My own experience with a Nimitz class Attack Aircraft Carrier’s top speed could be summed up in two examples:
We performed a Kiss/Cross maneuver when it was believed a crew member fell overboard during a Tiger Cruise. All crew accounted for.
B) Returning from WESPAC. All flight squadrons depart to nearest base prior to CVN arrival in port. We unloaded the rest of the Airwing personnel when we dropped anchor. IIRC, we sounded Sea and Anchor at around 1300; we were probably not haze grey/underway until 1530.
We were at our home port the next morning.
Kinda like driving from San Diego to San Francisco.
I was a submarine officer in the Navy – we had mostly the same nuclear training that carrier nukes had. I never served on a carrier, but the stories from training and from senior sailors about speed records and such were usually about the USS Enterprise, not Nimitz class ships. Enterprise had a whopping eight nuclear reactors – late in its career, some of those reactors were permanently shut down, but early on, the stories went, if all of the reactors were operating, Enterprise could go in excess of 40 or 50 knots.
I’m still rather skeptical, but such stories were commonplace among submarine sailors. Incidentally, the stories of submarine speed records were about the USS Seawolf (I served on a 688 class), which supposedly could outrun the fastest Soviet submarines (including a liquid-metal cooled experimental sub that could go 48 knots, supposedly). I’m skeptical of these claims too.
Not much faster than 20 knots, at least as I recall from the olden days (1980s) when I was on the Enterprise (CVN-65).
For fixed wing flight operations, the course (Fox Corpen) and speed was calculated to have 25 knots of wind 5 degrees to port over the flight deck. If there was no wind, we could go in any direction at about 23 knots to get 25 knots of wind.
Nuke power means never having to try to save fuel
I can neither confirm nor deny that the story I was told actually happened (I wasn’t there) but it makes sense that it could be done.
The Enterprise had completed an overhaul and part of the testing involved high-speed runs. During those runs the pitometer/pit sword used the measure the ship’s speed was retracted as several locations throughout the ship received the information but it wasn’t necessary for personnel to know it.
I stood watches in the Surface Module of what was called the Combat Information Center (CIC). One of the Operations Specialists petty officers who stood watch in Surface during the high-speed runs told me how they calculated the speeds during the runs: they chose a fixed point on the shore and took a range and bearing to that point and did so every 3 minutes and from that could calculate how far the ship had travelled over time, which could be expressed in speed (old salts will recognize that as Maneuvering Board 101). With the electronics and GPS today, I expect it’s all done at a computer console now.
And finally, I honestly don’t recall the top speed I was told but it was “in excess of 30 knots” tho as stated above, we could conduct flight operations as long as we had 25 knots of wind 5 degrees to port over the flight deck.
I don’t doubt it. But you/the destroyer were maneuvering for a position relative on the carrier (when in plane guard duty) or both ships were transiting to a certain location to arrive at a certain time, which required a certain speed.
If ship A is 10 miles astern of ship B and both are steaming at 20 knots, ship A will never close to 5 miles astern of ship B unless ship A increases her speed above 20 knots (Relative motion! 30 years later it’s all coming back to me!).
Fuel is factored in, many people are paying attention to that at all times (remember the Fuel, Oil & Water Report that went to the Captain with the 12 o’clock Reports?). I’m sure you remember underway replenishments to receive fuel from a CV/CVN, I was in Deck Dept and I remember sending it to destroyers.
I was addressing the speed needed to conduct fixed-wing flight operation (25 knots of relative wind over the deck) which is the same for a CVN, CV or a sail-powerd aircraft carrier (helicopters don’t care so much).
The classic form of dry dock, properly known as graving dock, is a narrow basin, usually made of earthen berms and concrete, closed by gates or by a caisson, into which a vessel may be floated and the water pumped out, leaving the vessel supported on blocks.
As for “running away from the escorts”, it’s a bit of hyperbole. Carrier groups don’t bunch up like in the top picturein the Wikipedia article except for photo ops – in fighting shape they’re spread out over an area the size of the Eastern seaboard*, with individual ships maybe close enough to each other to see the nearest one on the horizon (read the linked article for specifics).
So if the wind were to change and the carrier had to pour on the power to continue flight ops, it would appear to accelerate rather quickly to sailors on any ship that could see it, but wouldn’t move much from the center of the hundred-square-mile box formed by its closest escorts.
To put that in perspective, let’s say the carrier is in DC. The lead surface ships are out around Philadelphia, air coverage extends to NYC, and the attached submarines are sneaking around as far out as Boston.
I see this post has been going on for a very long time. As a naval architect I wanted to chime in and offer some insight on vessel speed. One of the first posts mentioned a formula for the speed of displacement vessels 1.34 (waterline length)^1/2. This formula is a rule of thumb that does work for ships.
The longer a vessel is the faster it can go, at least in theory. When a ship goes fast enough that it creates a wave along its length, like a sine wave, it has reached “hull speed”. To go faster you the boat must plane. You still need the required power to achieve hull speed and we assume the propellers are properly designed for an optimum speed.
The displacement of a ship is how much it weights. The Displacement to Length Ratio is the first thing to calculate in isolating hull speed. DL Ratio = Displacement / (0.01 WL)^3 . The unit for displacement is Long Tons, 1 Long Ton = 2240-lbs. The Waterline Length, WL, is measured in feet.
The Speed to Length Ratio is the 1.34 in our rule of thumb. For a given vessel its SL Ratio = 8.26 / (DL Ratio)^0.311
The maximum possible hull speed in knots is our rule of thumb formula. Knots = SL Ratio (WL)^0.5
So maximum speed using the rule of thumb formula is really based on waterline length and the weight of the ship. Its still a best guess; but, an educated guess. I ran the numbers for my old ship, USS America, using information found online. I got a speed we never achieved. Checking further it would require 1.36 million horsepower to reach the speed projected. The installed power on the ship of 280,000-hp provides a maximum speed of 39-knots.
In very broad laymen’s terms perhaps the steam turbines ‘the same’ but a marine engineer wouldn’t say so. The significant difference is that the turbines on old conventionally powered carriers were designed to take superheated steam, that is steam heated in the boilers to above the saturation temperature, the temperature at which water boils at the boiler’s pressure (which was ~1200 psi in those ships). The steam in a nuclear ship is generated by pressurized hot water, the so called primary loop, water in turn heated by nuclear reaction. No superheat, and lower pressure. Thus the nuclear ship’s turbines are bigger and heavier for a given power output.
And this is among the reasons why ‘30+ knots’ as top speed for the Nimitz and improved Nimitz class ships probably does only mean around 31 kts, whereas the last of the USN CV’s (oil fired carriers) had design speeds a few knots higher. The later ships are bigger, and their power plants are bigger and heavier for a given horsepower, both because reactors of a given output are heavier than oil fired boilers, and as above the turbines are bigger and heavier for a given output also. The nuclear ship has the advantage of not having to carry ship’s own oil fuel, but one of the whole ideas is to use that advantage to carry more fuel instead for the embarked a/c and/or oil fired escorts. And also fuel fits into almost any space, machinery takes up more prime space in the ship.
So there’s no obvious reason the designers would allocate more weight to the machinery plant of a CVN to have it exceed the speed of a CV, and apparently the design choice was to let the top speed be a bit lower: 31kts was judged fast enough. As mentioned, oil fired escorts burn too much fuel at such speeds to maintain them for long, and weather is less likely to permit it for a smaller ship also. And even back when it was planned to have lots of nuclear powered escorts for the CVN’s, there’s just no particular tactical reason to go say 35kts rather than 31 which would justify all that extra machinery size and weight.
There was a discussion of ‘hull speed’ but this tends to miss the point. So called ‘hull speed’ can be thought of as the point at which the normal rule of thumb of speed v power breaks down. But that rule of thumb is that power increases as the cube of speed. Thus roughly it requires 44% more power to go 35kts than 31, assuming the ‘hull speed’ is somewhat greater than 35. Again, there’s just isn’t a good enough reason to devote that much extra space, weight and cost. The 31-ish figures, which have been given also by experts like Norman Friedman, are credible IMO.
IME (as professional operating and design marine engineer on commercial ships, in one past career) this kind of speed exaggeration is also common on fast merchant ships, such as very fast container ships or the liner SS United States*. Some people will also say these ships could go several to 10 or more (the less well informed the person, the bigger the exaggeration) kts faster than their real speeds. It’s a lack of understanding the speed/power relationship and the design constraints. The numbers past mid-30’s kts for CVN speeds are just sea stories. It’s not inconceivable the CVN’s could have top speeds like 33 or 34 kts like the CV’s, but it’s completely believable it’s actually lower, more like 31.
*which did achieve a remarkable 39kts on trials, so it’s certainly possible for a large ship to be that fast, but exaggerated stories put it much higher.
