er... they were rock ships. It is not the material which a craft that slips space and time is made of. The best material is "rock" and it is the technology that manipulates the "mass". The "weight". "Which doesn't exist at the "when" state.... Rock literally becomes a phantom material to move from-through space and time... Location. The technology is quite outside human reality. Humans are not "made" to understand. That is all. Humans believe they are meat. Lol.