CV-18 Fujian/003 CATOBAR carrier thread

[taxiya]

Unless, instead of all the catapults connecting to the cycloconverter like the US ones, now the cats are connected to the inverter. So when you shut one off, you shut them all off, and the same problem remains?

There is no cycloconverter (an AC-AC converter) in China's launcher. I don't know what inverter you mean. Regardless, in China's system each launch motor is controlled and fed by separate control cabinet which does the AC-DC-AC work. Turning off one motor only need to turn off the DC bridge from the AC bus in that single control cabinet. It should not affect anything else. That DC bridge is acting as a dedicated switch for one launching motor.

[Edit]
If by inverter you mean DC-AC converter that creates the driving pulse wave for the motor, then there is not one single "inverter" for all motors, but dedicated "inverter" for each motor. That is the beauty of going through DC, each one is isolated from others by basic design.

I think the diagrams that started this conversation is very misleading by omitting critical details that differentiate the two systems and hide the problem of EMALS. The black boxes in Chinese system contain the DC bridges which acts as switches.

 

[Helius]

There is no cycloconverter (an AC-AC converter) in China's launcher. I don't know what inverter you mean. Regardless, in China's system each launch motor is controlled and fed by separate control cabinet which does the AC-DC-AC work. Turning off one motor only need to turn off the DC bridge from the AC bus in that single control cabinet. It should not affect anything else. That DC bridge is acting as a dedicated switch for one launching motor.

[Edit]
If by inverter you mean DC-AC converter that create the driving pulse wave for the motor, then there is not one single "inverter" for all motors, but dedicated "inverter" for each motor. That is the beauty of going through DC, each one is isolated from others by basic design.

I mean catapults from the US EMALS are connected to the cycloconverter due to the AC-AC config, which is obviously is what it's for, and collectively from what I understand.

So yes, if the PLAN EMALS does employ AC to DC to AC, their cats would be connected to an inverter at the DC to AC end of this arrangement.

 

[stannislas]

There is no cycloconverter (an AC-AC converter) in China's launcher. I don't know what inverter you mean. Regardless, in China's system each launch motor is controlled and fed by separate control cabinet which does the AC-DC-AC work. Turning off one motor only need to turn off the DC bridge from the AC bus in that single control cabinet. It should not affect anything else. That DC bridge is acting as a dedicated switch for one launching motor.

[Edit]
If by inverter you mean DC-AC converter that create the driving pulse wave for the motor, then there is not one single "inverter" for all motors, but dedicated "inverter" for each motor.

Chinese catapult is highly likely using the super capcitor instead of flywheels, I can't imagine where you think fujian use the DC-AC?

 

[taxiya]

Chinese catapult is highly likely using the super capcitor instead of flywheels, I can't imagine where you think fujian use the DC-AC?

Where do you get that "highly likely"? It is therotically possible and desirable, but not according to Ma Weiming as of now.

Read papers by Ma Weiming and other people from his team, it is said to be flywheel. Ma Weiming clearly said that super capacitor at the moment of writing does not have the required energy density.

Also please understand that MVDC is NOT excluding local load being AC. MVDC ONLY means the main power bus is DC.

Also you need to know the basic of linear motor, it is an AC motor. The input is DC but the control circuit will generate AC of desired frequency to regulate the speed. That is where the DC-AC happens.

Here is the paper by Ma Weiming "电磁发射系统中电力电子技术的应用与发展", see highlight especially the orange coloured texts "AC-DC-AC".
energy from flywheel can not be fed directly to the launcher, it must be converted to desired ... through AC-DC-AC converter.



same paper, flywheel is at hundreds MW power class (required by catapult).

Another paper "电磁发射技术" about catapult (电磁弹射技术)
Chapter 4.1 says catapult is based on flywheel.



And lastly

 

[enroger]

Where do you get that "highly likely"? It is therotically possible and desirable, but not according to Ma Weiming as of now.

Read papers by Ma Weiming and other people from his team, it is said to be flywheel. Ma Weiming clearly said that super capacitor at the moment of writing does not have the required energy density.

Also please understand that MVDC is NOT excluding local load being AC. MVDC ONLY means the main power bus is DC.

Also you need to know the basic of linear motor, it is an AC motor. The input is DC but the control circuit will generate AC of desired frequency to regulate the speed. That is where the DC-AC happens.

Here is the paper by Ma Weiming "电磁发射系统中电力电子技术的应用与发展", see highlight especially the orange coloured texts "AC-DC-AC".
energy from flywheel can not be fed directly to the launcher, it must be converted to desired ... through AC-DC-AC converter.

View attachment 91240

same paper, flywheel is at hundreds MW power class (required by catapult).
View attachment 91236
Another paper "电磁发射技术" about catapult (电磁弹射技术)
Chapter 4.1 says catapult is based on flywheel.
View attachment 91239
View attachment 91237View attachment 91238

And lastly

Wow, I was completely wrong about cap vs flywheel.... turns out cap actually has higher energy density but much lower power density compared to flywheel? The more you learn.... I guess the real secret sauce is in the AC-DC-AC

 

[iantsai]

Islands comparision. by 梁无咎@weibo.com

 

[ougoah]

Ford appears to use a very outdated mast design in comparison to 003. Chinese radar and electronic sophistication is apparent in just an image. Any reason why Ford uses so many antenna units with dome covers? It's like comparing a Soviet cruiser with a Burke here.

 

[Tam]

Ford appears to use a very outdated mast design in comparison to 003. Chinese radar and electronic sophistication is apparent in just an image. Any reason why Ford uses so many antenna units with dome covers? It's like comparing a Soviet cruiser with a Burke here.

The domes are mostly satcoms.

Note that Early Enterprise used a very early AESA design, forgot the name of it. However, the concept was way too advanced for the technologies at that time so it was mainly experimental and abandoned.

Later Enterprise removed the early AESA and replaced it with the SPS-48, which is a frequency scanning planar radar. This radar electronically scans vertically and is rotated horizontally for 360 degree coverage and 3D acquisition. It works in the same principle as the Russian Fregat radars, except its much bigger and more powerful. This type of radar is simple and reliable, Soviets then Russians, and the PLA also has their land equivalents used as volume search radars. Nimitz continued to use the SPS-48, and there is no new radar change with US carriers until the Ford class. US did not choose to adopt air defense radar like AEGIS SPY-1 into aircraft carriers, and fixed 3D phase array didn't arrive until the Soviets with the Kiev and Kuznetsov classes with the Mars Passat. However Mars Passat radar proved to be troublesome, so they replaced it with a large frequency scanning planar radar, forgot the name of it, which also ended up inherited into the Indian Navy carrier.

Ford used both the SPY-3 and SPY-4 AESA radars but the lead ship will be the only one that will equip it. The next ship will equip the EASR, which is the baby version of the SPY-6 that is rotated around, along with the SPQ-9B, which is a small X-band planar radar that is also mechanically rotated. The second setup will be much cheaper, and both SPY-3 and SPY-4 seems to have a troubled development, and their use of Gallium Arsenide also makes them outdated compared to Gallium Nitride radars. So at this point, both SPY-3 and SPY-4 are dead ends.

I am not sure the amount of satcoms shown on the 003 island is all there is to it, as both the Liaoning and Shandong seems to have more. Its likely more will spout up as the ship is being fitted.

 

[henrik]

Ford appears to use a very outdated mast design in comparison to 003. Chinese radar and electronic sophistication is apparent in just an image. Any reason why Ford uses so many antenna units with dome covers? It's like comparing a Soviet cruiser with a Burke here.

It seems like the tower of type 003 is skinnier. What if they miss something and have to add more room for installing stuff?

 

[zavve]

The next ship will equip the EASR, which is the baby version of the SPY-6 that is rotated around, along with the SPQ-9B

CVN 79 will use S-Band AN/SPY-6(V)3 along with X-band SPY-3. There will not be an SPQ-9B nor any rotating AN/SPY-6(V)2. Please differentiate EASR (AN/SPY/6(V)2) from the fixed EASR (AN/SPY(V)3) that USS Kennedy will use.