Thank you, it's exactly what i wanted.

I wanted to change the grenade craft because i think it is a little bit overcheat.

Why don't you try to make the silo with the rocket a vehicule and then, it put you in a rocket wich will be the true vehicule ?

Hope i helped you but i don't know anything in programation with Lua.

Is there anyway to change a recipe and/or the technology needed for an item integreted in the game ?