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Aircraft carrier acceleration

  1. Jul 5, 2005 #1

    Pengwuino

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    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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  3. Jul 5, 2005 #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.
     
  4. Jul 5, 2005 #3
    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
     
  5. Jul 5, 2005 #4
    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.
     
  6. Jul 5, 2005 #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.
     
  7. Jul 5, 2005 #6

    Astronuc

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    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.
     
  8. Jul 5, 2005 #7

    brewnog

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    Of course, I was only thinking of orders of magnitude to see if it sounded realistic.

    What do you reckon anyway?
     
  9. Jul 5, 2005 #8
    Oh Nimitz?

    It's currently docking in my country!
     
  10. Jul 5, 2005 #9

    brewnog

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

    Don't forget your stop watch.
     
  11. Jul 5, 2005 #10

    russ_watters

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    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.
     
  12. Jul 5, 2005 #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.
     
  13. Jul 5, 2005 #12
    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.
     
  14. Jul 5, 2005 #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).
     
    Last edited: Jul 5, 2005
  15. Jul 5, 2005 #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 -
     

    Attached Files:

  16. Jul 5, 2005 #15

    Pengwuino

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    So are we rather agreed upon the idea that 5 hours is way off base?
     
  17. Jul 5, 2005 #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:
     
  18. Jul 6, 2005 #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.
     
  19. Jul 6, 2005 #18
    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
     
    Last edited: Jul 6, 2005
  20. Jul 6, 2005 #19

    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.
     
  21. Jul 6, 2005 #20
    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.
     
    Last edited: Jul 6, 2005
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