September 12, 2019


With a view to developing future reusable launchers, CNES has initiated a demonstrator called FROG in partnership with start-ups, students and non-profit associations. This demonstrator’s aim is to test and evaluate new guidance and navigation algorithms.

There are limits to what simulations can do, which is where real-life testing comes into play. To this end, CNES has devised FROG as an agile, experimental test platform.

FROG is a recursive acronym that stands for ‘Frog, a ROcket for GNC demonstration’. Initiated by CNES’s Launch Vehicles Directorate (DLA) to test landing algorithms for reusable launchers, FROG is a small-scale demonstrator of Vertical Take-off, Vertical

Landing (VTVL) concepts. Standing 3 metres tall and with a diameter of 30 centimetres, it is designed as a learning vehicle. DLA teams, working with partners from industry, academia and associations, are plugging new guidance, navigation and thrust control (GNC) algorithms into the demonstrator to test new solutions in responsive fashion and with short development times. Once validated, these concepts may be incorporated in larger architectures like the Callisto and Themis reusable demonstrators and other projects coming on stream in the decade ahead.

FROG is also seeking to break free from traditional development methods by turning to contributors from outside DLA. Several teams of enthusiasts are developing and testing solutions concurrently through an agile, experimental approach to think outside the box and rapidly devise new control methods

The FROG prototype, powered by a turbojet, made its first flight at the end of May 2019. The vehicle is equipped with all the systems required to land vertically, with a steerable nozzle, active attitude control and four legs to absorb the shock of landing. In the near future, there are plans to replace the turbojet with a small rocket engine to further improve the realism and fidelity of tests.


Jeremie.Hassin at