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 suite of small-scale demonstrators of Vertical Take-off, Vertical Landing (VTVL) concepts.

Standing three metres tall and with a diameter of 30 centimetres, FROG-T is designed as a learning vehicle. Teams at CNES’s Space Transportation Directorate (DTS), working with partners from industry (Drone-Center, Polyvionics), academia (IUT Cachan technology institute) and associations (Planète Sciences), are plugging new guidance, navigation and 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.

The FROG-T prototype, powered by a turbojet, made its first flight at the end of May 2019. The vehicle is fully equipped to land vertically, with a steerable nozzle, active attitude control and four legs to absorb the shock of landing. It is now entering its operational phase and will be used, for example, for the Horizon Europe SALTO project. A smaller electric version (FROG-E) also exists and a version with a small rocket engine (H2O2) is in development, to be called FROG-H. This version will make FROG more representative in terms of propulsion.

FROG is also seeking to break free from traditional development methods by turning to contributors from outside DTS. 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.

CNES CONTACT

elisa.cliquet at cnes.fr