Thread by @johnismay

Some quick math on #BeirutBlast: though it's difficult to precisely measure the explosive yield of 2,750 tons of AN due to age/deterioration, the publications I have say in a worst-case scenario it could have had as high as 42% the power of TNT nytimes.com/2020/08/05/wor…

That would mean the explosion could have had the force of 2.3M lbs or 1,155 tons of TNT. You can then use U.S. military publications to determine the resultant blast overpressure in pounds per square inch (psi) at various ranges

The pubs I used as an EOD Tech rely on something called "k-factors," which give you a number to plug into a simple equation:

d = k (NEW)^(1/3)

d = distance
k = k-factor
NEW = net explosive weight, as measured in TNT

So if you want to know at what distance you could expect to experience a given level of blast overpressure, you multiply the k-factor for that psi level by the cube-root of the net explosive weight

K6 = 27 psi
"Unstrengthened buildings will be destroyed. Personnel will be killed by blast, by being struck by debris, or by impact against hard surfaces. Transport vehicles will be overturned and crushed by the blast."

K9 = 12 psi
"Unstrengthened buildings will suffer severe structural damage approaching total destruction. Personnel will be subject to severe injuries or death from direct blast, building collapse, or translation."

K11 = 8 psi
"Unstrengthened buildings will suffer damage approaching total destruction. Personnel are likely to be injured seriously due to blast, fragments, debris, and translation. There is a 15% risk of eardrum rupture."

K18 = 3.5 psi
"Direct propagation of explosion is not expected.
Delayed propagation of an explosion may occur [...] There is a two percent chance of eardrum damage to personnel."

K24 = 2.3 psi
"Occupants of exposed structures may suffer temp. hearing loss or injury from blast effects, building debris and displacement. [.] personnel in the open are not expected to be killed or seriously injured by blast effects, fragments and debris may cause injuries."

K30 = 1.7 psi
"Unstrengthened buildings can be expected to sustain damage that may approximate 10% of their replacement cost. Occupants of exposed, unstrengthened structures may be injured by secondary blast effects, such as falling building debris."

K50 = 1 psi
"...buildings can be expected to sustain damage that approximates 5% of their replacement cost. Personnel in buildings are provided a high degree of protection from death or serious injury; however, glass breakage and building debris may still cause some injuries.

K328 = 0.065 psi
"This is the distance used for overpressure for public withdrawal distance (PWD) from intentional detonations"

Understand that this formula was developed for bomb techs to make quick field-expedient estimates with paper and pencil. This, for the moment, is the best I can do with the information I have. As more data becomes available, I'll naturally reevaluate these calculations

This approximation cannot include all scenarios bc blast overpressure waves can bounce, reflect, and do strange things in reality. A large building standing between the explosion and a smaller building might take more of the brunt and shield the structure behind it to a degree

I've been asked a lot about the reddish color of the smoke plume from the #BeirutBlast, and I trust Dr. Lance here. She knows the chemistry far far better than I ever will

https://twitter.com/UnderwaterLance/status/1291026617419075585