Shipbucket

Hello everyone! Long time no see...

This is a pet project I've been grappling with for some time, but it occurs to me that I could really use some help "debugging" the design! The basic premise is a modern nuclear-powered cruiser; in aesthetic terms the current design owes a lot to the Zumwalt (I will admit to liking its looks, if nothing else) albeit without the controversial tumblehome:


Note: I've included an incomplete top view to help illustrate the shape of the vessel



The main issue is the powerplant. I've opted for a very inefficient and cumbersome CONAG arrangement of two D2G-size reactors and two gas turbines largely because of my ignorance of the dimensions of nuclear plants. The D2G is one of the few naval reactors I can roughly size (thanks to the below-decks part sheet!), yet it really lacks the power output for a ship of this nature- hence the need for the gas turbines. Ideally, I'd prefer to fit a single, larger reactor- possibly an A4W- but the classified nature of that design makes it very hard to guesstimate the space required.

I don't suppose any of you guys have any thoughts- however vague- about the space required for a nuclear plant based around a single A4W?

A secondary issue concerns the hangar. I wonder if it seems a little small, considering the size of the flight deck...

Oh...and I should point out that the design is for an offsite AU-style project, hence the purple lower hull.

You've got what, 110,000SHP available on this? That's slightly in excess of a Zumwalt (assuming you're using the latest, greatest LM2500s - why no MT30s)? What's the specific reasoning for going nuclear in this case?

_________________
AU Projects: | Banbha et al. | New England: The Divided States
Blood and Fire

To be brutally honest, the specific reason is my personal preference for nuclear propulsion! It's always fascinated me and this project was always intended to explore that. If you want an "in-sim" justification though, the specific circumstances of the AU scenario make fuel supply one of the larger logistical constraints...which is why I'm not at all happy about those gas turbines.

I opted for LM2500s simply for commonality with my frigate design, which is conventionally powered (although I had prepared a speculative LWNP variant).

Not bad. Since you're using an all electric setup anyway you should consider carrying the gas turbines in the superstructure. With two reactors to provide ballast there should'nt be any problems with topweight, and it will save you a ton ton of duckting and generally make the design simpler.

_________________
“Close” only counts with horseshoes, hand grenades, and tactical nuclear weapons.
That which does not kill me has made a grave tactical error

Worklist

Source Materiel is always welcome.

That's fair enough then. I do however agree with Thiel you could move the gas turbines top side for the sake of ease of access. Which leads me into another question how are you going to do repair and refuel on the reactors buried so deeply in the ship without clear access routes to them? Short of blow torching your way down I can't see as there's any logical way to get to the forward reactor.

_________________
AU Projects: | Banbha et al. | New England: The Divided States
Blood and Fire

That's a very good idea...
This is why I placed the aft reactor beneath the hangar...but yes, I do agree. I suppose it's hopelessly naive to imagine that you can fit a modern core that will last for the lifetime of the vessel?

The truth is...I don't see how you can have easy access to the reactor without wasting a lot of topside space. If you can think of any arrangements that would work (and still keep the reactors dispersed)...well, I'm all ears.

Honestly, I'm not sure. Nuclear propulsion isn't something that I'm well read in.

At the very least you need pathways to extract spent cores for replacement if you can't use the same fuel for the entire lifespan which would mean short of performing a right angle turn the forward reactor is going to have a very long way to send its spent fuel up.

Have you thought about perhaps having two separate towers for the superstructure? Have the turbines on on the deck immediately below the main deck, use the amidships space for boat handling and what not while at sea and have the forward reactor refuelled / repaired that way. The aft one as you mention isn't as hard to get to.

You could also probably shorten the helipad considerably if you're only expecting to operate H-60s off of it.

_________________
AU Projects: | Banbha et al. | New England: The Divided States
Blood and Fire

I have. I actually considered an arrangement similar to this as that would allow the reactors to be sited beneath the flight deck...but I reckon that would require a major redesign and I'm also unhappy with the weight distribution. This is what I've come up with so far:



Alternatively, I have tried two other arrangements:

I think that the first of the pair of alternatives would be your best bet. The latter has a big open whole in the main deck where that pair of turbines is which I'm dubious of.
My last concern is the lack of CIWS gun, laser or missile. ESSM is all well and good but if I were building it I'd probably have some sort of close-in systems not least as fail safes against ESSM being taken out of action for whatever reason.

_________________
AU Projects: | Banbha et al. | New England: The Divided States
Blood and Fire

well, not an bad effort at all. a few things come to mind first of all, loose from the powerplant.
- it might be an idea to fit AGS-Lite, if shore bombardement is not the main reason of existance for this ship
- I wonder why the Mk 57 PVLS is not used?
- the SPY-3 + VSR have 120 degrees angles instead of the 90 degrees of the SPY-1, so you only need 3 instead of the 4 drawn right now.
- nuclear ships are known to be quite a bit bigger then dinosaur powered vessels with the same systems.

in arrangement, she looks about right.

then, the parts. note that the steam turbines you have used are 1930's vintage, so I would look into newer ones. I have a set of gearing class turbines drawn which are slightly newer (PM me if you want them) but I do not know if it would be more usable.

seein the position of the aft turbine room and the electric engine room, I cannot see why you would not pu them in the same room, and maybe even directly couple one of the reactors. by putting the electrical engine to the gearbox you can run both shafts on one reactor or on the gas turbines, or deliver power to the onboard power network (IEP) with an shorter machinery setup.
the post you made later (after I started writing this) fixes that though, but keep it in mind

if we go a bit into handwavium, we can say that was the D2G developed further, it would have gotten more power out of the same size. that, and the fact that turbines got better due to computer aided design, we can assume 35000 shp at least, maybe even 40000 from each reactor.

the zumwalt has an immense amount of power available, but not all of its engines will be in operation all the time. if we look at an normal (non nuke) mission profile, we see that ships stay at low speeds quite a lot. in that view, I think that CONAG would not be that inefficient at all, as the gas turbines would only be started when required. it would make sense to have some smaller gas turbine and diesel sets as 'regular' ship service units for when the ship is not under propulsive power(or when at really slow speeds), so both the gas turbines and the reactors can be shut down if they are not needed.

a longer waterline might result in a lower required power as well, so I personally think you need the power of the zumwalt as a maximum, not a minimum. (the virginia had enough with the 2 D2G and the ship service generators, of course there was less power required for the systems back then but even so, doubling this amount seems excessive even 50 years later.



now, the ship design. you need to look at your mission profile. what speed will you be sailing on most of the time? that is what you optimise the hullform on, and this defines the length (hull speed)
this is reason one why DXGN (virginia) is so much longer then DXG (kidd) (the other is the displacement due to the weight of the reactors) you might end up with a bigger ship then the zumwalt if you want to go 30 knots all the time.
after you have determined that, the next problem comes alive. on first glance, there are maybe 4 or 5 heavy systems on board: the radars, the VLS, the gun, the reactors and the hull itself, for example. the hull itself has its center of gravity about midships, and you want the weight of your entire ship in about the same place, as that gives you an effective hull form. as the weight of your propulsion system will end up on about 25% of the entire ships weight in this case, and you have very little fluids on board you can stabilise the ship with, this determines the place of the reactors. you can separate them from each other, but the midpoint between them should be about midship.
the superstructure where your gas turbine is in should not neccecarely be as high as that where the radars are in. hell, those things are light and you can move them around in this case, so you can put them under the helideck if you want. do not ever let them be a hindrance for where you put your reactor acces channel.this might shorten your superstructure quite a bit too, so you might be able to be a bit more effective with your space. the width of the ship might make it possible to have PVLS next to the reactor spaces, if you want.

note that your freeboard looks quite high. lowering it one deck already gives you one less deck to move the reactor trough. that said, as long as your stability can take it, there is nothing wrong with more freeboard

_________________
Drawings are credited with J.Scholtens
I ask of you to prove me wrong. Not say I am wrong, but prove it, because then I will have learned something new.
Shipbucket Wiki admin