Engines and Oxygen

[Zanotirn]

Many of the planets in SE lack oxygen (potentially along with atmosphere in general).

This however raises a question - how do the various combustion engines work without it? A diesel engine for example burns fuel, and thus requires a supply of oxygen for burning, which normally is taken from the surrounding atmosphere. You could in theory carry your own oxygen (akin to diesel subs in WWII), but this severely limits the endurance of the vehicle. Realistically if you don't have a supply of oxygen readily available, other engine types like electric would be far more practical.

It is particularly glaring with jet and rocket engines. The primary difference between jets and rockets is that jets have an intake to get oxygen from atmosphere while rockets carry their own oxygen. For diesel engines carrying your own oxygen is at least possible, if impractical, but a jet engine carrying its own oxygen is instead by definition a rocket.


It may be possible to address this by having both diesel and electric available from the start and tracking whether the planet has enough oxidizers in atmosphere - oxygen, fluorine and chlorine will all support combustion. Some rebalancing will probably be needed (perhaps e.g. machine requirements for electric softened or removed at the cost of lower engine power) - so that diesel is more practical at the start if your atmosphere supports it, but you have the alternative of using electric (this would be similar to to existing systems like having rainfall vs having to work for your water). Plus the various propeller-family engines would need to track if they are driven by combustion or electric. This might actually end up providing more gameplay variability with planets that are not combustion-friendly limited to lighter vehicles at the start.

[BlueTemplar]

For planets with atmospheric composition identical to Earth (but not necessarily the same pressure), this might already be the case for aircraft :
fb.asp?m=4950001

ORIGINAL: Soar_Slitherine

ORIGINAL: zgrssd

I would say at 20% Atmospheric density (200 mBar), you should expect 20% lift.
Given a 0.20g gravity, you would need 20% Lift.
So on the planet you gave, I would expect airplanes to be about as feasible as on earth.

According to this document by Vic, aircraft with non-rocket engines actually lose a lot of efficiency under very low air pressure, even if gravity is decreased by a similar ratio. It's not merely a matter of lift, most aircraft engines require air for combustion as well.

[BlueTemplar]

There's this other glaring issue I can't believe I haven't noticed before :
On planets with a gravity different from Earth, weight should be different for ground vehicles too ! (At least for the design weight, I think of the logistic weight more like size = volume = "bulk" ? The logistic "weight" is rather being expressed in units of mass anyway : 1 logistic point generally massing 10 tons.)

(And air pressure should play some role on their movement too...)

[varangy]

ORIGINAL: BlueTemplar

For planets with atmospheric composition identical to Earth (but not necessarily the same pressure), this might already be the case for aircraft :
fb.asp?m=4950001

ORIGINAL: Soar_Slitherine

ORIGINAL: zgrssd

I would say at 20% Atmospheric density (200 mBar), you should expect 20% lift.
Given a 0.20g gravity, you would need 20% Lift.
So on the planet you gave, I would expect airplanes to be about as feasible as on earth.

According to this document by Vic, aircraft with non-rocket engines actually lose a lot of efficiency under very low air pressure, even if gravity is decreased by a similar ratio. It's not merely a matter of lift, most aircraft engines require air for combustion as well.

This is a completely different thing.

It is talking about the propellers loosing effect because of the thin air. The composition of the air does not mater in this regard only air pressure.

OP is talking about how a combustion engine would work without oxygen. You can have 10 times more air pressure than on earth, but without oxygen your engine would not turn on.

[BlueTemplar]

Read OP more carefully :

Many of the planets in SE lack oxygen (potentially along with atmosphere in general).

My quote is specifically about the effect you (supposedly ?) get in the game due to aircraft lacking oxidizer. The game "just" assumes that all planets have the same oxidizer composition as Earth does in this matter.

[zgrssd]

ORIGINAL: Zanotirn

Many of the planets in SE lack oxygen (potentially along with atmosphere in general).

This however raises a question - how do the various combustion engines work without it? A diesel engine for example burns fuel, and thus requires a supply of oxygen for burning, which normally is taken from the surrounding atmosphere. You could in theory carry your own oxygen (akin to diesel subs in WWII), but this severely limits the endurance of the vehicle. Realistically if you don't have a supply of oxygen readily available, other engine types like electric would be far more practical.

It is particularly glaring with jet and rocket engines. The primary difference between jets and rockets is that jets have an intake to get oxygen from atmosphere while rockets carry their own oxygen. For diesel engines carrying your own oxygen is at least possible, if impractical, but a jet engine carrying its own oxygen is instead by definition a rocket.

Jet vs Rocket is not a factor here.

There are two parts to this discusion:
The need for a Oxydiser
The need for a reaction mass

Vic decided that in general combustion engines do not require Oxygen to operate at 100%. Somehow the Oxydiser is part of the fuel.
And at the same time, nobody just repalces superflous oxydiser with more fuel if the Oxydiser could literally be gotten from the air.
This avoids a whole lot of fringe casse, like there being enough Oxygen to run a engine - just not at the ground, where CO2 gathers.
Fuel is abstracted, to be easily useable (nevermind it being called Oil in reports - it is clearly not what it is!)
It can stand for fosil fuel, some metahne compounds or evne Liquid Energy - whatever the heck that is.

Rockets provide two things to work where they do:
a) A oxydiser (ironically it is rarely Oxygen, as it is not that good of a Oxydsier)
b) Reaction mass

The Ion Thrusters do not need the Oxydiser (given that it is a Magneto-Electric engine), but still need to provide their onw Reaction mass.

[Zanotirn]

Hmm, having oxidizer as part of the fuel would be a Very Bad Thing for a military vehicle. Petrol tanks are relatively safe only because the large amount of fuel in them is exposed to very little oxidizer. If the fuel spills and thus comes into contact with a large amount of oxygen, it becomes extremely flammable. On the other hand if the fuel is already self-contained and is only missing ignition (even if its formula is such that it requires high temperatures to ignite), in the realities of war that ignition can be provided by a lot of things like enemy fire or loading accidents. This would be worse than having engines run on gunpowder. It could work by having the fuel require some very specific catalyst but I'm not sure if it's possible with hydrocarbons. Or more likely carrying the fuel and oxidizer separately and only mixing them in the engine - which is again, the "bring-your-own-oxygen" setup, which runs into problems in real life, since with the fuel-air ratio of combustion engines for every 1 kg of fuel you'd need to carry something on the order of 15 kg of air, or around 3 kg of pure oxygen (though pure oxygen setups are impractical IRL due to too high temperature it leads to) or about 6 kg of N2O). And fuel-hungry vehicles like tanks are already very limited in the amount distance they can cover on a full tank.

edit: fixed a number

[zgrssd]

Hmm, having oxidizer as part of the fuel would be a Very Bad Thing for a military vehicle.

There is this secret technique called "use two tanks, damit!"
Rockets Scientists figured out that one before the first launch!

The game fuel figures are either aimed to simulate "you have oxydizer, no questions asked" or "you always have to carry oxydizer seperately" - and simply does not care about the opposite case too much.

[Fritz1776]

You know, maybe the atmospheric composition could be taken into account without having to massively overcomplicate things. The five possibilities are basically (near) vacuum, inert, oxidizer (O2), fuel (e.g. H2), and oxidizer + fuel. That last one probably being impossible but I'm not going to assume anything. Given that, you could say that fuel capacity is reduced by some factor if the atmosphere is inert, since you need oxidizer as well. Fuel atmosphere would be the inverse since you just intake combustibles from the atmosphere and oxidize them, so similar result although I'm not sure if the ratio would be different.

[zgrssd]

ORIGINAL: Fritz1776

You know, maybe the atmospheric composition could be taken into account without having to massively overcomplicate things. The five possibilities are basically (near) vacuum, inert, oxidizer (O2), fuel (e.g. H2), and oxidizer + fuel. That last one probably being impossible but I'm not going to assume anything. Given that, you could say that fuel capacity is reduced by some factor if the atmosphere is inert, since you need oxidizer as well. Fuel atmosphere would be the inverse since you just intake combustibles from the atmosphere and oxidize them, so similar result although I'm not sure if the ratio would be different.

There is a whole lot more Oxidizers then you can imagine. The list includes at least:
- Oxigen
- Hydrogen Peroxide
All 5 Halogens:
- Flourine
- Chlorine
- Bromine
- Iodine
- Astatine

Alternatively what you put into the tank might be the oxidizing agent, and you get the fuel from the Air. Flourine can treat just about anything as fuel, starting with most metals and 4 of the 7 noble gasses (you know, those gasses known for being extremely non-reactive).
At wich point we have to deal with a dozen alternative gasses to be retrieved and used.
There are metric butt-ton of combinations to skin Shroedingers Cat here.

Better to just keep things sane and simple.
Maybe add some early electrical engines that moons can start with.

[Zanotirn]

In terms of complexity this wouldn't be any worse than water atmospheric recomposition which currently needs one of 4 gases with oxygen plus one of 3 gases with hydrogen at 0.5% or above. And the player would probably just get a summary on feasibility of combustion engines in the help report section similar to how currently several factors are condensed there into advice on recommended agriculture method.

[Zanotirn]

Also there can be other arguments for having cheaper and simpler electric engines in-game. E.g. the main difficulty in an electric vehicle is the power storage (the engine per se is actually simpler to make than combustion engine) and any unit with energy weapons would presumably already have good power banks. So it looks odd to have lasers on a vehicle require just some usual IP plus metals, but if you want to add an electric engine on the same vehicle the price would suddenly include machines.

[arvcran2]

ORIGINAL: zgrssd
...

There are metric butt-ton of combinations to skin Shroedingers Cat here.

...

LOL!