Next-gen smoke grenade hides soldiers from enemy eyes — and thermal sensors, too

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If you’re a civilian, smoke bombs are something you might associate with fun hijinks on the Fourth of July. If you’re in the military, however, a smoke bomb may just save your life by providing you with a dense cloud of smoke cover when you need it the most. The only problem? While smoke bombs may cover you by reducing visibility, smart sensors are increasingly able to look beyond what is visible to the human eye by analyzing the infrared (aka thermal) region of the spectrum.

That’s where U.S. Army researchers may have just changed the game. Presented at the 255th National Meeting & Exposition of the American Chemical Society (ACS), they describe the creation of a totally new kind of smoke that can foil both the human eye and infrared detection.

“Because of the advancement of sensors beyond the visible region, we need new, high-performing obscurants in the infrared region,” lead researcher Zach Zander of the U.S. Army’s Edgewood Chemical Biological Center, said in a statement. “Each obscurant can absorb or scatter light at a given frequency. Most of the smokes that we use do well in either the visible or IR range. The objective of this program is to create what we call a bispectral obscurant, which works to block visible, as well as infrared, detection.”

Traditional army smoke grenades are made using a toxic material called hexachloroethane. The new smoke, on the other hand, is made of a type of terephthalic acid, a known visible obscurant, along with a metal organic molecule called UiO-66 that is able to absorb frequencies in the infrared range.

In a proof of concept demonstration, the new type of smoke grenade was exploded in a 249-cubic-yard chamber lined with sensors. It was then closely monitored at both visible and infrared wavelengths. While the results were impressive at showcasing its resistance to both visible light and infrared sensors, team members think they will be able to further improve the overall effectiveness by changing the recipe of the pyrotechnic portion of the grenade.

In the long term, the researchers hope to create a “Swiss army knife” of smoke grenades in which it’s possible to use a single grenade to block out a wide spectrum of different wavelengths. This would be especially useful in a military setting where it is crucial to be able to minimize the amount of equipment each soldier has to carry.