The oft-overlooked actual difficulties of space settlement. Not technology and logistics, but like, how hard it will likely be for the humans doing the job at first. And second. And then for a while after, too.
Plants in spaaaaaaaace
Growing fresh food in space habitats. Poop-potatoes. Wide-spectrum LEDs. Self-contained hydroponics/aeroponics.
Turning people into jelly. Differing human sensitivity to sustained g-forces in different directions. The wonderful engineering concept of the ship with omnidirectional seating that reconfigures on-the-fly for optimal g-resistance (The Razorback).
High-speed space impact
Turning into jelly and then having your jelly explode your ship, because physics. Relativistic baseballs. Long-haul space-racing and how to be your own butt-wiping pit crew.
Kinetic weapon diplomacy
Nuclear non-proliferation treaties in space. Orbital kinetic weapons and cloaked nuke-ships playing the role of the submarine as deterrent.
Interstellar highway program
Minimum viable star system bootstrap answering machine. The Fermi paradox. The odds that most of the signs of alien civilization that we might discover would be past.
The Universe Today Ultimate Guide to Viewing The Cosmos: Everything You Need to Know to Become an Amateur Astronomer by David Dickinson & Fraser Cain: Amazon
The Expanse Season 3: Prime Video
Guide to Space by Fraser Cain: YouTube