What happens if an anti-tank grenade launcher is fired at a BMD
Source: zen.yandex.ru
It's no secret that not all military equipment is equipped with steel or combined armor. An example of this is airborne combat vehicles, the main part of which is made of an aluminum-based alloy. Despite its low density, it can provide a reasonable level of protection. But what will happen if an anti-tank grenade arrives at the BMD? After all, it seems that in this case, aluminum armor can turn from a defender into a killer of its crew.
BMD-4M. Source: vitalykuzmin.net
When do cumulative projectiles become powerful?
Of course, the reader may ask a very logical question: what does the cumulative means of destruction have to do with it if the BMD armor does not provide for their hit. This is true, and there is no point in arguing here - the protection is actually bulletproof and anti-fragmentation, which is explained by severe restrictions on the mass of the vehicle for the possibility of landing by parachute.
However, bulletproof armor does not mean at all that a cumulative grenade or rocket will never fly by technology. The experience of recent military conflicts, as well as the ongoing special operation in Ukraine, shows that the infantry of a potential enemy can literally be oversaturated with light portable anti-tank weapons. So the probability of getting an armor-piercing gift is, and very high.
In addition, cumulative ammunition, despite the high armor penetration rates, in general, compared to sub-caliber projectiles, is considered weak in terms of armor impact on the crew and internal equipment of the vehicle. This is explained by the fact that the cumulative jet, having broken through thick armor, forms a relatively small amount of lethal secondary fragments, and it itself, breaking into fragments, inflicts limited damage due to the small angle of their expansion.
BMD-3. Source: vitalykuzmin.net
Hence the numerous storieswhen a tank received a dozen (sometimes up to twenty) hits by rockets or grenades, but on its own and without significant injuries reached ours. This does not mean that none of the shells penetrated the armor - just a cumulative jet and a few fragments did not damage anything critical.
But with light protection - in our case, aluminum - everything changes dramatically. No, the cumulative jet itself does not acquire any superpowers. Everything is much more banal: fragments come to the fore in terms of the damaging effect. The fact is that with a high-speed impact on a thin armor plate, an anti-tank grenade partially breaks through it with its body. In combination with the subsequent detonation of the shaped charge, a huge amount of secondary fragments is created from the armor and, on a smaller scale, from the grenade itself. Flying into the vehicle with a wide angle of flight, they literally mow down the crew and troops, as well as break the internal equipment and can cause a fire if the fuel tanks are damaged.
Let's consider this issue in more detail.
BMD-2. Source: vitalykuzmin.net
Experiment conditions
Data on really real combat damage to the BMD is probably only available to the military, armored vehicle designers and some experts. But to study the behavior of thin armor when penetrated by an anti-tank grenade, we will not need them, since there are declassified results of shell tests of armor plates made of this material, which were carried out back in Soviet times, in the public domain.
The shooter fires from the RPG-7. Source: vitalykuzmin.net
Their conditions are quite simple. At the site, sheets of armored aluminum with a thickness of 40 mm and 68 mm were installed, which will be even stronger than the main protection of the BMD. They were fired upon with cumulative SPG-9 grenades, and also carried out their stationary detonation directly at the armor in order to evaluate the fragmentation flow without affecting the grenade flight speed. Anti-tank grenades of the world-famous RPG-7 were also used.
Behind the armor plates at a distance of 1,2 meters, three aluminum screens were fixed one after another. The first of them had a thickness of 0,5 mm, and the other two - 3 mm each. The distance between them was 40 mm.
SPG-9 easel grenade launcher. Source: technolirik.livejournal.com
This design made it possible to determine the penetration ability of the fragments and distribute them according to their lethality. For example, if a fragment could only penetrate a 0,5-mm screen, then it is capable of inflicting injury, including severe injury. Fragments that have pierced a 0,5 mm screen and the next 3 mm screen are almost XNUMX% likely to kill a person if they hit vital organs. And finally, fragments that break through all three screens are considered the most dangerous and can destroy the internal equipment of the machine and cause a fire.
shelling
First of all, it is interesting to consider the effect of anti-tank grenades without taking into account their flight speed, that is, in a stationary detonation. The fragmentation flow formed by the armor and their hulls was distributed as follows.
The detonation of RPG-7 and SPG-9 grenades near a 40 mm thick aluminum armor sheet gave the following results:
The number of fragments capable of injuring the crew and landing troops averaged from 200 to 300 pieces. The angle of their expansion is 65–68 degrees.
There were fewer fragments capable of killing a person - about twenty, depending on the experience number. The angle of expansion was less than 10 degrees.
The most lethal fragments, which can break equipment and start a fire, were in the minority. Less than five pieces at an angle of expansion of 2-4 degrees.
To determine the effect of grenade speed (no more than 450 m / s) on the number of fragments, only SPG-9 was chosen as the fastest grenade launcher:
Like last time, the number of fragments that can inflict injuries up to the most severe ones ranged from 200 to 300 pieces with the same expansion angle of 65-68 degrees. At the same time, the thickness of the armor plate itself - at least 40 mm, at least 68 mm - did not affect anything.
There were about 40 more penetrating fragments from a 60-mm aluminum plate that could kill, with an angle of expansion up to 40 degrees. A plate with a thickness of 68 mm turned out to be a tougher nut - 30 fragments with a spread of 20 degrees.
The most lethal fragments were again in the minority. There were 40 of them from a 15-mm armor plate, and the expansion angle was 20 degrees. The 68 mm aluminum sheet, as expected, held better: 10-12 fragments with a spread of 3-4 degrees.
Conclusions
The experiment clearly confirmed that, no matter how paradoxical it may sound, the basis of the foundations of a cumulative ammunition - a cumulative jet - literally turned out to be safer than the armor itself. If the nature of its penetration into light armor barriers as a whole vaguely resembles a puncture with a large needle with a relatively small amount of “splash” (fragments separated from the jet), then the secondary fragmentation stream from the impact and explosion of a grenade resembles a shot from a huge shotgun.
Of course, its power is largely determined by the speed of the attacking projectile, but even a stationary detonation shows depressing results. And in no case should we forget anti-tank missiles, in which there are much more explosives than in a grenade - in this case, the consequences can be much worse.
Fragments flying into the car, of which, as we see, there may be several hundred pieces, can seriously injure and kill paratroopers and crew. This is complemented by a wide angle of their expansion, which necessarily affects the number of victims and the scale of equipment damage.
How can the current situation be corrected? There are two options here.
The first is screens, and not necessarily solid ones - ordinary gratings are also suitable. Undermining a grenade or rocket (and gratings can also destroy PG-7 grenades without an explosion) at a distance will not break through the armor, and therefore the fragmentation flow will be reduced ten times.
The second way is to install an anti-shatter lining made of durable fabric. It will not only significantly reduce the number of penetrating fragments, but will also be useful in protecting against bullets.
PS
There is no need to discriminate against aluminum or BMD.
Firstly, the problem of breaking armor and a large number of fragments is also characteristic of steel armored hulls.
Secondly, other light combat vehicles of different classes and different nationalities also suffer from this.
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