The truncated icosahedron geometry employed for the symmetrical shockwave compression of fission implosion devices.

The simplest nuclear weapon is commonly known as a gun-type device, because it achieves critical mass by forcing together two sub-critical masses of uranium through a mechanism very much like a gun that shoots a smaller wedge-shaped sub-critical mass into a larger sub-critical mass. This was the design of the “Little Boy” Hiroshima atomic bomb. The next level of complexity in nuclear weapon design was the implosion device, which relied upon conventional explosives to symmetrically compress a larger reflector/tamper sphere of U-238 into a smaller sphere of Pu-239, with a polonium-beryllium “Urchin” initiator at the very center. The scientists of the Manhattan project were so certain that the gun-type device would work that they didn’t even bother to test it, so the first nuclear device to be tested, and indeed the first nuclear explosion on the planet, was the Gadget device designed to be the proof of concept of the more sophisticated implosion design. It worked, and this design was used for the “Fat Man” atomic bomb dropped on Nagasaki.

These early nuclear weapon designs (conceptually familiar, but all the engineering designs are still very secret) are usually called First Generation nuclear weapons. The two-stage thermonuclear devices (fission primaries to trigger fusion secondaries, though most of the explosive yield still derives from fission) designed and tested a few years later, known as the Teller-Ulam design (and tested with the Ivy Mike device), were called Second Generation nuclear weapons. A number of ideas were floated for third generation nuclear weapons design, and probably many were tested before the Nuclear Test Ban Treaty came into effect (and for all practical purposes brought an end to the rapid development of nuclear weapon design). One of the design concepts for Third Generation nuclear weapons was that of a shaped charge that could direct the energy of the explosion, rather that dissipating the blast in an omnidirecitonal explosion. There are also a lot of concepts for Fourth Generation nuclear weapons, though many of these ideas are both on the cutting edge of technology and they can’t be legally tested, so it is likely that little will come of these as long as the current test ban regime remains in place.

According to Kosta Tsipis, “Nuclear weapons designed to maximize certain of their properties and to suppress others are considered to constitute a third generation in the sense that their design goes beyond the basic, even though sophisticated, design of modern thermonuclear weapons.” These are sometimes also referred to as “tailored effects.” Examples of tailored effects include enhanced radiation warheads (the “neutron bomb”), so-called “salted” nuclear weapons like the proposed cobalt bomb, electro-magnetic pulse weapons (EMP), and the X-ray laser. We will here be primarily interesting in enhancing the directionality of a nuclear detonation, as in the case of the Casaba-Howitzer, shaped nuclear charges, and the X-ray laser.

What I would like to propose as a WMD is the use of multiple shaped nuclear charges directing their blast at a common center. This is like a macroscopic implementation of the implosion employed in first generation nuclear weapons. The symmetry of implosion in the gadget device and the Fat Man bomb employed 32 simultaneous high explosive charges, arranged according to the geometry of a truncated icosahedron, which would result in a nicely symmetrical convergence on the central trigger without having to scale up to an unrealistic number of high explosive charges for an even more evenly symmetrical implosion. (The actual engineering is a bit more complicated, as a combination of rapid explosions and slower explosions were needed for the optimal convergence of the implosion on the trigger.) This could be employed at a macroscopic scale by directional nuclear charges arranged around a central target. I call this a macro-implosion device. In a “conventional” nuclear strike, the explosive force is dissipated outward from ground zero. With a macro-implosion device, the explosive force would be focused inward toward ground zero, which would experience a sharply higher blast pressure than elsewhere as a result of the constructive interference of multiple converging shockwaves.

A partially assembled implosion device of a first generation nuclear weapon.

The reader may immediately think of the Casaba-Howitzer as a similar idea, but what I am suggesting is a bit different. You can read a lot about the Casaba-Howitzer at The Nuclear Spear: Casaba Howitzer, which is contextualized in even more information on Winchell Chung’s Atomic Rockets site. If you were to surround a target with multiple Casaba-Howitzers and fire at a common center at the same time you would get something like the effect I am suggesting, but this would require far more infrastructure. What I am suggesting could be assembled as a deliverable weapons system engineered as an integrated package.

A cruise missile would be a good way to deliver a macro-implosion device to its target.

There are already weapons designs that release multiple bomblets near a target with each individual bomblet precision targeted (the CBU-103 Combined Effects Munition, more commonly known as a cluster bomb). This could be scaled up in a cruise missile package, so that a cruise missile in approaching its target could open up and release 12 to 16 miniaturized short-range cruise missiles which could then by means of GPS or similar precision location technology arrange themselves around the target in a hemisphere and then simultaneously detonate their directed charges toward ground zero. Both precision timing and precision location would be necessary to optimize shockwave convergence, but with technologies like atomic clocks and dual frequency GPS (and quantum positioning in the future) such performance is possible.

A macro-implosion device could also be delivered by drones flown out of a van.

A similar effect could be obtained, albeit a bit more slowly but also more quietly and more subtly, with the use of drones. A dozen or so drones could be released either from the air or launched from the ground, arrange themselves around the target, and then detonate simultaneously. Where it would be easier to approach a target with a small truck, even an ordinary delivery van (perhaps disguised as some local business), as compared to a cruise missile, which could set off air defense warnings, this would be a preferred method of deployment, although the drones would have to be relatively large because they would have to carry a miniaturized nuclear weapon, precision timing, and precision location devices. There are a few commercially available drones today that can lift 20 kg, which is probably just about the lower limit of a miniaturized package such as I have described.

The most elegant deployment of a macro-implosion device would be a hardened target in exoatmospheric space. Currently there isn’t anything flying that is large enough or hardened enough to merit being the target of such a device, but in a future war in space macro-implosion could be deployed against a hard target with a full spherical implosion converging on a target. For ground-based targets, a hemisphere with the target at the center would be the preferred deployment.

In the past, a nation-state pursuing a counter-force strategy, i.e., a nuclear strategy based on eliminating the enemy’s nuclear forces, hence the targeting of nuclear missiles, had to employ very large and very destructive bombs because nuclear missile silos were hardened to survive all but a near miss with a nuclear weapon. Now the age of land-based ICBMs is over for the most advanced industrialized nation-states, and there is no longer any reason to build silos for land-based missiles, therefore no reason to pursue this particular kind of counter-force strategy. SLBMs and ALCMs are now sufficiently sophisticated that they are more accurate than the most accurate land-based ICBMs of the past, and they are far more difficult to find and to destroy because they are small and mobile and can be hidden.

However, hardened, high-value targets like the missile silos of the past would be precisely the kind of target one would employ a macro-implosion device to destroy. And while ICBM silos are no longer relevant, there are plenty of hardened, high-value targets out there. A decapitation strike against a leadership target where the location of the bunker is known (as in the case of Cheyenne Mountain Complex or Kosvinsky Kamen) is such an example.

This is, of course, what “bunker buster” bombs like the B61 were designed to do. However, earth penetrating bunker buster bombs, while less indiscriminate than above ground bursts, are still nuclear explosions in the ground that release their energy in an omnidirectional burst (or perhaps along an axis). The advantage of a macro-implosion device would be that the focused blast pressures would collapse any weak spots in a target area, and, when you’re talking about a subterranean bunker, even an armored door would constitute a weak spot.

I haven’t seen any discussion anywhere of a device such as I have described above, though I have no doubt that the idea has been studied already.

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