Additional details from their Twitter account:

After months of preparation and anticipation, the Tower At Nine interstellar spacecraft launches from its home of Ren, beginning its acceleration to near-lightspeed to cross the vast expanses between the stars.

https://x.com/teeteegone/status/1851976871879094313

And a cutaway view can be found here: https://old.reddit.com/r/worldbuilding/comments/1fyzmn0/anatomy_of_a_spacecraft_the_tower_at_nine/