This story is adapted from Into the Waves: My Quest to Uncover the Mystery of a Civil War Submarineby Rachel Lance.
The war in Ukraine is new. The injury patterns in this war are anything but. Since the invention of the world’s first high explosive in 1867, TNT, people have regularly inflicted the same patterns of blast trauma on themselves. Sometimes it seems like we even do it eagerly. Every few decades we invent a new vehicle to amplify the mayhem, such as cluster bombs or thermobaric bombs, but the basic physics of explosion and the vulnerable anatomies of our softest body parts have not changed.
At the start of any new war, false claims of blast trauma start flying as fast as shrapnel. A month into this one, we already have leading public figures making inaccurate statements about how thermobarics “suck” the air out of your lungs. (They don’t, but more on that below.) Regardless of the level and prevalence of the many misunderstandings about explosions, one thing is undeniably, eternally true: People near explosions can die. Here’s how it really works.
From a medical perspective, blast injuries are neatly categorized into one of four orderly bins that are numbered: primary, secondary, tertiary, and quaternary. A blast victim may receive only one type, or may receive a trauma bag containing any painful mixture of the four. Quaternary trauma is sort of the “other” bunch of things that can, but don’t always, occur as a result of an explosion, such as burns, chemical agents, or radiation exposure. Tertiary trauma is the type of injury most people expect – think of an action hero who hurts his back after being carried across the room. It should be noted that tertiary trauma almost never occurs in the real world. Secondary injuries are unfortunately an extremely common type of injury. They are the result of objects, such as shrapnel or even fragments of the bomb casing, being thrown and striking a person due to the explosion. Secondary injuries are dark and visually gruesome as they often take the form of extremity trauma, cuts deep enough to reach the skeleton, and amputations.
These three types of injury—secondary, tertiary, and quaternary—make obvious sense as expected possibilities. Primary blast injuries, on the other hand, are an impressive, sometimes invisible, terrifying accident of nature. They are a byproduct of the strange physics of explosions mixed with human frailty. Primary injuries result solely from the pressure caused by an explosion, usually due to a shock wave.
To understand how a shock wave maims, it is first crucial to understand how a shock wave is born. Usually sound moves like billiard balls on a massive smooth felt table. First, a noisy event occurs, such as an impact. A gas molecule in the immediate vicinity of the action repels: This is the cue that hits the cue ball. The cue ball moves outward until it hits the 4-ball, another gas molecule. Kunk. They hit each other, and the cue ball transfers some of its energy to 4. Now both balls move, slightly more slowly and in an outward direction, until they hit other balls, hitting their next nearest neighbors. The overall wave front of the motion moves forward, but each individual ball moves only slightly across the table. The motion is transmitted outward, expanding and slowing a little with each collision as the leading edge of the motion passes through the table.
