Optimisation of Assembly Sequences for Modular Solar Power Satellites Under Coupled Orbit-Attitude Dynamics

The scale of future space structures is expected to exceed the dimensional and mass limits of launcher fairings, requiring large modular systems to be assembled directly in orbit. During this process, the progressive addition of modules continuously alters the mass distribution, inertia tensor, and sensitivity to environmental disturbances, consequently modifying the orbit-attitude dynamics of the evolving structure. Accounting for these effects is therefore essential when planning assembly operations, particularly for large-area platforms such as solar power satellites. This work presents a dynamics-aware framework for planning the spacecraft assembly sequence in which the order of module installation is selected by explicitly considering the coupled orbit–attitude response while the structure remains uncontrolled. Orbital motion is modelled using a perturbed two-body formulation including Earth’s oblateness, solar radiation pressure, and third-bodygravitational effects, and attitude evolution follows rigid-body dynamics driven by gravity-gradient and radiation torques. The assembly process is formulated incrementally, adding a fixed number of modules at each step through a greedy optimisation that minimises a cost function based on the maximum attitude deviation while satisfying feasibility constraints. The framework is demonstrated on the ESA SOLARIS and SPS-ALPHA concepts and assessed in both geostationary and geosynchronous Laplace-plane orbits.Comparisons with non-optimised sequences and reduced-perturbation models show that assembly order and environmental disturbances strongly influence the dynamical behaviour. The proposed approach identifies sequences that reduce the resulting dynamical response while remaining computationally tractable forstructures composed of thousands of modules.