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If only we had a carrier with ‘Cats and Traps’!

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If only we had a carrier with ‘Cats and Traps’!

Old 7th Jun 2018, 06:49
  #41 (permalink)  
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Just for information, found elsewhere (all of it, including that below the quoted contrac5 part).

Contracts NAVY
April 28, 2006

"Lockheed Martin Corp., Lockheed Martin Aeronautics Co., Ft. Worth, Texas, is being awarded a $52,400,000 ceiling-priced modification to a previously awarded cost-plus-award-fee contract (N00019-02-C-3002) to exercise an option to certify the small diameter bomb for the U. S. Air Force Joint Strike Fighter conventional take off and landing (CTOL) aircraft and eliminate the effort for wind corrected munitions dispenser and external fuel tanks...."
A short history of external tanks with the F-35 program re: what would be qualified as stores at the end of SDD.

The original assumption is that they would use legacy F-18 tanks like the conventional shape shown above. Once they got into simulation and later wind tunnel models doing stores separation they ran into problems. The conventional tank showed to be high risk for bumping into the aircraft and/or other stores.

So they came up with 3 elongated tear-drop designs. (see the graphic in the Sep 2006 brief). These carried a bit less fuel but were supposed to offer a solution. However in the same kinds of simulations there were still problems. There is a brief out there somewhere that shows quite the pitch-up of the tear-drop design coming way too close to the aircraft after being punched off. There were still risk issues of external store separation scenarios; for example when also carrying a 2000lb bomb on the nearby station. Of the three elongated tear-drop candidates the one that showed the most promise was one that had an extension on the pylon.

Eventually they decided that there was too much risk/time/money invested for now and pulled external tanks from SDD as per that April 2006 contract which also removed WCMD (for instance CBU-105). And of course that same contract added SDB for SDD......

Not long after; briefs started touting the idea that you don't need external tanks compared to legacy. I am sure that went to the plus side for MX calculations too as you don't need extra people/manhours to clean and maintain external tanks on a deployment if your jet can't carry them. Maybe we will see them someday after SDD. Who knows?.......
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Old 7th Jun 2018, 12:32
  #42 (permalink)  
 
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As explained at the time, tanks didn't do much for the A & C, which had 18-19 klb internal fuel already and a larger fuel fraction (internal fuel to clean TOW) than most fighters. The B, however, has a fuel fraction of about 0.3, which is similar to many modern aircraft (Gripen, Typhoon and Rafale for instance).

Engines is right to say that tanks are not to be dropped on a regular basis. However, the option is there, in extremis - for instance, a CAP may be flown with tanks and the tanks dropped if an actual adversary heaves into sight, or strikers may drop weapons and tanks if engaged unexpectedly. It's about the only way to achieve more than 500nm radius, even with a light load, on a supersonic high-g fighter, and the only way to go anywhere with a heavy load.

It's a bit more complicated on a stealth aircraft because tanks are not stealthy. Even if you can drop tanks and be fully stealthy afterwards (meaning that you lose the tank and the pylon, as in the F-22) you have to determine when to dump the tanks based on when you might be detected. That would often be very early in the mission. I don't think that the F-35 has the pylon-dropping option.

0.3 fuel fraction and no external option is not that much, so long over-water ferries are always going to be a bit of a production for the B.

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Old 7th Jun 2018, 15:06
  #43 (permalink)  
 
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Originally Posted by Pontius Navigator View Post
Some years ago the Captain of Ark Royal reckoned that the capacity of a modern CV was one aircraft per 1,000 tons. On that basis he said the QE could have 65 aircraft. Clearly we have compromised - big carrier, smaller air group.
There are caveats to that. If we really wanted to - and bought enough aircraft - you could fit 60-ish on the deck and hangar. But operating them would require extensive deck manoeuvres, which means lots more bodies, which means lots more accommodation. You could reduce the accommodation standard and cram more people aboard, but it's people that cost, hence the big ship to allow a relatively small number of people to operate up to 40 cabs.

The old Ark (IV) managed around 36 cabs on 56000 te - so quite a bit more than 1000te/cab - and required 2500 crew.

As for cats - the design still included provision for boiler rooms until at least 2007 (nigh-on cutting steel). EMALS provision was made in the power architecture, but somewhat hampered by both the IT*R status of the kit (and hence access to info) and level of maturity at that time. There's enough wiggly amps (nigh on 120MW) of installed generating capacity to cover off the propulsion load (80MW) and still leave a lot for electrical services....

Last edited by Not_a_boffin; 7th Jun 2018 at 16:47.
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Old 8th Jun 2018, 13:47
  #44 (permalink)  
 
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OK. I have only the vaguest notion of Cats and Traps but 2 Billion quid to retrofit as a system, really!!

Let us say I have the UK's checkbook, surely if we purchased the hydraulic bits needed for the Traps of the USA I would budget that at £10 million per carrier.
Now the steam generation system is way more complex, but Older UK non-nuclear carriers had steam catapults, let us say £150 million to fit this.

Could it be that simple, what have I missed?
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Old 8th Jun 2018, 17:43
  #45 (permalink)  
 
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Originally Posted by DroneDog View Post
OK. I have only the vaguest notion of Cats and Traps but 2 Billion quid to retrofit as a system, really!!

Let us say I have the UK's checkbook, surely if we purchased the hydraulic bits needed for the Traps of the USA I would budget that at £10 million per carrier.
Now the steam generation system is way more complex, but Older UK non-nuclear carriers had steam catapults, let us say £150 million to fit this.

Could it be that simple, what have I missed?
A few things you may have missed:
-The older UK carriers had steam boilers that were used for both ships propulsion and the catapults (and power generation). The new QE class has gas turbine propulsion, so no steam. A steam catapult would require an entire steam generation and piping system (which was mused, but not fitted). EMALS was also studied but would have been massively expensive (and risky)
-Add a few zeros to the price of the arresting gear.
-Catapults and arresting gear require much more manning and maintenance than a flat deck and ski jump. Factor in the additional costs for the additional crew, their housing ashore, pensions, medical, training.... Factor in routine maintenance (intensive), periodic refit, and major overhaul of the catapult and arresting systems throughout the life of the carriers.
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Old 8th Jun 2018, 17:58
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There is also the detail of where on the ship you're going to install all that plant - neither option is exactly compact. The size of the steam plant tends to get overlooked because current systems share steam plant with the propulsion system, but people seem to think the electrical system is small. It isn't, of course, because it needs something to store and deliver the energy. The most effective solution appears to be large flywheel-alternators which are spun up (slowly) with motors from the electrical system and then essentially shorted out by the cat which draws the energy out in a few seconds. These flywheel alternators are huge, highly stressed and have massive gyroscopic moments which need to be accommodated in the mounting structure. They're not the sort of thing which can be tucked behind the shower in the chief engineer's cabin.

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Old 8th Jun 2018, 18:12
  #47 (permalink)  

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I've heard stories of what's tucked behind the shower in the Chief Engineer's cabin. Now, where's Roger, the Cabin Boy?
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Old 8th Jun 2018, 18:38
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What chance of this going well when the British military can’t seem to operate a simple winch launched glider............ ship, catapult, advanced jet.......... I don’t see it ending well.
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Old 8th Jun 2018, 18:58
  #49 (permalink)  
 
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Originally Posted by Herod View Post
I've heard stories of what's tucked behind the shower in the Chief Engineer's cabin. Now, where's Roger, the Cabin Boy?
He's doing a personal development task with Seaman Staynes

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Old 12th Jun 2018, 14:44
  #50 (permalink)  
 
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The decision to go for STOVL was really fixed at decision point - the design was originally designed with either/or options, and that it could in future be amended for CATOBAR (Not least because Thales etc hoped to sell the design to the French). That was in 2002/3 but once the Uk decided to go STOVL the naval architects started designing the details to work that way, so parts that may have initially been intended to hold catapult or arrestor equipment became used for other things - the idea that there were these voids in the hull, just waiting for the change of mind in 2010, or a future refit, sadly didn't match the reality as the engineers and architects designed and built the ship in practice. So it would never be a 'quick change' - not least, think on all the 100s of schematics and plans that would have to be redrawn.
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Old 12th Jun 2018, 18:32
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Originally Posted by Davef68 View Post
The decision to go for STOVL was really fixed at decision point - the design was originally designed with either/or options, and that it could in future be amended for CATOBAR (Not least because Thales etc hoped to sell the design to the French). That was in 2002/3 but once the Uk decided to go STOVL the naval architects started designing the details to work that way, so parts that may have initially been intended to hold catapult or arrestor equipment became used for other things - the idea that there were these voids in the hull, just waiting for the change of mind in 2010, or a future refit, sadly didn't match the reality as the engineers and architects designed and built the ship in practice. So it would never be a 'quick change' - not least, think on all the 100s of schematics and plans that would have to be redrawn.
easy.."find".... "replace"........
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Old 12th Jun 2018, 19:00
  #52 (permalink)  
 
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cafesolo
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Cabin boy in Spanish "grumete"-- Larousse Concise. Wonder where that came from.
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Old 12th Jun 2018, 19:34
  #53 (permalink)  
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Grommet?

”A ring of rubber designed to line a hole to prevent a pipe passed through it from chafing.”........
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