Aircraft carrier acceleration

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  • #1
Pengwuino
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Main Question or Discussion Point

Does anyone know what kind of time it takes for an aircraft carrie to reach full speed if it starts from rest? Specifically a nuclear powered US carrier (nimitz maybe?). Someone said it takes 5 hours and im just having a hard time believing it.
 

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  • #2
FredGarvin
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Most things like that are classified. Details like top speed, range, etc... are pretty closely held secrets. I know when my brother was on the Eisenhower (CVN-69) they would tell you very little.
 
  • #3
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Pengwuino said:
Does anyone know what kind of time it takes for an aircraft carrie to reach full speed if it starts from rest? Specifically a nuclear powered US carrier (nimitz maybe?). Someone said it takes 5 hours and im just having a hard time believing it.
I don't know what full speed is and very few people really do, but I have a few years of my life spent on a couple different ships and I am positive that five hours is crazy. I think maybe 20 minutes or so. I have never timed it but they can go from 35 knots to a dead stop, go in reverse, then get back up to 35 knots in about half and hour...thats just a guess but it really does not take too long IIRC.

Regards
 
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The speed on the placard always went black after about (not sure I should say, insert your guess here) knots or so...but I can assure you, the ship continued to accelerate for a while.
 
  • #5
brewnog
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These boats are pretty big, approaching 90,000 tonnes. I wouldn't be at all surprised if it took a couple of hours to go from standstill to full pelt, although 5 hours does seem a little on the large side, even compared with oil tankers.
 
  • #6
Astronuc
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brewnog said:
These boats are pretty big, approaching 90,000 tonnes. I wouldn't be at all surprised if it took a couple of hours to go from standstill to full pelt, although 5 hours does seem a little on the large side, even compared with oil tankers.
You'd be surprised! :rolleyes:

Oil tankers are designed differently - very different hull shape.

One has to consider thrust (shaft power) to mass, and hydraulic resistance.
 
  • #7
brewnog
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Astronuc said:
You'd be surprised! :rolleyes:

Oil tankers are designed differently - very different hull shape.

One has to consider thrust (shaft power) to mass, and hydraulic resistance.
Of course, I was only thinking of orders of magnitude to see if it sounded realistic.

What do you reckon anyway?
 
  • #8
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Pengwuino said:
Does anyone know what kind of time it takes for an aircraft carrie to reach full speed if it starts from rest? Specifically a nuclear powered US carrier (nimitz maybe?). Someone said it takes 5 hours and im just having a hard time believing it.
Oh Nimitz?

It's currently docking in my country!
 
  • #9
brewnog
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darkar said:
Oh Nimitz?

It's currently docking in my country!

Fantastic. Go and see if you can take her for a spin.

Don't forget your stop watch.
 
  • #10
russ_watters
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Townsend said:
I don't know what full speed is and very few people really do, but I have a few years of my life spent on a couple different ships and I am positive that five hours is crazy. I think maybe 20 minutes or so. I have never timed it but they can go from 35 knots to a dead stop, go in reverse, then get back up to 35 knots in about half and hour...thats just a guess but it really does not take too long IIRC.

Regards
I'm not sure of the exact time either, but I was going to guess about 10 minutes.

The thing about nuclear carriers is they always have their reactors running near full capacity because it does take so long to start one (days?). As a result, bringing the power turbines up to full is mostly a matter of opening a few steam valves.
 
  • #11
Astronuc
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As for the performance of nuclear naval vessels - those who know, do not say, and those who say do not know. Anyone who knows the performance of nuclear vessels and the details of the nuclear reactor and fuel is obligated not to discuss such information - and more so since Sept. 11.

I'll post a picture later as to the performance of a nuclear carrier.
 
  • #12
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A pic is weak...

Do a search for a video of carrier quals...I can't seem to find one on the net but I have seen many for training purposes and what not.

Also, the Admiral will usually pick the fastest ship in the fleet for his flag ship. On my last west pac the Admiral was on our ship, USS Carl Vinson CVN 70. On our way out of Hawaii all the ships were bolting out at full steam, we won easily to say the least.

EDIT: I wonder what the Ronald Regan is capable of??? We can only speculate.
 
  • #13
Integral
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The top speed of an air craft carrier (or any ship for that matter) is determined by many factors. How the steam is generated is just one, and perhaps one of the less significant factors that determine top speed. Screw design and hull shape may be more critical, in that respect the nuc carriers are identical to the last remaining conventional Carrier, the USS JFK. I would bet that there is little difference in the top speed of the Kennedy and say the Enterprise, which is of the same generation and very similar design.

I served aboard the JFK for 2 years ('71-'73) so am a little bit familiar with the operations of a carrier. First of all I do not recall much concern about doing a "dragster" race to top speed. It is very rare for a carrier to come to a full stop in the open sea. I only saw it once or twice in the time I was aboard (btw, of the 24 months I was aboard we spent 15months deployed to the Med. so I did spend significant time at sea!) When we did get under way from a dead stop I would guess we were at cruising speed (somewhere around 20kts ) in about 10 min. It should be well known that a carrier (any modern carrier) can do 30kts with out breaking a sweat. During air ops we cruised into the wind to give the planes 30kt of airspeed, we could create a 30kt wind if needed. Further an aircraft carrier can do 30kts in any sea condition short of a full hurricane. One of our high speed runs occurred as we were leaving the North Atlantic in heavy sea conditions, the Capitan tired of the Russian cruiser tailing us. He cranked it up and walked away leaving the poor cruiser and our destroyer escorts far behind, fighting the 10ft + seas. During the high speed runs you could feel the whole ship vibrating and the decks became noticeably warmer as they probably had to bring additional boilers on line to maintain the speed. Once again from cruising to top speed took another 10-15min. So my guess for a dead stop to top speed would be more like 20-30min. I do not think that the source of the steam will have a tremendous effect on this, since the hull shape and drive trains from turbine to screw are nearly identical.

As a side note, while aboard the Kennedy I served with a fellow who in civilian life was a mechanical engineer working for the Newport News ship yards, he had been working on the USS Nimitz before joining us. It seems that the common design tactic was to go to the drawings for the Kennedy and simply copy them when ever possible.

Now if you are talking from a cold ship start to top speed perhaps the nucs would have an advantage. but that is not a very realistic condtion as the only time that the JFK went cold was when it went into the yards for refurb. The boilers are always on, generating, if nothing else, electricity and water (fresh and hot).
 
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  • #14
Astronuc
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Fast carrier. :biggrin:

CVN-68 Nimitz, which I've seen numerous times in San Diego, Calif.

From the public domain -
The carrier's two nuclear reactors give her virtually unlimited range and endurance and a top speed in excess of 30 knots (that's the best you'll see - :biggrin: ). Eight steam turbine generators each produce 8,000 kilowatts of electrical power, enough to serve a small city. The ship has enough electrical generating power to supply electricity to a city of 100,000. The ships normally carrys enough food and supplies to operate for 90 days. Four distilling units enable NIMITZ-class engineers to make over 400,000 gallons of fresh water from seawater a day, for use by the propulsion plants, catapults and crew. The ship carries approximately 3 million gallons of fuel for her aircraft and escorts, and enough weapons and stores for extended operations without replenishment. These ships also have extensive repair capabilities, including a fully equipped Aircraft Intermediate Maintenance Department, a micro-miniature electronics repair shop, and numerous ship repair shops. Keeping a NIMITZ-class carrier ready at all times requires repair shops to maintain machinery and aircraft, heavy duty tailor shops to repair parachutes and other survival gear, and electronic ships that keep communication, navigation and avionics equipment in good condition. NIMITZ-class carriers boast all the amenities that would be found in any American city with a comparable population, including a post office with its own ZIP code, TV and radio stations, a newspaper, a fire department, a library, a hospital, a general store, two barbershops and much more.
 

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  • #15
Pengwuino
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So are we rather agreed upon the idea that 5 hours is way off base?
 
  • #16
When I was probably about 15 I took a tour on a ship. They were showing us the gatling guns mounted up front and told us that they were capable of tracking and shooting at incoming targets on an automated system. So I asked what sort of reaction time they had and they laughed at me. :redface:
 
  • #17
FredGarvin
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I saw video of the Ronald Regan going thru sea trials. The coolest thing I have ever seen was the test that is probably what Astro just posted. It was a test of being able to turn at a certain speed and radius. They showed from two different vantage points; the air and on the deck. From the deck you would have sworn it was at a 45° slant. To see a ship that big do that was incredible.
 
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FredGarvin said:
From the deck you would have sworn it was at a 45° slant. To see a ship that big do that was incredible.
My very first west pac was on the Kitty Hawk, the last conventional carrier. When pulling into Hobart Tasmania, Australia there were sea swells that we so big that I was literally walking on the bulkhead and the deck at the same time. All the birds had to be 24 pointed and all the hangar bay doors were shut. Everyone I knew, I was on nights, that was day crew either slept like a baby or fell out of their racks and some were hurt pretty bad.

Sometime you would see the small boys a rockin and rollin but never before in my life have I ever seen a ship the size of a carrier sitting nearly on its side. Some of the waves would even break over the top of the flight deck. :bugeye:
In any case it made for an interesting night and and easy one since there was no real work that could be done under the circumstances.

Ok, I am done, no more sea stories for you landlubbers...

Regards
 
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  • #19
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FredGarvin said:
I saw video of the Ronald Regan going thru sea trials. The coolest thing I have ever seen was the test that is probably what Astro just posted. It was a test of being able to turn at a certain speed and radius. They showed from two different vantage points; the air and on the deck. From the deck you would have sworn it was at a 45° slant. To see a ship that big do that was incredible.

Oh and one last thing, those "test" are called carrier quals..

Every carrier has to pass them from time to time. They are not just testing the carrier but the crew as well.
 
  • #20
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The discussion boils down to how Flank is defined. My experience(chasing a target) is they can go from zero to a few knots short of X in a matter of minutes and slowly creep up to X. The problem with the definition comes from the ability of the powerplant to minimize an iodine/xenon transient. Daughter partical decay transients can take hours ands hours so the ship may not reach flank until the transients have subsided(in all reactors used to power the screws), but these big huge targets are increadibly nimble to say the least. 30 minutes is a bit long IIRC but close.

[edit]A bit of correction, the ship can reach flank in minutes but may have to wait for the daughter particle transients to subside before reaching the absolute top speed possible which could actually take 5 hours. The difference in speed is nominal though.
 
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  • #21
Integral
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Townsend said:
My very first west pac was on the Kitty Hawk, the last conventional carrier.
As I mentioned above, the JFK, is sitll commissioned, it is the last conventional carrier.
 
  • #22
FredGarvin
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Townsend said:
Oh and one last thing, those "test" are called carrier quals..

Every carrier has to pass them from time to time. They are not just testing the carrier but the crew as well.
Actually, this round of tests I saw was not carrier quals. It was the official acceptance testing that the Navy was conducting before accepting the carrier from the Newport News shipyards. The ship was brand new. It consisited of a skeleton Navy crew and a lot of ship builders. It came off to me that the tests they did there were different than the ones for a regular deployment work up.
 
  • #23
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FredGarvin said:
Actually, this round of tests I saw was not carrier quals. It was the official acceptance testing that the Navy was conducting before accepting the carrier from the Newport News shipyards. The ship was brand new. It consisited of a skeleton Navy crew and a lot of ship builders. It came off to me that the tests they did there were different than the ones for a regular deployment work up.
Maybe, I am unfamiliar with commisioning of ships but I doubt it could be much more intense than carrier quals. Perhaps they just test different things but like I said I really don't know anything about it.
 
  • #24
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Integral said:
As I mentioned above, the JFK, is sitll commissioned, it is the last conventional carrier.
I guess it is still commissioned (I did not even know about it) but it is not the last conventional carrier as the Kitty Hawk is in Japan IIRC, unless of course something has changed in the last two years I don't know about, and it is still commissioned.

I don't know how long they plan on keeping these conventional carriers around but for a lot of the worlds ports you cannot pull in if you are running on a nuclear reactor. That makes up most of the carrier fleet. For any of the CVNs you have to stay out to sea about a mile or so and ride ferries into port. It really sucks cause sailors just want to get off the dame thing but they have to wait in line forever just to catch a ride on a little dingy used for hauling cattle. Then of course on the last night of port call everyone is lit up like a christmas tree and has to wait to get on a small ferry back to the ship. You cannot imagine what its like being shore patrol in a situation like that... :cry:

Anyways, thanks for correcting me there Integral. I wonder, is the indy still in service? I will have to check that out.

Regards
 
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  • #25
Integral
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Townsend said:
I guess it is still commissioned (I did not even know about it) but it is not the last conventional carrier as the Kitty Hawk is in Japan IIRC, unless of course something has changed in the last two years I don't know about, and it is still commissioned.
Ok, I just checked on it you are correct, there are 2 conventional left.
I don't know how long they plan on keeping these conventional carriers around but for a lot of the worlds ports you cannot pull in if you are running on a nuclear reactor. That makes up most of the carrier fleet.
IIRC the main difference between a conventional and a Nuc was that the conventional needed a extra couple of fuel lines for ships fuel during an unRep. The nucs still had to take on aviation fuel and supplies.
For any of the CVNs you have to stay out to sea about a mile or so and ride ferries into port. It really sucks cause sailors just want to get off the dame thing but they have to wait in line forever just to catch a ride on a little dingy used for hauling cattle. Then of course on the last night of port call everyone is lit up like a christmas tree and has to wait to get on a small ferry back to the ship. You cannot imagine what its like being shore patrol in a situation like that... :cry:
Sure I can :biggrin: Been there done that! I remember once that a storm came up while I was ashore (Izmir, Turkey) , they were running a "test" boat back to the ship to see if they could make it. They were looking for volunteers to ride it back. I wanted to get back to my bunk so went along. It was quite a ride, were were in a 50' motor whale boat with a canvas cover, so stayed pretty dry... most of us any way... at one point we took a wave over the bow and the canvas opened up, it looked like some one dumped a 50 gal barrel of water on the poor fellow setting under it.

The fun part was getting onto the fantail latter with the small liberty boat bouncing on the sea while the carrier was nearly stationary. You had to time the step just right. Not always easy after a night of drinking ashore!

Anyways, thanks for correcting me there Integral. I wonder, is the Indy still in service? I will have to check that out.

Regards
The Indy as been decommissioned, believe it or not, they sank the America, doing survivability testing!
 
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