Plausible reasons for Hovertanks

Question

A less common, but still cool (imo) feature of science fiction is hover tanks. Be they using antigrav, quad-copter style rotor blades or just the inflatable skirt of modern hovercraft.

However, they suffer a lot of the same issues as combat mecha, in that they rely on very fragile and complex tech, without which they immediately bite dirt. Additionally they just can't pack the same payload, meaning they can't even armour up their weak points.

However, just like this question about mechs, our world in question can build hovertanks to a similar cost as other combat vehicles. When would it be an advantage to use hovertanks over their tracked/wheeled/legged cousins?

Answer 1

Terrain considerations.

Most ground-based propulsion has some kind of surface that they cannot function well in. Wheels spin out on loose sand, legs can topple on boulders, tracks lose traction in swamps and wetlands, and neither can move through deep water.

Hover vehicles have none of these issues. Even if their altitude is limited to a few feet, they can cross any semi-solid surface without issues. They are also immune to most kinds of pressure-based landmines, and quad-copters can even cross chasms without problems.

Hover vehicles crossing actual rivers and lakes depends on the way of hovering, but most types will allow that as well.

Answer 2

Whenever mechs and hover tanks are discussed people always only point out their drawbacks and ignore their advantages. However when we look at wheels versus tracks we can list various advantages and disadvantages, then use those to determine when you want to use one or the other depending on the vehicle's characteristics and usage. The same has to be done for a hover tank (and mech).

You might not want to build an MBT out of your hover tanks, but in any army the actual full MBTs are a minor group of the total amount of vehicles. There are tons of different armored fighting vehicles (AFV's) that serve in the army. And if your hover AFV is the heaviest vehicle that can cross the local marshlands, then it's effectively the MBT of those marshlands. Similarly your hover tanks might have a boost function that allows them to temporarily bridge large gaps (I do not recommend jumping). This way you can cross anti-tank ditches but also bodies of water that would require amphibious vehicles otherwise. Imagine those poor tracked tanks protecting a bridgehead while a bunch of hovertanks have crossed a few miles downriver and are now destroying their supply lines, moving back before any tank can get at them.

Defense:

Hover AFVs would sport less armor, but that isn't a problem, as that is what AFVs do. If you really feel the need you can always look at helicopters. With the introduction of the Russian Shilka, firing 23mm shells, most combat-oriented helicopters now have armor and rotors designed to withstand them. Your hovertanks would likely be able to sport armor around any fans it has, making them more resistant than helicopters. This puts them well into the range of most AFVs, which have enough armor to withstand small-arms, shrapnel and some small autocannons, but don't have much to gain from sporting more armor. Most of the rest of its defense would focus on using terrain and maneuverability to their advantage.

Weapons:

You can do two things, perhaps even both at the same time. A hover AFV could easily benefit from using weapons equipped on helicopters. This makes flipping the hover AFV with recoil much harder. The second thing is build the hover AFV around a gun to make it a turretless tank destroyer. A turret would increase the heigh of the gun and gives a risk of flipping; if built around the centerline of the AFV, you don't risk flipping, and the combination of tilting the thrustforces and a high turn rate let you aim the gun. The recoil can then effectively be used by the hover AFV. Upon firing, the recoil will push the vehicle backwards, allowing it to instantly reverse out of position and find a new spot to fire from. Although, since you are trying to move a 10 to 30 ton vehicle with recoil alone, it won't instantly scoot off into the scenery with every shot. The amount of recoil experienced is also lower. A normal tank has an acceleration phase where the gun pushes the vehicle backwards and a deceleration phase where the forces are bled out of the vehicle through the tracks, both often happening simultaneously for extra stress on the vehicle. A hover AFV would have a longer deceleration phase which reduces the total stress forces on the vehicle during firing, allowing it to fire a larger gun for its weightclass.

Terrain:

Just like you use a wheeled vehicle for city patrolling and a legged mech for steep hills and mountain combat, so do you use your hover AFV in the situations where it's useful rather than put it into the specific field a tank is useful. A hover AFV will spread its load over a larger area than a vehicle of similar weight (this does not mean it won't set off mines! 10 tons of hoverforces pushing down will trigger them!). Terrain you would use them are wetlands with many broad waterways, marshes, soft ground, areas with lots of bridges with a low maximum capacity, highly irregular ground, shingle beaches etc.

Maneuverability:

Hovercraft don't meaningfully touch the surface they are passing over. This means that if they turn their momentum will carry them onwards in the direction they were going. This is both an advantage and disadvantage. If you bring a Hovercraft up to speed and turn it, you can pass a clearing while strafing and fire a shot for example.

The disadvantage is ofcourse that making turns is a far longer process for a Hovercraft, which has to slow down in it's previous direction and start accelerating into the new direction. A solution is to add extendable friction feet to the bottom of the vehicle, essentially allowing you to add wheeled/tracked maneuverability to hovercraft. The friction feet could have a row of wheels for turning on asphalt, lock the wheels and use more friction on things like mud and have a wing-shape at the "ankle" of the foot so if you cross large bodies of water you extend the feet lower into the water and use a type of Hydrofoil design turning capabilities (which instantly helps it cross larger bodies of water more easily).

Answer 3

Reliability

As you say, the tank relies on a fragile piece of complex tech. The thing is that tech can be made reliable enough that it can outweigh the downsides. Computers and electronics are physically fragile, potentially can be hacked and could be disabled without ever getting near the tank. Currently all modern tanks come with a plethora of electronics. The reason for it is because the technology has become way more reliable, cheap, strong and offers benefits that outweigh any further fragility or weaknesses.

Your hover tanks can be much the same. The technology gets reliable enough for widespread use.

Floating, thus ignoring most of the ground composition, can be incredibly powerful. That is because mobility is getting more and more important. Tanks are made to withstand an attack, but practically always you want to prevent the attack. That can be done by striking first.

Moving swiftly into more advantageous positions, striking first and ignoring terrain is just very powerful. It might even help in some cases to float higher and lower to evade fire.

Finally they might be strong enough to float over water, in some favourable water conditions. That means they can have a more varied role, making them again better for their price as well as able to move tactically over a piece of sea and mount an attack from behind enemy lines for example.

Answer 4

Antigrav hovertanks aren't necessarily fragile

There's no particular reason that an antigrav system has to be overly vulnerable (more than, say, an internal combustion engine). Sure, it's pricey to repair and maybe you can't do it in the field, but as long as you don't get a bullet through it you'll be fine.

With an antigrav system, you can have heavier armour than on a regular tank. Suppose that all it does is reduce the effect of gravity on the tank by 95%. If you can build a regular hovercraft that weighs 4 tons (not unreasonable) you can build a 80 ton hovertank (cf 60 ton M1 Abrams).

That being said, there's no particular reason why you wouldn't put antigrav on a regular tank, especially if you could turn it on and off easily. Drive a supertank on regular roads without breaking all the bridges, then turn off the antigrav to fire the main gun. The niche that leaves for the hovertank is then just what other answers have pointed out: fast, terrain-independent ground vehicles.

Answer 5

Resistance to land mines:

If your antigrav device can function with armour between itself and the ground then it can withstand a small explosion that would blow the tyres or break the tread of a ground vehicle. If it distributes the weight of the vehicle over a larger area of ground than a tank's treads, or else if it makes the vehicle literally weightless, then it sets off fewer land mines.

High tech doesn't have to be more delicate:

After all, microchips are much more rugged than vacuum tubes. If the antigrav generator is some kind of solid-state device, perhaps in some way resembling an electromagnet, then it could be more reliable than a diesel engine by dint of having fewer moving parts, leaky fluids, things that can get clogged with soot, etc.

Answer 6

While the typical military hovercraft have been landing craft, the Finns experimented with a missile boat on a hover craft chassis.

While in many 'typical' situations, the hovercraft's 'fragility' (though modern materials for skirts might be bullet resistant) and difficulty of control may be an issue.

The trick is finding environments where they work - the Finns wanted hovercraft for operations over ice (where conventional ships can't operate) and water. Likewise a combat force in marshy riverine areas where an amphibious tank may get bogged down may find a hovertank to be more flexible for infantry support - the americans used hovercraft as patrol boats

Simply - they're most useful when they can go places where others can't.

Answer 7

Refer to Planetside 2, where this exact situation comes up with the levitating MagRider (the main battle tank of the Vanu) vs. the other two factions using more traditional tread technology. https://www.planetside2.com/

The core advantages of the hover tank in battle are:

• Ability to strafe tank shells, dumbfire missles, etc.
• Performance upgrades that 'boost' the tank speed via advantages in "frictionless" tech
• Ability to climb terrain more easily and bridge gaps over small distances (i.e. holes in the ground)

The core disadvantages are:

• Easier to kill/less durability
• Due to the power requirements for weight it tends to do less damage (reliance on energy weapons vs. heavier traditional shells)
• You can accidentally 'charge' off a cliff much more easily
• Maneuvering among other hover tanks can get messy due to the inertia (i.e. whoops, I accidentally turned your tank into a ramp)

There are quite a few videos out there you can refer to for practical problems that come up with them, and the game has been out for so long that much of the balance in tank technology has already been considered.

Answer 8

Low gravity and semi-liquid terrain

A sci-fi setting on a world with low gravity might be better suited for hovertanks, as it's easier to keep that weight up in the air - and as a bonus, key parts of the world may be composed of something like quicksand, where any really heavy object needs to have its weight spread upon the terrain across its whole bottom plane (like a plank or a hovercraft) instead of just wheels or tracks with a fraction of the total area.

Answer 9

If you had the technology to build massive hovertanks, you would not need them.

In modern warfare today, tanks have very few applications. They offer no advantages over alternative weaponry. Their only real purpose today is to LOOK intimidating - to project the illusion of power and might. They are for dramatic effect only. Their only functional use is against stationary targets, buildings, and entrenched positions on open, uncluttered battlefields. As the Iraqi war proved, they have limited benefit in war. A pickup truck with a missile launcher is far more effective.

A military that could produce these beasts would find it far more advantageous to build hundreds of smaller assault vehicles mounted with guided missiles than one huge tank. The problem with hovertanks is that the 'hover' adds absolutely no advantage to a tank. Tanks are made to be slow. In fact, they NEED to be slow. The more stationary and stable they are, and the more stationary and stable the target is, the more functional they are. They are quite effective against buildings and entrenched positions, useless against moving vehicles, helicopters, and fighter jets. Using ballistic weapons, developing a firing solution while both you and the target are traveling at high speed is nigh on impossible. The weaponry would have to be guided. Once you develop guided weaponry, high speed, and maneuverability (all characteristic of a hovertank), the heavy shielding of tanks becomes redundant. In fact, it becomes a distinct disadvantage. They just make much bigger, better targets for effective anti-tank weaponry. The more added weight, the lower the speed and maneuverability advantage. F=ma always prevails. The force needed to change the direction of a massive tank is still huge, be it on wheels or on some hover capability. The thrust would have to be tremendous (and it would have to be thrust, as there is no ground contact for any friction drive). That takes a lot of fuel, and fuel just adds more weight. These tanks would be jet fighters confined to the surface.

As a side note, the battlefield would be unmanageable, unless it were on absolutely solid rock. Everything, everywhere, would be projected all over the place, from the thrust. Newtons' Laws. In point of fact, these tanks would have to be operated in isolation, as the thrust from any nearby tank would blow another tank into tailspins and uncontrollable behavior. If the thrust is able to move the tank, it is able to move anything nearby. If the tank were on soft ground, the vertical 'hover' thrust would project as much mass from under the tank as the mass of the tank itself. All the thrust would do would be to dig a very large hole under the tank. In any conceivable battle using hovertanks, the tanks would be stationary. A hovertank battle group would be settled to the ground during battle conditions, no hovering at all. No advantage whatsoever from the hover capability. Siting ducks to lighter, more manoeuvrable assault weaponry.

On the other hand, if this 'hover' capability did not need thrust (anti-grav or whatever), then it would not be wasted on tanks. They would use it for hoversleds, as a generalist transportation vehicle. They would be used for moving everything from personnel to heavy equipment. They would be mobile weapons platforms. They would be mobile ballistic missile platforms. They would be used as surface-restricted alternatives to helicopters. They would be used as helicopter and VTOL launching platforms. And if they still wanted to have tanks, they would be used as sleds to transport these tanks. But they would definitely not be used as alternatives to tanks themselves.

Answer 10

The first problem is one of engineering. Assuming the reference to hover tanks refers to vehicles equipped with ducted air fans and a 'skirt' or similar the issue becomes one of weight vs mobility.

Any military tank fitting the classic definition has to be;

A) Heavily armed - carrying a significant weapons payload of some type;

B) Heavily armored/protected - equipped with armor and active protection systems capable of defending it from heavy weapons fire;

C) Capable of maneuvering across varied terrain over an extended range.

However with hovercraft you get a trade off. Specifically you generally get (C) at the expense of (A) & (B). This is because every kilo of weight you add in armor and weapons dramatically increases the size/power requirements of the lifting fans and fuel consumption of the vehicle. So for the cost of building a hovercraft with the armor and weapons of a main battle tank you could probably build a dozen more fuel/cost efficient 'normal' tanks - which will also be much quieter than a 'souped up' heavily armored hovercraft.

Secondly you have the maneuverability issue. Hovercraft are great at traveling over open/mixed terrain at high sped. And terrible at breaking, changing direction/cornering compared to wheeled or tracked vehicles. This is because their speed comes at the cost of traction. (Which also makes them terrible platforms for firing cannons from BTW). And if you don't think traction is important (which it is) try taking a sharp corner on an icy road at high speed. Better yet, don't try, just trust me on this. Most of the time traction is a good thing!

For these reasons no country on Earth has ever produced a heavily armored combat hovercraft

What hovercraft are good at is what the US used them for approaches to landing zones from the sea. Plus as transports for crossing soft/marshy/watered terrain.

So you could create two types of military hovercraft;

(1) High speed/large volume military transports and;

(2) High speed, lightly armored missile/light cannon armed attack craft or Edit: (I forgot to add APCs)

But no tanks.

Answer 11

The long, straight treads of a tank mean that the tank sits on a tangent line to the surface of the ground below it. When traveling up or down a hill, the body of the tank will pitch up or down accordingly. This limits the operator's visibility as well as the weapons' field of fire.

A hovering tank has the potential to traverse sloping terrain while remaining level. Going down a hill no longer means that you're staring at the dirt at the bottom, or going uphill no longer leaves you watching the birds. You can keep your eyes and weapons focused where they need to be, regardless of what you're driving over.

Even though your hovering system is complex, it doesn't have moving parts like a tracked tank does. Moving parts are always the first to wear out, so eliminating the friction and mechanical wear of tracks/wheels might actually improve your reliability.

Answer 12

So long and tanks for all the friction is what caterpillar tracks would sing if you decided to get rid of them. At face value, hovertanks are much cooler than they are practical.

While a hovertank's locomotion would lack friction, it's as big a strength as it is a weakness. With arbitrarily advanced technology, a hovertank can be arbitrarily heavy and fast, so arbitrarily hard to direct and stop. Remaining stable and accurate when you shoot would be an issue, whereas a regular tank is always the same height and direction, a hovertank's position can vary. Assuming you can anchor your tank when shooting your cannon or getting shot. It won't do you any good against mines, because we would definitely start using anti-hovertank mines as soon as apossible.

You could use hover tanks in really bad terrains, like thin ice, swamps, fording rivers every twelve seconds, and such. Something a flying death machine would be just as capable of. And unlike hovertanks, Unmanned Combat Aerial Vehicles aren't scifi. So unless your typical battlefield consists of 100% dog-awful terrain where air support is consistently compromised, hovertanks aren't really useful.

So does that mean hovering is useless? No. Hovering can still be leveraged... for support roles.

Artillery

There are other cannon-delivery vehicles than tanks. Here, you aren't going to have an armour problem because artillery cannons aren't really armoured, by design. They're not battlefield units, they provide firepower from the safety of far away. But you still need to move it in position, and this is where hover can open new and interesting tactical options.

Suddenly, your artillery support can be placed anywhere on the map, provided the destination has solid-enough ground. Want to put your cannons on the mountain? Hover it there, plop it down securely, and start shooting.

Redefining heavy

I think the overlooked strength of hover technology is to make heavy things lighter. This is getting a bit outside the frame, but I want to give you hoverthings, even if they're not hovertanks.

Putting things on a hovertrailer means you can start lifting heavier things. You don't even have to get rid of the wheels, adding some hover-assist already helps a heavy vehicle cross terrain that would otherwise ensare it. You could imagine regular trucks pulling hovertrailers or hover-assisted trailers, capable of moving heavier loads, provided you remember to give it good brakes.

Hybrid vehicles would certainly be more complex and more expensive, but it's worth it if enables you to do thing no other vehicle can. Wars are won and lost through logistics. If you can ford hybrid tanks through the swamp, that's a valuable tactical option. If you can move more troops with a hovertrailer truck, that's an edge.

You could even imagine smaller hovercarriers. Like Boston Dynamics' Big Dog, but without legs and floating. Imagine what applications Hover Dog (™) could be used for. Suddenly you don't need two blokes just to carry one wounded guy to the back. Carrying ammo and heavy guns in combat becomes easy. And you don't need to worry about it getting stuck in the terrain, because it gently floats above.

I know it's not as cool as tanks, but this is practical.

Answer 13

Landmines

Hovercraft don't set off landmines, even when using a low weight setting. See Mythbusters.

Your world is a firm believer in scorched earth. Landmines have been left behind from every major war and minor skirmish for hundreds of years. Except for population centers and farms which have been demined at great expense most of the land is unusable due to this - unless you have a hover-tank.

Answer 14

Well, since the hover tank is appliying such force in the direction of the ground in order to "levitate", it would require an immense amount of energy. It would be better to just put its weaponry in a helicopter or plane and go in your merry way.

However, maybe you could make a metallic "boat" that would be pushed by the propulsion of a turbine in the horizontal. This way you wouldn't need to actually levitate.

However, you still would need a lot of energy to move its heavy body, it could be an all-terrain light/scout tank, specially made for ambients that aren't suitable for average tanks, like swamps. After all, the best way of travelling through a swamp is not travelling through a swamp (I think).

Also, it would move a lot of dust, making it spot-able from high distances.

Answer 15

Marines would be the immediate highest bidder for your hovertanks. Why bother with a dangerous docking maneuver or loading tanks onto a boat? Use the tank as a boat. This probably cause a lot of amphibious assault ships to be refitted for fast deployment and loading of hovertanks.

A hovertank will have better agility than a traditional tank - able to turn quickly and dodge sideways. Hovertanks also have the advantage on extremely uneven terrain and mountains - anything impassable by a typical wheeled or tracked vehicle.

Recoil problems can be sidestepped with smarter arms loadout. Swap out the traditional cannon for an EMP emitter that will instantly fry anything dependent on electronics (just about any modern military vehicle) - with no recoil. Get rid of the typical vehicle-mounted LMG and put a rapid-fire laser in the anti-personnel hardpoint - again, removing recoil and ditching ammo weight. Conveniently, this saves a lot of loadout space and weight for an extra-large generator which you probably needed anyway. Use some of the saved space for a missile rack to take out enemies outside line-of-sight.