Launch from a pad in Wiltshire, rendezvous with a station, land on the Moon, orbit Mars—or jump to another star. A space flight simulator you can rewrite from the inside.
Download the beta (v0.17) Read the flight manual See the gallery Build an addonKosmos models the Sun, planets, moons and the asteroid belt with true orbital mechanics, and draws Earth, the Moon and Mars from high-resolution survey data.
Planet positions come from the VSOP87 theory, so every world starts at its true place in the sky for the date you choose. From there it follows a Kepler orbit, and your ship feels the gravity of whichever body it is currently falling towards.
Fly a staged launcher from a launch pad to low orbit, plan a transfer with the on-board MFDs, and put a lander down on the surface of the Moon or Mars. An autopilot written in Lua can fly the ascent for you—or you can take the stick and do it by hand.
Four sites on Earth—Chippenham and Twickenham in the UK, Helsinki, and Wagga Wagga in Australia—each have a pad, runway, hangars, tower and a full set of navaids: VOR, NDB, VTOL beacons and an ILS. Each has its own cameras.
Every one is a small JSON file, so adding your own is easy.
Addons can be aeroplanes. The Skylark twin uses simlib’s atmospheric flight model: lift and drag from every surface, stalls, flaps, wheels and brakes. Take off from Chippenham, then try an ILS approach back in.
Multi-function displays, a 3D cockpit with clickable screens, and in-sim tools for cameras, settings, the property tree and Lua scripts.
Orbit, Surface, Map, Attitude, Align Planes, Sync Orbit, Transfer, Docking, HSI, VOR, VTOL, ADF and more—all written in Lua.
Chase view, 2D dashboard or a 3D cockpit where the MFD buttons are clicked by ray-picking.
Cut to any ship, cockpit, interior or spaceport camera in the universe.
Labels, orbit line, key help, sound and volume, saved between sessions.
Read and write the live property tree.
An in-game script editor with syntax highlighting. Run scripts by hand, per frame, on a timer or when a property changes.
Press G for the galaxy map, pick a star and jump. Each star has a procedural planetary system of planets, moons, belts and comets, including one Earth-like home world. Real stars such as Sirius, Proxima, TRAPPIST-1, Betelgeuse and Rigel are hand-built, and ships with a quantum jump drive can hop to any star within 50 light years.
Ships, scenarios, spaceports, planets and instrument displays are JSON and Lua files. No compiler needed: drop a folder in addons/ and it appears in the game. A stock parts library built from NASA 3D models (Lunar Module, Agena, Mercury, Viking, Pioneer, the VAB and more) is ready to use.