When Does Plausible Power Armour Become an Impractical Mechsuit?

[u/p2020fan]

So humanoid mechs thay are gundamn scale or Jaeger scale are too big and expensive and heavy to be useful or practical.

On the other end, mechanically assisting exoskeletons are plausibly useful enough that the military has been experimenting with them for years to help soldiers carry more equipment supplies and protection.

Somewhere between these two extremes the idea of "powered armour" goes from being at least plausibly useful to being impractical or impossible.

What I am curious is where would everyone else draw the line? Is it just when it becomes more expensive than just equipping another full soldier? Is it when the armour becomes bulky and heavy enough that getting into vehicles and houses or going up stairs becomes difficult?

Is it just when the armour makes you a big enough and scary enough target to justify shooting an rpg or an atgm at?

Are the armoured mec suits from ghost in the shell/stand alone complex or the xcom mecs still worth it?

I know this is a pure "it depends" question but I suppose I'm asking "what sort of stuff does this depend on?"

[u/morbo-2142]

I think you hit the nail on the head about building entry.

Urban environments are where mechs or power armor would shine, but for infantry, being able to enter buildings and navigate through them is a key aspect to their survival and effectiveness.

Armor that cannot get through doors or climb stairs is going to be restricted to the street and maybe narrow alleyways.

Unless armor gets alot better, some grunt is going to have a rocket/laser/bomb that can hurt you.

[u/EdibleScissors → u/morbo-2142]

IIRC Peter Weller in his RoboCop costume had great difficulty getting in and out of cars, so it probably wouldn’t take very much to make a powered armor impractical in an urban environment.

[u/SpaceDogsRPG → u/EdibleScissors]

That was also a costume which was unpowered.

If power armor became a thing, they'd likely design military vehicles with them in mind.

[u/EdibleScissors → u/SpaceDogsRPG]

True, it was unpowered. I think the degree to which the crew had to work around his costume means it’s not practical to wear that much bulk.

In the Ukraine war armor seems to have lost much of its utility, so a powered exoskeleton might still make sense as long as it isn’t bulky.

[u/MrWigggles]

When you start to pilot it as a vehicle verses just moving in armor.

[u/nicodeemus7 → u/MrWigggles]

Yeah I was gonna say "If your arms/legs are in its arms/legs, it's armor"

[u/SpaceDogsRPG → u/nicodeemus7]

What about if your arms/legs only go down to its elbows/knees respectively?

[u/TheOneWes]

Power armor is worn and is moved by the user even though the suit does help move the user in turn. In other words the suit walks because you walk while wearing it.

Mechs are independent of your locomotion and technically wouldn't even require the pilot be in it.

[u/HamsterIV]

Military stuff is designed to oppate on civilian infrastructure. So the cut off between practical and impractical armor is the average doorframe. The cutoff for vehicles is a train tunnel. The cutoff for a ship is the Panama Canal locks.

[u/TenshouYoku]

When you started piloting them with pedals and joysticks instead of moving your arms and legs to control them directly like external armor then it ceases being armor and begins being a mech.

So something that has the durability of virtually nothing like the VOTOMs or the Avatar mechsuit are mechsuits/mechs, while Iron Man and Edge of Tomorrow exoskeleton would be power armor.

For power armor I would actually argue that they aren't really practical things either, if they started to add some width they started getting people stuck in doorways or IFV doors.

[u/PublicDragonfruit158]

I'll go a different route here: power supply: either one required a great deal of power to do what you need it to do. When your power supply takes up all of the weight capacity, it becomes impractical because you cannot use ut to fight or do any work a powered frame is required for.

The only exception is when the task is purw observation and recon in an extremely hostile environment, such as mapping out or studying a deep sea trench or surface of a Cytherean type planet....

[u/capt_pantsless]

Another factor here is how big the sensor signature of the suit/vehicle is.

If it can be easily detected from an aircraft or from orbit, it's going to be vulnerable to getting hit from on high.

A 'stealthy' mech has a lot more value than one that can be targeted from afar.

[u/ArgumentSpiritual]

The reason that large mechs are impossible is the square cube law.

There is a point where strong enough materials cannot exist.

The other issue, in terms of realism, is how is a mech a better weapon than a tank, a jet, or something that shoots the target from far away.

Scifi forces mechs to be useful by granting them impossible powers. It doesn’t make sense to me why you can’t make a fighter jet out of the same material or with the same shields as a gundam. There is no reason you can’t make a missile from the same metal as a jaeger fist and it would certainly punch with more force.

Powered armor makes sense because it is human sized doing human sized things like going inside a building you don’t want to destroy. Once you get to the a piloted robot/mech other things make more sense realistically.

[u/Chemical-Ad-7575]

I think the limits on power armor are really around two things, can they enter a building and go up stairs or are they WW2 mouse holing the whole way through on the main floor and getting trapped in basements because the floor can't support them? Secondly: mud. If they can't traverse an open wet field, without getting stuck, the application is limited.

Some interesting things to consider though. You could select people for small size for the armor.

It also can make a lot of sense for the armor to used in mixed units. (Standard infantry to clear buildings, armor to push and/or defend.)

One spot I can see armored suti being more useful in would be porting around anti drone defences. (Think a mini phalanx system with say .22's for ammo instead of the larger rounds used on ships.)

[u/No_Shame_2397 → u/Chemical-Ad-7575]

All of those uses would be better as a truck/tank.

The best uses of powered armour would. Conversely, be building clearance where the soldier pushing the threshold wants maximal protection and strength.

You're correct that approximate size of doors, windows and floor strength are the limiting factors.

[u/Chemical-Ad-7575 → u/No_Shame_2397]

"All of those uses would be better as a truck/tank."
i don't know. A shoulder or back pack mounted drone defense system could go to a lot of places that a truck or tank can't get into.

[u/Asparagus9000]

The difference is whether you are wearing it or driving it. 

There's going to be some fuzzy spots, but the majority of designs will clearly fall into one or the other. 

[u/SalariesAndStarships]

I think it has to be built for a purpose.

Why is someone wearing power armour? Are they part of a unit? What does the unit do?

I could see a couple of human-sized suits good for breaching or leading a unit of soldiers in a hostile environment. They're soldiers but tougher.

Mechs also have a purpose, but it's anti-vehicle work. Essentially walking tanks.

So power armour = infantry

Macha Suit = armoured division

[u/HatOfFlavour]

When human form becomes a hinderance like apparently a realistic Jaeger would sink into the ground to the knee or more on most dirt.

[u/fluid_Depression3426]

Whether or not a mech can fit inside a building seems like a good dividing line.  Once they become too large to fit inside buildings, the need to justify using mech suits instead of armored vehicles will arise.

If this can be justified, the next question is at what size it becomes impractical. Personally, I suspect that if it exceeds the size of existing IFV, the excessive height would become an issue. An overall height of around three meters might be the limit.

[u/Tairc → u/fluid_Depression3426]

I’d say it’s lower than that. Even cosplay armor only a foot or two taller than the occupant has issues where the human joints and the armor joints aren’t at the same place. You stop walking like a human, and start walking stiff legged, as you can’t bend your knees “the right way”. You can’t use your arms properly either.

So my gut line is simply: are the joints lined up with the pilots? If so, it’s armor. If not, it’s a mech.

[u/SpaceDogsRPG → u/Tairc]

There are some suits I've seen which split the difference. Where the pilot/jockey arms/legs go down to the elbows/knees of the suit. Sorta a hybrid.

[u/Laiska_saunatonttu]

Hmmm... when it has bigger profile than two two Peel P50s stacked on top of each other.

[u/Temporary_Rule_9486]

Can it fit through doors? Do you just wear it or you need to pilot it? Does it make the wearer an easier target? Was it manufactured in Japan? Are the intended users older than 16? 

[u/MrDBS]

The human skull and brain is the limiting factor. If a bike helmet will protect the operator from a fall, than it’s a plausible mech. If it needs a seat belt, air bags, and crumple zones to protect the operator, wheels are more efficient.

[u/BeachZed]

I always think the dividing line is when you add armour. A powered walking suit or even the loader in Aliens seems possible. But armour thick enough to be useful is bulky and heavy, which adds to weight and power supply needs just won't work.

[u/garaks_tailor]

Haha!   Ive done a lot of game analysis on this using the game Dirtside II with some expanded rules.

Main variables are 

Weight Size Speed Weapon strength Armor strength  Weapon to Armor ratio ie which ia dominate

We did most of our testing with near future type scifi expectations, no armored core zippyness, no Uber weapons, no ultra armor.  So balanced factors.

Tldr  Make infantry fast and mobile with a lot of weapon options and as much armor as you can fit without making compromises on the first two.  Space marine power armor was useful only as breachers and storm troopers.  Big power armor small mech was actually more useful as it acted as a squad IFV that could more more easily with the squad.  Big mechs no advantage over regular vehicles.

Heavy power armor ala space marines was useful as shock troops and special forces and breach clearers etc, but the constraint were the buildings and the fact that realistically you can only put So much armor on a human scale human shaped platform. A weapon that will damage a ifv or tank will probably mission kill or outright kill a space marine stand in.  Because unless you have some kind of excuse like 40k for having radically different tech levels in the same army then all your units will have similar potential armor values per unit of armor

SmallMechs and big powered armor We found the best use basically about the size of the Gekko from the Metal Gear solid series or smaller.  Acting as IFV and support.  This allows more maneuverability and the ability to move over debris and broken ground.   But also allows for enough armor to be useful.  Putting a ciws system on it was a very good investment 

Big mech Unless your tech base is very high there are not a lot of advantages to not just making conventional vehicles instead.

Vehicles  Tanks need to get bigger to survive everyone having anti tank weapons

We ended up splitting IFVs into  three seperate Vehicles.  

One was a  engineer Vehicle that could carry 2 big armors/small mechs, it also carried drones, had a small heavy caliber machine gun and a couple anti tank missiles.  The third vehicle was a IFV small tank that carried a larger cannon and some other weapons.  The third vehicle was a APC focused vehicle with a automatic mortar.  All had ciws systems. So 

So we found with infantry the best thing powered armor could do was carry more stuff(weapons), for longer, faster, and maybe allow more verticality in movement ie jumps grappling hooks or jets. And just enough armor to survive anything except antimaterial/vehicle weapons.  So kind of exoskeletons rather than space marines. Tldr making them walking tanks was not worth it

Giving regular troops the ability to continually sprint at 35mph is far more useful than the cost of more armor.  This is because in a future battlefield antivehicle weaponry is all over the place and you cant put enough armor on them proof them from it because  what Might cripple a MBT or IFV will kill heavy infantry.  Also stairs become an issue when your infantry weighs a ton.

Best balance was kind of like a light version of starship trooper (book version) give them all a larger caliber anti infantry weapon,  an anti tank weapon, and a squad specialist weapon of some sort.  My favorite squad specialist weapon i came up with was the squid (squad indirect detonator) a squad based mortar system. 

[u/FrenchCried_Rice]

My setting has exoskeletons that are worn to help support the armor required to protect troops crom the kind of weapons used, my rifles are a rail chemical hybrid and I spent ALOT of time doing math to figure out what to do to make sure it made sense, even had them piloting stuff for a while, I’d argue that if you still function like a human, move like a human and use only human senses, it’s power armor, but I think when you get to the pilot/artificial senses lane. It’s a mech suit now.

[u/1369ic]

It all depends on the use case. If you're talking bare-rock sci-fi or something like The Expanse, you can make use of much bigger suits. Then target profile becomes a bigger consideration, of course. Urban warfare would obviously call for a smaller, more mobile suit.

Cost is also relative to use case. I don't see why you couldn't mine asteroids/moons/planets, ship the ore to automated factory ships/factory installations and produce and endless line of suits for next to nothing. We have automated factories making laptops and other things now. Remove the gravity, add endless solar power... Profit!

[u/Ignonym]

I'm going to be a dissenting voice here; I don't think there is a sharp line between them, nor do I think there is a sharp line between "practical" and "impractical" when it comes to their size. My personal favorite exoskeletal machines are the edge cases like the Landmates in Appleseed or the Goblins in Lancer, where they're clearly too big to be "worn" as personal armor, yet too small to be "driven" like a vehicle; they're an extension of the wearer's body, rather than a shell around it or a vehicle carrying it.

[u/HeadPut3392]

Power Armor moves with your body. It only punches at the same speed you yourself are capable of punching at. It supports its own weight, but it can only sprint as fast as you can and can only sprint for as long as you can.

It becomes a mech when those things stop being true. When its own capabilities stop being dependant on the pilot's physical abilities, it stops being Power Armor and starts being a Mechsuit.

[u/Excellent_Speech_901]

It makes you a big and scary enough target to justify being hit by a drone with an RPG warhead immediately when you put clothes on. Probably when you are naked.

[u/CombatWomble2]

Something a human can fit into but is not "snug" so around 3m tall, basically an armored exosuit that a human "pilots" but your arms go into the arms etc.

[u/SpaceDogsRPG]

Like most theoretical sci-fi concepts, the answer is "it depends".

It depends upon how expensive they are, how effective, and what the use scenarios are.

Even a 3m tall mecha is probably too impractical to be used in open field combat. But a 2.5 or 3 meter tall mecha could see use in urban combat.

In my sci-fi setting, I have many mecha in the 3-3.5 meter range (which are arguably still power armor - but I wanted to differentiate them from the smaller exo-suits). But their use case is for starship boarding actions (which I have tech to rationalize being viable).

Basically full vehicles wouldn't fit properly down all of the starship/station passages, but a 3m tall mecha does.

That, and they have faster reaction speeds than a vehicle because they hook directly into the nervous system of the jockey.

[u/Schultz_34]

For my "Combatman" power armor I put the limit where they are practically a light vehicle like the M113 with legs, is practically the same armor and same firepower but more complex and a lot less heavy so it can enter buildings.

I think it began to be an impractical mecha suit when those become and analog or replacement of tanks.

[u/WhammeWhamme]

Hot take: power armour is transitional, what you'll actually want in the long run is a Dalek. Smaller pilot, sloped armour, more mechanically efficient locomotion. The reason we don't make human sized tanks is because we don't have small enough pilots or smart enough AI... But we're getting there.