mc-missile

Players write a guidance program in a separate server application that controls a missile in flight. When a missile is fired from a crossbow or dispenser, the server sends the missile's state to the player's guidance server, and the guidance server returns control inputs for the next tick. The game updates the missile's state 20 times per second, and each update passes through three stages: receiving the control input, applying it, and then adding random noise before the missile moves on.

Guidance servers run as Docker containers on the same machine as the Minecraft server. The mod reads a PORT environment variable and exposes a gRPC server port that follows the protocol defined in guidance.proto. The only input the missile accepts is a rotation request for pitch and yaw, since the control moment gyroscope is the sole actuator. Angles are given in degrees, and the F3 menu displays them negated because projectiles use flipped headings.

The mod is published for Fabric only, on 1.21.4. It needs Fabric API. Only the server needs it, so players join without installing anything. mc-missile is open source under the GNU Affero General Public License v3.0 or later, and its source code and issue tracker are public. Christopher Besch and Thomas Hädicke are credited as the authors in the project's contributor list.