Bipedal combat robot: useful when?

Factual Questions
1

We see many cartoons and movies where some of the protagonists fight from GTLRs. Sometimes these can fly, and sometimes they have other capabilities.

I can easily imagine uses for small robots with any number of legs, all the way down to insect size. Larger robots would not do too badly with at least three legs for stability, and more to spread their weight.

For large robots, it seems to me that the combination of size and small number of support points would be a huge disadvantage: roads and any surface less strong that solid granite bedrocl would crumble under their weight.

My theory, then, is that the GTLRs are mostly actually used for psychological reasons: to impress and encourage allies, and intimidate enemies.

The exception mught be for specialised combat against individual large monsters, but even then, that would have a large psychological component. If the Navy, Air Forces, and Army could vanquish the monster, they would; only when the regular forces prove ineffective is the GTLR team called in.

The GTLR itself, I suspect, would be tailored to the psychology of the monster it is meant to fight, and is essentially a psychological tool as much as a physiucal combatant: a tool to convince the monster to cease ravaging the Metropolis and go away.

So…

Is there any tactical situation in which a Giant Two-Legged Robot (GTLR) would actually be an advantage?

2

So… we can step away from reality for a moment and visit the universes of sci-fi like Battletech, Heavy Gear, and while we’re at it, I’ll throw in Mobile Suit Gundam and its myriad of descendants (you could say they started it all, really).

FASA’s Battletech posited that there were many advantages to piloting a “GTLR”, to use the OP’s term. The most important of which, in terms of gameplay, was compartmentalization. Battlemechs are 25 feet feet tall, and the operator rides in the robot’s head - far away from the nuclear reactor and all that nasty radiation. Lose an arm or leg, or suffer a breach to the reactor, and the pilot and his machine will still be able to fight on. A tank crew, OTOH, was not likely to survive a direct hit to an important part of their vehicle. While not as realistic have it could have been, there was also the element of physical combat - you wouldn’t want to be on the business end when a 70-ton monstrosity uproots a nearby tree and decides to break it over your crew compartment!

Heavy Gear took a (slightly?) more pragmatic approach. Gears are smaller and more nimble than tanks, and their flexibility allowed them to do sneaky things that a human soldier could, such as take cover from enemy fire, cooperate physically, and rapidly switch weapons (and thus also tactics) to deal with difficult foes. The designers made it pretty clear, however, that in a toe-to-toe slugfest, even the biggest, ugliest Gear was no match for the armour and weapons payload of a main battle tank.

Then there’s Mobile Suit Gundam… on the “realism” scale, Gundam is probably the most far-fetched, with robots that can fly, wield lightsabers (they call them “beam sabers”), and some of which are even controlled less by joysticks and levers than by their psychically-sensitive pilots (the “Newtypes”). The mobile suite escalation between the Federation (Earth) and Neo-Zion (off-world colonist) forces begins when the Zionists introduce their first suits, which are more manueverable in the depths of space than the spaceships used by the Federation. There is a huge leap here in terms of believability (I’m not even going to get into Gundanium and Monivsky Particles), but I don’t really buy it. If you’re at short enough range that your opponent can see you, extra manueverability will not buy you much if he tries to slice you in half with a laser.

3

In an age of ranged weapons, the “Giant” part of GTLR is a real liability. Heavy Gear got it right in making the robots small enough to take cover and not be the biggest target in the area.

To me, space/ zero g is the only place where anthropomorphic vehicles might have an advantage. After all, there’s no need for streamlining or wings, wheels, or treads. So a man-shaped suit could allow the pilot to “Swim” through space with thrusters to allow three-axis maneuvering.

4

The short answer is, when SkyNet decides it needs them. :stuck_out_tongue:

I have to say, when Hogarth realizes that the friendly and grateful GTLR in Iron Giant is his to do with as he pleases, part of me was a little envious…

5

I beleive in the design of armoured vehicles, height is almost always considered a DISADVANTAGE as the lower the profile, the less of a target you present. So I’d say yes, they may look v. cool, but giant humanoid robots are militarily pointless.

Giant humanoid robots that can transform into trucks, car, etc. on the other hand…

6

I think the best argument I’ve seen (mind you, I’m not saying it’s a very good one) is that we’re used to walking around on two legs, so we could (in principle) control a GTLR in the same way we’re accustomed to controlling our own legs. So you either put the pilot in some sort of harness that lets him move his legs, and put sensors on his joints, or you have some sort of direct neural interface, and either way, to move the mech, the pilot just walks. This logic is best, I think for the exoskeleton category of mech, which can do all the things a human can, like walking into buildings (and leave the building standing in the process).

7

For climbing and rocky terrain, two legs is good. Four would be good too. Six even better. Howsabout 2 legs and four arms?

8

Heh, Robot Jox!. Setting aside the massive reconstruction and wear&tear these things would have, honestly, the only use I’d see for it would be for PR. Or humanitarian missions, such as clearing people out of a Chernobyl-style disaster, for example.

9

The US military is researching exoskeletons for combat use. The first generation, whenever that comes around, will enhance the wearer’s strength, speed, jumping ability, and carrying capacity. I’ve seen articles about the early prototypes, and so far they do increase the wearer’s strength quite a bit. The major problem right now is in developing a portable power source; current prototypes are either wired into a stationary source or only run for a few minutes.

10

If you could get down to a man-sized lethal force delivery robot you could argue that two legs might simply be cheaper, lighter or smaller than four.
The Army would be ALL OVER using midget-sized bipedal robots if you could get them to move like a grown man and deliver automatic weapons fire, or be used to suicide bomb hardened targets with a dozen pounds of high-quality explosive.
No reason to get obsessed with battle mechs that can flatten a city block just by falling on it…
Certainly by the time your lethal force delivery robot is the size of a tank, two legs won’t make a whole lot of sense. I could see outfitting an Abrams-sized tracked tank with four or more AUXILLARY legs for added “getting unstuck” capability.
What I’m curious about is whether there would be any reason to take a tank-shaped vehicle and make its primary locomotion method legs rather than tracks. I can’t really think of one on most terrain.

11

robot jox. Neat, neat film.
Three kinds of bizarre, too.
If we had UNMANNED giant robots, the biggest advantage from the military’s perspective would be no human casualties when we lost a robot.
The US military positively DESPISES combat deaths, as each one is worth several million dollars in bad PR.

12

One advantage that a bipedal robot would have is redundancy. If a tank blows a track in battle, it is pretty much screwed. However, if a humanoid robot lost a leg, it might be able to limp/drag itself to safety.

A tank cannot alter its own profile- if it is 10’ tall, its never gonna make itself shorter than 10’ tall. However, a bipedal robot could theoretically kneel, lean, or fire by poking an arm around a corner, etc, things a conventional tank could not do. This could increase its survivability. There are also many places tanks cannot go- dense jungles, mountanous areas, etc that a legged robot might be better suited to traverse.

If bipedal robots were limber enough to mimic human motions, such as putting themselves in a prone position, or manipulating objects with their hands. As a fan of the old FASA Battletech board game, mechs were extremely versatile. They could endure enormous amounts of punishment and keep on ticking (with some lucky dice rolls, anyway).

13

Giant robots (at least those with any decent armor) are going to have some considerable problems with their weight to surface area ratio, negating any supposed mobility advantages.

14

That article leaves out some important things about the Hardiman project.

Only one arm ever worked.
The legs never worked.
The other arm had no lifting capacity.
Attempting to get the suit to move resulted in sprains, fractures etc.

Back To The OP

No. We’ve had this discussion before.

A huge robot on two legs? It will sink into the ground. You’d have to cover the battlefield in steel reinforced concrete. This problem becomes much worse if the thing runs.

A huge robot= a huge target. Laying down will not help. This simply changes things from a huge standing target to a huge prone target.

How much would this thing weigh? How much fuel do you need to move all that weight? You wind up with massive fuel tanks, which explode when hit, literally tons of batteries (what happens to massive amounts of sulfuric acid when hit by missiles, shells etc? OTTOMH I’m not sure. But, I am sure it would be rather destructive to the robot)

What happens when a leg is incapacitated? A hopping or limping giant robot is huge and slow moving target. A legless giant robot is a huge and stationary target.

These things would need serious armor. If such armor were developed, it would be much better to use it on tanks and other vehicles.

IMO An effective combat robot would be no larger than human sized, and possibly much smaller. They would have six or more legs. They would have no arms, just weapons mounted on swivels.

Six legs enables them to be fast, stable, and not sink into solid ground.

Small size reduces cost, makes a much stronger unit, and is a much smaller target.

Tiny bug bots could carry cameras etc and provide reconaisance. Bigger bug bots could be loaded with explosives and function as walking mines. The man-sized bugs would function as infantry, able to go wherever a human can.

15

You might as well skip to nanobots and have them turn the enemy into grey ooze. Horrific.

16

For large vehichles, the main detemination of what terain you can cover is how much pressure you apply to the ground. A tracked vehicle spreads its weight out over a much larger area than a walking vehicle, and so has much less ground pressure. A giant walking robot wouldn’t be able to venture from firm ground; it would become mired in mud or sand that a tank would drive through easily.

Giant walking robots also have the disadvantage of being much more complex, and therefore more expensive, less reliable, and harder to repair. A tank has a simple internal mechanical transmission which just needs to couple motor torque to two output shafts. The tracks have a lot of moving parts, but they’re easily repaired in the field; if a tank throws a track or loses a road wheel, the crew can repair it themselves. A disabled tank can be towed off the battlefield by another tank, or a specialized tow vehicle. A proper bipedal walking robot needs at least 6 powered joints in each leg, plus waist/torso joints. Each of those joints is a much more complex mechanism than the tank’s transmission, needing to output large amounts of torque, reverse direction several times a second, and be fairly precisely controlled for position in speed. A single broken shaft, blown motor, or bad encoder and your bipedal mech is disabled. And a damaged mech can’t be repaired in the field, and can’t be towed; you need a crane and a flatbed truck to get it back to the repair shop. So you’ve got a machine which costs an order of magnitude more complex than a tank, which will be useable in the battlefield less often due to maintinence requirements, which can’t go everywhere a tank can, and which is easier for the enemy to disable. Man-sized autonomous combat robots might be useful someday, but I don’t expect to ever see bipedal mechs fielded by any military force.

17

::nods ::
You folks have pretty much come to the same conclusion as me.

Obviously the GTLRs are a pricey throw-away propaganda exercise dressed up as combat gear. :slight_smile:

Now, cockroach-sized scuttler bots, on the other hand…

18

A RSTLR (Reasonably Sized Two Legged Robot) might have some application as a sort of “Walking Forklift”, something used for construction type uses, carrying around and assembling large things. That said, I’m not sure where a legged piece of construction equipment would be better than a tracked one.

For the most part, these things would be great for stuff like games (Rock’em Sock’em Robots, Ultra Sized Edition) or toys for the rich and elite (ever wanted your own robot butler capable of over six million forms of communication?), or just for stuff like “I wonder if we could…” projects that folks like MIT would play with.

MAYBE you could use a man-sized robot (MSTLR) for things like exploring sunken ships or depressurized space stations which would require manipulation of things like latches or wheels that would normally be used by a human hand, but where a human in a space suit or a deep-sea diving suit would be unable to maneuver (them suits are bulky)