The homemade explosive used by Brussels suicide bombers is a chemical nightmare
One thing Brussels authorities seem to have figured out, however, is the type of explosives suicide bombers set off during the attacks.
Frederic Van Leeuw, Belgium's chief prosecutor in the case, told reporters on Wednesday that investigators found 33 pounds of homemade explosives at a house used by the two bombers who struck Brussels Airport, according to the Associated Press. Those two explosions, combined with a third in Belgium's subway, injured at least 270 people and left 34 dead.
Police also found nails - presumably to serve as shrapnel - and other raw materials for making explosive vests at the residence, according to The Chicago Tribune.
The key explosive ingredient discovered, said Van Leeuw, is a compound called triacetone triperoxide, or TATP - a crystalline powder that is a nightmare to terrorists as well as authorities.
An unstable white powder
TATP is easy to make and hard to detect, but is also incredibly unstable. In fact, all it takes is a firm tap to explode TATP with a force that's about 80% as strong as TNT. (Which is why it has gained an infamous reputation as "the Mother of Satan" among terrorists who make it, according to The Future of Things.)
The infamous "shoe bomber" used TATP in 2001, as did terrorists in London in 2005 and 2006. The chemical was also in bombs detonated at the University of Oklahoma in 2005 and Texas City in 2006, according to explosives researchers at Northeastern University.
And, most recently, it was used in the November 2015 terrorist attacks on Paris.
"TATP and other explosives of the peroxide family are used extensively by terrorist organizations around the world because they are easy to prepare and very difficult to detect," Ehud Keinan, a chemist at the Technion-Israel Institute of Technology, said in a 2005 press release about his research of the chemical.
You might recognize two chemicals in TATP's full name - triacetone triperoxide - because they're ingredients you can find in your local pharmacy's cosmetics and first aid aisles.
"TATP can be easily prepared in a basement lab using commercially available starting materials," according to GlobalSecurity.org, which also notes "it's easy to blow yourself up when you make it."
Jimmie Oxley, an explosives researcher at the University of Rhode Island, told Tech Insider by email last year that making TATP is as easy as "baking a cake."
"We have done a lot of work trying to prevent its synthesis," wrote Oxley, who has experimented with adding trace chemicals to hydrogen peroxide in hopes of foiling TATP's homemade production. "It isn't easy to do and the ingredients are very common."
Chemistry of a nightmare
One reason TATP is difficult to detect is because it does not contain nitrogen, a key component of homemade "fertilizer" bombs that security scanners are now very good at finding.
Each molecule contains only hydrogen, oxygen, and carbon - some of the most common elements on Earth - shaped in a ring.
So where does it get its explosive energy, if not by heating?
It wasn't until 2005 that Keinan figured out detonating TATP is more like a massive air blast than a fire bomb. When a crystal of the explosive is rattled hard enough, each solid molecule instantly breaks into four gas molecules.
"Although the gas is at room temperature, it has the same density as the solid, and four times as many molecules, so it has 200 times the pressure of the surrounding air," according to the release about Keinan and his colleagues' 2005 study of TATP.
"This enormous pressure - one-[and-a-half] tons per square inch - then pushes outward, creating an explosive force" that's on par with TNT, states the release.
"In a TATP explosion, the gas molecules give up their energy of motion to the surroundings, in the process creating the shock wave that does the damage."
Can we detect it?
Scientists are now working feverishly to create practical ways to find TATP before it can be used to kill innocent people.
ACRO Security Technologies, a company founded by Keinan, has created a disposable marker-size "peroxide explosives tester," or ACRO-P.E.T.
"The ACRO-P.E.T. provides an immediate answer to whether a suspicious material that has been discovered somewhere ... contains even minute quantities of a peroxide-based explosive," Keinan told The Future of Things.
Other researchers are working on ways to find TATP when it's being transported, and without the need for a direct chemical test like Keinan's device.
In 2011, for example, scientists at Hitachi in Japan created a machine that sucks in air from around a passenger and - in two seconds - can sniff out minute traces of TATP.
A German research group also that large amounts of TATP can be detected in transit. Because the chemical is so touchy, they say in their study, it's usually dissolved in a special liquid before being moved around - and that fluid's unique odor is what they hope security scanners of the future could sniff out.
Warning: We have purposefully omitted key details about TATP's manufacture. Do not attempt to make it or any other explosive, for that matter.