Building and flight
Parts, physics and tools
Design a spacecraft, test it in flight and change what does not work. The same builder also makes planes, rovers, boats, stations and articulated machines.
Build and customise a craft
Assemble engines, tanks, cabins, batteries, wings and other parts. Resize hardware, arrange staging, tune engine settings and check mass, thrust and fuel before launch. Part groups can be rotated independently to build at angles.
Paint directly on parts, add text or image decals and pack spare parts in cabins. In flight, an astronaut can carry, remove and fit supported parts for repairs and changes. Hinges, fairings and other parts whose connections are set at launch stay builder-only.
Fuel, electricity and balance depend on what you built. Moving a joint changes the craft's shape and centre of mass. Docking joins vessels; undocking and staging separate them.
Orbital and atmospheric flight
Coasting craft in vacuum follow analytic Keplerian orbits. Thrust, atmospheric drag, parachutes and surface contact use numerical integration. Flight and map views show the same simulated state.
Plan transfers and rendezvous on the map, place manoeuvres and use guidance to fly them. Optional N-body gravity adds the pull of other bodies. Its navigation tools include Lagrange-point targets.
Simulation details and limits
World positions, velocities and orbital calculations use double precision. The renderer works in nearby coordinates relative to the active craft. It does not decide the craft's physical position.
Time warp can take large steps along clean two-body orbits. Thrust, atmosphere, contacts and N-body interactions need smaller steps, so the available warp rate changes with flight conditions. Forecast paths remain approximations when more than one body's gravity matters.
Vessels in the loaded star system continue to be simulated when you switch craft. Other systems are archived while you travel. Multiplayer uses the same core flight simulation.
Re-entry and heat protection
Entry heating depends on speed, air density and the exposed shape of your craft. Parts facing the airflow heat up; protected parts receive less. Plasma follows the hull, and scorching stays on the affected surfaces.
This illustrates the model's speed³ term. It is not a live flight prediction: density, shape and exposure also change during entry.
How the heating model works
The model uses a Sutton-Graves approximation: heat flux grows with the square root of density and the cube of speed. Exposure is measured from the posed hull, including moving parts and open bays. Scorch remains attached to the part through rotation, staging and docking.
Heating, plasma and water are game approximations, not computational fluid dynamics or a chemistry solver.
Hinges, pistons and winches
Use joints for folding legs, moving arms and walking machines. Ropes and powered winches connect attachment points on separate craft. Slack cable does not pull; a taut cable applies force and can turn an off-centre load.
A winch can reel in, pay out, hold or detach. Battery charge and load limit its motor. Grabbers attach to payloads, and cargo bays can carry equipment inside a craft.
Cable simulation limits
Ropes use a massless two-end constraint. They transmit force and torque, but full rope wrapping, self-collision and snapping are not simulated.
Explore the surface
Leave a cabin, use a jetpack, plant a flag and collect rocks. Rovers use wheel suspension and traction. Floating craft displace water according to their submerged shape.
Drills remove terrain in the direction they point. You can dig shafts, trenches and tunnels with solid ground above them.
Excavation supports roofed cavities. It does not simulate water flooding into a new tunnel.
Set up a surface colony
Survey resource deposits and land colony hardware away from your home world. Mining rigs, storage, housing and a colony launch pad let you establish a base for local craft construction and launches.
Available deposits and colony hardware set the material, fuel and crew limits for a craft built there. You can also refill compatible liquid-fuel tanks on landed craft, within the colony's fuel allowance.
These are construction and refuelling limits, not a stockpile that depletes with each launch.
Program a flight in Mission Lab
Build flight programs from visual blocks. Add conditions, actions and guidance tasks for launches, staging, manoeuvres, rendezvous and landings. Programs operate the same craft and controls you use when flying manually.
A program belongs to its vessel and can continue while you inspect another craft. Progress is saved with the flight; supported separation handoffs can pass instructions to the next stage.
Edit parts and worlds
The built-in part editor changes behaviour, artwork, collision shapes and mass properties. The moving-parts editor animates deployable artwork; Engine Lab edits engine plumes.
Body Studio edits stars, planets and moons: their physical properties, terrain, atmosphere, water, clouds, rings and surface structures. Preview the result in flight or on the map.
Share mods through the Community Hangar, or export mods and worlds as files. Saves retain the exact mod versions they use, so editing a library mod does not silently replace content in an existing world.
Choose a world scale
The default solar system uses real distances and sizes. Compact 1:10 and 1:20 worlds shorten trips and reduce the energy needed to reach orbit. Rockets keep their size, mass, thrust and propellant; surface gravity stays the same.
| Scale | Earth radius | Vehicle size |
|---|---|---|
| 1:1 | 6,371 km | Unchanged |
| 1:10 | 637.1 km | Unchanged |
| 1:20 | 318.55 km | Unchanged |
Choose the scale when creating a world. It changes the simulation, rather than the camera zoom.
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