NUCLEAR WARHEADS
An extract of “The New Era of Nuclear Strategy : From Cold War Arsenals To Nuclear Sufficiency” Amazon publisher
Nuclear warhead models can be counted in the hundreds. Initially, the aim was to maximize power. The transition from fission-atomic weapons to thermo-nuclear weapons, where the power of the explosion comes from the fusion of hydrogen, has made this possible. All nuclear countries have made the move. 225
Human-scale Explosive Devices
First it has been a race for power then came the race for light weight to ensure easier missile delivery. More precisely, the progress made in energy density. For the first warheads, 50 kilograms were needed to deliver one kiloton of power. Today, for advanced warheads, a kiloton "weighs" between 0.5 and one kilogram.
The volume and shape of the payload are the characteristics that determine the missiles' ability to deliver the bombs. The following figure shows the extent to which American missiles have evolved, revealing that bombs are now on a human scale. They are currently one meter high or less cones
Here, no longer a closely guarded secret, is the plan for a 300 Kt W-87 warhead to be found under the nose cones of American intercontinental missiles.
An Absolute Safety System
An inescapable safety system must prevent any unintended explosion of the bombs, whatever the circumstances.
The safety of the bombs is guaranteed by a whole series of measures based on a fundamental principle: an explosion is only permitted if the strict conditions of use that have been programmed (altitude, timing) are met. Mechanical devices, electronic assemblies and software combine to create locks, barriers, and safeguards.
- Blocking the critical mass mechanism. The presence of inert material in the cavity of the fissile material sphere makes it mechanically impossible to compact the critical mass. This buffer is evacuated when the bomb is armed,
- The creation of an "exclusion zone" inside which the electronic device controlling the detonation of the bomb is located. This zone is electrically isolated and shielded, and cannot be disturbed by external radiation,
- The firing device is isolated from the charge by a "door" mechanically activated when the bomb is armed: a "strong link",
- The bomb is definitively disarmed if an event (violent shock, fire, explosion, etc.) occurs, either due to the crash of the carrier (aircraft) or any external action,
- Finally, once the device is armed, a last level of "environmental sensing devices" (ESDs) prevents the weapon from detonating unless it is close to its programmed detonation point. This device takes into account parameters such as acceleration during the drop phase, temperature, and pressure. If these parameters are not detected in a suitable sequence and within an acceptable range of values, the explosion remains prohibited.
These features are found in the B61-12 bomb used by NATO's European forces. It should be noted that the bomb's power is adjustable, to enable flexible tactical use while minimizing collateral effects.
The architecture of nuclear devices no longer holds any secrets. The plans that were once classified as top secret are now accessible on the web. The secrets lie elsewhere: in the production processes, in the design of the uranium enrichment facilities.
Edouard D Valensi
