Air Weapons: 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). The RCFC screws into the front of the mortar shell, in place of the fuze. Dropped from the air, it will land within  5-10 meters of the GPS coordinates it was programmed for. An 81mm mortar shell weighs about eight pounds, with up to half that being explosives. It causes casualties within 20 meters of impact point. Thus GPS is accurate enough to make a micro-JDAM based on 81mm mortar shells effective. The mortar shell, with the RCFC, would weigh about fifteen pounds. A more powerful weapon would be a 120mm mortar shell. Normally, these weigh about 35 pounds, with up to fifteen pounds of explosives. An RCFC version of this would weigh about 45 pounds.

Such weapons would be expensive. While the mortar shells themselves cost $50-100 each, the RCFC for each would cost over $20,000. These would be competing with the many precision weapons the troops on the ground already have. For example, there is the 26 pound Javelin, with its nine pound warhead, and the larger (fifty pound) TOW with a 13 pound warhead. These two missiles are expensive, with TOW costing $25,000 each, and Javelin $75,000. But even that can be too much bang for the infantry. That's why the AT4 rocket launcher, and its four pound warhead is so popular. It's not laser guided, and you have to be pretty close to use it. But at the normal ranges its used (a hundred meters or so), it's very accurate, and it's cheap ($2,700). The LAW is similar, smaller (2.2 pound warhead) and cheaper ($2,000). What these smaller JDAMs are handy for are smaller UAVs out on patrol, and in need of a small weapon for targets of opportunity (like a few guys trying to set up a roadside bomb.)

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