BAE’s LROD Cage Armor
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Russian-designed RPG shoulder-fired rockets are a widespread threat in many parts of the world, including the current conflicts in Afghanistan and Iraq. At present, the most common threats involve RPG-7 single warhead variants, which are also produced in quantity by China (to Iran for use abroad) and by Iran (direct shipment to Iraq and Afghanistan).
There are 3 standard approaches for protecting vehicles against incoming RPGs: (1) Heavy or layered armor the warhead can’t penetrate; (2) Reactive armor tiles that explode outward when hit, deflecting, disabling, and/or disrupting the rocket and its blast; and (3) “Cage armor” or similar add-ons that can prevent detonation, or prevent the shaped charge jet from forming, at least some of the time.* The bad news is that providing enough steel cage armor can add a couple of tons to vehicle weight.
Enter BAE Systems’ LROD, developed under a fast-response Defense Advanced Research Projects Agency (DARPA) program to provide RPG protection for Hummers and MRAP mine-resistant vehicles. The project led BAE to ask if steel was really necessary – and the answer was: no…
- Nearer My LROD to Thee
- Updates and Contracts [updated]
- Appendix A: How RPG-7s Work (*)
- Appendix B: Additional Readings and Sources [NEW]
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BAE Systems’ LROD aluminum cage armor alternative provides similar protection, at less than half the weight of traditional steel. The process isn’t quite as simple as making an aluminum cage and slapping it on a vehicle, of course. BAE invested considerable time and effort to develop a design that minimizes the odds of a shaped charge jet forming if an RPG hits its armor. US Army officials then conducted more than 50 live-fire tests, in order to verify that its performance met their standards.
Once that challenge was solved, the next step involved leveraging aluminum’s lower weight in another way. LROD attaches to small vehicles using bolt-on methods, instead of requiring welding, or even full-scale cutting and chassis modification as is the case with some cage armors.
Additional LROD engineering work is required for each different vehicle type, in order to ensure a setup that delivers enough protection, and has the attachments and brackets located in the right places to take the load smoothly. That requires more up front investment by customers, but it delivers 2 key advantages. One is that bolt-on systems made of numerous similar modules are easier and cheaper to remove and repair if and when the vehicle takes a hit. That life cycle cost advantage is paired with an operational advantage, thanks to other patent-pending aspects of LROD that work to make in-field change-outs easier.
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LROD has become standard equipment on the US Army’s MRAP Class III Buffalo explosive ordnance disposal vehicles; over 100 kits have been delivered, and more are on the way for the USMC’s Buffalos. Force Protection’s MRAP Class I and II Cougar MRAPs have received them, and so has the MRAP Class I RG-31.
BAE is working on LROD variants for the tracked BAE Hagglunds Bv206/ BvS10 family, BAE’s amphibious AAV7 Amtracs vehicles, BAE’s new RG-33s, and other MRAP-type vehicles as requested.
As Appendix B illustrates, however, LROD has emerging competitors – some of which use completely different approaches to low-tech RPG protection.
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Nov 16/09: BAE Systems announces a $42 million U.S. Army contract to produce L-ROD bar armor kits for the U.S. Army’s RG-31 and Cougar MRAP vehicles.
April 23/09: BAE Systems information and Electronic Systems Integration in Washington DC received a $ 16 million firm-fixed-price, unfinalized contract for LROD kits. The contract includes 2 “Bar Armor kit” prototypes: 1 each for the BAE/GD RG-31 and the Force Protection Cougar 4×4 CAT I Mine Resistant Ambush Protected Vehicles; and 325 production kits for the Cougar CAT II.
Work will be performed in Washington, DC with an estimated completion date of May 1/09. One bid was solicited and one bid received by the TACOM Contracting Center, Detroit Arsenal in Warren, MI activity (W56HZV-09-C-0311).
Feb 2/09: An email from BAE Systems says that they plan to make 1,000 L-ROD kits per year on a new automated production line, and that they are hiring people to work in the Austin, TX manufacturing facility this year.
May 6/08: BAE Systems announces that it has received a $23.7 million contract from the Army’s Tank-Automotive and Armaments Command Life Cycle Management Command to equip 371 RG-31 vehicles and 174 MRAP-II vehicles (545 total) with its lightweight L-ROD bar-armor kits. The kits are designed to provide partial protection against anti-tank rockets, and are used widely on the US Army’s MRAP Class III Buffalo ordnance disposal vehicles.
Oct 8/07: BAE Systems announces an order for 215 LROD armor kits, under a not-to-exceed $14.5 million contract from the Army’s Tank-automotive Armaments Command (TACOM). BAE Systems will equip RG-31 and Cougar Class II vehicles with the aluminum cage armor, which is widely used on Army Buffalo explosive ordnance disposal vehicles. See release: “BAE Systems to Provide Bar Armor Kits for 215 U.S. Army Route Clearance Vehicles.”
July 17/07: BAE announces an initial contract that will see 14 LROD kits installed on installed on U.S. Army RG-31 and RG-31A1 mine-protected vehicles from BAE OMC & General Dynamics. The first 2 kits have been installed, and the US Army will procure 12 additional LROD kits for 2007 delivery to operational units in response to an Army Operational Need Statement. The Army has also expressed interest in procuring additional kits for the entire RG31 and RG31A1 fleet, which consists of about 425 vehicles delivered or on order. See release: “BAE Systems Delivers First Lightweight RPG Protection Kits for RG-31.”
Appendix A: How RPG-7s Work (*)
Though they are unguided, can be a bit tricky to aim, and have short range, the RPG-7’s disadvantages are masked in the close-quarters reality of urban combat and other common modern battle zones.
We know that many of our readers are engineers – hence a thank-you to DID reader Andres Kranjc. He points us to several sources that explain the detonation failure concept in more detail, from US Army TRADOC (SEC UNCLAS pdf) documents covering the RPG-7 [PDF format], which notes that stationary “RPG screens” first saw use in Vietnam. If the nose fuze passes through the screen’s gaps, the impact bends the warhead in a manner that shorts the detonation signal.
Netherlands-based TNO Defense, Security and Safety research lab’s “Constrictor” flexible net aims to provide precisely this kind of protection, using a more lightweight alternative.
Those of you thinking that screens are not 100% certain to prevent warhead detonation, depending on the angle at which the piezo-electric crush fuze hits it, are correct. Andres also points us to Russian equipment manufacturers who tout cage protection against PG-9S grenades, which use much the same concept. Claimed protection is “0.5 probability [DID: 50%] in the areas covered by grill screens.” A protection level of 50% is still preferable to 0% protection, of course, and certain composite armors and other techniques can improve the odds further.
The bottom line? If there is a direct RPG hit and the shaped charge forms its molten jet, anyone in an RG-31 (or worse, a Hummer) is probably in for a very bad day. While the jet is far less stable in air than it is when going through a dense and homogeneous medium like steel, several feet of stand-off detonation distance would be needed to stop it from penetrating lightly armored vehicles. Absent a lot of armor, very clever composite sandwich designs, and/or a lucky deflection of the jet away from key vehicle parts, the vehicle’s occupants are in real trouble.
In general, one can expect cage armor or RPG screens to turn only some incoming rounds into duds, or otherwise prevent the explosive from forming a proper shaped-charge jet. If that works, even an RPG full of technically “detonated” explosives that splatter against the vehicle in glops and bang/burn, probably isn’t going to do much damage. Preventing a properly formed shaped charge jet involves a lot of specific science, math, and engineering; suffice to say that there are a number of approaches, and that this is a popular field for additional research.
The offense is also busy, of course. New RPG designs are introducing 2-stage tandem warheads, whose 1-2 punch makes many attempts at passive defense much more difficult. Meanwhile, cage armors will continue to be a popular defensive option against the most prevalent RPG threats.
Appendix B: Additional Readings
- DID – Out of Whole Cloth: Tarian Rocket Protection. A different approach.
- Textron (Oct 13/09) – Textron Defense Systems’ RPG Countermeasure System Completes Phase I Testing. Another different approach. TRAPS is based on…. airbags.
- DTI Ares (May 16/07) – RPG-7.net. Covers TNO’s “Constrictor” net.
- US Army TRADOC (1976) – Soviet RPG-7 Antitank Grenade Launcher (SEC UNCLAS) [pdf]
