Apparently,the terrorists were traveling towards the glasgow airport with an off roader half filled with domestic butane cylinders.
Butane is a hydrocarbon,which is highly inflammable,but how good is it at exploding?
To explode,the gas needs oxygen and ignition source.The gas air mixture must be between 2% and 5%.If it is below 2% or above 5%,it will still burn but will not explode.
The autoignition temperature of butane is around 450 C
.At this temperature,the gas will auto ignite,without any ignition source,such as lighter or flame or spark.
From the news reports i saw on various news channels,the terrorists stopped the vehicle,poured petrol inside it,ignited it and then drove it into the airport.
Looking at all this,they were planning to explode the gas cylinders under the effect of heat.
If the gas cylinders were to explode,they needed to be heated up to a certain degree,where the internal pressure of the gas was above the designed maximum pressure that the cylinder walls could take.
the domestic cylinder is made up of 2-3 mm thick mild steel sheet,which is welded to make a bottle shape.The usual maximum pressure for which these cylinders are made is 1000psi.At this pressure the weakest part of the cylinder will give way and the gas will escape a t a very high velocity.
If at the time of the structural failure of the gas cylinder,the gas is at at it's auto ignition temperature,it will ignite immediately upon contact with oxygen,but that won't be an explosion,but an ignition.If the gas is released at lower than the auto ignition temperature,it will escape at high velocity,and may or may not come in contact with the source of ignition.
But the domestic cylinders which the terrorists were using are fitted with safety valves,which release small quantities of gas to avoid internal pressure from rising to dangerous levels.
For the terrorist's attack to be devastating,all cylinders had to reach high pressure,and then explode at the same time,which unless they had devised some ingenious way,was not very probable.
The cylinders could have heated up and then ruptured to release flammable gas,and for that to happen,their car had to be at fire for more than 10 minutes.Even then the cylinders would have ruptured one at a time or a few at a time.
So thank you al-qaeda for sending such dumb ass knuckle dusters,who apparently had no knowledge about flammable gasses :DD:DD:DD