ORU-BOAS (ORU based on Building Blocks for On Orbit Advanced Assembly of Space Systems) project will develop and demonstrate an ORU concept (TRL 6) based on the Building Blocks developing in previous SRC calls and PERASPERA/EOF objectives. The main points to be developed are: - An ORU compatible with the different SI, payloads and services as indicated in the topic reaching finally a TRL 5/6 - This ORU to be used as "plug&play" module for the topic HORIZON-CL4-2022-SPACE-01-11 (In Orbit Demonstration phase) - To develop a Satellite Construction Kit user cases for future application in ISMA (In Space Manufacturing and Assembly) missions - The ORU design concept will include an AppStore and Open-Architecture mentality for the different modules as avionics. The ORU will be designed in a modular concept in order to be flexible and provide capabilities to upgrades in an efficient manner. This project will consider the needs and requirements of current PERASPERA projects: EROSS+ and PERIOD. The ORU-BOAS consortium is formed by SENER Aeroespacial (coordinator), Thales Alenia Space France, Thales Alenia Space Italy, ISISPACE and DLR. This consortium has a considerable experience in previous PERASPERA projects: SENER was coordinator of OG5 SIROM and Thales Alenia Space France coordinated OG4 I3DS, OG7 EROSS and OG12 EROSS+. Rest of participants have contributed also to these and others PERASPERA projects: PULSAR, MOSAR, ADE, ... SENER and ISISPACE are currenty working in PERIOD.