Japan’s national space agency, JAXA has confirmed that the inaugural test flight of the Callisto reusable rocket demonstrator has slipped to 2026.
The Cooperative Action Leading to Launcher Innovation in Stage Toss-back Operations (Callisto) project, conceived in 2015, is a collaborative effort between the French space agency, CNES, the German space agency, DLR, and JAXA. The demonstrator will stand 14 metres tall and have a lift-off mass of around four tonnes. The primary goal of the project is to develop reusable rocket technology that could be applied to future rockets.
In July, CNES updated the design of its official website, adding new information to several project pages. The agency’s Callisto project page was revised, pushing the inaugural flight of the demonstrator from late 2024 to between late 2025 and early 2026.
On 28 October, JAXA provided an update on the status of the Callisto program at a Ministry of Education, Culture, Sports, Science, and Technology event. As reported by the Japanese financial newspaper Nikkei, the agency revealed that before moving on to an inaugural flight of Callisto, it would first conduct a 100-meter test flight of a smaller demonstrator. Although this test flight was initially expected in 2024, additional safety measures required at the Noshiro Rocket Test Site need to be implemented before the test could proceed.
As a result of the delayed testing of the smaller demonstrator, JAXA confirmed that the expected inaugural flight of Callisto has now definitively slipped to 2026.
Upcoming European reusable rocket demonstrators
As Europe looks to develop reusable rockets, several demonstrator projects are nearing their maturity.
CNES is expected to test its FROG-H demonstrator in 2025. FROG-H is a small 3.6-metre demonstrator powered by a monopropellant rocket engine being developed by the Łukasiewicz Institute of Aviation in Poland. The aim of the project is to build on the work done for the turbojet-powered FROG-T demonstrator by testing the solution under conditions that are more representative “from a propulsion point of view.”
Themis is a large reusable rocket demonstrator being developed by ArianeGroup under an ESA contract. In addition to the demonstrator itself, ArianeGroup is also developing a new rocket engine called Prometheus, a project that is also being funded by ESA. The initial T1H Themis demonstrator will stand at 28 metres and will be powered by a single Prometheus rocket engine. The first hop test of the T1H demonstrator will be conducted from Esrange Space Centre in Sweden.
While Themis is just a demonstrator, it will have a direct real-world application. In late 2021, ArianeGroup announced that it had created a new subsidiary called MaiaSpace that would pursue the development of a small rocket called Maia. The ArianeGroup subsidiary will make use of the architecture of the Themis demonstrator for the first stage of Maia and will utilize a vacuum-optimized variant of the Prometheus engine for its upper stage. The inaugural test flight of Maia is expected to take place in late 2025.
