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Subject: ROKN Patrol Corvette sucken by DPRK torpedo boat
YelliChink    3/26/2010 12:10:07 PM
Just happened 2150 Korean local time. Chinese reports say that it was DPRK torpedo boat. The ROKN corvette sunk is probably a 1200t PCC. I can't read Korean so I am not sure which one exactly. At this moment, 59 out of 104 crew have been saved so far. Best wishes to the still missing ones and condolence to families of lost sailors.
 
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gf0012-aust       4/7/2010 7:59:13 PM
V2, if they're planing, then they aren't semi-submerged. :)
 
I know I am being pedantic but......
 
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Reactive       4/7/2010 8:31:42 PM

V2, if they're planing, then they aren't semi-submerged. :)

 

I know I am being pedantic but......


Yup, I think that's the point, they may have made a run for it, one thought here, at the distances involved, what are the chances of any naval gun system engaging a fast maneuvering surface target at 40kts?
 
Pretty unlikely, someone care (thinking of someone who probably can't resist) to do the figures on projectile flight time, CEP of the airburst round (assuming it's an airburst). 
 
It's very unlikely to have been birds, strange that there was no air support available (heli's perhaps) to check it out, and if necessary, obliterate.
 
Wasn't birds, doubt anyone seriously thinks that..
 
R
 
 
 
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VelocityVector    gf   4/7/2010 8:54:50 PM

Bugger ;>)  Admit I am fascinated by one-offs and ambush tactics, especially when powers stick with and hatch nefarious schemes with these for decades.  They don't have to actually work, though as the Nazis showed some may work and at least the NorKs seem encouraged albeit desperate.  I am Macyver, I should seek psychiatric help.  Bear with me, or don't.  But the Taedongs, swell moniker, were designed to and apparently have achieved a degree of success at intrusions like the one I suspect for Cheonan.  The Iranians appear to have equipped their semi-submersibles with Furuno and they aren't going to use that radar to identify Burkes and with gps and area knowledge you don't need Furuno for shoreline navigation.  Tankers, though, at favorable transit points could be isolated with Furuno and set alight with very short range, rocket weapons.  Extended burn time could grant an attacker a quite vivid display.  Just saying.

v^2

 
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Hamilcar       4/7/2010 9:53:26 PM
Pretty unlikely, someone care (thinking of someone who probably can't resist) to do the figures on projectile flight time, CEP of the airburst round (assuming it's an airburst).
 
About 18-21 seconds depending on angle of fall and the proximate range ~ 8900-9100 meters.
 
H.
 
 
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gf0012-aust       4/7/2010 10:02:46 PM

Bear with me, or don't.  

am bearing...  and to add, it only needs to work once....
 
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gf0012-aust       4/7/2010 10:26:20 PM


Bear with me, or don't.  
am bearing...  and to add, it only needs to work once....
V2, not being cryptic, just typing on a netbook and hate using small keyboards, so being economical with word count
 
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Reactive       4/7/2010 10:43:10 PM

Pretty unlikely, someone care (thinking of someone who probably can't resist) to do the figures on projectile flight time, CEP of the airburst round (assuming it's an airburst).


 

About 18-21 seconds depending on angle of fall and the proximate range ~ 8900-9100 meters.


 

H.


 

Thanks,
 
So at 40kts the target's position is a semicircle of radius of roughly 420m (assuming 20s for projectile flight time). Very poor kill probability assuming that they're not setting a dead-straight course.
 
And if this is the primary mechanism that the Cheonan would use to engage targets these distances then the semi submersibles could be exploiting a gap in the effective enagement envelope of fast maneuvering targets with this class of patrol vessels..
 
I can't figure out the lack of air-support in the area after the sinking though, especially given the reports of a NK spyplane in the vicinity... No additional info of that as far as I'm aware... And none on the initial reports of 4 returns...
 
R
 
R
 
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YelliChink       4/8/2010 12:51:01 AM
So, none of you think that it's possible that some of the ship's subsystem were not working before they were sent to sea? From Korean sources, some newspaper reported that the ship went out to the sea after skipping a major overhaul.
 
Sounds like many subsystem on the ship, in addition to hull integrity, may not be that they supposed to be.
 
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Hamilcar       4/8/2010 1:04:56 AM
Thanks,
 
So at 40kts the target's position is a semicircle of radius of roughly 420m (assuming 20s for projectile flight time). Very poor kill probability assuming that they're not setting a dead-straight course.
 
That is the reason for plotting a track solution and for use of a rapid fire gun. Its an interesting problem as you have to solve for a vector (direction and speed) then beat the area of ocean that you predict the future contact position will be after time of flight. 20 seconds gives a semi-circle as you say of roughly 400 meters assuming a 20 m/s rate of advance. So you lay down a barrage wall of shells in front of the target. Effective air burst radius for 3 inch HE/frag would be about 15 meters radius (lethal). As a rough rule of thumb, I would beat at least 15 shells into the track once I got a shoot solution. That would be six seconds to lay down a ladder on a vector of 120 meters length, not 400 meters. The provisional object target I estimate at least to be to be 10-15 meters long which which means a five second turn moment at 15 degrees arc second. at 10 m/s before the hull loses bite and skids. A track solution should be possible and a PK of maybe 30%-50% is possible? Certainly that straddle salvo would be possible, and the crew of the speculated object target would sweat for it. Problem is that if it was sneaking out at 2 m/s, and it was 90 minutes after the attack? 4800 seconds would mean 9600 meters separation, but if we assumed the object hung around to make sure Cheonan sank and allowed only 3600 seconds at creep 2 m/s speed to evade? 7.2 kilometers separation and then its tracked, solved, shelled, uses countermeasures and speeds to safety? That would mean about 300 seconds dash to safety or 6000 meters at 20 m/s. The Soc Cho would have ~  60 seconds of R/U ammunition to use in ten such straddle solutions and could use both of her mounts to bracket the track to handle target turn right or turn left off solution.
.          . 
And if this is the primary mechanism that the Cheonan would use to engage targets these distances then the semi submersibles could be exploiting a gap in the effective engagement envelope of fast maneuvering targets with this class of patrol vessels..
 
That would be between direct lay and indirect lay, or about 4500 meters.  
 
I can't figure out the lack of air-support in the area after the sinking though, especially given the reports of a NK spyplane in the vicinity... No additional info of that as far as I'm aware... And none on the initial reports of 4 returns...
 
That I don't know.  
 
H.
 
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Hamilcar       4/8/2010 1:10:48 AM

So, none of you think that it's possible that some of the ship's subsystem were not working before they were sent to sea? From Korean sources, some newspaper reported that the ship went out to the sea after skipping a major overhaul.

 

Sounds like many subsystem on the ship, in addition to hull integrity, may not be that they supposed to be.

I looked  at that in the accident matrix, YC, but that is mostly rumor and scuttlebutt. Without a master's casualty list, we don't really know what worked on Cheonan, and what was flagged for refit and repair. 
 
She was old for a PC..

H.
 
 
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