Are all of these handwaving propulsion? They seem to all be habitat designs.
Ok I'll take my shot at propulsion:
Pulse nuclear BUT:
For acceleration, we have a launch gun that fires more fuel at the ship, and the ship catches the fuel, imparting momentum from the catch, and more fuel for acceleration.
For deceleration, we have pellets that it catches up to and uses the catching to slow down with, AND gains fuel to decelerate.
If the catch can be done like an ion drive in efficiency, then you get ion drive efficiencies while gaining fuel for the pulse nuclear accelerations/decelerations.
The real problem would be timing the deceleration "catches", and a HELL of a railgun.
We aren't really doing this in current physics without a massive and functional orbital/planetary economy that gives cheap nuclear fuel and materials. We'll probably need solar wind antimatter harvesters as well, if those are actually a thing.
The drive in this design is not yet invented Helium 3 - Deuterium Direct Fusion Drive.
In your design how is it going to catch up to pellets if it's decelerating? I.e. pellets need to be pre-decelerated for this. Which raises the question, would it be cheaper just to bring all deceleration fuel onboard.
You'd spend years firing pellets in advance of the voyage, on the same trajectory but moving a little slower than the ship you plan to launch. Time it all so you catch up with the first of them just as you want to start decelerating.
And also it requires extraordinary navigation precision. These launches are going to be spread in time, which means that they don't happen from the same place (all celestial bodies move relative to each other). Which in turn means that when you approach the pellet there is going to be perpendicular velocity component.
Even without taking this into account all systems are going to need active guidance - there is no way you do single burn and end up in the same place in the same time few light years away.
The best schema is probably launching all fuels containers that should be picked up for retro burn at the same time with much higher acceleration (orbital rail gun and then a burner), and with very slightly smaller final speed.
Then on the main craft you do short retro burn to match speed to fuels containers, attach them and do full retro burn for orbital insertion.
Benefit of this schema is that you don't need to accelerate everything slowly using main engine, so your original booster can be way smaller. (Energy-wise it only works if you have stationary means to accelerate high-g-capable payloads, i.e. orbital railgun, in this case you don't have to accelerate extra fuel required for initial burn)
Are all of these handwaving propulsion? They seem to all be habitat designs.
Ok I'll take my shot at propulsion:
Pulse nuclear BUT:
For acceleration, we have a launch gun that fires more fuel at the ship, and the ship catches the fuel, imparting momentum from the catch, and more fuel for acceleration.
For deceleration, we have pellets that it catches up to and uses the catching to slow down with, AND gains fuel to decelerate.
If the catch can be done like an ion drive in efficiency, then you get ion drive efficiencies while gaining fuel for the pulse nuclear accelerations/decelerations.
The real problem would be timing the deceleration "catches", and a HELL of a railgun.
We aren't really doing this in current physics without a massive and functional orbital/planetary economy that gives cheap nuclear fuel and materials. We'll probably need solar wind antimatter harvesters as well, if those are actually a thing.