March 22, 2015: Strategy Page
The U.S. recently successfully tested a JDAM (GPS smart bomb guidance) kit modified to work on a B61 nuclear bomb. The latest version of JDAM includes wings which enable the JDAM equipped bomb to glide up to 70 kilometers. But the main reason for a nuclear JDAM is not enabling the bomber to drop the bomb from a distance but so the B61 ground penetrating version can use a smaller sized explosion to get the same effect as a much larger explosion. Since JDAM lands the bomb within 30 meters of the aiming point a smaller nuclear explosion gets the same effect (on an underground bunker) as the old version that would only land within 150 meters of the aiming point. That means you only need a 30 kiloton nuke to take out a bunker instead of a much larger one of about 150 kilotons. This means less collateral damage and less fallout going into the atmosphere. Yes, even nukes can be ecologically sensitive.
The B61 JDAM is, like the B61 itself, hardened to prevent EMP (electromagnetic pulse) from damaging the electronics. Not a lot of adjustment is needed for the JDAM kit as the B61 has a shape similar to that of the non-nuclear bombs JDAMs are normally used on. The air force is spending over $700 million for the five year effort to develop the B61 JDAM kit. This kit will be tested to make sure it works from a B-52, F-15, B-2, F-16, F-35A and the European PA-200 Tornado
Meanwhile the $8 billion effort to refurbish the elderly B61 nuclear bombs is proceeding but budget cuts may delay the number to be refurbished (to about 400) and the delivery date (from 2017 to 2020). Getting this refurb into service means that the last American megaton (million tons of TNT equivalent) bomb, the B83 can be retired before it ages out of usefulness. Nuclear weapons have electronic and chemical components that degrade with and either have to be refurbished or retired because of age-related ineffectiveness.
The effort to refurbish one of its oldest warhead designs, the B61, began back in 2006. The B61 is a thermonuclear ("H-Bomb") weapon that is available in several versions. The ones being refurbished are those designed for penetrating the earth before going off. Most nuclear bombs with higher yields ones (300-400 kilotons) are detonated in the air rather than allowed to hit or penetrate the ground. Some 3,200 B61s were built since the design went into service in the mid-1960s, and about half of those remain available for use.
The refurbed warheads will be good for another two decades. The basic B61 nuclear bomb weighs 320 kg (700 pounds), is 330mm in diameter and 3.56 meters (11.7 feet) long. They are delivered by aircraft as bombs. Back in 2006 about 400 B61s were still stored in Europe and these are not being refurbed. Interestingly, the W80 nuclear weapon used on some two thousand cruise missile warheads are not being refurbished either. Without the refurb all these older warheads will be useless by the end of the decade and that fits in with the continuing arrangements between Russia and the United States to reduce their Cold War era nuclear arsenals.