Concordia
The grey four-rotor station in black space, rotor names painted on its hull, with the open forward cage and spoked end disc nearest.

Concordia press kit

Concordia is a 21 km rotating city at the Earth-Moon L5 region that anyone can walk through in a browser. This page has what you need to write about it: the facts, six images, the film, free footage and a contact.

The short version

Use any of these as written.

Short. Concordia is a walkable simulation of a 21 km rotating space city at Earth-Moon L5. Four cities spin at Earth gravity, and the whole station opens in a browser.

Medium. Concordia is an interactive simulation of a rotating space city built at the Earth-Moon L5 region. Its four habitation rotors each turn once every 100 seconds to give 1 g, and visitors can walk its streets, ride the lift to weightlessness and follow a family from a kitchen to a launch track, free in a browser. The physics is real. The 2045 history is a speculative design.

Long. Concordia is an interactive simulation of a rotating space city, 21 km long, at the Earth-Moon L5 region. Four habitation rotors, each 2.5 km in radius, turn once every 100 seconds to give the ground Earth's gravity. Tsiolkovsky (Rotor 1) and Noordung (Rotor 2) spin opposite to Bernal (Rotor 3) and O'Neill (Rotor 4), so the station nets close to zero angular momentum and does not wobble. Visitors walk the streets, ride a lift from 1 g to weightlessness, tour the shipyard and spaceport, and follow a family from a kitchen to a 10 km electromagnetic launch track. The whole station is modelled at full scale and runs in a desktop browser at concordia.davidveksler.com, with a guide of plain-language science pages that works on any phone. It was made by David Veksler. The design descends from Gerard K. O'Neill's 1970s space settlements.

Facts

21 kmlong, end to end
4habitation rotors, 2.5 km radius, 1 g
100 sone turn of a rotor
384,400 kmfrom Earth, at lunar distance
57,000generated city buildings
84scenes in the atlas
16chapters in the 10-minute guided tour

What is real and what is invented

Real: spin gravity, counter-rotation and angular momentum, radiation and debris shielding, air loss through a breach, orbital mechanics at L5, and the engineering limits on each. Invented: the 2045 history, the economy that pays for it, the families and the names. The about page says the same in more words, and every number on the site is labelled with which kind it is.

The design started from Isaac Arthur's episode "The O'Neill Cylinder Space Habitat: Islands In The Sky" (2025-04-24), credited on the site. Concordia differs from the 1970s designs in using four sealed rotor cities instead of one and a shield that stands still.

How it was made

David Veksler designed it and directs the work. AI coding agents write much of the code under a written engineering specification, with automated checks and review on real GPUs before anything ships. The building page covers how the station itself is built, and David will talk through how the simulation was made on the record.

Film

A 1 minute 44 second film of the guided tour, in 4K: watch on YouTube. There is no voice-over.

Images

Six images from the simulation, free to use with the credit line below. Click an image to see it larger; the files in the table below are the full-resolution downloads.

Dense city of pale blocks, green rooftops and steel lattice under cool light, with a curved cream wall on the right.
A district under the megaframe, the steel lattice that carries the city.
Through a glass lift cabin window, a steel truss climbs the shaft, with city towers and walkways seen on either side.
Through the window of a lift, rising toward the axis and weightlessness.
Cutaway hub rings and bearings run across black space, with a grey rotor disc on the left and lattice trusses on the right.
The hub bearings where pairs of rotors spin in opposite directions.
A long ship with a tapered nose sits in gold cradles among steel trusses, with a large tube in the foreground.
The zero-g shipyard, with a ship in its cradles.
The grey four-rotor station in black space, rotor names painted on its hull, with the open forward cage and spoked end disc nearest.
The whole station, with its four rotors named on the hull.
A grey cylindrical station shows its spoked end disc at left, with a caged ring section beyond it and a planet above.
The station's caged end and spoked end disc, with a planet beyond.
File Shows Size
concordia-city-megaframe-2560.jpg The city under the megaframe 2560 x 1440, 1.5 MB
concordia-ascender-sky-2560.jpg The lift to the axis 2560 x 1440, 0.5 MB
concordia-counter-rotation-2560.jpg The counter-rotating hub 2560 x 1440, 1.1 MB
concordia-shipyard-2560.jpg The shipyard 2560 x 1440, 1.0 MB
concordia-station-pullback-1600.jpg The whole station (render enhanced with an image model) 1600 x 900, 0.3 MB
concordia-end-lookback-2560.jpg The caged end and end disc 2560 x 1440, 0.3 MB

Footage

Silent 4K clips of any scene in the film are free to use in videos and articles, monetized channels included. Ask at the address below and say which scenes; clips come as H.264 or ProRes. The film's soundtrack is not part of the offer, because its sound effects are licensed for non-commercial use only.

Credit line

Concordia by David Veksler, concordia.davidveksler.com. Earth textures: Solar System Scope, CC BY 4.0.

A link to the site is welcome. The full list of sources and licences is on the credits page.

Contact

David Veksler: contact@davidveksler.com. Interviews, a walkthrough of the station, a screen-share demo, a question about a number or a clip that is not here: write.

If you find something that is wrong, write that too. Every number on the site is labelled with its basis.