A Future Abrams Tank
Much debate has ensued over what the future of the M1 Abrams tank should be. Many have bought into the notion that the tank is dead. Others feel we should convert existing Abrams to improve its overall capabilities. What is universally accepted is that the existing Abrams has significant problems that must be addressed.
I think a lot of proposals for the Abrams are to convert it to perform roles that are really better suited to a medium tank based on the Bradley. At its core, the Abrams is a tank destroyer and there is still a place within the force for this capability. Missiles can be countered too easily to use them as the sole method of dealing with heavy armor enemies. But there need to be significant improvements in the overall capabilities of the Abrams.
The Engine Question
From the day the Abrams was created, there has been extensive arguments over the value of the turbine engine instead of a conventional diesel engine. A number of myths need to be addressed here. While the Abrams uses massive quantities of fuel, so do all other heavy tanks. The biggest difference is in how they are used. The British Challenger 2 is rated at about three gallons per mile in cross country operations and this uses a conventional diesel engine. Where there IS a major difference is when the engine is at idle but this problem can be compensated for by using auxillary power units. While the current Abrams powertrain consumes a lot of the Army's maintenance budget, this is largely because of the excessive size of the Abrams force and the age of the powertrains. The current Abrams engine uses 1960s technology and the U.S. currently maintains a fleet of around 8000 Abrams tanks. At the most, only 2000 of these tanks could EVER be put to use.
The turbine engine offers a number of significant advantages that should not be so easily dismissed. The first is that a turbine engine generally doesn't care what kind of fuel is being used. Whether it is the kerosene-type diesel the U.S. uses or standard diesel purchased locally abroad, the turbine can burn any of it with no real problems.
There is also the issue of smoke, particularly in cold weather. Conventional diesels put out enormous quantities of smoke when started, especially in cold weather. Turbines don't have this trait - they are smokeless engines regardless of conditions. Noise is another important factor that must be addressed. The turbine engine produces substantially lower noise than conventional diesels. These are important signatures being eliminated by using turbines.
Personally, I place these advantages as being of greater importance than the negatives associated with the turbines. One of the arguments used for conventional engines is to allow soldiers to follow the tank but with the size and weight of the Abrams, it isn't necessarily suitable in this role. There's also the issue of the blast from the Abrams 120mm cannon - do we really want infantry operating THAT close to this tank? If not (and I think there are better systems like the Assault Gun Mortar and Bradley Medium Tank for these roles) then I think we should keep the turbines in the Abrams. Most enemy don't possess thermal sights but they all have eyes and ears and the turbine makes the tank far less susceptible to these.
Tank armament is always an iffy thing but the real problem the Abrams has (that few people recognize) is that it can burn up ammo way too fast for the amount of ammunition it can hold. At the heart of this problem is the fact that the Abrams lacks an effective mid-size gun in its secondary armament. If a given target is anything that cannot be taken out by a .50 caliber machine gun, the only option available is the main gun. Moreover, there is no ammunition available for the main gun for any role other than anti-tank. So we need to make a number of changes here.
First is to develop an Abrams round that can accept 105mm semi-fixed artillery shells. This would dramatically improve the options available for using the main gun without having to go through all kinds of problems with developing and manufacturing new rounds. We will still only be able to carry 40 rounds of ammunition, but improved secondary armament can help this problem.
The Russian BMP-3 uses a 30mm auto-cannon for its secondary armament and looks like the best option for the Abrams as well. The 30mm offers excellent range and lethality and is readily available as it is used in a variety of systems already, including the AH-64 Apache. If we develop a round similar to the Bofors 40mm AP-3 round, we can effectively use this secondary gun against virtually any target.
Since the primary purpose of the ring mounts on the turret are for engaging nearby personnel threats, I would replace the commander's .50 caliber machine gun with the 30mm cannon mounted in a cupola like that of the M-60 tank. The loader's gun should continue to be the 7.62mm machine gun to give the tank a good mix of explosive and direct fires at close range.
We should also replace the standard smoke grenade arrangement with a breach loaded rack that could hold disposable grenade launchers. This would give us the ability to use these mounts for a variety of roles including smoke, marking, anti-personnel, and flame.
The two systems that should be added for improved protection are command-detonated Explosive Reactive Armor and the anti-RPG force field system currently in development. The most prevalent anti-tank weapon in the world is the RPG so the inclusion of this system is a no-brainer. This is also an effective anti-missile system as most anti-tank missiles rely on the shaped charges these force fields are designed to defeat.
CDERA can be effective in two roles. First is that it can serve as ERA to defeat most types of anti-tank munitions. Including the command detonation option allows the tank to serve as a rolling mount for anti-personnel mines. In close engagements, the ERA tiles can be detonated to devastate nearby enemy. In the future, sensors can be added to the system to allow for an active defense system at stand-off ranges.
Many call for the use of roofs on tanks in order to detonate top attack weapons at a stand-off distance from the tank and also to provide some cover for those using the secondary armaments. I think all tanks should have this capability, but it shouldn't be a permanent install as there are a number of situations where these roofs could pose a problem
Further discussions with others on this topic gives me the impression that regardless of what I personallly believe about the Abrams, many WANT a diesel engine in this tank. Regardless of it's weight and size issues, many combat arms folks want to use the Abrams in defensive and infantry support roles. While I do not support this idea, I feel obligated to share the knowledge I have of this issue so that if we DO decide to field a diesel version of the Abrams, then we do it properly.
Because of the tremendous weight of the Abrams, it is not well suited to a hybrid powertrain although the Allison parallel hybrid may be a potential option. Still, the notion of using batteries to power a tank may not be a particularly good idea as batteries tend to be awfully volatile in this usage where the vehicle is going to be getting pounded with explosives and kinetic energy projectiles regularly. Realistically, at this stage of man's technological development, we should still be using mechanical powertrains for tanks.
Contrary to popular belief, putting a 1500hp diesel engine is NOT going to yield significant gains in fuel consumption in and of itself (in cross country operations, the diesel British Challenger 2 and German Leopard are both rated at between 2 and 3 gallons of fuel per mile traveled which is around the average for the Abrams according to most sources). The problem with Abrams fuel consumption is not the engine, it is how the tank is currently used. You have to match up the appropriate powertrain for the role of the vehicle. As a rule of thumb:
1. Lots of idle time in a defensive posture is better suited to a diesel but is best suited to an APU which will burn the same amount of fuel in a day that an idling diesel will burn in an hour. For those who doubt this, consider the Russian T-90 tank - it is essentially a T-80 tank with a diesel replacing the turbine engine but they still put in an APU because of excessive idle fuel consumption. A large tank diesel can burn well over 5 gallons per hour at idle; better than the turbine but still an enormous amount of fuel for a vehicle that isn't moving.
2. Lots of stop and go at modest top speeds is slightly better suited to the turbine because of its bottom end torque from continuous combustion. You also don't get the smoke and noise of acceleration as with a diesel. The key here is that the tank is doing a lot of wide open acceleration, a role that is better suited to turbines as this is how they are designed to operate.
3. For relatively constant low speed driving, as with combat patrols and overwatch roles, you're better off with a diesel because you can save a considerable amount of fuel here and this is the sort of role in which diesels really excell - steady speeds.
4. For high constant speeds, the advantage kicks back to the turbine as diesels don't like running at max RPMs for considerable lengths of time whereas the turbine thrives on this. You may get slightly less fuel consumption, but this will be more than offset by maintenance costs and the turbine will have far less in this role. Many get confused here as civilian semi-trucks use conventional diesels and are cruising at 60mph with massive weight - what they fail to grasp is that these trucks typically have 13 to 18 forward gears to assist the engine in getting to that speed and maintaining; the Abrams currently has only 4 forward speeds and I haven't seen a tank transmission yet with more than 6 forward speeds.
Now then, where we have a problem today is that current Army doctrine is for cavalry type operations that tend to fall into categories 2 and 4, which means the Abrams should use a turbine based upon our current doctrine. On the other hand, modern warfare and most future conflicts are likely to focus more on operations that fall into categories 1 and 3 which leads us to a diesel conclusion. Unfortunately, many within the pro-diesel community just go with the idea that if we throw a big diesel in the Abrams, we can use it for ALL roles and achieve significant gains in fuel consumption. Keeping the high power levels will inevitably result in continued "lead footing" in the armor community, which is the REAL source of our excessive consumption of fuel. The problem isn't the engine - it is our practice of blasting across the countryside at 40mph+ when we don't need to and really shouldn't.
Since the entire reason people desire a shift to a diesel is to make the Abrams better for urban and infantry support roles, the obvious solution is to take the ability to fly about the countryside away from the Abrams. These intended roles do not need the ultra high power levels, and to be frank, the Abrams would be better in these roles WITHOUT the high power. A smaller diesel may sacrifice some acceleration but you make tremendous gains in fuel consumption and reliability. The key here is to downsize the engine in the transition. What I propose is to outfit the Abrams with a 900hp diesel for this application.
At 900hp, this Urban Abrams would still have a better power-to-weight ratio than the old M-60s (and most of the tanks used by nations we consider enemies) but it generally will use 40-50% less fuel than the larger diesel in this application, which translates into a very significant improvement of the turbine. The tank would still be capable of significant speeds that are adequate for most combat situations but it takes away the current ability to blast across the countryside, hence we will save additional fuel from ending this wasteful action in and of itself. Ideally, we could also add a "road gear" that would enable the tank to cruise at higher speeds on hard roads for long range transport without using tank transporters (the British Challenger 2 uses a total of 6 forward speeds with a 1200hp engine so there is really no obstacle to adding gears for on-road operations). The smaller diesel will give us the REAL gains in fuel consumption that many people desire.
To address the other half of the combustibles equation, I propose we do a crash development on a new gun that will use existing ammunition in a new way. As outlined in my article on Abrams ammunition, 105mm semi-fixed artillery ammunition comes in a lot of useful flavors for this particular application. With the greatly reduced fuel consumption of the small diesel engine, we won't need 498 gallons of fuel storage on this tank. Recent advances have been made using liquid propellants in guns that are not volatile when hit by enemy fire but are still very effective as propellants. The downside is that this application requires an autoloader to manage the propellant. But what about a semi-automatic gun?
Instead of a fully autoloading system, why not use a manually-fed autoloader? The loader would simply be loading the "autoloader" one round at a time with the actual feeding into the gun and injection of propellant being automated. If we design this system to use the 105mm projectiles, we gain a number of advantages with this design. For starters, we retain the manual loader and the flexibility of choosing specific rounds at will. Second, we can fit will over 100 rounds in the existing ammunition storage boxes of the Abrams while the propellant would be stored in modified tanks replacing the unneeded fuel storage, so we aren't losing space or survivability. Third is that without using the long tank rounds, we can increase the elevation of the main gun to heights more useful for this application, making the Abrams an artillery piece as well as a tank. And finally a far greater variety of ammunition would be available as the rifled 105mm artillery barrel is already compatible with all existing 105mm rounds but could also be used to fire HESH rounds, laser-guided rounds like the Russian Refleks, and dedicated anti-tank rounds like the British CHARM system. And realistically, we may be able to carry a total in excess of 120 main gun rounds in this configuration so we can carry significant quantities of a wide variety of ammunition. Plus the 105mm gun would be lighter in weight to boot - this will likely offset the gain in weight from switching to a diesel engine.
Personally, I still think a Bradley Medium Tank is better suited to this role, but since many in the combat arms community desire a diesel variant of the Abrams, this is probably the best approach to take. Use a smaller diesel engine to maximize our gains in fuel consumption and convert the main gun to a semi-automatic 105mm howitzer that uses liquid propellant with existing artillery projectiles. Throw in the 30mm cannons mentioned above and replace the existing built-in grenade launchers with breech loaded disposables and this should be an extremely potent platform. We'll end up with a much more reliable and cost effective system that should also be far more useful in the types of combat roles expected in the future.