How big a bomb

[mike wightman]

That's just nasty...

it does make those cheap 0.1kt nukes worth using though

 

[Fritz_Brown]

I don't know that a penetrator would help much on starship hulls, though. Remember that a particle beam can be stopped by these hulls - a BSD penetrator isn't going to do much in terms of getting through the hull to get the bang inside.

 

[vegascat]

All you need to do is breach the surface of the armor, not the entire thickness.