Natural illumination solution for rotating space settlements

TL;DR

This paper proposes a reliable natural illumination system for Kalpana One-style rotating space settlements, using passive optical components to distribute sunlight and enhance urban living space while maintaining stability.

Contribution

It introduces a novel light transfer scheme with passive components, avoiding large moving parts, and analyzes optimal settlement placement and urban density.

Findings

The scheme is technically reliable with no large moving parts.

Settlements are best located at the equator for stability.

Urban floorspace per person can reach up to 25,000 m².

Abstract

Cylindrical kilometre-scale artificial gravity space settlements were proposed by Gerard O'Neill in the 1970s. The early concept had two oppositely rotating cylinders and moving mirrors to simulate the diurnal cycle. Later, the Kalpana One concept exhibited passively stable rotation and no large moving parts. Here we propose and analyse a specific light transfer solution for Kalpana One type settlements. Our proposed solution is technically reliable because it avoids large moving parts that could be single failure points. The scheme has an array of cylindrical paraboloid concentrators in the outer wall and semi-toroidal reflectors at the equator which distribute the concentrated sunlight onto the living surface. The living cylinder is divided into a number of $\varphi$-sections (valleys) that are in different phases of the diurnal and seasonal cycles. To reduce the mass of nitrogen needed, a shallow atmosphere is used which is contained by a pressure-tight transparent roof. The only moving parts needed are local blinders installed below the roof of each valley. We also find that settlements of this class have a natural location at the equator where one can build multi-storey urban blocks. The location is optimal from the mass distribution (rotational stability) point of view. If maximally built, the amount of urban floorspace per person becomes large, up to 25,000 m$^2$, which is an order of magnitude larger than the food-producing rural biosphere area per person. Large urban floorspace area per person may increase the material standard of living much beyond Earth while increasing the total mass per person relatively little.