The opening of the space business to the commercial market causes the cost and criticality of the on-board system to shift towards the payload component that delivers the value-added of the mission. As the cost of the payload increases, every effort is made to reducethe cost of the other elements of the spacecraft. The integration of the traditional on-board real-time control functions into a single platform component, denominated 'spacecraft bus', is one of the main effects of this cost-reduction effort. The new scenario is likely to require the allocation of additional real-time control functions to payload components. The immediate consequence of this phenomenon is the distrubution of on-board services across the spacecraft. In earlier work we have presented an engineering approach to the construction of the real-time software embedded on-board integrated platform components. In this paper, we extend that approach to address the future scenario in which real-time control functions may be distributed across multiple processing nodes in the system.