Why doesn't monopropellant get a real name? Rename to hydrazine?

[tophatrhino]

From ksp1 to ksp2 liquid fuel was changed to methane. Why not give mono-propellant a real name?

Possible fuels:

• Hydrazine

• Hydrogen peroxide

• Nitrogen (Cold gas thrusters)

• Something else?

[mattihase]

CFCs

[skogs]

Hehe...I thought methalox was actually kind of fun since it is actually rarely used in real life.  Sure all the new hotness is methane and oxygen, but that hasn't always been the case. Methalox is the core of real life space race #2. Most previously used either kerosene  or hydrogen ... methane is kind of an oddball in the middle of the spectrum but obviously has some practicality to it. 

For monoprop I think cold gas nitrogen would make most sense, but also doesn't have the largest number of examples in real life. 

[TechDragon]

Given how they just swapped "Liquid fuel" for "Methane" but didn't think through the implications of using that on the Jet engines... While you can run a jet engine on liquified natural gas (which is basically liquid methane with enough impurities they don't want to call it just "methane" since liquified natural gas is more than 90% methane with the rest varying amounts of other light combustible gasses ethane, propane, butane, and some impurities like heavier alkanes, and nitrogen) and this was demonstrated by the soviets https://en.wikipedia.org/wiki/Tupolev_Tu-155 so it definitely works.

There's some issues with the density here, and a large portion of the Tu-155 was a big cryogenic tank because LNG or Liquid Methane would both require significantly more room for a given amount of energy. I don't have enough info yet to work out if they factored this in to the tank sizes and fuel burn rates. Airplane design in KSP1 (and KSP2) usually has way more fuel tank volume than you normally see, since we end up using tanks as big structural parts which in normal planes would just be cabin, cargo or fuselage, (I know some get fancier with plane designs, I'm just speaking in generalities) and so its hard to say from my own experience that they didn't faithfully swap the "fuel economy" of the jet engines over to properly match the Methane fuel. If not then I see no point in relabeling monoprop, since if they didn't adjust any of the numbers for jets then one of the major fuels is still just a generic made up liquid hydrocarbon that works roughly like how the "liquid fuel" (which is basically what kerosene is) did but this time called "Methane". If the names still dont mean anything in real life why bother giving monoprop a real name? 

To clarify that a bit... (ignoring the more specific Xenon in ion engines) 

So in KSP1 we had "Liquid fuel" + "Oxidizer" in rockets and "Liquid Fuel" in jets, which given you fill jets and rockets with (admittedly different quality/grades, but still mostly the same stuff) the liquid fuel "Kerosene" this broadly makes sense and seems like a simple abstraction to hide science details out of the way while the game focuses on other things. This didn't make a lot of sense for the nuclear rocket engine in KSP1 but hey, its a game, lets not overthink it. 

In KSP2, we have the more realistic sounding (because they are real things) "Methalox" which is short for methane and liquid oxygen and is our rocket fuel, we have Hydrogen for nuclear rockets now, and we have Methane (presumably liquid) for our jet engines... which means our rockets make complete sense, and sound more scientific, but now our jet engines are kinda whacky experimental contraptions. While yes you can build a jet to run on liquid methane, and yes its cold as heck up in the atmosphere so some of the cooling issues aren't as bad as you might think, generally speaking, liquid methane is a bad fuel for fancy fighter jets and other general aircraft and while sure you can probably do piston prop planes with compressed natural gas like you can also make cars, between the lower fuel density and the heavier tank mass, I don't know how well it would work. "Methane" as a jet fuel only makes sense on big "wide body" style jets where you have room in the middle for a respectable size cryogenic liquid tank to keep the fuel in... which is how a lot of kerbal airplanes get designed, so its not a complete write off.

But the thing is, all we did was fix the glaring issue with nuclear by giving it its own fuel type, otherwise we swapped one kind of "handwavium" fuel for another. Our not very realistic fuel just swapped from being our "Liquid Fuel and Oxidizer" rocket fuel in KSP1 to our "Methane" jet fuel in KSP2. 

So unless they really went deep and adjusted all the combustion efficiencies and everything else to make the methane fueled jet engines realistic (which I doubt, because what's the benefit the game design to make the jet engines worse?... and from the limited flying I've done the jets seem more powerful than in KSP1?) then there's not a lot of point to just for the sake of appearance, make Monopropellant into something more realistic sounding.  Which is far from a simple choice, since we've got different kinds of hydrazine, is it "normal" Hydrazine? is it Dimethyl Hydrazine? Unsymmetrical Dimethyl Hydrazine? Is it Nitrous Oxide? Hydrogen Peroxide? Something new like Hydroxylammonium nitrate? Perhaps we get one of the not entirely "mono" monopropellants like Cavea-B (more technically 1,4-Diaza-1,2,4-trimethyl bicyclo[2.2.2]octane dinitrate dissolved in white fuming nitric acid)  which had to use a little bit of UDMH each time to light the engine, but was otherwise a monopropellant as the Cavea-B burned in the engine by itself after ignition. All of these with different densities and performance, and all of them valid choices, except maybe Cavea-B...

So, is it even worth it?

We still have a level of "don't worry about the details" when it comes to our "Methane" jet engines... I'm all for realism (huge Realism Overhaul fan, cant wait to see how KSP2 goes for mod makers, because I'm already imagining how good Realism Overhaul might be as a KSP2 mod) but its still a game, its meant to be fun, and getting too technical in places probably hurts more than it helps because it leads to people being distracted by details and complaining about things like "you cant get that much thrust from a hydrazine monoprop thruster, it would have to be UDMH".

 

[kerbiloid]

It's Monomethylhydrazine usually.

[Nuke]

id do it just for consistency because all the other engines use actual chemicals rather than an ambiguous name like "liquid fuel". i generally like this move because it takes the guess work out when it comes to modding other engines, and will help declutter mod contributed resources. 

2 hours ago, kerbiloid said:

It's Monomethylhydrazine usually.

does that work as a monopropellant, because i can only find references to its use as part of a hypergolic bi-propellent (the wikipedia article kind of sucks). 

Edited March 1, 2023 by Nuke

[kerbiloid]

27 minutes ago, Nuke said:

does that work as a monopropellant, because i can only find references to its use as part of a hypergolic bi-propellent (the wikipedia article kind of sucks). 

It's first of all an RCS monopropellant, used as a component of bi-propellant to simplify the hardware.

[The Aziz]

 

 

[Kerbart]

Because there’s only one monopropellant, while we have two kinds of rocket propellant. We could, Werner-style, name them “Stoff A” and “Stoff B” but actual chemicals make more sense. Ironically, Hydrogen, technically, is used as a monopropellant…

[The Aziz]

3 hours ago, Kerbart said:

we have two kinds of rocket propellant

Two kinds so far*. Plus methane itself. Plus xenon.

[Kerbart]

Just now, The Aziz said:

Two kinds so far*. Plus methane itself. Plus xenon.

Ah yes, Xenon. Another monopropellant!

I do agree that it does make a strong case to refer to an actual chemical for monopropellant. And hydrazine rolls better of the tongue than, say, "hydroxylammonium nitrate"