The challenge in space data acquisition, e.g. for earth observation, lies in limited data-downlink capacity. Advances in onboard processing technology prompt exploration of deploying edge computing on satellites to alleviate data transport issues. This can be achieved through individual satellites or specialized networks akin to public cloud data centres. Use-case evaluation and stakeholder validation shaped system requirements for a generic Space Data Centre (SDC) architecture that was devised and simulated in Excel, integrating technology roadmaps and user needs. The analysis highlighted a tipping point favoring onboard edge computing over raw data-downloading, essential for future space and satellite ecosystem's efficiency.