Open doors let railgun shoot through

[Koya2]

Right now railguns destroy all in their path, so we can't have any building in front of them. It occurs to me that doors could be used to protect the railguns and they could detect (maybe with circuits, although maybe automatically like happens with trains) when the railgun is going to shoot and open just before.

At the moment a door forced open will be destroyed by the railgun, too.