Real life gundam

[JMvS]

Originally Posted by Engels

OK, nobody wants to talk about that, I see. I gotcha. So back to topic...

@JMvS I don't understand where you are trying to get at. I said that all armors are made of alloys, and you list to me series of materials that can be alloyed with something? Aren't you exactly proving my point? Then why you said "Ermm not so much"? When a person uses the term "alloy" I guess it doesn't mean automatically that he/she is saying metal alloys, unless it is explictly said so. If "alloy" = "metal alloy", then I guess we should not be using terms like "aluminium alloy", "titanium alloy", etc, we simply use anything else. In other words, why my words necessarily imply that I referred to metals? Seriously, I am not asking this as rethoric or such. I really wanna know about the seemingly semantical problem behind this...

My point is precisely semantic: an alloy is by definition metallic.


And at the same time they are categorized by their base metal, as those can have extremely different properties (you can't simply mix one part of iron and one part of copper and expect something with intermediate properties, it simply does not work this way).
So we have iron and steel alloys: where iron is the main ingredient, combined with varying small percentages of carbon, and with many many variations.
And similarly, copper based alloys, titanium based alloys, aluminum based alloys, etc...

It's not very easy to explain, but it's due to the way how metals "work". Basically, metallic materials, on the atomic level, are like the balls of a ball pool, glued by pooling their electrons together (which is why they conduce electricity), unlike non metallic materials where atoms are bonded by covalent bonds into molecules or molecular units (electrons are shared only between specific atoms).
Atoms can be piled randomly: it is called an amorphous state, in opposition to crystalline state; in crystals, the atoms are piled according to a lattice shape, where you can either replace atoms with similarly sized atoms, or fit smaller atoms in the gaps.
But of course, with the notorious exception of turbine fan blades, metallic objects are not made of a single crystal, but are polycrystalline, and size and shapes of crystals are important.

So by playing with sized of atoms and their chemical properties, alloys can be designed, together with metallurgical processes, to engineer crystal sizes, shapes, and associations.

Why is that? (again, not rethoric ).

Well armor have several requirements: it must hold together, be given the shape of the thing to be armored, thickness plays a role against armor piercing weapons, but of course how it is cumbersome or heavy is important when designing a vehicle (which is why we'll never see armored tanks with a 10m concrete armor, despite it being a quite effective protection).
Problem with aluminum is that for similar resistance to steel, it'd be much more cumbersome than steel (more volume), plus it has the problem of being heat weak.
Titanium is faring much better in term of heat and mechanical resistance, but it is much complex to work with (plus it's expensive).

And finally, do you agree that carbon nanotubes could be used as armors (or just to make artificial muscles -- or both) in mechas, or there is also some problem with this?

Possibly, but we have to overcome the many problems of production. But to use it as structural and armor material, the problem is the one common to most composite materials: bonding together the fibers.

[JMvS]

Originally Posted by Engels

But it is at least theorically possible to work with it for a mecha, right?

I suppose yes, but defining the mecha's combat doctrine would be most important in determining it's usefulness (would armor really be useful and not a hindrance).

What you mean? We can't produce carbon nanotubes right now?

Do we have any perspectives of surpassing this problem? Or it is as far as we know completely impossible?

Well, for now carbon nanotubes have a similar history to spider silk: known for a while as one of the strongest fiber existing, but hardly available for mass scale production and application.

Regarding the bonding problem, I think we are not even there yet, as scientist have been working on nothing but tiny strands. There's a long way to go before making long fibres or rigid objects out of it.

[reinloch]

The progress in smart weapons and drone delivery platforms and the attention being poured into this realm shines the direction of future warfare. Armor is on an ever losing race against weapons, so the focus today is on compact design, flying higher and faster, and electronic protection.

[4Tran]

Originally Posted by Engels

Can someone please expand this post, seeing as 4tran isn't here on ASuki anymore since last year? What exactly would be those 'superior alternative designs' in the emphazised part (by me)?

Wow, this is a real blast from the past, but I ain't dead yet .


Here's a thought experiment: think of a human body and compare it with what we would find useful for an industrial machine, and especially a manned one. Under such circumstances, why would we need such components as a head separate from the torso? Human beings do so for many reasons, but none of these reasons apply to machinery. In fact, why would machines even need heads in the first place?

Originally Posted by Engels

Also, the original post which prompted this answer was about how the construction of Mobile Suits in Gundam made sense in the scheme of that world, or, as the user himself pointed out, "colony repair craft > humanoid robots for war". Now how exactly a case can be made that even in space -- which I assume we have little experience with, in this manner at least -- this design would be certainly not useful?

Any likely space repair craft are going to resemble minisubs as much as anything else. Hence combat versions of such vehicles are basically going to be Balls. There'd be no need for legs and other useless peripherals. Moreover, it's a lot more likely that any military designs would do so from the ground-up; with dedicated combat machines with lots of thrusters.

Originally Posted by Engels

And third, what similarity exactly does a legged drivetrain have with a humanoid robot aside from the legs, which are themselves very different in concept, design and purpose? Isn't this comparison a little far-fetched?

A legged drivetrain would be the legs of a vehicle, its power system and its engine. The comparison here is between the efficiency and complexity of such a system with its alternatives like tracks or wheels. For sake of simplicity, I tend to leave the engine out of the equation, and assume that a tracked vehicle would have the same engine as a legged one.

[Rising Dragon]

... no offense intended, 4Tran, but where the heck did you come from?

[4Tran]

Originally Posted by Engels

Not dead, I would say. Just taking another steps in life maybe. Anyway I am glad that you're back, I always appreciate your posts but never had the chance to talk to you.

Well, thank you. I'm off of Gundam for the time being, but I always enjoy discussing this kind of technology.

Originally Posted by Engels

Yes, they won't need any of this stuff, but I wasn't thinking about mechas who have 'heads' in the first place (it may be my fault to not have said this earlier, but I guess you wouldn't have to exclude that type of mechas with such arguments either ). I was thinking of something more along the lines of 2009's Avatar mechas -- those don't have 'heads', only the pilot cabine's.

That would certainly make more sense, but do note that the Avatar AMP suits weren't meant to be specialized military vehicles - they simply used what they had and improvised them into weapons. Moreover, they weren't meant to take on a technologically advanced enemy, and so many of their standard weaknesses compared to conventional vehicles aren't that important.

Originally Posted by Engels

But even in the case of Gundam (if we're about to talk of incredible unrealistic mecha), the head has a function; IIRC, it's where the MS 'camera' is located.

That's more an excuse for having a human-style head than a real reason though. It's easy enough to mount cameras all over the body, and indeed that's what even a lot of mobile suits do. Funnily enough, the only Gundam show to have a justifiable reason for the heads is G Gundam; and that's because it's for the purpose of keeping score.

Originally Posted by Engels

I guess I am confused over what "colony repair craft" defines, so you're welcome to try to enlighten me. I was thinking about something along the lines of mechas -- inside the colonies -- assisting humans to construct stuff and occupying the same niche of your current 'industrial' machines. That is completely off track, isn't it? (I addmit that I don't know much about UC Gundam)

As a proof of this, I didn't even had any clue of what you meant by "Balls" until I searched and found this.

Refer to my example of mini-submarines. While the mediums the two types of vehicles operate in, undersea and space, are different, they still share similar environmental challenges. Thus the design for one will be similar to the other; especially seeing as they perform similar tasks. The mini-subs in The Abyss would be very similar to what space versions of repair craft would look like. Hence the Balls.

Originally Posted by Engels

I guess I simply misundrestood what you meant by "legged drivetrain" then. Sorry. That said, while I agree that mechas would be infinitely more complex than wheeled or tracked machines (that doesn't seem to be a problem to me, however), I don't know about any 'inefficiency' it would have compared to them, so again you are invited to shred some light on that matter as well.

Efficiency is mostly a matter of what percentage of the engine's power will go directly towards propelling the vehicle. Tracked and wheeled vehicles are relatively efficient because most of the energy is dedicated to moving forward, while legged vehicles have a lot of wasted motion (lifting the leg, etc.). Moreover, the more complicated design of legged movement means that a smaller percentage of the engine's output even gets to the legs in the first place.

Logically speaking, the longer the legs are, the less efficient they are going to be as well. And then we get into matters of stability and so forth. That's why if there are going to be any combat mecha at all, they're far more likely to be quadrupeds since they can use shorter legs and will have greater stability.

[Vsin]

To be honest, I think the power requirements of a walker aren't actually that much larger (if larger) than those of a wheeled/treaded/whatnot vehicle. Yes said vehicle is putting all that power to move forward, but it has the added resistance factor of the weight of the entire vehicle the grand majority of the time. In the case of a walker, half the legs (however many you end up with) do nothing but move the weight of the leg itself, while the other half can be locked in place (mechanically or something) and consume almost no power. There is a brief moment where the legs do need to lift the vehicle, but for the most part I can't see it consuming too much power.

Now that I've said that, the Biped walker would only be practical if we could get the balancing system to work nicely. Even then, you need only look at humans to realize that being a biped would only be practical if the unit is small; too large and you need a complicated balancing system (eg: to "step back" when you get knocked back) just so it doesn't repeatedly fail.

On a sidenote, I think Mecha would be more practical than Power Armor. Why? When it comes to the drive system, the full Mecha would not have the space constraint of sticking human body parts next to/inside the drive systems. As such, despite the increased size, I'm sure that it would work out much better for drive efficiency.

[4Tran]

Originally Posted by Vsin

To be honest, I think the power requirements of a walker aren't actually that much larger (if larger) than those of a wheeled/treaded/whatnot vehicle. Yes said vehicle is putting all that power to move forward, but it has the added resistance factor of the weight of the entire vehicle the grand majority of the time.

It's not resistance; it's traction.

Originally Posted by Vsin

In the case of a walker, half the legs (however many you end up with) do nothing but move the weight of the leg itself, while the other half can be locked in place (mechanically or something) and consume almost no power. There is a brief moment where the legs do need to lift the vehicle, but for the most part I can't see it consuming too much power.

For a very rough comparison, look at how much energy it takes to walk 20km, and compare it to how much is required to bicycle that same distance. Wheels are ridiculously efficient compared to legs.

Originally Posted by Vsin

Now that I've said that, the Biped walker would only be practical if we could get the balancing system to work nicely. Even then, you need only look at humans to realize that being a biped would only be practical if the unit is small; too large and you need a complicated balancing system (eg: to "step back" when you get knocked back) just so it doesn't repeatedly fail.

True, but I see that more as a technological challenge. Basically, it's one that can be overcome given the proper equipment. It'll probably be always more complicated than it would be practical, but it's still less of a limit than the other numerous structural challenges.

Originally Posted by Vsin

On a sidenote, I think Mecha would be more practical than Power Armor. Why? When it comes to the drive system, the full Mecha would not have the space constraint of sticking human body parts next to/inside the drive systems. As such, despite the increased size, I'm sure that it would work out much better for drive efficiency.

True, but then we run into problems with size. Height is the very antithesis of a good military vehicle, so anything over 3m or so is just going to be a giant target.

Furthermore, you shouldn't think of Power Armor as a separate vehicle. It's really just the powered version of a self-contained suit of armor. They're not really meant to go very fast; just to give better armor and heavier weapons to regular infantry.

[4Tran]

Originally Posted by Engels

I agree. But it shows that this particular impracticality can be overcomed, and we can still have a bipedal and relatively bad*ss GIANT (4 meters) mecha. Now, for the emphazised part, what "standard weakeness" would be that and why they don't matter?

The standard weaknesses that don't apply to the AMP suits are that they don't have to compete with conventional vehicles and they don't expect anyone to shoot at them with AT weapons. The AMP suits would fare extremely poorly against a technological opponents with their weak armor, poor armament, and all. Against the local fauna and natives, this is of much less concern.

Originally Posted by Engels

Could you give me some examples (I have only watched the Wing series, and I don't recall MSs there having cameras not on the head)? I wanna know how those Mobile Suits work and do look like.

Practically all of the mobile suits from Zeta Gundam on have a sensor system called a "panoramic monitor". What that does is to project the surrounding environment onto the interior of the cockpit; creating the illusion that the mobile suit is invisible around the pilot. Obviously, this would require cameras covering the entire body, with the head housing the primary sensors. It's also heavily suggested in just about all mobile suits in other Gundam shows use the head = primary sensors/body = secondary sensors setup as we see heads get destroyed fairly often.

Originally Posted by Engels

Fine, I will look up minisubs on Wiki and elsewhere. But I suppose that in the sense of 'industrial purpose' I proposed, to use bipedal mecha in some types of activity wouldn't be a stupid move; it would perhaps work, right? Just to know your opinion about this.

In space, legs wouldn't be very useful. Small objects wouldn't exert enough gravity to justify walking on them, and the larger man-made objects are likely to rotate - inertia would throw any objects on the outside skin away from the object. Bipedal walkers might be useful on larger asteroids and moons, but I'm not sure how likely that would be. I imagine that if we were to ever develop this industrial bipeds, they'd be limited to stuff like the loader in Aliens (do we have enough James Cameron references yet ).

Originally Posted by Engels

Maybe you could explain to me that stability argument, because I never understood it, despite being more than overused in those types of discussions. For example, the article "Why Giant Mecha Robots are Stupid" on TechBlog says:


[...]being bipedal means that any rest state requires a change in position–you can’t sleep standing up. Thus, if a bipedal mecha were to lose power–or just be turned off–it would at best be left in a vulnerable state that was easy to push over[...]

Well, not necessarily. It is certainly possible to make stable bipedal structures. We have toys like that. The issue is that they don't seem too much like a human body, and also don't have much agility in walking. Besides, I don't believe that bipedism in itself is the problem, but the human erect walking. A Macross-like avian feet system, like those used in the intermediary configuration of the combat units, or the Star Wars AT-ST's, are bipedal, but very stable.

Bipedism alone is not the main hurdle-- properly considered, there are even certain advantages to it (this very article lays out some of them); it tends to fall apart only when it is conflated with the anthromorphic factor.

Stability is a question when it comes to movement over bad terrain and discharging weapons (recoil, etc.) as well as standing still. For these concerns, a high ground pressure and a high center of gravity are big detriments. Hence an ideal bipedal walker would have short stumpy legs with huge feet with the torso close to the ground (hello UrbanMech!). However, that would sort of defeat the purpose of going with two legs to begin with. It'd be better to go with a quadruped and leave it at that.

[4Tran]

Originally Posted by Engels

I agree overall, but what are AT weapons? And, since the AMP suits weren't meant originally as weapons, to what purpose were they created (I don't remember the movie anywhere mentioning any of this)? I suppose that it was for assisting humans in industrial work, but would it work according to what you say in the third quote of this post?

Oh, and BTW, would those flimsy feet work too? Would they support the pressure of the body?

In terms of design, the AMP suits aren't too bad. The key here is that it's a very light vehicle (1700kg), so it's in the same class of vehicle as the Wiesel or Humvee. The roles that these kinds of vehicles are used in tend to downplay most of the disadvantages of combat mecha.

As for the AMP suits in Avatar, I think that they could be seen in several scenes loading/unloading equipment. Perusing the official website, it looks like they are specialized military designs, but they're still one of the more authentic depictions I've come across.

Originally Posted by Engels

Interesting. I think that I might see them working in the actual anime (one of them, to be more precise) . But is that, as a realistic sci-fi notion, plausible?

There's nothing too implausible about it. All they would really have to do is coat the cockpit in video panels and use software to display all the images properly. However, it seems to me to be a very roundabout way of doing things. It would be a lot simpler to project the exterior view onto the inside of the pilot's head, and move that view by tracking the head movement. That kind of application probably isn't too far from our current capabilities. Of course, it doesn't look as good on screen, but there you go.

Originally Posted by Engels

You mean, in a space station (for example)?

Yup; that and the ever-popular O'Neill colonies.

Originally Posted by Engels

Why?

Because walkers would only make sense on objects with very rough terrain, like the asteroid in Armageddon. Anywhere else and you'd probably still be a lot better off with tracked vehicles. Moreover, the smaller moons and other bodies will have very little gravity, and a walker will have to be controlled very carefully lest they put themselves into escape velocity. For example, escape velocity on Phobos is around 12m/s, and Deimos is about half that.

Originally Posted by Engels

Hahaha, what is surprising is that, for a guy who is famous for directing goofy sci-fi flicks, some of his ideas are surprisingly on the spot.

I don't really find it that surprising at all. Cameron grew up on the science fiction novels of the '50s-'70s - the era of the most emphasis on the science part of the phrase. It makes a lot of sense that he would try to incorporate real science into his films as well.

Originally Posted by Engels

So even a 4 meter mecha like the AMP suit could not stand still? And you don't think there's any problem with the human erect walking-- what about my examples then?

Don't get me wrong, I'm not trying to state that there's necessarily anything wrong with the concept of bipedal motion. I'm simply claiming that other techniques would be better. The main issues with bipeds is that it's a lot easier for it to fall down, slip or get stuck in mud, and that they have a very high center of gravity.

There shouldn't be any problems with an AMP suit standing up, but it would also be a lot easier to tip one over. Similarly, it's a lot easier for a human to trip than something like a lion. Bipedalism serves two big advantages for humans: it gives us a very high sight line and it allows us to move about and simultaneously free our forearms for carrying things or using tools. Neither of these advantages translate well to military applications.

As for your examples, the GERWALK mode in Macross' variable fighters are used as an alternate flight and landing mode. They aren't used for walking around in-universe, and they'd probably be very ungainly in the attempt to do so. In Return of the Jedi, AT-STs seem fairly easy to knock over so I can't see them as very good examples.

For my money, one of the better depictions of how mecha might work is the Heavy Gear universe. In that scenario, the mecha are meant to serve in an intermediate role between infantry and tanks. The mecha are treated as reasonably decent combat machines rather than the all-conquering gods of the battlefield seen in some anime (and Battletech ). Like other military units, they can be extremely effective, but in a slugfest against tanks, they get slaughtered.

[fizzmaister]

AT weapons are anti-tank weapons. High explosive rounds, kinetic energy penetraters and the like.

It's not that bipedal suits need to constantly move to remain upright, they constantly need to re-balance because bipedal designs are inherently unstable. You need a minimum of three points of contact for something to be stable. As an example, find a four-legged chair and lean back on it until you're balancing on the back two legs. If you get good at it, you can balance for a few seconds, but you need to constantly shift your weight to keep from falling over. Now if you take a 3 legged stool, you can sit on it normally.

Legged vehicles are inferior in almost all regards to wheeled or tracked vehicles. The only advantage I can see is that legged vehicles might be able to step up onto ledges that would be impractical for other kinds of vehicles. Unfortunately, that is more than offset by legged vehicles higher weight to contact area (more pressure on the ground), lower speed, and greater target area.

[4Tran]

Originally Posted by Engels

You mean that this is an advantage?

It is; but mostly in the sense that the AMP is a light support vehicle which mecha would be far more suitable for rather than heavy combat vehicles. The biggest difference is that they aren't expected to stand up to tanks.

Originally Posted by Engels

So you think it is one of the more plausible/realistic mecha ever?

For Hollywood, absolutely. I can only think of the Aliens loader as being better. The AMP suits would be far worse if they were meant for an opponent who could effectively shoot at them. In comparison, the Matrix Revolutions APUs are among the worst because they provide no protection for their pilots.

Even compared to anime mecha, the AMP suits aren't that bad.

Originally Posted by Engels

Wait, what's plausible: the anime version of that application, or the 'non-roundabout' way you described?

Both are plausible, the panoramic monitor method would just mean covering the inside of the cockpit with a bunch of LCD panel-equivalents. The version I described is far more likely as more and more displays/information/sights are integrated into modern helmets as we speak.

By the way, if you've ever watched Macross Plus, the YF-19 shows off the same technology when Dyson gets his first flight.

Originally Posted by Engels

And, in any case, if that's possible within our 'current' science, does that mean that Zeta Gundam actually gave birth to a useful idea that might be used in pratice (much like the Balls, say)?

Sure; although I don't think that Zeta Gundam was the first place the idea showed up. I seem to recall some books from the '60s and '70s that had similar ideas.

Originally Posted by Engels

What about the "Stanford torus"-type colonies (those used in 2001: A Space Odyssey, and the Wing series in Gundam)? Would that work different in one of them?

It'd be the same. The only way it would be different is if the structure is so gigantic that it would generate enough gravity (in which case it'd be over a thousand kilometers long), or if it generates some sort of artificial gravity on its skin.

Originally Posted by Engels

So that would be only the only case in which mecha would be absolutely necessary, and not just cool, reasonably workable, or simply neutral?

There's almost no case where mecha would be absolutely necessary.

Originally Posted by Engels

Would it be possible to have a mecha battle on the moon?

Sure. That's probably one of the better places they can operate in. I still don't think that it'd be a very good idea though.

[4Tran]

Originally Posted by Engels

Hahaha, don't even say that. They didn't had even protection glasses! The enemy machines could just throw some blinding flash that the entire army would be rendered useless!

Or use tear gas . Open cockpits are just awful ideas in intense combat situations.

Originally Posted by Engels

Could you point out to me 3 examples of anime mecha that are better than the AMP then, please?

There's the VOTOMs in Votoms, the destroids in SDF Macross, and the Labors in Patlabor. I admit that this isn't a very long list. A lot of it is dependent on what the mecha is designed to face in combat and how they are employed.

Originally Posted by Engels

Unfourtanely, I have watched only the first season of Macross. But I plan to finish it someday, and maybe, just maybe, go see another series then.

You should really give Macross Plus a shot. The movie version is probably the better one, and it's only about an hour and a half long.

Originally Posted by Engels

But the Balls *concept* is original to Gundam, right? Or not even that?

The concept of an EVA vehicle with manipulator arms has been around since the '20s and '30s. The only new thing that the Balls have are those big guns mounted on top.

Originally Posted by Engels

What you mean, "on its skin"?

I can mostly recall this in the Macross shows: when Valkyries and destroids fight against enemy mecha, they can stand on the outside of space craft as if they were standing on the ground. This presumably happens because the space craft exert an artificial gravity field on the skin.

Originally Posted by Engels

So we could use tracked/wheeled vehicles on 'very rough terrain' like the asteroid in Armageddon?

Not well. That's why this is one of the few environments where legs might be a good idea. The problem is that most larger asteroids are going to be fairly smooth.

Originally Posted by Engels

Why?

Because you'd have to find an environment where mecha can operate fairly well but tracks and wheels wouldn't work, and it still has to be someplace that's still worth fighting over - most inaccessible places are worthless. This is an extremely rare combination; which is why mecha are so very unlikely. On top of that, mecha would still have to fulfill a niche that can't be satisfied by other weapons and systems.

Originally Posted by Engels

You say that because 'violence is bad', or because of some technical difficulty?

It's because mecha would still get pasted by tanks.

[fizzmaister]

OK, I am still confused, so let me try to get this straight: you're saying that while mecha on small objects would be just not 'useful', i.e., impratical, in larger ones they would be simply outright impossible to work with (due to rotation, inertia, etc.,)?

No. A small asteroid won't have enough gravity to keep the mech on the surface. A very large asteroid might have enough gravity to hold it, but it might also have enough spin to launch the mech clear of the asteroid. You would need something with a large mass for a sufficient gravitational field, and slow enough spin to keep things from flying off. The only things that really fit this are planets and moons (possibly super-massive ships, or ships with artificial gravity of the star trek kind, not rotational habitation module artificial gravity).

About the moon, if a lunar rover could navigate the moon, a proper tracked vehicle should be able to as well.

[4Tran]

Originally Posted by Engels

And that would be a useful addition?

Only if you absolutely have to. A non-dedicated military vehicle just isn't going to have the features that make the dedicated versions dangerous, so it's a bad idea otherwise. Moreover, the only reason the Ball even works is because the gun it has doesn't have any recoil: otherwise, a weapon firing from so far off axis would wreak havoc on the firer.

Originally Posted by Engels

But we can't be sure because we never tried it, right?

It's more that there are very few environments where it's worthwhile to begin with. Generally, battles are fought because they are in places that are easy to traverse.

Originally Posted by Engels

And the moon is one of those places?

Nah, the moon is total tank country. Silhouettes are so easy to pick out from a great distance that anything that isn't as low to the ground as possible is just a target.

Originally Posted by Engels

I see. That seems to be always the point at issue. Damn tanks!

Yeah, that's pretty much always the case. Tanks are simply too good at doing what mecha are generally depicted to do.

Originally Posted by fizzmaister

No. A small asteroid won't have enough gravity to keep the mech on the surface. A very large asteroid might have enough gravity to hold it, but it might also have enough spin to launch the mech clear of the asteroid. You would need something with a large mass for a sufficient gravitational field, and slow enough spin to keep things from flying off. The only things that really fit this are planets and moons (possibly super-massive ships, or ships with artificial gravity of the star trek kind, not rotational habitation module artificial gravity).

Precisely. Macross ships are one of the few that display that kind of artificial gravity.

[4Tran]

Originally Posted by Engels

But this only applies to mechas, right (and keep in mind that here we are talking about an Avatar-like, 4-meter mecha)? If yes, why? If not, could we buy anything at all in space station/colony?

The point address the very principle of walking on the outside of space structures. It doesn't really matter how big they are, it's just not a very good idea under any realistic circumstance. If we were to build vehicles to move near colonies and the such, then we would use legless designs.

Originally Posted by Engels

I guess I misundertood your comment then because I was thinking about a mecha-only battle, without tanks or any other modern weapons, for that matter.

Whenever we discuss the practicality of a weapons platform, the context of existing and competing designs have to be taken into account. Even if we were to eliminate all competition to only mecha designs, quadrupeds like tanks with legs would still be superior to bipedal mecha on account of their form factor.

Originally Posted by Engels

BTW, 4tran, in this post, you say that: "Actually, we don't. For a rudimentary legged drivetrain, one only needs around a megawatt of power (depending on the mass of the mecha). This kind of power can be readily found on modern tanks and the like. If this is insufficient power, aircraft engines can be adapted for use - these are generally capable of much greater output than their land equivalents. The main problems that we have with building mecha (beside their practicality) is with the drivetrain and control systems; these are some of the same issues that we have with building human-form robots as well."

My point here was that in terms of sheer power requirements, it would be possible to build bipedal walkers. However it doesn't say anything about the practicality of such an idea, nor does it take into account any other technological limitations.

Originally Posted by Engels

But you also said in this other one that: "That's a great site . If you think about the different attributes and applications of combat vehicles, bipedal mecha fare poorly in pretty much all of them. There are plenty that we haven't touched on yet like fuel consumption, internal stowage, range, and so on. It would take a long time to list them all.".

This statement was to address both the techololgical limitations and practicality of the idea (i.e. that there are tons of problems).

Originally Posted by Engels

As for what concerns a mecha's power supply, I suppose that you don't agree in this particular with said text, given this first post, right? Just a bug.

Not really; the amount of power required to move a legged walker is a lot more than that required for a wheeled or tracked vehicle. This problem hasn't gone away. It's possible within our current and foreseeable technology to power such a vehicle, but it'll still have a very poor fuel economy and low top speed.

[4Tran]

Originally Posted by Engels

But in what specific situation would the bipdedal mecha be 'useless'? We couldn't get it inside the colony? We could not use use it to defend the colony from enemy attack in a war? What? (I am really ignorant)

Personally, I'd think that any combat in the vicinity of a space colony would be restricted to the outside. The interior is overly vulnerable to damage, and if an attacker has managed to penetrate that far, it's probably lights out for the defender anyways.

Originally Posted by Engels

The issue is that I asked this having in mind certain situations that I am still about to write in my fanfic. Those situations involves only bipedal mechas, with no room for other models. I was thus veryfing if those scenarios were plausible.

If you're planning to use this information for a fanfic, then you've got a lot more freedom to play around with the ideas. First off, most readers are going to care a lot more about fun than plausibility. This would be especially true if you don't overemphasize the mechanics: it'd be better to leave them as background notes for your own reference, and only mention them as needed. Just go with what seems natural, and you should be fine.

If you're going for battles with just mecha, there's nothing wrong with that; and it neatly sidesteps most of the problems that they have with other vehicles. On a personal note, I mostly only mind it when the work tries to emphasize how mecha are much better than tanks.

Originally Posted by Engels

Yeah, but I suppose that statements like "Some of these mechas would require megawatts just to move. What kind of portable power plant can provide that much power in a package small enough to fit in a mecha without weighing so much as to destroy the knee joints?" go directly against your words, right?

It does, and it's precisely what my argument was meant to counter. Most of this objection is based on technological challenges, and we can (almost) always overcome technological challenges given time. My own objections are always a case of comparing mecha to other kinds of vechicles and platforms, and more advanced technology isn't really the answer there.

Originally Posted by Engels

And what is top speed by the way? (I couldn't find it in short notice on Wiki )

Given equal power generation, if legged drivetrain can generate 50% of the efficiency of a tracked one, then the mecha will have a top speed of 50% of what an equivalently massed tank can. Obviously, this is subject to tons of other criteria, but it's a good starting point. And you can tweak the numbers however you like.

Oh, by the way, I stated earlier that it's possible for our current technology to power a mecha (of say, around 50 tons). That's still true, but I should add that it's well beyond our ability to build a bipedal mecha that can travel at any reasonable speed for a long time to come.

[Engels]

Originally Posted by 4Tran

I should add that it's well beyond our ability to build a bipedal mecha that can travel at any reasonable speed for a long time to come.

That still rings true?

[LoweGear]

Speaking of Real Life Gundams:

YouTube

https://youtu.be/5J3nq7PjpD0

Sorry; dynamic content not loaded. Reload?

That moving Gundam statue they're building at Yokohama is progressing nicely.

[B214]

I think the latest update on this is the Gundam can move already. Albeit slow.