Army/Marines closer to fielding GPS-guided arty

[akd]

Raytheon-BAE Systems Bofors' Excalibur Closer to Fielding

Tucson AZ: The Raytheon Missile Systems and BAE Systems Bofors' Excalibur team successfully concluded safety testing of the Excalibur global positioning system-guided 155 mm artillery projectile. Excalibur is the next-generation family of projectiles for US Army and Marine Corps artillery.

The Sequential Environmental Test-Safety (SET-S) series of 15 Excalibur projectiles took place Aug. 24 to 30. The program is a cooperative effort between the United States and Sweden.

The success of the SET-S series brings the team closer to the early fielding goal. The next steps prior to fielding to deployed forces early in 2007 are production verification tests, first-article tests and a limited user test.

The projectiles were fired from an M109A6 Paladin howitzer during the tests at Yuma Proving Ground, Ariz. The Excalibur rounds in the SET-S firing series were conditioned at extreme hot and cold temperatures, subjected to shock and vibration testing to simulate logistical and tactical transportation, initialized with the portable Excalibur fire control system, and fired at much higher than normal charge levels to demonstrate safety margin in the projectile design. Some of the rounds also were fired at 5 degrees off-axis to demonstrate the projectile's enhanced maneuverability and operational flexibility.

The goal of the SET-S series is to verify that Excalibur is safe to handle, transport, and fire as part of the Army's safety confirmation for fielding. Despite the over-margin test conditions, Excalibur continued to exceed its accuracy requirements. Average CEP (Circular Error Probability) was demonstrated at about 5 meters (16.5 feet), significantly better than the 10- meter (33 feet) requirement. One projectile detonated with devastating effects less than two feet from the target center.

The Excalibur program currently is responding to an urgent request from the warfighter to accelerate fielding because of the projectile's better than 10-meter accuracy that is not available from any other artillery projectile. Because of its accuracy and increased effectiveness, Excalibur reduces the logistical burden for deployed ground forces. It also provides lower collateral damage through its concentrated fragmentation pattern, increased precision and near-vertical descent.

Excalibur produces a wide range of effects in all terrain at extended ranges and in all weather conditions. With 155 mm howitzers part of the standard organization in current operations, Excalibur's precision effects are readily available to small-unit maneuver elements.

article

[John Kettler]

akd,

I've seen the segment on Future Weapons about the Excalibur several times, and it never gets easier.

The thing is downright scary. I think it'll have a major impact on MOUT by restoring a great deal of clout long denied to artillery by building masking.

Of course, the Guided MLRS is even worse!

Regards,

John Kettler

[flamingknives]

GMLRS - 200 lb unitary warhead - bigger boom, better range.

And currently in service.

[Thomm]

Originally posted by flamingknives:

... bigger boom ...

Ohhh, can it be that somebody here is forgetting about the evil collateral damage that these things do! Better stick with an deadly accurate 155mm shell for those surgical operations in urban areas!

Best regards,

Thomm

[flamingknives]

If you're going to knock down a house, 200 lbs isn't huge overkill, plus it's no less accurate than the 155mm shell.

Plus a bigger boom has more non-kinetic effect.

[John Kettler]

flamingknives,

When did the GMLRS attain IOC? Thought it was still in development.

Blast effects go up as the cube of explosive weight, if memory serves, but do we know: a) explosive charge composition for GMLRS warhead and 155mm HE; charge to weight ratio for each, and whether the 200 pounds for the GMLRS is the weight of the entire warhead or just the charge weight?

The blast radius and frag envelope for the standard 155mm HE round are very well established,

but I'd be wary about assuming anything about the GMLRS not backed up by video or stills, which I know from Future Weapons can be fired in airburst mode, surface burst and delay, the latter for killing field fortifications. Since the GMLRS warhead isn't subjected to the 100,000 Gs that the 155 round is, the warhead wall thickness may be less, which could mean that the fragments don't carry as far, even with a larger explosive charge.

The matter thus is far less straightforward than some might otherwise expect.

Regards,

John Kettler

[flamingknives]

February this year, IIRC. There were a number of articles on their use.

Defense Industry Daily is one that mentions their use. Check the links in the article for more information.

[John Kettler]

flaming knives,

What I read said that the 200 pound number is the all-up warhead weight, not the charge only. Here's

a link to a GMLRS combat use account. Attention getting!

http://www.defenseindustrydaily.com/2005/10/gmlrs-used-successfully-in-iraq-battles/index.php#more

Regards,

John Kettler

[RSColonel_131st]

How accurate can you fire an unguided 155mm?

5 meter CEP is great, but are normal shells that much more inacurate?

[flamingknives]

Unguided shells are significantly less accurate, and also have a shorter range. Excalibur, being guided, can scrounge a bit of aerodynamic lift and glide a bit more distance than a classical ballistic arc.

A presentation on the subject gives unguided 155 a CEP of 160m at 25 km, but that's with cargo rounds. Unitary ought to be more consistent.

[c3k]

flamingknives,

I have no source for this, but how does the lack of guidance have an effect on range?

Guidance needs control: most controls utilize aerodynmics; there is no "free lunch"; aerodynamic forces - be it lift or turns - comes with a drag penalty.

Or, do the guided rounds utilize some sort of booster?

Are there pop-out wings? How is the round de-spun, if so?

Thanks,

Ken

[flamingknives]

web page

That has a bit on it on page 7, but basically you can use the control surfaces (even thought they are small) to maintain the attitude of the projectile such that the lift-drag ratio is optimised. The round is de-spun by pop-out fins which are then needed to stabilise the projectile. These also generate lift, although their small size means that their drag is small.

[c3k]

flamingknives,

Thanks. I've done a bit more research (okay, okay - I typed "excalibur" into google) and found this:

http://www.globalsecurity.org/military/systems/munitions/m982-155.htm

In this write-up, the author discusses the xm982 round and hit upon "base bleed" and "rocket" technology built into the design. This, to me, makes it quite obvious that the range extension is due to rocket assist - exhausted through base bleed nozzles.

Edited to add the following:

"XM982 Excalibur - Similiar to the M483A1 with the addition of a rocket motor to further increase the effective range, and with options to increase delivery accuracy." (from: http://www.globalsecurity.org/military/systems/munitions/155.htm)

Thanks,

Ken

[ September 25, 2006, 04:12 AM: Message edited by: c3k ]

[John Kettler]

c3k,

Technically, base bleed technology is not the same as rocket assisted propulsion (RAP). Rather, base bleed is a range enhancement measure which works by reducing drag around the base of the shell through combusting material which generates enough atmospheric displacement to smooth the sharp, turbulent transitition when the air flow comes off the shell body and then decouples, producing wake burble. The base bleed effect is rather like making the shell pointed on both ends, thus aerodynamically much smoother. Base bleed is one of the key technologies to the new generation 155s pioneered by Gerald Bull, as in ERFBBB (Extended Range, Full Bore, Base Bleed), = long barrel, no saboted subcaliber projectile, and base bleed to get the most out of the redesigned, more aerodynamic shell. By contrast, RAP is a rocket booster "kick" motor on the end of an old school artillery shell. While it adds range, accuracy suffers.

Regards,

John Kettler

[c3k]

John Kettler,

AH! Thank you for the informative primer. Yeah, the bubble of low-pressure dragged behind any moving object creates a large amount of drag. Filling that void from an on-board pressurized source would reduce drag and lead to longer range.

Having educated me on that, this says: "XM982 Excalibur - Similiar to the M483A1 with the addition of a rocket motor to further increase the effective range, and with options to increase delivery accuracy." (from: http://www.globalsecurity.org/military/systems/munitions/155.htm)

That statement, as regards the xm982 Excalibur, is what made me think, as I still do, that the Excalibur is rocket boosted. I have not seen pictures of the base of the round. I -assume- that the rocket exhaust utilizes a base-bleed path, instead of a single central nozzle. And further, that it produces thrust as opposed to a decrease in drag.

Additionally, from what I can find, the base fins are mounted on a rotating band, such that the round will continue to rotate while the base fins will not. (Basically a slip ring.) Is this correct? Although, that puts the canards at distiinct disadvantage!

So, do the base fins, upon deployment, utilize a slip ring with high friction, so as to stop the round from spinning?

In short, I've seen lots of glossy cartoons and tables of how great the xm982 is/will be. How does it work - nitty gritty details and all that, and do any pictures exist showing some of the control details?

Regards,

Ken

Edited to add:

Alright, I did some more sleuthing, and found that, indeed, John Kettler, you are very much correct. There is a cutaway diagram showing a base-bleed system, self-contained, at the very base of the projectile. The diagram shows the entire ogive section filled with "Rocket Propellant Grains", adjacent to 5 "Nozzles" which ring the circumference where the curved ogive section meets the straight cylindrical section. That would be the rocket boost exhaust.

So, two separate range-enhancement systems: a nose mounted, mid-body exhausted rocket boost; and a drag reducing base-bleed system.

Now, on to that slip ring....

Thanks,

Ken

[ September 25, 2006, 06:43 AM: Message edited by: c3k ]

[imported_Wildman]

and here I heard that the GMLRS was not performing well in the desert. I may have to get back with my Army ammo buddies and see what's what.

[aka_tom_w]

OK!!

I want to be on the winning team that has this weapon!

Will it be in the game?

Check it out:

Posted 03-Oct-2005 06:30

Related stories: Americas - USA, Field Reports, Lockheed Martin, Middle East - Other, Missiles - Precision Attack, New Systems Tech, Warfare - Trends

Also on this day: 03-Oct-2005 »

M270 MLRS

Back on May 9, 2005, DID noted that several new forms of smart artillery shells would begin to give US artillery relevance again in urban battles fought under restrictive rules of engagement. On June 28, 2005, DID profiled the multi-national Guided MLRS system in more detail. Now that GPS/INS guided system has been used in combat by the 3rd Battalion, 13th Field Artillery Regiment in Iraq.

DID has details regarding these specific uses - along with overviews of the larger campaigns of which they are a part.

The U.S. Army news service reports that unitary-warhead GMLRS rockets were fired in Tal Afar west of Mosul, destroying two separate buildings from over 50 kilometers away with zero advance warning and less collateral damage than a precision bomb. The targets were two housing complexes that had been fortified and were known to house many insurgents, based on intelligence from units in the field that have been engaged from the structure or who had made contact with the terrorists around the structure. The rockets were fired on Sept. 9 and 10, killing 48 insurgents, said Maj. Jeremy McGuire, deputy of operations, Force Field Artillery, Multi-National Corps - Iraq.

Damage to surrounding buildings was described as "almost non-existent," while the target's destruction was described as "absolute."

[flamingknives]

c3k, could you share that picture of the Excalibur that shows the rocket in the Ogive?

This web page shows the manufacturer's spec, and there's no room in the ogive for rocket motors. It needs the base-bleed system, since the aerodynamic design of the rear end is rubbish, having no discernable boat-tail. Fired as a dumb round, I suspect that even with base-bleed, it would not go as far as some existing, unassisted rounds.

You can see from the spec sheet that it has a slip obturator - this is the only bit that engages the rifling, so it should minimise the spin of the round. I'm not sure why the fins rotate. It's worth noting that the British Army uses APFSDS rounds from a rifled gun, so slip obturators must be pretty effective.

This web page shows another diagram of the flight (page 7). Note how it says "ballistic prior to apogee" indicating that after apogee, it is not ballistic, but in controlled flight

web page

web page

web page

All indicate contolled flight to gain extra range.

[c3k]

flamingknives,

I found the cutaway diagram here:

http://www.globalsecurity.org/military/systems/munitions/m982-155-specs.htm

My question about the round centers about it's "lift". All the aerodynamic surfaces appear to my untrained eye to be control surfaces, not lifting surfaces. Hence, they modify it's impact point, not range. I freely admit I have an almost total lack of real knowledge about this round.

The slip obturating ring is still puzzling to me. The diagrams I've seen place the base fins ON the ring. I'd think a bit of rifling induced spin would be good for the first part of the round's flight. Any clarification on the obturating ring and base fins and how they relate to each other would be appreciated.

The links you provided are helpful. They all seem to show the fins deployed immediately after firing. Additionally - as a grasp - the PDF document has the cover illustration of the round showing the fins blurred. As if they are in motion, spinning.

I agree the canards pop out at apogee. I do not think they could extend the range by any significant amount. (I leave that vague so I have wriggle room later!)

Thanks,

Ken

[ September 28, 2006, 05:09 AM: Message edited by: c3k ]

[flamingknives]

I'd hazard that the cross-section is a concept design. Every picture I've seen has the guidance and control equipment in the ogive, which leaves scant room for rocket motors. You'll also note that the round shown has no base fins.

Lift isn't solely due to the canards, but the control that they exert allows other sources of lift to be exploited. The base fins and the body also provide a substantial amount of lift. The gliding flight is further evidenced by the trajectories in every source. All are ballistic to apogee followed by a non-ballistic - i.e. controlled - descent. Base bleed extends a conventional ballistic trajectory while rockets typically function in the early stages to allow the round to reach a higher apogee.

The rotating base fins are a confusion, but their presence indicates that spin is minimised right out of the barrel, or the drag they induce would be entirely parasitic.

[MikeyD]

This thread got me searching the web. mostly interested to compare U.S. and Russian finned warhead design, though I admit terminal guidance is totally different:

Russian Kitlov-2 guided artillery shell

Guided artillery PDF download

And here's a little news blurb:

US sanctions Russian firm for selling arms to Iran

( 2003-09-17 09:48) (Agencies)

The United States said on Tuesday it imposed sanctions on a Russian company for transferring laser-guided artillery shells to Iran and it imposed, and immediately waived, broader sanctions on Russia.

"The United States government has determined that the government of Russia transferred lethal military equipment to countries determined ... to be state sponsors of terrorism," the State Department said in the U.S. Federal Register. While the notice did not identify the equipment, a State Department official said it was laser-guided artillery shells. "

The site "Moscow Defense Brief "states that Tula Instrument Design Bureau was supplying the Krasnopol 155mm laser-guided artillery shell to iran, though the company denies the claim. India has also signed-up to purchase the munition.

[c3k]

flamingknives,

I agree that the link to the Excalibur cross-section could be an artist's concept: that it has little bearing on the real round. That's why I'm trying to find a real picture of one.

Spinning fins: again, agreed that spinning the whole round with fins would be highly parasitic. My question is whether the round is de-spun from the beginning; do the fins continue to spin; do the fins help to de-spin the round?

Thanks,

Ken

[flamingknives]

Unless the fins are on a frictionless bearing, they would help to de-spin the round. Since, as a scotsman once said, "ye canna change tha laws of physics" they would, therefore, de-spin the round. Mind you, the round wouldn't be spun up that fast anyway, as it features a slipping obturator. The picture below shows the round in stowed and deployed configurations. In the stowed configuration, the obturator is visible forward of where the base fins pop out from.

For images of the round, I doubt you can do better than Raytheon's website.

[c3k]

flamingknives,

Thanks, been browsing pictures and I cannot find ANY which show ports or nozzles anywhere on the body. So, the rocket assist may have been a dream idea, or an early development later dropped.

However, several pictures -undated- show 4 tail fins, pop-out style like the canards, on the tail instead of the 8 fin spinning ring. Is that a difference between a submunitions carrier and a unitary warhead round?

Hmmm, I'm thinking it would be better for me if someone could ship me examples of each, with an appropriate firing platform. I'd post the results of any firing trials I'd perform.

Thanks,

Ken

[flamingknives]

Actually, if you're that interested, you might try trundling over to the StrategyPage fora, where there's a poster under the handle "Artyengineer", who apparently works on the M777 howitzer and has worked with the M982.

From what I've seen, I think that the four-fin tail is an old design, and the eight-fin spinner is the current state of play, for some reason.