A space simulation of a whole galaxy, built on the real sky

The sky is a catalogue. 119,626 stars from the HYG database, corrected against Gaia DR3, Hipparcos and the Washington Double Star Catalog, sit where astronomers measured them, and every one you can fly to has a generated system: planets on Keplerian orbits, moons, rings inside the Roche limit, belts at the resonances of the giants, stations at the Lagrange points. Distances are true: Neptune is 4.5 billion kilometres from the Sun, and you cross that on your own drive. We began with the stars that have the best data; the rest of the Milky Way is generated by the same simulation and arrives next.

The ship is a place. The Calliope has two decks and a crew of seven, and her reactor, power bus, fuel and life support are live systems you read off the overhead panel. Fly her on a Thrustmaster Warthog with true Newtonian physics, stand up from the helm mid-cruise, and the planets keep sliding past the canopy. Her water is her propellant and her radiation shield, and the dose model behind the cabin readout agrees with flown dosimeters within a factor of two.

The worlds are whole. Eight procedural planets and moons you land on and walk to the horizon, gas giants whose weather is grown for each planet from its own seed, moons checked against photographs of our own Moon, and black holes and neutron stars drawn from their physics along closed-form Kerr geodesics, bending the real stars behind them. On the ground there is a war to fight at Vennik Flat, neon cities and ancient ruins to explore, and a moonbase being furnished.

Underneath is the simulation behind the game, a Python model of the galaxy that generates every system from a 107-type planetary science corpus and whose procedural Milky Way is being ported into the engine now. The fiction is set in 2538 in the Freeholds, a ragged chain of independent worlds on the rim of human space.