All the new Space Age content minus the other planets and interplanetary logistics. Play with the new toys, craft the new science packs, and battle the new enemies at home on Nauvis.
I've since learned that this is a Vulcanus thing. Seems like Nauvis is counting as Vulcanus with this mod pack, which makes using nukes pretty costly (they leave permanent lava lakes behind).
Upon further research it seems that because this mod allows both Ammoniacal ocean and Lava to exist on Nauvis, the crater is actually a mix of both. I've made a mod that removes this (in general, so it works for regular Vulcanus/Aquilo too).