By now you already have a sense of how everything works, and there won’t be any major surprises from here on out. When your airship reaches rank 50, you’ll start to measure your progression in how many sectors you’ve unlocked. Unlocking sectors can take a bit of patience, as you may have already discovered. It is all about luck and perseverance.
When your flagship reaches rank 50, it might be time to change your strategy from maximize exp to maximize chances to unlock new sectors. At present, we don’t know whether any specific stat is important, and it is starting to seem unlikely. The only sure-fire way to improve your odds is to take more trips! You can outfit your flagship with the best rigging you have and consider sending it out on short voyages to only sectors that have a potential to unlock new sectors. Sometimes you might be able to hit more than one sector with potential in a single trip (e.g., a trip from 11-15 to have a chance to unlock both 14 and 19), and other times it might be best to make single-sector voyages.
As you can see, there are two distinct sector chains, one that begins with 11 in the west and another that begins with 10 in the east. It is up to you whether you want to tackle both at once or pick one. The advantage to going east is that you will find a new airship upon reaching sector 18. The advantage to going west isn’t quite clear yet, no one has fully explored it! There is an advantage to making progress on both routes, the sectors closer to the middle are near enough that you can visit a sector from each route in a single voyage, giving you twice the potential to unlock new sectors.
If you plan to eventually use all four airships and have the most flexibility in airship configurations at higher levels, it is still really handy to make each set of parts as they become available. For example, right around when you discover your 2nd airship, you be able to use all four invincible parts making your old bronco parts available for your new ship. This trend will continue for your 3rd and 4th airships.
But if you are happy with just a single airship, you can make steady progress and make very few parts along the way. For sector 17 and beyond you will need at least an Enterprise forecastle, since 90 surveillance is the minimum requirement. However, that seems to be the only minimum requirement that we’ve encountered so far. It may just be possible to discover all 24 sectors with only the original bronco parts and an enterprise forecastle. I’ll be testing this idea, stay tuned!
I can’t confirm 100% but I was in the exact same situation you describe. I had been farming the same route day after day for optimal exp but was not finding any new sectors. I finally decided to try and change up my route to a less-efficient alternative and sure enough I discovered a new sector. I have since been under the impression that certain routes have the possibility of finding certain sectors.
This very same question has occurred to me, and others have reported your same predicament. It is possible that some sectors are only unlocked by visiting a specific sector, and if that is the case, it would be a super handy thing to have in the guide! I’m going to add this to one of the “unsolved mysteries” and hopefully we can get some others to share their observations and shed some light on it.
In the above guide, I proposed that Surveillance influences the probability that you will gather a 2nd item and retrieval influences your extraction rating. The biggest reason for believing this comes from the wording of the flight log. For each node that you encounter in a sector, you get a message reporting the weather conditions followed by the impact on surveillance level and exploratory capability.