CT Only: Do Grav "Tanks" look like Tanks?

[McPerth]

And is there any other increments or is 50% available out to 100+ diameters?

Again, I'm no science/physics whiz, but wouldn't a drive working at 1G near the surface need to work far harder than one out at 10 diameters where the gravity is much less. Thus the 50% reduction in max power would not be much of an issue?

Neither I am, as said, and I'm talking from the Traveller rules POV. Those rules are for gravitic drives in space )as opposed to thruster plates) in MT, as said, not being sure of what happens to gravitic plates (as opposed to drives) when far from a gravity well, but I've always understood gravitics (both, plates and drives), unlike thrusters, need to push against some gravity well to work.

 

[pendragonman]

Neither I am, as said, and I'm talking from the Traveller rules POV. Those rules are for gravitic drives in space )as opposed to thruster plates) in MT, as said, not being sure of what happens to gravitic plates (as opposed to drives) when far from a gravity well, but I've always understood gravitics (both, plates and drives), unlike thrusters, need to push against some gravity well to work.

It is somewhat explained in T5 with the gravitic drive. Out to 10 Ds, full thrust, passed that efficiency drops to 1 %. Not enough gravity out that far to manipulate effectively.

 

[Timerover51]

Neither I am, as said, and I'm talking from the Traveller rules POV. Those rules are for gravitic drives in space )as opposed to thruster plates) in MT, as said, not being sure of what happens to gravitic plates (as opposed to drives) when far from a gravity well, but I've always understood gravitics (both, plates and drives), unlike thrusters, need to push against some gravity well to work.

First, you have the gravity well of the planet that you are departing, then you have the gravity well of the star around which that planet is orbiting, which is sufficiently strong so as to keep that planet in orbit around said star, then you have the gravity well of the galaxy which is keeping all of the stars orbiting the Galactic Core, and you finally have the Universal Gravitation constant.

Also, by 1-G acceleration, it means that you are supplying sufficient force to a mass to accelerate it at the rate of 9.81 meters per second per second or 32.174 feet per second per second. It has nothing to do with the gravitation field that you are in.

It is somewhat explained in T5 with the gravitic drive. Out to 10 Ds, full thrust, passed that efficiency drops to 1 %. Not enough gravity out that far to manipulate effectively.

What do you mean that T5 says that beyond 10 Diameters the efficiency of a gravitic drive would drop to 1%? The Earth's Moon is about 30 Earth diameters away from the Earth. The Earth possesses a sufficiently strong gravitational field to retain the Moon in orbit against the gravitation pull of the Sun at that distance. Also see the discussion of the Lagrange Points here, where the interaction of the Earth's, Moon's, and Sun's gravitational fields creates a stable volume in space for orbit:

http://en.wikipedia.org/wiki/Lagrangian_point

Also, in accelerating to that 10D distance, you build up a considerable velocity, which does not go away simply because you stop exerting a acceleration force. Assume that, based on Starter Traveller, you boost for 1-G for 2000 seconds to reach a distance of 10,000 kilometers from a planet's surface. That 2000 seconds of 1-G boost gives you a velocity of 19.62 kilometers PER SECOND, or 70,632 kilometers PER HOUR. If all you do is coast from that point, supplying just enough force to counteract the slowing of the ship by the planetary and stellar gravitational fields, you will reach your safe Jump Point at 1,280,000 kilometers distance from the planet in about 18 hours, 7 minutes, 20 seconds. That does assume no turnover and deceleration to have essentially zero relative velocity at the jump point (you do not really have zero velocity, but explaining that gets a bit complicated).

However, if your gravitic drive does become basically ineffective at a distance of 10 diameters from the departure planet, and you have to arrive at the target planet 100 diameters distance, HOW DO YOU GET TO THE ARRIVAL PLANET? According to your statement of the rules, YOUR DRIVE DOES NOT WORK. For that matter, how do you decelerate at all once you are halfway to the jump point?

Accelerating at 1-G to your 10 diameter distance from the Earth, when you reach that point 128,000 kilometers from the surface, you have been boosting at 1-G for 7,224 seconds, or a fraction over 2 hours. You are traveling at over 70 kilometers PER SECOND, or over 250,000 kilometers PER HOUR. Your drive no longer works effectively. HOW DO YOU SLOW DOWN?

If, in fact, the T5 rules really state that beyond 10 diameters from a planet, your drive works at 1% efficiency, then there is a MASSIVE problem with how the gravitics drive is described at working, which needs to be either fixed or simply dropped from further consideration.

 

[McPerth]

However, if your gravitic drive does become basically ineffective at a distance of 10 diameters from the departure planet, and you have to arrive at the target planet 100 diameters distance, HOW DO YOU GET TO THE ARRIVAL PLANET? According to your statement of the rules, YOUR DRIVE DOES NOT WORK. For that matter, how do you decelerate at all once you are halfway to the jump point?

Accelerating at 1-G to your 10 diameter distance from the Earth, when you reach that point 128,000 kilometers from the surface, you have been boosting at 1-G for 7,224 seconds, or a fraction over 2 hours. You are traveling at over 70 kilometers PER SECOND, or over 250,000 kilometers PER HOUR. Your drive no longer works effectively. HOW DO YOU SLOW DOWN?.

Mainly by not using gravitic drives for crafts thought for those situations.

In MT, most of those crafts would use thrusters (if at high enough TL) of fusion rockets to keep acceleration outside the gravity well. In T5 IDK, as I have not read it.

That's why I said that gravitic tanks (and vehicles in general) will be used in gravity, not in zero-gravity or microgravity. After all, they are planetary vehicles, not space crafts.

 

[whulorigan]

First, you have the gravity well of the planet that you are departing, then you have the gravity well of the star around which that planet is orbiting, which is sufficiently strong so as to keep that planet in orbit around said star, then you have the gravity well of the galaxy which is keeping all of the stars orbiting the Galactic Core, and you finally have the Universal Gravitation constant.

Also, by 1-G acceleration, it means that you are supplying sufficient force to a mass to accelerate it at the rate of 9.81 meters per second per second or 32.174 feet per second per second. It has nothing to do with the gravitation field that you are in.



What do you mean that T5 says that beyond 10 Diameters the efficiency of a gravitic drive would drop to 1%? The Earth's Moon is about 30 Earth diameters away from the Earth. The Earth possesses a sufficiently strong gravitational field to retain the Moon in orbit against the gravitation pull of the Sun at that distance. Also see the discussion of the Lagrange Points here, where the interaction of the Earth's, Moon's, and Sun's gravitational fields creates a stable volume in space for orbit:

http://en.wikipedia.org/wiki/Lagrangian_point

Also, in accelerating to that 10D distance, you build up a considerable velocity, which does not go away simply because you stop exerting a acceleration force. Assume that, based on Starter Traveller, you boost for 1-G for 2000 seconds to reach a distance of 10,000 kilometers from a planet's surface. That 2000 seconds of 1-G boost gives you a velocity of 19.62 kilometers PER SECOND, or 70,632 kilometers PER HOUR. If all you do is coast from that point, supplying just enough force to counteract the slowing of the ship by the planetary and stellar gravitational fields, you will reach your safe Jump Point at 1,280,000 kilometers distance from the planet in about 18 hours, 7 minutes, 20 seconds. That does assume no turnover and deceleration to have essentially zero relative velocity at the jump point (you do not really have zero velocity, but explaining that gets a bit complicated).

However, if your gravitic drive does become basically ineffective at a distance of 10 diameters from the departure planet, and you have to arrive at the target planet 100 diameters distance, HOW DO YOU GET TO THE ARRIVAL PLANET? According to your statement of the rules, YOUR DRIVE DOES NOT WORK. For that matter, how do you decelerate at all once you are halfway to the jump point?

Accelerating at 1-G to your 10 diameter distance from the Earth, when you reach that point 128,000 kilometers from the surface, you have been boosting at 1-G for 7,224 seconds, or a fraction over 2 hours. You are traveling at over 70 kilometers PER SECOND, or over 250,000 kilometers PER HOUR. Your drive no longer works effectively. HOW DO YOU SLOW DOWN?

If, in fact, the T5 rules really state that beyond 10 diameters from a planet, your drive works at 1% efficiency, then there is a MASSIVE problem with how the gravitics drive is described at working, which needs to be either fixed or simply dropped from further consideration.

In T5, the Gravitic G-Drive and the Grav-based Maneuver Drive (M-Drive) are different drive systems. The G-Drive drops to 1% efficiency beyond 10 diameters from a massive object. It has an internal Cold-Fusion power cell that powers it - it needs no independent supporting Power Plant (and is refuelled yearly during annual maintenance).

The Grav-based M-Drive "grabs onto" and rides the curvature of spacetime. It is effective to 1000 diameters from a massive object (beyond which it drops to 1% eficiency). The M-Drive does require an independent supporting Power Plant for operations - it is NOT independently self-powered.


G-Drives are typically used by Small Craft and other short range orbital vessels. Long Range vessels normally use M-Drives.

 

[aramis]

Timerover -

The drives, at 1%, are still effective provided one isn't falling straight at the world. It's about 18.5° of arc if I did the math right, so a 1/9 x1/9 chance, or 1/81 chance, that you're going to get dropped aimed at the planet.

So, as long as you're not aimed at the planet, 0.01G is plenty to circularize your orbit.

Keep in mind: the Deep Space 1 probe broke earth orbit with about 0.001G peak... and became the fastest moving man-made object ever.

 

[McPerth]

And don't forget that, before hiting any planet, they will go into its 10 radi treshod and regain its full thrust to stop themselves...

 

[McPerth]

I expect combat gravs to commonly have 3 basic hullforms... in a CT/MT/T20/T5 TU

Tank-like - because it's pretty well optimal for surface-hugging ops in support of ground forces. Low, slow.

Helicopter Gunship like - Take an AH64, pull the rotors and replace with grav. Medium speed, medium agility.

Airplanes. With 1G lift, and the rest into forward thrust. As it speeds up, the airfoils take over the lift, and the lifter shifts to aft thrust mode... faster than the other modes. Long and skinny, probably staggered biplane wings (which have been noted as being more mass-efficient in IIRC Popular Mechanics). Not terribly agile, but blindingly fast. Lands like a helo (except in emergencies, when it can glide in), flies like a jet. Used Air-to-Air, and for some Air-to-Ground roles.

In a TNE setting... due to the different nature of gravitics, you get mostly tilt-pod and vectored thrust aircraft; most look like variants of the AV-8B or the Osprey, but can rotate over much faster. Essentially, in TNE, you cannot replace the thrust agency modes, but you can do more with them. So, the airplanes have 747's with a 100m take-off roll, and harriers that pull a full 2g's straight up. You add wingless harriers to the mix, too, as the vectored thrust is plenty to lift 2% of the craft mass.

Well, I was refering to tanks proper (and APC/IFVs too). Off course other crafts more akin helicopter gunships or speeders to be used both for air superiority or straffing would exist, but its use would be, IMHO, more limited, due to the high lethality and precisión of the anti-air weaponry.

As someone said in other posts, at those TLs, you main survival strategy is bein undetected, and this is quite difficult for something flying over NOE.

 

[salochin999]

The way I treat grav is a power plant creates a field and that field can be polarized to use the gravity vector being applied to the ship so instead of pulling straight down it can be angled including straight up.

Grav, manouver and jump all work the same way but needing bigger fields and thus bigger power plants to generate the fields: grav only works well near a planet, manouver near a star, jump star to star.

As TL improves the total vector available increases, the drop off with altitude decreases and the ability to angle the field to get directional thrust (apart from straight up or down) improves.

So they start off like a hover version of a standard tank, thrust in any direction, vector movement, no high altitude, can fly over obstacles at the cost of reduced forward thrust.

http://neisbeis.deviantart.com/art/Tank-concept-280292254

Bit later can fly higher and faster so more of a flying tank than a hover tank.

http://drell-7.deviantart.com/art/The-Emperor-s-Lift-Cavalry-187001956

Next stage more of a gunship with multiple weapons, anti-air as well as ground and carrying a squad of infantry with armor and infantry merged into one.

http://s4.postimg.org/bkbab8fju/sttheo_01.jpg


Final stage might look like a mini spaceship

http://shimmering-sword.deviantart.com/art/Transport-Gunship-196333556

 

[Magnus von Thornwood]

My G-Tanks.

As I said in the previous thread, I see the grav tank to be more of a flattened egg, slathered in armor, point defense and a big spinal mount weapon. They can spin on their own axis, fly upside down (maybe, I am considering running with the popular yet non-canon DGP SOM thrusters, but I ain't married to them and I don't yet see a need for pineapple upside down tanks), and they are used to patrol or spearhead attacks. Return of the Land Cruiser!

I think I may have to sketch one up later.

 

[Timerover51]

Timerover -

The drives, at 1%, are still effective provided one isn't falling straight at the world. It's about 18.5° of arc if I did the math right, so a 1/9 x1/9 chance, or 1/81 chance, that you're going to get dropped aimed at the planet.

So, as long as you're not aimed at the planet, 0.01G is plenty to circularize your orbit.

Keep in mind: the Deep Space 1 probe broke earth orbit with about 0.001G peak... and became the fastest moving man-made object ever.

The Deep Space Probe was already in orbit, so already had a fair amount of velocity. Applying a small acceleration to an already orbiting object for an extended period of time will build up quite a high velocity. Your orbit just keeps getting larger and larger until you achieve escape velocity from that particular gravitational well.

Also, if your gravitic drive efficiency drops to 1% at 10 Diameters, it should be steadily dropping the entire time of boost, as the gravitation field is dropping as well.

I will stick with something on the order of the "Dean" drive, and restrict countra-gravity/gravitic lift plates to atmospheric operation only. They will help with the initial lift to orbit. Essentially, an H. Beam Piper approach.

 

[aramis]

The Deep Space Probe was already in orbit, so already had a fair amount of velocity. Applying a small acceleration to an already orbiting object for an extended period of time will build up quite a high velocity. Your orbit just keeps getting larger and larger until you achieve escape velocity from that particular gravitational well.

Also, if your gravitic drive efficiency drops to 1% at 10 Diameters, it should be steadily dropping the entire time of boost, as the gravitation field is dropping as well.

I will stick with something on the order of the "Dean" drive, and restrict countra-gravity/gravitic lift plates to atmospheric operation only. They will help with the initial lift to orbit. Essentially, an H. Beam Piper approach.

Pop out at 100D with any residual velocity relative to the world other than straight in (jump preserves vector), and you'll fall into an elipse with pretty good velocity, which you can circularize.

 

[Travellerspud]

....and then there are the "Banana Republic" version of grav tanks built at TL5-6 (or should I say grav aerial battleships) ala H.Beam Piper

*uses imported grav modules for lift only with local controls (agility is horrible and requires off-world techs)
*uses local propulsion methods (or 50:50 mix)
*chassis is locally made
*mounts a fixed-foward battle-ship grade gun battery
*lots of secondary and AA batteries
*can also carry parachute troops
*heavy enough armor to shrug off the common fighter/interceptor weaponry (and or common SAM's)

and of course - raw meat for high tech forces!

 

[Golan2072]

....and then there are the "Banana Republic" version of grav tanks built at TL5-6 (or should I say grav aerial battleships) ala H.Beam Piper

*uses imported grav modules for lift only with local controls (agility is horrible and requires off-world techs)
*uses local propulsion methods (or 50:50 mix)
*chassis is locally made
*mounts a fixed-foward battle-ship grade gun battery
*lots of secondary and AA batteries
*can also carry parachute troops
*heavy enough armor to shrug off the common fighter/interceptor weaponry (and or common SAM's)

and of course - raw meat for high tech forces!

I love this! Perfect for "Weird War II" stand-ins... :-D

 

[salochin999]

....and then there are the "Banana Republic" version of grav tanks built at TL5-6 (or should I say grav aerial battleships) ala H.Beam Piper

*uses imported grav modules for lift only with local controls (agility is horrible and requires off-world techs)
*uses local propulsion methods (or 50:50 mix)
*chassis is locally made
*mounts a fixed-foward battle-ship grade gun battery
*lots of secondary and AA batteries
*can also carry parachute troops
*heavy enough armor to shrug off the common fighter/interceptor weaponry (and or common SAM's)

and of course - raw meat for high tech forces!

excellent idea

 

[salochin999]

The other thing might be how do they look en masse if they were fully aerial?

Say doctrine was that a battalion attacks on a frontage of 1 km

http://balagan.info/infantry-unit-frontages-during-ww2

and say the grav battalions IYTU are 5 grav squads per platoon, 4 platoons per company and four companies per battalion that's 80 grav squads

so at say 50 m intervals between each grav that's a 4 high x 20 wide wall of something like this (IMTU)

http://s4.postimg.org/bkbab8fju/sttheo_01.jpg

coming at you all guns blazing if you're the defender.

That would be quite a sight.

 

[Meeko100]

I've massively twisted so much about MTU that this ma not be similar in anyway to OTU. Just a warning.

The way I see it, grav tanks, and grav tech in general, doesn't't scale down very well. It can generate 1-2 G's on a average man in a floor plate for spaceships, and can lift a tank of considerable weight off the ground, but they lack the power to go from ground to orbit with the weight of the armor and guns and such. They can fly maybe a good hundred feet off the ground of an 1-g world, but they are too heavy to manage greater flight unless they were specifically designed to pull it off, with wings and such. Or were on a planet with less gravity.

An air/raft can pull a ground to orbit off because its considerably lighter then a military vehicle, compared to the amount of force generated. A tank could float down safely from orbit, but it'd need some way to return. For the navy and marines, this is less an issue, seeing as you could simply send it down in a cutter, or pick it up after its got the objective with a cutter. Lots of ship carry them; even little couriers and free traders shove cutters or ship's boats in their bays. Surely a marine assault ship with g-tanks would have been wisely designed to have cutters built into it, knowing this issue.

So, under those rules I do see grav tanks turret up designs. On a particularly large world, the turret down designs may not be able to fire properly, where on small planets, a tank could adjust the angle of flight and pop a shot into the dirt if it has to. Or it could just lower altitude and then shoot whatever needs to not exist anymore.

But yeah... Like modern vehicles!

 

[Major B]

So how do Grav "Tanks" look like in YTU? Like flying tanks, like gunships, or like something else?

My take on military Grav vehicles is they have excellent operational and even strategic mobility but tactical mobility, while improved over tracked designs, is still limited by the lethality of guided weapons and lasers. So a grav force on one continent can load up and move to a trouble spot on another continent very quickly but once there the grav vehicles would be hugging the ground for protection and operating in a way that would be recognizable to a WWII armor veteran. Note that by recognizable I do not mean identical - think evolutionary rather than revolutionary.

If you keep those considerations in mind while designing a vehicle some interesting things come out. For example, this vehicle is designed for assaults from orbit. The idea behind it is to get close to the ground as quick as possible and then fight from there. The point defense weaponry is mounted in a chin turret like an AH-64 but the main armament is in a traditional top turret.

Other vehicles I have designed or invisioned blend the two forms to a greater or lesser extent depending on their intended purpose. I have some designs in the file library that range from light speeders that look the part (in my mind anyway - no artwork for these yet) to those that look more like a Trepida or Astrin.

Here is another related thought to consider: As grav technology matures over time, and vehicle designs change, and tactics change in response to new capabilities, how will crew roles and training requirements change? In the US Army a tank crew usually divides roles in this way: the most junior crewmember is the loader, next most senior the driver, next most senior is the gunner and the commander is seniormost. Sometimes loader and driver are reversed. Would this have to change as the driver becomes a pilot? In attack helicopters the pilots are the most senior but then again the comparison isn't exactly fair since helicopters combine pilot and gunner roles.

IMTU, the Imperial Marines follow more of a driver model where a junior crewmember is operating the vehicle while the Imperial Army (this is MTU) treats combat vehicle drivers more as pilots (to include having a warrant officer program for them to keep them stabilized in crews longer).

 

[samuelvss]

Join with Major B's comments, and add a bit.

It has been said that at some point, as armored vehicles fly, and flying vehicles become armored, they just merge.

IMTU, grav tanks are just that: tanks. Tanks use the protection of the ground to be able to concentrate more protection in a frontal arc, maximizing their protection there. By maximizing armor optics and tank-killing weaponry there, they become very specialized vehicles, optimized for their niche. They do well in "two-dimensional" fights. A "gunship" might be armored on all faces, or even more on the belly, to provide air support. Fighters and air defense keep enemy air off.

This not to say that IMTU grav tanks can't fly at essentially any altitude. When they do so, however, it is movement for the purposes of deployment, redeployment, or wowing kiddies at air shows; all presume the enemy is not within direct fire range with anything scary to the tank's belly plates.

IMTU, external grav thrust varies directly with the gravity of the planet, as does weight, of course. Mass, of course, remains static. Thus the grav vehicle's ability to support itself is the same, as it ascends, but its ability to accelerate decreases as it gets farther out of the gravity well.

 

[Condottiere]

Grav tanks would merge with attack helicopters; whereas gunships rely on the game mechanics of their space specced hulls and speed for protection, and their space specced weapons for lethality.