Modular, Serviceable and Demisable Small Satellites: Engineering a Resilient European Space Defence Architecture

Europe’s defence, security, and critical-infrastructure missions are becoming increasingly dependent on small satellite constellations for communications, ISR, navigation resilience and environmental awareness. Yet most small satellites are still engineered as disposable assets, creating strategic fragility, rising replacement costs, and growing orbital sustainability risks. This paper presents a new engineering doctrine for small satellites based on three integrated principles: design for manufacture, design for service, and design for end-of-life, enabling Europe to field space systems that are affordable, but enduring, adaptable and sovereign.

Drawing on collaborative programmes between Leicester Space Park, the Satellite Applications Catapult, and the University of Oxford, we examine how modular spacecraft architectures can be optimised for high-rate European manufacturing while remaining fully compatible with in-orbit servicing and upgrade. Particular emphasis is placed on the UK’s Westcott RPOD (Rendezvous, Proximity Operations and Docking) Facility, which provides a unique national capability for validating servicing-ready spacecraft, docking interfaces and capture mechanisms for operational use.

Modularisation enables spacecraft to be built, tested and integrated using repeatable industrial processes, while also allowing failed or obsolete subsystems to be replaced in orbit, payloads to be upgraded, and missions to be rapidly reconfigured in response to emerging threats. For defence and security users, this transforms small satellites from expendable platforms into maintainable, upgradable space assets, significantly increasing resilience against both environmental degradation and adversarial interference.

Equally critical is design for end-of-life. In congested orbits, spacecraft must be demisable by design to ensure safe disposal, while modular architectures also provide a pathway to future reuse and recovery as European in-orbit servicing capabilities mature.

To ensure Europe’s space capabilities remain robust, affordable, and operationally available, sovereign manufacturing, servicing and end-of-life design must be developed with urgency, enabling systems to be sustained, adapted and refreshed in orbit without the delays and costs of repeated replacement programmes.