Aeronautics Anti-Grief & Dupe Patch

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.

What it patches

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.

Important — how to make the anti-grief layer effective

This is one layer and relies on your server setup. For it to actually stop raids:

Use a claim mod (e.g. OPAC) so players can't build, glue, or dig inside/under other players' claims.
Ensure bases sit on covered ground — the more grass_block (or other listed surface blocks) around a base, the harder a terrain-grab is.
The Nether has no grass; if you don't disable claims there, consider adding 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.

Currently included

spawner, grass_block, item drains, mechanical drill, hand crank, and Copycats+ pressure plates and buttons.

Installation

Drop the .zip into your world's datapacks/ folder, run /reload, verify with /datapack list.

Editing

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.