The recent failed car-bomb attempt in NYC appears to be a clear example of the issues I discussed in this post relating to the difference between learning the theory of making bombs and actually doing so with the materials you have to hand in the local environment.
Reportedly a street vendor spotted smoke coming out of an SUV which had been abandoned in Times Square, alerted a police officer who then called in the bomb squad. When the VBIED was made safe and dismantled it was found to be made up of three barbeque propane tanks, eight bags of ‘non-explosive grade’ fertilizer, petrol and some commercial firecrackers. The detonator appears to have been connected to couple of alarm clocks, suggesting this was not intended to be a suicide attack. It seems that the intent was to use the firecrackers to explode the fuel containers. As will be seen below, this is an unlikely way to try to cause gas canisters and fertilizer to explode.
Interestingly, an individual who has been arrested by the US authorities had apparently recently returned from a trip to Pakistan, something that has been seen in suspects involved in previous attacks and plots.
On first inspection, this bears a strong resemblance to the Summer 2007 attempted VBIED attacks in London, perpetrated by two Iraqi medical staff working in the UK. In that incident, one VBIED, which was parked outside a famous London nightclub (Tiger Tiger), was spotted giving off smoke and the authorities were able to disarm the device. A second VBIED had been towed by London’s parking authorities because the bombers failed to put a ticket on it. Both devices were made up of petrol and gas canisters and were described as ‘amateurish’ efforts. Before they could be arrested, the two men involved tried to mount a hasty suicide VBIED attack on Glasgow airport, again using an SUV containing gas canisters and petrol. The main result of this attack was the two men managing to set themselves on fire, one dying later from his injuries.
Improvising jihadist bomb-makers appear to have something of a fascination with the use of propane gas canisters. Presumably this arises from their reading of online bomb-making instructions which advise them to use these pressurized containers to enhance the power of their explosive devices. However, as noted in this post, such instructions may, at best, be inadequate, or at worst, plain wrong. Consider the case of Dhiren Barot, a British national found guilty of conducting surveillance against potential targets in the UK and the US, and with plotting a number of outlandish attacks involving radioactive material gleaned from thousands of smoke detectors and the ‘gas limos’ plot. In the latter, Barot suggested that filling limousines with a large number of propane/butane canisters which ‘if carefully orchestrated, can be as powerful as exploding TNT’.(1)
Barot was given a 40 year sentence for his activities. However, his defence team appealed the sentence on the grounds that his plans were amateurish and unlikely to be effective if ever put into practice. As part of the appeal proceedings, an expert witness stated that:
“In general, the overall project offers up what appears to be a well devised plan but is perhaps better viewed as a professional-looking attempt from amateurs who did not really know what they were doing. If pressurised cylinders of flammable gas (with or without oxygen as additional cylinders) were assembled as described and were the heat-producing ‘add-ons’ (e.g. napalm) included, then, on setting off the contraption, there would be a high likelihood that a fire source at least would be produced. An explosive event might occur particularly if explosive substances were present. However, the expectation of an explosive yield of 370kg TNT equivalent from the basic ‘main charge’ cylinders is unrealistic since the 37 propane cylinders (each of which is estimated as being able to produce a 10kg TNT equivalent yield) are distributed between three limos and it is highly improbable that they would all produce their maximum explosive effect simultaneously. That notwithstanding, the potential for severe damage, disruption and injury in the area concerned is present and is evidently intended”.[Emphasis added](2)
Considering this and other expert testimony, the court concluded that:
“The Gas Limos Project was superficially attractive, but in fact amateurish. It combined different proposed methods of creating explosions and fire that were mutually incompatible. The Gas Limos and their contents were intended to give rise to a massive cumulative explosion. This would never have occurred in practice. The greatest explosive hazard would have occurred if gas had been released into a confined space and ignited if and when it had reached a mixture with air that fell within the explosive limits. This would not have been easy to achieve, and would certainly not have been achieved had the combustible materials that were supposed to be placed around the gas cylinders been ignited at an early stage. This said, the proposed contraptions would undoubtedly have been very hazardous. Precisely what harm they might have done if attempts had been made to ignite or detonate them could not reliably be predicted”.[Emphasis added](3)
So, while the intent was certainly there, and there would likely have been a large fire or explosion if the gas had been vented into a confined space and ignited (akin to an accidental domestic gas explosion), the use of this type of canister as a means of delivering a VBIEd attack appears to be ineffective.
So, if repeated efforts to use domestic gas canisters as explosive charges have failed (or were unlikely ever to work as intended), as seen most recently in New York, why do aspiring jihadists (and these are the individuals who have got far enough along the path as to operationalise their intent) keep making the same mistakes? Well, for one, if their main source of instructional material is incorrect, then it is unsurprising that they cannot make even crude functioning devices. Second, without some practical experience, bomb-making is a difficult activity, especially in an environment where precursor materials are difficult to access. Third, it is difficult to learn from the mistakes of your colleagues if you are totally compartmentalized from them. While the threat from dispersed, unconnected cells of amateurish individuals make it much harder to identify and interdict potential attacks, it also ha a significant impact on any given cell’s operational effectiveness. Without direct access to a knowledgeable bomb-maker or to resources such as reliable explosive material, mounting bomb-attacks is a complex and difficult undertaking, especially in a hostile security environment such as the US or UK.
Happily for their intended targets, aspirational jihadists seem to be failing to learn from their mistakes.
(1) ‘Rough Presentation for Gas Limos Project’, downloaded from Met Police website, 9 November 2006
(2)  EWCA Crim 1119 Case No: 200606248 A8, Dhiren Barot -and- R, 16/05/2007, para. 25