This paper presents the design and modelling of a next-generation nuclear-powered mother ship capable of serving as a self-sustaining refuelling hub for unmanned maritime vehicles. A 140m vessel equipped with a 130 MWth Very High Temperature Reactor was modelled as an integrated energy system that converts nuclear heat into synthetic diesel (F-76), through high-temperature electrolysis, direct air capture, and Fischer–Tropsch synthesis. An Energy Management System (EMS) was developed to coordinate power balance onboard. The EMS was extended with a mixed-integer linear programming layer, allowing fleet-wide optimisation of refuelling and mission timing for up to six unmanned surface vehicles. Mission scenario simulation results show that the nuclear mothership can maintain long-term autonomous operations with minimal external fuel dependence, providing aself sustaining alternative to conventional refuelling operations.