Just curious, which parts have you upgraded so far, and in what order? Just anecdotal evidence, but we upgraded our forecastle first (not sure if i'd recommend that) and we always seemed to find new sectors at a pace that held steady with our rank. Others have thought that Surveillance plays an important role.
Hijacking this post to put some outdated information that was previously in the guide, it may be interesting to see what we originally believed.
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.
-When there is no difficult weather, you receive a message like this: No wind or turbulence detected. 2 surveillance levels sufficient for exploration.
-When you encounter difficult weather, you get a message like this: Experiencing high winds. Airship surveillance levels unaffected, but exploratory capability may be slightly hindered.
-When you are not able to gather a 2nd item, you receive a message like this: Additional anomalies detected. However, airship condition found insufficient for further exploration.
The use of the word "surveillance" in these descriptions suggests that the stat plays a role. Considering all of those messages together, it sounds like your surveillance level is sort of like the HP of your airship.
When you encounter winds or turbulence on your first item, it can reduce your HP. When the time comes to gather the 2nd item, if you do not have enough HP, you skip that item and move on to the next sector. Your surveillance level starts fresh for the next sector.
Edit: I've been able to disconfirm this theory. I now have had the case where I was unable to gather an additional node even after having no wind.
It's worth noting that while it sounds nice, our data haven't really demonstrated this strongly one way or another. Based on this theory you could hypothesize that there is a much lower chance of gathering a 2nd item after experiencing turbulence, a moderately lower chance after experiencing wind, and no penalty after not having bad weather. The following is our data, although a much larger sample is probably necessary to clearly demonstrate this:
-Failure rate after turbulence: 6 out of 12 (50%)
-Failure rate after wind: 4 out of 8 (50%)
-Failure rate after none: 0 out of 1 (0%)
Edit: Now that we have so much more data in our fancy database, lets re-run these analyses!
Another interesting observation from our results came from upgrading our aftcastle, which decreased surveillance by 4 points. After this upgrade we had significantly higher failure rate for finding a 2nd item:
-Failure rate before surveillance decrease: 4 / 14 (29%)
-Failure rate after surveillance decrease: 6 / 8 (75%)
However, take the above observations with a grain of salt. One confounding factor is that we also ranked up and traveled to higher sectors on the "after decrease" missions. The higher failure rate may just be because the sectors were more difficult.
Entertaining other ideas, it might be that surveillance influences whether you can gather items in a sector at all, and we haven't yet encountered a sector where surveillance is not high enough to gather an item. So far, we've always been able to gather a first item and occasionally unable to gather a 2nd. We haven't yet been at a sector where it was possible to gather a 3rd. There have been no "additional anomalies detected" after the 2nd item. Surveillance may also play a role in that, although it seems more likely that there is a cap of 2 nodes for each sector we've encountered so far.
One interesting tidbit is that gathering a 2nd item doesn't seem important for performance ratings (exp boost). On several occasions we've gotten "decent" and "satisfactory" ratings for a sector even when we've failed to get a 2nd item. Conversely, we've gotten "abysmal" ratings where we were able to gather both items but merely with "normal" retrieval levels.
Retrieval is a bit more straightforward. When you extract an item you get a message like this: High retrieval levels result in above-average extraction yield.
Again, the use of the word "retrieval" in this line highly suggests the stat is involved. In our own data, there is a very strong correlation between improving retrieval and getting better retrieval results/performance ratings. We've made a single improvement to retrieval (invincible aftcastle).
-Ratings before improvement: B, C, C, C, C
-Ratings after improvement: A, A, A
We actually just upgraded to enterprise aftcastle last night, and we've yet to see the results. It would support this theory if we see a rating even better than A when she comes back! Edit: Well she came back! We got quite a chunk of EXP but still an A rating (was hoping for S).
Unlocking the 2nd Airship
The following reports helped us figure out that it was sector 8 that was important:
- Rank 20 → 22, sectors 2 → 5 → 7 → 8, unlocked
- Rank 22 → 24, visited sector 8, unlocked
- Rank 22 → 23, solo trip to sector 8, enterprise rigging and all other parts invincible, unlocked! (Thanks Seravi!)
- Rank 27, 5 → 6 → 7 → 8, hit rank 27, unlocked (Thanks Tatsuo!)
- Rank 25, still not unlocked
- Rank 22, still not unlocked
- Rank 19 → 22, full invincible parts, stats are all at 80, still not unlocked (Thanks Inzoum!)