Murdoc posting at Defense Tech

R2-D2 vs. Mortar Rounds

I’ve got a new post up at Defense Tech. This one is on the Army’s version of the Navy’s CIWS Phalanx anti-missile system, the C-RAM.

R2-D2 vs. Mortar Rounds

A common tactic of the insurgents in Iraq is to set up a mortar (often in a residential neighborhood), quickly pop off a few rounds at an unsuspecting US or Iraqi military base, and then get out of the area before any response can be made. Next to IEDs, mortar attacks are probably the most common threat faced by most American troops not actively involved in combat. Although most mortar rounds explode harmlessly, plenty of damage and many casualties have been caused by lucky shots.

phalanxciws.jpgSince the attackers are often making their getaway even as the first rounds start landing, it’s very difficult to send a team of soldiers to apprehend (or kill) them even if the source location can be determined. And since the insurgents prefer to fire from built-up areas thick with civilians, a simple artillery barrage isn’t an option. Mortars are small and fairly easy to use, which means that large numbers of operators are available and they can pretty much come and go as they please.

A number of things have been tried to counter-act the mortar threat. The AN/TPQ-37 Firefinder Weapon Locating System, originally designed to track incoming artillery rounds from long range, simply wasn’t up to the job of picking up mortar rounds and calculating the firing location.

About the same time as that article appeared, another appeared on about a new system, the Lightweight Counter Mortar Radar, that was being tried out in Iraq with some success. The LCMR is used to track incoming rounds and feed target data to counter-fire units.

Getting back at those firing on you is all well and good, of course. But it doesn’t stop the incoming rounds from harming you or your installation. And, as noted, the insurgents prefer to fire from the relative safety of civilian neighborhoods. They’ve learned that American counter-fire is quick and deadly, and the mortar teams that have survived have adapted their tactics to negate American firepower. So the military is working hard to find a way to shoot down incoming rounds.

Since laser defenses are still quite a way off, the Army has looked to an existing system to fill the need. The Navy’s Phalanx CIWS system, an autonomous 20mm gatling gun capable of firing up to 4,500 rounds per minute, has been modified to defend ground units.

Known as “R2-D2” to Navy personnel, the Army is hoping to use these droids to defend bases. The program is called C-RAM, short for “counter rocket artillery mortar” system, and two test units arrived in Iraq last month.

R2-D2 is merely part of an integrated system. The previously-mentioned LCMR and the AN/TPQ-36 Target Acquisition Radar, the AN/TPQ-37’s shorter-range brother, feed information on incoming rounds into R2-D2 and it opens up in an attempt to shoot them down. At the same time, a Hunter UAV is dispatched to the calculated firing position in an attempt to attack the attackers with laser-guided Viper Strike missiles or at least track them so they can be intercepted by ground forces.

The naval Phalanx systems fire depleted uranium or (more recently) tungsten armor-piercing rounds. On the high seas, all these heavy rounds falling to the surface aren’t much of a problem. But in crowded urban environments this would present a very serious danger to friendly forces and civilians. So instead of using the AP ammunition, the C-RAM uses the HEIT-SD (High-Explosive Incendiary Tracer, Self-Destruct) ammunition originally developed for the M163 Vulcan air-defense system. These rounds explode in mid-air, raining shrapnel at the incoming rounds in order to destroy or deflect them*.

[UPDATE: This post was edited by Murdoc on 07/24/2005]

* UPDATE 2: The CIWS rounds don’t actually “explode in mid-air, raining shrapnel at the incoming rounds in order to destroy or deflect them” as I wrote. The self-destruction is a safety feature that keeps live rounds that miss (and there are a lot of them) from accidentally hitting targets on the ground or from posing a hazard later.


  1. This was a good idea that was long in comming. That said, if the army is serious about this, the Phalanx anti-missile system may not be the best choice. The Phalanx is big and heavy (around 6 tons), bulky (the R2D2 dome )and not the most adaptable. The selection of 20mm rounds, limits its usablity in alternate roles. The Navy is moving away from the Phalanx, to a more flexible and capable weapon, the Millenium Gun. The Millenium gun is built to be adaptable, and accept multiple sources of data. It is self contained, lighter (around 3.5 tons) and its 35mm gun, has a greater range then the Phalanx. Depending on the target, it can engage targets at up to 4 km.

  2. Small point: HEIT-SD does not really ‘explode in mid-air, raining shrapnel at the incoming rounds in order to destroy or deflect them.’ HEIT-SD rounds for the 20 mm Vulcan guns are point-contact fuzed. In other words, they only explode when they actually hit something or, at the end of their useful range, when their tracer burns out (the self-destruct point). There’s no time or proximity type fuze action involved. There are two fuze types typically used with 20 mm Vulcan ammunition: Super-quick and short delay. With a super-quick fuze, the round detonates on contact with the target body and the splinters mainly shred the outside airframe. With a short delay fuze, the round penetrates into the target body before detonating and thus the splinters chew up the internal works. To James: Thanks for linking to my website. Point of order: I’m afraid that you are comparing apples and oranges as the weight you give for the Millenium does not include the off-mount radar and computing system needed for fire control while the weigth for Phalanx does include those things. The 3.5 ton weight that you found at my website is only for the Millenium gun mounting itself, it does not include the needed radars and fire control elements. As Phalanx is a self-contained unit, including all radars, computers and gun equipment, the mounting weight of 6 tons is an ‘all-up’ figure. Only a power source needs to be added to turn the Phalanx into a truck-borne weapon system. For Millenium, you need the naval equivalent of ‘Skyshield’ sensor and command modules, which can be seen here: The guns in this picture are the land air-defense version of Millenium.

  3. I believe the AHEAD rounds of the Mil. gun have timed fuses. The timing on the fuse is actually set as the shell leaves the muzzle and the system knows exactly how fast the shell is travelling. The shells burst before they each the target and do create a cloud of shrapnel.

  4. Hi Gareth, My comment was really in regards to the type of ammunition used by Phalanx and other similar 20 mm ‘Vulcan’ cannons which was the subject of Mr. Murdoc’s article, I really wasn’t addressing the kind of ammunition used by Millenium/Skyshield. Please note that in Mr. Murdoc’s last paragraph, he is specifically describing how HEIT-SD operates. My post was intended to correct Mr. Murdoc’s description of how HEIT-SD operates. You are correct that AHEAD uses a time fuze, but, by definition, that means that AHEAD is not a HEIT-SD type of round which is what C-RAM uses. AHEAD is also not a HE round as it does not use a ‘High Effect’ or ‘High Explosive’ burster to attack the target, and it really uses pellets rather than splinters to shred the airframe (shrapnel is sort of an archaic term which is really referring to a specific kind of shell but which was also used around the mid-twentieth century to mean shell-casing fragment. These days ‘splinter’ is the generally more accepted term to mean a shell-casing fragment). AHEAD is actually in a new category and doesn’t fall within the older projectile abbreviated designations like AAC or HEIT. My Jane’s Ammunition Handbook, for example, doesn’t call it anything other than AHEAD (Advanced Hit Efficiency And Destruction).

  5. I was a CIWS tech in the Navy from 96-02, I was one of the first techs trained on the 1B version. I defintitly see a use for the 1B version in the Iraq. With the ability to track and lock on targets with the FLEER Camara, could be very useful. However, as a former tech and knowing what it can and can’t do, I can’t see CIWS being very successful at shooting down morter rounds.

  6. Rumor is that it has done it’s job (kill morter rounds) in Iraq. I could be wrong but if it has saved 1 life or 100 it has been a good choice. Better things are mostlikely on the way but for now it seems to get the job done.

  7. There is a comment (Posted by James | June 23, 2005 10:02 PM) saying the Navy is going to the Millenium Gun. Here it is 2 years later and to the best of my knowledge, the Navy has yet to schedule this gun for a ship. If anyone knows different, I’d love to hear about it.