General Theory of Optimal Combat Vehicle Design: A project

[shin_getter]

There appears to be no well organized thought on combat vehicle design evolution. If you survey the space of internet arguments, non-parametric arguments based on piecemeal history or other theory of war dominates. If one looks at history, bad design is not uncommon, for example British or Nazi tank design or Large Cruisers. Even with hindsight, some forums can argue over optimal ship gun size and belt thickness for decades after their retirement.

Is the problem solvable? Now for someone building for a uncertain future there are many unknowns. Given hindsight however? The optimal design and tactics given technological and resource/political constraints can be found using game theory.

To mathematically solve optimality for a system as large as war itself is beyond practical information and computational capabilities. A simplified model problem can be solved very quickly however.
--------------------
Models of warfare has existed, but none the commonly known ones are very useful for thinking. Models like Lanchester's model of attrition or mobility-armor-firepower is insufficient. Models like RAND full scale simulations is too complex to draw patterns to enable quick understanding.

I believe it is possible to generate good mental models for thinking about optimal vehicle design, by simplifying the vast complexity down to a few parameters. I think the kind of models in basic micro-economics is a great way to gain intuition over the problem.

Perhaps this effort has been done already, as it is not too hard to develop. This post is inspired by models within "Fleet tactics and Coastal Combat" after all. Do tell me good theorists that thought about this if you know some.

----------------------------------------------
Here is my initial simplifying model:
Vehicles design space to be reduced to:
Firepower to cost curve, Sensors to cost curve, Defense to cost curve, Mobility to cost curve
I'll post the results of this model later, I am first collecting background information on this.

Now I am sure many here have their own models on how to think about vehicle design, you can also share it here.

 

[UpForce]

There are so many jokes about circular development paths in the APC/IFV/MBT community; interested to see what you come up with nonetheless. How do you define "cost" here? Casualties, vehicle attrition, acquisition price, ratio of objectives reached? Do you intend to model interdependent variables such as increased firepower resulting in decreased mobility? Is there room for an adversarial model? My heuristic to combat vehicle design is that of Alfred, Batman always has a function (i.e. a push button solution) available to the problem at hand ...

 

[shin_getter]

Land combat is the most complicated and involves combination of hugely dissimilar forces and terrain conditions and would have to be tacked later. From a complexity perspective, one would probably go from surface naval, air, and finally to land forces.

As for adversarial reaction, their existence does not prevent existence of an optimal strategy as proven in game theory under nash equilibrium. For weapons systems without strong secrecy the problem can be reduced to a perfect information game for both sides which result in pure (as opposed to mixed, randomized strategy: rock paper scissors) optimal strategy. Now one can play alternative strategies if the opponent does something suboptimal, but if both side seek optimality there is only one or at most a few finite combinations.

As for cost, it is easy to just reduce it to a single number to make models solvable. More complicated models are only meaningful if one can get meaning and accurate parameters to feed into it. This kind of information is simply not available to the public and I seriously doubt most governments are even capable of collecting and computing them as it falls under social science.
-------------

 

[HoHun]

Is the problem solvable? Now for someone building for a uncertain future there are many unknowns. Given hindsight however? The optimal design and tactics given technological and resource/political constraints can be found using game theory.

To mathematically solve optimality for a system as large as war itself is beyond practical information and computational capabilities. A simplified model problem can be solved very quickly however.

Hi,

That's quite an interesting thought, but at the same time, the outlines appear rather abstract. Perhaps you could get the ball rolling by demonstrating your idea using a highly simplified model?

Regards,

Henning (HoHun)

 

[Foo Fighter]

The big problem I see in ANY land vehicle project is making a decent spec/role and then sticking to it. If we took every penny wasted in pointless rounds of development that go nowhere we would have a huge amount to get something recent, run it and while doing that develop the next project. You can talk actual model (Or Kylie Minogue (I know but I'm old so live with it)) as much as you like but it is all pointless.

 

[uk 75]

All weapons are easier to design when you have the spur of an "enemy in being".
Tanks produced between 1918 and 1939 all proved to be fairly useless.
By the end of World War 2 the Russians had built T34 the Germans Panther the US Sherman and Pershing and the Brits the first Centurion.
Since the end of the Cold War the US combined arms force of M1 tanks M2 infantry fighting vehicles and M109/MLRS self propelled artillery has remained unmatched by all opponents except large bombs dug into roads/roadsides.
The formula seems to be to balance out armour, weapon, speed, range and cost based on what you want the vehicle to do.

 

[riggerrob]

Returning to the basic 4 elements: mobility, communications, armament and protection. the challenge is balancing those elements and balancing them against anticipated foes.
As one wag suggested, if you neglect armament, then you get a 70 ton portable radio.
Protection and mobility are often at odds. The perfect protected/armored vehicle ends up too heavy to move. Mobility is often limited by local bridges and roads. For example, if you consider a 70 ton Merkava to be the best modern tank .... but most of your bridges are only rated for 40 tons, then Merkava is useless. So armor gets reduced until the AFV is light enough to cross local bridges. This forces compromises like only armoring the front enough to defeat known weapons, while installing considerably less armor on sides, rear, top and bottom.
Speaking of bottom armor, up until 2000 AFVs were designed to protect against known anti-tank mines, but Al Queda, Mujahaden, Taliban, ISIS, etc. soon learned that they could defeat even a 70 ton M1 Abrams by burying a full ton of explosives under a road.
Older theories can only design an AFV to fight known weapons ... IOW fight the last war.

 

[uk 75]

The armoured vehicle in its various forms has evolved since the earliest forms in World War1. But the basic idea of a tracked or wheeled vehicle armed with some kind of weapon or tool/load bed has remained the same.
Wargamers and Sci fi writers have dreamt up hover or anti-grav vehicles. Robot or remote control vehicles have been suggested over the years.
The M1 is over 40 years old so I am not holding my breath for anything radically different.

 

[shin_getter]

Disclaimer: the logic of the model is trivial. The numbers needed to fill the model is anything but so. I think there is no real comprehension of design without good guess on the numbers however.

Now if one thinks out everything it'd fill a book and more, here is something to start with:
-----
Some simplifying conditions:
- Very basic model: near mirror vehicle competition, no networks/combined arms, vehicle dynamics to projectile interaction neglected:

1. Combat vehicles start conflict outside range of each other and one or both side have to move toward each other
2. Victory comes from using launched projectile to defeat the opponent force before opponent do it to you

Means to do so:
1. Out Range opponent
2. Faster attack when in mutual range
3. Defeat opponent first in exchange of fire

Typical Laws of Economics and combat that enable the problem to be solvable:
A. In real systems, linear increase in performance beyond thresholds demand superlinear increase in cost.
B. No characteristic is perfect: everything is probability curve spanned across space and time. Systems fail, people fail, weird environments happen.
--------
Now lets solve for the weapon range problem, ignoring other factors (as it may not be relevant in some domains).

For every increase in weapon range:
1. Increase sensor costs, radar range is Quad Root of Power, Passive is square root. Plus problem with accuracy.
2. Increased munition costs, see rocket question. Also requirements for accuracy (munition guidance, datalinks, etc)
3. Increased launcher costs (to fire heavier munitions, carry relevant sensors)

At some point the increase in percentage kill per dollar in range would be too low to be worth it. We can characterize this with a simplified model:

Base Line vehicle 1 -> V1
Extended weapon range vehicle 2 -> V2

Now with some additional simplification one can make this solvable:
If odds of successful out-range engagement is greater than the fractional cost increase, than V2 is a superior design.

One can look "epoch" of warfare depending on different key constraints. (most expensive marginally) In sensor constrained kill chains, early sensing, stealth and dispersion rules. In launcher constrained kill chains, local superiority in force density is decisive. In munition cost constrained warfare...well that is yet to be thought through but improving munition efficiency is likely what matters here.

The model also predicts that with defense improvements, effective range would be reduced.

------------
Now that is just a very simple model. There are many topics to work on that can be analyzed by model building: Now many of the topics might have been thought through, but layman like me can't find resources,

1. Relationship between value of mobility with different offense-defense context
2. Relationship between strategic position and platform design
3. The logic of battle networks
4. The logic of carrier (one vehicle carrying another, from ships to rail to trucks) design
5. Mixed force structures and nash equilibrium
6. Optimizing an entire arms race in an changing technological context
7. How technology impacts tempo of warfare. (this should have real impact on strategic thinking for non-military)
8. Technological development context for stable warfare development and context for revolutionary changes

and so on....

 

[shin_getter]

All weapons are easier to design when you have the spur of an "enemy in being"....
The formula seems to be to balance out armour, weapon, speed, range and cost based on what you want the vehicle to do.

Returning to the basic 4 elements: mobility, communications, armament and protection. the challenge is balancing those elements and balancing them against anticipated foes.

To "balance parameters" is like "making money is about buy low and sell high", highly insufficient idea for figuring out what to do.

Imagine the design space spanning BT tanks, tankettes to O-Ni, how do you know where the optimal design fall?

If you are building to "counter the enemy", you can end up with Hitler facing KV-1 and ordering Tiger IIs and Maus to overmatch Russian heavy armor. Two can play the game and Russians could have returned with KV-4 and KV-5.

Now, at some point is additional armor, additional firepower inferior to additional mobility, numbers and reliability. But where is that point? How would one figure this out, without a world war involving dozens of designs facing each other? How can one read comparative tank trials and material requirements and figure this out? Something like bridging requirements isn't a hard limit either, if the benefit in weight overmatch the combat engineering and strategic mobility problems, a super heavy would make sense.

In the modern era, the space in vehicle design have again expanded to 1ton to 70ton, and that is for vehicles capable of defeating each other.
---------------------------
Now, I did think about this comparative common problem. Here is what I've thought about:

Using the model:
1.Out-Range
2.Effective Attack first
3.Win exchanges
---
1. Improving gun power increases range where armor can be defeated
2. Due to tank combat being LOS constrained, and limitation of eyeball mkI, massive gun power is not worth while with rapidly diminishing returns. I'd estimate reliable 1km is enough for wwII.
3. Improving armor decreases enemy gun effective range. However a larger gun is cheaper than a heavier armored vehicle.
4. Tanks are too small for extensive compartmentalization to reliably win mutual penetrations

From this simple model, and focused on pure vehicle combat: a lightly armored vehicle that have sufficient gun power and fast response (try to spot first, first on target) is optimal.

With this model, heavy armor on a fleet level simply can not be optimal in a pure vehicle to vehicle combat context as it is dominated by lighter vehicles with more gun power. This model is insufficient to explain why medium tanks happened to be most effective. (as opposed to TDs or cavalry tanks)

However it is known that tanks fight things that are not other vehicles. It explains the armor in the sense:

The human, individually and in a group, has upper limit in payload and has to trade off destructive power to weapons range.
With a vehicle that:
1. Has protection to enforce a weapon immunity zone towards the human moveable weapons
2. Has sensor/firepower to reliably defeat the human at immunity zone ranges

Would dominate infantry. I believe this defines optimal armor if attainable without excessive cost. It is enough to enable tank weapons out range infantry weapons. As such, HMG, anti-tank rifles, man handleable anti-tank guns and such has to be defeated by armor. Rocket projectors with low range can be out ranged and would not be a requirement.

High efficiency in vehicle combat and anti-infantry combat thus defines the period medium tank.

-------------
Mobility is a factor that probably will tie into relationships with sensing and fire control that is will take some work.