Can't research alien towers

[The Lone Badger]

My latest runthrough on Brutal mode in the Experimental version, I've developed Railguns and Lasers but the Railgun Tower and Laser Tower research nodes are still locked. There's no mouseover text to tell me how to unlock them either like there is on other nodes in the Alien tech tree. Anyone else run into this?

[Panterich]

Did you download plasma tower?

[The Lone Badger]

No. That's probably it then.