Wednesday, February 27, 2008

Tsar bomba is serious business

The device offically designated RDS-220, known to its designers as Big Ivan, and nicknamed in the west Tsar Bomba (and referred to as the Big Bomb by Sakharov in his Memoirs [Sakharov 1990]) was the largest nuclear weapon ever constructed or detonated. This three stage weapon was actually a 100 megaton bomb design, but the uranium fusion stage tamper of the tertiary (and possibly the secondary) stage(s) was replaced by one(s) made of lead. This reduced the yield by 50% by eliminating the fast fissioning of the uranium tamper by the fusion neutrons, and eliminated 97% of the fallout (1.5 megatons of fission, instead of about 51.5 Mt), yet still proved the full yield design. The result was the "cleanest" weapon ever tested with 97% of the energy coming from fusion reactions. The effect of this bomb at full yield on global fallout would have been tremendous. It would have increased the world's total fission fallout since the invention of the atomic bomb by 25%.

A shock wave in air was observed at Dickson settlement at 700 km; windowpanes were partially broken to distances of 900 km. All buildings in Severny (both wooden and brick), at a distance of 55 km, were completely destroyed. In districts hundreds of kilometers from ground zero, wooden houses were destroyed, and stone ones lost their roofs, windows and doors; and radio communications were interrupted for almost one hour. The atmospheric disturbance generated by the explosion orbited the earth three times. A gigantic mushroom cloud rose as high as 64 kilometers (210,000 ft).

The Tu-95 was painted with a special white reflective paint to protect it from the thermal radiation of the fireball. The airborne laboratory plane was also covered with the same paint. In clear air, the 50 Mt test was capable in principle of inflicting third degree burns at a distance of up to 100 km.

The area of effectively complete destruction extended to 25 km, and ordinary houses would be subjected to severe damage out to 35 km. The destruction and damage of buildings occurred sporadically at much greater ranges than this due to the effects of atmospheric focusing, an unpredictable but unavoidable phenomenon with very large atmospheric explosions that is capable of generating localized regions of destructive blast pressure at great distances (even exceeding 1000 km).

It is safe to assume that the 100 Mt bomb was a very conservative design - one that pushed no technical envelopes save for size. The two principal reasons for thinking this are the extremely compressed development schedule, and the very high profile of the test


There was no previously existing military requirement for a 100 megaton weapon - such weapons are virtually useless for military purposes. The Soviet Union had only one delivery system capable of carrying a weapon of this size - a handful of the relatively slow prop-driven Tu-95 bomber - and it was incapable of intercontinental range with a payload this large. A 100 Mt weapon can level urban areas in a zone 60 km wide, cause heavy damage in a zone 100 km across, cause 3rd degree burns in a region 170 km across (only a bit smaller than the width of West Germany) and eye damage to 220 km. Such a weapon can only be used as a means of destroying an entire urban region - a major urban complex including suburbs and even neighboring cities. This scale of destruction is much larger than any discrete urban area in Western Europe. With its dense settlement, use of such a weapon in Europe is equivalent to an attack on a major portion of an entire nation and its population. Fallout from a low altitude or surface burst in central England could produce lethal exposures extending into the Warsaw Pact nations; a similar explosion in West Germany could create lethal fallout as far as the Soviet border. Even in the United States there were only three urban regions at that time large enough to conceivably merit attack with such a weapon - New York, Chicago, and Los Angeles. On any smaller target it would be simple overkill. Even if the Tu-95 were able to reach Chicago, the closest plausible U.S. target, (which is doubtful given the enormous payload, far in excess of normal for long-range missions, and the added drag from the belly bulge required to house the bomb) it would have been detected crossing the North American early warning line and then been over U.S. and Canadian territory for 8 hours - ample time for jet fighters to intercept and shoot it down

This made me feel a little better until I realized they were talking about this with reference to military technology 50 years ago. I wonder how hard it would be to come up with a delivery system for this class of weapon today.

So there you have it, the most powerful weapon of destruction ever built. I can't hide my recent fascination with nuclear weapons of the most murderous kind - it just feeds off the fear I get watching and reading this stuff.

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