What color is your power armor?

My recent analysis of the combat exoskeletons from Edge of Tomorrow made me realize that there are at least three types of humanoid or animal-like mechanical fighting machines frequently depicted in science fiction, and I’ve decided to explore their feasibility. I think they can be grouped into these categories:

1. Power armor / exoskeleton
2. Mechwarrior (“Mech”)
3. Jaeger / Zord

Power armor / exoskeleton

Defining characteristics:

• Can only accommodate one person.
• Provides some combination of enhanced strength, endurance, speed, or carrying capacity.
• Best thought of as a “suit.”
• If worn, the person’s overall size is not so big that they can’t fit through standard-sized doorways or into vehicles designed for un-armored people.
• The suited person remains narrow enough to fit between trees and duck under branches in wooded areas.
• Depicted in Edge of Tomorrow, the Fallout, Starcraft, and Halo video games

Problems and disadvantages:

• Limited power supply (can’t fit a big battery into a relatively small machine and expect it to last long)
• Could limit mobility and agility so much that you’re better off not wearing it.
• Potentially dangerous to the wearer and to comrades who are not wearing their own, protective suits. Risk of serious accidents rises if your strength is amplified and you have lots of heavy, unyielding metal strapped to your body.

Feasibility:

• Mildly feasible.
• Light exoskeleton that increases load-carrying capacity of infantrymen, or lets them carry heavier weapons than otherwise possible (like .50 caliber machine guns) could be valuable and practical someday.
• Heavy, fully enclosed exoskeleton for short duration, close-combat missions might also be practical.
• Best use might be in noncombat logistic roles, like picking up and moving heavy cargo around bases.
• Discussed at length in my blog entry about Edge of Tomorrow.

Mechwarrior (“Mech”)

Defining characteristics:

• Can accommodate one or two people.
• Can’t fit through standard-sized doorways or into other vehicles except large cargo planes and maybe large cargo helicopters.
• Similar size and firepower as a tank or attack helicopter.
• Should be thought of as a military vehicle and not as a suit.
• Primarily or exclusively designed to fight using guns, missiles, and other ranged weapons. Usually ill-suited for hand-to-hand combat.
• In theory, can traverse rougher terrain than wheeled/tracked vehicles thanks to its legs.
• Depicted in Return of the Jedi, the Mechwarrior and Titanfall video games

Problems and disadvantages:

• Having legs instead of wheels or caterpillar tracks would be problematic.
  • Legs would propel the vehicle slower than wheels or caterpillar treads. The ride would also be much bumpier, which would be exhausting and potentially disorienting for crewmen. Combat performance would suffer if the crewmen were dizzy and beat-up by the time they arrived at the battle site.
  • Mobility advantage over wheeled and tracked vehicles is questionable since mechs would have higher ground pressure–all of their weight would be concentrated on two feet, whereas traditional armored vehicles spread out their weight over 6-8 large wheels or two, long caterpillar tracks. This means a mech would have worse problems sinking into the mud and getting stuck.
  • Having a humanoid or animal-like layout (i.e. – legs for sure, and possibly arms as well) would increase a fighting vehicle’s surface-area-to-volume-ratio compared to a traditional wheeled or tracked vehicle with the same size and firepower. A mech would thus need to devote more of its mass to armor to achieve the same, all-around ballistic protection as a tank. Increasing the armor would necessitate deleting other things to save weight (e.g. – reduce fuel, ammo, or main weapon size/power).
  • The powertrain would need to be heavier and more complicated. A conventional tank like a T-72 essentially has a big truck engine that is transversely mounted and spins a shaft connected to one wheel on either side of the vehicle. It’s a simple and compact layout. A layout designed to move two, multi-jointed legs would be much more mechanically complex, requiring multiple motors and many spinning shafts, meaning more weight and more moving parts that can fail.
• Its width would prevent it from going down alleys or between closely-spaced trees. Human enemies could run to constricted areas like that for cover. The mech’s big selling point–that it can go places where trucks and tanks can’t–is eroded thanks to the tree problem.
• Its tallness would impose many problems.
  • Forested areas become even more impassable since branches can block mechs and/or obscure their crewman’s view of targets at ground level. Power lines, some road lights, and bridges/overpasses also turn into obstacles. The mechs definitely can’t be used for peacekeeping or domestic policing if they’re going to be constantly snapping power lines and cutting off electricity to whole neighborhoods. High ground pressure might also damage roads by leaving footprint indentations.
  • The taller and wider a mech is, the bigger of a target it becomes, and the easier it is for enemies to shoot it from longer ranges.
  • Mech would have high centers of gravity that would introduce the risk of tip-overs. Even if falling over didn’t destroy a mech, it could do enough damage and injury to the vehicle and crewman, respectively, to knock them out of the fight.
  • The torque from shooting heavy weapons mounted high on the mechwarrior would tip it over.
• Accidental injury problem would be worse than in power armor / exoskeletons. For example, if a mech fell over by accident, it could crush friendly 20 infantrymen.

Feasibility:

• Probably infeasible. There’s a reason why there are tens of thousands of advanced tanks in global military service, but not even one, basic mech.
• It would be better to use aircraft and infantry to patrol and fight in areas where the terrain is too rough to bring in tanks and wheeled vehicles. Probably not worth it to build mechs just for specialty engagements in those places. Mechs might provide an advantage there, but would be inferior to traditional military vehicles in all other types of terrain. Not a flexible asset.
• Building a useful mech is a much bigger technical challenge than making powered exoskeletons.
• If we decided to build combat mechs anyway:
  • Designing them with four or more legs would make them safer, more stable, less likely to get stuck in the mud (ground pressure problem), and would offer a smoother ride than mechs with two legs. Problematically, a human pilot wouldn’t be able to intuitively control a machine that had more than two legs. Like in a car, the pilot would probably use a steering wheel and pedals to input direction and speed commands to the mech, and the mech’s computer would figure out exactly how to reposition the 4+ legs to achieve that. However, this disconnect between inputs and fine movements of the vehicle could lead to problems if the computer stepped on, say, a land mine, friendly infantryman, or an open sewer hole that the human pilot could see and wanted to avoid.
  • Making it as low to the ground as possible, with its volume distributed horizontally as opposed to vertically, would make it more stable and reduce its target profile.
  • Spider-like or beetle-like mech makes more sense than human-like mech.
  • The number of legs would present a tradeoff between vehicle stability and smoothness of ride vs. fuel efficiency and mechanical complexity/breakdown rate. Unsure what the optimum number of legs would be, but “two legs bad” for sure.
  • Would probably need built-in wheels for easy transport over roads and flatter ground. Remember, it won’t be climbing jagged hills or stepping over big logs in the forest all the time. This would also be easier on the crewmen.
  • The most practical design might resemble a “walking excavator,” but with armor and heavy weapons comparable to what is found on APCs. Couldn’t have the same firepower, speed, or protection as a main battle tank. (Videos showing walking excavators in action: 1) https://youtu.be/Hn1aZQFhC40 2) https://youtu.be/j87k71kOBis)
  • Would have a 360 degree rotating gun turret, like almost all armored vehicles. Wouldn’t need as big of a cannon since heavily-armored tanks wouldn’t be able to get into the rugged terrain areas where mechs would operate (20mm – 40mm cannon would be fine against other mechs, infantry, structures, and entrenched positions).
  • Might make sense to have heavy-lift helicopters transport mechs to their battle/patrol zones (mountain top, forest clearing, sand dune area).
  • A fully automated mech that lacked human crewmen wouldn’t suffer from many of the problems listed in this section, like disorientation and exhaustion from a bumpy ride. Small, unmanned turret would reduce center of gravity as well.

Jaeger / Zord

• 

Defining characteristics:

• Huge. At least 100 ft tall. Size and firepower are comparable to warships (modern destroyer or cruiser).
• Strong enough to win fights with big groups of armored vehicles and planes attacking it at once.
• Best thought of as a “one-man army.”
• Can go anywhere since its feet are so big it can just step on and crush trees and walk up hills like they were steps. Can also wade through shallow bodies of water.
• Has standoff weapons like missiles and cannons but is also designed for hand-to-hand combat and striking with oversize, handheld weapons like giant swords.
• Depicted in Pacific Rim, several Godzilla movies, the Power Rangers TV show and movies.

• 

Problems and disadvantages:

• The “square-cube law,” along with limitations on the strength-to-weight ratios of physical materials, effectively prohibits the construction of machines this big that can also rapidly walk around and violently swing their arms (it also prohibits the existence of animals in the same size range).
  • Square cube law basically says that, as an object scales up in size while maintaining its original proportions, its volume and hence weight rises disproportionately. Arms and legs get really heavy, but the amount of interior space for motors and linkages to move them doesn’t grow as much. Explained well here: https://theconversation.com/some-bloody-rocket-science-gives-pacific-rim-uprising-an-extra-lift-92342
  • A Jaeger/Zord would have such heavy limbs as a result of that Law that even the biggest, most powerful motors in the world could only move them very slowly. See this article: https://www.zimbio.com/Beyond+the+Box+Office/articles/TzjPYG8JMuA/Pacific+Rim+How+Engineer+Sees+Jaeger
• Massive investment of money and resources into a single weapon that can only be in one place, at one time would probably be better spent on many smaller weapons (e.g. – tanks, fighter planes, mobile missile launchers) that can be spread out to patrol and fight enemies across large areas, and concentrated in one place when necessary to fight against a strong enemy.
• Falls and tip-overs would be fatal to human pilots. Accidentally falling onto buildings or groups of friendly troops could kill hundreds of people at once.
• Shares many of the same problems mech have, but to a worse degree.
• They would be gigantic targets that enemies could see and shoot at from dozens of miles away, or bomb from high altitudes. They wouldn’t be able to hide themselves except in cities among skyscrapers, in canyons, or perhaps by diving into deep bodies of water. In every other environment, they would be impossible to camouflage.
• Explored in my End of Evangelion review.

Feasibility:

• Infeasible for many scientific and engineering reasons.
• We would need Star Trek levels of technology (radically stronger and lighter materials, miniaturized fusion reactors, and cheap ways to build both) to make the sorts of Jaegers and Zords shown in the movies. With current technology we might be able to build Jaegers and Zords that were extremely slow, fragile, expensive, and of almost no military value. They would be missile- and gun platforms only, and would break themselves if they punched or kicked anything hard.
• Even if the Star Trek technology existed, it’s doubtful anyone would make a Jaeger/Zord since it’s better to create a land force made up of many small, expendable units than to invest everything in one giant, all-important fighting machine. A single point of failure is really bad. A force made of many units is also more flexible since they can be spread out across a large area.

Additional thoughts on power armor / exoskeletons

• The most realistic of the three types of fighting machines.
• A minimalist exoskeleton with attachment points for big weapons like .50 cal machine guns, grenade launchers, and recoilless missile launchers would let infantry squads bring heavier weapons on patrols into rugged terrain areas. Squad members wearing the exoskeletons could fill some of the firepower niche that mechs are intended to fill.
• Instead of all the troops wearing those exoskeletons with big weapons, it might be worn by every fifth or tenth man, specially trained for that equipment. Most of the troops would have normal weapons and would have no exoskeletons or lighter exoskeletons just designed to increase their load carrying capacity and to ease the physical strain of long marches.
• Might work like this: Squad leader keeps the .50 cal exo-soldier in the back of the line unless needed. If so, he calls him up and deploys him carefully.
• My thinking is guided by assumptions about existing science and tech. Exoskeletons would be totally plausible with Star Trek technology (e.g. – super light, super strong metal; flexible bulletproof body panels, personal fusion reactors).
• Avatar final battle would actually be ideal scenario to use heavy weapon exo-soldiers. Forest environment blocked air support and wheeled vehicles (the tree cover would have also made it impractical to deploy mechs). Idea was to use helicopters to insert troops, win, and then recover them after a few hours, so no risk of batteries dying. Enemies were large, so abnormally large weapons needed.
• Unclear if Edge of Tomorrow beach landing was well-suited to exo-soldiers. Mimics were very fast, but not actually that robust. Regular troops with normal weapons would have been better since they were faster and more agile. Also could have landed greater number of regular troops with same number of transport craft.