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scuttlebut steve 2/21/2007 10:16:38 AM

The destructive power of 16" shells is so overrated. A 16" shell packed just about the same punch as a 2000lb dumb bomb. What BB Iowa can do can be out-done by a single B-52 if indiscriminating carpet bombing is the mission.

except for the fact that one of those ships has several hundred shells and if we can make 155 mm rounds with gps and all that wonderful stuff we could do the same for 16" shells. Expense is the main reason we dont use them, if they were cheap we would have them and we would use them. If the cost of the platform wasnt so high the USN would have developed rocket assist (75-100 mile range, probably not even that big of a tech challenge) gps guided shells and would have found good use for these ships, especially given the toughness of the platform that is firing them.

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doggtag 16" shells vs 155mm AGS vs railguns vs SSMs 2/21/2007 3:35:50 PM

Benefit of 16" rounds: intensely heavy chunks of metal (>2000pounds) that have exceptional penetration capability vs reinforced concrete targets (dig around for WW2 pics of coastal emplacements after battleship bombardment) and pretty much anything else.

A 16" PGM could have truly prodigious range, possibly beyond 250km if we adopt a subcaliber munition (but development costs and price per round could be phenomenal).

Benefit of 155mm AGS: will give DDX/DDG1000 Zummwalts, and only them, superior gun firepower to any other naval vessel armed with lesser cannon. LRLAP Long Range Land Attack Projectile is hoped to reach 180km or so. Final cost per production round remains to be seen: only hoped-for estimates are available, and taking every other gun-fired PGM program into account, are considerably optimistic.

Could offer services-wide benefits if Army & USMC can adopt LRLAP for land artillery 155mm systems (however, the much greater range potential over the Excalibur 155mm PGM may only be achievable from the higher launch pressures and velocities of the AGS gun barrel).

Benefit of railgun: extremely high velocity generates incredible on-target effect due to kinetics & shockwave.

Considerable range potential compared to any other gun system.

Doesn't suffer from powder erosion in the barrel, but magnetic effects from the barrel's coils/rails on surrounding systems and personnel is still questionable without much more research. (Equals much more money needed to verify all saftey issues. We already know what to anticipate from chemical energy propellants)

Creating guided shells to withstand such massive launch stresses (as well as magnetic fields) may prove prohibitively expensive.

Benefit of SSM: for a given missile's size (diameter, length) it can be tailored for just about any range (make it longer), any warhead, and currently we can achieve CEPs easily within 5m. Shock stresses when launching a missile can be lower than any gun system (longer acceleration curve), so electronics and steering servos don't necessarily need to be as strong as they do in gun-fired (at high velocities) munitions.

Currently, the advantages favor SSMs, in whatever diameter best suits your payload-range-how fast ratios.

Take a look at the deck footprint of a triple 16" turret (how much area do we need to ensure safe traverse of the guns),

and the cubic space it takes up inside a hull to accomodate both the turret and all its servos, ammunition & propellant hoists, etc.

A VLS occupying the same surface area and volume of a 16" triple turret surely will offer us a wider type of ordnance available for any number of missions (not just shore bombardment), and we can even chose several different diameters of SSMs, all of which could go the same ranges with different warheads, or carry the same weight warheads different ranges at different speeds, etc.

Would a massive array of quadpack POLAR VLS cells give us more rounds available than a single 16" triple turret has in its magazine (consider how far down into a ship such a turret reaches: we have enough room to double, even triple stack (vertically) POLAR-sized missiles) ?

Most likely it would.

At 200km, a POLAR SSM gives us far greater range than any 16" rifle could reach.

But would a 16" LRLAP gun-fired PGM get us that far, for a lower per-round price?

How big would a 16" LRLAP be?

How heavy?

Current 5" PGMs are easily twice as long as typical shells (the shell/munition only, not including the charge lengths).

If we fit the 90kg unitary warhead of the GMLRS into POLAR, will it have more explosive power than a 16" shell?

(shells of that caliber were primarily metal, with a rather small percentage of their weight actually being explosive.)

As for the 155mm AGS: does its final overall cost justify all the more support we'll really get from it, seeing as only Zummwalts will be armed with it?

Is it in our best interests to spend so much for all of maybe 20 gun mounts (ten dstroyers w/ 2 turrets each, if that),

when we have 3 or 4 times as many 5" naval guns in service, guns which in all reality, will soldier on right alongside the AGS?

The Italians have developed guided shells also (Volcano for 127mm, the Davide system DART for 76mm), yet we never hear they're having as many gun-fired PGM problems as we in the US do (the fact they have actually done it in 76mm, and we haven't yet, should prove something- and we even use the gun that fires it!).

As for railgun

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Herald1234 Comment on railguns 2/21/2007 5:09:56 PM

BAE Producing Scaled-Down Rail Gun Naval Weapon?

Posted 07-Mar-2006 07:52

DD (X) Destroyer

BAE Armament Systems Division in Minneapolis, MN has received a pair of contracts for the "design and production of the 32 MJ Laboratory Launcher for the U.S. Navy." The design and fabrication of the 32 MJ Lab Launcher that can launch a projectile at Mach 8 will be a major step toward development of a full scale tactical 64 MJ EM Gun weapon system for the U.S. Navy. The two contracts together are worth almost $15 million.

Some hint of what they are talking about can be gleaned from the name... and now BAE has added more details.

The first stage contract was announced by DefenseLINK on March 3, 2006. It is a $5.5 million cost-plus-fixed-fee contract for the design and production of the 32 MJ Laboratory Launcher for the U.S. Navy. Work will be performed in Minneapolis, MN (66%) and Dayton, OH (37%), and is expected to be complete by August 2007. The contract was competitively procured and advertised via Federal Business Opportunities site, with three offers received. The Naval Surface Weapons Center, Dahlgren Division in Dahlgren, VA issued the contract (N00178-06-C-1008).

On July 6, 2006, BAE reported the next phase as well: a $9.3 million contract from the Office of Naval Research (ONR) to develop technologies and preliminary design for an Electro-Magnetic (EM) railgun prototype. Thy added:

"An electro-magnetic railgun uses electrical energy to accelerate projectiles to extreme velocities. Railguns do not require powders or explosives to fire the round and therefore free magazine space for other mission areas. In addition, electro-magnetic guns provide a highly consistent and uniform explosive charge that gives much greater accuracy.

BAE Systems was selected by ONR to advance to the next phase of the Innovative Naval Prototype Program. Under this 30-month phase, BAE Systems will take the state-of-the-art Electro-Magnetic Railgun technologies through technology maturation and develop a preliminary design of a 32-MJ EM Railgun. Thirty-two megajule is equivalent to a firing speed of Mach 8 or eight times the speed of sound. This will be an intermediate step on the road to a 64-MJ Tactical System capable of deployment on-board naval surface combatant ships.

....BAE Systems

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flamingknives 2/21/2007 6:22:39 PM

Why not have a VLS that can fit MLRS rocket pod containers. You can then get GMLRS and ATACMS in a standardised container, and any naval VL AA missiles then become available for land use (assuming associated radar systems).

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B.Smitty 2/21/2007 11:05:24 PM

MLRS pods do not have a square cross section, so you'd waste space with missiles that took up an entire pod. Also, length might be an issue. An MLRS pod might be ok for ESSM, but not for SM-2 - too long.

And, IIRC, M270 MLRS launchers have a relatively slow traverse and elevation, so might not be appropriate for a SAM.

But it is an interesting idea.

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doggtag Comment on railgun (Herald1234) 2/22/2007 12:08:54 PM

I'm not doubting the engineers' math on that one,

but my question still remains: without guidance and control mechanisms that can withstand not just the extreme G's at launching but also the intense magnetic fields the gun creates, what good does a 500km range projectile ("slug" in the above article, almost implying an unguided chunk) do if we can't guarantee it will even land within the same grid km of the target we wanted to hit?

I think that's always been the overlooked feature: no matter the velocity, a physical projectile will suffer from atmospheric conditions acting on its flight trajectory. Especially in a ballistic flight (arcing trajectory), at those ranges the projectile will suffer, even if minimally, minute distortions in its trajectory, both going up and coming back down. Meteorological effects will have greater influence on projectiles covering those distances more than they do for today's Mach 2-3 (2200-3300fps) artillery systems, even with their Mach 8 speeds.

Since we are moving more towards precision surgical strikes rather than large scale area effects, I won't be impressed with railguns until they can hit, shot after shot, within 10m of their intended target from those 250-500km ranges.

The machining and fine tuning needed to keep a projectile balanced and intact at those velocities will certainly add to the price. Not to mention the external coating materials needed to prevent the shell from melting at those velocities (the Sprint ABM of the late 1960-early 1970s used some kind of phenolic coating to allow for its short-lived, 6-miles-per-second time of flight).

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KlubMarcus 2/22/2007 12:39:28 PM

We build off of our experience with ICBM's. We've got plenty of experience making sure that electronics can survive naval conditions, including sub-launched ICBM's. We've got plenty of experience with getting fast-moving and relatively small ICBM warheads to their targets. Who knows? They're probably going to stick mechanical guidance and fuses to the railgun slugs. It only has to be accurate enough to hit the right city block or building, not a specific window or floor of the building. If the rounds really are small, then you just saturate the area if you can't get enough accuracy.

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Herald1234 2/22/2007 1:00:09 PM

I'm not doubting the engineers' math on that one,

[Your slug in the test rig is just that, a "block" of aluminum. The same solution we use for smoothbore cannon projectiles we will have to use for railgun bullets. At some moment after it clears the rails or more likely if it is exoatmospheric; upon entry the fins will snap out and the terminal guidance package takes over.]

[Treat it like the reentry killbody of a ballistic missile. The terminal descent phase for a TBM or an artillery round has no fundamental difference. The mass is still a ballistic mass subject to the same exact kind of solutions.]

[That repeatability would still be valuable if you could drop 50% of your bullets within 100 meters of your intended aimpoint. Killbodies even with the fin steerage and guidance package are cheaper than the equivalent rockets to make store and use. This is a steered mass with maybe an explosive filler.]

Another thing I failed to take into account: the aerodynamics, heat issues, and body balancing of shells moving Mach 8 aren't the same as slower projectiles: casings will have to be machined much smoother, as the smallest protruberance at those velocities could cause the shell to destabilize (imbalanced drag, additional friction, etc).

[Minor, you can machine balance a steel slug within 1/10,000 ratio balance tolerance with our current methods. A thick wall casing handles the heatloading. If you are that worried, make the bullet body out of duraluminum or stainless steel. It's not like it has to survive more than eight minutes.]

[Sprint was a thin-cased rocket built for its extreme lightness as well as its high specific impulse rocket motor to attain that ridiculous acceleration. You can build your railgun bullets thicker. You have to for the raigun bullet has to not only survive artillery shell acceleration but it also has to act as the contact brush/bridge across the rails so that the travelling linear electromagnetic charge can cross the rails and do work on the bullet]

And will those railgun shells need special protective storage on the ships, to prevent any accidental scrapes or bumps on the rounds, which could cause even a small enough pinhole or dent in the heat-resistant coating that could allow catastrophic failure inflight?

[That actually will be a good question as the railgun bullet will use a plastic breakaway sabot to sit inside the rails, exposing only those parts{brushes} of the bullet it needs to make ground with the rails for the shove charge to do work. I'm actuially more concerned with the effects of salt water on the railgun itself. Saltwater and railgun don't play well together. Pitting in the rails+50 Mwatt traveling linear charge =catastrophic barrel burst.]

Herald

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scuttlebut steve another rail benefit 2/22/2007 10:40:36 PM

one other benefit of railguns: ke rounds fired magnetically means no gun magazine detonation if struck and more rounds stored in the same size magazine space.

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doggtag thanx Herald 2/23/2007 8:18:25 AM

Here's a question then:

could the sabot of the railgun projectile actually carry the armature (or brushes or whatever) so the shell itself needn't be subjected to the electrical pulse?

Effectively, we'd be discarding the useless bit(s) after firing, just like dropping off an extended range booster after it's done its job.

In such a case, couldn't then the shell be contained/electromagnetically sealed enough to, in principal, act like a large faraday cage so the internal electronics wouldn't even need excessive EM shielding?

Then when entering the downswing of its trajectory, the shell could release/eject a piece off the tail to allow the GPS receiver to work, and the steering mechanisms could be deployed once the velocity has dropped to a more friendly mile-per-second or so (they could be contained in the aft section near the GPS kit, JDAM style).

But, very high velocity kinetic rounds like the LOSAT and CKEM, and even Patriot PAC-3 hit-to-kill, use reaction control thrusters around the nose to course-correct at such high velocities (because mechanical fins may not react fast enough).

And in that case, can those chunks of solid propellant in the reaction control mechanisms withstand the high electromagnetic stresses without initiating?

The other issue I see, if we totally contain the shell inside a faraday-esque sabot, can the petals/sleeve discard accurately- and quickly-enough (at those velocities) so as not to interfere with the shell's flight?

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