Ostranauts ship building
Grid layers, hull and flooring, rooms, airlocks, and the fastest way to expand a starter hull.
A grid with hidden floors.
Most building questions come down to what occupies each layer.
Every tile has several layers. The subfloor holds abstract space for things like subfloor bins and fuel tank piping. The floor carries airtight flooring and storage like cargo webs. The space above the floor splits into lower and upper: equipment, loose items, racking and people use the lower slot; lights, vents, overhead bins and air pumps use the upper one. The ceiling layer is for power conduits and does not need to be sealed.
Seal what you need.
All hull pieces connect, and airtightness is a choice.
All hull pieces connect to each other regardless of brand, and a ship does not have to be airtight. It is usually smart to keep one pressurized room anyway. Floor tiles under interior walls make it easy to move the wall later without pressure loss, and flooring under exterior walls adds hit points against micrometeors. Every floor tile adds mass, so there is a tradeoff.
Labels matter when you sell.
Equipment works anywhere; rooms set the price.
The room list matters most when buying or selling a ship. Equipment works in any room, and NPCs will use it anywhere. Rooms mainly change the ship's resale value, so a correct label is worth money when you sell.
Floors first.
The fastest upgrade on a Box Sled is more floor.
The quickest expansion on a Box Sled is to bolt on more floor tiles: the sled is mostly open and unpressurized, so floors give you carrying space without a full rebuild. After that comes walls, extra O2 and N2 pumps, and a heater. In the editor, right clicking an object in any inventory, including the ground, lets you order an install directly.
One true airlock.
Extra EVA exits use standard doors.
An airlock is a room built around the docking port. Some starter hulls, like the Gas Sled (Box Sled), begin with no airlock at all: the door opens straight to vacuum. Others have a buffer airlock or a turbo pump airlock. Community reports say a ship gets one true docking airlock, so a second EVA exit usually means standard doors, or rebuilding the ship around the airlock to reposition it. The docking port itself cannot be modified.
Yes, it is in the game.
Fire in the Hold added real ship-to-ship combat.
Ship-to-ship combat arrived with the Fire in the Hold (0.15) update on 21 April 2026. It adds ship-mounted weaponry: Point Defense Cannons (PDCs), Mass Throwers, Missile Launchers, and a Decoy Launcher, plus Armor Cladding. Combat is centred on Ceres, where two factions fight a proxy war and pirates hunt for profit. PDCs fire 20mm shells, auto-target missiles and locked targets inside an 85 degree arc, and are best used as defense rather than primary guns. The wiki warns that ship combat is unforgiving: prepare the ship before picking fights.
Common questions
Do I need walls everywhere?
No. One pressurized room is enough for safety; walls add mass and take time to build.
How do I expand my ship?
Install floor tiles first, then walls and life support. Salvaged tiles work fine.
Can I move an airlock?
Only by rebuilding around it. A ship has one true docking airlock per community reports; extra EVA exits use standard doors.
Do rooms matter mechanically?
Only for buy and sell value, not for equipment function.
Is ship combat in the game?
Yes. Ship-to-ship combat arrived with the Fire in the Hold (0.15) update in April 2026: PDCs, mass throwers, missile launchers, decoys, and armor cladding, centred around Ceres.