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So, this is another inane question about the tech in 40k which most likely has no answer other than "GW said so". The imperium has reliable fuel cell technology, a lot of it. The most common weapon in the 40k verse is the humble Laguna, each las gun has at least on fuel cell as its magazine. These cells can be recharged by positioning so that they face a fire, granted that would take a long time, but; it's common practice to recharge them by just leaving them out in the sun. Indeed, the simplicity of this set up is one of the reasons that the las gun is so ubiquitous in the imperium. The other is its ease of manufacture, which implies that the fuel cell is also easily manufactured. Each fuel cell contains enough energy for what, hundreds? Thousands of shots? Each shot is capable of punching a hole through a person. That's a lot of energy.
So, (I like that word) my question; why doesn't the imperium make larger fuel cells to power their vehicles? Why so much use of promethium? I don't think a smoothly running clean leman rus is going to make the death of a billion guardsmen a day any less grim dark, but poorly maintained leaking Diesel engines are almost a distraction from the setting.
Well, that's my two cents.

Because they don't know how. The advancement of technology, and building things in any way shape or form that are different to the standard designs they have access to is considered tech heresy.

While it's a bit silly the fluff seems aimed at "we don't know how to produce X reliably enough".

If you look at modern tanks, some run on multi-fuel based engines, meaning you can fill them with almost anything and it'll combust enough to move the tank. I think it's probably the same idea. A simple normal motor would be far cheaper and easier to maintain for a large army on the move or PDF forces o backwater planets (by this logic they should also be using autoguns).

Short answer? Because GW.

This is more of a background question.

That said, according to the FFG rpg books, a lasgun or laspistol gets between 15 to 60 shots per fully charged pack, depending on setting.

The average guardsman is issued one, maybe two (maybe none!) and the need to charge it in the sunlight or by a campfire should tell you how desperately long they can be expected to go without getting a chance to charge thenlm properly, which probably involves a generator also burning prometheum.

'Cause this isn't a clean-and-simple sci-fi setting, it's THE GRIM DARKNESS OF THE FAR FUTURE.

More seriously if you're looking for an in-setting technological reason it could be an ease-of-maintenance thing or a useful life thing (it is implied or stated that lasgun power packs can be damaged by repeated 'toss it into the fire' quick recharging), on top of the Machine Cult's resistance to innovation. They may just not have worked out all the possible applications of the technology; how long was China building fireworks and explosive catapult shells for before someone worked out cannons?

plus Promethium isn't just petrol, it's all purpose explodey juice which comes in as many grades as there needs to be for the sake of the plot of a given story.

It is plentiful, easy to refine and 100% munitorum sanctioned heretic burny juice.

I guess that my wider problem is that I feel that sometimes the emphasis on grim dark gets in the way of the story. The universe should be grim dark because humanity is beset on all sides by endless tides of enimeis. They don't need to make common sense illegal and all lasguns with a two-way barrel to make it depressing.

Power cells don't generate smoke, and clean energy is very anti-grim-dark.

More likely, power cells drain quickly, have long recharge time and may be complex/time consuming to create (compared to extracting promethium). If you look closely at the size of flamer weapons, you will also note that as small as the cannisters are, they too last an entire battle (or are small/light enough to carry enough to last entire combats), so it is much denser/has a higher energy output than our conventional diesel/napalm.

KayTwo wrote:
So, this is another inane question about the tech in 40k which most likely has no answer other than "GW said so". The imperium has reliable fuel cell technology, a lot of it. The most common weapon in the 40k verse is the humble Laguna, each las gun has at least on fuel cell as its magazine. These cells can be recharged by positioning so that they face a fire, granted that would take a long time, but; it's common practice to recharge them by just leaving them out in the sun. Indeed, the simplicity of this set up is one of the reasons that the las gun is so ubiquitous in the imperium. The other is its ease of manufacture, which implies that the fuel cell is also easily manufactured. Each fuel cell contains enough energy for what, hundreds? Thousands of shots? Each shot is capable of punching a hole through a person. That's a lot of energy.
So, (I like that word) my question; why doesn't the imperium make larger fuel cells to power their vehicles? Why so much use of promethium? I don't think a smoothly running clean leman rus is going to make the death of a billion guardsmen a day any less grim dark, but poorly maintained leaking Diesel engines are almost a distraction from the setting.
Well, that's my two cents.

Cost efficiency and ease of manufacture. Even "thermic combustion reactors" in Astartes vehicles run on liquid fuel. Even exotic internal combustion engines are cheaper to build and easier to maintain than hyper-advanced powerplants.


Can the Mechanicus build advanced, powerplants that don't need liquid fuel? Of course they can. Just look at all the cool stuff they hoard...er, reserve...for their own forces. But with the Imperium's current situation and logistical needs, arc-reactors, huge power cells, and tank-sized plasma furnaces are just not practical to produce on such a large scale.

 Elbows wrote:


Short answer? Because GW.

No. Not "Because GW"

Unless that's your short answer for every fluff question...in which case why even bother reading any of the fluff?

KayTwo wrote:
I guess that my wider problem is that I feel that sometimes the emphasis on grim dark gets in the way of the story. The universe should be grim dark because humanity is beset on all sides by endless tides of enimeis. They don't need to make common sense illegal and all lasguns with a two-way barrel to make it depressing.

The grimdarkness can go over the top, yes, but trying to make significant changes to the aesthetic to it based on out-of-setting moral considerations (does anyone see the Imperium worried about environmental impact anywhere? At any time?) isn't much better. Honestly I find a better antidote to the grimdarkness to be zooming in on the small scale and examining the people (or creating a cast of slightly nicer people) instead of trying to doctor the setting; the Imperium is borked at a large scale and running mostly on momentum, that doesn't mean everyone in it is depressingly unfriendly or otherwise a jerk. Small acts, good people, and the struggle to be moral mean more against such a horrifying backdrop than they would in a setting where the writers are nice and everything's going to work out all right.

 AnomanderRake wrote:

KayTwo wrote:
I guess that my wider problem is that I feel that sometimes the emphasis on grim dark gets in the way of the story. The universe should be grim dark because humanity is beset on all sides by endless tides of enimeis. They don't need to make common sense illegal and all lasguns with a two-way barrel to make it depressing.

The grimdarkness can go over the top, yes, but trying to make significant changes to the aesthetic to it based on out-of-setting moral considerations (does anyone see the Imperium worried about environmental impact anywhere? At any time?) isn't much better. Honestly I find a better antidote to the grimdarkness to be zooming in on the small scale and examining the people (or creating a cast of slightly nicer people) instead of trying to doctor the setting; the Imperium is borked at a large scale and running mostly on momentum, that doesn't mean everyone in it is depressingly unfriendly or otherwise a jerk. Small acts, good people, and the struggle to be moral mean more against such a horrifying backdrop than they would in a setting where the writers are nice and everything's going to work out all right.

Slightly off-topic, but along those lines, I prefer stories following average citizens just trying to get by in the middle hive. I always found Dark Heresy to be more interesting than the other RPG systems.

You're overestimating the energy contained within a las shot. Regardless, if you want some utopian sci-fi setting, you're in the wrong universe.

Don't you know that new and inivative ideas are heresy? Follow the standard templates or be *BANG* ...

~What heresy is going on here?~

Because it's simple to produce. You can mine it from glass planets it's cheap and doesn't require high tech stuff.

The production of nuclear power is nearly a lost art

 troa wrote:
You're overestimating the energy contained within a las shot. Regardless, if you want some utopian sci-fi setting, you're in the wrong universe.

I don't see how cleaner energy makes the universe less grimdark, especially when said clean energy is being weaponised on a massive scale. Rake put the grimdark in 40k best with what he said earlier:

 AnomanderRake wrote:
the Imperium is borked at a large scale and running mostly on momentum, that doesn't mean everyone in it is depressingly unfriendly or otherwise a jerk

It's not something that has to be mandatory to everything that happens in the universe. A universe where you know that everything is hopeless and everything that goes on reflects that idea would make for a frankly dull reading experience, and 40k is certainly not a hopeless setting, despite the Imperium being in total anarchy and beset on all sides by Xenos and Heretics.

Back on to the question, it's already been mentioned - innovation is Heresy within the Imperium, unless the innovation is in the form of an STC. Promethium is also a very potent substance that can power anything from the smallest Hand Flamer to the biggest Thunderhawk Engines - it's a very flexible resource that can be used to power practically the entire spectrum of Imperial technology, while also keeping the technology easier to maintain. Lasguns are a piece of technology that function differently because they typically have such a small power demand (until you crank up the Megathule setting of course), and even bigger Laser Weapons such as Lascannons and even Battleship Lances require a lot of space to fit their thirsty capacitors.

It's therefore much easier and practical to use fuel based tech to power anything that doesn't need to slice straight through a battle tank, and Promethium is the perfect platform for this.

G.A

KayTwo wrote:
I guess that my wider problem is that I feel that sometimes the emphasis on grim dark gets in the way of the story. The universe should be grim dark because humanity is beset on all sides by endless tides of enimeis. They don't need to make common sense illegal and all lasguns with a two-way barrel to make it depressing.

It's not that common sense is illegal. It's that maintaining the specialist knowledge and infrastructure to build and maintain technology like that is pretty hard when you're beset on all sides by endless tides of enemies.

Planets die, libraries burn. Suddenly you're left with a bunch of people who know that a piece of tech does work, and how to keep it working, but not how to build one from scratch. You spend time trying to rebuild your universities and your factories, hoping perhaps a sage from another world will arrive to instruct you, but along comes another existential threat. The knowledge is passed down imperfectly to the next generation of embattled technicians. If the tech was built robustly enough in the first place, it may even stay useful for thousands of years. Eventually it will be maintained by those with no concept of how it could function, and without the educational infrastructure to learn, because their society is focused on survival.

Under those conditions, the types of technology that survive are the simple and robust ones (promethium combustion engines), the ones that are widespread and critical to society's function (plasma drives, lasguns), and those that have managed to develop focused subcultures dedicated to their preservation (bolters, STCs, etc.). What you don't get is people trying to figure out how to wring motive force from a lasgun clip, because that requires working from first principles through experimentation through industrialization- which very few planets have the luxury of enabling.

Another possible factor is ease of repair. The clunky internal combustion engines allow for quicker repair if the damage was light or superficial. Lasgun packs on the other hand are described in Fear the Alien to be malfunction when damaged, to the point where they can explode. A shot to the engines of a lasgun powered vehicle would require the crew to abandon it lest it suddenly explode. The time spent repairing tanks between battles would be significantly increased.

Would you put some crazy hi-tech engine into vehicle that is labeled as expendable (Rhino, Chimera, Taurox, even the Leman Russ tank)... No.
On the other hand, Baneblade tanks are eqipped with nuclear reactors, if i remember correctly. (Baneblade Novel)
Are Baneblades labeled as expendable? No...

Edit// Lexicanum says that Baneblade uses multifuel powerplant, but I still think that the novel mentioned nuclear reactor. Or at least a reactor of some kind.

 Hawky wrote:
Would you put some crazy hi-tech engine into vehicle that is labeled as expendable (Rhino, Chimera, Taurox, even the Leman Russ tank)... No.
On the other hand, Baneblade tanks are eqipped with nuclear reactors, if i remember correctly. (Baneblade Novel)
Are Baneblades labeled as expendable? No...

Edit// Lexicanum says that Baneblade uses multifuel powerplant, but I still think that the novel mentioned nuclear reactor. Or at least a reactor of some kind.

Mars Triumphant was a mars-pattern; it specifically mentioned the reactor as one of the differences from the other one in the company (Ostra-something)

Each fuel cell contains enough energy for what, hundreds? Thousands of shots?

About sixty. Similar question in reverse - why don't we power tanks and trucks today with cordite propellant from gun cartridges?


(Because you can't get the energy out in controled quantities in a useful form. High-capacity quick-discharge power cells are probably the same).

Look at a modern battery powered car.
Takes forever to recharge.
Range is limited.
Power cells dont have the longevity.
There might not be enough rare metals.
Or they might just decide to blow up sometime.

It is worth noting that things like the Ordinatus engines use the same plasma furnaces as starships IIRC as power.

So when innovation is permitted and it's the techies that build it it doesn't use promethium.

Suppose you are the leader of some backwater world in the IoM during wartime. You are tasked with producing as much as possible in order to support the war apparatus of the imperium and. Now guess what happens when your tech cult for some reason can't keep up with the local power requirements by just patching up the few old nuclear reactors that are still running your planet.

You could try to order new ones, but we all know how fruitful that will be. Or you could you know run your economy on Promethium, that just happens to be produced locally.


Automatically Appended Next Post:
Lets skip ahead 10.000 years of technological regression further. You are now an army commander. Your supply lines are hardly putting out any new nuclear reactors, your tech priests are horrible at repairing them and most of the planets supplying you just happen swim in large quantities of Promethium.

Would you ask those red robed bureaucrats to supply you with promethium accepting engines instead ?

 malamis wrote:
plus Promethium isn't just petrol, it's all purpose explodey juice which comes in as many grades as there needs to be for the sake of the plot of a given story.

Yup. Resin, liquid, solid blocks - you name it. Promethium is just the IoM's universal term for fuel really. It can vary from world to world.

 General Kroll wrote:

 Elbows wrote:


Short answer? Because GW.

No. Not "Because GW"

Unless that's your short answer for every fluff question...in which case why even bother reading any of the fluff?

Yes. Because GW. They wrote it.

How do you quickly charge the bank of power cells needed to run a leman russ?

With a promethium powered generator.

Can you charge them as quickly as you can refill a fuel tank? Unlikely.

You also need to take the generators plus promethium to the front lines to charge them instead of merely taking the promethium.

 the Signless wrote:
Another possible factor is ease of repair. The clunky internal combustion engines allow for quicker repair if the damage was light or superficial. Lasgun packs on the other hand are described in Fear the Alien to be malfunction when damaged, to the point where they can explode. A shot to the engines of a lasgun powered vehicle would require the crew to abandon it lest it suddenly explode. The time spent repairing tanks between battles would be significantly increased.

Yeah, but promethium is highly flammable and will either catch fire or explode when shot....so, I don't see any added safety value by using it.

KayTwo wrote:

 the Signless wrote:
Another possible factor is ease of repair. The clunky internal combustion engines allow for quicker repair if the damage was light or superficial. Lasgun packs on the other hand are described in Fear the Alien to be malfunction when damaged, to the point where they can explode. A shot to the engines of a lasgun powered vehicle would require the crew to abandon it lest it suddenly explode. The time spent repairing tanks between battles would be significantly increased.

Yeah, but promethium is highly flammable and will either catch fire or explode when shot....so, I don't see any added safety value by using it.

https://en.wikipedia.org/wiki/Self-sealing_fuel_tank

KayTwo wrote:

Yeah, but promethium is highly flammable and will either catch fire or explode when shot....so, I don't see any added safety value by using it.

Shooting a tank of flammable material does not cause it to catch fire or explode. This is movie nonsense. It needs to be mixed with air and heated at the same time to cause combustion.