will undergo two test campaigns in Kiruna, Sweden. On 13 January, after years of preparation and construction, the EU’s first orbital launch complex, Esrange Spaceport, was officially inaugurated. In operation since 1966, Esrange Space Centre is located beyond the Arctic Circle at 68°N, 21°E, about 40 km east of Kiruna, Sweden. The facility covers an area of 20 km² and has an impact area of about 5200 km² where rockets can land without interference. Daily activities include sounding rocket launches, stratospheric balloon flights, etc, while the infrastructure includes launch pads, buildings, warehouses, and offices. The team successfully managed numerous gravel transports, developed advanced communication systems for the rockets, built new control centres and implemented procedures for a wide range of missions. The newly inaugurated Esrange Spaceport is scheduled to begin launching satellites into orbit in 2024.

What has happened in the last few weeks

ArianeGroup has successfully completed a 12-second static fire test of the Prometheus® rocket engine and Themis demonstrator stage. This milestone represents Europe’s first liquid oxygen and methane liquid propellant engine for reusable launchers. The test took place on 22 June at ArianeGroup’s vehicle and technology testing facility in Vernon, France. The eagerly awaited full-scale test of the Prometheus® engine, carried out directly on the Themis reusable stage demonstrator, is an important milestone. This achievement paves the way for the development of Europe’s future launcher family.

Looking ahead

The results and findings of the SALTO project will contribute to the overall objective of reducing launch costs by 50%, increasing the flexibility of the launch service and reducing the environmental footprint. In addition to the overall impact on reusability, several SALTO technologies will contribute to cost reduction, reducing the mass/volume of the launcher and using lower cost materials. The use of modular systems will better knowledge of the margin the transfer of functions to the ground infrastructure will allow better margin knowledge through increased process automation. In the future, the focus will be on developing key technologies for rocket engines, such as additive manufacturing and artificial intelligence, which are essential for monitoring and maintaining reusable engines.

Author of the article Lorenzo Iacopino

Author of the article Lorenzo Iacopino

Lorenzo Iacopino is currently pursuing his Master’s degree in Aerospace Engineering at the esteemed University of Bologna. His academic pursuits are driven by an unwavering passion for spacecraft and astronomy, fueling his commitment to exploring the vast frontiers of these disciplines. Beyond his scholarly endeavors, Lorenzo finds great satisfaction in contributing to the advancement and popularization of scientific knowledge. He is eager to learn from the space sector leaders and share his insights and expertise fellow scholars and the broader audience.


ArianeGroup tests a complete reusable rocket stage for the first time, ArianeGroup


SALTO – reuSable strAtegic space Launcher Technologies & Operations, SALTO