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Artillery: 120mm, Mortar, GPS, Make It Happen
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March 24, 2010: After years of searching (and procrastinating), the U.S. Army is finally going to choose a GPS guided 120mm mortar shell from one of three suppliers (two American and one Israeli). All the systems are similar. For example, one of the American systems is the RCGM (Roll-Controlled Guided Mortar). This one works by using a special fuze that includes a GPS unit and little wings that move to put the 120mm mortar shell closer to the target. Thus all you need to convert existing 120mm mortar shells to RCGM is the RCGM fuzes (which handle the usual fuze functions, as in setting off the explosives in the shell, as well as the guidance functions.)

To use RCGM, you place each fuse into a device that transfers the target GPS coordinates, then screw the fuze into the shell, and fire the shell. It would also be possible to program each fuze once it is screwed into the shell, via a metal probe that would go into a hole in the fuze, transfer the data, and signal that that the transfer was accurately made.

In any event, guided 120mm shells just got a lot cheaper and easier to use. This is particularly crucial for 120mm mortars, which are used by units close to the front lines, where not a lot of ammo can be carried, and resupply is riskier since the enemy is so close. Thus a guided 120mm shell means fewer shells getting fired to get the job done. And RCGM is not the first attempt to produce a guided 120mm mortar round. There are several, so the army can afford to put the three best candidates through a round of competitive tests.

ItÂ’s about time, because the army has been working on a guided 120mm mortar shell for a long time. Three years ago, the U.S. sent laser guided 120mm mortar rounds to Iraq and Afghanistan for testing. The XM395 Precision Guided Mortar Munition had been in development for twelve years, and was almost cancelled at least once because of the delays. The 38 pound XM395 round has a range of 7.5 kilometers, and will land within a meter (three feet) of where the laser is pointed. Unguided mortar shells cannot put the first round that close, and requires firing several rounds, and adjusting aim, before you get one on the target. A guided mortar round is very useful in urban warfare, where a miss will often kill civilians. The 120mm mortar round has about 2.2 kg (five pounds) of explosives, compared to 6.6 kg (15) pounds in a 155mm shell. The smaller explosive charges limits collateral damage to civilians. The XM395 was tested in Iraq and Afghanistan last year, but since it required someone nearby to use a laser designator, it was considered to have limited usefulness. Thus the push to get a GPS guided shell into service. Normally, an unguided 120mm shell will land anywhere within a 136 meter circle (on the first shot). The laser guided round will land within a one meter circle, and the GPS guided one with a ten meter circle. The GPS round is deemed the most useful, especially since the troops are satisfied with that degree of accuracy in GPS guided 155mm artillery shells, 227mm rockets and JDAM bombs.

Every U.S. infantry battalion is equipped with 120mm mortars. The army expects to select a GPS shell system by the end of the year, and quickly get it into service.

 

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LB    No they do not   3/24/2010 5:44:21 AM
"Every U.S. infantry battalion" is not equipped with 120mm mortars.  Airborne, Air Assault, Light infantry, and Marine battalions all use 81mm at battalion level.
 
The 120mm guided mortar shell will be very useful; however, getting an 81mm version to work will be far more useful.  A mechanized infantry battalion already has various guided weapons and the means to transport them.  The force multiplier of light infantry with guided 81mm rounds is much greater than heavy maneuver battalions gaining guided 120mm.
 
That said light infantry operating with additional attached transport as either light motorized or mixed light motorized/leg might desire replacing some number of 81mm with towed 120mm and/or have 120mm mortars attached or operating in support as some 105mm howitzer units will probably be asked to cross train on the 120mm mortar beyond the current levels.
 
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DavidE    Why are shells better than rockets   3/24/2010 6:19:50 PM
Since I know nothing about this, can someone please explain to me why it makes sense to fire
GPS guided artillery from a gun, where you face all the difficulty of getting the electronics to
survive the firing?  Doesn't a rocket, with a much gentler acceleration, make it much easier
to accomplish the same job?  And surely rockets come in similar sizes and ranges to artillery
shells, right?  So why aren't GPS rockets replacing GPS shells everywhere?
 
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Hamilcar       3/24/2010 6:53:45 PM

Since I know nothing about this, can someone please explain to me why it makes sense to fire

GPS guided artillery from a gun, where you face all the difficulty of getting the electronics to

survive the firing?  Doesn't a rocket, with a much gentler acceleration, make it much easier

to accomplish the same job?  And surely rockets come in similar sizes and ranges to artillery

shells, right?  So why aren't GPS rockets replacing GPS shells everywhere?

Now that we have miniaturized electronics that can survive 20,000+ gee jolts and mechanical guidance servos that do the same, we can make the guidance kits for gun launched  projectiles. Those shells are much smaller for equivalent payload, much cheaper and more plentiful than rockets. A 120 mm mortar shell is a lot more cost efficient than a Hydra rocket and the helo that comes with it.  
 
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DavidE    What about bazookas/rpgs   3/24/2010 10:32:11 PM
Thanks for this info. It sounds like you are saying that rockets have to be larger
and heavier than gun artillery.  But RPGs and bazookas were just as man-portable
as any mortar, right?  We couldn't base our GPS rocket artillery system on
this type of thing? 
 
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Hamilcar    You really need an artillery expert.   3/24/2010 11:01:43 PM

Thanks for this info. It sounds like you are saying that rockets have to be larger

and heavier than gun artillery.  But RPGs and bazookas were just as man-portable

as any mortar, right?  We couldn't base our GPS rocket artillery system on

this type of thing? 


But from my perspective (rockets are more my thing) those are direct fire short ranged weapons of less than 1000-5000 meters range and are intended for direct sight and shoot to no more than the horizon. What we discuss here is a crew served portable weapon (mortar) that can be towed behind a light truck and shoot rounds over mountains to hidden from direct observation targets up to 7000 to 10000 meters away. A mortar shell is a plunging  fire weapon that falls on you from a steep parabola arc. Its called indirect or plotted fire when you engage the target. This makes the mountain useless as a defense, and most likely a ditch if you can drop the mortar bomb into it. Precision guidance makes that possible. It will also crash through roofs as it falls meaning that those thick walled Afghan houses would offer no defense to a mortar shell like they would an RPG or some light antitank missile weapon.
 
Just from my perspective, that is why it seems to me that a PGM mortar round is cost effective for what it does.
 
H.
 
   
 
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LB       3/25/2010 1:53:57 AM
On one level it doesn't matter where the supporting fire comes from as long as you have it and it's effective.  On another level the more responsive weapons are organic to the unit and every leg infantry battalion already has 81mm mortars.  Light infantry battalions have very few other heavy weapons.  It might make very good sense in some situations to replace a Javelin with an RPG or SMAW type weapon but do you really want to do that in order to use a guided rocket when the Javelin is already a guided weapon and the 81 mm round has more utility?
 
The main consideration in a leg infantry unit is weight.  Everyone already is carrying far too much weight in equipment, gear, ammo, etc.  Guided 81 mm mortar rounds for mortars the unit already has doesn't add weight and in fact might result in fewer rounds needing to be employed and thus resupplied.
 
Moreover, there are already various guided direct fire weapons and also very accurate "unguided"- a tank main gun round may not be guided but it can be extremely accurate.  There are various small guided ATGW's available as well that employ various warheads.  A guided mortar round for an infantry battalion is a big deal that some will regard as revolutionary.
 
 
 
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Mil-Tech Bard    The meaning of 120mm GPS fuses   3/25/2010 11:35:25 AM
The military procurement cross over point for "all smart" is when the cost of GPS guidance of a shell or bomb is about a 10-15 times the cost multiple of a proximity or multi-function time fuse (about $300-$1000 depending on the capability and the total numerical purchase).

Once you start producing a lot of GPS "fuse replacements" at $10k-$15K per, the logistical pay off of being 100% smart pays for itself in terms of diminished logistical supply chain costs.  You need fewer smart shells to do the work, so the need to transport 100 dumb shells drops to 10-15 smart shells.
 
We have reached that crossover point with 155mm precision guidance kits and have passed it with 100% purchase of guided rockets for the MLRS/HIMARS launchers.

The trend lines in military procurement have been pointing this way for some time.
 
There was a huge problem getting time and proximity fuses for artillery in the mid 1990's because the end of the Cold War in 1989 killed military fuse purchases for a few years.  During that dead time, the industrial base sources for military time and proximity fuse components went off-shore.
 
When the Army went to buy a new generation of fuses in light of what it learned from Gulf War 1, they found this out the hard way.  New mechanical time fuses were not possible and affordable hardened electronics for the role were not there yet.  This significantly upped the price of the new generation of multifunction artillery fuses due to the development involved and the smaller than Cold War numbers purchased.
 
If you have to go that route anyway, the delta difference between an advanced multi-function fuse and a low end GPS precision guidance kit is not that much and precision guidance covers many rules of engagement sins in terms of protecting careers higher in the command chain. 

For example, a guided 120mm mortar shell that lands in the wrong place is 10 to 40 times less destructive than a 2000lb JDAM depending on how it is fuzed, and since it is organic to Tank, Stryker and Bradley infantry battalions, it does not have to go up to Brigade & higher command levels where the JAG officers live to get approval for use.  A 120mm mortar impact zone is also much less telegenic than a 2000lb bomb.
 
Some on the Strategypage boards would still like to use slide rules and quadrants for ballistic calculations to fire dumb shells, but the industrial base, and the culture recruits are drawn from, supports both mil-speced I-phone type devices and precision guidance fuses with GPS.
 
 
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Mil-Tech Bard    The meaning of 120mm GPS fuses   3/25/2010 11:43:38 AM

"Every U.S. infantry battalion" is not equipped with 120mm mortars.  Airborne, Air Assault, Light infantry, and Marine battalions all use 81mm at battalion level.

 

The 120mm guided mortar shell will be very useful; however, getting an 81mm version to work will be far more useful.  A mechanized infantry battalion already has various guided weapons and the means to transport them.  The force multiplier of light infantry with guided 81mm rounds is much greater than heavy maneuver battalions gaining guided 120mm.

 

That said light infantry operating with additional attached transport as either light motorized or mixed light motorized/leg might desire replacing some number of 81mm with towed 120mm and/or have 120mm mortars attached or operating in support as some 105mm howitzer units will probably be asked to cross train on the 120mm mortar beyond the current levels.



See:
http://www.strategypage.com/htmw/htairw/articles/20090106.aspx

Micro-JDAM

January 6, 2009: U.S. firm General Dynamics has successfully tested its RCFC (Roll Controlled Fixed Canard) flight control and guidance system with 81mm mortars dropped from  aircraft. The RCFC is like the guidance kit attached to aircraft bombs to give them GPS accuracy, and turn them into JDAM (Joint Direct Attack Munition).

<snip>
 
IMO, this is a game changer.  Each US Army battalion level tactical operations center is now going to own it's own 24/7 precision guided weapon armed air force.

Welcome to the era of federalized airpower. 

Airpower that is incapable by design of being used and directed by a centralized theater air commander.

Airpower that is organic to ground units and provides close air support and reconnaissance with in it's capability to the local ground commander without clearance through six to seven layers and two services worth of military command and control to get the job done.

The 1970's era saying "If you can see it, you can hit it.  If you can hit it, you can kill it" just got a close range, over the hill,  around the corner, in the next alley third dimension.

Strategypage.com talks about this capability going up to 120mm mortar shells and parking on Shadow class UAVs. 

The key thing I am looking for next is this Micro-JDAM kit being miniaturized down to "Nano-JDAM" sized kits for 60mm mortar shells for use on company level, Raven class, hand thrown UAVs.

Every company commander as his own air chief of staff, with his own PGM armed air force, will happen inside of five years, maybe in as little as two.

The USAF brass is going to have a heart attack when their Army liaison officers report on this happening in the field.

This is a phase shift in airpower that takes advantage of the Nintendo and X-box generations without the need for college educated pilots.
 
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Mil-Tech Bard    The meaning of 120mm GPS fuses   3/25/2010 12:12:35 PM
LB,

Orders of magnitude mean things. 

The deployment of this "GPS fuse"  -- think of them as JDAM kits for artillery and mortar shells -- is the firepower equivalent of going from 1870's machine gun unit deployment deployment to late WWI levels of machine gun deployment.  That is, going from machine gun as a "regimental gun" to platoon heavy support weapon, virtually over night.

The US Military's ground forces have developed tactical operations centers at brigade, battalion and increasingly at company level that are multi-media and direct both UAV's and ground based video/laser tracking and targeting.  They are using 155mm Excalibur and 227mm GMLRS rockets to engage targets urban targets due to their speed of flight, smaller collateral damage and shorter engagement time due to shorter coordination time, compared to USAF close air support.  Most of the "Close air support" in 2006 in Iraq was in fact GMLRS fire missions.

The deployment of the GPS fuse to mortars means that those battalion and company TOCs can engage targets out of line of sight with precision guided munitions from organic means without the time taken to call higher level chain of command. This is *extremely* important because every level of authority required to make a decision doubles the amount of time it takes to make one.

The "Kill chain," to use the modern term of art, with GPS fused mortars is roughly double the ballistic flight time of a GPS mortar shell in combat. 

That speed, rate, and volume of indirect fire PGM engagement will elevate American ground forces fire power, compared to the current Russian or Chinese Army's, to roughly that of the Imperial British Army versus the Zulus or the Dervishes.

This development will not only humbug the whole modern close air support paradigm.  It may make humbug the "Missiles in a box" NLOS-LS from the FCS program as well.

I know GPS fuses on Naval 5-inch guns are going to make the USMC ANGLICO teams very happy.  Hell, a single USMC MEU could stop a Chinese invasion of Taiwan _by itself_ with organic artillery and mortars firing nothing but GPS fused cluster bomblet shells.

Consider this passage from wikipedia on the SADARM:
 

Combat history

The system was used for the first time during combat during the 2003 Invasion of Iraq,[1][2] with a total of 121 rounds reported fired by the 3rd Infantry Division with 48 vehicle kills attributed to 108 M895 (sic) SADARM projectiles.

Given that there are two SADARM canisters per M895 shell, we are looking at a 22% hit rate for the 216 canisters fired in combat.

Now assume GPS fuses for the SADARM carrier shells and a JSTARS/UAV combination to play forward observer increasing that to a 44% hit rate.  We have dropped the total number of M895 shells required from 108 to 54.

Now assume that JSTARS/UAV combo is backed up by FCS unattended ground sensors, thus increasing the SADARM hit percentage to 88%.  

We now only need 27 M895 shells with 54 SADARM canisters to kill those 48 Iraqi vehicles. 
  
That is the power of GPS fuses with SADARM. 
  
Now consider that if we know which Iraqi vehicles are wheeled and which are tracked, we can substitute air burst HE shells for some of the SADARM to kill soft vehicles.

This isn't _A_ magic bullet.  
  
It is hundreds if not thousands of magic bullets fielded in a C3I/ISR system that can target all of them rapidly across the battlefield.

Heavy forces will need to field anti-shell and missile point defenses a'la HAMMERS SLAMMERS to remain relevant on the battlefield.

We are lucky that Iraq's Green Zone shelling got us to deploy Phalanx in the anti-shell "C-RAM" (Counter artillery rocket and mortar) technology.  It will give us the technological basis to deploy counter PGM artillery systems sooner than our adversaries.

 
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WarNerd       3/25/2010 2:46:15 PM

Since I know nothing about this, can someone please explain to me why it makes sense to fire GPS guided artillery from a gun, where you face all the difficulty of getting the electronics to survive the firing?  Doesn't a rocket, with a much gentler acceleration, make it much easier to accomplish the same job?  And surely rockets come in similar sizes and ranges to artillery shells, right?  So why aren't GPS rockets replacing GPS shells everywhere?

The choice between rockets and tube artillery for indirect fire, assuming similar warheads and range, in many cases comes down to the number of rounds that you feel you need to carry to do the job.  Both systems can be considered to have 2 parts, the round and the launcher.
 
Rocket propulsion is less efficient than the combustion of an enclosed charge like in tube artillery, and has a parasitic weight penalty because it has to drag motor casing along with it, at least during the boost phase, so per round the rocket ammunition is heavier than ammunition for tube artillery. 
 
The other half of the equation is the launcher.  The launcher needs to have a certain minimum length to allow the projectile to gain sufficient velocity for the main guidance method, usually fin or spin stabilization, to take over.  For a rocket the launcher can be as simple as a guide rod or a V-trough for a guided round as long as the crew and adjoining equipment and ammunition (more rockets) are protected from the, which is why tube launchers are more popular for small rockets (they also improve propulsion efficiency by restricting the expansion of the exhaust).  For tube artillery you need an enclosed tube strong enough to contain the pressure of the propelling charge and long enough to produce the required final velocity (ignoring hybrids such as RAM and shells) plus a method to deal with the resulting recoil forces.  The size of the gun (or tube artillery launcher) and the emplacement time (to anchor it up for firing) increase as a product of projectile weight and range.
 
So, in the final analysis, the analysis of rocket vs. tube artillery comes down to which weighs less for a number of rounds fired (N) of weight (Wr for rockets, Wp for tube projectiles) from a launcher weighing (Wl for rockets, Wc for tube).
 
         Wl + N * Wr  >?<  Wc + N * Wp
 
If you only need 1 to 4 shots rockets usually win, more than 10 shots the tube artillery usually wins.  Rockets also win at the extremes of range and payload, where the tube artillery launchers just get too big to be practical.
 
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