I wouldn't really use the AT-AT as a bad example of why legs on vehicles is a bad idea. That thing is poorly designed as a weapon in virtually every way. It was super heavy armored, sure, but it was a slow and massive target with no real reason to be so. It only had a few small (for the vehicle's size) laser weaponry on the head of the craft, which is where the crew hung out too, leaving the huge part of the vehicle as a heavily armored... crew compartment? What was the huge chunk of metal for anyway? Add the fact that it was unstable enough to get tripped up by a cable (legs moving something that heavy should have been strong enough to snap that cable), had a high center of gravity, had no method to get itself back up, and, worst of all, had no way to prevent itself from falling. A low center of gravity would have prevented most of those issues. It could could have easily carried more, and nastier, weaponry as well as defensive turrets on the tops, sides, and rear to shoot down attackers from other directions.

But, at least it's not as bad as the AT-ST. That sucker has all of the issues of the AT-AT with the addition of less stability of being on two tiny chicken legs and armor so thin and wimpy a couple of logs are able to squish it. That sucker is nothing but a death trap for the crew controlling it.

Star Wars did better in Episode 2 with what I think is called the AT-TE. That low to the ground, six-legged walker the Republic used. Low center of gravity, frontal weapons, a turret, heavy armor... it more or less corrects all of the AT-AT's issues, which is ironic since it's before the AT-AT.

@darthkev, on 01 November 2011 - 12:07 PM, said in Military Hierarchies:

... the airplane is already circumventing water travel to an extent today.

Not for heavy freight it isn’t, and the navy is still likely to play a major role in any major deployment that occurs beyond the range of a friendly fighter base. If you’re attacking from space, then you clearly have heavy-lift spacecraft, but how much do they cost to operate, and are they able to stand up for themselves in a fight? Most science fiction seems to take for granted that such vessels will be largely helpless.

Josh: I think the only even vaguely rational explanation for the AT-AT is that its primary design goal is to scare a much weaker opponent, whereas the ‘earlier’ AT-TE comes from a government which takes its enemies seriously. And the AT-ST is clearly manufactured by a Grand Moff’s brother-in-law.

Regarding FTL travel and communications, that's entirely up to how the author designs the universe.
For example, say Quantum Entanglement is developed into a digital high-bandwidth communication system. You now have instant communication regardless of distance, you can now control entire ships remotely with robot crews from humans sitting on a planet somewhere.

Otherwise you make up the speed of FTL communication as you see fit for the story - slower if you want a more independent group at the frontier, faster if you want more bureaucracy or a unified and coordinated military over the entire universe.

On FTL travel speed, you can throw special relativity out the window and say "it takes x days (relative to a motionless clock) to jump y distance, based on ship mass or whatever" as the EV universe does, in which case reinforcements, resupply and other deliveries might arrive too late. If you have an instant-jump (eg: wormhole-on-demand type engines) then there's no reason for resupply/reinforcement/etc to ever arrive too late unless someone screws up. Or you can keep the time dilation section of special relativity ("these huge engines just make me go really really fast in normal space") and nothing will ever arrive in reasonable time, and the frontier is really on its own.

@Darthkev: Planetary magnetic fields tend to be weak. You would need a ridiculously strong magnet to hover on most planets, and there's the small side effect that any magnetizable or already magnetized metal near the hovermagnet will either fly towards or away from the hovermagnet at very great speed. Also, EMP-shielded electronics already exist (see: Faraday Cage).

@lnsu, on 01 November 2011 - 02:03 PM, said in Military Hierarchies:

If you have an instant-jump (eg: wormhole-on-demand type engines) then there's no reason for resupply/reinforcement/etc to ever arrive too late unless someone screws up.

Or if you want a really convoluted plot, why not say that jumps through hyperspace send you back in time?

Yeah, quantum entanglement was another one of those things where I thought "hey, I've come up with a reasonable explanation for FTL communication," and then played Mass Effect. Or actually Mass Effect 2.

On walkers: I've never really seen a "pro" argument that outweighs the "con" arguments. Getting those joints articulated correctly would require an enormous investment on the R&D front. Once you get past the development hurdle, which would probably be enough to keep it from getting past the concept stages in the first place, you still have an incredibly intricate, hence very vulnerable, system that will ground you craft if the slightest thing goes wrong with one of the innumerable moving parts that would have to go into each leg. Then you factor in how bloody much it would cost to build a set of legs as opposed to... anything else, plus the extra equipment it would necessitate (Battle Tech does a good job of going into how much stuff it takes to keep a walker walking), and you're pretty much staring down a crapshoot.

On the plus side, I can see the whole "better on bad terrain" part, but that doesn't seem like enough to me. Additionally, I've never really seen anything that made it seem to me like walkers would have an easier time with rough terrain to begin with. It seems like it would actually have a worse time on rough or uneven terrain, since whereas even modern armor can deal with unevenness, a walker, even with 6+ legs and a low center of gravity, would either need incredibly intricate sensor and locomotion equipment (and now we're talking $$$$$) or be thwarted. Unless you want the pilot determining where to put each foot down on every step.

Plus, presumably, your universe has something resembling tanks or better, aerospace fighters, possibly portable artillery, etc. So they're not going to be accessing anything you couldn't otherwise. And walking, even in the future, is a really inefficient, slow, easily-disrupted method of transport. So that makes a very short list of pros (assuming terrain advantage) and a pretty extensive list of cons. In the end, it pretty much boils down to "what's the point?"

Finally, to jump back to Josh's thoughts on an entirely space-faring society, I think we're are operating on different presuppositions. The battleship analogy works only to an extent. Battleships aren't equipped to create food, can't strip passing fish (asteroids/planetoids) of their resources for fuel and materials, and, most importantly, can't build more ships. You'd probably have to be able to do all of those things, particularly having a mobile manufacturing infrastructure, to make it viable. So we'd be talking a pretty far advanced society, even by SF standards.

Just as importantly, you seem to be assuming that the galaxy is mostly populated at this point (hence most resources are claimed), while I'm operating on the opposite premise. Honestly, I have a hard time envisioning a galaxy in which there aren't ample resources a mobile society could exploit, assuming they have the tech for relatively easy FTL travel. (Don't forget: despite what pop SF tells us, there's an awful lot of stuff out there. It'll be a long, long time before anyone uses all that stuff.)

@Dave on AT-ATs: I pretty much came to that conclusion too as that's about the only thing it'd be good at (and it did work there for a bit). If the Rebels had been better prepared for an attack, I think the fight would have gone much differently after they got past the whole scare thing and realized "Oh, we can just trip them!"

@Walkers in general: I have no idea what the video is called or what the link is, but a couple or so years ago someone showed me a video on YouTube of researchers showing off their mechanical walker. It was four-legged and about... waist high if I remember. They had it navigate normal ground, grass, concrete with patches of frozen ice, being kicked and shoved, a bridge made of randomly placed bricks, an arid, rocky place, and some other difficult terrain. It navigated all of it without falling down. It slipped on the ice and stumbled when it got kicked, but it managed to stay on it's feet. If we can make stuff like that now, sci-fi people should have no issues making complicated walkers capable of maneuvering over difficult terrain. Costs and whether it's worth making those are still very valid issues that come up, however.

@Nomadic wars presuppositions: Probably. I'm more leaning towards the "All the good worlds around civilized space are claimed" and "If they're truly a nomadic society, they won't be sticking around any one place for long to do a serious mining operation nor would they have the machinery/technology to do so efficiently because they don't need it normally." They could find some great, untouched worlds away from civilized space, but if they're far out then there isn't going to be a war going on without very fast travel speeds.

My sea-going vessel analogy was the closest I could think of in modern terms. It'd probably be better if you assumed they were modified to have some farming and manufacturing for self-sufficiency or brought along large (and vulnerable) cargo vessels modified for those purposes. Either way, they're still at a severe disadvantage in most instances. Atilla the Hun in space could theoretically show up, but I think even he had a home base of sorts.

@david-arthur, on 01 November 2011 - 02:36 PM, said in Military Hierarchies:

Or if you want a really convoluted plot, why not say that jumps through hyperspace send you back in time?

Privates, three days ago we lost Stardock Alpha to an attack by the aliens. In two hours, you're going to be sent out through hyperspace so you can arrive just in time to save the station.

Ah, the chicken walkers. It's like an engineering marvel brought to you by Wile E. Coyote. I'm ish on the walker idea. For the amount of engineering that would go into it vs. the practicality of it, I'm not seeing the cost-benefit stackup here. Maybe they can navigate difficult terrain, but better than just an all-wheel drive SUV type of robot? And more reliable in mechanics? I'm skeptical.

Backtracking to DarthKev's statement on anti-gravs with electromagnetism. There are two major problems with trying to use a planetary magnetic field for levitation. One, as brought up, the field is incredibly weak on the whole. The magnetic field of the Earth, for example, generally ranges between .25 and .65 gauss in intensity. A strong refrigerator magnet, on the other hand, might be somewhere in the neighborhood of 100 gauss. Secondly, because the poles are so far apart, you don't have a localized enough north-south to repel against. A mag-lev train operates on the order of several hundred thousand gauss, requires significant wattage, and has fixed-pole magnets all along the track to keep the train levitating and moving forward. No good if you want to hover just using the magnetic field of a planet.

On the subject of time travel. I hate time travel. I don't mean I hate plots based on time travel or anything (some of my favorite Trek episodes revolve around it, truthfully.) Time travel just gives me a serious headache when I attempt to figure out all the causality issues and paradoxes. Then, you have to question the whole idea of bubble universes, parallel timelines, and all that jazz, and by the time you're done, migraines ensue. Thus, I take the attitude of my favorite Trek captains: avoid it at all costs, and don't ever, ever let the Department of Temporal Investigations know if something happened. (Now, all that said, Trials and Tribble-ations was one of my favorite episodes of anything. Ever. It was made of sheer awesome and coated in incredible.)

I explored the idea of using quantum entanglement for non-interceptable real-time communications with my recent bar exploits, but I anticipate that the bandwidth availability would likely be fairly limited, realistically. Probably no better than short text messaging or binary beacons, I would figure. It is a realistic form of FTL communication, however, if physics can overcome the issue of separating entangled particles without either decaying or becoming disentangled. I actually did a little undergrad research on the subject back when I was still a physics major.

I think with nomadic spacefarers, it's more likely they'll simply avoid war by moving away from hostile powers, fighting wars only when they choose, and against weaker opponents (then moving on after looting the spoils).

The other option, I suppose, is the Ghengis Khan route.

I do sort of like the idea of a conquering nomadic force, where they leave vassal states in their wake but don't have a permanent home of their own, seeing the territory they conquer as merely sources of tribute to collect the next time they wander by.

I'd never really even thought of the conquering nomadic force route, since my one thought experiment on the subject has been with a militant and aloof but ultimately well-meaning society – perhaps Vorlons would be a good analogy, sans the millennia of socially and genetically manipulating every sapient species in the galaxy. That could actually be a really fun route to take, since the liberties and restrictions imposed by such a way of life would be a blast to explore. Quick hyperspace travel would mean that it wouldn't be hard for a fleet to threaten to eliminate a rogue vassal (or just a few planets as an example). But it could also be a logistical nightmare, depending on how well the fleet can support itself and its crew.

That also brings up an aspect of interstellar conflict I've only seen addressed a few times (Ender's Game, maybe Babylon 5... that's about it). Depending on how precise hyperdrive systems are and how many ships different navies can field (and less sexy things like the mass of ships and how much thrust they can produce), there's an enormous risk that a few ships could drop out of hyperspace near a heavily populated planet and wrack up a couple hundred million civilian deaths before anyone could respond. Seems like a mobile people, beholden to few scruples and relatively safe from a counter-attack in kind, could quickly become a terror. Or could planetside (or perhaps orbital?) defenses be enough to discourage such attacks?

Well, the most scary thing of all I don't think has even been brought up yet: relativistic or FTL weapons themselves. If you've got the power to accelerate a 100 kg mass to roughly .95C, you've got a recipe for planetary devastation. If your FTL concept does not require the use of a supporting subspace like dimension, it's even more frightening. A warp capable ship (manned or unmanned) that flies into a planet, space station, or fleet with the sole purpose of being a kamikaze run? If you have a fleet than can drop out of FTL on the edge of a system or even around say, the orbit of Mars or Jupiter, you'd likely hardly notice them, if you did at all. Fire off a 100 kg relativistic missile, sit back, and watch the ensuing chaos.

@krugeruwsp, on 01 November 2011 - 10:48 PM, said in Military Hierarchies:

Well, the most scary thing of all I don't think has even been brought up yet: relativistic or FTL weapons themselves. If you've got the power to accelerate a 100 kg mass to roughly .95C, you've got a recipe for planetary devastation. If your FTL concept does not require the use of a supporting subspace like dimension, it's even more frightening. A warp capable ship (manned or unmanned) that flies into a planet, space station, or fleet with the sole purpose of being a kamikaze run? If you have a fleet than can drop out of FTL on the edge of a system or even around say, the orbit of Mars or Jupiter, you'd likely hardly notice them, if you did at all. Fire off a 100 kg relativistic missile, sit back, and watch the ensuing chaos.

Worse yet, just target the system's star, in order to cause it to either explode or collapse on itself to create a blackhole. In terms of orbital strikes, mass drivers that can propel either localized asteroids or space junk of destructive size can also be effective in causing chaos if the point is to not save the planet for habitation or resource collection.

@JTH

Boston Dynamics is doing a lot of good work in walking robots:
http://www.bostondynamics.com/

BigDog:
PETMAN: http://www.youtube.c...h?v=mclbVTIYG8E
AlphaDog: http://www.youtube.c...h?v=SSbZrQp-HOk

There are a lot of other people doing similar work too, they're just who came to mind first for me.

That's the exact video I was referring to. Good find. That Alpha Dog is even more impressive.

This post has been edited by JoshTigerheart : 02 November 2011 - 02:40 PM

See, I'm still not seeing the advantage over a wheeled rover vehicle, especially in speed. I can't see that this would be remarkably better at terrain issues.

And I still see benefit in using legs. Yes, we have EMP shielding, but that still has its own weight you then have to compensate for. If your method of mobilization isn't electrical at all (or at least is only minimally electrical) then you can minimize or even eliminate the weight added by EMP shielding, allowing the addition of other equipment in its place. I'm not saying it's a good idea to make it your only method of locomotion, but it's still a good choice for certain circumstances. As already mentioned, legs are slower than wheels and hovering, so if you need speed you need another method of getting there. But if all you need is to get from point A to point B, legs work fine. I still maintain legs are better for extremely uneven terrain than wheels. I also believe there's a good chance of it requiring less energy than hovering. Lastly, there's still the scare factor previously mentioned; the vibrations will announce your presence, but in a good way when things start falling over.

Edit: @Josh: I wasn't using the AT-AT as an example of a weapon. I was using it as an example of a legged vehicle. However, while the Rebellion's leadership did manage to escape during the Battle of Hoth, the battle was still a major victory for the Empire. Firstly, not all the Rebel transports escaped; at least six were destroyed before even taking off. Secondly, the Rebellion only managed to down a total of four AT-ATs using the tow-cable method. All in all, the AT-AT isn't a bad weapon. The Rebellion may have even been ended on Hoth thanks to the AT-ATs if not for Admiral Ozzel. As for your question on the purpose of the main body, it's a troop deck capable of carrying a minimum of 40 troops along with speeder bikes and spare weapons.

This post has been edited by DarthKev : 03 November 2011 - 12:56 AM

It could still use turrets on the main body. And the fact that it has a head at all means it has a neck, which is another structural weak point, legs notwithstanding. I agree that the AT-TE is the far superior walker. Anything spindly means structural weakness.

The Rebels really weren't prepared for an attack if I remember correctly. At least not one of that scale.

Anyway, the development of those legged robots in the videos are being funded by the military, so they must have some use for them in mind. If not for combat purposes, it could be for utility, such as one of those robots accompanying a group of soldiers on foot by carrying extra supplies. In a sci-fi setting where amazing A.I. is prevalent, or you simply have someone controlling it by remote, it'd be trivial to attach a small weapon or two so that it can help out in combat situations, even if that's not its primary purpose.

@joshtigerheart, on 03 November 2011 - 01:16 AM, said in Military Hierarchies:

The Rebels really weren't prepared for an attack if I remember correctly. At least not one of that scale.

If I recall correctly, the Rebels would never have been able to hold off a dedicated push from the Empire under any circumstances. Remember, their bases were:

Yavin IV: Hidden base that was nearly crushed instantly and evacuated as soon as it was discovered
Hoth: Hidden base that was crushed instantly and evacuated as soon as it was discovered
Home One: Mobile base (they figured out that being able to take their base with them if it was discovered was helpful)

In those circumstances, maybe you could justify AT-ATs, sort of. They're big and scary looking and if they take a bunch of fire so your more fragile forces, like the crappy chicken-walkers, can get in close, maybe they've served their purpose in some way. Still though, what's the mass of one of those things? And how many not-god-awful vehicles and weapons could you cram into a transport for the same mass/space?

Back on the subject of walkers in general, Josh brings up a good point: outside combat, walkers would be considerably less impractical, since probably the biggest weakness is how vulnerable such a complex system of locomotion would be to enemy fire (and the possible center of gravity issues). And I hadn't considered terrain like mud or snow, where treads and wheels could probably struggle more than a walker – maybe (3 qualifications is probably enough).

The advantage walkers ostensibly have on rough terrain is that they can select what points of the terrain they use to support themselves, allowing them to step over impediments (like climbing rubble in the video), and they can dig down and get a grip in things like mud or snow (although wouldn't the levels of energy you'd have to be able to produce for your future society to be viable render things like melting snow (on planets that aren't absolute 0) on the fly or powering through mud pretty simple?) The thing, though, is that it seems like if you took those advantages, and put treads on the "feet", you'd still have a vastly superior system. The majority of the time, you'd be rolling, which as we've discussed is many, many times more efficient and and quicker than walking. Uneven terrain can still be bypassed by adjusting the treads/wheels up and down and side to side, and you'd definitely have high enough PSI on the "feet" to dig down and get traction in wet terrain, but you're not really walking. Rubble would still require walking, but shouldn't be much trouble because you have nice, flat, broad treads to support you. And as Josh (I think?) mentioned, the spider-like legs of the AT-TE would help center of gravity issues while giving a good range of motion. Think of a spider on roller skates, except the skates are treads. And you're not as severely crippled if a single joint goes out of commission.

So I will concede that in wet terrains, assuming the hypothetical tech level isn't high enough to nullify the terrain problems, or in rubble, where you may not be able to climb with treads for fear of dislodging the rubble itself, a walker could be able to make it through some environments that other ground vehicles couldn't. And if you're a pack mule for infantry, you don't really need the speed. Any other situation, though, and I can't see the advantages unless you're in a place that other vehicles simply can't pass. And even then, it seems like it would be a competition between our future analogs of air support and hovercrafts.

There's a bunch of other situational things to take into account too. What do the inhabited planets in-universe look like? If there's a bunch of yucky, marshy/snowy/rocky places, that makes walking more appealing. How densely populated are your planets? If they're not packed, since colonists can select where to settle, you're less likely to run into poor terrain (and since we're talking orbital deployment, quickly bypassing terrain in between population centers should be a breeze). How economical is it to operate fighters in the atmosphere, and how much mass can they carry? This, combined with the above, may dictate that it's simply more practical to use aerospace craft and infantry in difficult-to-reach areas than dedicate resources to walkers for what would probably be that sole purpose.

You'd also have to consider how accurate orbital bombardment is (which would also determine how legal/ethical it is), but that applies to all ground combat. If you can snipe defense installations from orbit, ground forces would start to shift focus to occupation and suppression, in which case walkers' advantages would seldom apply. You don't have to walk across that inhospitable terrain to blow up the enemy bunker if it was dust before you had any boots on the ground.

Actually I'm kind of glad I got to that last point, because that's another really important aspect of interstellar military operations that I don't see get brought up often, and it has a lot of rumination potential.

@Darth, you can have non-electrical wheeled transport easier than non-electrical legged transport. EMP shielding can be made from thin mesh, use the power source that powers the rest of the vehicle, and does not weigh enough of use enough power to really have any tradeoffs, especially on a cargo-carrying vehicle. Also, legged transport relies on electronics just as much as wheeled, if not more so.

@JTH: They're intended to carry supplies through rough terrain where trucks can't go, but people can. I think.

Quote

When fully developed (AlphaDog) will carry 400 lbs of payload on 20-mile missions in rough terrain. The first version of the complete robot will be ready in 2012.

Yeah, and this is why, from a pure engineering standpoint, I don't see the additional value of walkers as opposed to wheeled or tracked vehicles, especially if they can hover or fly as well as being wheeled or tracked. For short distances in sticky situations where wheels or treads just won't cut it, then fly/hover. For 95% of situations, though, it shouldn't be an issue. And, as Archon brought up, most likely air/space superiority will be a key battle first before infantry on the ground is going to have to occupy or suppress defensive positions, especially if highly accurate orbital bombardment can be achieved, or at the very least, strong air superiority and bombing.

Walking vehicles, from a combat mechanical/engineering standpoint, are just too complex, in my opinion. There's a whole ton of articulated movements to deal with. If something goes wrong, there's just too much to fix. You want a vehicle that is durable and simple as possible. This was the great advantage of the Jeep in previous wars. They were a durable automobile, but they were ridiculously simple in design and easy and quick to fix. I think the same would need to be true of aerial combat vehicles or crossovers like I'm proposing. It would need to be simple to operate, simple to repair, and cost-effective to build.