A server-side datapack for Create: Aeronautics (Simulated) on Minecraft 1.21.1 / NeoForge. It adds blocks to the simulated:non_movable tag so the physics assembler leaves them in place instead of absorbing them into a contraption.
Item duplication — excludes item drains and Copycats+ blocks that can be abused to duplicate items when assembled into a sub-level.
Terrain-grab griefing — surface blocks like grass_block act as an anchor the assembler can't lift. On servers where bases sit on natural ground, a raider can't simply assemble a chunk of terrain into a ship and drag it through a base.
This is one layer and relies on your server setup. For it to actually stop raids:
grass_block (or other listed surface blocks) around a base, the harder a terrain-grab is.minecraft:netherrack to the list.Without a claim mod, a raider can build a contraption from non-listed blocks elsewhere and fly it in — so treat this as part of an anti-grief stack, not a standalone fix.
spawner, grass_block, item drains, mechanical drill, hand crank, and Copycats+ pressure plates and buttons.
Drop the .zip into your world's datapacks/ folder, run /reload, verify with /datapack list.
Edit data/simulated/tags/block/non_movable.json — add/remove block IDs under values. Keep "replace": false so the mod's own machinery stays intact.