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Subject: Most Efficient Carrier Size
Roman    3/2/2004 12:57:47 PM
It is often said that the bigger the Aircraft Carrier the more efficient it is, but I suspect that only works up to a point and in any case it may be preferable to have more smaller hulls to be able to deploy them in more places simultaneously. So what is the most efficient size of an Aircraft Carrier? Do you think Aircraft Carriers larger than the Nimitz would see further gains in efficiency?
 
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Hugin    RE:Most Efficient Carrier Size   3/3/2004 3:19:46 PM
Quote: "So what is the most efficient size of an Aircraft Carrier?" Depends on what you mean by "efficient" and how you define "size". Efficient doing what? Is sixe defined purely by how many tonnes of water the vessel displaces, the size of the flightdeck or in terms of how many $ has been thrown at the ship(cost of ownership). Personally, I'm convinced the last definition of size(more specifically; the size of the budget) is the only definition of "size" that makes any sense. So you'd have to compare the budget with what you want the vessel to do. What do you want your "efficient" carrier to do?
 
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Hugin    RE:Mark F   3/3/2004 3:31:18 PM
Quote: "The USN has studied this question repeatedly and keeps coming back to the same solution - something about the size of a Nimitz is the most cost-effective." I do not know if or how often the USN has studied this exact issue, but if they have ever studied it, it should be obvious to everyone it's a study designed to arrive at a predetermined result, namely that more of what the navy already knows and feels comfortable with is the "best" option. I wouldn't assign any "carrieir efficiency" studies done by the navy ANY relevance at all. It's like asking a pawnbroker for advice on the best way to raise cash if you are short of money. Quote: "From a cost effectiveness standpoint, bigger is better when it comes to carriers." You dodge the real issue! How do you define "bigger"?
 
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Mark F    RE:Mark F   3/3/2004 9:25:30 PM
"I do not know if or how often the USN has studied this exact issue, but if they have ever studied it, it should be obvious to everyone it's a study designed to arrive at a predetermined result, namely that more of what the navy already knows and feels comfortable with is the "best" option. I wouldn't assign any "carrieir efficiency" studies done by the navy ANY relevance at all. It's like asking a pawnbroker for advice on the best way to raise cash if you are short of money." What nonsense! Is this your opinion based on personal bias or do you have evidence to back up your claim that the Navy falsifies these studies? The idea that carrier designers, or the Navy or some other unseen, unamed secret entity have for decades been secretly conspiring against the real advantages of smaller carriers is as persistant as the idea that similar entities have conspired to kill the FAC. Problem with conspiracy theories like this is there is no need for such a secret entity to knock down these ideas. They loose on their merits. Instead of bias and rhetoric, maybe it would be helpful to look at emperical examples. The only practical reason anyone seems to come up with for smaller carriers is to reduce individual unit cost. They can't be justified on operational grounds. Their political cost is the same as a full-bore supercarrier yet smaller carriers always end up as small, slow, second-rate carriers lacking flexibility, striking power and staying power. Reducing unit cost is a fine goal, but at what price? The immense size of the current crop of American carriers was driven by the need to launch and recover 100,000 lb nuclear strike aircraft, not by some phallic need for a really big stick. In other words, carrier size was determined the old fashioned way, by defining a mission. Such aircraft are no longer in the inventory but the ships that were designed to carry them of course exist to this day, their size proving useful for other reasons. Attempts by the USN in the modern era to build smaller, cheaper carriers start in the late 1950's when the staggering cost of CVAN 65 USS Enterprise was beginning to be appreciated. One attempt to reduce her size (and cost) resulted in a ship 25ft shorter and 5,000 tons lighter at full load that had to omit ALL side protection to accomplish a savings of $5m out of a total projected cost of $314m. Not really worth it. An attempt to design a smaller, more affordable CVN in 1960 resulted in a ship almost 200ft shorter than CVAN65 and of about 60,000 vs. 85,000 tons. It sacrificed 2.5ft of hangar height, could only handle an aircraft of up to 50,000lb vs. 80,000lb and had a total capacity of 750 vs 1,347 tons of aircraft. It sacrificed half the catapults and elevators, and on half the propulsion plant could not make the 30 knots deemed the minimum acceptable speed for a carrier at the time. It could carry 75% of the aviation fuel of Enterprise and 90% of the ordnance so could thus sustain operations for a similar period of time, but in no way could she come close to the intensity of operations provided by Enterprise. The reduced cost did not offset the dramatically reduced capability. A smaller, "minimum carrier" studied at the same time would have been 34,700 tons (roughly Essex sized but shorter and beamier) capable of carrying out a single air strike with 600 tons of aircraft. This ship could just make 30 knots using an oil-burning plant and had 1/5 the aviation fuel capacity of Enterprise and no torpedo protection at all. It was a disposable ship, and not much of a bargain. The next attempt at a smaller, cheaper follow-on to Enterprise tried to take advantage of a projected family of more efficient reactors. Slightly smaller than a Forrestal, design 58A had 80% of Enterprises aviation fuel capacity and 3 elevators instead of the 4 of Enterprise. Protection standards would have been maintained. Aircraft capacity was 1,125 tons for 78 aircraft vs the 1,347 tons and 99 aircraft of Enterprise. Hangar height was reduced by 3ft. It would have had the same radars and Terrier air defense system then being projected for Enterprise. Cost would have been $291m vs. $314m for Enterprise. Inreasing length by 40ft would have added another $8m to the cost. Neither design could have sustained 30 knots with the 4 projected reactors. A 3 reactor version would have been cheaper at only $242m but it was even slower. All 3 compared poorly to an Enterprise on a cost vs. capability basis. The very small difference in cost did not make up for the much larger difference in capability. The most practical cheaper alternative to CVN 65 without giving up capability ended up being a return to the oil-fired Forrestal design. The next big attempt at smaller carriers came in the 1970's, pushed by people like Admiral Zumwalt. CVV was the major program, an outgrowth of Zumwalt's earlier T-CBL, proposed by Ford and championed by Carter. It would have b
 
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Roman    RE:Mark F   3/4/2004 1:44:48 AM
Mark F, that was one amazingly excellent post. I think you have effectively demolished the case for smaller carriers despite their advantages of being able to deploy to more areas simultaneously due to the possibility of building more of them (and even this, as you pointed out is not assured, since the US Congress approves the number of ships). Clearly, the US Navy has studied the issue and decided that smaller carriers are not worth it. Has the US Navy, however, tried the opposite approach and studied even larger carriers than the Nimitz?
 
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macawman    RE:Most Efficient Carrier Size   3/4/2004 2:45:58 AM
It appears that the optimum size carrier for the US Navy is a more efficiently designed Nimitz class. I think that the next carrier AIRPLANE will shape the next generation of US flat tops. January 21, 2004: The tenth and last of the Nimitz class carriers (CVN 77) will incorporate a lot of long awaited design changes. Although it will look like the other Nimitz carriers, the deck will be longer and wider. This will make it possible to store aircraft on deck without them hanging over the side. This, it was discovered can sometimes confuse the CIWS (Close in Weapons System, a computer controlled 20mm automatic cannon used as a last ditch defense against incoming anti-ship missiles.) The CVN 77 will have two elevators instead of three. The two elevators have been moved so that they can do the work of three. There are also more fueling stations on deck, so that the fueling crew won't have to drag fuel hoses across the deck so much. The ammunition elevators will also be moved to new locations, which will result in fewer ammo handlers being required, as they won't have to move bombs around as much as before. This "pit stop" approach to fueling and arming will require fewer people on deck, and make it safer for those who are there. The island has been shifted to the rear, and made taller and thinner. The main reason to keep the island at all is to have some place to mount the radars. But the new island will be have no admiral's bridge, just a small sitting room and visitor's bridge from which he can show guests what a carrier is like. The admirals quarters and staff spaces will now be below. The changes in fueling and arming, and one less elevator, plus greater use of automation on board, will reduce crew size by about 500 sailors. This makes it possible to provide roomier accommodations for the crew. The Navy believes this carrier will be the last with a steam catapult; the next generation is expected to have an electro-magnetic system of some sort. This alone will cut crew size several hundred more. The next class of carriers, the CV(X), will make massive use of automation and more intelligent layout. This is expected to cut crew size from about 5,000 to 3,000. This will allow for even better living conditions, and more space for bombs and aviation fuel. The CV(X) will probably also use a lot of UCAV (unmanned combat aircraft), which will contribute to making the crew size smaller because 25-35 percent of the aircraft won't have crews. The UCAVs are easier to maintain, because there is no gear on board to take care of pilots.
 
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Hugin    RE:Mark F   3/4/2004 7:01:09 AM
Quote: "What nonsense! Is this your opinion based on personal bias or do you have evidence to back up your claim that the Navy falsifies these studies?" Wait a minute Mark; I never claimed or even mentioned anything about anyone falsifying anything. That's just how you read it. Nor do I buy into any conspiracy theory. I was merely referring to a well known phenomenon within any organisation whether it's the Chinese government, GM's board of directors or the USN, namely than any review of possible future needs are 9 out of 10 times done in a way that will not seriously question present practises. This means that when the USN asks (itself) what type of carriers it needs for the future only certain questions will be asked, questions that will validate previous practises and dogmas far more than it will challenge them. I find it quite amusing that the many examples you mention in your post in reality proves my point. None of the examples mentioned goes outside the established practises, they all represent down-scaled (and compromised) versions of what the USN already knows (and cherish) so much and the thinking behind remains firmly within the "box". It's merely a question of how many aircraft, elevators, propellers, reactors, catapults and so on, while no one dares ask the questions challenging the established way things are done. A couple of years ago I read a proposal for a new type of carrier, written by a group of naval engineer students. I can't find the link anymore, but if I recall correctly, the objective was to provide 80% of a Nimitz class' sorties at half the price(cost of ownership). It was based on the idea that the USN would buy the STOVL version of F-35 and do completely away with catapults and arresting wires. The vessel would have had a large superstructure with partly automated rearmament/refuelling in a "pit-stop" scheme. I'm not qualified to say if such a proposal is practical and what downsides it may have, but it represents the kind of "thinking outside the box" necessary if you're really trying to change the cost-performance ratio for the better. BTW, if you scroll down to the "Bigger US Carriers" thread you will learn I'm a champion of BIGGER but CHEAPER carriers; not SMALLER carriers as you seem to believe if you rebuttal is any clue ;)
 
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Mark F    RE:Mark F   3/4/2004 7:43:30 AM
The final version of CVV (which I didn't describe for reasons of space) was supposed to take advantage of improved STOVL aircraft, which in the end, never materialized. Of course if you have to develop a new aircraft to take advantage of a new carrier, any cost savings are negated. The Nimitz design is pushing 40 years old and is essentially a development of a 60 year-old design. I have no doubt that ways can be found to make an all-new carrier cheaper to build. Reducing size is the obvious one that always gets turned to but the loss of capability is always more dramatic than the dollar savings. Some savings could be found in unit cost in an all-new design but the real savings would be in lifecycle costs. Greater automation for reduced manpower. More modern, more reliable systems. Longer intervals between refuelings - these are where the savings are going to come from.
 
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Mark F    RE:Roman   3/4/2004 7:44:43 AM
Nimitz is about as large as can be accomodated in existing yards.
 
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Hugin    RE:Mark F   3/4/2004 8:09:07 AM
Quote: "The final version of CVV (which I didn't describe for reasons of space) was supposed to take advantage of improved STOVL aircraft, which in the end, never materialized. Of course if you have to develop a new aircraft to take advantage of a new carrier, any cost savings are negated." Have you read about the efforts to build a supersonic Harrier and the possibility of addidng some type of "afterburner" to increase take-off weight. Well, IIRC, the prototypes were very promising, but the whole thing was abandoned for lack of potential buyers; talk about the "dog biting its tail". Fast forwarding to today: You don't need to develop a new aircraft, it's right there to order; just use the STOVL version of F-35. I've read the US Army is considering a number of the STOVL version too. Wouldn't it be wonderful? The USN, USMC and US Army ALL buy the same aircraft and will all be able to help the USN fill up the flat tops should a shortfall of airframes occur. As an added bonus, you'd save development cost for the CV and CTOL versions (though I guess it's becoming a bit late for that), just as training/maintenance issues and spare parts inventories offer prospects of further savings.
 
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Mark F    RE:Mark F   3/4/2004 8:13:53 AM
I think it is a bit late for any cost savings on a CTOL F-35. Besides, buy a more expensive, less capable version of the aircraft, just to save a few bucks on catapults? Seems like a bit of a false economy to me.
 
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