Maybe I've just been on at the wrong time, but after nearly a week I have yet to see any of the non-permanent gates launch. I notice that they generally are not completed very far when I go to deposit minerals, and was wondering what happens when the launch time comes and the gate is not finished? Do the empty slots randomize, or does the gate fail to launch and start over?
From the wiki (which is quoting the game itself):
"...The percentage any stratum is filled equals the chance of that theme being produced. So if a gate launches with a beast stratum that is only half full, there is only actually a 50% chance that the stratum will lock in as beast themed. Only a completely filled stratum guarantees its theme."
If that random chance fails, then we get random levels.