[MarcoSkoll]

I can't help but think that this has got a little sidetracked though.

It has a little, but then again, this is a discussion on materials.

Depleted Uranium, apart from the toxicity and radiation, shares a lot of traits with adamantium. I imagine Admantium would be somewhat less brittle (and probably not pyrophoric either!) though.

[Adlan]

Maybe it is some alloy of Uranium then. I like Marco's idea, it being an alloy. If it's main mixture is Uranium though, that wouldn't explain, it's rarity, Uranium is about 40 times more abundant than silver.

Also, The Admech talking about Adamantium mines, if it's an alloy. Unless of course, they don't let those outside the machine cult know that it's an alloy.

[N01H3r3]

Maybe it is some alloy of Uranium then. I like Marco's idea, it being an alloy. If it's main mixture is Uranium though, that wouldn't explain, it's rarity, Uranium is about 40 times more abundant than silver.

Also, The Admech talking about Adamantium mines, if it's an alloy. Unless of course, they don't let those outside the machine cult know that it's an alloy.

Perhaps they're speaking more of the other materials specifically required to produce Adamantium, and those materials are sufficiently rare compared to Uranium to account for the overall rarity of Adamantium.

Y'know what... next week, when I'm back at work, I'm going to speak to one of my colleagues, who happens to be a 40k-playing metallurgist, about this topic. See what someone with a professional knowledge of the subject has to say about these metals...

[Kasthan]

A point to consider is that promethium would have to have an oxidising agent (oxygen) mixed in (like in TNT, which has oxygen atoms bound into the molecule, thus can provide its own oxygen giving the dramatic explosions that occur) or sprayed out at the same time otherwise it would not burn (think combustion 101; fuel, oxygen, heat). It is also daft for GW to suggest that it bursts into flame once sprayed as there may not be any oxygen in the atmosphere (e.g. Space Marines in a Space Hulk).

Also Promethium is said to be used in Imp Guard tanks and cookers, which means it can not have a massive octane rating due to engines needing a a slower (in commparsion to other fuels) more powerful burn to produce touque (which is why lorries and tanks use desiel).

My guess is that the metals that are used are alloy combinations, which at the moment we do not know about. In addition some of the metals could be isotopes that have not be discovered yet.

[MarcoSkoll]

A point to consider is that promethium would have to have an oxidising agent (oxygen) mixed in  or sprayed out at the same time otherwise it would not burn (think combustion 101; fuel, oxygen, heat).

Not at all. I think you'll find petrol burns fine in air without adding further oxygen. Given that the operators of these things need oxygen to survive, it's safe to say that if the user is still alive to use it, then it will be capable of burning.

Actually, a big part of flamethrowers is that they DON'T mix in an oxidiser.

If you mix in an oxidiser, you'd get a very hot blue flame... but one that would have a very short range, because of the high rate of combustion.
If you don't mix in an oxidiser - you get the characteristic orange/yellow flame, which can travel over longer distances.

It is also daft for GW to suggest that it bursts into flame once sprayed as there may not be any oxygen in the atmosphere (e.g. Space Marines in a Space Hulk).

Space Hulks have an atmosphere. If they didn't, nothing would live in them, and thus, nothing would need to be cleared out of them. Simple.

Also Promethium is said to be used in Imp Guard tanks and cookers, which means it can not have a massive octane rating due to engines needing a a slower more powerful burn to produce torque.

Promethium is merely a generic term for a wide range of combustible fluids - think of it as a form of slang for the word "Fuel".

In addition some of the metals could be isotopes that have not be discovered yet.

But that would still be the element in question, just a specific nuclide of it.

Like in TNT, which has oxygen atoms bound into the molecule, thus can provide its own oxygen giving the dramatic explosions that occur.

Not really... Trinitrotoluene decomposes exothermically (breaks down into smaller molecules giving off energy in the process), but the process has a high activation energy.

That is to say, it doesn't combust. Instead, it breaks apart explosively after it's conferred enough energy to start the reaction. (Similar thing with Nitroglycerine, but it has a very low activation energy, thus allowing knocks or minor heat to set it off.)

There's a difference between low explosives that are a mixture of compounds where some are fuel and some are oxidiser and thus combust... and high explosives which are simply one compound that decomposes exothermically.

I should admit that I know more about explosives than most of the people I know would like me to.

[InquisitorHeidfeld]

Plasteel is common across sci-fi settings, it is simply a plastic with most of the structural qualities of steels.
The concept probably arose during the 70s when polymer technologies were advancing at a significant rate and these new materials were particularly fashionable. A Plastic's very low cost plus the versatile applications of steel was an appealing concept.

I would suggest that Plasteel would be a thermoset plastic (akin to epoxy, Tuffnel, Bakerlite...etc). Once cured Thermoset plastics behave much more like metals than Thermoplastics and therefore are more suitable for construction applications...etc.
I would suggest that in most properties it is equal to or better than steel and that it is (in keeping with the ideas of the 70s) both significantly lighter and significantly cheaper. Other than cost one might suggest that Carbon fibre reinforced plastics offer an appropriate analogue.


Adamantium however is a mythic material - in some cases an alloy of known materials, in others a metal reserved for the gods themselves.
It is, without exception, incredibly tough. Treated appropriately it has exhibited ductility, hardness, strength, plasticity... It is implied that it is also reasonably elastic but never actually stated.
Put simply it is a reasonably rare, and therefore expensive, metallic material with exceptional qualities. Dense enough to function well as a penetrator (in the way Tungsten might be used in the real world), Hard and strong enough to defeat attempts to penetrate it.
Quite simply it is the best material for almost any task - except for its prohibative costs.

[Ynek]

It's worth bearing in mind that adamantium is not something that the GW staffers came up with. It's a ficticious material that's been getting thrown around in popular fiction for decades.

If I recall correctly, the material was first mentioned in marvel comics as being a top secret alloy made from iron which was made as an attempt by some scientist to recreate the material used to produce Captain America's shield. Since then, it has featured in dozens of different universes, usually as some nigh-indestructable super-hard doomsday material. And once again, I prove myself to be, beyond reasonable doubt, a complete nerd.

My point is that Adamantium was not made by the GW brain-trust. It's an alien element that was brought in for convenience simply so that when people see the name, they think "uber-hard metal". If they had called it "Emperorium" or something, we wouldn't know any of it's properties, but since they've used the familiar name of Adamantium, we all know that it's a super-hard, high-melting point, very rare material, just because that's the way it's always portrayed in other forms of fiction.

Just my two cents on that little matter.

[Koval]

Adamantium, or rather adamantine or simply Adamant, has also been used in fiction since Classical times. It's hardly as if Marvel came up with something totally original.

Adamantine is also an archaic name for diamond, if it's of any use.

[Kaled]

Space Hulks have an atmosphere. If they didn't, nothing would live in them, and thus, nothing would need to be cleared out of them. Simple.

Usually some bits of a hulk will have an atmosphere and some bits won't - and 'stealers are capable of surviving in a vacuum for some time, so it's entirely possible marines would want to use flamers somewhere where there's no oxygen.

[MarcoSkoll]

...so it's entirely possible marines would want to use flamers somewhere where there's no oxygen.

In such a case, you'd need a specialised flamer. The Imperium might be daft at times, but I can't see them creating and equipping all flamers so they have the capacity to work in vacuum. (So in this case, if there are "vacuum flamers" then the fuel they use is yet another different thing lumped under the term Promethium.)

Alternately, if they're in an area of a hulk without an atmosphere, the Marines might simply have to do without the flamer and use bolters instead - which would work in vacuum, because firearm propellants contain oxidisers.

Actually, on that note, that's one of the few things that irritated me about Firefly, the fact that Vera was supposed to need air to fire. (Science Fail)
But in their defence, although they don't need air to fire, guns do need air to cool them, so sustained fire with them in vacuum is pretty ill advised, as the gun will rapidly overheat and damage itself. So actually, you'd probably need specialised bolt weapons as well for using in a vacuum, made of more durable materials, and with a cooling system that could work in a vacuum*

And before anyone says "Space is cold" - yes, it is. However, that's useless without any air to act as a conductor to the heat.

*These do exist. The one NASA uses works by using the fact that boiling points drop as pressure goes down, and that boiling something absorbs energy. Basically, they slowly vent water into the vacuum, which boils off, taking heat with it.

[InquisitorHeidfeld]

Adamantium is a very ancient material - as I've previously stated "- in some cases an alloy of known materials, in others a metal reserved for the gods themselves."
Hephaestus' forges are the first incidence on the material which I can call to mind - so that's 3000 odd years in existance before it appeared in the 40k universe.

However...
While we do know that it's strong because it forms the exoskeletal framework of a suit of Tactical Dreadnaught Armour and we know that it's both hard and tough from its other applications we cannot accurately predict its properties otherwise.
Marvel's use of Adamantium differs from the original, almost all uses differ in some way from the original... In some worlds it can only be forged by magic, in some it is alchemical, in others still it is indestructable once solid...

No outside references can be used to predict the properties of Adamantium in the 40k universe simply because the adamantium of the 40k universe is different to all other instances of the fictional material.
The best guess we could make would be to call it elemental. The quintescance of metal. To say that any property one associates with metal is expressed most perfectly in Adamantium.
It would be heavy then. Aluminium is a metal and it is light but it is aluminium's lightness which makes it remarkable and therefore lightness is not a usual property of metal.
It would be strong, hard...etc. It will melt but like the one ring a blacksmith's forge won't even soften it.


On the branch topic of flamers and O2.
I would suggest that equipping Space Marines with Flamers/Heavy Flamers which do not contain either a bound source of oxygen (nitrous oxide for example) for combustion or a fuel which produces heat and flame without need for oxygen would be rather silly considering that they are all equipped as standard with a space suit.
The application of hard vacuum is not the only reason to fuel them in that manner, doing so makes the target difficult to extinguish, even by immersion for example.
There are means by which this could be done without making the flamers particularly risky - we aren't talking about a substance which needs to be self igniting for example like White Phos. The fuel could be made to have a low volitility for a start, give it a high enough ignition temperature and the risks, even on a battlefield where laser weapons are in frequent use, could be mitigated with a little refractory material... And by keeping the fuel tanks small to limit the damage when one does go up.

As to weapon overheating, Air cooled weapons do, as implied require air to conduct heat away from (particularly) the barrel but air cooling is not the only option. Water cooled weapons would be unimpeded by operation in that environment and many weapons could easily operate within normal usage parameters indefinitely because their barrels are sufficient heatsink to allow radiant heat dispersion. Bolters (given the minimal access air has to the barrel) would seem to come in that last category... particularly as the primary heat generation on such a weapon is after the round exits the weapon's barrel.

[MarcoSkoll]

I would suggest that equipping Space Marines with Flamers/Heavy Flamers which do not contain either a bound source of oxygen for combustion or a fuel which produces heat and flame without need for oxygen would be rather silly...

And I argue that it's silly on the basis that a flame weapon that carried its own oxidiser would result in a hot, but very short flame.
Think of a bunsenburner - if the air valve is shut, you get a normal yellow flame, like you see in most flame throwers. If you open the air valve, you get a hotter, but shorter blue flame.

Mixing in an oxidiser more efficient than air would only continue this trend. If doing such a thing, you'd need to find a way of heavily slowing the burn rate.

...considering that they are all equipped as standard with a space suit.

Power armour is better thought of as an environment suit. It can survive a vacuum, but it's not a feature you'd use by choice.

Water cooled weapons would be unimpeded by operation in that environment

Depends what you mean by water cooling.
Any water cooling that would work in a terrestrial environment wouldn't in a vacuum, because closed circuit water cooling is almost invariably air cooled itself. The heat that goes into the water has to go somewhere.
If you're talking about vacuum water cooling (which won't work under pressure), that's a different matter.

But in either case, bolters aren't normally water cooled. It would still involve modification.

and many weapons could easily operate within normal usage parameters indefinitely because their barrels are sufficient heatsink to allow radiant heat dispersion.

That's not actually the case. By the time radiant heat dispersion became particularly effective, you'd already have the barrel hot enough to be doing it serious damage.
And given that the barrel absorbs about as much heat as the kinetic energy of the shot, that would happen after only a few magazines from most weapons.

Bolters (given the minimal access air has to the barrel) would seem to come in that last category...

The air has a lot of access to the barrel. We're not talking about just the air that can reach the outside of the barrel, but a lot of cooling comes from air being able to flow into and through the barrel, which given the dynamics of the gas flow around barrels is actually pretty effective.

...particularly as the primary heat generation on such a weapon is after the round exits the weapon's barrel.

But they still have a basic propellant charge, which generates a lot of heat. Although bolts are self propelled, the operation of the firearm is pretty similar to any other.

[N01H3r3]

Mixing in an oxidiser more efficient than air would only continue this trend. If doing such a thing, you'd need to find a way of heavily slowing the burn rate.

Not necessarily.

Astartes doctrine is short-duration rapid-strikes that presumably are organised with the benefit of as much prior information as possible. It stands to reason that the Astartes would have access to a variety of different flamer fuels, configurations of bolter shells and so forth, along with particular alterations to the environmental systems of their armour as appropriate for the ambient conditions to allow them to operate at peak efficiency in any situation.

Thusly, they'd have promethium for low or zero-oxygen environments, and ones for higher-oxygen environments, with the appropriate one chosen as necessary. That aside, if you're fighting something capable of functioning effectively in a vacuum, you'll probably want as hot a flame as possible if you intend to incinerate it...

It may be worth noting at this point that Imperial Armour 4 actually gives us some numbers for Astartes Heavy Flamer performance. Apparently, they contain sufficient fuel for 9 seconds of continuous fire, and "generates heats in excess of 900 [degrees] C" (enough to melt aluminium or boil sodium), suggesting a fuel which burns quickly and at high-temperature.

It can survive a vacuum, but it's not a feature you'd use by choice.

Given the nature of boarding actions and space hulk missions, I can imagine they utilise the vacuum-proof qualities of their armour quite frequently. If you've got a self-contained heavily-armoured suit that can support the wearer in almost any conditions including vacuum, then why not use it for that? Certainly, it makes boarding actions against enemy vessels easier, as you are far less concerned about loss of atmosphere than those whose ship you're boarding.

[MarcoSkoll]

Thusly, they'd have promethium for low or zero-oxygen environments, and ones for higher-oxygen environments, with the appropriate one chosen as necessary.

No. If it's being done, the oxidiser and fuel HAVE to be separate, requiring separate tanks of each, and a more complex design.
Else, you'll end up with the entire tank exploding. It's very important that in flame throwers that there is no oxidiser in the fuel tank, to prevent any risk of such an incident. With an oxidiser in the fuel, then the flame can (and will) trace back through the system into the main tank, even if a flame arrester is present.

Also, can we just emphasise the point that using a flamer in a vacuum, even if it CAN work in a vacuum, is immediately less useful, because nothing but the fuel can combust (and as I've already said, it will burn very fast), thus removing any secondary sources of fire - much of the damage from a flame is through prolonged application of heat, not the application of high heat for a relatively short time.

Given the nature of boarding actions and space hulk missions, I can imagine they utilise the vacuum-proof qualities of their armour quite frequently.

Use, maybe. Choose to use, much less so, because at that point, if there are any damaged seals in the suit (highly likely, if you've taken fire), it would no longer function as such.

It's a safety measure. It's like the gear I use when working with something that has the potential to produce shrapnel. The gear may well get used (as in stopping said shrapnel from making a mess of me), but I wouldn't choose to use it (i.e. deliberately inducing a situation where it would have to stop the shrapnel).

you are far less concerned about loss of atmosphere than those whose ship you're boarding.

Under those circumstances, why worry about needing a flamer that can work in vacuum? If it can't work, odds on, everything you wanted to use it on is dead as well.

Survivors will be few, and I take it that any flamer armed marine will carry some form of sidearm.

generates heats in excess of 900 [degrees] C

That's actually pretty low, and is certainly not an oxidised flame. Even a yellow bunsen flame is about 1000 degrees C. In oxidised conditions, a blue flamed bunsen is about 1300-1500 C, and I've got a blowtorch which is capable of hitting temperatures of 1500-1600 C with the right gas mixture, which is enough to melt steel without too much bother.

[N01H3r3]

Use, maybe. Choose to use, much less so, because at that point, if there are any damaged seals in the suit (highly likely, if you've taken fire), it would no longer function as such.

Assuming no means of quickly patching damage to the armour (which seems unlikely, really), or that the Astartes themselves are engineered to be able to endure in vacuum for a time without their armour (required standard mucranoid activation treatment before any mission which contains risk of vacuum exposure).

It's an acknowledged function of the Adeptus Astartes. Whether or not it's convenient isn't a consideration - it's still something they do better than essentially everyone else in the Imperium.

you are far less concerned about loss of atmosphere than those whose ship you're boarding.

Under those circumstances, why worry about needing a flamer that can work in vacuum? If it can't work, odds on, everything you wanted to use it on is dead as well.

Survivors will be few, and I take it that any flamer armed marine will carry some form of sidearm.

The remaining survivors (like, say, Genestealers, who aren't exactly the most normal of creatures when it comes to their innate capabilities - if so engineered, a Tyranid species need never eat nor breathe so long as it has sufficient internal food and energy reserves to last as long as it needs to in order to fulfil it's biological imperative, and the other considerations of vacuum exposure are known to be within the capabilities of the Hive Mind to overcome) are the ones you need to worry about.

And, when considering flamer-armed marines, Terminators with Heavy Flamers need to be considered - they physically can't carry a sidearm. It's the heavy flamer (which, it should be noted, has been depicted for the last decade at least as having a multitude of feed pipes and nozzles... why must all of those be for the fuel itself) and a powerfist.