Advanced grav tanks - why do they have turrets?

[l_c_jackson]

I am not generally a boring gearhead, nor am I entirely obsesses with military technology (honest!), but something about the standard TL15 grav tank designs just baffles me. I've had a look for previous references to this and not found any, but apologies if I have missed anything.

Why would anyone want to spoil the aerodynamics of a high-speed, highly agile vehicle, increasing the cost, production time, weight and height and decreasing the reliability, by sticking a turret on it? You couldn't use a turret mount pointing sideways when the grav tank was moving at high speed, as the air resistance would slew the vehicle round, possibly causing a fatal loss of control and a crash. At very high speeds air resistance might even snap off the barrel.

For use at lower speeds, it would make sense either to mount the gun directly onto the hull externally (either with a limited traverse like a WWII tank destroyer, or entirely fixed to the hull) or internally (like a mini-spinal mount, firing out of the front of the hull). The proposed external gun "grav tank-destroyer" design would have the advantages if cheapness, simpler design, faster production and improved reliability. On top of those, the alternative grav tank with an internal spinal mount would have a lower profile and would protect the main weapon from attack.

OK you say, what about the problems of shielding the crew from the main gun's heat, noise and radiation, and what about access for maintenance? Well those must have been fixable in large spacecraft for the canonical Traveller spinal mount, so why not for a grav tank? If those solutions cannot be applied to such a small vehicle, ruling out a grav tank spinal mount, a grav tank-destroyer design could retain the external gun mount and yet still have the advantages above.

The only reason I can think of for a turret mount on a vehicle that can spin round at low speeds is that it places the weapon on top of the vehicle, for a better line of fire. However a grav tank with a spinal mount would have the option of "popping up" briefly above surounding terrain (as attack helicopters do) to take a shot at a target already detected by sensor pods extending above the vehicle, or from remote sensor data. The proposed grav tank-destroyer alternative would still have the gun mounted on top of the vehicle.

My suspicion is that the designers of the advanced grav tanks and APCs have just copied the designs of tracked vehicles, which cannot spin round in the air, and based their "futuristic" designs on a system that doesn't make sense with Traveller technology. You can understand why the early grav tanks might follow the design of tracked tanks, but surely that would disappear as they became faster and more agile?

Would anyone like to shoot me down in flames on this?

 

[Andrew Boulton]

Turrets let you engage targets without having to change the direction of travel.

 

[mike wightman]

IMHO the designers of grav tanks made the error of thinking of them as flying tanks rather than heavily armored helicopters - which is the closes analogy to the grav tank.

Imagine an Apache with the armor of an Abrams.

 

[Hyphen]

Dear l_c_jackson -

You've mentioned the meta-game reason: something with a turret is recognisably a tank, therefore that's how it gets drawn.

Now for some speculation: a turret may make a tank more flexible. Fow example, it can point it's bow armor (heaviest) at one threat while slewing the turret to fire at another. Maybe the turret can be turned faster than the tank (G-forces on the crew? but they should be negated by inertial dampers, so *that's* not a good reason). However, if a high-speed tank sees a target to one side, turning the turret may be easier than the entire tank body. How about being able to allow a disabled tank to still track targets and fire?

Apart from those couple of reasons, I dunno. My dislike was more that many are drawn with obvious shell-traps (can't remember if that's the right word for "big nooks and crannies that will trap an incoming round and give it a better chance of penetrating"). %-(

FWIW, the meson sled does not have a turret, it's more like the Jagdpanther (I *think* that's the one I mean: fixed, forward-firing BIG gun?). So if fits your model.

BTW, popups are canon until TL 13+, when point-defence fire control becomes good enough to "pick off" vehicles performing popups. After that TL, it's hug the ground, likethe grav tanks in Ground Control (the most Trav-like ground combat sim I have ever seen).

One last point: I have no objections to having multiple turrets on a tank - like on a WWII bomber. This would allow you to use the rapid-pulse-Y on aerial targets, the Z-gun on a tank, and the starship fusion gun on... sorry, I was getting carried away, thinking of the Belion: http://members.tip.net.au/~davidjw/tavspecs/trendi/belion.htm.

 

[far-trader]

Turrets are still going to be useful and used imo as they allow continual engagement while the vehicle itself maintains it's own independent speed and evasion. The grav tank will zip along in it's NOE flight plan while the turret tracks and fires multiple times on the same target or engages multiple targets.

Imagine an Apache with the armour AND main gun turret of an Abrams :devil:

I don't think the air-resistance will be enough to worry about snapping the barrel, nor overcoming the momentum of the grav tank enough to slew it beyond what the gravitics can easily compensate for.

As for the bullet traps, yeah, some of the drawings are bad that way. I always put it down to sensor deflection trade offs and other compromises.

Another turret advantage I've seen and used is multiple armaments for the same chassis. Makes the actual designing easier and the logistics in game gain as well.

 

[BlackBat242]

As well as the high probability that even at TL 15 a turret can be aimed more accurately and quickly than the whole vehicle (important for those kilometer+ range weapons).

Also the comments of Hyphen & far-trader... off-vehicle-axis shots are far more common in real armoured warfare than those on or near the vehicle's front-rear axis... mainly due to multiple threats and obstacles that restrict vehicle travel.

While grav tanks can lift above most obstacles, and thus have a greater degree of maneuver freedom, trying to slew the entire vehicle at high speed could be disastrous... while slewing a properly-designed turret would have minimal effects.

The turret can also be trained on target much faster than the whole vehicle... essential for survival (kill the enemy before he kills you?). Armoured combat does NOT happen slowly... not since WW2, anyway.

An alternative would be to fit the vehicle with multiple weapons in barbettes mounted on all sides... but that would take up significantly more volume & weight than a turret (and thus drive up the size of the vehicle) as well as costing much more.

Do you want 10 "grav battleships" or 20 "grav cruisers"? Especially if the speed, armor, and main weapon ratings are the same?

 

[Gadrin]

Probably because it's a game.

I think one of the covers of GURPS Traveller books features a guy holding
a mini-lightsaber (or something). There are no lightsabers in GURPS
Traveller so...

Loren once mentioned that it was general consensus that in the future
an egg-shaped craft would probably be the ultimate design for attack
ships.

There are some egg-pods in the Emperor's Arsenal in T4.

So take it with a grain of salt.

Tech level 15: Gunships mounting rapid pulse X guns and heavier Z guns are
[COLOR=#ff0000]virtually indistinguishable from orbital craft[/COLOR]. Lower performance personnel
carriers mount rapid pulse X and Y guns and missile systems.

I suppose orbital craft might have turrets on them if they look like
merchant starships

I think of the Fiery-class myself.

Let's put it this way: if the players made a stink about turrets I'd
get rid of them. If they don't and we can can have a good session -- does it really matter ?

>

 

[AndrewR]

...You couldn't use a turret mount pointing sideways when the grav tank was moving at high speed, as the air resistance would slew the vehicle round, possibly causing a fatal loss of control and a crash. At very high speeds air resistance might even snap off the barrel.

I very much doubt you'd slew your turrets while going _that_ fast. While speed saves, there's a trade off point where you're too predictable a target because you loose maneuverability going so fast. High speed let you deploy, re-deploy and exploit breakthroughs quickly, but when the fusion bolts start zinging in, you slow down, drop low, and only dash from cover to cover.

Also: from a damage perspective putting your weapons in a separate section that you can expose separately from the main crew compartment means you can survive hits that a 'spinal-mounted' tank wouldn't since you'd have to expose the entire tank to fire.

Modular turrets also let you field different weapon systems while keeping design costs down.

Anyway, my 0.02cr...

 

[Whipsnade]

Gents,

Does anyone envision grav "tanks" routinely fighting at hyper or even supersonic speed? Does anyone envision them behaving in battle like current day combat aircraft? Even at rather low altitudes? Is TL15 avionics suite going to allow you to zip at 500kph a meter off the deck?

I'd say no to all those things.

We're already seeing the beginning of the "end" of manned tactical aircraft with more survivable, more agile, and much smaller drones filling more and more roles. The higher you fly - no matter what speed - the easier it is to already kill you and when long range energy weapons enter the mix it's going to be more a case of "You Fly, You Die" than ever before.

Grav tanks look like tanks because they fight like tanks. They don't flit about the battlefield like helos or A-10s on bennies because that's the best way to get killed by either tac-missile or energy weapon. Instead, they hug the ground, look for hull down positions, and sprint between them as others wait on overwatch just tanks have done since the middle of the last century.

Yes, grav tanks can deploy from orbit. Yes, grav tanks can sprint across continents and oceans as they move from theater to theater and front to front. However...

... they move like tanks and fight like tanks when they reach the point where the enemy can fire on them. Once they can be targeted, once enemy sensors enter the picture, even the relatively low altitudes that NOE high grav speeds require is far too dangerous a risk. Even with gravitics, a tank can't outrun or dodge a tac-missile let alone beam of coherent light, plasma, or mesons.

Form always follows function. Grav tanks look like tanks because grav tanks fight like tanks.


Regards,
Bill

 

[aramis]

Bill, go take a look at how combat helos fly and fight. Often below treeline, and often at 100mph+... sometimes both at the same time.

A grav tank is a superheavy apache that doesn't have rotor vulnerabilities & noise.

Yes, a Trepida SHOULD be fighting much like an Apache...

That's how I used them as a GM, and how players have used them IMTU. And the rules support using them that way.

 

[Whipsnade]

Bill, go take a look at how combat helos fly and fight. Often below treeline, and often at 100mph+... sometimes both at the same time.

Aramis,

Apache's don't face energy weapons and don't fly at 600mph+ NOE either.

A grav tank is a superheavy apache that doesn't have rotor vulnerabilities & noise.

The lack of rotors and noise is inconsequential when dealing with TL15 sensors.

Yes, a Trepida SHOULD be fighting much like an Apache...

If it flies anywhere near as high as an Apache, it's dead.

That's how I used them as a GM, and how players have used them IMTU. And the rules support using them that way.

Striker treats them as tanks because they are tanks. Fly too high and too many people can "see" you. When too many people "see" you, you are dead.

Grav tanks are tanks and are thus shaped like tanks. Form follows function.


Regards,
Bill

 

[Andrew Boulton]

Grav tanks look like tanks because they fight like tanks.

With Challenger 2 (other modern MBTs will be similar), while the Gunner engages target #1, the Commander uses his sight to find target #2. He then passes it to the Gunner, automatically swinging the gun round to engage it. This is much easier with a turret, especially on the move.

 

[veltyen]

Gents,

Does anyone envision grav "tanks" routinely fighting at hyper or even supersonic speed? Does anyone envision them behaving in battle like current day combat aircraft? Even at rather low altitudes? Is TL15 avionics suite going to allow you to zip at 500kph a meter off the deck?

Yup. But more for narrative reasons. Ultra fast low altitude tanks are cool. Cool trumps realistic.

I'd say no to all those things.
We're already seeing the beginning of the "end" of manned tactical aircraft with more survivable, more agile, and much smaller drones filling more and more roles. The higher you fly - no matter what speed - the easier it is to already kill you and when long range energy weapons enter the mix it's going to be more a case of "You Fly, You Die" than ever before.

At that point you are leading to nanoswarm warfare (see Diamond Age, amongst others).

However in a universe where ranks of uniformed men man turrets familiar to a B17 crewman in spaceships hundreds of metres long, and where the few, the proud, the marines run at the enemy in hightech powered armour wielding glorified metal clubs arguing from realism and derivation from the modern day doesn't overly make sense.


IMTU grav tanks are diamond shaped, with the main gun mounted spinally. The simplicity in armour and the advantage of cross section more then make up for the loss of the (main[1]) turret. I also allow directional grav thrust - meaning that you keep your vessel pointed at the biggest threat firing constantly even when traveling obliquely to the target.


[1] Anti personal, light weapons, and AMS are on turrets - multiple smaller turrets.

 

[Gadrin]

A grav tank is a superheavy apache that doesn't have rotor vulnerabilities & noise.

 

[veltyen]

Thanks for the link to the 3drt site.

http://www.imdb.com/title/tt0388349/ (where that particular tank is from)

Wow.

Just wow.

 

[Klaus]

Well, I always thought it a little odd that a flying tank has its turret on the roof.

At high TLs, we cannot really say for sure that a turret will turn faster than a grav vehicle can spin. Turrets are heavy, require lots of machinery, and can fail.

Even if a grav tank can fly supersonic with some kind of jet, it will be able to fly sideways at 'tank' speeds.

What about anti-'tank' gunships - high speed attack craft with fixed mounts. Especially good in ambush against the tanks while they are flying at high-ish speed to the battlefield, rather than ground hugging when they get there.

Also, what about asymmetrical warefare. Most conflicts in the OTU (at least) will take place with small numbers of high tech vs high numbers of mid-tech, so various tank designs will be optimised for that - more like Spectre gunships - large craft that can loiter while their belly turrets savage the defenceless enemy below - maybe even carrying troops to mop up afterwards.

One last thing - with a laser, the only thing that needs to be in a 'turret' is the aiming mirror...

 

[Gadrin]

Thanks for the link to the 3drt site.

http://www.imdb.com/title/tt0388349/ (where that particular tank is from)

Wow.

Just wow.

It had the two-man canopy like a helo-gunship so I felt it fit.

>

 

[Gadrin]

One last thing - with a laser, the only thing that needs
to be in a 'turret' is the aiming mirror...

Right.

It seems the main Fusion Gun will be used at stand-off distances anyhoo
depending on how much power the gun requires; since it does no good to fly
into an area where you can only shoot every 30 seconds

Laser Periscopes in GURPS are very handy (you can build robots like the
Boomers from Bubblegum crisis that shoot out of their mouths, so the
laser-carbine is concealed in the body/torso to appear normal.

Anyway, a gunship with a Fusion gun and some NPUs or RTGs to handle point
defense lasers, say a pair of Laser Periscopes on each side, it uses the main
gun, then cruises in close and pulse-blasts the "leftovers" with rapid fire
laser bursts, still big enough to be considered laser cannons. I think in
GURPS those point defense laser cannons can shoot 8 or 8+ times per second
for each weapon.

>

 

[Greylond_Aston]

People keep comparing it to an Apache. FYI, the Apache as a Gun Turret mounted underneath the nose. It has a +/- 100 Degree traverse(that's off centerline, so that means it can traverse 200 Degrees).

Source;
http://www.aviationphotoalbum.com/H...ecifications/AH_64_Apache_Specifications.html

 

[l_c_jackson]

Thanks everyone - you've convinced me I was wrong.

Thanks fellow Citizens, you've convinced me that I was mistaken. That was a though-provoking discussion.

Can I also say what a great site this is, having pointed me to Copplestone Castings miniatures and the fantastic Traveller Trailer on youtube (thanks Andrew, you deserve a medal for services to Traveller).

Finally, apologies to any real "gearheads" I may have offended in my initial posting! I'm glad I took the plunge and embraced my own "inner gearhead".

I've enjoyed this first contact with CotI so much, I'll be back for more later.

Cheers, Lindsay Jackson.