A vision of the interior of Amalia, an air-inflated asteroid turned into a city for 1 billion people, a.k.a. a gravity balloon. The grey cylinders are edit: 1km long by 500m wide, each housing 50,000+ people. Each pair of hab-cylinders sits in an opening of one of the “flow dividers”, a thin sheet which separates the airflow inside the colossal asteroid into “layers” that encourage steady thermal convection to the city’s equatorial radiator, and prevent the mega-city from overheating. Each cylinder rotates to provide gravity.

Each city-tube is girded by an array of tensegrity trusswork, and different tubes are connected by compression bridges and tensile cables, which carry pipes and trains running from tube to tube that transport fluids, cargo and people. The whole city (the open interior of the asteroid) is 40km across, comparable to the height of Chicago or the width of many moderately large US cities, but it can hold a billion people because many layers of citytubes are essentially stacked on top of each other.

I wanted this piece to show a lot of detail (and I really should have started with a larger canvas – oops), and to have the vibrant, cluttered look I feel like a real space mega-city would have. To that end, you can see aircraft flying between cables and tubes, and the glows of trains and other climber-vehicles crossing cables. Plants also grow in the zero-gravity air, clinging to structures. There are supposed to be smaller artificial outgrowths clinging to bridges and cables too, but I was getting too tired to add those in.

Specifications were taken from Alan’s Gravitational Balloons page on “Global Air Heat Transport in a Gravity Balloon”. I messed up some of the technical stuff such as the positioning of cylinders, but I’ll get it right in the next one.