Convex/Concave mesh collider

Noone knows the answer?

@hajnis I know it's quite late, but what collider you use really depends on whether you want the ship to be able to fly inside of the hollow parts of that object or not. Also, checking convex on colliders does optimize it for rigidbody calculations, but isn't really necessary on static objects without a rigidbody. Besides, a convex collider can only have a maximum of 255 faces, and this looks quite a bit more detailed.

Mesh colliders are generally considered to be quite expensive processor-wise, but ones without rigidbodies aren't typically too bad (one reason why terrain can have tens of thousands of collision faces without lagging you out.)

If I were you, I'd use the normal concave collider unless it proves to be too slow, and in that case you're better off just making a low-resolution "hull" mesh that acts only as a collider, while the more detailed mesh is rendered visually.