Return of the battleship.

[alexsa]

Originally Posted by Wooki

Hydrogen (IMHO) really only makes sense when it is transported via ship. It makes a lot of sense in projects where energy is available in a remote location, putting it in a bottle and then taking bottle of energy to where its needed.

These seems to be a suggestion the Hydrogen will not explode and is less dangerous than hydrocarbons. This is nonsense. Hydrogen by it nature has a very wide explosive range (4% to 75%) and is lighter than air and has a flash point of -259 degree C and a boiling point 252 degrees C. A number of merchant ships have had hatch covers blown off and been lost (with loss of life) when hydrogen generated as a result of oxidisaton of the cargo (we are not talking large volume here) found a source of ignition (this can be as simple as steel on steel contact with hatch covers). Hydrogen escaping into any space poses a serious risk. Teh attached report is a sobering reminder of the risk.

http://www.register-iri.com/content/...argoAsia-B.cfm

Diesel on the other hand as a flash point of greater than 60 degrees C (closed cup) and is not even considered a class 3 dangerous good (it comes in at about 62 degrees C). HFO is even less combustable.

As an aside there are currently no ships designed to carry H2 in bulk and it must be shipped as a refrigerated liquid (See UN1966) when shipped in tank/packaged form. There are compressed gas carriers being considered but these are being designed around natural gas.

Originally Posted by Wooki

and re the thread topic, yes that means creating a war fighting ship of large proportions, but I have argued that the CVN Nimitz and the CVN 21 are too small anyway. They are just big enough to have big ship maintenance costs but too small to get big ship benefits in capability. Make them 200,000 tons or 300,000 tons and they become way more efficient and you start getting into the fabled "sea base" concept.

Oh and armor? Just make it spaced armor or whack in a hydrogen tank and you are good to go.


cheers


w

200000 to 300000 tonnes will be an interesting design challenge. Assuming a low block coefficient necessary for high speed it will be a very long ship and there will be significant hull strength issues, particualry in a seaway. By way of an example look at the Emma Maersk. This ships DWT is only 157000 tonnes and the ships is 400m long. Noting cargo ships tend to be heavier than warships and the CVN21 is 100000 tonnes dispalcement on 333m the extrapletion to 200000 to 300000 tonnes is daunting.

http://www.shipgaz.com/magazine/issu...06_article.php

[kato]

Originally Posted by Wooki

Make them 200,000 tons or 300,000 tons and they become way more efficient and you start getting into the fabled "sea base" concept.

I don't really see any use for a ship of such dimensions - even as a carrier.

Despite the large size, you'd run into arrangement problems in carrier operations, unless you keep the embarked aircraft at present numbers - but that would be uneconomical to the max. Think about it - where do you place extra catapults? Elevators? Multiple angled flight decks - because other than that there's pretty much no solution for such problems? Also think for example about the scale of propulsion equipment to bring this carrier to proper aircraft operations speed. Or think of the crew scale.

A battleship of such dimensions runs into similar problems. The size of capital ships has traditionally been driven by two factors weighing in heavily - armament and armor. What kind of modern armament would you envision - a battery of 1000+ VLS cells? Because other than that, there's pretty much zero reason nowadays to go to large scales in ship dimensions. Once you start figuring in the protection package for such a ship though - radar/AAW pickets, ASW ships trailing the seas around it and such - this becomes a moot question; building a handful SSGNs is simply cheaper.

As a seabase - i.e. an integrated package for support of littoral, amphibious and land operations essentially? What for? Sure, i could see MPF ships of such sizes acting in such roles. But, again, there's an economic turnpoint reached - bigger ships always means less ships, and the MPF/Seabase ships are essentially tailored to support a specific externally given force size. Anything beyond that would be excess, and would reduce the possible number of concurrent deployments as well.

[Abraham Gubler]

Originally Posted by kato

Despite the large size, you'd run into arrangement problems in carrier operations, unless you keep the embarked aircraft at present numbers - but that would be uneconomical to the max. Think about it - where do you place extra catapults? Elevators? Multiple angled flight decks - because other than that there's pretty much no solution for such problems? Also think for example about the scale of propulsion equipment to bring this carrier to proper aircraft operations speed. Or think of the crew scale.

The size provides you with a bigger flight deck. The only reason carriers have catapults, wind over deck and angled flight decks is because of size limitations even on a 100,000 tonne carrier. The bigger a ship is the more efficient propulsion power can be and crew size.

The 300,000 tonne carrier could have a flight deck 500m long and 150m wide. This is 1.5 times longer and twice as wide as the Nimitz flight deck. Such a carrier could have two parallel runways and a large central deck park and deck edge elevators.

There have been quite a few serious engineering studies of such large carriers. The biggest problems with them are the same problems that face supertankers, that is the deep draft and problems with docking and navigating shallow waters.

[kato]

A 150m wide carrier would have to spend its lifetime in deep seas. And not fit into any canals of course. A 3.5-to-1 length to beam ratio with overhangs? Horrible on the likely block factor (or very susceptible to tipping over), and probably damn near immobile.

Oh, and a F-18 has a minimum safe runway length of around 1800 ft for conventional takeoff on land (official requirement: 2300 ft at min takeoff weight). 1400 ft would be "doable", but not safely so without wind over deck. F-35C has similar requirements. Unless we go with the requisite 800m minimum standards that land airfields for conventional-aircraft STOL operations have, we'll need catapults. And at least turning into the wind. And arresting gear. Read: a carrier - not a floating airfield.

[Abraham Gubler]

Originally Posted by kato

A 150m wide carrier would have to spend its lifetime in deep seas. And not fit into any canals of course.

Sure but if anyone was to build such a large carrier they wouldn't be doing so in order to have something nimble for sailing around Danish islands but for sitting 200km offshore with an airwing of 200 aircraft and enough ordnance and fuel to fly them for weeks.

Originally Posted by kato

Oh, and a F-18 has a minimum safe runway length of around 1800 ft for conventional takeoff on land (official requirement: 2300 ft at min takeoff weight). 1400 ft would be "doable", but not safely so without wind over deck. F-35C has similar requirements. Unless we go with the requisite 800m minimum standards that land airfields for conventional-aircraft STOL operations have, we'll need catapults. And at least turning into the wind. And arresting gear. Read: a carrier - not a floating airfield.

I never suggested the megacarrier could do away with catapults but tried to place some context into your problems with a big ship. With a 500m long deck why not have 250m long catapults? Who needs an extra 30 knots of wind over deck when the catapult can do it?

I find it really strange that someone can think that size is a hindrance to flight deck operations. Lack of size has always been why flight deck operations have been difficult. The USN went to a supercarrier size (USS Forrestal) in order to have a carrier able to operate for more than 66% of the time in rough waters like Arctic waters.

[kato]

Originally Posted by Abraham Gubler

I never suggested the megacarrier could do away with catapults but tried to place some context into your problems with a big ship. With a 500m long deck why not have 250m long catapults? Who needs an extra 30 knots of wind over deck when the catapult can do it?

But - the operative question - is there space for a higher number of catapults?

Realistically, carrier operations isn't about whether you have to turn the ship into the wind, but how quick you can get how many aircraft off the deck and into the air afterwards. Larger catapults do not increase sortie rate. Longer runways do not increase sortie rate (unless you can actually use them to take off CTOL at sub-minute launch rates).

Of course there is still some growth margin to achieve perfect operations with the current 4-catapult supercarrier. But beyond that growth margin (pushing a supercarrier by say about 10-20% in all three dimensions) there's simply no reason to grow further.

While you could transport a larger air group, it's not worth it operationally unless you can get a certain number of aircraft into the air within a certain time frame. 200 aircraft on a carrier - well, that's one wing for defensive CAP, three wings on operational rotation for strikes and other offensive operations between maintenance cycles. Questions that immediately pop up are: How long do you need to get 50 aircraft into the air for your strike/escort package (with four EMALS cats, proper wind condition and perfect taxiing it's between 10 and 30 minutes btw)? Do you need 50 aircraft with at a 250% surge rate simultaneously for the assigned tasks (which percentage of strike operations need it and for which percentage in duration of these operations)? Would it be more flexible and cost-effective to have two carriers with 100 aircraft?

[Abraham Gubler]

Originally Posted by kato

But - the operative question - is there space for a higher number of catapults?

Yeah sure. You could easily fit eight catapults alongside each other for a 150m wide flight deck. I don't know how you can think that a huge megacarrier would somehow be a laid out in the same pattern as a current supercarrier or somehow limited in flight deck.

Nice to see you've now gone from 'could never be done' to 'why would you' which of course is a good question and why no one has bothered to grow the size of a super carrier (there is no reason). But if for some operational reason you needed all your air wing eggs in one basket then it would be feasible.

[gf0012-aust]

Originally Posted by kato

But - the operative question - is there space for a higher number of catapults?

If you look at the new EM cats which are now on final land based evals - I'd say yes at the physical imposition level. They are taking up less space - and that also means that there then becomes a positive for extra available space on issues of bunkerage.

As indicated though - the issue is the volley rate - EM cats will enable faster cycliing, and hence faster launch rates.

Faster smaller cats (real estate) mean nominally:

• bunkerage opportunity
• corresponding impact on weapons lifts
• corresponding impact on fuel storage
• corresponding impact on stowage and maint of aircraft below deck
• an impact on overall lift issues - it does mean that larger lifts can also be used. That would mean a change in basic aircraft foldaway engineering, but it could also mean lifting multiple UCAV/UAVs at a time
• corresponding impact on taxi queues
• corresponding impact on recovery rates as aircraft can be parked off deck without effecting launch and recovery rates

Personally, I'm not a fan of sea-basing sized platforms, but thats neither here nor there anyway.

[kato]

And they "only" needed to switch to a completely new reactor/turbine design to power that, as they can't use the steam directly any more and instead now need to draw 11 MW extra in electric power just for EMALS... (the steam turbines on the two reactors of a Nimitz produce 64 MW total).

[gf0012-aust]

Originally Posted by kato

And they "only" needed to switch to a completely new reactor/turbine design to power that, as they can't use the steam directly any more and instead now need to draw 11 MW extra in electric power just for EMALS... (the steam turbines on the two reactors of a Nimitz produce 64 MW total).

The new super conducting engines (and they're already commercial) have 1/3rd the equivalent weight, almost 1/3rd less volumetric mass and close to double the output.

These engines are seriously in consideration for future submarines due to some inherent advantages.

again, one of the huge plusses for the SC engines is a bunkerage release. More real estate means more warfighting space and greater ability to stay and fight longer as more aviation fuel, more weapons and more sophisticated energy intensive ewarfare/sig management systems can be employed.

These are "here and now" engines, so not a buck rogers scenario.....

[StingrayOZ]

Why supersize a super carrier when they don't fill the current ones out with full cold war sized airwings. Didn't the US design the carriers with absolute war time maxiums of 70-80 aircraft?

I could see value in upsizing a carrier to 130-140,000t. For example extend STOVL (F-35B and UAV) and helicopter areas. But then again this would have to be balanced out and be at the cost of the US marine amphibious ships who already do this role. In the end its proberly better to have twice the ships, doing what they each do best. With two carriers you get better battle damage, more flexable maintence, more surge capability, the ability to site them in two different areas to maximise sorties and countless other benifits I haven't covered etc.

Given the US has 11 or 12 carriers at anyone time, and those carriers are expected to be global strategic assets, cutting the number and going for fewer larger ships seems like a risky move.

[gf0012-aust]

Originally Posted by StingrayOZ

Why supersize a super carrier when they don't fill the current ones out with full cold war sized airwings. Didn't the US design the carriers with absolute war time maxiums of 70-80 aircraft?

Using Forrestal as the first of the Supercarriers... she was able to combat embark over 100 aircraft.

The reduction in aircraft numbers over time has been more to do with relative mission efficiencies per weight of capability on target than on maximum aircraft per platform.

A wartime disposition could see all the carriers lift their combat elements as they certainly have the space to do it.

[peterAustralia]

Is it just me or does this thread seem to be a bit daft.

This hydrogen thing, I am sure you can power a surface ship with hydrogen, but please what are the benefits, and do they outweigh the downside (explosive, flammable and/or difficult to store, takes up a lot of space)

As to 200 thousand ton ships. Is this for real, will anyone actually ever build one, no. Can anyone afford to build one, no. Besides, if large multiple runways for a carrier are desired, the obvious route is to go down the mulithull path, such as a trimaran. There was a sketch done by someone at sinodefence forum some months back along these lines.

I might suggest, that better use of time would be spent on seeing what it any armour is appropiate in 21st century. Obviously there is no need now to protect against 15 inch shells. The threat now is missiles, bombs and torpedos. What type of armour is best to protect against blast, what thickness.

What will be the extra cost if say if a thousand tonnes or armour go into a 10 thousand tonne ship, given that theseadays the cost of ships is mostly in the fittings and electronics, the cost of the extra steel by itself is minor. What areas are best armored. Is there a need for a ship that is large and armoured, how much more would it cost versus a conventional ship with identical sensors and weaponry? What about a layer of water between steel plates, that was used in WW2 to protect British battleships against torpedoes.

No one has talked about torpedo protection. If I might suggest, a ship of three identical hulls, with multiple crossbeams. If one hull is badly damaged the remaining hulls would have enough strength and structural integrity to keep the ship whole and intact,,,,, just an idea. The outer hulls would be a good buffer against missiles, they could also be used to place redundant sensors, so that if a sensor on the center hull was knocked out, the backup can do its job.

[Wooki]

Originally Posted by alexsa

These seems to be a suggestion the Hydrogen will not explode and is less dangerous than hydrocarbons. This is nonsense.

Thanks for the input and my last on this. The cited examples are irrelevant to bulk hydrogen. The reality is that the velocity and atomic weight cause a fire (flame front) to behave in ways that are extra-ordinary. A breach in a liquid H2 container will create a combustible atmosphere well away from the vessel. You yourself may have observed this in high velocity vents Alexsa. But first (before a combustible atmosphere can form) any sort of fire will be snuffed by the initial shockwave formed by the hydrogen changing state. It literally takes microseconds for the fire to form and then be blown out.

This has been tested ad nauseum using an API round and liquid Hydrogen container and the results are always the same. the cylinder is punctured, a flame front begins to develop and is snuffed be the velocity of the shockwave. To the observor all you hear is a loud bang. Slow motion photography has to be used to ascertain the formation any sort of flame front.

Like I said, it is an urban myth that bulk H2 transport is dangerous. It is in fact safer then bulk hydrocarbon transport.

And also (as I wrote before) all bets are off in a submersible, where the H2 cannot vent safely. It is the velocity and atomic weight that make H2 safer.

cheers

w

[Salty Dog]

Originally Posted by kato

And they "only" needed to switch to a completely new reactor/turbine design to power that, as they can't use the steam directly any more and instead now need to draw 11 MW extra in electric power just for EMALS... (the steam turbines on the two reactors of a Nimitz produce 64 MW total).

I'm sure there will some happy folks on the new CVNs without the steam catapaults. They are temperature sensitive and had to be slowly heated up a day prior to getting underway. EMALs should make life easier.