JDAM stands for Joint Direct Attack Munition. These are designated GBU-29, GBU-30, GBU-31 and GBU-32 (GBU is U.S. Military speak for General-purpose Bomb Unit).

From the Federation of American Scientists at http://www.fas.org:

The Joint Direct Attack Munition (JDAM) GBU-xx is a tailkit under development to meet both USAF and Navy needs, with the Air Force as the lead service. The program will produce a weapon with high accuracy, all-weather, autonomous, conventional bombing capability. JDAM will upgrade the existing inventory of general purpose and penetrator unitary bombs, and a product improvement may add a terminal guidance seeker to improve accuracy. JDAM can be launched from approximately 15 miles from the target and each is independently targeted.

The FAS has good stuff on military systems; I recommend the site highly. The four variants of the JDAM listed above are for use with 250, 500, 1000 and 2000 lb. gravity bombs, respectively. They are tailkits, which means that they bolt onto an existing dumb bomb, and using their movable fins and navigation/guidance systems maneuver the bomb onto its target. They were conceived and built with the intention of counteracting the negative effects of weather, winds and smoke on conventional bombing accuracy.

The JDAM is told at the start of the mission what coordinates it is intended to hit. This makes it a Competent Munition. It is then launched (dropped) from an aircraft, either Naval or Air Force, up to 15 miles from the target. The JDAM uses internal INS or GPS systems to determine its present location, and maneuvers the bomb onto which it is bolted to strike the desired target coordinates.

One advantage of the JDAM is that it is quite cheap when compared to more complex guided, seeking smart weapons. It is also a large force multiplier for aircraft; whereas previously a bomber with 10 conventional munitions typically would expend all 10 in an effort to ensure the destruction of one target, a bomber with 10 JDAMs can allocate them to 5 or ten separate targets with a reasonable assurance of destroying perhaps five to seven of them, and in ideal cases all ten.

The Joint Direct Attack Munition (JDAM) is a guidance kit that converts unguided bombs into all-weather, multiple guidance capable "smart" munitions. There are several versions, but even in the least capable configuration they are an more than an order of magnitude more effective on a per-warhead basis than than unguided or passively guided bombs.

I love the JDAM.

The most common types are the 500 lb. (nominal weight) GBU-38, and the 1000 lb. GBU-32. They are based on the Mk-82 or -83 bombs, respectively, which are essentially nothing but a whole bunch of the nitroaromatic compound Tritonal packed into a streamlined steel casing. Officially, the Mk-82/83 are referred to as "Bomb, General Purpose, Low Drag". Unofficially, they are called "dumb" or "iron bombs".

When the fast movers call on station and give their loadout, and it includes one or more JDAMs, there is a special kind of comfort in knowing that they can drop thousands of pounds of hate onto a dart board from fifteen miles away and three miles up. I can say with surety of memory and total elucidation that the JDAM has saved my life more than any other piece of kit in the entire DoD inventory.

Don't get me wrong, anything in the air capable of putting metal onto (or into) badguys is great. Rockets, missiles, autocannon, chainguns, or if shit gets totally out of hand, the plain jane .50 in the doorway of the exfil chopper - all are welcome. We do not discriminate when it comes to air-to-ground superiority.

That being said, I LOVE the JDAM.

My wet dream is an A-10 with JDAMs under the wings. If for some terrifying reason three or four 500-pounders wasn't enough, there's nothing Warthog pilots like more than an excuse to fire up the Avenger - but I'm getting sidetracked here.

At a median cost of about US$50,000 each, depending on the exact model, your taxpayer dollars are capable of evaporating enemy personnel, vehicles, gun emplacements, or whatever else gets in the way in a surprisingly cost-effective fashion - two JDAMs (say one ground fuzed and a follow-up airburst) cost less than a quarter of the life insurance payout for a single lost American troop.

In a typical scenario, the gas being burned by the asset itself and tankers supporting it, all of the routine and repair maintenance involved for both airframes, and the personnel required to maintain them, cost more than the munitions by far.

The financial analysis is totally secondary to most of what I have to say, though.

I LOVE the JDAM.

Try to imagine how much I love the JDAM, and try to imagine how much the badguys hate the JDAM. Those two opposing feelings, and their polarity, are directly influenced by each other in an ever-escalating feedback loop from which there is no escape, except by cease of conflict.

In Afghanistan the only thing in all the world scarier to the insurgency than helicopters (oh, how they hate helicopters of all stripes) is what they call "bombard". At least with helicopters, they can generally hear that one is nearby, and try (try!) to hide. With a JDAM, the asset can be at a slant of 15 miles or so, totally out of ear and eye range. They think they're the cool kids in school, getting away with all manner of nefarious shit...

...and suddenly, BOOM! That Gucci little spider hole they've been shoring up with mud bricks and filling with PKMs for the last week and a half is blown right back into conformity with the sand and scrap metal that the rest of the goddamned country is made of.

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