A Slightly Different Take on Mechs vs Tanks
There are many pages and videos comparing mechs vs tanks. This video prompted an interesting response by Apock1239 - a response which I commend as being intelligent, thoughtful and wrong.
So here’s my take.
Rather than make generalised comparisons, I’m going to consider specific benefits attributed to mechs and give examples as to how we could do something similar with today’s technology, but don’t because it’s obviously stupid. Don’t get me wrong; I love mech games, and especially BattleTech, but I can’t see how the tech could be more than a novelty.
Let’s start with some comments responding to the above-linked video.
Most servo systems rely on batteries, (no onboard fuel required) which can be integrated into the legs, arms, body, side walls, basically anywhere with any kind of free space. Add that servos and batteries are actually more power efficient (and more powerful in general) than gas engines, and we start seeing a new story. Mechs are actually mechanically simpler, needing only ONE electric motor per axis of rotation, contrary to popular belief. You would need about 16 to make a BattleTech style mech. The number of moving parts on a tank, due to it's basic nature, is much higher than the number of moving parts you'd find on the more mainstream mecha from basically any franchise. A gasoline engine alone has many more moving parts than an entire Electrically powered mecha would. Not to mention the servos on a mech could very easily be armored and made more resilient than the treads of a tank could ever be.
Let’s grant the premise about electric motors and servos. In fact, let’s assume that only half of the claimed 16 electric motors are needed for locomotion; that’s 8 motors.
So rather than driving leg servos, consider a vehicle with 8 wheels, each driven by a motor. On the mech, every single one of those motors and its associated mechanisms is critical; damage to any one joint system severely impacts mobility. On a multi-wheeled vehicle, it’s possible for wheels to fail with minimal effect, as long as those failed wheels don’t foul movement.
What if we hypothesise myomers instead of rotary engines? That would favour mechs, right? Or we could use those myomers to power an oscillating drive train to convert the energy back to rotation (think train pistons).
Another common “advantage” is that mechs provide a flexible, elevated firing platform. If we wanted a flexible, elevated firing platform we could do it using today’s technology by putting a scissor-lift on tanks between the hull and turret. It doesn’t take long to come up with multiple reasons why no military has seriously tried this.
Finally, let’s talk armour. Fiction loves big tanky things, whether they are knights, dragons, tanks, battleships, or towering robot mechs. But big tanky things either need massive amounts of firepower to keep stuff away (in which case your primary defense is “kill it first”, not the armour) or enough armour to shrug off lots of hits.
There are brief periods in history when armour beats weapons. But invariably the weapons win. Armour is not without value, but most of the time it’s a much better long term plan to not be hit than to be able to absorb hits. Armour also comes at significant cost in resources and weight. Yes, armour keeps you alive, but if you can stay alive without armour then you don’t need to carry all that weight.
Mechs are invariably portrayed as big tanky things. They have a big profile, which makes them easy targets. Being roughly humanoid, their forward profile tends to be their largest profile; this is the profile that just about every modern military design tries to minimise. Their means of locomotion and any arm-mounted armaments are highly exposed, further increasing the amount of armour required. Modern tanks are almost exactly the opposite; they are compact (maximising internal area vs surface area) with a small frontal profile (minimising the area that needs to be armoured heavily).
At this point I’ll grant one for the mech: if you have an overwhelming tech advantage, they are very impressive and intimidating. But as soon as the enemy achieves tech parity the mechs are going down fast.
Consider the evolution of modern warfare. The primary offensive weapon systems are artillery (lots of firepower that’s hard to counter-attack) and missiles or drones (small, manoeuvrable and expendable). What do these have in common? They have minimal armour but survive by being a difficult target to engage. Infantry and vehicles are used to take and hold objectives, consolidating the opportunities made by artillery and drones.
Mechs suffer from being expensive generalists. You can easily find sentences of the form “A mech can do X, which a Y can’t, but not as well as a Z”. If you can only have 1 unit and it must fill lots of roles, then a generalist is good. But if I can have a tank squad and an infantry squad and some helicopters or drones and some artillery, how many mechs to I need to be as effective?
In almost every game, a good mix of specialists will beat a group of generalists. Because with good tactics each specialist unit can be performing optimally, whereas a generalist by definition is never performing optimally, because it’s only ever doing part of what it’s capable of.
But I don’t actually think that mechs are the logical outcome of trying to design a generalist military vehicle. I think that we’ve already decided that the answer is mechs, and are searching for a question that works. That’s fine for fiction, but isn’t a winning strategy for reality.