You know, it's funny. I went to where I was supposed to go, but the Nexus was closed. Nothing openable.
So I cased the joint like a good thief, looking for any entranceways. All around the facility is that stupid swamp, and I blasted my way through it and found no entrances.
Before I did that, though, I landed on K7 and kept walking wherever I could, following the rock wall. I had to fight some crabs, and it eventually led me to the mouth of a spider cave.
I thought to myself, "this looks like it may go beyond the north wall." If true, it might lead to native territory, where I didn't want to go (I had asked the Muties about where the various factions were).
I now understand that the spider cave leads (eventually) to the NoT. So if I had just kept going on my initial exploration, it would have led me right to the NoT as intended. (Instead, I went to the horticultural centre and did that quest).
That's kind of bad design. Because the way into the K7 facility is very protracted and unintuitive. I knew the spider cave would lead somewhere cool, but I wasn't sure it would be the facility.
Despite the awkward design, my intutition had told me to follow the caves, and I didn't listen. So now I'm going back to finish the job.