Let's assume the Kennedy-class missile cruiser was designed with a Spun Hull. This would require 180 tons (900 x 20%) be allocated to fuel, cargo or low maintenance machinery. The cruiser carries no fuel beyond fissionables (0 tons) ans not much cargo (37.8 tons). I don't think the ship has any significant components that can be considered "low maintenance" -- certainly not the powerplant.
So, the cruiser would have to greatly reduce the size of the powerplant (and thus stutterwarp drive) to get sufficient free "waste" space for the spun hull. This clearly makes the spun hull version significantly less capable than the printed version.
So, no, I think that 20% space requirement for non-critical components rather eliminates warships from using spun hulls.
Well, a ring configuration (the one I'm defending here), while being spun hull might be empty in its center, so not really needing to devote any such space to fuel, cargo or low maintenance machinery.
For solid spun hulls, there's no such 20% space requirement for non critical components, but what is said is that 20% of the ship`can be held at comfortable gravity, for humans, the rest being not. The advantage of the ring configuration is that this 20% is in fact most of the ship volume. As no bouble is needed by the warp, the empty space is not counted (as I understand) for mass.
The space that is unusable for crew and passengers, and usually used by cargo, fuel or low maintenance machinery is the central 15m radius, that uses to be empty in a ring configuration. And even so, it does not say that it is unliveable by humans, and the fact it may be used by low maintenance machinery hits (as I see it) that people can work for short periods on it.
OTOH, I guess this same ring hull configuration would need to be more or less balanced to maintain structural integrity. If one side holds too much mass more than the otherm I guess the ship will ahve some kind of problems. All of this is represented in my
Steer Wheel Warp Frame design.
In this same design, as I told in the description (sorry, I could provide no graphics, my graphic skills being abysmal), and for those same balance reasons, in the center of the ring there is section (united to the main ring by the pylons) that holds the power plant, and warp drives that I guess can be considered low maintenance (most control functions are performed form other parts or by the repair bots). After all, the need of only 6 engineering crew (2/shift, I guess) for a 110 dton fision plant (and the fact that, being a fission plant, probably people don't work directly on it) and 1 per shift for the warp drives (in the bridge) makes me think that people rarely visits this part.
I don't see why the Kennedy could not have a similar configuration, with its fusion power plant in the central part of the ring and the spun habitat in the ring itself. Depending on the width of the ring, the radius could be quite good for it.
The main problem I see on this configuration in military ships, aftyer thinking a little more on it, is for the turrets and missiles controlers and TTAs, as the rotation of the ship may change the aspects for them, unless also set in the center part (that will probably be larger than the unusable 15 m radius), leaving the spun ring just for the habitats.
