TheMarcksPlan wrote: ↑25 Feb 2021 20:23
Re firing cycle time, here's what happens at the gun face
The rest is pretty straightforward. We need the second-stage hoists go from first stage pickup to tray (and back) in <12 seconds. That's easily doable.
Second Stage Hoists
The turret cross looks something like this drawing I did a while back and posted far upthread:
Shells ascend ~10 feet, powder ~17feet. To make the roundtrip journey in 12 seconds, minus a second for transfer, requires ~2 ft/s and ~3 fts/s for shells and powder respectively (~1.4- 2.1 mph). On the same HP we could speed up the descent - when the hoist is unloaded and working with gravity - and thereby slow down the ascent. Or we could specify a shorter cycle time.
We'll probably want to specify a shorter cycle time of, say, 7.5 seconds for the second-stage hoists. This will enable the ship to do short bursts at up to 8 rds/min when firing from near the loading angle of 45 degrees - which is around where the guns will fire at max range engagements and when doing long-range AA barrages against approach high-altitude aircraft.
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First stage hoists
I envision the first-stage hoists being outside the rotating structure, feeding the turrets via at least two independently-rotating rings that would periodically mate to the rotating structure. Again this is something only possible due to the absence of barbette - otherwise there's space for this solution. I'm not gonna redo the drawing completely (maybe I will if someone is earnestly interested); here's a 30sec sketch via Paint:
Red arrows for shell flows, black for powder.
It's not fully drawn, but each row of guns in the turret is 6-7ft higher than preceding one. On the three-row turret, the upper two horizontal areas would feed shell and powder decks devoted to third-row guns. Thus we can have 4-5 levels of stacked rotating rings around the turret circle, each feeding turret levels that service different rows of guns.
I've put another set of black arrows with question marks on the diagram. This represents the option of using a level(s) below the first-row powder floor for intermediate hoists to the second-row powder floors. If space on the floors becomes a problem or if we want more room to stow ready rounds (for high-rate bursts), this is an option. Otherwise the bottom two layers on the above drawing are superfluous.
[I realize this is not a great drawing so if somebody's really interested in the schematics, which make perfect sense in my head, I'll post a better version.]
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It might be possible to do a single-hoist system if we specify shell & powder magazines up around the turrets. Two good reasons not do so, though perhaps it's a worthwhile saving of machinery and generating plant:
- Powder we usually want as far low as possible for safety reasons. If we're sufficiently confident in our deck armor's impenetrability, however, maybe.
- Because the megaship carries so much shell weight (~800k tons probably), and because the hull is so deep, shell storage has a big impact on vertical CoG. With shell storage near the bottom of the hull, full-draft (ballasted) CoG is ~35ft below the waterline. If shells are stored abreast the turrets, ballasted CoG moves up to around the waterline. Most BB's had CoG above the waterline, however, so maybe we move the shells up - they're safer up there than powder. That removes a lot of first-stage hoist machinery.
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Tactical implications for surface engagements: The ship can dart in and out of maximum practical range for adversaries, firing short bursts at 8 rds/min then maneuvering back out of range using her 40kn speed. Typical shell flight time at >40k yards is
>80 seconds, megaship might fire 7 rounds in 45 secs (one in the chamber at t=0) then maneuver hard, exiting the enemy's target point at 22.5 yards/sec. By the time enemy shells start landing 35 seconds later, she's quite far from the aiming point (depending on turning radius specifications - as discussed upthread, this can be surprisingly low due to megaship's multiplicity of shafts and availability of reverse).
Of course the enemy can maneuver too but megaship will presumably be firing against a battle line, barrage style. Enemy maneuvers during shell flight time will only shift which ships get hit. [If the megaship is fighting only one ship, that's either a very unlucky ship or Japan has spent everything on its own megaship].
