I've had a great idea. Super-heavy spider mines. We know the distance band from our cities that Garkill likes to crash his Rok - it shouldn't be too hard for a spider mine to arrange to be at ground zero under the Rok and when it stops moving the repulsors and shields on the belly stop working. If the charge survive until then it can really do some damage.
It would have to be a really tough and powerful charge. A nuke would be one option. Normally a groundburst nuke on your own territory is something you'd avoid because of the fallout but given there's a Rok there full of dirty great Ork reactors and dirty great ork munitions and dirty great Orks which we'll be blowing up one way or another anyway that is pretty irrelevant. The really simple design would be gun style nuke but with a plunger instead of propellant. That takes U-235 though and we don't really use the stuff so we'd have to start an enrichment industry from scratch. I guess we'd actually ruggedize something more advanced.
It would have to be a really tough and powerful charge. A nuke would be one option. Normally a groundburst nuke on your own territory is something you'd avoid because of the fallout but given there's a Rok there full of dirty great Ork reactors and dirty great ork munitions and dirty great Orks which we'll be blowing up one way or another anyway that is pretty irrelevant. The really simple design would be gun style nuke but with a plunger instead of propellant. That takes U-235 though and we don't really use the stuff so we'd have to start an enrichment industry from scratch. I guess we'd actually ruggedize something more advanced.