Device for a spacecraft comprising: electronic boards (C); 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 (BP) for exchanging electric power between electronic boards (C); - a shared bus (BC) for exchanging data between the electronic boards (C); - a module (MGC) for managing the inputs/outputs and for telemetry gathering, per electronic board (C); - an electrical level interface (INE) between an electronic board (C) and the shared data exchange bus (BC), per electronic board (C); wherein at least one electronic board (C) 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 (CPP) for monitoring and protecting the power flows of the shared power exchange bus and a module (CPC) for monitoring and protecting the inputs/outputs in order to manage the power supply and the communication of the components of the electronic board (C). electronic boards (C); 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 (BP) for exchanging electric power between electronic boards (C); - a shared bus (BC) for exchanging data between the electronic boards (C); - a module (MGC) for managing the inputs/outputs and for telemetry gathering, per electronic board (C); - an electrical level interface (INE) between an electronic board (C) and the shared data exchange bus (BC), per electronic board (C); - a shared bus (BP) for exchanging electric power between electronic boards (C); - a shared bus (BC) for exchanging data between the electronic boards (C); - a module (MGC) for managing the inputs/outputs and for telemetry gathering, per electronic board (C); - an electrical level interface (INE) between an electronic board (C) and the shared data exchange bus (BC), per electronic board (C); wherein at least one electronic board (C) 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 (CPP) for monitoring and protecting the power flows of the shared power exchange bus and a module (CPC) for monitoring and protecting the inputs/outputs in order to manage the power supply and the communication of the components of the electronic board (C). - 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 (CPP) for monitoring and protecting the power flows of the shared power exchange bus and a module (CPC) for monitoring and protecting the inputs/outputs in order to manage the power supply and the communication of the components of the electronic board (C). <EOS>