19 July 2024

The M1 Thumper

Recent images have surfaced online, showcasing the M1 “Thumper” prototype, a unique variant of the legendary M1 Abrams tank equipped with a 140mm main gun and an autoloader. Developed in the late 1980s, the “Thumper” was designed to significantly enhance the firepower and penetration capabilities of the existing M1 Abrams, which typically features a 120mm gun.

The M1 “Thumper” stands out with its enlarged turret designed to accommodate the formidable 140mm gun. This development aimed to provide the tank with superior firepower, making it more effective against heavily armored adversaries. The prototype underwent a series of rigorous testing and evaluations to assess its performance and viability on the battlefield.

Despite the promising advancements in firepower, the “Thumper” project was ultimately shelved. The decision to not proceed with production was influenced by several factors, primarily the high cost associated with developing and deploying a new tank variant with a larger gun. Furthermore, advancements in ammunition technology for the 120mm gun used by the standard M1 Abrams helped maintain its battlefield effectiveness, reducing the immediate need for an upgrade to a 140mm gun.

In comparison, a similar project was undertaken by Germany for the Leopard 2 tank. This involved the integration of a 140mm gun autoloader system, where the main gun was positioned on the left side of the turret, with ammunition stored in the turret bustle. However, like the “Thumper,” this project was also discontinued at the end of the Cold War and never reached the battlefield.

From here. Wikipedia also discusses it:

M1 Thumper (also known as ATAC Demonstration System) was a single M1A1 fitted with a heavily modified turret to trial the experimental XM291 ATAC (sometimes referred to as LW120) smoothbore gun, a more powerful replacement for the M256 capable of firing either single-piece 120 mm or two-piece 140 mm ammunition with only a barrel change. The 140 mm rounds were too large (boasting twice the chamber volume of a M829 APFSDS and twice the muzzle energy) and heavy to be moved around by a human loader, mandating the installation of a XM91 mechanical cassette autoloader. The Thumper underwent testing in 1988 and in the 1990s at Aberdeen Proving Ground, where it demonstrated accuracy equal to an M1A1's but with significantly higher armor penetration capability.

This concept was a bad idea 35 years ago and would be an even worse idea today, informed by the experience of tank warfare since then.

For example, in the 1991 Gulf War, M2 Bradley Infantry Fighting Vehicles, with two TOW anti-tank missiles and a much smaller 25mm chain gun destroyed more enemy tanks than the M1 Abrams main battle tank and only about 25% of enemy tanks were destroyed with other tanks. More than 3,000 Iraqi tanks were destroyed or captured in that short and one-sided war.

Similarly, in Ukraine, very few tanks have been destroyed by other tanks (less than 5% of destroyed tanks) and tanks have otherwise proved to be a low demand resource. See here and here

Tank casualty rates in Ukraine, one of the largest conventional wars between near peers in post-WWII history, have been extreme. Initially, Ukraine started without about 900 operational tanks (see also here) and Russia started with about 2,600 operational tanks devotes to the mission (see also here), although both sides have reactivated mothballed tanks and Ukraine has received tanks provided to it by its allies.

Oryx, a third-party non-profit (which admittedly undercounts losses by considering only photographically documented losses) has identified 866 tanks lost by Ukraine (96% of its original active tank fleet) and 3242 tanks lost by Russia (125% of its original tank fleet for the mission and 90% including at least another 1,000 tanks that it brought of out reserves and storage), since February of 2022 when the current phase of the Ukraine war began. Tanks losses by both sides have included the most modern state of the art tanks available to each side, including at least 10 out of 31 M1A1 Abrams tanks provided to it in August or September of 2023 and the most advanced T-90 tanks in Russia's arsenal. Russia pulled its small number of T-14 Armata tanks from the conflict after a brief deployment limited to secure positions (see also here).

The M1 Abrams tank has problems. An insufficiently large tank shell is not one of them (Russia uses slightly larger 125mm shells but has had more problems with the combined systems due to barrel repair issues or poor choices about where their ammunition is stored). And, the greater weight and/or lower number of shells that could be carried at once, would have made the other problems with the M1 Abrams (such as its excessive size and weight which makes it hard to deploy many of them quickly or to deploy in tight mountain passes or urban areas), which have become apparent now, even worse.

8 comments:

neo said...

And, the greater weight and/or lower number of shells that could be carried at once, would have made the other problems with the M1 Abrams (such as its excessive size and weight which makes it hard to deploy many of them quickly or to deploy in tight mountain passes or urban areas), which have become apparent now, even worse.

Panther KF51 has a new turret mounting an autoloaded 130 mm calibre main gun

andrew said...

Thanks for the heads up.

Notably, even so, it is only 59 tons. https://en.wikipedia.org/wiki/Panther_KF51 Some of the details are sketchy, but it still seems like an obsolete at inception war machine.

neo said...

why's still seems like an obsolete at inception war machine?

what do you want in a near future tank ?

andrew said...

@neo

Tracked, heavily armored military vehicles with a single main gun firing a large unguided shell, and minimal secondary weapons (i.e. tanks) are obsolete.

Direct fire weapons have a maximum range of 2000-2500 meters. Anti-tank missiles, suicide drones, aircraft delivered boms, and artillery have a significantly longer range than that are all capable of destroying or critically disabling at tank at longer ranges. The rate at which tanks are destroyed in modern warfare is on the order of 90%+ There is no tank in existence, including this one, which can survive a direct hit from an anti-tank missile (which is often one shot, one kill), or an artillery shell. Tanks are also vulnerable to land mines, IEDs, pits, large steel or stone barriers, and a variety of other defenses. Tanks rarely have advanced active defenses, and even when they do (see, e.g., Israel) those can often be overcome by something as simple as firing two anti-tank missiles at it at the same time. Tanks generally don't have anti-aircraft defenses.

The large main gun of a tank like the 105mm-130mm main guns used in most tanks are primarily intended to be used against other tanks. But only a tiny percentage of all enemy tanks of destroyed in that way.

Main battle tanks are heavy and slow. They can't evade enemy fire as fast as enemies can close on them. They slow down the units that they are with. They are insanely fuel guzzling (about 0.5 mpg), which creates a long logistics train of vulnerable fuel tanker trucks which is a huge problem in modern warfare which has no front lines. They can't go to tight urban streets or mountain passes or narrow jungle/forest roads which are common in much of the world. They are too heavy to cross many bridges. They are too heavy to deploy more than one at a time by airlift and only with larger military transport planes which are scarce. They take weeks to deploy by sea and many days to deploy by rail (during which transport, they are highly vulnerable). Their performance in mud is overrated. The superiority of tracks over wheels as of 2024 is overrated and the reality is that even tanks operate the vast majority of the time on roads.

Some sort of armored vehicle makes sense against forces without anti-tank weapons or other heavy vehicles like infantry with small arms, but even then, tanks aren't very effective without dismounted infantry support.

A much lighter, missile carrying, wheeled, more fuel efficient vehicle with enough armor with deal with small arms fire and shrapnel, but not so much as to make a futile attempt to stop anti-tank missiles and artillery shells would be a better choice than a tank. Active defenses are to be preferred strongly to heavier armor.

The M10 Booker has tried to make a case that its main 105mm gun should be used by infantry against moderately strong bunkers and armored vehicles without anti-tank weapons (like armored personnel carriers) but the case for it is not very convincing as I've detailed in prior posts on the subject.

andrew said...

N.B. The U.S. Marine Corps has entirely removed tanks (and self-propelled howitzers) from its arsenal for these reasons. This isn't just crazy liberal me putting forward an entirely speculative idea that no one has taken seriously.

andrew said...

One of the last times a U.S. tank destroyed an enemy tank in battle was in the Battle of 73 Easting on February 26, 1991. https://en.wikipedia.org/wiki/Battle_of_73_Easting

neo said...

israel used tanks in Gaza

andrew said...

If all you have are hammers, all problems look like nails.

And, there is no indication that tanks were terribly important militarily in Gaza. Main guns weren't used at all.

But, Gaza does, at least, present a situation where the main vulnerabilities of tanks are not present, because the opposing force lacked anti-tank weapons.