Every crew that has taken one to a Korian site asks the same question on the way, and the catalogue answer has never satisfied anybody.
EXCAVATOR. Opens sealed Korian sites. Unarmed. Requires escort.
The complaint is reasonable. A vessel that goes to the most dangerous places in the galaxy and cannot defend itself in any of them looks like an oversight. It is asked whether the hull could carry a battery. It could. It is asked whether the crew could be armed. They are.
Neither changes the answer, because the constraint is not the hull.
A site does not open under pressure
Korian material has never been cut, drilled, burned, dissolved or broken. Three hundred years of trying has not scratched one Fragment, and it has not scratched one door either. What opens a site is not force applied to it. It is a very long, very careful sequence of correct approaches, and the Excavator is the vessel that can carry the equipment and the patience to perform it.
Mass spent on a weapon is mass not spent on that. There is no version of the ship that does both, and every generation that has tried to build one has produced a vessel which fights adequately and opens nothing.
And so it needs an escort
Which means that wanting Fragments — wanting to win, in the only sense the word has here — obliges you to build a fleet whose entire purpose is keeping something else alive. Not taking ground. Not breaking a colony. Standing around one fragile ship for as long as it takes.
Crews find this clarifying. It is difficult to be confused about what you are doing out there.
The Silence understand the arrangement perfectly, which is why they never engage the escort first.