Wormholedrives and stardrives

[General Hawkwing]

Intra-solar system ships verse galaxy spanning ships is an interesting idea. However, I wonder about the long-term value of ships that are restricted to one solar system. As your borders expand, how much defense is required for the home system. How much cheaper would it have to be to make it worth it? Remember that the cheaper cost is offset by the additional expense of researching to separate lines of engines.