Active leg protection against mine explosions is a useful Israeli invention for military equipment.
There's nothing wrong with the title of this article, and it's not a wild flight of fancy. The Israeli company Plasan has indeed developed active leg protection for armored vehicles against mine explosions. Naturally, we're not talking about the "legs" of the combat vehicle, but the legs of the people inside it. And this thing, it must be said, could be quite useful.
The legs also suffer
Mines and improvised explosive devices, when used against armored vehicles, are quite treacherous. They are treacherous because even if the explosion doesn't completely destroy the vehicle or render it inoperable, the occupants (troops and crew) can suffer such severe injuries that further combat is impossible.
The point is that the energy of the explosion imparts powerful vertical acceleration to the hull, which is transmitted to those inside. Therefore, even if the bottom isn't penetrated, the soldiers won't benefit. The most severe injuries observed in such situations are compression fractures of the spine and pelvis, which can render a person permanently disabled.
Typically, to prevent such situations, energy-absorbing seats are used that are not rigidly connected to the vehicle's underbody. They are often designed with suspension mounts and/or damping devices, which prevent the transmission of shock from the floor (underbody) deforming under the blast.
However, the spine and pelvis aren't the only parts of the human body that suffer from mine explosions. Feet on the floor, especially if they're bent at about 90 degrees at the knees, also experience powerful vertical acceleration. Sometimes, the legs literally fly up to ear level—we'll see this later using the mannequins.
The result: broken tibias, ankles, and feet, and joints are destroyed. All these injuries render a person completely incapacitated and require a long period of treatment and recovery. Sometimes these injuries even lead to amputations—for example, someone didn't step on a "Lepestok," but simply rode in an armored personnel carrier or infantry fighting vehicle, and as a result, part of a leg is missing.
It is possible to avoid injuries, but not always
In fact, the problem of leg injuries from mine explosions isn't insurmountable in principle. An example is the V-shaped underbody, which diverts most of the blast energy and maintains its integrity without penetrating into the crew compartments—MRAPs and some other armored vehicles carry them, and their occupants know no harm.
A double bottom or a "floating" floor, separated from the bottom by shock-absorbing dampers, can also be used. However, these solutions are not suitable for everyone and not always: a V-shaped bottom cannot be bolted onto an existing combat vehicle, and a double bottom, again when incorporated into existing designs, will significantly reduce the height of the crew compartments.
Mine-resistant underbody pads installed remotely from the vehicle's underbody are also not always feasible. They increase the vehicle's weight and simultaneously reduce its ground clearance—meaning they negatively impact the vehicle's maneuverability and maneuverability on both sides.
So there's no easy way out of this situation. But the Israelis seem to have found at least the path of least resistance by introducing active leg protection for combat vehicles. It's called LAPS, or Leg Active Protection System.
Let's be clear: it's unlikely to be suitable for crews, as they work in confined spaces, and a LAPS is more likely to break their legs than save them. But for paratroopers in infantry fighting vehicles and armored personnel carriers, it's perfectly suitable.
Leg Active Protection System
Naturally, Plasan isn't sharing any detailed information about its development—and that's not surprising. After all, it's a system directly related to improving the survivability of personnel in combat vehicles, and such features aren't usually detailed in marketing brochures.
Nevertheless, some details about LAPS are still known, and they are quite sufficient to understand the general logic and operating principle of the complex.
Simply put, LAPS works by raising a person's legs off the floor as quickly as possible at the very moment the vehicle hits a mine or improvised explosive device. In other words, the system should literally yank the legs out of the zone through which destructive vertical acceleration is transmitted to the body.
To this end, the LAPS is equipped with sensors, most likely mounted on the vehicle's underbody. These sensors are tasked with recognizing the detonation of a mine or improvised explosive device within milliseconds and issuing a command to activate the system. Reaction speed, it should be noted, is a key parameter here.
The results of a mine detonation involving dummies (and a drawn illustration) with and without LAPS active leg protection. The legs, as you can see, are blown apart quite violently without the protection—the energy of the explosion makes itself felt. Image by Plasan
According to the developers, explosion detection occurs even before its energy begins to deform the underbody. The system also includes a built-in filter that filters out false sensor signals from impacts and other normal loads when driving over rough terrain, etc.
When an explosion is detected, the system sends a signal to the actuators of the seat occupied by the vehicle's occupant. It is reportedly not much different in appearance from a standard energy-absorbing seat, only slightly deeper. Apparently, this is done to position the seat edge closer to the occupant's knee.
When the mechanisms are activated, the seat literally lifts the fighter's legs upward, lifting them off the floor to a safe height a split second before impact, which is transmitted to the undercarriage by the blast wave. Essentially, it's analogous to a car airbag, except instead of the impact being cushioned by the deployed airbag in a split second, the body (legs) are removed from the impact zone during the same time.
Moreover, the active protection system, as rumor has it, will be controlled by an onboard computer with a neural network. This is all to minimize the likelihood of false triggering and ensure the required response speed. After all, a delay means injured soldiers, and a false activation of the mechanisms means chaos in the troop compartment.
Conclusions
The Plasan idea is quite interesting, especially considering that not every vehicle, even one under development, can accommodate a V-shaped underbody or a double floor. So, in the long run, if active leg protection is put into mass production, many soldiers will be saved from leg injuries, lengthy rehabilitation, and disability.
But LAPS will require a significant investment. And this applies not only to onboard computing systems with a high-speed processor and AI—scales will have to be built into the seats, which, after weighing the soldier, will automatically adjust the force of their leg lift. Standardization is impossible here, since one soldier might weigh 60 kilograms, and another 90-100 kilograms. The mechanism simply won't be able to lift one soldier's legs, while launching another into space—an exaggeration, of course.
But then again, this is Israel. Considering how they treat the lives of their soldiers, they won't spare any expense.
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