Perhaps like you, I saw some very unsettling footage on the news this evening–footage showing an M1A2 Abrahms battle tank just moments after an RPG slammed into it, lightly wounding two of the men inside and killing one, I believe.
My guess is that the explosive charge on an RPG is significantly larger than that of a hand grenade, but how much?
Also: about how fast does the RPG’s rocket propel the grenade? Are we talking several hundred MPHs?
And what accounts for an RPG’s penetrating ability? I’m guessing it’s more than a simple F=M x A, including such factors as the density and shape of the RPG’s nose.
Frankly, I’m stunned that an RPG could penetrate the armor of our best battle tank…
I am no expert in the field, but I know a thing or two.
An RPG, as opposed to a hand grenade, is not only much more potent, but also concentrates its whole explosive power on the point of impact.
A hand grenade creates something like a spherical explosion instead.
I haven’t seen the footage (a link maybe?) but it is very dificult to seriously damage a M1 tank (which has reactive armour) with an RPG. There is one occasion(some test probably), where a M1 sustained two succesful hits from sovied-designed Israeli tanks and then striked back, incapacitating both enemy tanks.
I d’like to add that the attackers most probably got a lucky shot. Some places (like between the turret and the main body of the tank) are quite vulnerable.
As pointed out, the M1 does not carry reactive armor (an armor that explodes outwards when struck.) M1s carry composite armor made of steel and ceramics and God only knows what else.
You’re right though in that RPGs are designed to focus their explosive power. To be honest the term “RPG” is deceptive. An RPG is not like a grenade launcher that throws little grenades. It’s really closer in design and purpose to a rocket launcher. It’s similar in capability to the M72.
The RPG-7 grenade (the RPGs you see used are very likely RPG-7s) is an 85mm projectile that weighs about five pounds, which is much heavier than any hand throwns grenade.
Sorry for the short first post: I was going out for beer.
Since three troops were involved it sounds like a turret hit. If the loader and commander were up in their hatches an RPG is going to spoil their day. And the gunner won’t especially like having 4 or 5 pounds of explosive going off against the wall of his cubicle. As Dog80 pointed out it may have been a lucky trap shot shot against the turret ring.
Actually, your guess is right in the ballpark. A couple hundred miles an hour flight speed with maybe 3 or 4 seconds flight time.
The shape of the RPG’s nose, or any shaped charge weapon, is only an accommodation to aerodynamics. The work is done by the inverted cone shaped explosive charge right behind that thin shield. It’s hard to believe, when you see the diagrams, that shaped charges really work. But they do. RPGs can go through 18" - 24" of steel in the right conditions.
Here’s a link that explains shaped charges in a little more detail. They’ve been widely used in man-portable anti-tank projectiles since WWII, though the principle, originally known as the “Munro Effect” was first observed in the late 1800s. Here’s some more info on the RPG-7, which is pretty much the standard model, though the Russians are now producing and selling more advanced ones (including, I believe, models with multi-stage shaped charges). Note from the first diagram that much of the large, pointy warhead is, in fact, hollow.
I expect that recent damaging hits to M1s by RPG rounds are a function of the unusually close quarters environment in which the tanks have been coming under attack in the original invasion of Iraq and more recently. If an attacker is willing and able to close to point-blank range, he has a better chance of hitting his target in one of its more vulnerable areas (e.g., the turret ring, the lower side hull behind the treads, hatches, etc.). This is in contrast with their designed role, and most of their active employment in the ‘91 Gulf War. Note that range has no inherent effect on the penetration capability of a shaped charge. It pierces the same thickness of armor whether fired from 1000’ feet away or 1 foot. RickJay - I believe the M1A2 actually has a layer of depleted uranium in its composite armor on some surfaces, along with the other materials you mentioned.
Here is what an RPG-7 looks like.
This is not the first time an RPG has done damage to a tank. Back in Aug of last year a tank was put out of action by an RPG round. Here is a series of excellent pictures of the 8/03 tank
Don’t forget that the armor on a tank is not the same thickness all over. some areas are thinner than others.
There have also been rumors of RPGs with hyperbaric warheads being tested in the perpetual border slirmishes between China & Russia.
If true, the RPG has just become one of the most dangerous infantry support weapons on the battlefield, as it could be turned on infantry with great ease, & could destroy Chobham-type armor as well.
That link may need a little more explanation for some. As stated by others, the front cone of an RPG is hollow. In fact, there is another hollow cone on the inside, but the bottom of this cone is facing forwards. The first hollow cone does 2 things, it provides a more aerodynamic profile and it provides a standoff distance for the start of the explosion.
The second hollow cone (which is bottom forward) is lined on the inside with a thin sheet of metal (used to be copper, not sure if that’s all that’s used) and the outside of the cone is the explosive.
When the front cone hits the target, it detonates the explosive at the very tip of the back hollow cone. This melts the metal lining, and blows it back down the center of the second hollow cone towards the target. As the explosion propagates down the cone (towards the target), it continues to add molten metal to the jet, and the explosive force continues to accelerate the molten metal. The metal then hitsthe target like a thin molten spear at the speed of sound. It doesn’t make a large diameter hole, but it makes it through a lot of armor.
Defenses against the RPG include forcing it to detonate early so the molten jet breaks up before it hits the armor, and turning the RPG so that it is not facing directly into the armor.
Okay, I think we’re all familiar to the concept of a rocket launcher thanks to FPS games going all the way back to Doom. Are there real differences between what those games describe as a rocket launcher, what a real rocket launcher is, and what an RPG is? How about a bazooka?
A small launcher like an RPG-7, M72, or Carl Gustav is basically a rocket-assisted shell; it has a rocket-type engine that fires it at the beginning of its flight, but it’s flying most of the way unpowered. They’re unguided and for obvious reasons, accurate range is limited. A bazooka is such a weapon (the M72 is today’s bazooka.)
This is as opposed to a true rocket launcher like a TOW, Stinger, or Dragon, which are actual missiles, with rocket engines propelling them all the way to the target.
Nice post, BoringDad, with a chance for me to clear up a common misconception.
I have often heard of shaped charges “burning” or “melting” their way through metal. Neither term is correct.
The metal isn’t burned, or oxidized, by the passage of the shaped charge jet. There’s little or no oxygen to be had 'cause an explosion just went off in the immediate neighborhood. This effect can be useful in putting out oil-rig fires.
And it’s not melted either. The temperatures associated with the jet’s passage are typically well below melt temperatures of the metal, usually steel, being penetrated.
What the jet does do is push its way through. Yield strength of steel is on the order of 40K psi, more or less. Local pressures from shaped charge jets are in the 10+ million psi range. Rather than think of a hot knife through warm butter, as an analogy, think of a screwdriver through styrofoam.
Interestingly, some of the metal from the jet is deposited on the penetrated metal’s surface. So what you get is a very loud, expensive copper plating technology.
I guess you’ve gotten the answer now that the RPG penetrating ability comes from a shaped charge.
The term “grenade” applies to any small missile. Grenades can be thrown by hand, propelled by a rifle (rifle grenade), rocket etc. The hand thrown grenades usually thought of are fragmentation. However, there are also concussion grenades, smoke grenades, tear gas grenades and probably some more I haven’t thought of.
If I can be an incredibly nitpicky metallurgist for a second - the cavity liner doesn’t melt, and the jet isn’t molten. This has been determined by flash x-ray diffraction. The jet is structurally a solid, but it flows under the immense pressures generated by the explosive.
Sidenote, America no longer uses the M72; Do you guys? We use the M136 now, and the troops are clamouring for the Carl G. (which the SF and Rangers already have).
Just to be be incredibly nitpicky: The Carl Gustav is not technically a rocket launcher, it’s a recoilless rifle. The round contains a propellant charge much like a conventional artillery round, except that the bottom blows out to allow gases to escape to the rear of the weapon. But it’s not a rocket - the casing stays in the weapon, and it’s the launcher that handles the pressure of the propellant charge going off. Only the shell leaves the muzzle, a good part of the propellant gases leave through the vent at the rear of a weapon, and the shell casing has to be removed from the weapon before reloading.
The M72 (and the bazooka) OTOH are both rocket launchers, in that they - ehm - launch a rocket. If you inspect a bazooka round or a M-72 round, they are little solid-fuel rockets in their own right - with a rocket bell, fins and everything. The tubes of the bazooka and M72 are much lighter than those of the Carl Gustav in that they do not handle any pressure - except what’s necessary to protect the user from the exhaust gases.
(And so to make the confusion complete: Both the Carl Gustav (and the RPG) can fire rocket-assisted rounds - well after the round has left the launcher, a sustainer rocket engine kicks in to improve range. Range is nice. Computing for windage with a rocket-assisted round - preferably before the target decides to solve the problem by running you over instead - not so nice.)
So technical specifications aside… How effective are RPGs ?
I was made to understand that only those cumbersome Marine Amphibious APCs were vunerable to RPGs. That most other armor in the US arsenal was RPG proof. (Though of course having them slam into your tank isn’t fun at all of course.)
Is it any good vs infantry ? HUMVEEs must be a favorite with Iraqi Insurgents.
Is it more pshycological seeing those grenades flying all over the place ?