JDAM and JSOW versus PHALANX CIWS

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HJ RE:JDAM and JSOW versus PHALANX CIWS 4/11/2005 12:27:52 AM

Jim and I are now at peace thanks to off-line chat.

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displacedjim RE:JDAM and JSOW versus PHALANX CIWS 4/11/2005 10:07:10 AM

It was my bad. I misinterpreted/assumed facts not in evidence regarding HJ's comments based on what I would mean if I'd said them. Briefing Rule No. 1: Know your audience! I apologize. Regarding the subject(s), I can only offer opinion, as I don't know any specifics regarding CIWS effectiveness. I'd take a guess and bet the more common reason a gun like Phalanx or an AK-630 shoots down an anti-ship cruise missile is because it shoots it down, i.e., it renders the missile non-flightworthy, as opposed to getting a catastrophic warhead kill. Missiles typically have their sensor in the nose, followed by their guidance system, battery, warhead, fuel, motor, and finally the fin actuators in the tail. Just one or two puny 20mm coming through the sensor and guidance unit surely must knock it out. But then, I seem to recall footage of warhead kills of missiles, so that must happen, too. Given the difference in trajectories and the fact it is following a near-ballistic flight path, I'd think about the only way to stop a bomb is by catastrophic warhead kill. In general, I thought the explosive fill for those missiles and bombs was actually pretty insensitive to shock, such that even some hits from a 20mm or 30mm wouldn't set it off. After all, if the fusing fails the bomb's a dud, even if it smashes through a ship (Falkands, anybody?) In the case of the older DU ammo for the Phalanx, maybe the polyphoric effect if a penetrator goes through the warhead casing and into the explosive can detonate it? A standard Mk84 bomb body is pretty thin steel even at the nose, but the BLU-109 casing is I think on the order of a couple inches thick at the nose. I'd guess that's reaching (and past) the limit of penetration capability for a 20mm or even a 30mm firing uphill at it--at least until it gets (too?) close. Also, while it seems likely to be better than getting a hole put in you, a bomb detonating topside is no picnic, either, and can still knock a ship out of the fight. In the case of a laser guided bomb, a hit in the (admittedly small) nose section could disable the laser sensor and blind the bomb, even if you don't detonate it. From that point on, it would go ballistic--of course, being so close to the ship by then, that may not matter and the bomb will probably still be a hit or a near miss. JDAMs, on the other hand, have their guidance and actuator package in the tail section, so warhead kill is the only way to go. Displacedjim

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gf0012-aust RE:JDAM and JSOW versus PHALANX CIWS 4/11/2005 10:24:18 AM

"JDAMs, on the other hand, have their guidance and actuator package in the tail section, so warhead kill is the only way to go." Unless you shoot it (JSOW/JDAM) in the arse via a top down attack from something already loitering... but that is way beyond the realm of "likely and possible" in a stand alone ship defence scenario. gets back to the issue of ensuring organic air is near and present as much as possible. shooting a JDAM/JSOW up the freckle would need liberal doses of prayer/luck/timing/opportunity all rolled into one. ;)

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Aurvangur RE:JDAM and JSOW versus PHALANX CIWS 4/13/2005 6:46:49 PM

Anti-ship missles fly at Mach 0.8 Silkworm to Mach 2.2 for Sunburn. Bombs drops at 144 ft/s=Mach 0.13 (terminal velocity). Phalanx fires 20mm round with 15mm Tungsten or DU. 4500 rounds per minute. Phalanx range is estimated at 1 mile(this seems low). Super Rough Guestimates So it looks like we've got 36 seconds with the target in range which is 2700 rounds fired by the Phalanx assuming it is fired for the first intercept at the systems max range. An inch of steel protecting the bomb? With 15mm of DU it's not a problem. I can't imagine the bomb not going off but what do I know. Phalanx will have plenty of time to make multiple hits on the bomb. Bad news: At 1 mile or less at intercept, alot of that bomb shrapnel will still be hitting the ship. Might work but you better be ready for the rain of debris. The debris alone might cripple a Chinese landing craft. Bad time to be on deck.

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EW3 RE:JDAM and JSOW versus PHALANX CIWS 4/13/2005 7:13:19 PM

"Bombs drops at 144 ft/s=Mach 0.13 (terminal velocity)." where did you get that number? it's usually defined by v=at^2 where a=9.8m/s^2 t = time. so after 10 seconds v = 980m/sec. That's a first approximation good for short time intervals, beyond that you have to deal with Stokes Law, Reynolds numbers, and drag coefficients. I'd guess it's get up to around M.8 or so. Interestingly one of the SDBs (Diamondback?) has "wings" that it retracts or disposes of just to reduce drag and increase terminal velocity.

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Aurvangur RE:JDAM and JSOW versus PHALANX CIWS 4/15/2005 5:32:34 PM

My bad. A person's terminal velocity is 144 mph (80-200 depending on weight and position.) A 500lb JDAM is supposedly around 600mph, if you have a better number plug it in. 1mile/600mph = .01666h = .1 min = 6 seconds 4500 rounds/ minute * .1 min = 450 rounds. At an effective range of 1 mile, the Phalanx could put, at most, 450 rounds on the target. A glancing blow might not do it but I would bet that even 1 round solidly hitting a JDAM would set it off. 15mm DU bullet at 2300mph(-gravity&drag) meets bomb traveling at 600mph. My money is on the Phalanx but again, I wouldn't want to be on deck when the shrapnel hits.

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EW3 RE:JDAM and JSOW versus PHALANX CIWS 4/15/2005 5:39:41 PM

To be honest with you, if dropped from a B-2, I doubt they would even see the JDAM coming. And the SDB which is about 6 inches in diameter, will be out next year. One thing that worries me, is that someone on SP mentioned that CIWS stands for "Captain it won't shoot". From my experience in the Navy there's not a lot of talent with guns of any type, so I can believe his observation. (I've also seen it confirmed in a list of the systems most of of service.)

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blacksmith RE:JDAM and JSOW versus PHALANX CIWS 4/17/2005 7:39:19 PM

I recall a news bite around the time Phalanx came on line (1970's?) that it could intercept a 4 inch shell (~105mm). That's a lot smaller than a JDAM, JSOW, or SDB and probably a whole bunch faster. The next technology to add to the mix (haven't heard of it used in CIWS, but someone will eventually get around to it) is the electronically fused 20mm XM1018 High Explosive Air Bursting (HEAB) round developed for the OICW. A time delay fuze causes the projectile to explode in the proximity of the target. While a JDAM bomb casing may not care about shrapnel, fuzes can be extremely sensitive, and the JDAM tail kit is not in a bomb casing. The current technology is in favor of the defender although some is not fielded yet. Best offense is to saturate the defenses.

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EW3 RE:JDAM and JSOW versus PHALANX CIWS 4/17/2005 7:59:04 PM

I could be very wrong, but I thought I saw a blurb that they cancelled the HEAB in 20MM form. Also, and this goes back a way in time, but there is used to be a "hole" in the air search radar capability from directly overhead extending out like 15 or more degrees from the perpendicular. The gain of the old style radar antennas straight up was horrible. This could have been fixed with newer technology, and two ships would wind up scanning each others cone, so that can protect you. But if you're alone or not networked and that cone is still there, that's where the JDAM goes, and you won't see it coming because it's coming from a B-2.

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gf0012-aust JDAM and JSOW versus PHALANX CIWS 4/17/2005 8:23:56 PM

It would be interesting to see HEAB fired from the Metalstorm 36 barrel platform. Barrels could be mixed as well. HEAB, solids, short cannister, flechettes could be mixed and electronically fired across a range of engagement zones. Metalstorm would be better off working on their turreted multi-barrel rather than dicking around with UAV's and UGV's . The multi-barrel weapon is really way beyond the CTD stage. With a bit of corporate courage they could have fielded a trials platform years ago. bloody suits... ;)

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