Structures on Asteroids
Structures are ships without thrusters that can be spawned connected to asteroids in their faction's regions when a sector is generated.
They require a block both with features=ROOT and a valid root shape, such as RECT_ROOT. Its yellow port must be free (not connected to anything) and face the direction of the asteroid. See below:

In the regions.lua, the region that has structures requires ambient={-1}. It will then use structures of the faction with the faction ID of the faction field.
{
ident=98
faction=98
ambient={-1} -- No other ambient types are allowed.
asteroidDensity={0.2,0.2}
asteroidSize={12,24}
-- Other region fields here.
}
Create and save your structures as you would any other modded ship. They should be in the ships/ folder.
Reassembly/
└── mods/
└── Faction 98/
├── ships/
│ ├── 98_Structure_1.lua
│ ├── 98_Structure_2.lua
│ └── 98_Structure_3.lua
├── blocks.lua
└── factions.lua
└── regions.lua
When you generate new sectors for the faction, you should find structures on every asteroid.

Note that there is no way of controlling asteroid shape usage.
