Scenario: SW Galactic Empire vs. WH:40K Imperium of Man

[Connor MacLeod]

Enough to shake a 2,500-tonne Warlord class Battle Titan, despite the inertial dampeners.

Okay, so we might be talking some millions of tons of newtons of force (about consistent with what their tank cannons probably generate IIRC) possibly. (Maybe hundreds of thousands of newtons.) Now, the amount of force applied by the blast wave is going to depend as well on the profile of the tank (the surface area) - what are its dimensions, and what was the facing?

The Warhound was just outside the main Titan pens, outside the crater but within the nuke's blast radius. Its legs were damaged and it was partly buried, but the chassis itself was mostly intact.

Not that bad for an unshielded scout Titan.

So probably no closer than 1-2 km, but no farther away than 30 km. Was it in front of the facility or behind it (relative to ground zero)

And wait this is a MECH wer'e talking about? Partly buried?

[Connor MacLeod]

Enough to shake a 2,500-tonne Warlord class Battle Titan, despite the inertial dampeners.

Okay, so we might be talking some millions of tons of newtons of force (about consistent with what their tank cannons probably generate IIRC) possibly. (Maybe hundreds of thousands of newtons.) Now, the amount of force applied by the blast wave is going to depend as well on the profile of the tank (the surface area) - what are its dimensions, and what was the facing? ?

Errr, the above should read "millions of newtons" not "millions of tons of newtons."

[Connor MacLeod]

There's a "hard" Exterminatus (lances, mass drivers, fusion bombs) in the Fire Warrior ending cutscene, but I dunno how long that took. The Dawn of War novel states that the end result of such a strike is reducing the planet's crust to molten rock.

The whole crust or part of it? T hat does sound like a BDZ -grade event. If we know a timeframe and number of ships, that might provdie hard figures

Another problem is that Night Haunter was being pursued by at least one other primarch (Rogal Dorn), so it's not likely that Night Haunter was going to hang around for long, given that Dorn was kind of monumentally pissed off with him.

Might be useful by implication, but I'm all just guessing. Unless your "opponent" is a fairly reasonable guy, its unlikely that you'd get away with that (think of how the old BDZ debates demanded explicit proof of timeframe, results, whatnot.. to be valid. Not everyone accepts a logical extrapolation.)

Initially somewhere between 100-50 meters I'd guess, all of two feet later.

So he's moving towards the guys firing on him? Meaning that the range steadily decreased?

Main reason Veq was deflecting/dodging the bullets was to show the Word Bearers how outmatched they were, I think. He's something of a show-off, certainly, and has a penchant for theatrics.

Well that might work too. Still, I think its alot easier to swallow if he can't TK deflect them in any other way (maybe he can shield his hands over a short distance, but not extend it far enough to deflect said projectile... that's a bit iffy though.)

That was part of what Veq was doing. His defence seems to be a combination of blocking, dodging, and catching incoming fire.

Blocking and catching would be easier to justify IMHO than dodging (Arms don't mass quite as much as the body, and you might not need to move them as far... although its still not ideal.)

Sven, a Blood Claw (Space Wolf scout) was making a point of theiving HMGs off corrupted Guard units in Grey Hunter and putting them to good use. So, they can handle some more powerful weapons (a CSM in Traitor General was carrying around an autocannon in a powered shoulder mount).

I imagine they can handle more powerful weapons due to their enhancements and armor (meaning they probably can generate greater individual firepower) But what I mean is that they either need to generate more than 1000 kg*m/s worth of momentum (probably at least several times that, given Mike's analysis of ST armor durability) or a projectile that can through some means generate MJ-range energy.

And even if the KE of a bolter shell's not overly useful, the explosive core may help.

Might.. but not penetrating before exploding is gonna hinder its effectiveness somewhat due to the nature of explosions.

Imperial Guard command vehicles, about 100m tall, and heavily shielded+armoured. They're mainly armed to fight infantry though.

Ouch.

Round from one of the myriad weapons designated macro-cannons. These range from smaller, three-tonne rounds (mentioned earlier) to APC-sized shells fired from shipboard guns.

They have rounds that mass MORE than 3 tons? How big are those?

Tactical dreadnought armour has shields of its own, but they act more to diffuse incoming fire. As far as durability, a plasma rifle shot didn't breach the chestplate of Forrix's tacdread armour in Storm Of Iron (Forrix being a shining example of how much damage it takes to put down an SM) but it was close.

I see. No idea what an SD-9 or 10 can take, unless a YVH droid is a valid example ( actually, while its likely not a very accurate example, its probably not many orders of magnitude off either.)

Yep. Which is why Imperial Guard armour units are very stringent in their selection processes: they don't like wasting the Emperor's most holy ammunition, especially if it means that a heretic gets a free shot at them.

That sounds like a serious disadvantage, (which is mitigated by their greater durability somewhat, but would still be a possible problem.)

[Connor MacLeod]

We already had a non-specific, non-quantified post in here already, and I doubt the WH40k'ers will appreicate you waltzing in and making their side look bad any more than they did the other guy. Meaning, back up some of your claims.

I have to admit I'm not exactly an expert on 40K and I'm sorry if it sounded like I was trying to sound like one, but from what I understand the general consensus is that you'd have to throw considerably more than 125 million stormtroopers at Terra's defenses to capture the GEoM. Am I correct?

Probably, if they fought like the Space Marines. Which they don't have to, neccesarily. For one thing (and probably the most important and only consideration you really need.) the odds are quite good that the Imperials would hold orbital space, giving them a tremendous advantage in orbital fire support. In addition to the firepower their heavy vehicles will afford (LAAT-like vessels, AT-ATs, etc..) and the potential range advantage Imperial troops would have with weapons - such individual disparities become less problematical.

[Connor MacLeod]

Sorry for being a troll earlier, I'll do my best to make sure it doesn't happen again.
I think to figure out how much resources the Empire would need to capture Terra we should try to figure out some variables.

(1) How many IoM warships does it take to defeat an ISD?

An ISD's firepower is probably on the high Teraton/low petaton range (shields are probably at least comparable and probably several times greater than that.) Given the known/implied firepower for the IoM, a 5:1 minimum ration in favor of the Imperials isn't unreasonable and may be in fact generous to the IoM side.

But its irrelevant, since even if the IoM ships are comparable to Imperial ones, the Empire simply has more ships to throw at them. Hell, the Empire could afford to be 1/10th the capability of IoM warships and still have an advantage in winning. All else equal, the absurd consturction rates the Empire has gives it a crucial edge.

(2) What is the fleet strength of the IoM? How many warships are based in the Sol system? How many ships do they have total? How quickly can they reinforce Sol?

Someone else will have to answer this, but I've heard "thousands" generally tossed about.

(3) How many troops does an Imperial troop carrier (Acclamator?) carry? How many troop carries per ISD in a typical Imperial fleet?

An acclamator carries 16,000 troops, dozens of small walkers (AT-TE) and large aritllery pieces (SPHA-T) and about 80 LAATs (both gunships and cargo types).

No idea. Death Squadron had at least 2, probably more (dozens probably.) Millions or billions of troops may not be improbable.

Full scale invasions doubtless include hundreds of Acclamator-type transports. (And some sources such as Lando Calrissian and the StarCave of Thonboka suggest that Imperial reinforcements can arrive on an hourly basis.)

(4) What percentage of troop carriers can be expected to be taken out between IoM fleet and Terra's ground defenses?

Depends on how the Imperials play it. Its not impossible for the Imperials to stand off to many light seconds and bombard the planet from long range (IE Hoth) to soften up the defenses before going in.

(5) What is the defending garrison of and around the Imperial palace? How many regular infantry and cavalry? How many Adeptus Custodes?

I believe this was answewred before, and it was a very large number (billions if not trillions.)

(6) How does IoM regular infantry compare to stormtroopers? How do stormtroopers compare to Custodes? How does Imperial cavalry compare to IoM cavalry?

Individually, the Space Marines are qualitatively superior in almost every respect to stormtroopers. Stormies, however, are MUCH more numerous, and they still have acess to firepower that can hurt a SM. Moreover, they definitely have a potential range advantage, although it may neccessitate a fixed position.

The GE generally seems to have an edge in their vehicles though, and possibly in coordination.

(7) How powerful is an average WH40K Psyker compared to a Sith Lord)?

depends on the Sith Lord/dark Jedi. In general, they probably have access to psykers at LEAST comparable to anyone except maybe Uber-Palpy, (disregarding any wank tactics I've described before), but they seem to almost cerrtainly hold a numerical advantage in this regard.

(8 ) As a general estimate, how many casualties would you expect the Empire to take capturing the GEoM, based on quantifiable data on the defenses of Terra?

Depends on the Empire's tactics. If they're cautious and take their time, ,casualties could be quite minimal. If they rush, then they start taking more losses.

[The Duchess of Zeon]

The WEG Imperial Sourcebook explicitly states on page 99 that:

The Corps is one of the few instances of real cooperation between the Army and the Navy. Imperial military planners from each branch designed the transport ship to hold all corps types, building in the possibility for expansion into both the starship and the unit. The fact that the corps transport ships are among the newer model of ships in the fleet is perhaps a sign that the two branches are ready to cooperate more closely so that the New Order may expand.

An armoured corps (the largest type) has 48,192 troops from 74,794 men altogether, supported by 5,128 repulsorlift vehicles and 1,219 heavy (repulsorlift) tanks, along with about a thousand man command staff and two thousand industrial repair and support 'droids. Such a corps can be landed and deployed from a single transport which is capable of landing directly on the planetary surface to unload the force in question.

[Lost Soal]

All info was taken from Imp armor. All the supers use V18 multifuel engine, kinda points towards a diesel of sorts. All tank engines are said to be multifuel, so I'm leaning towards a common tech base. No I don't think my HP estimate is low, super heavies manage a whopping 18-25 km/h so they're slow. Even the Russ is pitifully slow at 21-35 km/h. The first armored vehicle the Guard has that could race with modern tanks is the Chimera with a top speed of 70km/h.

Btw, if the HP estimate for the shadowsword engine is lowered, the recycle time for it's main weapon is also increased, or it's output is lower. Unless someone can come up with a reason why it's so slow, other than an underpowered engine.

-Gunhead

I admit I'm speculating here but the slow speed could be intentional. Modern engines when powering land vehicles of a heavy nature tend to sacrafice speed in order to generate torque. Superheavies lug around vast quantities of ammo, mount insane numbers of cannons in comparison to other tanks and are expected to travel over or through any terrain or obstical. For that torque would be more important than speed.

A small note on IoM armour. Using the figures derived from the scale model, the main hull of the superheavy can be crudely represented by a hollow box 10.8m x 6.1m x 5m, at a thickness of 220mm. This cuts off the tracks and all internal components, ammo and engines. Constructing the box out of AISI 1020 Steel, said box masses ~490 Tonnes.
Whatever they are calling steel clearly isn't what we know it as

[Black Admiral]

Okay, so we might be talking some millions of newtons of force (about consistent with what their tank cannons probably generate IIRC) possibly. (Maybe hundreds of thousands of newtons.) Now, the amount of force applied by the blast wave is going to depend as well on the profile of the tank (the surface area) - what are its dimensions, and what was the facing?

About 40 meters tall, roughly humanoid proportions, if somewhat blockier, and the facing would be the forward hull.

So probably no closer than 1-2 km, but no farther away than 30 km. Was it in front of the facility or behind it (relative to ground zero)

Behind, IIRC.

And wait this is a MECH wer'e talking about?

Yep. A Titan, one of the AdMech's avatars of the Machine God. Which is why the humanoid shape.

Partly buried?

About up to mid-thigh level I think.

[Brother-Captain Gaius]

I was reading through the recent Codex Space Marines and I stumbled upon this, regarding Marine coordination and efficiency (as well as fleet composition), which was touched upon earlier in this thread:

The Angels of Death

Space Marines are the greatest warriors that Humanity has ever produced, and each Chapter maintains battlefleets that are integral to their way of war and capable of razing an entire planet to a barren, lifeless wasteland. The largest vessel in the Space Marine fleet is the battle barge and it is comparable in fighting power to a battleship of the Imperial Navy. This massively powerful vessel can transport up to four Companies of Space Marines along with their tanks and Thunderhawk gunships. It can deliver powerful, sustained bombardments and is able to punch its way through orbital defences to delivers its deadly cargo. More numerous are the strike cruisers, fast and well armoured vessels that can carry a full Company of Space Marines, their vehicles and gunships. Like the battle barge, a strike cruiser is also able to deliver short but intensive planetary bombardments. Though these mighty vessels are the most powerful craft available to the Chapter, numerous other vessels, such as frigate and destroyer class ships also make up a Space Marine battlefleet.

Once the Space Marines fleet has punched through to the planet of their enemy, they seek to deliver a decisive blow as quickly as possible, since they are not numerous and can normally expect to be outnumbered. There are three main tactics by which the Space Marines utilise to destroy their foes, the most brutal of which is the orbital assault, known to the few that have survived such an attack as 'death from above'. The Space Marines drop into action in the wake of a devastating orbital bombardment, using drop pods and Thunderhawk gunships. With paralysing suddenness, they surgically destroy their targets, leaving the enemy leaderless and disorganized, incapable of anything except surrender or flight.

If the Space Marines are able to land heavy equipment, an equally destructive tactic is the armoured spearhead. Manoeuvering at speed, behind a far-ranging screen of bikes and land speeders, the Space Marines smash their powerful tanks unerringly against the weak link in the enemy army, armoured columns slashing left and right before powering on into the foe's vitals.

When the theatre of operations offers the room, Space Marine forces can drop or infiltrate behind the front lines and launch a series of daring raids. The enemy reels from dozens of perfectly placed blows, clumsily lashing out at the Space Marines only to miss and be attacked again. There comes a point, exhausted and crippled, that even the mightiest army collapses, whereupon the Space Marines fall on them, like wolves upon the fold, to deliver the killing stroke.

In all the galaxy that is the dominion of Man it can only be the Emperor's divine providence that allows a thousand such Chapters to exist.

[Gunhead]

Soal, IoM basic armor is called plasteel. The name would imply a lighter version of conventional steel. IoM tanks all have larger armor envelope than our steel armored tanks, yet only weight 50% more, or there abouts. (A T-55 weights around 36t, leman russ 60t). This still makes supers too heavy, but it could be just crappy design.

I've already posted the numbers on IoM armor in my previous messages.

On that torque issue, supers can do cross country at 18km/h which is just a 28% drop from their max roadspeed, so they actually have pretty high torque ratings. This assuming it's consistent regardless of hills and other land features. This still gives them pitifully low HP, because the're is no reason to make a tank slow on open flat terrain. After all such terrain should be crossed post haste, or risk enemy action against your forces.

-Gunhead

[gamesguy]

Bit off the current discussion track here, but...

How about we assign all the stormies with disrupters, which is most likely a NDF weapon(if not, then it has ridicioulous firepower in the GJ range). their short effective range(7-12 meters) shouldnt be a factor inside of a building, and their firepower means 1 hit=1 dead SM.

In addition, I see thermal detonators being very handy, perhaps mod them with an impact fuse, very useful in clearing out a room of defenses...

[Lancer]

only problem with that is that SW disruptors aren't NDF.
from Wong's SW ground weapons page:

An even more extreme example of this design philosophy is found in the Tenloss DX-2 Disruptor Pistol and DXR-6 Disruptor Rifle. An examination of the picture will reveal that both weapons are meant for extreme short range use, since even the "rifle" is no longer than a modern SMG and has no shoulder stock. The SWEGWT supports this speculation by stating that their ranges are just 7 metres and 20 metres. Ammunition capacity is also poor; both guns can fire just five shots before reloading. However, these guns are so powerful that even a single shot from the weaker pistol can disintegrate ½ m³ of durasteel armour plate! This makes them much more destructive than the normal handguns of the Empire (or the Federation), which can easily blast through rock or masonry but are ineffective against armour. The operating mechanism is actually no different than that of normal blasters; according to the SWEGWT, the only real difference is that it can "process a much greater volume of blaster gas" with each shot, thus indicating that as expected, it deliberately trades ammunition capacity for destructive power (it also means that 20 shots from a regular Blastech E-11 would have the same effect as one shot from the Disruptor).

[buzz_knox]

I don't understand the incredulity at the tonnage figures of the super heavies...

The German Maus tank from WWII was 180~ tonnes.

The experience of that tank and the other super heavies of that age (i.e. the Tortoise and the T28) is precisely why people have difficulty believing in these tonnage figures. Super heavies don't work. The tonnage is always too high for any reasonable engine to move them at something more than "full ahead crawl." And they are notoriously unreliable.

It requires fairly advanced techology to make super heavies feasible (i.e. something more powerful than diesel or gas turbine engines, armor of lighter weight but equal/greater capability than steel). But with that technology comes the realization that super heavies are about as easy to kill as ordinary tanks. They don't offer any real advantage, and soak up resources that could be used to build smaller, more effective vehicles in larger quantities. So, whenever people see a 300 ton tank (let alone with an engine that is not up to the task of moving it at sufficient speed to avoid being artillery practice), they start the have problems with suspension of disbelief.

Now, if these super heavies were capable of carrying shields (and no smaller vehicle could) or had mobility due to anti-grav (as some have suggested) or reactors things change a bit. But then, you run into the problem of if it works on them, why not use it for smaller vehicles, so you could disperse your assets?

[Dark Hellion]

No one gets away with telling the Ad-mech to be reasonable. Remember, we are talking about a civilization that has cannons that fire shells the size of WWII naval vessels. They don't believe in overkill.

[Currald]

Well, the really big superheavies (called Praetorians back in the late eighties Adeptus Titanicus) such as the Leviathan, Capitol Imperialis, Colossus, Land Train, etc. came standard with Void Shields. In practice, these vehicles and the more "reasonable" Shadowswords, Baneblade, etc, are indeed slower than the MBT Leman Russes and Land Raiders. They require considerable support from other units and function as a sort of mobile bunker, anchoring the line of infantry advance and providing anti-armor capabilities. They cannot function in the sort of blitzkrieg "charge across the desert" roles we see for dedicated tank companies. They rely on their massive weapons ranges to keep smaller tanks from getting close enough to attack.

Some other superheavies lack long-range anti-armor weapons, relying on absurd amounts of anti infantry weapons. These tanks prefer to fight within cover (though obviously not anything too conjested) and take out whatever infantry are foolish enough to show their faces. Again, though, a wise commander supports his superheavies with infantry in nearly alll situations, as they can be overwhelmed if an enemy unit gets close enough.

[Falkenhayn]

IoM fleet size is between 375-675,000 ships, IIRC, of which one fifth to one quarter are Battlefleet Solar. It's sourced back to an E-mail reply from Andy Chambers, also IIRC, though I've heard other equally prominent GW personalities cited.

[Lost Soal]

On that torque issue, supers can do cross country at 18km/h which is just a 28% drop from their max roadspeed, so they actually have pretty high torque ratings. This assuming it's consistent regardless of hills and other land features. This still gives them pitifully low HP, because the're is no reason to make a tank slow on open flat terrain. After all such terrain should be crossed post haste, or risk enemy action against your forces.

I fully appreciate that the super heavies are very slow, I'm just trying to cover all the possibilities for the these speeds.

The experience of that tank and the other super heavies of that age (i.e. the Tortoise and the T28) is precisely why people have difficulty believing in these tonnage figures. Super heavies don't work. The tonnage is always too high for any reasonable engine to move them at something more than "full ahead crawl." And they are notoriously unreliable.

It requires fairly advanced techology to make super heavies feasible (i.e. something more powerful than diesel or gas turbine engines, armor of lighter weight but equal/greater capability than steel). But with that technology comes the realization that super heavies are about as easy to kill as ordinary tanks. They don't offer any real advantage, and soak up resources that could be used to build smaller, more effective vehicles in larger quantities. So, whenever people see a 300 ton tank (let alone with an engine that is not up to the task of moving it at sufficient speed to avoid being artillery practice), they start the have problems with suspension of disbelief.

While the armour issue is a problem in real life the engines your talking about are already in use. Caterpiller are supplying quarry mining trucks which run at operation loads in excess of 300 tonnes and are powered by diesel engines which deliver power in the 3000HP range. These truck can run at speeds of upto 67kph.

In 40K it has been demonstrated that their armour is up to scratch and can shake off shots from dedicated tank destroyers. Also the psycological aspect cannot be overlooked, as most troops which see a vehicle of its size heading towards them tend to run before being squashed.

[Connor MacLeod]

About 40 meters tall, roughly humanoid proportions, if somewhat blockier, and the facing would be the forward hull.

Ouch. That's going to be a helluva lot of force then.. easily millions of newtons worth of force at 4.6 psi.. any larger would probably have knocked it on its ass if not end over end.

Behind, IIRC.

Then only part of the Mech was visible to the blast?

Yep. A Titan, one of the AdMech's avatars of the Machine God. Which is why the humanoid shape.

Makes things a bit iffier, since Mechs are generally much easier to knock over than tanks. I'll have to consider this one some.

About up to mid-thigh level I think.

That might help explain why it wasn't knocked down then. That should be enough to pretty securely brace it against the blast wave.

[Connor MacLeod]

Bit off the current discussion track here, but...

How about we assign all the stormies with disrupters, which is most likely a NDF weapon(if not, then it has ridicioulous firepower in the GJ range). their short effective range(7-12 meters) shouldnt be a factor inside of a building, and their firepower means 1 hit=1 dead SM.

In addition, I see thermal detonators being very handy, perhaps mod them with an impact fuse, very useful in clearing out a room of defenses...

Because as the quote Matt provided, most disruptors have shitty range, refire rates, and ammo capacity. Which is why they aren't military weapons, raelly.

If they need that much firepower they can use E-webs or medium repeating blasters. Being numerically superior they can more easily "gang up" on Marines in terms of firepower.

[Connor MacLeod]

Relevant tidbits (or at least what I considedred relevant)

I was reading through the recent Codex Space Marines and I stumbled upon this, regarding Marine coordination and efficiency (as well as fleet composition), which was touched upon earlier in this thread:

The Angels of Death

Space Marines are the greatest warriors that Humanity has ever produced, and each Chapter maintains battlefleets that are integral to their way of war and capable of razing an entire planet to a barren, lifeless wasteland.

I assume it means a single battlefleet (IIRC each chpater only has one, right?) Which means that each battlefleet should be capable of delivering at least 1e9 megatons worth of firepower over an unknown timeframe. Could be higher, possibly.

The largest vessel in the Space Marine fleet is the battle barge and it is comparable in fighting power to a battleship of the Imperial Navy. This massively powerful vessel can transport up to four Companies of Space Marines along with their tanks and Thunderhawk gunships. It can deliver powerful, sustained bombardments and is able to punch its way through orbital defences to delivers its deadly cargo.

Not sure what this tells us. I'd guess that given above, an upper limit on firepower is 1e9 megatons (over an unknown timeframe)

More numerous are the strike cruisers, fast and well armoured vessels that can carry a full Company of Space Marines, their vehicles and gunships. Like the battle barge, a strike cruiser is also able to deliver short but intensive planetary bombardments. Though these mighty vessels are the most powerful craft available to the Chapter, numerous other vessels, such as frigate and destroyer class ships also make up a Space Marine battlefleet.

See above.

Once the Space Marines fleet has punched through to the planet of their enemy, they seek to deliver a decisive blow as quickly as possible, since they are not numerous and can normally expect to be outnumbered.

Note the reference of a quick, decisive action once enemies are defeated - obviuosly they don't take very long to do whatever they do (which presumably includes BDZing the planet. This might give clues into timeframe if we can determine how "quickly" they tend to act. Average orbital bombardment durations might provide an upper limit, for example.

There are three main tactics by which the Space Marines utilise to destroy their foes, the most brutal of which is the orbital assault, known to the few that have survived such an attack as 'death from above'. The Space Marines drop into action in the wake of a devastating orbital bombardment, using drop pods and Thunderhawk gunships. With paralysing suddenness, they surgically destroy their targets, leaving the enemy leaderless and disorganized, incapable of anything except surrender or flight.

If the Space Marines are able to land heavy equipment, an equally destructive tactic is the armoured spearhead. Manoeuvering at speed, behind a far-ranging screen of bikes and land speeders, the Space Marines smash their powerful tanks unerringly against the weak link in the enemy army, armoured columns slashing left and right before powering on into the foe's vitals.

When the theatre of operations offers the room, Space Marine forces can drop or infiltrate behind the front lines and launch a series of daring raids. The enemy reels from dozens of perfectly placed blows, clumsily lashing out at the Space Marines only to miss and be attacked again. There comes a point, exhausted and crippled, that even the mightiest army collapses, whereupon the Space Marines fall on them, like wolves upon the fold, to deliver the killing stroke.

In all the galaxy that is the dominion of Man it can only be the Emperor's divine providence that allows a thousand such Chapters to exist.

REst of this is interesting, but not sure how it might pertain to the discussion except in describing how they conduct battles. Hafta think on this one.

[Brother-Captain Gaius]

Well, you had asked about the Imperium's combined arms capability and general operational efficiency, and I thought that passage fairly relevant and just tossed it in to support my earlier statements.

[Gunhead]

IoM armor really isn't that hot. 400mm of steel armor is nothing our RL weapons can't handle. Most infantry AT-weapons pierce 400mm of steel with ease.
And that 400mm is from a land raider that gets the best IoM can offer being a vehicle used by the SM.
Now I wouldn't use game mechanics for calculations but what I can use them for is to determine is x more powerful than y. It just doesn't tell me how much more powerful x is to y. Like a bolter is more powerful than a lasgun in the game and so it is in the stories and fluff.
This tells me most tanks and other AFVs in IoM don't have significantly more armor than 400mm of steel.

-Gunhead

[gamesguy]

only problem with that is that SW disruptors aren't NDF.
from Wong's SW ground weapons page:

Then all the better. Multi-meltas have an upper limit in the single-double digit GJ range. Multimeltas reliably kill 40k tanks.

I calced the amount of energy required to vaporize 1/2m^3 of iron a while back on SB.com, it came out to 24 GJ for vaporization, 4 GJ for melting. That is almost as powerful if not more so than multimeltas.

Meaning a single disrupter shot can take down most 40k tanks, and vaporize SMs, termies, dreads, etc with ease.

[Black Admiral]

Then all the better. Multi-meltas have an upper limit in the single-double digit GJ range.

Wrong. See Connor's estimates on page 12 of this thread.

Not to mention that vaporising 12 cubic metres of ice (Caves of Ice) takes something like 20-odd GJ IIRC, and that's just for a meltagun, not a multimelta, which is distinctly more powerful.

Also, as a random note, a Leman Russ Demolisher can survive a hit to the turret from a multimelta. However, I wouldn't recommend trying to fire the main gun afterwards.

[Currald]

This tells me most tanks and other AFVs in IoM don't have significantly more armor than 400mm of steel.

-Gunhead

All of the superheavy tanks have better armor than that. For instance, in Space Marine/Titan Legions a Land Raider has a 2+ save from the front, while most superheavies have +1 from the front (with some with even better armor). An Imperial Guard superheavy will have better survivability than a Land Raider.