Miragedriver
Brigadier
I looked at the image again and I think your right. There just are not enough barrels to get twelve. I almost want to say 10 barrels but that would not be enough. The engineer in me likes even numbers.
PLAN Aircraft Carrier programme...(Closed)
- Thread starter bd popeye
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I looked at the image again and I think your right. There just are not enough barrels to get twelve. I almost want to say 10 barrels but that would not be enough. The engineer in me likes even numbers.
No I did not forget to account for the major sink of energy i.e. leakage. that is included in step 2.
But does matter with the other system on the ship, where does the electricity for the EMAL come from? A boiler developing steam to drive a steam turbine which drives a fly wheel that drives a generator which drives the electromagnetic array.
A steam system would only require a boiler to develop steam, desalination is practically distilling, which is heating up water to the boiling point...
My point is to question what energy savings there are, lets have a quick run through some engineering rule of thumbs,
Ecat1,
Boiler, 80% efficient
Steam turbine, 90% efficient
Generator, 90% efficient
linear motor, 50% efficient??? (should be lower, since the linear motor gets the current from a flywheel generator, thus current is fluctuating; and since it is a fully inductive load, efficacy would be low)
mechanical losses - fly wheel yada yada - 95% efficient
Overall system: 30.8% efficient
Ecat2,
Gas turbine generator, 55% efficient (just checked commercial Mitsubishi one)
linear motor, 50% efficient???
mechanical losses - fly wheel yada yada - 95% efficient
Overall system: 26.1% efficient
Steam cat
Boiler, 80% efficient
Steam piston, 6% efficient
mechanical losses - fly wheel yada yada - 95% efficient
Overall system: 4.6% efficient
Where do you get 5-6% efficient?
USA catapult C13-2 used on CVN72 to CVN77 uses 500 KG of water at 450 psig, 459F
Embodied energy including desalination, is 2802 kJ/kg, where 981 kJ/kg is the enthalpy of liquid water at t or 1.4GJ of energy per launch; if all of the steam is lost and none is returned as hot water if all is returned as hot water it will be 0.91GJ.
With a 309 ft runway (94m), it can propel a 80,000lb (39,900kg) plane to 140 knots (72 m/s) (i.e. F111A) full afterburner thrust is 164.6 kN
kinetic energy of the aircraft post launch is 103.4 MJ
Work to accelerate a plane is F*S (assuming force applied is constant which it isn't but you have punch through of the engine and so on) force required to accelerate plane is 1100 kN.
You have some force used to overcome friction and aerodynamic loss and the engine values are bench values meaning they are lower in reality. But lets say 164.6 kN is developed, it means that the catapult supplied 85% of the launching force. lets assume that it account for 85% of the post launch energy, thus, 88MJ of energy, which is between 6% to 10% of the energy required to build steam.
So the 5-6% is reasonable. So yeah, seems like it is likely that Emal would be more efficient overall,
//edit
But this is also still contingent on the fuel source, if it is nuclear powered, it doesn't matter - as the reactor is used to generate steam or the reaction absorbed by boron rods...
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by78
General
My goodness Jeff, you are thorough. The US naval intelligence should really hire you as a consultant on the latest Chinese naval developments. Jane's ought to let you freelance too
Have you considered pulling together all the info you've gathered and put them in a book form? Maybe Deino can help with the editing and finding a publisher. We all can chip in to proofread and fact-check in exchange for advanced copies.
That'd be a fun little collaborative Sinodefence project.
Miragedriver
Brigadier
My goodness Jeff, you are thorough. The US naval intelligence should really hire you as a consultant on the latest Chinese naval developments. Jane's ought to let you freelance too
Have you considered pulling together all the info you've gathered and put them in a book form? Maybe Deino can help with the editing and finding a publisher. We all can chip in to proofread and fact-check in exchange for advanced copies.
That'd be a fun little collaborative Sinodefence project.
Jeff, you could get an entire other book just from the thank you and credits section.
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Skywatcher
Captain
My goodness Jeff, you are thorough. The US naval intelligence should really hire you as a consultant on the latest Chinese naval developments. Jane's ought to let you freelance too
Have you considered pulling together all the info you've gathered and put them in a book form? Maybe Deino can help with the editing and finding a publisher. We all can chip in to proofread and fact-check in exchange for advanced copies.
That'd be a fun little collaborative Sinodefence project.
I second that proposal!
Engineer
Major
The only fallacy here is one called Appeal to Accomplishment, and I was not the one who made it. Serving on a carrier is simply not the same as designing a carrier.
Obviously, if China installs a piece of technology on her carrier, than that technology would be proven and reliable. This was never in dispute. However, that technology to be installed does not have to be a steam catapult.
The issue with such argument is that EMALS does not seem to be a long way off, judging from the amount of Chinese research materials on the subject. Moreover, CATOBAR capability is not just about launching aircraft, as large part of that capability has to do with the people involved in the maintenance and logistic systems. Starting with steam then introduce EMALS means two separate groups are needed for two separate pieces of technology. Then, when new people come in for training, they have to be divided into two groups. Sticking with one launch system means the subsequent groups can fully utilize the experience from their seniors. This comes back down to logistic issue that I have been mentioning, and the latter strategy actually contributes more to CATOBAR capability in the long run. Time will tell, but time also favors EMALS.
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Engineer
Major
Is my argument that carriers are more important and built in limited numbers? Yes, it is. The importance means it is difficult to try out different carrier designs as they did trying out destroyer designs. The limited number means it is better to keep the difference between hulls as small as possible. We are actually in agreement on the premises, but you somehow concluded it is better to rush for steam catapults than to wait.
Actually, I am mimicking what PLAN thinks. PLAN has waited this long to have everything ready which made the Liaoning so successful. There is little reason why they would now rush things with their future carriers.
Your examples with VLS and destroyers aren't really applicable when it comes to carriers. I have addressed this point already, which you failed to see. As an analogy, I can buy a bike, then buy another one when I realize the first one isn't so suitable, and so on. I can afford to buy at least a new one every year, but I can't do that if we are talking about cars. Swap bikes with destroyers and cars with carriers, then perhaps you would start to see my points.
I have said this already, but I shall repeat it here: what POP3 said does not answer any of our question. POP3 didn't say PLAN will go for steam catapult. Rather he is confident that PLAN would go for steam catapults, with the rationale that PLAN has been doing research with steam catapults much longer than with EMALS.
As a response to what some interpret to be an assertion about PLAN choice of steam catapults, I pointed out that there are more considerations than just the length of time spent on R&D of steam catapults. This somehow got people excited enough to debate with me for hours. It seems people are too focused on the technology aspect, forgetting about the parts involving human and infrastructures.
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Engineer
Major
From , the efficiency of steam catapult is only 4~6%:
The efficiency of energy storage mechanism with EMALS:
Efficiency of the launch motor:
89.3% × 70.0% = 62.51%. Obviously there are other efficiencies that are unaccounted for, but the final number would still be far higher than 4~6% of a steam catapult.
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We don't actually know how far along they are with their development of an EM catapult. We can make conjectures based on leaked materials, but from those we can only conclude with certainty that they're working on the technology and that it will probably happen. That's why leakers like pop3 are so valuable. They can provide us details and context to better gauge our own assessment of these programs.
I've gotten some info suggesting that the first carrier will be a fully domestically made Liaoning, with some internal changes but not a whole lot of external modifications.
Second ship will be a few years later, where it will be a heavily modified Liaoning, maybe re-designed deck, smaller island, etc.
Third ship will be a few years after that, and it will be something similar to the Kitty-Hawk.
Second ship will be a few years later, where it will be a heavily modified Liaoning, maybe re-designed deck, smaller island, etc.
Third ship will be a few years after that, and it will be something similar to the Kitty-Hawk.
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