Alex and Bobbie managed to get in their suits, refuel/restart Razorback's fusion reactor, make a plan and take positions, all in very short period of time, cause when they dumped the core that ship was in visual range, now onto them, inbound less than 2-3min.
Hand-sized grenade planted on inner wall of the engine cone, only far as hand can reach, blew up entire ship, even if engine cones are made of materials resistant to fires and explosions of fusion reactor exhausts, specifically to prevent those from spreading inwards, and so missiles can explode into engine cones, causing them damage, but if lacking penetration, without blowing up entire ships.