London Bombing Details

Interesting details about the bombs used in the 7/7 London bombings:

The NYPD officials said investigators believe the bombers used a peroxide-based explosive called HMDT, or hexamethylene triperoxide diamine. HMDT can be made using ordinary ingredients like hydrogen peroxide (hair bleach), citric acid (a common food preservative) and heat tablets (sometimes used by the military for cooking).

HMDT degrades at room temperature, so the bombers preserved it in a way that offered an early warning sign, said Michael Sheehan, deputy commissioner of counterterrorism at the nation’s largest police department.

“In the flophouse where this was built in Leeds, they had commercial grade refrigerators to keep the materials cool,” Sheehan said, describing the setup as “an indicator of a problem.”

Among the other details cited by Sheehan:

The bombers transported the explosives in beverage coolers tucked in the backs of two cars to the outskirts of London.

Investigators believe the three bombs that exploded in the subway were detonated by cell phones that had alarms set to 8:50 a.m.

For those of you upset that the police divulged the recipe—citric acid, hair bleach, and food heater tablets—the details are already out there.

And here are some images of home-made explosives seized in the various raids after the bombings.

Normally this kind of information would be classified, but presumably the London (and U.S.) governments feel that the more people that know about this, the better. Anyone owning a commercial-grade refrigerator without a good reason should expect a knock on his door.

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Posted on August 5, 2005 at 4:03 PM • 39 Comments

Comments

Arik • August 5, 2005 4:24 PM

I think it’s nice that (for whatever reason) the powers that be decide that wide knowledge about this is better than keeping it secret.

It’s a balance between raising public awareness to the specific tale-tales as a mitigating factor and shedding light on bomb-making recipes as a contributing factor, and it seems like public awareness won.

DL • August 5, 2005 4:27 PM

The only thing special about standard commercial refrigerators is that they are optimized for storing bulky items and lack consumer features like fancy shelves, water dispensers, etc. There is no reason they could not have used plain residential refrigerators instead.

Refrigrators (commercial included) are way too common to consider as a warning sign of possible terrosism.

I wonder how long it will be before someone here makes a crack about being afraid to buy a new fridge for fear of being shot in the head.

Bruce Schneier • August 5, 2005 4:53 PM

“Is it possible that the second bombing failed because the explosive had degraded?”

The second bombings seemed much more amateurish on a whole bunch of levels. I started writing a post on that, but dropped it because it was just too speculative.

Graham • August 5, 2005 4:54 PM

You obviously do no background research, have no problem jumping to wild conclusions, and are generally very hypocritical in your approach.

First, NYPD released this by mistake, Scotland Yard specifically asked them not to do so.

Secondly, please explain why disproportionate interest should be put on refrigerators? I know nothing about explosives but surely this is just another failure of imagination? There must be explosives which don’t need to be kept in refrigerators? And trying to regulate (however voluntarily) the sale of refrigerators is almost as boneheaded than trying to stop people sharing MP3s.

Yet when it comes to defensive thinking, you seem to think protecting concert halls and movie theaters is just as important as protecting trains? Have you lost all concept of the tradeoff? Clue: the same number of people may be vulnerable but transport is essential infrastructure and costs billions in lost revenue when down, movie theaters aren’t.

Your pundit status is well deserved, but you seem to be milking it for all its worth without worrying too much about spewing snake oil.

Ian Mason • August 5, 2005 4:58 PM

@Bruce

“Oops”

Don’t sweat it. Often the only way the British public find out what our government is up to is when someone files an FOI act request in the States! There is a culture of secrecy in public British life that is more often counter productive than not. Now at least the British public know to consider being suspicious of someone buying hydrogen peroxide and citric acid at the same time.

Matthew Skala • August 5, 2005 5:06 PM

Not that this is the point, of course, but I sure wouldn’t trust that explosives recipe. The author is measuring dry chemicals by volume, not adjusting the amounts according to their variable purity, and consistently gets the formula for hydrogen peroxide wrong – which implies that s/he doesn’t know what the formula means and is just parrotting some other source. The comment at the end about some batches being much stronger than others implies that the whole process is poorly controlled. This isn’t baking a cake, the amounts have to be right; and actually, with technique at sloppy as this sounds, a cake wouldn’t come out very well either.

Mary R • August 5, 2005 5:18 PM

Ha! When the police starting knocking down doors of yuppie twits with commercial kitchens in their fancy condos, I’ll believe the cops aren’t profiling.

Mark El-Wakil • August 5, 2005 5:28 PM

If anyone with purchased commercial refrigeration is interrogated / interviewed, wouldn’t it then make more sense for a would-be terrorist to construct a cooling system in addition to the bomb ingredients?

I don’t really see the police going around like that actually being effective.

David Currie • August 5, 2005 5:39 PM

Heh, I found the comment:
“Anyone owning a commercial-grade refrigerator without a good reason should expect a knock on his door.”
amusing, given what you’ve been writing about the problems with profiling lately. They’ll just start storing stuff with people who have good reasons to own these refrigerators.. 🙂

lengo • August 5, 2005 5:39 PM

HMDT is so bad that I doubt any savvy person will use it. First of all it is not reasonable to make the whole bomb from primary explosive (they are commonly used only as initiators for secondary and ternary), and there are a lot of other substances which are much more stable and require only commonly available components, e.g., acetone peroxide can be made from hair bleach (hydrogen peroxide), acetone, and sulfuric acid (electrolyte in various types of lead-acid battery).

“the powers that be decide that wide knowledge about this is better than keeping it secret.”

This reminds me crypto books I read as a kid. They explain that Cardan’s screen is very secure system because there are so many possible keys, etc-etc. Since in reality this cipher can be trivially broken it is possible to guess that this disinformation in popular mathematical books was there on purpose — to make life easier to code-breakers: if somebody thinks that he knows the answer he is not going to search for it.

Davi Ottenheimer • August 5, 2005 5:54 PM

I think it is also useful to note that the man in charge of the Met said it took seven days for Police to enter the building due to the nature (volatility?) of the explosives, and that is one of the reasons for extending a detention period beyond 14 days. So, on the one hand they are talking about early warning signs, and other other they are saying they need more time to build a case after the fact…

tom • August 5, 2005 6:22 PM

The “images” link to abcnews.go.com is broken, it has an extra character at the end.

Davi Ottenheimer • August 5, 2005 7:20 PM

Not only is the recipe available online, but so too are some amazingly simple methods to stabilize it without need for the kind of cooling described above.

Matthew Skala makes a good point about the risks of online recipes. I made this salmon with whiskey once…

This might be an even more controversial link:
http://www.fortliberty.org/military-library/Improvised_Primary_Explosives.pdf

This “fort liberty” site claims to be a pro-America group trying to protect themselves from “Muslim extremists”, Republicans and Democrats…apparently by publishing guides on to how to make explosives like HMDT.

Paul • August 5, 2005 7:52 PM

The linked recipe for the explosives used is rather crude. There are far better sources for such information available, as well as communities dedicated to helping get the formulations and preparations right. For bonus points, see what you can find in the US patent office archives, as well as foreign archives of the USPTO… you’ll find more interesting information in the non-redacted foreign archives…

@lengo:
You say “much more stable” and then go on to use the words “acetone peroxide” in the same sentance.
HAHAHAHA… you’re quite amusing, you know that?

Ari Heikkinen • August 5, 2005 9:36 PM

Trying to make explosives from instructions downloaded from the internet is pretty stupid. Explosives are something you don’t generally want to try to make (or even handle) without proper training.

Chris Wright • August 5, 2005 10:31 PM

But what else am I supposed to do with that stump in the back yard that just won’t budge?

Ned B. Kelly • August 6, 2005 10:11 AM

“There are far better sources for such information available, as well as communities dedicated to helping get the formulations and preparations right.”

One such place being:

http://www.roguesci.org/theforum/index.php?

which has been around since 1998, and recognized by the other ‘community’ forums as being the superior one for advanced improvised E&W information.

Given the general (lack of) technical knowledge of journalists and the (likely) disinformation of the police, it’s no wonder they got the acronym ‘HMDT’ wrong.

In fact, it could have been quite possible to have made HDN, which is almost as easily made as HMTD, using the same Hexamine, but is nearly on par with RDX, which it’s converted to by an additional nitration step.

Though, from the pictures, its obvious that a cool explosive was used, as there was no fire, no scorching of the debris or bodies, and given that there were intact windows in the bus, that it was a low velocity explosive, not a a ‘Military-Grade’ explosive as first mentioned, which would have shattered the windows, while a low-velocity explosive pushes them out intact.

Peroxide and nitrate based explosives are likely candidates, of which HMTD is one.

We had the explosive type identified the first day it happened, far ahead of the press and their police handlers. 🙂

Al • August 6, 2005 12:33 PM

“I wonder how long it will be before you can’t buy refrigerators over the counter any more”

I’m afraid this has always been the case, you generally wheel them round the side as they are heavy

Ari Heikkinen • August 6, 2005 2:52 PM

Why would anyone even try to make explosives themselves when there’s easy ways to steal them. I remember some 20 years back when some fellow kids in the neighborhood went to a construction site and stole a bunch of detonation caps and dynamite from there and then blowed the caps in the new years eve (while us others were blowing firecrackers). Still, even those kids didn’t dare to try the dynamite and just detonated the caps.

With self made explosives (although I’m not an explosives expert by any means) I’d assume the problem would be to make them stable (that is, to make them safe) and not so much to make them effective.

Rapid_Right_Winger • August 7, 2005 3:36 AM

I’m appalled that people are allowed refrigerators. I think it’s time we took peoples fridges away. People who have fridges are unpatriotic. I also think the ingredients for the bomb shouldn’t of been put out over the internet. Clearly the internet is a tool of the devil.

Rabid_brainless_right_winger • August 7, 2005 3:38 AM

I’m appalled that people are allowed refrigerators. I think it’s time we took peoples fridges away. People who have fridges are unpatriotic. I also think the ingredients for the bomb shouldn’t of been put out over the internet. Clearly the internet is a tool of the devil.

Matt C • August 7, 2005 5:47 AM

@Ari: “Why would anyone even try to make explosives themselves when there’s easy ways to steal them.”

In the context of the UK, after more than 30 years of the IRA et al. making a right nuisance of themselves, explosives any more powerful than those used in retail fireworks are extremely tightly regulated (hence David Copeland’s use of fireworks for the devices he planted in London a year or two back).

IRA HE (Semtex etc.) was sourced from outside of the UK, something that is likely much more difficult these days, now that the Libyans and other erstwhile suppliers are ‘going straight’.

Stealing and/or buying on the UK black market (such as it is) is probably a complete non-starter for would-be terrorists who wish to keep an extremely low profile prior to their attacks, thus they resort to home-made HE.

Bruce Schneier • August 7, 2005 5:49 PM

“I’m appalled that people are allowed refrigerators. I think it’s time we took peoples fridges away. People who have fridges are unpatriotic. I also think the ingredients for the bomb shouldn’t of been put out over the internet. Clearly the internet is a tool of the devil.”

When our beer is warm the terrorists have won. Or maybe the British.

Rob Mayfield • August 7, 2005 6:14 PM

No need to take peoples fridges away unless they fit the profile – if they are a bottle-blonde, then take the fridge away – unless they like beer and arent English.

Chung Leong • August 8, 2005 1:44 AM

If you installed a hundred sunlamps in your home, you can expect some attention from the coppers too. The police is doing the right thing in telling the public exactly what sort of suspicious activities to look for. Had the information been available earlier, someone could have tipped the London police and thus perhap prevented the 7/7 bombing.

Ned B. Kelly • August 8, 2005 11:38 AM

Roguesci.org is still up and running.

Perhaps you’ve been blocked by your ISP, as per some Anti-Terror law in your country?

There’s no such thing as TATP (TriAcetone TriPeroxide). That term has gained credibilty through simple repetition…almost like an urban legend.

There are isomers of Acetone Peroxide (AP), those being mono-, di-, tri-, and tetra- of acetone peroxide.

Increased isomerization increases stability, with the mono- being a very sensitive liquid, with the di- and higher isomers being solids, with the di- being very impact and friction sensitive, while the tetrameric is relatively inert.

Having seen the pictures of the ‘bombs’ that the latest batch of brit Jihadi’s made up, it’s obvious these guys had NO clue what they were doing, as far as the weapon designs went.

Airsoft shrapnel? :p

As for the fridge, that was used to cool the AP mixture down to form the trimeric form of AP, which is the most stable of the easily made isomers, as the tetrameric form requires tin catalysts, while the lesser isomers require only simple mineral acids.

People make explosives, rather than stealing them, because of lack of availability from local sources, security at those sources, deniability of orgin, sheer weight (lot easier to home-make 2 tons of ANFO than TNT), or special target effects desired.

The people in charge of security would be far better served by stationing ‘decoy’ dogs (suggested elsewhere) at the entrances of the subways, dogs which aren’t trained for detecting explosives/drugs, but the terrs wouldn’t know this, especially if the few trained dogs are rotated through at random.

Keeps ’em guessing, and might actually deter some of the spontaneous untrained wann-be Jihadi’s.

DarkFire • August 10, 2005 4:49 AM

Ah I stand corrected. I was merely repeating something I heard elswhere.

I take it then that the propper designation would in fact be tri-acetone peroxide or TAP?

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