A Modular Architecture for Space Habitats - From Rotating Tubes to Orbital Megastructures

The ladder-tube architectural system is designed for long-duration human habitation in space. It combines a non-rotating structural ladder with an independently rotating tube to provide artificial gravity, maintainability, and incremental expansion through attaching additional ladder-tube modules. The design integrates closed-loop ecological flows, including heat exchange, atmospheric cycling, water recovery, and nutrient circulation, into a unified metabolic system that supports long-term stability.As the modular design allows for the continued growth into very large structures, it is necessary for the architecture to incorporate distributed governance, education, and maintenance frameworks that mirror the modularity of the built environment. These social systems ensure continuity of knowledge, operational resilience, and the capacity for renewal across generations. A city scale formation of modules is designed to be constructed, maintained, and upgraded without large-scale disruption, enabling sustained operation over centuries.The ladder-tube grammar also extends naturally into curved and ring-based variants, allowing the architecture to scale from small habitats to large orbital settlements and theoretical megastructures. Its modularity also supports replication, fission, and relocation, enabling cities to adapt to changing conditions or seed new settlements.This document outlines the structural, ecological, and organisational principles, using the variant of the Stacked Ladder City, to demonstrate how these elements form a coherent, extensible system for humans thriving in space.