Ivano-Frankivsk got zero attention in the news. It was an old mine turned in 1955 into a nuclear weapons storage facility. It was emptied in 1993 when the weapons were transferred to Russia. In 2018 it was reopened as the barracks for 2 battalions of 10th Mountain Assault Brigade. Apparently also a conventional weapons storage, since the Ukrainians announced several secondary explosions on the site. It’s supposed to be nuclear missile proof, though, so either it actually wasn’t or there was a load of ammunition leaving or entering the place.
A warhead that weighs 500 kg travelling at hypersonic speed carries kinetic energy equivalent to the explosive force of 4000 odd kg of TNT. Delivered directly to the roof of an underground bunker, the kinetic punch would be greater than a small nuclear bomb exploding in the air above. The blast ‘overpressure’ would be as lethal as explosions and flying objects.
Just like with other previous weapons of such a nature, the ‘overpressure’ can be the killer, not just explosions and flying objects.
sciencedirect | Vapor cloud explosions are caused by the rapid combustion of flammable gas, mist, or small particles that generate pressure effects due to confinement; they can occur inside process equipment or pipes, buildings, and other contained areas. A vapor cloud explosion can be either a deflagration or a detonation (the distinction is important when deciding on whether or not to use a flame arrestor in pressure relief systems).
A deflagration occurs when a flame front propagates by transferring heat and mass to the unburned air-vapor mixture ahead of the front. The combustion wave travels at subsonic speeds to unburned gas immediately ahead of the flame front. Flame speeds range from 1 to 350 meters per second. At low speeds there is little effect from the blast overpressure while at high speeds, peak overpressures can be as high as 20 times the initial pressure. Most vapor cloud explosions are deflagrations.
A detonation occurs when the flame velocity reaches supersonic speeds above 600 meters per second (they are generally in the 2000 to 2500 meter per second range). Peak overpressures can be 20 to 100 times the initial pressure. Detonation can be initiated either by use of a high explosive charge or from a deflagration wave that accelerates due to congestion and confinement. Certain chemicals are more prone to create detonations than normal hydrocarbons. These include ethylene, acetylene, and hydrogen.
The United States Environmental Protection Agency (EPA) provides tables and simple equations for some of the more common chemicals to calculate the distance of the overpressure waves. These tables are generally conservative, i.e., they predict greater impact than would be likely to actually occur. Nevertheless, they do provide a useful starting point.
Blast effects
The calculation of explosion effects is a complex topic involving many variables. Table 9.5 shows some overpressure values with typical effects.
Table 9.5. Effect of Overpressure
| Overpressure (psi) | Damage |
|---|---|
| 0.15 to 1.0 | Glass failure |
| 1.0 | Person knocked down |
| 0.4 | Minor structural damage |
| 2.0 | Partial collapse of walls and roofs |
| 3.0 | Eardrum damage |
| 3.0 to 4.0 | Light buildings demolished; storage tanks ruptured |
| 5.0 to 7.0 | Complete destruction of domestic buildings; loaded rail-cars overturned |
| 10.0 | Total destruction of buildings |
| 15.0 | Lung damage |
| 35.0 | Fatalities |
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