Legged military vehicles

[removeduser_4536284751384]

http://www.youtube.com/watch?v=-uKID...eature=related
Take a look at this video, and imagine instead of a small robot a huge heaxpod or octopod tank. Legs have a whole host of advantages over tracks for military vehicles.

They provide some great tactical flexibility. You see in the video that the height of the vehicle could be easily varied. If a lower profile is needed a legged tank could simply sit on its belly. Or when going hull down, it can raise itself up and use much higher obstacles than tracked tanks for cover - gentle slopes aren't the only option. It could even peer around corner like a person, only exposing a small part of itself. Or if the worst comes to the worst, angle itself in the way that makes enemy shells most likely to deflect. Basically it can use terrain and its own structure in a far more flexible manner than traditional tracked or wheeled alternatives.

They also add al lot to mobility. Tanks are actually suprisingly immobile. They can't go everywhere infantry can go. In fact the US Army guestimate that wheeled vehicles can traverse 40% of the Earth's land area and tracked vehicles 70%. A legged military vehicle could traverse a great deal more, being able to pick its steps carefully. An at the operational level, a legged vehicle can cross huge gaps compared to tracked or wheeled vehicles. They could step across the streams, bogholes and crevices that litter every landscape in the world far more effectively. They could also traverse higher cliffs than tracked or wheeled vehicles.

A legged vehicle could also have a lot more flexibility in its design. Modern tanks can't be wider than 4 m because they'd be unable to fit on civilian road infrastructure. A legged vehicle can walk with closer footprints than its maximum width, so it can be made a lot wider. As you see in the video, it could also be folded up and transported some other way. Without these restrictions, an legged IFV could hold 14 men and still carry more powerful weapons than a current tank. A dedicated legged tank possibly be armed with a railgun and still have acres of space to store the capacitator banks needed to power such a weapon. And with all this increased size, the survivability of the vehicle would not necessarily be impacted. The legs are basically extra armour and I've already outlined how legged motion lets the tank use terrain to its advantage far more flexibly.

And on the survivability note, legs are a lot harder to destroy than tracks. Legs can actually be armoured, and shaped to deflect fire. And even if they are destroyed, only 3 legs are needed at a minimum. A tank with 6 or 8 has a lot of redudancy. That's not to say losing legs wouldn't affects its speed, stability and ability to traverse difficult terrain.

So why has there been so little research into this area, outside of science fiction depictions that are almost universally inaccurate. Let me criticise the Star Wars AT-TE:

They go to all the trouble of developing complicated legged motion, and they connect them to the bottom of the vehicle. That's basically destroying the vast majority of advantages that legs provide. If a military vehicle is going to legged, the legs need to be side mounted like an insect's. They need to have a knee joint above the vehicles hull to allow for greater maneuverability.

Not to mention these walkers are ridiculously tall for no good reason. The armour at the sides is almost vertical. And then there's the exposed main gunner and that huge glass window at the front. Need I say more?

[Gelgoog]

your vid does not work.

[Sphere]

Many problems ...

1.) Crappy soil is less than 2000 PSF bearing stress. That means you need ~1SF of ground contact per ton of of tank to keep from simply sinking into the ground. A modern tank like the M1 Abrams is ~61 tons. Wanna guess at its area of ground contact is? It's 62.5SF Same rules would apply to a "walking" tank. For every ton would would need roughy a SF of ground contact. That means the "feet" would have to have ~double the area compared to tank tracks, because half the feet wouldn't be on the ground. Also the "leg" system itself would me much much heavier than simple tracks. In the end it would end up needing clown feet if it was ever to be used on any surface besides pavement.


2.) A vehical like the abrams can do 45mph on rough roads, 60mph on paved roads. It would be very difficult to get a legged vehical to go faster than a human walking pace. It would need to be trucked to where ever it was going to be used which rather defeats the point of armor in the first place.

3.) Keeping the simple mechanical sprockets and track-links in a tank from falling apart is very difficult in wartime conditions because trying to move around 60 tons of steel involves a lot of stress and strain. Keeping hydraulic systems running on just light construction equipment is itself a pain, much less these highly complex and massive "legs" that presumable would have to hold up 60+ tons continuously, not to mention moving it around and taking fire.

In short this would be a complete nightmare.

[removeduser_4536284751384]

1.) Crappy soil is less than 2000 PSF bearing stress. That means you need ~1SF of ground contact per ton of of tank to keep from simply sinking into the ground. A modern tank like the M1 Abrams is ~61 tons. Wanna guess at its area of ground contact is? It's 62.5SF Same rules would apply to a "walking" tank. For every ton would would need roughy a SF of ground contact. That means the "feet" would have to have ~double the area compared to tank tracks, because half the feet wouldn't be on the ground. Also the "leg" system itself would me much much heavier than simple tracks. In the end it would end up needing clown feet if it was ever to be used on any surface besides pavement.

For a 70-ton vehicle that works out at 2 square meters for each of the six feet, which is not very big at all. If they were rectangular, 1x2 m, that's narrower than the WWII Tiger tank tracks and only slightly wider than M1 Abrams tracks.

And even if you made them pointy and they sunk into the ground, I think that might be an advantage. It would provide more grip, so it would be better able to climb rough, steep slopes. In fact I can imagine them having interchangable feet for different conditions, including high-area ones for boggy ground.

2.) A vehical like the abrams can do 45mph on rough roads, 60mph on paved roads. It would be very difficult to get a legged vehical to go faster than a human walking pace. It would need to be trucked to where ever it was going to be used which rather defeats the point of armor in the first place.

No it wouldn't. I've linked to the video, it had a URL that couldn't be embedded. Watch it and see how fast it goes. It could probably go human running speed. And for faster travel, the bottom of the hull could have tracks or wheels.

3.) Keeping the simple mechanical sprockets and track-links in a tank from falling apart is very difficult in wartime conditions because trying to move around 60 tons of steel involves a lot of stress and strain. Keeping hydraulic systems running on just light construction equipment is itself a pain, much less these highly complex and massive "legs" that presumable would have to hold up 60+ tons continuously, not to mention moving it around and taking fire.

I can't imagine them being any more maintenance intensive than excavator arms. The immense advantages they give more than offset this.

[Jaketh]

I see legged vehicles such as this becoming common place within the next 40,000 years

Spoiler Alert, click show to read: 

If bipedal constructs turn out to be unstable a quadruped construct akin to a Imperial AT-AT may actually be viable as a large stable weapon platform for the military

[removeduser_4536284751384]

If bipedal constructs turn out to be unstable a quadruped construct akin to a Imperial AT-AT may actually be viable as a large stable weapon platform for the military

while there is certainly no disadvantage with quadrupedalism, the AT-AT is miles too tall, too poorly protected, has its weapons in crappy places and is generally a terrible design.

[Mortality]

The problem with large legged military vehicles is that price tag. They would make their worth quite soon, but it would just end up with your enemy (Assuming this is going to be a conventional warfare) comes up with their own design. I would imagine a pseudo AT-AT would be common place in a battlefield a couple hundred years from now.

[Jaketh]

while there is certainly no disadvantage with quadrupedalism, the AT-AT is miles too tall, too poorly protected, has its weapons in crappy places and is generally a terrible design.

A bipedal design like the one that i posted would actually be a stable platform due to the massive skyscraper wide legs, it would take a direct hit from a nuclear ICBM to knock one on its ass, the only problem is the massive cost, But the pure badassness of such a warmachine would outweigh that

[Voodo chile]

The US military is in the stages of developing basically a large dog/pack mule which is a robot. Well its partially funded by the marine corps. First version of the completed robot to be released in 2012

[Irish Warrior]

The advantages are completely negligeble compared to the cons, if one of the legs is hit, then what? It gets dragged back to the repair area, further damaging itself?
The machinery on the inside would have to be fairly fast for weight, and so the feet need to be bigger to handle the increased weight it needs instead of just an engine.
The idea hasn't been looked into because it would be incredibly diffucult to make and maintain.

[removeduser_4536284751384]

The advantages are completely negligeble compared to the cons, if one of the legs is hit, then what? It gets dragged back to the repair area, further damaging itself?

Read the OP before you post please. We've already established a hexapod or octopod can stand on three legs. That's one of the advantages. It can lose several legs on both sides and keep going. One RPG-7 to the tracks and a modern tank is out of action.

Plus, legs can be more armoured than tracks to begin with.

The idea hasn't been looked into because it would be incredibly diffucult to make and maintain.

But it has and is being looked into. Just not in combat vehicles, but logistics ones. Many commercial forestry vehicles are currently legged.

[Irish Warrior]

Read the OP before you post please. We've already established a hexapod or octopod can stand on three legs. That's one of the advantages. It can lose several legs on both sides and keep going. One RPG-7 to the tracks and a modern tank is out of action.

Plus, legs can be more armoured than tracks to begin with.

But it has and is being looked into. Just not in combat vehicles, but logistics ones. Many commercial forestry vehicles are currently legged.

I did, my point remains, with one leg gone the stabilty is severly damaged and the on board computer would simply not be able to cope with such a spike in activity.

And yeah in a non military view it could be very beneficial, as a machine that can work offroad and then transport the goods would be a lifesaver.

[removeduser_4536284751384]

I did, my point remains, with one leg gone the stabilty is severly damaged and the on board computer would simply not be able to cope with such a spike in activity.

That completely depends on how incompetent the designers are.

[Helm]

Mech on mech action that's what we want to see.

Spoiler Alert, click show to read: 

What they could do is give you something between a tank and and infantry soldier.

[Jaketh]

Designs like the one below are reasonable in terms of functionality vs cost

Spoiler Alert, click show to read: 

[LSJ]

For large military machines, I don't see legs being practical.


- With a tank, there isn't so much surface area to armour. It is essentially a flat box with a flatter box on top. Armouring legs would add several tons per leg, as each of the legs would require heavy hydraulic structures and require thick armour around each of the structures. The surface area to armour is much greater for a legged box compared to a tracked box.

- A tank of modern design only has two exposed joints - the turret ring and the main weapon mount. With a legged vehicle, there are, in addition to those two exposed joints, several per leg, unless armour is extended to cover the joints like full-plate (then there are still at least one per leg where it attaches to the body).

- Tracks are easier to repair and maintain. When a tank has its tracks blown off, it can have new wheels put on and new links fixed onto the tracks. If a leg suffers catastrophic damage, electrical and hydraulic systems have to be repaired, and possibly a new leg attached. And the cost of one leg repair would be much higher than the cost of replacing tracks and wheels.

- Tanks are capable of high speeds and fast turns. A six or more leg design would not be capable of speeds and maneuvers anywhere near that of a modern MBT.

- A legged vehicle with a low profile would still not be able to climb many slopes or bypass many objects, such as mountains, swamps, and forests; the operational range expansion is minimal. Tough terrain will always require infantry and air support.

For such things as small resupply and recon vehicles/robots, legs can be very useful (like the "dog-bot"). But they are not practical for main combat roles.

[removeduser_4536284751384]

- With a tank, there isn't so much surface area to armour. It is essentially a flat box with a flatter box on top. Armouring legs would add several tons per leg, as each of the legs would require heavy hydraulic structures and require thick armour around each of the structures. The surface area to armour is much greater for a legged box compared to a tracked box.

I assume legs would be armoured only to resist enemy RPG and light cannon rounds. It would be impossible to armour them against tank guns. Active protection systems are a better idea.

In fact, I think the legs will be an integral part of the tank's armour - they are thick metal structures on both sides of the tank, making it far survivable than current tanks.

- A tank of modern design only has two exposed joints - the turret ring and the main weapon mount. With a legged vehicle, there are, in addition to those two exposed joints, several per leg, unless armour is extended to cover the joints like full-plate (then there are still at least one per leg where it attaches to the body).

I don't really think it changes much - a small cannon or rocket won't cause any damage. A tank's main gun will catastrophically destroy a leg no matter what. The thing is, with this design only the leg is destroyed. With current tanks, an enemy's main gun will completely destroy the tank.

- Tracks are easier to repair and maintain. When a tank has its tracks blown off, it can have new wheels put on and new links fixed onto the tracks. If a leg suffers catastrophic damage, electrical and hydraulic systems have to be repaired, and possibly a new leg attached. And the cost of one leg repair would be much higher than the cost of replacing tracks and wheels.

Tracks are easy to repair, but suspension and transmission isn't. That's the most comparable to a leg and it involves a huge amount of repair work and disassembly to fix. A leg could just be removed and replaced by a new one easily enough. That would be cheaper than the work that's required if an Abrams gets hit from the side the inside the track.

- Tanks are capable of high speeds and fast turns. A six or more leg design would not be capable of speeds and maneuvers anywhere near that of a modern MBT.

To the contrary, the only thing a tracked tank has over a legged one is speed. A legged tank can turn on a dime far faster than a tracked one. It can also swing itself around and raise itself up or down. Look at my first video link.

- A legged vehicle with a low profile would still not be able to climb many slopes or bypass many objects, such as mountains, swamps, and forests; the operational range expansion is minimal. Tough terrain will always require infantry and air support.

But the brilliance of legged designs is that they can be both low and high profile at the same time - the legs let them easily adjust their ground clearance at the demand of the driver. It can sit on its belly to make itself smaller if it's caught in the open, or behind a hill it can quickly raise itself up on down. And there are far more cover hills available to a legged design than a tracked on, which requires a gentle slope. A legged one couldlook out from behind some obstacle like a depression or cliff.

[Solid Snake]

Metal Gear....

[GrnEyedDvl]

Have you guys seen any of the modular robot designs?

http://www.youtube.com/watch?v=4oSavAHf0dg

[Ak1980]

How big is the leg vehicle we are talking about? Too small powered suit (in future) will be better, too big tank will be better. Problem with leg vehicle is armored distribution it will never as armored as tank, walker only advantage over tank is the ability to move in rocky terrain, but we can use combination of drone and power suit to do the same thing. Also too many leg = too many moving part = higher cost? Also isn't tank capable to climb 30-45 degree hill?