This proposal addresses sub-topic 1: R&I on new scalable satellite platform concepts and building blocks increasing the degree of satellite modularisation. SCHUMANN ambitions to strengthen the foundations of the future space ecosystem, by means of 2 complementary developments: (1) a Functional Spacecraft Module (FSM) consisting of a Refuelable Tank (RTa), along with a refueling experiment setup to support the testing and qualification of this module. This FSM will demonstrate that a “side”, standalone module development, by following appropriate design rules and leveraging previous OG developments, can be integrated at a late stage into an IOD mission. (2) a “Design and Development Specification for the Spacecraft Construction Kit” (DSSCK) consisting of a specification and tools aimed at guiding and supporting FSM developers, to make their modules compatible and usable in a single ecosystem.