I'm perfectly aware that my English is far from perfect. Especially when I don't take my time writing posts... I'm still improving though.

Absolutely right. But as people already have said, the power/speed curve raised geometrically, so to get 90% of max speed you only need about 80% of max power. So power reserve can be significant, speed reserve is lower.
And CVs are so big than they don't lose much of energy fighting against waves, so the reserve don't have to be big.

The design speeds for CVNs are know: "The JFK was designed for 33.5 knots, the Kitty Hawks 33.6, the Forrestal 32.0 and the other CVs of that class were designed for 33.0. All had powertrain installations designed to provide 280,000 shp except Forrestal which had 260,000 shp. In all cases, the power was delivered via four shafts"

Now let's return to the "30kts at any time" requirement. If ship can make 30kts at 80% power output, then it can make about 33.5kts at 100% power. About right. And official max speeds of CVNs relased by Navy in June 1999
are:

Enterprise 33.6 knots after last refit
Nimitz 31.5 knots
Theodore Roosevelt 31.3 knots
Harry S Truman 30.9 knots

so in range of 31 to 33.5kts. All seems to be consistent. Only some CVNs from official relased figures (results of trial runs probably, like for Enterprise) seem to be slower than design speed which I believe to be rather common thing for weared ships :-)

But the best argument for me were not guessing how much of power or speed reserve should a ship have, but the simple fact that the propulsion of CVNs is almost identical to propulsion of previous CVs with exception of nuclear reactors (steam generators). Even if reactors are capable of producing more steam, CVN has same steam turbines as CVs with the same max power output, the rest like reducton gears, shafts, propellers are designed for the same power output like on CVs. In text Kurushio quoted, was said that CV construction was copied where only possible in CVN design.
To make CVN faster, to design more powerfull propulsion, would reqire either adding one shaft (so one steam turbine/reduction/ect.) or designing new more powerfull turbines ect. to get more horsepower with 4 sets. But exactly same thing could be done with conventional propulsion... if someone wanted more speed in exchange of usable loadout.
So it's extremally unlikely that CVN propulsion as a whole can deliver more horsepower than CV propulsion. Max speeds should be very similar. In fact maybe little lower, as CVNs tend to have higher displacement than CVs with the same length. There are other advantages of nuclear propulsion than just max speed.

Now when we got little bit over 33kts as highest design/achieved figure, then if there were torpedos in water and a run for your life, then maybe steam turbines and rest of gear can be overloaded by 10-15% or so - I don't know... probably we have some people here working with steam turbines who could say if you can overload them if there is steam available ? Is it technically possible to increase steam input above max designed power output ? If yes, then both CV and CVN probably could go 1-3kts faster risking machinery damage. But CV just as good as CVN :-). On the other hand, I would hardly name it max speed if achieved at over 100% of designed/safe power output...

Cheers!

Ok, Amizaur, so saying all this is correct....in Debt of Honour, they get a CVN going on 2 shafts and 30 knots. It actually says it can just about reach 30 knots on 2 shafts, which is the bare minimum to launch planes off it.... Yes, I know it's fiction...so...how fast do you think a CVN could do on 2 shafts?

p.s. Actually your English is very good...sorry mate, I was nitpicking.

I'm not sure what speed on two shafts. If we assume that two shafts can deliver just half of the power delivered by 4 shafts (and this is not quite sure... the screws have variable pitch but I'm not sure if turbine/screw combo could be less or maybe more efficient when trying to deliver full power at 2/3 of max speed...) the just looking at power/speed curve - which can vary somewhat from ideal V ~ P^2 in larger intervals too - it's quite safe to assume clean geometrical dependance with small intervals, because the possible error is smaller yet, with significant speed/power change the estimation error can be larger too... But assuming half of max power delivered by two shafts/screws and geometrical power/speed curve, then CVN on 50% of max power would get to 70% of it's max speed. So if it's normal max speed was 33.5kts, then on two shafts this should be around 23.7kts. With 15% overload this would be about 25.5kts. So you only need less than 10kts of wind (5-7ks) to get you 30kts and launch the planes... Of course the error in this estimation can be greater than previously, some assumptions were made...

And are you sure that you absolutely need 30kts of wind to launch planes ? I don't know much about carrier operations, but I would think that steam catapults could be overloaded a little too - or rather the planes can be given a kick stronger than usual, because the catapults can launch heavier planes than fighters.
You could launch a little lighter planes (less fuel and weapons) and launch them stronger than usuall... What's the speed of a fighter plane (relative to carrier) after launch ? I found it's 160mph in 2.5 seconds. That's about 140kts and 72m/s so acceleration would be around 3g at 90m distance.

Now if you are lacking 10kts in carrier speed and have to gain it on catapult launch. To get 150kts instead of normal 140kts on same 90m distance you'd need to accelerate the plane at 3.4g instead of normal 2.9-3.0g. About 16% greater acceleration, shouldn't affect the pilot much, plane should take it too, and to assure that forces on plane launching hook/structures not exceed max, you'd just need to launch plane at least 16% lighter than max carrier launch weight. The catapult power needed is only 16% greater too, or if the plane is lighter by 16% - required catapult power is exactly the same as normal.
I don't know if it's allowed to launch a plane stronger than usual, but from technical point of view shouldn't be problem. The structure of carrier based plane is designed most probably with at least 1.5 safety factor, so 16% more should be piece of cake. If you normally launch planes with 30kts wind, you should be able (from technical point of view) to launch them with 20kts wind too, with 16% more G and 16% structure overload or using 16% lighter launch weight. If it is a used procedure or maybe it's not possible for some reason - I have no idea...

No idea what the speed should be to launch an aircraft off a carrier...my book "Carrier" is somewhere else and it's been yonks since I've read it. Somebody have the info at hand?

I never said it could only do 30kts. I said they could not sustain 40kts. The actual top end of most CVNs is betweeen 32kts and 36kts.

We've moved on to the speed planes are launched off flat-tops. We've pretty much established nobody really knows what the actual top speed of a CVN is. ;)

Sure people know. Iknow exactly what it is, I'm just not willing to say.

I was fortunate enough to be the Intel custodian on an LA class sub. You would be suprised how much info is in the Intel books a nuclear sub has(coincidentley we had special Janes as well) and I am a bit of a bookworm. Our captain took great pleasure in quizing me on shipborne sensors and capabilties data all the time. After my Senior Chief challenged him to once. This secured my position as the on-call ESM/EW watchstanders, much to the dismay of a couple higher ranked shipmates who desired the post. Given the infrequency of LA classes going to PD, this was a very prized watch:D. It could backfire on you as well, if some event caused a prolonged PD period.:damn:

Anyways, back on topic. I don't recall any data about launch speed for the planes, and I certainly don't know how much they could be safely operated outside prescribed metrics for operations. Nor do I know how much the propulsion system could be operated outside approved safe operating limits.

The Navy doesn't give much leadway to operating nuclear power plants outside guidelines. Sometimes doing so can be very costly because if it happens massive inspections are automatically required. I know of one instance that reduction gears had to be put through some very difficult examination do to an accidental event and it cost a bunch and asses were eaten aggressively.

The only time I ever witnessed operations outside guidelines that didn't cause a big rucuss or mandatory inspections was when Admiral Rickover was onboard and the operations were on his orders. They were his Nuclear vessels after all:rock::rotfl:

Just to chime in here on the speed of CVN vs CV's. One thing you all seem to be forgetting is ships LOADING. With a CV you have to carry a LOT of fuel onboard for yourself and for your planes. This is a ratio of how much room vs how fast vs operation capabilities. This affects your propulsion plant design sigificantly.

For those of you wondering about overloading a steam plant it is possible. With a conventional superheated steam plant you have to worry about your feed rates and % of superheat (I presume that a CVN is a superheated steam plant with gives you a MUCH higher thermal efficiency than a saturated steam plant). If you pull too much steam thru the those boilers then you have many many bad things happen. More than I can tell you without giving a weeks long lecture on boiler plant/steam plant design and operations. Lets just say that it is BAD. Also, if they DO use superheated steam (and I think they do. Any CV sailors out there??) then the plants are TOTALLY different in operation and can not be compared.

add: I just found out that the USS Kennedy (CV-67) used a 1200 pound steamplant so YES, the conventional ones ARE using superheated steam.

With a nuclear plant you are limited by your feed rate to the steam generators and the amount of carryover that you want to live with in an oversteam situation. Like someone said earlier, it triggers MASSIVE inspections and visits from NAVSEA08 asking the C.O. WHY he saw fit to exceed safe operating guidelines.

Just how much speed can you gain by breaking these rules??? Well.. it is a matter of conjecture and theory. More I can not say.

Interesting. I've got another Clancy quote for you to all ponder...and I know I might get slaughtered for this one too, but oh well. I remember in his book (and I remember it because it stood out) Clancy says "...the only reason other nations besides the US do not have catapult launched carriers is because the catapult arm can only be manufactured in the US, no other nation has such a facility to make one". Now, I must admit, this is one "fact" I was a bit dubious on, because think about it...other nations can build the world's longest bridge (Japan), the worlds tallest building (Canada) and the worlds biggest plane (France)...yet they can't make a catapult arm?

Saying that, the book is now ten years old and France make the Airbus A380 in different parts of the country as opposed to Boeing which makes them all under one roof. So who knows...:hmm:

I think it is just that no one had put in the necessary effort. Considering the Americans had been bilding those things for decades, there's almost certainly nothing difficult technologically. But engineering is funny that way. We all know what the big problems are, so you can guess another guy's capability even if you never made one quite well, but if you hadn't been building them, it'd take a real effort to get started - countless tiny problems to solve.

What I never really understood was the Soviet's reluctance to build one. Yes, it is unlikely they can match the US' fleet of them. But a full size carrier allows for power projection and real air defense. One would think they should at least have built 3-6, allowing them to exert influence when necessary.

Those Soviet admirals who actually thought that a V/TOL carrier is superior in "cost-effectiveness" needs to have their brains checked. Even if they decided on 40000 ton instead of 80000 ton carriers, for 40000 tons you can still have a real aircraft carrier if you would just put those missiles somewhere else (like under the hull), added a catapult and maybe improve things further with a ski-jump. That will give you a real air defense capability.

Oh yes, and I just remembered. He stated that when France were using catapult launched carriers (before the De Gaul), the catapults were made by the US because France could not make them. That's why they got tired and later went with V/Stol...just like the Brits....

Wow, this discussion is getting interesting. While of course it's all theoretical, I hope everyone is enjoying it as much as me!
A few comments, if I may.
1. Helos are routinely used to take "cover shots" of ships at sea- where do ya think all those snazzy pics come from?:D
2. Helos routinely fly at "slow" speeds. The "10 at 10" maneuver is when the pilot is feeling nice, and allows the recue swimmer to deploy at 10kts, 10feet of altitude. If he was off by 5-10 kts, I would know about it pretty damn soon!
Also, when landing aboard the smaller ships (ie ffg/ddg) we "pace" the ship on final approach, which is often quite a bit slower than 36kts :p. Usually 12 kts or less.
Therefore, the comments questioning the accuracy of the helo's instruments to measure speed are incorrect, in my opinion.
3. I agree, there is no way to know how much ocean current there was, but in my experience, in the open ocean, there is little effect of currents at the surface in excess of 3 kts. Maybe it's worse deeper, but I never went that deep :) The location was East of Pearl Harbor, if I remember correctly. Water was warm, I remember for sure!
Also, we have GPS for speed/postion fixes in addition to the "KIAS", so there are 2 different measurements- 1 is the relative movement through the air (usually a pitot tube), which is affected by air currents; the other is movement relative to the ground. As you all know, in stormy weather we may have 130 kias showing, but GPS will show maybe 100 kts. These will often be different. The older autopilots we had (sh-60b and f) had alot of trouble maintaining a hover, but I understand that the newer blocks, and "R" variant have improved avionics.
I don't know which one the co-pilot was referring to when he said the ship's speed was about 36kts. There isn't a seperate gauge at the senso station, so I couldn't tell ya.
I never spent much time below decks on the CVN- I doubt I went below the mess deck to be honest. Too messy for us little airdales. So all this information is new to me. I never gave much thought the inner workings of the ship. Never did find that bowling alley either...
But I would highly suspect that a CVN is capable of speeds around 35 kts.

I'll go with Swimsalot! :up::rock:

Well, from what I know, a steam catapult on board a CV can generate significantly more force than is required to get at least most aircraft off the deck of the carrier.

Carriers need to be able to move to LAND the planes, not shoot them.

If I remember my father correctly (he was the DIV-O of the catapult's on a CVN btw) the criteria was to be able to shoot a max loaded airplane to a minimum flying speed in a zero wind over the flight deck situation. He did add that is was a rather unpleasant sensation as he had done it before in A-6's. It is not too healthy for the planes either.