I believe it's the environment chamber. I'm on the second island, pretty close to the end it seems, and I need it to finish my doomsday weapon. Unfortunately, from what I'm seeing, it's impossible to get it unless I start over from the beginning so I can get all the doomsday data from the first island, which I thought I had done. Am I soft-locked out of the ending?

I've found two possible workarounds, but unable to implement them since the pages I've found seem to leave out crucial info on how to do it.