Ambient Armor – Drones and Autonomous Devices as Personal Shield-Bearers
The words “shield-bearer” bring to mind a knight’s page or squire – a young man or boy tasked with maintaining and carrying his master’s arms and armor when they’re not in use. But as time passed and the 14th century was drawing to a close, crossbows had come to fill the armories of Europe and the firearm had begun to find its way to the battlefield. Those days saw the rise of a new kind of shield – the pavise, a large body shield for archers and gunners to take cover behind as they prepared their weapon for its next shot – and a new kind of shield-bearer – the pavise-bearer, a man specially trained in moving the pavise and fixing it in place, in setting up shield walls, and generally in providing static and mobile cover for the archer or gunner fighting alongside him.
This was not an entirely new concept. There are reports as far back as the Iliad of similar tactics: Mighty shield-bearer Ajax the Great often provided mobile cover for his archer brother Teucer, and they fought as a team. But such tactics had never been systematized, on an army-wide basis, until the late 14th and 15th centuries in Europe and the development of the pavise.
The pavise was popular for a relatively long period – from the late 14th through the mid 16th centuries. Yet, over the course of the 16th century, it faded from use as its defensive utility diminished; advances in firearms technology gradually obviated the shield-bearer and his shield. Today, the integration of robotics and advanced materials may bring this ancient concept into the modern era, with robots serving as the shield-bearers of the future, for the principles of mobile defense and static cover clearly remain relevant.
There are two ways to accomplish this: One way is to employ very light autonomous systems, which may even be airborne, as a defensive screen. This is the so-called “ambient armor” concept. The second way is with heavily armored ground-based drones and autonomous robotic systems serving as breachers, forerunners, and mobile cover.
Ambient Armor
Light autonomous armor was first conceptualized in a 2016 MIT paper titled “Toward Ambient Armor: Can New Materials Change Longstanding Concepts of Projectile Protection?” The idea, in brief, is to mount very lightweight composite and fabric armor materials onto small drones or autonomous vehicles – and this includes quadcopter-style drones as well as ground-based systems. These small drones or autonomous vehicles would move around and in front of the people they’re tasked with guarding, placing themselves along the expected trajectories of incoming threats.
This, which the paper termed “ambient armor,” could be extraordinarily useful. Need to turn a dangerous corner? A drone with an aramid curtain will fly in front, to both conceal your presence and disrupt or destabilize incoming threats. Suspicious roadside debris? Small drones with UHMWPE-polyurea panels will screen it as you pass.
(Images from Materials design for robotic platforms enabling unique mechanisms of projectile protection, Liu et al., 2019)10.1016/j.jmrt.2021.09.010.)
A particularly interesting characteristic of these systems, and something that hasn’t been lost on the wise men who first conceptualized them, is that armor deformation simply doesn’t matter if the standoff between the armor and the projectile’s target is large enough. There’s no need to set backface deformation limits.
What’s equally interesting is that projectiles don’t need to be stopped cold. It may be that they don’t even need to be substantially slowed down. It may be enough to destabilize them or increase their drag coefficient. If bullets are directed away from their human targets, or so degraded in flight that they can’t possibly impact a human target 100 yards behind the drone’s armor screen, that would be sufficient.
What the above implies is that the number of potential ambient armor materials is much broader than the small palette of traditional armor materials used in shield construction. Aramid felt – a lightweight, very soft and fleece-like fabric – appears to be particularly effective as a large-standoff barrier material. Other options may be optically transparent, like foldable glass-polyurethane sheets, rigid polycarbonate sheets, metal meshes, or perforated metal plates.
On that note, even thin perforated metal sheets are known to almost completely destroy AP rounds. The below image is from “Defeat mechanisms provided by slotted add-on bainitic plates against small-calibre 7.62mm×51 AP projectiles” by Fras et al.:
When a 7.62x51mm AP bullet hits a thin (4mm) perforated sheet it is substantially destroyed and destabilized – even if it impacts directly over a slot in the plate, as in the above image, provided that slot is smaller in one dimension than the diameter of the bullet. Asymmetric forces are applied onto that bullet, separate its components, and ruin its trajectory. And that’s not even the worst-case scenario for the bullet: Those asymmetric forces will often fracture the core into pieces.
It’s pretty straightforward to imagine how similar concepts can be utilized in ambient armor. As most armor is concerned with stopping rather than destabilizing projectiles, this is a largely unexplored research opportunity. It could be that lightweight materials with knobs, pyramids, perforations, etc., are optimal for destabilizing projectiles in flight.
Here I’m reminded of an old patent for a “bullet destabilizing” invention that was called “ChaoTech,” which utilized extremely irregular ceramic geometries inside a textile armor pack.
It is unknown to what extent this invention worked in practice. Though, certainly, a more regular structure would provide more reliable protection. Chaos is not what you want in a ballistic material, and there is assuredly an optimal design that awaits discovery.
As things stand right now, aerial drones with aramid or UHMWPE felt curtains appear to be the most plausible route to near-future ambient armor, but there’s much more work to be done.
Heavy Armor on Wheels
The other way to make a personal shield-bearer is to improve upon current trolley-mounted heavy shields/barriers. Already, the heaviest ballistic shields have wheels and are pushed into conflict situations. It’s very simple to imagine, with off-the-shelf technologies and tools, that these wheeled barriers can function much as drones do, via simple handheld controls, or even autonomously.
We’ve demonstrated, with the Colossus Heavy, that it’s possible to make wearable plates that are capable of stopping .50 BMG AP projectiles at muzzle velocity. That sort of plate, while not terribly overweight at just over 9 pounds, is not very convenient to wear – but a tracked or wheeled bot could carry even heavier armor effortlessly. This sort of mobile pavise could be very useful in certain tactical situations. It would perfectly replicate the role of the old pavise-bearer, in providing for robust static barriers that can transform into mobile cover at a moment’s notice – and can clear entry-points and bottlenecks in advance of their users if circumstances demand it.
Before they were acquired by Textron 2019, Howe and Howe Technologies of Maine had developed armored “SWAT Bots” as an unmanned ballistic shield solution. The SWAT Bot was extremely large and heavy, and seems to have been deployed only a handful of times. It seems highly plausible, however, that similar technologies, likely streamlined and with a reduced noise and signature profile to facilitate their use indoors, will emerge over the next few years.
And just as the gunners of the 15th century moved behind pavise-bearers who were tasked with providing them with mobile cover, the warriors of the near future will fight behind robotic pavise-bearers who do much the same thing.
