A device for a spacecraft includes electronic boards; elements that are robust to radiation, i.e. that have a foreseeable failure rate that is lower than a threshold called acceptable threshold, comprising: a shared bus for exchanging electric power between electronic boards; a shared bus for exchanging data between the electronic boards; a module for managing the inputs/outputs and for telemetry gathering, per electronic board; an electrical level interface between an electronic board and the shared data exchange bus, per electronic board; wherein at least one electronic board comprises: a part equipped with COTS components whose failure rate is unforeseeable or greater than or equal to the acceptable threshold; and a firewall formed of components that are robust to radiation and whose failure rate is foreseeable and lower than the acceptable threshold, comprising a module for monitoring and protecting the power flows of the shared power exchange bus and a module for monitoring and protecting the inputs/outputs in order to manage the power supply and the communication of the components of the electronic board.