Forum adverts like this one are shown to any user who is not logged in. Join us by filling out a tiny 3 field form and you will get your own, free, dakka user account which gives a good range of benefits to you: No adverts like this in the forums anymore. Times and dates in your local timezone. Full tracking of what you have read so you can skip to your first unread post, easily see what has changed since you last logged in, and easily see what is new at a glance. Email notifications for threads you want to watch closely. Being a part of the oldest wargaming community on the net. If you are already a member then feel free to login now.

It depends. Do you mean what projectile has the most heat energy or the highest absolute temperature?

You can have a high absolute temperature and not have a ton of heat energy. The Nova Cannon's plasma warhead burns with the energy of a small star, but it could have a lower temperature than a plasma macro-cannon battery bolt. It just does more damage due to having massive amounts of mass with high energy as opposed to a more conventional plasma macro-battery shot which has high temperature but much lower mass.

The sun is very hot, but its possible to generate temperatures in labs here on Earth that are much hotter than the sun. Obviously, its a very tiny amount of matter that is that temperature. Its all about the dose.

Commissar von Toussaint wrote:

I always hated the "plasma gets hot" rule. Any weapon that killed its user with the regularity of Russian roulette would have been either pulled from service or lost on the battlefield with alarming regularity.

They were, in 2nd edition. The CSM used the Mk.1 plasma weapons which had the equivalent of "Gets Hot". Imperials used plasma weapons that required a turn of cooling afterwards if you fired on full power, and this was supposedly done because the old weapons were causing unacceptable Marine losses from overheating. The CSM didn't change because they cared more for power and fire rate than safety.

However in game terms, the Mk.1's were more desirable, as the risk of overheating wasn't that high and there were different severity levels of overheating so some were more survivable. Having to cool off a turn was a big drawback as it effectively halved the firepower output of that plasma weapon at full power as games in 2nd edition lasted 4 turns. Yes they could use other carried weapons while the plasma one cooled but it still meant the utility of the plasma weapon was effectively halved.

 Grey Templar wrote:
It depends. Do you mean what projectile has the most heat energy or the highest absolute temperature?

You can have a high absolute temperature and not have a ton of heat energy. The Nova Cannon's plasma warhead burns with the energy of a small star, but it could have a lower temperature than a plasma macro-cannon battery bolt. It just does more damage due to having massive amounts of mass with high energy as opposed to a more conventional plasma macro-battery shot which has high temperature but much lower mass.

The sun is very hot, but its possible to generate temperatures in labs here on Earth that are much hotter than the sun. Obviously, its a very tiny amount of matter that is that temperature. Its all about the dose.

Ok, but the Sunfury Plasma Annihilator fires the equivalent of a small sun. Which is just a big star. So is a titan based plasma gun hotter than a ship based nova rail gun? According to the fluff yes. Then again the Necrons have guns that can literally destroy an entire planet, so that I guess? A Doomsday Ark's main cannon is powerful enough to completely vaporize a titan's voidshield in a single shot. A Deathmark fires a gun that turns it's opponent to ash in five dimensions?

I think Sanguinius' Abs take the cake.

Not sure why you feel the very-scientific measurement of "small sun" trumps "small star". Sounds equivalent to me- a sun is a star, there is nothing remarkable about Sol.

To add my two cents.

Lasers aren't inately hot in of themelves. Their "het" comes from blasting photons at a point. It's how satelights with solar sails move. The photons hitting the sails causes the energy s it moves. You can see this on youtube. omeone has a lightweight cube on a near zero friction surface, they shine a torch at it and it moves the object. So for lasers its the energy of build up of photons blasting a certain poin causing the damage. So I wouldn;t say they're hot of themelves, merely the heat comes from the natural reaction of photons hitting the receiving point. So if a surface was incredibly reflective it wouldn't get hot at all. Lasers are typiclly 6000c, of course scale thi up to the larger ship weapons.

Plasma weaponry I would say is up there. Plasma is a state of matter, plasma its supercharge molecules. So you are seeing the ionisation of the molecules. that is the plasma. So the very nature is they have to get hot enough to ionise and thus cause the reaction. Plasma is typically in the range of 8000 celsius, of course scale this up to the larger ship weapons.

Melta weaponry is a sub atomic reaction. So along the line of a small fusion reaction. Melta weapons cause a sub atomic raction then force the energy of said reaction out of the desired direction. Giving the energy only one direction of escape. Sub atomic reactions typically happen in the very high heats. Fusion reactions if this is comparable typically is around 150M Celsius. Again scale this up for the larger weaponry.

So from a tabletop sandpoint I'd say meltas are the clear winners.

However it depends what the larger weapons use. I believe the hottest we have had a laser go is 2M Celsius.
So on the troop level I would say:
1: Melta
2: Plasma
3: Laser

But on an ordenance level.
1: Melta Based (Nova etc)
2: Laser
3: Plasma (because the need for ionasation range wouldn;t change, merely the pwer output to get a bigger ball)

Happy to be proven wrong, im no scientist. This is just my two cents.

People keep using varying descriptions of how Nova Cannons work. They are Rail guns, not melta guns. They magnetically send a piece of metal to a point at the speed of light. In total vaccum such as space there is no heat build up because it's zero friction.

A Melta gun shoots or "vents" a ton of burning hot "plasma" in a cone and ignites it(?) For obvious reasons there is no science here, as it's all completely fantastical. The Gluons take the Zagmus and propels them along the Dingus Array towards the target, before igniting them using Mungo Jerry emitters. Same exact scientific basis for how Meltas work.

Same with Plasma. There is no scientific basis for why "plasma" would be a self contained star's worth of heat.

Lasers and Railguns are literally the only things in 40k ripped from actual scienctific fact, and that is just using hyper focused light to form a powerful beam. And only one of them generates actual heat.

Nova cannons are relevant because they have a warhead that explodes and creates heat. Yes, the railgun part doesn't make any notable amount, its what it delivers to the target.

 Grey Templar wrote:
Nova cannons are relevant because they have a warhead that explodes and creates heat. Yes, the railgun part doesn't make any notable amount, its what it delivers to the target.

Nova cannon rounds are usually as described in BFG a solid round that is accelerated by a railgun (one that seems to use gravity rather than EM) at somewhere approaching , and then the round has a timed fuse that detonates the shell releasing a blast of plasma.

Warriors of Ultramar describing part of the battle for Tarsis Ultra describes a nova cannon shell as moving at 5,000 km per second which is 18,000,000 km per hour. That is about 1.6% lightspeed.

People need to differentiate between heat and temperature. A shot of plasma from a hand held plasma gun may shoot a bolt of plasma that is at the same temperature as the surface of the sun (about 6000K), but it has less heat energy (i.e. how many joules) than the sun because there is less mass.

Iracundus wrote:
They were, in 2nd edition. The CSM used the Mk.1 plasma weapons which had the equivalent of "Gets Hot". Imperials used plasma weapons that required a turn of cooling afterwards if you fired on full power, and this was supposedly done because the old weapons were causing unacceptable Marine losses from overheating. The CSM didn't change because they cared more for power and fire rate than safety.

However in game terms, the Mk.1's were more desirable, as the risk of overheating wasn't that high and there were different severity levels of overheating so some were more survivable. Having to cool off a turn was a big drawback as it effectively halved the firepower output of that plasma weapon at full power as games in 2nd edition lasted 4 turns. Yes they could use other carried weapons while the plasma one cooled but it still meant the utility of the plasma weapon was effectively halved.

My cat is blocking my access to the Chaos Codex, but if memory serves both Mk I and later plasma guns could be fired in single-shot mode with no risk (same with the heavy plasma gun). Where you needed a recharge was when you pushed the envelope.

Doing that naturally brings certain tradeoffs, but it also allows you to just accept the utility of an S7 weapon.

"Gets Hot" was an every shot kind of thing, so you have a 1 in 6 chance of shooting yourself. However, it was AP 2, and in 3rd AP 2 was the Holy Grail of missile weapons, capable of killing even Terminators outright (initially at least).

It was a dumb rule.

There is no "warhead" in a railgun, it's just a solid slug that hits with such unparralleled force, that it acts as a massive explosion. Think the Rock that hit the earth and made the Dinosaurs be unalive. That was essentially a Railgun to the planet. No explosives involved, just such incredible force that it altered the entire planet's atmostphere. That's a novacannon.

FezzikDaBullgryn wrote:
There is no "warhead" in a railgun, it's just a solid slug that hits with such unparralleled force, that it acts as a massive explosion. Think the Rock that hit the earth and made the Dinosaurs be unalive. That was essentially a Railgun to the planet. No explosives involved, just such incredible force that it altered the entire planet's atmostphere. That's a novacannon.

No. Nova Cannons quite explicitly have a plasma warhead. It is a railgun that has a plasma warhead in its projectile

Railguns typically don't have warheads, but that is not a requirement for something to be considered a railgun.

A solid projectile isn't going to explode into plasma in space.

A nova cannon is described in the BFG rulebook:

A nova cannon is a huge weapon, normally mounted in the prow of a ship so that the recoil it generates can be compensated for by the vessel's engines. It fires a projectile at incredible velocity, using graviometric impellers to accelerate it to close to light speed. The projectile implodes at a preset distance after firing, unleashing a force more potent than a dozen plasma bombs.

BFG rulebook, p. 22

Yeah, clearly not just a solid slug. It has a warhead.

I always thought that meltas were supposed to be masers (concentrated microwave weapons).

Nope. Shotgun blast of super heated Plasma Vapor.

 Emperors Grace wrote:
I always thought that meltas were supposed to be masers (concentrated microwave weapons).

Yes they were basically masers as described in 2nd edition

Subsequently GW in its technobabble seems to have made them maybe something different.

Also some weapons like the Eldar Fusion weapons don't seem to be masers...if you go by the term fusion. I thought of them perhaps being plasma weapons but where the plasma is compressed enough to have actual fusion going on, as opposed to plasma weapons where the plasma is hot but not hot enough or under enough pressure for fusion.