Firearms future tech: First smart bombs, now smart bullets

Sandia National Laboratory has developed a laser-guided ‘bullet’ which really isn’t a bullet, for reasons explained below

Several TV shows and movies have featured bullets — usually deployed by the bad guys — that fly around corners and look for one person or object in particular. We don’t have those yet, but a new projectile developed for snipers at Sandia National Laboratory could be a game-changer for taking out distant targets.

This projectile — it really isn’t a bullet, for reasons explained below — is about four inches long and is contained within a protective sabot (shell) when loaded into the rifle. Without the sabot, the projectile looks like a miniature missile and is technically a “fletchette.” The sabot guards the fins on the projectile prior to firing, and provides a seal against the walls of the gun barrel to get the most out of the powder charge that propels it.

When the projectile leaves the barrel, the sabot falls off.

Going Downrange
Once in flight, a sensor in the nose of the projectile looks for a laser designator in the same way a smart bomb dropped from an airplane does. Neither the bomb nor the sniper projectile is self-propelled, instead using gravity and momentum to find its way to its target. The laser sensor adjusts the fins on the fletchette up to 30 times each second to correct the course to the target.

As long as the projectile can “see” the laser-illuminated target and it’s moving in the same general direction, it can impact with far greater accuracy than most human snipers could manage.

The new projectile isn’t really a bullet, and it won’t be fired from a conventional rifle. Bullets are spun as they travel down the barrel of the firearm that launches them, so they’re spinning many times each second while in flight. This spin stabilizes the flight path of the bullet, making it more resistant to wind and changes in air density that would drag a non-spinning bullet off course.

Spinning a projectile with aerodynamic fins wouldn’t accomplish anything and would confuse the projectile’s on board systems, so the barrels of these rifles are more like smooth-bore cannons.

Sandia attached an LED to one projectile to make it act like a tracer and reveal its flight path. The time-lapse photo above clearly shows the projectile changing course in flight, behaving very differently than a conventional bullet would. The video below offers another look.

Long-range snipers have to have more than just a sharp eye and a steady hand. As targets get farther away, bullets are in the air longer and forces have more opportunity to make them stray from their intended path. The sniper has to take into account the density of the air, wind direction and speed (which may be different at the target’s location), any change in elevation between his rifle and the target, and the refractive error of his scope at that distance.

Just the effect of gravity on the bullet is significant. While bullets are often described as being “in flight” while on their way to their targets, there’s really no flying involved. As soon as the bullet leaves the gun barrel, gravity will begin pulling it earthward, accelerating it in that direction at a rate of 32-feet-persecond-squared.

Counterintuitive as it seems, if you were to fire a bullet across a very flat landscape with no obstructions, and at the same time drop another bullet from the same height as the gun muzzle, they would both strike the earth at the same time (with possibly a slight error to account for the curvature of the earth), as they’re both being pulled down by the same force of gravity. While gravity is working in that direction, the bullet is decelerating along the vector it was given when it was expelled from the gun barrel, since its only source of propulsion stopped at that instant.

Factor in the air density and wind issues described previously, both of which will affect the bullet in some way, and you get a sense of how complicated this can get.

Sandia is looking for a manufacturing partner to produce the new projectile, and I doubt these things are going to be cheap. Their press release describes potential customers as “the military, law enforcement, and recreational shooters,” but frankly, I hope these aren’t sold privately. I’m no gun-grabber, but I have difficulty imagining any lawful private use for these. 

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