The original note, as written at the time
Imagine a spacecraft that moves at a constant acceleration of 1 g (9.8 m/s²) into deep space. This would make the craft’s base floor always have a feeling of gravity.
Ongoing development
A spacecraft that accelerates continuously at 1 g into deep space, so that the floor of the craft always feels like gravity.
The appeal is that the artificial gravity is not artificial at all. It is the same thing that holds you to a chair on earth, produced by the same acceleration, and no rotating habitat can match it because rotation gives you a gradient — heavier at the feet, lighter at the head — and the inner ear notices.
The consequence is the itinerary. A ship at 1 g reaches relativistic speeds in about a year of ship time, so the solar system becomes a place you can cross in weeks and the nearest star becomes a decades-long voyage rather than a centuries-long one. Both of those are transformations of what is reachable, and both depend on one thing: sustained thrust.
That is the whole difficulty and it should be stated without romance. Constant 1 g requires a power source and a reaction mass that do not exist, and the engineering is not a matter of scaling up what we have. It is a different class of propulsion.
The design questions that follow are the interesting ones. A ship that is always accelerating has a floor and a ceiling, so the interior is a building, and it can be furnished like one. A ship that must turn over at the midpoint has a moment where everything is weightless, and that moment has to be designed for — the water, the toilets, the sleeping.
If the propulsion ever arrives, the architecture is already solved: build a building that falls upwards forever.