Where's the Secret Sector?
One of the rockman ship achievements is "Find the Secret Sector". There doesn't seem to be room on the map for a secret sector.
What's the secret sector?
Solution 1:
The "Secret Sector" is a location you can visit while following the quest to repair the broken Stasis Pod. It is home to a secret race, and their secret ship.
Here's a good video walkthrough of the events you'll need to encounter in order to get there. Having the Rock cruiser's Rock Plating makes part of this easier, but it's still a challenging set of events to trigger properly: