Hovertanks and Recoil (or Curling with Tanks)

[epicenter00]

I wasn't sure if I should post this in the COTI 2300 board or here, but as it's a technical issue, I decided to post it here instead. Note if you're playing "thrust plate" Traveller, this discussion can be safely ignored. If you're playing 2300 it's an issue. It's also an issue in Traveller:TNE as "thrust plates" aren't as convienent anymore and anti-gravity vehicles have similar issues to hover vehicles (see FF&S).

A little background:

In 2300, hover vehicles are a big part of the landscape of the game, fulfilling the "futuristic" flying-car niche left vacant by the lack of anti-gravity technology in 2300. But flipping through the old 2300 Vehicle Guide the other day, something occured to me - in addition to the fact that many (but not all) of the hovertank images in 2300 curiously lack any kind of propulsion fans and just have hover fans - it seems that many hovertanks mount high recoil weapons (plasma guns and large caliber mass drivers).

The problem:

Now, I remember reading something a while back that said that hovercraft are considered to be somewhat limited in real-world military utility due to their noise, their power consumption, their lack of mobility in broken terrain, as well as their tendency to "hockey puck."

For those who don't know, "hockey pucking" is a tedency for hovercraft to become the very model of Newtonian physics: As hovercraft ride a film of air partially contained in a plenum, they have very low ground friction - good for manuverability, bad for being a stable firing platform. When a hovercraft shoots a high-recoil weapon they skitter off very quickly in the opposite direction, in a similar fashion to the hockey puck used in air hockey. Apparently this problem is far more severe on hovercraft than it is even on helicopters or fixed-wing aircraft (I'm not sure how true this last part is but I would imagine the problem would at least be as bad).

While it's understandable that 'hockey pucking' would be less severe in forward-facing fixed mount guns (like the mass driver on the AC-8 hovertank) since the recoil would be counteracted by the forward momentum of the hovertank (or could be), how do turreted guns compensate against this?

Almost all of the "big powers" use hovertanks with large-caliber mass drivers, big plasma guns, and "gatling" guns - all weapons that would have serious impulse or sustained recoil. In almost all cases, they're turreted guns. For those unfamiliar with 2300, the game system lacks anti-gravity as well as intertial compensation (both of which I like - don't get me started on the implications of what you should be able to do with such mastery of inertia and gravity as in vanilla Traveller).

Solutions?

I've been thinking of some solutions to issue and before opening this up for feedback from board members, I thought I'd mention them:

1) You're right, epicenter00, it's not very realistic. Get rid of the high recoil turret weapons and replace them with low recoil weapons like lasers and recoiless (backblast) missile launchers. This is probably the easiest solution, especially for lighter hover vehicles. It lacks a certain artistry, though.

2) Countermass systems. Perhaps by shooting an equal mass of airgel or plastic flakes or whatever out from behind the turret, the recoil of mass drivers could be reduced to managable levels. I suppose the same could be done with plasma guns except I find the idea of constant puffs of plastic flakes shot out from high cyclic weapons like "tri-beamers" to be a humorous and less-than-cool image, like a tank spraying party streamers as it goes into battle.

3) Gyroscopic stabilization. This is probably the best bet (?). I'm no expert in physics, but I'm told that it is possible in theory to reduce or eliminate the recoil of high-recoil weapons by transferring the recoil energy to a gyroscope. I would imagine it would require a fairly good computer to do this, but is well-within the technology of 2300. But wouldn't the transfer of energy play havoc with the pre-existing velocity of the hovertank, as well as possibly overloading the gyroscope?

4) Fans or jets. Related to #2, computer controlled fans might be a solution. Mount them on the turret and key them to react to the firing of the weapon to compensate for the firing. The issue seems to me that it might require a large fan or fan array, and that "ramp up" time for fans would probably mean that the fans are reacting to the recoil after the fact as opposed to eliminating it before it affects movement too much.

5) Ducted Fans. It would require a total redesign of the tanks, but ducted fans mounted in manuverable nacelles/gimbles might be a solution, but would probably have the same issues as #4.

Any ideas?


* It's come to my attention that in FF&S for Traveller: The New Era, "thrust plates" are again reduced in profile so "hockey pucking" might be an issue for grav tanks in TNE as well.

 

[TheEngineer]

Hi !

Well, I really love thrusters and stuff, but general physics, too

A friend in duty in the German "Heer" told me, that the recoil of most modern artillery weapon system is quite controllable, e.g. by using stuff like "Mündungsbremsen" (dont know the english word for that). Essentially its a device at the end of the barrel, which redirects parts of the expanding gas into pendicular and backward direction in order to compensate backward momentum.
As you might want to see here
Recoil compensators...
it produces something with a "high signature"

Perhaps you could assume, that "lets kill each other" technology has also improved to 2300, so that recoil compensation without g-gimmicks is just no problem any more....

Could You provide some stats for such a 2003 hovertank ?

regards,

Mert

 

[epicenter00]

Mündungsbremsen would be "Muzzle Brake" in English.

As mass drivers use magnetic induction to move their shot as opposed to chemical propellants, muzzle brakes wouldn't be useful on mass drivers.

Stats would be along the range of a mass of 10000kg ~ 12000kg, moving at a maximum speed of 200 ~ 220 KP/H. Their turret guns tend to range from the 6cm ~ 7cm range with a useful range of 2km or so and can fire once even 5 seconds or so.

Alas, I don't think the 2300 designers had an actual system to build this stuff. Most 2300 ranges are extreme by half, but even then, I can't imagine a tank with such a weapon being very stable without some sort of compensation.

 

[Todg]

Soft recoil (AKA differential recoil) weapons might help. In these weapons, the barrel and breech are held to the rear (typically) under sping tension. On firing, the barrel and breech are relased and fly forward, with the round actually being discharged when the moving mass reaches maximum forward velocity. The recoil generated by the projectile must first overcome the forward momentum of the gun.

This system is currently in use with the XM307 ACSW, XM312 and XM204. It was probably first used in the French 65mm mle.1906 mountain howitzer.

 

[Merxiless]

Land the tank and fire?

I'd say the design should follow military efficiency. if recoil is a problem, use recoilless weapons, like lasers.

There's no need for artistry, if the job is butchering humans, Silence of the Lambs notwithstanding.

All this talk of fans and jazz to compensate.. it's just more stuff that breaks down.

Big guns obviously won't work. This is why you don't mount a .50 on a rowboat.

So use a laser, or use it for Transport, or have it be a light-weight forward firing weapon only.

Alternatively, some kind of box launcher rocket system would seem to work well, as would a lighter missile, I think.

 

[Crashlogic]

Well to my mind simple thrust compensation works well enough. I never did get the point of turrets on grav vehicles. Direction of travel can remain constant even if the vehicle is facing sideways...it floats on a grave cushion and can turn on a dime. simply have the vehicle thrust in the direction of fire, in combination with any other recoil compensation system.

 

[Fritz_Brown]

But, Crashlogic, these aren't grav vehicles. They're aircushion-driven.
(Though you have a point about turrets.)

 

[mbrinkhues]

From my understanding the 2300AD "hover" tanks are closer to a "Harrier with Kilt" than to the classical hovercraft.

They use MHD-Turbines for power and in 2300AD MHD-Turbines with an expansion chamber are the ground-to-orbit engines so the Hovertanks are jet-driven, not prop-driven. This also matches with the "JumpJet" mode that the hovertanks have.

I always asumed that they had 4-8 vectored thrust nozzels under that skirt and used computer control to compensate for the gun firing as well as the tendency to follow contours.

Besides, 2300AD is simply not right without a company of LuKi IXs smashing through the french lines near Sedan.

 

[aramis]

For really big guns, the craft can add ...

plenum diverters: gates that vent some plenum pressure out the back of the turret, bringing the skirts down slightly.

under the skirt dig-in jacks: not good for light stuff, but really big stuff can use these to be hull-down and recoil spaded simply by cutting plenum pressure at low speeds. This can be hell on the crew, however, at speeds over 20 KPH.

 

[epicenter00]

Thanks everyone for these great ideas and suggestions. Keep them coming if you have any more!