Tag Archives: design

A Cruiser By Any Other Name

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I’ve discussed before that the Arleigh Burke-class is the best destroyer afloat today. It’s got a good radar, plenty of missile capacity, and comes at a pretty reasonable price due to its large production run. Competitors like the Daring class cost entirely too much and deliver entirely too little. Let’s look at a a follow on. Nothing lasts forever, and something newer, with newer systems, will be fun to sketch. This will be my version of something like the Zumwalt class. Though, because I prefer things evolutionary, it will be rather less ambitious. Admiral Zumwalt would have wanted it that way, anyway.

We’re not going to compete directly with the Burkes in terms of size, because that makes it really hard to justify the changes. And we’ve already sketched smaller. In case the title didn’t give the game up, we’re going bigger.

As always, we must first define our mission. Being a large cruiser, we’d like it to focus on air defense and air control, with plenty of land attack capability (i.e. plenty of missile tubes). We’d also like reasonable antiship capability and some antisubmarine capability, though this last is negotiable. I’ll pencil in some nice, off-the-shelf sonar systems now, with the understanding that designers can make adjustments as needed for cost reasons there.

On to the sketch! First thing to do is to forget about the stealth nonsense baked into the DDG-1000 design. Some low-observability features are a good thing, but the excessive stealth optimization of the Zumwalts with their special superstructure and ridiculous tumblehome hull is silly. A more normal hull design, bow raked forward, has far better seakeeping, and that’s much more important. Not only is it a patently obvious ship if one bothers to look out their windows, but we’d expect it to be able to handle Air Defense and Air Control, which means the radars have to be on, which means it will be pumping out electrons like the Las Vegas strip. And if we don’t turn on the radars, what exactly is protecting the carriers? Accepting that not every new design has to be a ghost’s shadow will help keep costs down. We need to limit the use of new technologies in new designs so the costs don’t explode. Nobody bats 1,000 with new designs. Some will fail, and we need to be resilient about this. Also, a more conservative design means we’ll be able to reuse some things from existing designs. Or, test out some new stuff elsewhere. Like we used to.

There you have it. Some gentle angles, avoid corner reflectors, keep the nice clipper bow. As a side effect, that’s a lot prettier.

Next: radars. I really like the original, un-neutered suite planned for the Zumwalts, namely the SPY-3 and the SPY-4. The SPY-3 is an X-band AESA radar, optimized for best tracking accuracy. The SPY-4, deleted from the DDG-1000s to save costs and still fitted on the Ford-class Carriers, is an S-band AESA radar optimized for high volume search. This split of functionality mirrors what NATO testing found to be best in the late 90s. These were integrated into a dual-band array system, which is some pretty revolutionary stuff. I’m fine with that as one of the key new technologies embarked, though the emitters could also be separated. The overall concept is right though. And, of course Aegis-type integrated fire control and combat management systems.

As a bonus, from an emissions perspective, a cruiser with a dual band radar looks a lot like a carrier with a dual band radar. Or maybe that other contact is another cruiser and the carrier is somewhere else. Or has its radars off. Emissions doesn’t tell you. With the right ECM and radar signature management, your active radar won’t help you either at range. Better go look, and hope you can radio your buddies back before you eat a missile.

On to missiles, and the tubes that launch them. The Mk. 57 can handle a greater volume of exhaust gasses than the Mk. 41, but the sheer number of deployed Mk. 41 tubes means missiles will be developed for that. Also, while the Mk. 57 is a bigger tube, it’s not much bigger, and there’s no missile around that would not fit in a Mk. 41 but would fit in a Mk. 57. Plus, the Mk. 57 modules are rather bulkier than those of the Mk. 41. So Mk. 41 it is! And we’d like to pack her with missiles. To hell with 80 missiles on nearly 15,000 tons. If we can’t do better than the 128 cells of a Ticonderoga, we should go home. Ideally we’d fit four of the big 64-missile clusters off the Ticonderogas for a total of 256 missile tubes. This gives us plenty of space for SAMs, including ballistic missile defense capable ones, LRASMs, Tomahawks, and VL-ASROCs.

Now, let’s talk about the gun. DDG-1000 originally had an ambitious vertical gun with guided shells, but this was shelved. The impact of development costs remains on the final design. I am not sold at all on ambitious gun projects that aren’t railguns, and those are nowhere near ready. The best estimates on the range of the Advanced Gun System put the ships entirely too close to shore. I’m fine with 155 mm, but 155 mm without being able to share shells (and shell development projects) with the army is patently absurd. And I’m still not entirely sold on the need these days, given how many other options there are for getting firepower on the beach, and how nasty coastal defenses can be. For my design, I’m quite satisfied with the 127mm/64 LW gun from Oto Melara. 127mm is a pretty standard naval gun caliber, and there are plenty of guided shells in that caliber under development.

There’s no need for extra antiship missile launchers given plenty of VLS cells and LRASM, so we don’t need to worry about those.

Point defense duties will be handled by at least two Rolling Airframe Missile launchers, mounted, well, wherever there’s room. Possibly amidships. Possibly fore and aft, which is rather more traditional.

Since we’re not obsessing over stealth, we can throw in some remote weapons stations and pintle mounted heavy machine guns to hose down any suicide bombers. Who will have no trouble finding a stealth boat because they use their eyeballs, not radar.

For propulsion, we’re going to go for Integrated Electric Propulsion, which has also been done on the Zumwalts. And could have been tested somewhere else. There’s no reason why it should be hard. Generators are run by diesel engines and gas turbines, and electric motors drive the screws. I’d like to take some time on a demonstrator to explore steerable propulsion pods for the electric motors in a military context, specifically focusing on cost, agility, and noise.

Helicopter fit is the usual hangar for two SH-60-size birds and beartrap-equipped deck. No reason to change it. Though, given the size, we should probably expand the hangar a bit to accommodate several drones.

Antisubmarine warfare is not our focus, but we should make a bit of effort to be prepared. A nice bow sonar and variable-depth towed array will do nicely, as will the usual pair of triple 325mm torpedo tubes amidships. Something like the Thales UMS 4110 CL sonar for the bow and a Captas 4 in the towed role.

Project LSAT

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When you look at the soldier’s load, ammo is a natural place to consider weight reductions. Less weight means more ammo. To deal with ammo weight, we can make the bullets smaller, or change their composition. We’ve tried Caseless Ammo, and that proved to have some significant technical challenges. What if we kept the case, but made it from something else?

Enter the LSAT project.

The idea behind LSAT was to create lighter cartridges using polymer cases and telescoped1 cartridge construction, and compare those to using caseless ammo based on the G-11 project. Of course, polymer isn’t brass, and this presents some design challenges. With a brass case, you can make a sturdy rim2 that an extractor claw can grab. You can then pull the case, spent or live, out of the chamber. This doesn’t work for polymer cases. A polymer rim of similar design isn’t strong enough for an extractor claw to pull the round out. You can only push the polymer case, which makes ejection a challenge.

To deal with this problem, the LSAT light machine gun uses a swinging chamber. When the chamber swings down to feed a round, the previous round is pushed forward into the ejection chute. The chamber then swings up to interface with the barrel for firing.

The focus of LSAT was a Light Machine Gun first setup, since the current US Army LMG, the M249, is considerably heavier than an M4. There’s more weight savings to be had there. The end result was a weapon prototype that weighed 9.4 lbs for the polymer-cased telescoped ammo version3. The version firing caseless ammo weighed a little more because of the need for extra components to provide an adequate chamber seal. Polymer-cased telescoped ammo is 40% lighter and takes up 12% less volume than conventional brass-cased ammo, so a belt of 100 rounds of 5.56 mm LSAT ammo weighs about 2 pounds, rather than the roughly 3.3 lbs for a 100 round belt of 5.56 mm NATO.

Let’s briefly talk about the LSAT rifle before getting into some analysis. The LSAT rifle is much less further along designwise than the LSAT LMG. Much of this is due to the fact that the US Army’s existing rifle, the M4, is already really lightweight. It’s an excellent weapon, and weight savings from ammo changes will be less noticeable with a 30 round magazine than with a 100 or 200 round belt. Further weight savings here are likely going to require materials changes.

Recently, the LSAT program started looking at the development of 6.5 mm cased telescoped ammunition, and weapons to fire them.

And now for the breakdown. First, I like the idea of continuing research into small arms development. And I like the idea of trying to keep it evolutionary rather than trying to force a revolution like with Project SPIW or the OICW. I like the LSAT LMG and the 5.56 mm LSAT round best. I’m a big fan of weight reduction, and the weight reduction in both weapon and ammo weight are big wins for the infantryman. I also like that combination for really only having one variable being played with. We’re still using the same 5.56 mm rounds, with the 5.56 mm bullets that we know, but we’re trying to use new materials to reduce the weight burden.

I’m also fine with the 5.56 mm LSAT rifle being put on the back burner. Weight savings from lighter bullets is less attractive here because we’re dealing with significantly fewer bullets. Plus, we already have a solid, lightweight rifle. Weight reductions there are probably going to come from rifle materials, not bullet design. I’m also ok with having a different round for the belt-fed infantry support weapons and the carbines. Linked and loose ammo are basically two different things anyway.

What about the new 6.5 mm projects? That really depends on the goal of those projects. If they’re looking to replace 7.62 mm NATO with a 6.5 mm LSAT round, I’d be okay with that. Or at least, I’d be fine with looking into that and testing the daylights out of that concept. And I would also be fine with a DMR-type ‘heavy rifle’ that fired the same round, in the same vein as the Dragunov rifle.

I would not be happy with any kind of effort to switch the general issue carbine from 5.56 mm anything to 6.5 mm anything. I do not approve of the extra load. I do not approve of adding a whole bunch of extra range that the average grunt can’t use. I do not approve of ignoring a mountain of historical evidence across multiple wars that most infantry combat occurs at relatively short ranges of less than 300 meters. I do not approve of excessively optimizing to fight in Afghanistan. I do not approve of small arms solutions to problems of rules of engagement and airspace deconfliction. I do not approve of any deviation from the classic solution to the sniper problem of mortars and artillery and airstrikes.

Any effort to make the standard infantry rifle a morbidly obese4 affair with a fat, overly energetic cartridge is a return to 1950s US Army Ordnance Department thinking. That nonsense brought us the M-14, which is a piece of junk. Let’s not make the same mistakes of the past. History teaches us what our parents and grandparents did wrong so we can make our own mistakes, not steal theirs.

I’m happy to debate the merits of a different cartridge for the medium/general purpose machine gun role, but that’s a very separate question. And trying for a ‘single cartridge’ means compromising too many ways. Since the SCHV rounds are the least bad present compromise, I’m happy to try out polymer cased telescoped rounds there, where at least the projectile itself can be kept constant.

  1. Telescoped like the 40mm CTAS rounds, but way smaller of course. ↩
  2. Even on ‘rimless’ cases like 7.62 NATO. ↩
  3. This unloaded weapon weight is very nearly replicated in 5.56 mm NATO caliber by the Knights Armament Stoner 96 LMG. ↩
  4. Projected weight for an empty, opticless 6.5 mm LSAT ‘carbine’ is 8 lbs, which is about 33% heavier than an empty, opticless M4 carbine. It would make a good DMR. ↩

Parvusimperator Designs A Frigate

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I’ve talked about frigates before, and while I settled on the F100, it’s not ideal. Plus, designing things is fun. So I’m going to work up a frigate design sketch, and get exactly what I want. Unlike some of my other design sketches, this one will have requirements and some open questions. Consider it more of an RFP solicitation, because I don’t have the naval architecture skills to place components and be sure the ship is stable.

As with any good design, we’ll start with the mission first. We want a Frigate. Alas, that has become a rather nebulous concept these days, so permit me to resurrect an older, more appropriate term: destroyer escort. We want a relatively small1 ship geared toward the antisubmarine and antiaircraft2 missions. A token antiship armament will suffice.

For the antisubmarine mission, we want the following:

  1. Hangar space for two (2) LAMPS III[^helo] helicopters. These are critical. Helicopters allow for more coverage of the sea and rapid prosecution of contacts. I’m extremely disappointed with how few frigates accommodate two helicopters.

  2. A modern, variable-depth towed sonar array. This gives the best performance, and a modern towed array is a very useful and effective tool for hunting subs.

  3. A modern bow sonar. We’re looking for a good, effective bow sonar, that can accommodate future upgrades. Something reasonably sized and reasonably priced. This is less important than the towed array, so we’re open to savings here.

  4. A ‘beartrap’ hauldown device on the helicopter pad, to enable flight operations in a wider range of weather conditions.

For the Antiaircraft mission, we want the following:

  1. The Aegis Combat System, with NTDS datalinks and Cooperative Engagement Capability. This is the thing that’s going to hurt our budget, but we need it. This is the best integrated battlespace engagement system afloat. And it’s scaleable. We won’t want ballistic missile defense capability on these.

  2. Four multifunction PESA radar arrays, either SPY-1D(V) or SPY-1F(V). Here’s something that I’d need more information to choose from. I don’t know the weight, cost, and capability differences here, and frigates have gone either way on these3. I’m inclined to think the -1F is the way to go, but I won’t sell the bigger -D model short without data.

  3. A 3D Air Search radar to complement the SPY-1 array. Again, lacking the relevant comparison data on effectiveness and price, I can’t specify one. Offhand the SMART-L might fit the bill, but we might also have something smaller available that would be a reasonable cost compromise.

  4. Forty Eight (48) VLS tubes. No less. We want the American Mk. 41 or Mk. 57 tubes, since they can carry a wider variety of missile types. We’ll need to carry VL-ASROC or similar in addition to SM-2, SM-6, and ESSM SAMs. We’re not too particular as to layout though, and it may work better to use the peripheral mounting capability of the Mk. 57 tubes to place some on either side of the helicopter hangar, in addition to the usual forward mounting position on the bow.

  5. Two (2) Mk. 49 Rolling Airframe Missile Launchers. CIWS is important. Ask the USS Stark. Two launchers provide excellent coverage. And we’re going with missiles instead of Phalanx or Goalkeeper because the missiles are the more effective system.

  6. Three (3) Mk. 99 Fire Control System radars for terminal illumination. ESSM and SM-2 both feature terminal semi-active radar homing guidance, at least at present. These provide the radar.

That covers the key points. Let’s talk a few others.

As mentioned before, a token antiship missile armament will suffice. We’ll take eight Naval Strike Missiles4 in two quad launchers mounted amidships. Good enough for dealing with trouble if it shows up unexpectedly.

To save space and weight (and cost), we’re only requiring a 76 mm gun. Probably the Oto-Melara 76mm/62 Super Rapido. We’re also not too particular as to where it goes. We’d expect it to be in the ‘A’ turret (forwardmost) position, but it might work better in the ‘Q’ turret (amidships) position, as on the Oliver Hazard Perry-class. Make it work, that’s all we ask.

Lightweight torpedoes have long been standard equipment for prosecuting close submarine contacts. We won’t argue. A pair of triple-tube launchers for 324 mm torpedoes will do nicely.

We’ll also want some smaller guns to take out small attack craft or suicide bombers. We’ll go with a pair of M242 25mm autocannons in remote weapon stations, mounted amidships. Also a few 12.7mm M2 machine guns amidships, and a few more Ma Deuces on the fantail.

I’m not going to comment on ECM and decoys beyond specifying modern suites of both. Open source data on ECM system effectiveness is basically nonexistent, so I won’t comment further.

Now, let’s talk propulsion. We would expect some kind of combined diesel/gas turbine system5 with two screws. We would also like a maximum speed of at least 28 knots, and a range of 4,500 nautical miles at a cruising speed of 20 knots. A 20 knot cruising speed will enable her to keep up with just about any task force you please, and 4,500 nautical miles will do a good job of getting you from friendly base to friendly base, and refueling at sea is something we know how to do.

We would guesstimate a crew compliment, including officers and men for the ship as well as flight personnel, to be about 250. By modern standards, this is probably a little heavy, but that’s ok. We want to be sure there are enough men for proper damage control drills.

As for the hull and superstructure, we’d like good internal subdivision in the hull, and we won’t sweat an overabundance of low observability features beyond a bit of angling and avoiding corner reflectors. We’ll keep everything pretty conventional in terms of hull shape in order to keep the costs down. Also to keep stability up.

  1. Guesstimating based on other designs, 5,700 tons or so. Nothing set in stone, of course. ↩
  2. Okay, anti-antiship missile. ↩
  3. SPY-1D is used on destroyers like the Arleigh Burke and derivatives, as well as the F100. SPY-1F is used on the Fridtjof Nansens. If the F100 can accommodate the -1D, so can we, but the -1F might be a better buy. More data is required. ↩
  4. We would also accept, and very much like, eight HF-3s, but NSMs are smaller and cheaper, so they’re what’s required. ↩
  5. i.e. CODOG or CODAG depending on the economics of the engines and gearboxes in question. Again, I don’t have those numbers, so I’m not going to sweat picking one. I would also not say no to COGAG. ↩

Tesla Motors: Ignoring Facts of Human-Machine Interaction Since 2014

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Okay, I’ve had about enough of Tesla’s zombie legion of brainwashed fans reflexively and ignorantly defending them on autopilot grounds, so it’s time for a good old fashioned rant. I have two targets.

First: autopilot itself. Tesla’s autopilot is a nifty technological achievement. In its current state, though, it’s dangerous, and it disregards seventy years of research into how humans interact with machines. This book, on the specific topic of human reliability in transit systems, cites just over two hundred sources. In the world of trains, locomotive cabs usually feature a device called an alerter. If the driver doesn’t flip a switch or press a button every so often, the locomotive automatically stops.

The locomotive, actually, is a good analogue for the specific sort of cognitive load imposed by driving with an assisted cruise control system. If you read my Train Simulator review, you have some idea what I mean. For the benefit of you who did not read it, let me sum up.

Driving a car manually is a task with relatively evenly-distributed (low) difficulty. It takes constant attention to keep from hitting something or driving off the road. It may take more attention at times, but there’s a certain minimum cognitive load below which you can no longer drive a car. Sure, it’s no helicopter, but you do have to be paying at least a little bit of attention. This is materially different from driving a train or a semi-automatic car.

Piloting those two forms of transit requires so nearly zero input from the driver as to be indistinguishable therefrom. In both cases, the vehicle handles the moment-to-moment input required to keep itself from crashing into things1. The driver has no ongoing task to keep his mind focused. A quick sampling of Wikipedia articles on train crashes shows, broadly speaking, two sorts of accident which capture almost every incident: equipment failures causing derailment, and driver inattentiveness causing a train to run into another train2. In fact, the trend with trains is increasing computerization and automation, because—shocker—it turns out that humans are very bad at watching nothing happen with boring predictability for dozens or hundreds of hours, then leaping into action the moment something begins to go wrong. This article, by a self-proclaimed UI expert3 goes into great detail on the problem, using Google’s experience with testing self-driving cars as an example. The train industry knows it’s a problem, too, hence the use of the alerter system I mentioned earlier.

“Well then, you ought to love what Tesla is doing!” I hear you say. Don’t get me wrong, I think they’re making intriguing products4, and the technology which goes into even the limited autopilot available to Tesla drivers is amazing stuff. That said, there’s a twofold problem.

First, no self-driving system—not even Google’s more advanced fleet of research vehicles—is perfect. Nor will they ever be. Computerizing a train is trivial in comparison. There’s very little control to be done, and even less at the train itself. (Mostly, it happens at the switching and signaling level, and nowadays that’s done from a centralized control room.) There are very few instances driving a train where you can see an obstacle soon enough to stop before hitting it, and very few instances where it’s worth stopping to avoid hitting the thing you might hit. Again, though, hitting a deer with a train is materially different than hitting a deer with a luxury sedan. More generally, there’s a lot more to hit with a car, a lot more of it is dangerous, and it’s a lot more difficult to tell into which category—dangerous or no—a certain piece of stuff falls.

Second, there’s a problem with both driver alertness systems and marketing. To the first point, requiring that you have your hands on the wheel is not enough. There’s a reason a locomotive alerter system requires a conscious action every minute or so. Without that constant requirement for cognition, the system turns into another thing you just forget about. To the second, calling something which clearly does not drive the car automatically an ‘autopilot’ is the height of stupidity5. Which brings me to the second rant I mentioned at the start of the article.

Tesla fans.

You see, whenever anyone says, “Maybe Tesla shouldn’t call their assisted driving system Autopilot, because that means something which pilots automatically,” an enormous gaggle of geeks push their glasses up their noses and say, “Actually…”6

I’m going to stop you right there, strawman7 in a Tesla polo. If your argument starts with “Actually” and hinges on quibbling over the definition of words, it’s a bad argument. Tesla Autopilot is not an autopilot. “What about airplane autopilots?” you may ask. “Those are pilot assistance devices. They don’t fly the airplane from start to finish.” Precisely. The pilot still has lots to do8, even to the point of changing speeds and headings by hand at times. More to the point, it’s almost impossible to hit another plane with a plane unless you’re actively trying9. Not so with cars. Cars exist in an environment where the obstacles are thick and ever-present. A dozing pilot is usually a recipe for egg on his face and a stiff reprimand. A dozing driver is a recipe for someone dying.

I also sometimes hear Tesla fans (and owners) saying, in effect, “Just pay attention like I do.” The hubris there is incredible. No, you are not unlike the rest of the human race. You suffer from the same attention deficit when monitoring a process which mostly works but sometimes fails catastrophically as does the remainder of the human race. It is overwhelmingly more likely that you overestimate your own capability than that you’re some specially talented attention-payer.

To quote Lenin, “What is to be done?” Fortunately, we have seventy years of research on this sort of thing to dip into. If your system is going to require occasional human intervention by design, it has to require conscious action on the same time scale on which intervention will be required. Trains can get away with a button to push every minute because things happen so slowly. Planes have very little to hit and lots to do even when the plane is flying itself. Cars have neither luxury. To safely drive an Autopilot-equipped car, you have to be paying attention all the time. Therefore, you have to be doing something all the time.

I say that thing ought to be steering. I’m fine with adaptive speed, and I’m also fine with all kinds of driver aids. Lane-keeping assist? Shake the wheel and display a warning if I’m doing something wrong. Automatic emergency braking? By all means. These are things computers are good at, and which humans can’t do: seeing a specific set of circumstances and reacting faster than humans. Until the day when a car can drive me from my house to my office with no input from me—a day further away than most people think—the only safe way for me, or anyone, to drive is to be forced to pay attention.

Update 04/21/17
I’m not usually one to revisit already-posted articles, but this is just too much. In this Ars Technica comment, a Tesla owner describes “multiple uncommanded braking events” since the last software update. In the very same post, he calls his Tesla “the best car I’ve ever owned”.

If you needed further proof of the Tesla fan’s mindset, there it is.

  1. Whether by advanced computer systems and machine vision, or by the way flanged steel wheels on top of steel rails stay coupled in ordinary circumstances. ↩
  2. Sometimes, driver inattentiveness causes derailments, too, as when a driver fails to slow to the appropriate speed for a certain stretch of track. ↩
  3. I like his use of a topical top-level domain. We over here at .press salute you, sir! ↩
  4. Electric cars weren’t cool five years ago. Now they’re kind of cool10. ↩
  5. In a stroke of genius, Cadillac called a similar system ‘Super Cruise’. I’ll be frank with you: when a salesman is going down the list of options for your new Caddy, and he says, “Do you want to add Super Cruise?” your answer is definitely going to be, “Heck yes. What’s Super Cruise?” It just sounds that cool. Also, it has a better, though not quite ideal, solution to the driver attentiveness problem. There’s a little IR camera on the steering column which tracks your gaze and requires you to look at the road. ↩
  6. Yes, I realize that also describes me and this article. I also just fixed my glasses. ↩
  7. Never let it be said that our qualities do not include self-awareness and self-deprecation! ↩
  8. The occasional embarrassed dozing pilot story notwithstanding. ↩
  9. That’s why it’s always news on the exceedingly rare occasions when it happens, and frequently news when it doesn’t, but merely almost happens. ↩
  10. If poorly built, but Tesla say they’re working on that. ↩

Rampant Armata Speculation

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Let’s have some fun with rumors, speculation, and armchair analysis, shall we?

We don’t know very much about Russia’s new tank, the T-14. In my review, I made the tacit (and completely groundless) assumption that the turret shell concealed some heavy protection for the gun. Something tank-like, i.e. that the frontal armor of the gun could be expected to withstand APFSDS rounds as well as big, high end ATGMs. Like the front of the turret of a Leopard 2A6/-A7/-E or an M1A2.

Let’s try to poke at this assumption a little, shall we?

First off, let’s forget about side protection. No tank in existence can take a modern sabot round to the turret flank and not care. Focus on the front. Clearly, the outer “shell” has negligible protective value. It does hold a lot of systems, most of which are fragile. Of course, there’s nothing else behind the turret face, so hits there will probably tear straight through the fragile sensors and APS effectors. The gun mantlet is not readily apparent, and the outer shell seems to be in the way. Compare the M1A2 and the Leopard 2A6, both of which have big, thick mantlet armor atop and around the main gun. This is curiously absent from the T-14.

Remember, composite armors trade weight for thickness especially when compared to an equivalent mass of steel. So if we want to stop sabot rounds from a tank, we’re going to need a bunch of bulk. And since we’d like to be able to elevate and depress our gun, we’re going to expect to see quite a bit of exposed, movable bulk.

We can also find some images showing a T-14 turret mounted on the relatively light (28-30 tonne) Kurganets APC hull. So there’s at least one lightweight version of the turret out there. Of course, the shell could hide more armor on the T-14 version, maybe. We can’t rule out two versions. Now, it’s hard to figure out how one could hide bulky composites under the shell, given its shape and attachment methods, but we really can’t be sure about anything. The Kurganets hull is a little unusual if only because this idea has gotten very little traction elsewhere. The Swedes have a CV90 version with a low-pressure 120 mm gun prototyped, but have not ordered it and have not achieved any sales. The US Army has a version of the Stryker with a 105 mm gun and autoloader, but this version hasn’t been too popular. The US Army has moved to add more conventional autocannon firepower to some Stryker APCs to get more firepower in the Stryker Brigade Combat Team. So no one else really likes this concept.

We should also note that T-14 has a lot of active protection system effectors. There are ten tubes for the Afghanit hard-kill APS, five on each side of the turret. Additionally, there are two boxes of twelve soft-kill (likely some kind of obscurant) effectors facing outward, one box on each side of the turret, and another twenty-four soft kill effectors in a vertically configured box to protect the roof. That is an awful lot of active protection.

For comparison, the Merkava IV has a Trophy (hard-kill) APS launcher on each side of the turret. Each launcher holds three effectors. No additional soft-kill system is mounted on Merkava. Of course, Merkava IV is also heavily armored, and Trophy is seen as a supplement for flank protection against high-end ATGMs (e.g. Kornet).

So what might this mean? Well, we know that the T-14 has a bigger hull than T-72. Scaling comparisons will tell us this. Also, we know that we have to fit all three crewmen up front, so that front compartment must be significantly bigger to accomodate the three crewmen plus all of the displays and computers. Also, loads of hull armor, since the front appears to be quite thick (it’s sloped, and likely some kind of composite or composite + ERA, all of which takes space). We don’t actually save all that much room in the turret basket, since we still have to have some sort of (probably vertical) carousel for enough rounds to make all this worthwhile. And while the engine is a weird X-configuration model, it’s quite a bit more powerful than the one on T-72, and it still needs a radiator, transmission, and of course fuel. So we’d expect the hull to be noticeably bigger, and this agrees with what we can see from playing with scaling.

We also know that while the T-14 is heavier than the T-72, it’s still a light MBT. While it’s hard to draw comparisons to Western analogues, we do note the large hull and thick glacis armor would eat up a lot of mass.

Historically, the Russians have been quite strict about the weight of their tanks, simply because their infrastructure can’t take the weight of big Western tanks.1 For this reason, they pioneered the autoloader in the 1960s, and made heavier use of ERA than anyone else. Both are lighter than their respective alternatives. It’s quite possible that something had to give to keep the weight within tolerances, and the designers chose to accept a less well protected gun. Active protection systems are pretty good at defeating ATGMs, and they’ve made sure to have something for both direct-attack and top-attack weapons. In the current small wars, they’re not likely worried about sabots.

Further, the roof seems like it would blow-out in the event the ammunition storage compartment is compromised, and there are a pair of blow-out panels on the T-14’s belly. So ammunition cook-off will not likely kill the crew. Further, the Russians have put an escape hatch on the floor of the crew compartment. Good for them.

Could Afghanit be effective against sabot rounds? Specifically, the kind of APFSDS rounds fired by a modern tank gun (120 or 125 mm). Again, we can’t know for sure. It might be possible. But I’m disinclined to believe the present statements about it. Afghanit looks to shoot some kind of fragmentation or mini-EFP warhead to damage incoming projectiles. It’s simple and cheap, and works great against RPGs and ATGMs. But these are relatively fragile. An APFSDS round is a solid rod of some dense alloy (based on depleted uranium or tungsten), and it’s moving a lot faster than a missile.

It’s certainly not impossible to intercept an APFSDS round, but it’s a lot more difficult than intercepting a rocket. And the extent to which you disrupt it is important. You intercepted it. Great. What’s the effect? Is it destroyed? Damaged? Destabilized? If the round is still incoming, how much armor is needed to stop it? And what was the incoming speed and penetrator design? Test details are, naturally, hard to find. So color me skeptical that Afghanit can reduce the effectiveness of modern APFSDS rounds2 sufficiently for a lightly armored turret3 to be able to stop them.

Okay. So what do we think? Given the large amount of active protection systems, the reported wait, the size of the hull, and the nature of the turret shell, I think it’s quite possible the Russians are taking the T-14 in a new direction with a less protected main gun. They’ve pushed the envelope before. Some things have caught on, some things haven’t. This isn’t a notion I’m overly fond of, but that’s ok. The proof is in the combat, and the Russians will likely get into some before too long4. The keen observer might then be able to learn something as to whether or not these ideas work.

  1. I pick on Leopard 2 and Abrams enough, so let’s talk Challenger 2. Wouldn’t want the British to feel left out. With their “Streetfighter” Urban Warfare supplemental armor kit, the Challenger 2 tips the scales at 75 tonnes. ↩
  2. To be clear, I mean M829A3 or M829A4 depleted uranium APFSDS rounds fired from the M256 gun on an Abrams or the DM63 round from the Rheinmetall 120 mm/L55 gun on the Leopard 2A6 and subsequent models. Modern rounds, modern guns, no reduced-power charges. We never know what ad copy means, but that’s what you think of when I say “tank rounds shot at Russian tanks,” da? ↩
  3. Supposing the T-14 turret is lightly armored, that. But I suppose we should still define things, so something meeting STANAG 4569 level 5 or 6. In plain english, something ‘resistant to 30 mm APFSDS rounds”. ↩
  4. Unlike some other countries, the Russians are likely to get into a fight and test their new stuff. ↩

Armored Vehicle Fuel Capacities

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I’ve found these to be quite hard to find on the net. All do not include supplementary drop tank options. Except where specified, variants have the same capacity of the original.

VehicleFuel (US Gal)Fuel (L)
M15051,907.6
M1 with UAAPU4501,703.4
Leopard 2317.01,200
Challenger 2420.61,592
Leclerc343.41,300
K2342.41,296
Namer369.81,400
Merkava IV369.81,400
T-72264.21,000
T-80B486.11,840
T-80U467.61,770
T-90317.01,200
T-14426.61,615
M2197745.7
CV9030/CV9035221.9840
SPz Puma237.8900
ASCOD227.2860
Boxer MRAV145.3550
BMP-1122.0462
BMP-2122.0460
BMP-3184.9700
M11380302.8
M113A195359.6
Marder 1172.2652
Stryker52.8200
BTR-8079.3300
BTR-9079.3300
M270163617.0
M109135511
2S1145.3550
Panzerhaubitze 2000264.21,000
K9 Thunder224.5850
Centauro137.4520
G6/G6-52/G6-52L184.9700

Borgundy Modular Aerial Bomb Family

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And now, time to develop some native industry. Our specific impetus is that we think cluster bombs are highly useful things. While the Dublin Convention bans them for signatories, plenty of nations didn’t sign on. Including arch-nemesis Russia. And likely troublemaker China. And frankly, why should they? Yes, war is horrible. Yes, the effect on the civilian population really sucks. But there are tons of unexploded shells in Northern France from World War I and tons of unexploded bombs throughout Europe from World War II. Let’s ban those too! Really, let’s just ban war. Oh wait, we tried that. Didn’t work1. Additionally, the Obama administration wouldn’t sell new customers any cluster munitions. So, we really can’t trust the United States to supply our needs, though Trump might change that in the near term. And neither can all of those middle eastern countries who have bought western aircraft/artillery. Time to fill a market void. And if we’re building cluster bombs, why not build some regular unitary-warhead bombs too?

Our goal is to reduce costs as much as possible by building a complete modular family. We’re going to have two sizes of cluster bomb dispensers: one in the 500ish kg size class, and one in the 1,000ish kg size class. We’ll then have various submunitions packages that we can put in the dispensers. We’ll review these packages first, then go over what we can attach to a dispenser (or a unitary warhead for that matter).

Package one is a bit of a mouthful, because it’s our analogue for the BLU-97/B. It’s a triple-threat, HEAT/Frag/Incendiary submunition. It’s got a shaped charge warhead to provide some anti-armor effect. This will necessitate an integral ballute to orient the shaped charge correctly so it will work if it hits armor. We don’t need a ton of penetration, since we’re hitting the roof. So we can make the charge rather small. This shaped charge warhead has a fragmentation casing to provide anti-infantry capability. It is also equipped with incendiary sustainer: material that burns hot for a while like magnesium that can be scattered by the explosion of the shaped charge to start fires. Three ways to do its job. Very cool. Total weight is about 1.55 kg, with explosive content of 290 g of cyclotol. These are cylindrical, with a diameter of 64 mm and a length of 17 cm. Really nice general purpose munitions.

Our second package is somewhat larger. These are thermobaric submunitions, also known as fuel-air explosives. For maximum safety, it actually uses a solid fuel air explosive warhead, weighing 33 kg. The idea here is to create a massive firestorm, which has a significant pressure wave secondary effect. It’s about 70 cm long and 34 cm in diameter, with an overall weight of 58 kg. It works with a dual fuse mechanism: the first releases the SFAE at an altitude of about 9 m and extends a probe, the second detonates everything when the probe hits the ground. The significant overpressure wave can be used for mine clearing, in addition to the obvious destructive uses.

Package three is a dual purpose mine. It uses an explosively-formed penetrator to provide anti armor capability, and it’s also equipped with a fragmentation casing for antipersonnel work. It has a parachute to slow it’s fall and a spring-loaded mechanism to right itself once it lands. This part is important since the explosively-formed penetrator must be pointing up to work. The self righting mechanism triggers after impact plus a time delay. There’s an additional delay before the mine is armed. It contains about 0.6 kg of explosive, has an overall weight of 2.4 kg, a diameter of 10 cm and a height of 15 cm.

Since the mines from package three are so small, they can be used alone or combined with other things. One such example is package four, which combines a bunch of our dual purpose mines with runway-destroying boosted penetrators. These are about 1.1 meters long and 10.2 cm wide, with a weight of 20.4 kg. A parachute delays the fall and orients them downward, at which point the parachute is jettisoned and a rocket drives them deep into the runway before a 3 kg warhead detonates. The mines are added to complicate reopening the runway.

Package five is some more dedicated anti-armor kit. These are submunitions, again equipped with an explosively-formed penetrator warhead, plus a ranging laser and an infrared sensor to determine if a tank is below the submunition. There’s also a self destruct mechanism so that if the submunition hits the ground without finding a tank, it will detonate anyway. There are drag flaps to induce a bit of oscillation in the fall so that the submunition can scan an area, while keeping the warhead pointed earthward. Diameter of the submunition is 13 cm, height is 9.5 cm, and weight is 3.4 kg. This is an analogue of the BLU-109. While in the 80s this was state of the art, by now the electronics industry has caught up, and the result isn’t too hard to duplicate. Offhand, Germany and Sweden both make similar submunitions.

That should cover most submunition needs that we can think of right now, but more can be added later. We also have a series of unitary bomb bodies. These are low-drag bodies in the 250, 500, 1,000, 1,500, and 2,000 kg size classes. There are also 1,000 and 2,000 kg class reinforced-case penetrator bodies. All unitary bombs have nose and tail fuse wells, and can accept a bunch of fuses, including contact, mechanical delay, and radar altimeter.

Both the unitary bomb bodies and the cluster bomb canisters can interface with a comprehensive set of accessory kits. There’s a basic tailfin kit for stability. A variant of this kit allows fin angles to be adjusted, in order to scatter bomblets for the cluster bombs by means of rotational inertia. There are a couple different fall delaying options, including parachute kits and ballute kits. In terms of guidance packages, there’s a GPS/INS equipped tail kit. This can be used alone or with a nose guidance kit. Laser guidance and IIR guidance nose kits are available. These may also be used with a conventional tail kit if a laser-guided bomb is desired, for example, instead of a Laser/GPS guided bomb. The IIR guidance kits are capable of transmitting back to a human operator or performing stand-alone automatic target recognition on a preloaded target. We can also add a wing kit if a standoff glide capability is desired.

  1. No really. Cf. the Kellogg-Briand pact of 1928. If you think any such notion can actually work, or that this war will actually be the last war, then I have some bridges to sell you. ↩

US Ground Combat Systems Are Not Obsolete

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I came across this article in the Free Beacon this morning, whose headline reads as follows: “Army’s Ground Combat Systems Risk Being Surpassed By Russia, China”.

Look, if you’re reading this article, you’ve read a lot of our articles. You know that I, Fishbreath, am not the expert on ground combat systems. Not really my cup of tea. You know, therefore, that when I say, “Man, this article is dead wrong,” that it really is just flat out dead wrong. Let me revise the Free Beacon’s headline: “Army’s Ground Combat Systems Risk Being Roughly Equalled By Russia, China After 40 Years Of Curb-Stomping Dominance”.

In the modern era, a combat system’s age is not nearly as important as its current capability. The T-14 and the Type 99 are modern tanks. They compete against the modern American system, the M1A2, in the three categories by which all armored fighting vehicles are judged: firepower, protection, and systems1.

First off: firepower. The American contender mounts the stalwart Rheinmetall 120mm smoothbore gun in the 44-caliber length. The Germans, being a little squeamish about depleted uranium2, made an L/55 version for higher muzzle velocities. This gun, either the lengthened version or the original with depleted uranium, still sits in the top tier of tank guns as far as penetration goes3. The Russian and Chinese entries both use the Russian standard 125mm caliber; the Armata uses the 2A82, the shiny new version sans fume extractor for installation in the unmanned turret, while the Type 99 uses the ZPT-98, the traditional Chinese clone of the 2A46. Neither is clearly superior to the Western choice of gun. Standard 125mm ammo is nevertheless lighter and shorter overall (counting the penetrator and propellant) than the one-piece 120mm loads usually fired through the Rheinmetall guns. In exchange, the Russian-style gun gains the ability to launch ATGMs—questionably effective against modern tanks—and a little bit more power for HEAT rounds, which have the same issue as the ATGMs. Call this one a slight win for the Abrams.

Next: protection. The Type 99 falls behind quickly here; it’s more or less a T-72 hull, and the T-72 doesn’t have a great deal of headroom for armor. Too, the Type 99 has to deal with the swampy, rice-paddied Chinese south. The Chinese can’t build a T-72-based tank much heavier than the current 52 to 54 tons, and the protection they can achieve there is limited, given what they have to work with. The Armata, though it weighs in in the 50ish-ton range itself, has the benefit of an unmanned turret. Unmanned turrets can be smaller, and armored volume is expensive in weight terms. Our own parvusimperator claims Armata has roughly Western-equivalent protection. Give Armata an edge, even; there are no squishy humans in its turret, and no explodey ammo in its hull. The unmanned turret, unproven though it may be, neatly isolates the two. Call this one a slight win for the Russians.

Finally: systems. This is the hardest one to write about, since the Russians and the Chinese aren’t talking. We know more or less what’s in the M1A2: nice digital moving-map navigation, color displays, modern sighting units, separate ones for the commander and gunner, with nice thermal displays. I think it’s reasonable to assume the Armata has similar. We can see that it has an independent sight for the commander, and the Russian avionics industry has built color MFDs and moving map systems in the past. Presumably, the charionics4 in their tanks won’t be too far behind. It’s even less possible to speculate about the Chinese; their latest MBT entered service around the turn of the century, and who knows what they’ve stuck in it. Call this one a tie between the Americans and the Russians.

In a way, though, systems are the least important item here. Unlike armor or guns, swapping out the computers, stabilizers, navigation systems, and sights in tanks is more or less trivial. There may be integration costs, and there are definitely upgrade costs, but ordinarily, you don’t run into the same sort of critical design problems you find when, say, trying to cram a 140mm gun into an Abrams turret.

So that about wraps it up. Contra the Free Beacon article, the new Combloc5 tanks do not surpass the Abrams in any meaningful way. Where they are superior, it’s a matter of degrees. Elsewhere, they still fall behind the Abrams. What we have today is not a new era of Combloc dominance. It’s a return to parity for the first time in almost forty years.

Let’s go back a few years more than that. It’s 1972, and the fearsome T-72 has just entered service. It’s faster than the M-60, hits harder, has better armor, and is being cranked out of the Soviet tank factories at an astonishing rate. The armored fist of the Soviet Union could well crush Western Europe. This doesn’t sit well with Western Europe.

The Germans and Americans are already hard at work on the MBT-70. It reaches a little too far, and doesn’t quite work out. The Germans and Americans each take the blueprints and build something on their own, and we get the Leopard 2 and the M1 Abrams, entering service in 1979 and 1980. This begins the aforementioned era of Western tank dominance. The Abrams and the Leo 2 are vastly superior to the T-72 and T-80. The Russians do some various upgrade projects to the T-72 and T-80 over the years, but never regain the lead. The Leo 2 and Abrams see upgrades on more or less the same schedule; they’re still a generation ahead.

Finally, today. The Russians have Armata, a legitimate contender; the Chinese have the Type 99, which is sort of the Gripen to the Abrams/Armata F-22: some of the same technologies, still half a class behind. Which brings us to the final decider. Quantity.

The Russians have about one hundred Armatas. They only entered service last year, so I give them a pass. Their eventual plan is to acquire about 2300.

The Chinese have about 800 Type 99s. I have no idea if they’re still being produced.

The Americans have roughly 1000 M1A2s, the most recent Abrams. Of course, we also have about 5000 M1A1s of various marks, most of which have been upgraded to include nearly-modern electronics.

Even if we allow that the Type 99 and the Armata are superior to the average Abrams in American service, which is wrong, we still have twice as many as both other types combined.

The Free Beacon may say otherwise, but I say we’re doing just fine.

  1. To include sights and viewers, as well as command and control computers. ↩
  2. Understandable, given that in most hypothetical wars, the Wehrmacht Bundeswehr would be shooting it over their own land. ↩
  3. As far as anyone knows. Armies are a little cagey about revealing how punchy their guns are, for some unfathomable national security reason. ↩
  4. Electronic systems for tanks, by analogy to avionics. (An avion is a French plane, a char is a French tank.) ↩
  5. Yes, I know they are, respectively, not Communists anymore and nowadays only Communists inasmuch as they’re heirs to a truly Communist body count. I don’t care. ‘Combloc’ is a reasonable way to refer to Russia and China in the context of this article. ↩

Borgundian Mechanized Infantry Loadout

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Let’s get this started. I’m following my own challenge rules, which you can find here. We’ve made a bunch of decisions so far, so let’s get those out of the way. Oh, and all weights are going to be in pounds, because I’m an American. Divide by 2.2 to get weights in commie kilos.

Carbine: HK 416. I didn’t specify a barrel length preference then, but we’ll go with 14.5 inches. Comes to 7.69 lbs empty. We’ll also need ammo in that gun. Thirty rounds of 62 grain M855A1 or similar in an aluminum, 30 round magazine comes to 1.06 lbs. Per doctrine, we’ll need a suppressor and an optic. We’ll take an Aimpoint Comp M4 red dot (0.74 lbs with mount and killflash) and a Surefire 556RC2 suppressor (1.06 lbs.). Also, we’ll need an IR laser/illuminator, because battles don’t stop at night. My choice there would be the B.E. Meyers MAWL-DA. I don’t have a weight for this, so I’m going to guesstimate 0.5 lbs based on other, similar devices. Plus a sling, which is going to set us back about another quarter pound. All of that adds up to 11.3 lbs, which is kinda sucky, actually. Oh well. Lots of capability there, not much to be done about it. Quit complaining and drop and give me thirty.

Armor time. See here for why I picked what I picked. IOTV (and we’ll add the deltoid (fragmentation) protectors, but not the side plates) is 26.69 lbs for a size medium. Size medium ECH is three pounds. Ballistic Eyewear adds 0.15 lbs, foam earplugs add 0.1 lbs, and knee and elbow pads add another 0.4 lbs. An FM50 gas mask rounds out the protective equipment list, adding another 1.85 lbs. Total weight for protective gear is 32.19 lbs.

Ammo. Pretty straightforward. Six spare thirty round magazines. Two M67 frag grenades. And two smoke grenades. Something like the M18, but with added thermal obscurants. Six mags comes to 6.36 lbs, two M67s comes to 1.76 lbs, and two M18s comes to 2.38 lbs, for a total ammo load of 10.5 lbs. Which doesn’t seem like a lot, but remember the vehicle holds more.

On to comestibles. I’ll go into more detail on this elsewhere. Since these are mechanized infantrymen, they have a big armored vehicle to move them around and carry stuff like food and water in reasonable quantities. Only the essentials need to be carried. For the standard, temperate European operating environment, we think two liters of water is an adequate amount to carry on the person, and we can top this off as needed from the vehicle stores or resupply. For food, we really only expect the soldier to carry an iron ration with him. This will take the form of something like the US military’s First Strike Ration, which is a hot-pocket-like sandwich that supplies the calorie and nutritional needs for one battle day. A full two-liter camelbak-type1 bladder is 4.88 lbs, and a First Strike Ration is 1.95 lbs, bringing total comestible weight to 6.83 lbs.

There are a few other items we need to list out. There’s the IFAK, the Individual First Aid Kit. This is for two reasons. First, it means a soldier can perform some first aid on his buddy. Second, a medic can always find some basic supplies (tourniquet, pressure bandage, sterile gloves) when he needs them in a pinch. Add a pound. We also need to issue a knife. For knife fighting duties, I’d like a double-edged knife, like the Gerber Mk. II. However, most knife tasks are utility tasks for the modern soldier. For these, a tough single-edge knife will work better. Something like a Ka-Bar. Tough, effective, legendary. I have one and love it. Add another 1.23 lbs for a Ka-bar and sheath. And we’ll need some night vision kit. I’ve been going for the high-end, feature-rich stuff. No sense in stopping now. We’ll take the PSQ-20B, which gives us third generation image intensifying optics plus thermal optics in one rugged, two pound unit. At least the battery pack is detachable and can be affixed to the back of the helmet for balance. Finally, we’ll need a radio. The PRC-159 from Harris should do nicely. Compatible with the once and future frequencies, plenty of encryption, good battery life. With battery, it weighs 1.72 lbs.

Almost done, I swear. The standard poncho with liner is a really great piece of kit. It’s waterproof, surprisingly warm, and extremely packable. That’s my one concession to weather that might crop up unexpectedly. Obviously, coats are worn when you can expect bad weather, like say in the winter. 1.5 lbs for the poncho and liner. And we’ll add a multitool, because they are ridiculously useful little things. 0.6 lbs for that.

Let’s wrap up by looking at what we’re not issuing. Recall that this is a regular rifleman. He is not a squad leader. Therefore, he does not usually need navigation equipment so he does not have a lensatic compass, maps, or a portable GPS receiver as a matter of course. He might be given these things as part of a specific mission, and that’s fine. Spare batteries for the various electronic devices mentioned are carried aboard the vehicle normally. As a side note, just about all the devices here take AA batteries. Logistical commonality strikes again!2 Similarly, cleaning kits are generally expected to be carried aboard the vehicle. as are entrenching tools. Further, since they aren’t on soldier’s backs, we can issue full size picks and spades, not the lame folding versions.

All-up weight for our kit is 68.87 lbs. Which is on the heavy side, but about on par with other modern armies. Remember, the pack is normally left in the vehicle, so it’s not counted in the fighting load.

1.) I actually prefer the Source brand bladders.
2.) Did you expect anything different from me?

Design Compromises: A Case Study

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Every design is a compromise. There are no free lunches. And trying to work out the why can be very informative. So let’s take a look at one of my favorite tanks, the M1 Abrams, and look at some design compromises, and their results. Since it’s very nearly equivalent, and designed at about the same time, I will use the Leopard 2 as a point of comparison. The Leopard 2 is somewhat more conventional internally in a few subtle ways.

The most obvious difference is the engines. Both designs have 1,500 hp engines, but where the Leopard 2 uses a pretty conventional twin-turbo V12 diesel, the Abrams uses a gas turbine. This gives the Abrams better acceleration, but also necessitates a greater internal fuel capacity. Where the Leopard 2 can get away with 1,200 L of fuel stowage, the Abrams needs about 1,900 L to meet its (shorter) range requirements. More fuel means more space. We can note that the Abrams has fuel tanks on either side of the driver, in addition to in various other places. The Leopard 2 does not have fuel stored up front in the hull.

The hull front on the Leopard 2 is used to store ammo in a pretty conventional rack. There’s not much in the way of blast venting provision here, so a penetration would be extremely bad news. That said, this is a pretty common place to store reserve ammo1, and hull hits are much less likely than turret hits. Still, from a survivability perspective, this is clearly not ideal.

The Abrams designers were able to shoehorn a few (six 120mm rounds, more of the smaller 105mm rounds) into a compartment aft by the engine, because of the shape of the gas turbine power pack. This rear ammo compartment has blow-out panels and a heavy door to isolate it from the crew compartment, but it’s not a lot of reserve ammo. The Abrams carries the vast majority of its ammo in the turret bustle. On the one hand, this makes subdivision easy. It’s a simple engineering exercise to add blow-out panels to the bustle, and this makes the Abrams among the most survivable tanks in the world.

Storing 34 120mm rounds in the bustle has its disadvantages. It forces a wide turret. Turret height is determined by the desired maximum gun depression, and a wide, tall turret means the armored volume is correspondingly large. The Abrams has considerably more armored volume than the Leopard, both in relative terms (i.e. crew space), and in absolute terms. Because so much of the Abrams’ ammo load is in the turret, there’s a significant amount of armor protecting the side of the turret bustle. More volume means it takes more weight to provide the same level of protection. Or, you have to use more expensive exotic materials (like depleted uranium).

On the other hand, more internal volume is another survivability gain. Armor penetrations are less likely to cause significant casualties or destroy enough systems to score a mission kill simply because there’s more volume to deal with, and volume leads to dispersion, which is the enemy of the shaped charge jet.

To be honest, on these grounds I prefer the survivability over protection. Protection can be added, but it’s much harder to do a redesign in favor of survivability.

We can see another difference in the guns on the latest models. Since the M1A1, the Abrams has been equipped with a license built Rheinmetall 120mm/L44 gun, just like Leopard 2s up to the A5 model. Subsequently, the Germans went to a longer L55 gun for more penetrating power. The Americans have not. So what gives?

Recall that Americans like their depleted uranium. The Germans don’t. Something something environment or something. Anyway, depleted uranium makes awesome armor. It also makes awesome armor piercing rounds. The Americans have done a good job of sinking plenty of R&D funding into new depleted uranium APFSDS rounds. They’re up to a fifth iteration of the design with the M829A4 round. So when adapting a longer barreled gun proved more costly than anticipated in the 90s due to stabilization issues, the US Army quietly dropped the project and stuck with their fancy rounds.

I don’t know if the Leopard 2 didn’t have the same stabilization issues as the Abrams with the longer gun, or if the Germans were just unwilling to change round composition. Regardless, the Germans adapted a longer gun. It means they can use tungsten-based APFSDS rounds, but it also means they will have somewhat more restricted mobility in urban environments.

For this one, six of one, half a dozen of the other. I’m indifferent here, provided both are available. I do wonder if the DU rounds will also perform better in the L55 gun, or if they’re optimized for the L44.

I suppose I should also comment on the engines. I strongly suspect that the Germans made the right choice here with the conventional V12 diesel, though I would strongly prefer an air-cooled model like the AVDS-17902. It’s possible the gas turbine just hasn’t gotten enough development funds, but a diesel engine company can push research into the civilian sector to recoup costs there, in addition to the military. I also approve of forward fuel tanks, and don’t approve of forward ammo stowage. Remember, well-designed fuel tanks provide reasonable supplemental protection.

1.) It’s also used on the Leclerc, K2, and Challenger 2, among others. Doesn’t mean I like it.
2.) Early versions powered the M60 Patton, and the 1,200 hp variant powers the Namer. A 1,500 hp variant is available.