3D printing has had a profound effect on the world we live in and is changing everything from medicine to manufacturing. Now scientists are putting this advanced technology to a new use, though, it could blow the whole place up.
Los Alamos chemist Alex Mueller is working with a team of scientists to create next generation incendiary devices by altering the composition of TNT. This will make more efficient devices, so the next generation could make today’s explosives look like fireworks, and could also save lives with controlled explosions and even safer compounds.
Microstructures make a massive difference
Slight changes to the microstructure can have a massive impact on the final explosion. 3D printing presents a world of opportunities when it comes to precise structures thanks to the layer by layer approach.
Explosives are separated out into low and high categories, based on their reactive qualities. They are considered low if they burn with a subsonic shock wave, or high if they detonate with a supersonic wave.
Conventional high explosives like TNT can detonate accidentally due to impact, or even a fire. So they are volatile compounds that are dangerous by their very nature.
Los Alamos is working hard on next generation explosives that can be hit with a hammer, run over with a car and set on fire without exploding. This will be a huge step forward for the industry.
Of course there is a trade-off, as the explosives need to actually detonate on command. So to achieve this level of safety, Los Alamos has concentrated its efforts on the hot spots that are created by air bubbles in the material. Inconsistent construction, with air bubbles almost at random, creates uneven hotspots. That makes TNT unpredictable.
From LEDs to IEDs
Mueller was working on LEDs, when he first started 3D printing. It became such an integral part of his work that he ended up hacking one to adapt it for his own specific needs.
“Because it’s a new technology, there’s this temptation to try and do everything with 3D printing,” Mueller said. “But new technology isn’t necessarily always better than the old way. Using a power drill as a hammer, just because it’s fancier, isn’t going to be better than using a hammer as a hammer. But in this case, the new technology has made the difference from impossible to possible.”
Through a series of lab tests, the team found that a chemical reaction follows the supersonic shock wave through the TNT and creates a number of hotspots in the compressed bubbles. The team profiled the hotspots and their impact on the shock sensitivity and volatility of each compound and structure.
“The ability to tailor sensitivity and the resultant energy release in the chemical reaction zone would be a holy grail in detonationphysics research,” Dattelbaum says. “Control and manipulation of structures at the microscopic scales through 3D printing is an exciting step toward achieving these goals.”
Explosives have specific energy
Part of what gives Conventional High Explosives the edge when it comes to pure power over Insensitive High Explosives is the way energy is released. With CHEs it is released aggressively, as you’d imagine with a detonation. It produces a chain reaction that devours all the base material.
With IHEs it there a slow release of energy with a number of reactions sparking in turn. This tends to leave a lot of waste explosive material that simply fails to ignite. That makes them inefficient, but a more efficient structure with this basic concept could be the perfect solution for ‘safe’ TNT.
A uniform structure could be the answer
That is where 3D printing comes in, to create a more uniform structure that replaces the relatively ramshackle approach of producing putty that we have right now. Each layer can have exactly the right number of voids to produce a perfect hotspot profile and the guesswork will simply be taken out of the equation.
The team is also looking at the materials themselves. TNT has been with us for more than a century and the delivery method has remained relatively unchanged for decades.
Now, 3D printing offers us the chance to reconstruct TNT and the scientists are determined to grab this chance to create safer explosives that could bring down a building when you want them to, and bounce off the floor when you don’t.