Do you want liquid fuel to be changed to realistic counterparts?

[magnemoe]

On 5/3/2020 at 2:09 PM, SpaceFace545 said:

I hear what you say but the advanced systems like metallic hydrogen will be doped with deuterium and other things to make it stable and we will have fusion engines that need to run on hydrogen. I would be very disappointed if engines that must run on hydrogen will just be substituted for liquid fuel. And I liquid hydrogen is in the game then engines such as the vector and nervas run on hydrogen in the real world.

Yes, metalic hydrogen will be its own fuel. So will fusion rocket fuel. 
An obvious benefit of liquid fuel and oxidizer is that its much easier to ISRU down to melting ice and splitting water molecules.  than metalic hydrogen who will require an specialized factory to create. 

Edited May 17, 2020 by magnemoe

[afafsa]

5 hours ago, Bej Kerman said:

Changing liquid fuel to x is rather pointless and doesn't make the game any deeper. It just makes things more complicated.

Except that it does make the game deeper. There are real and interesting trade-offs between engine types that translate into design considerations, particularly with how one approaches colonizing different bodies.

Kerosene is a cheap, dense, high-thrust fuel that is essentially impossible to manufacture off Earth. Liquid hydrogen is relatively easy to manufacture off-planet, you just need water, but doesn't have great thrust and requires massive tanks due to its low density. Methane is a decent trade-off, but requires CO2 or some other carbon source, which is abundant on Mars/Duna, but not on the Moon/Mun. These directly reflect how a player would approach engineering a spacecraft and what bodies the player would choose to colonize, and solving engineering problems is the whole fun of the game.

I think the primary problem is that the community in this forum is old and from the days when KSP was just a whimsical simple rocket simulator (myself among them). It has grown considerably since then, but there's a small, vocal group that seems to want nothing to change.

[SpaceFace545]

1 hour ago, afafsa said:

Except that it does make the game deeper. There are real and interesting trade-offs between engine types that translate into design considerations, particularly with how one approaches colonizing different bodies.

Kerosene is a cheap, dense, high-thrust fuel that is essentially impossible to manufacture off Earth. Liquid hydrogen is relatively easy to manufacture off-planet, you just need water, but doesn't have great thrust and requires massive tanks due to its low density. Methane is a decent trade-off, but requires CO2 or some other carbon source, which is abundant on Mars/Duna, but not on the Moon/Mun. These directly reflect how a player would approach engineering a spacecraft and what bodies the player would choose to colonize, and solving engineering problems is the whole fun of the game.

I think the primary problem is that the community in this forum is old and from the days when KSP was just a whimsical simple rocket simulator (myself among them). It has grown considerably since then, but there's a small, vocal group that seems to want nothing to change.

Literally everything you have said is true especially the part about the group that doesn’t want to change even though it would likely be for the good.

[Bej Kerman]

15 hours ago, afafsa said:

I think the primary problem is that the community in this forum is old and from the days when KSP was just a whimsical simple rocket simulator (myself among them). It has grown considerably since then, but there's a small, vocal group that seems to want nothing to change.

I do want things to change, just that things that aren't broken don't need fixing.

[shdwlrd]

16 hours ago, afafsa said:

I think the primary problem is that the community in this forum is old and from the days when KSP was just a whimsical simple rocket simulator (myself among them). It has grown considerably since then, but there's a small, vocal group that seems to want nothing to change.

The reason you don't hear a ton of players crying for complexity is the players are content with the way things are. If you're happy, you won't complain and remain silent. 

Think about the player base, the number of players calling for more complexity, and the number of players saying no. Now the silent part is either happy the way things are, or could care less what happens. (Until something happens they don't like, then will say something.)

[afafsa]

1 hour ago, Bej Kerman said:

I do want things to change, just that things that aren't broken don't need fixing.

 

38 minutes ago, shdwlrd said:

The reason you don't hear a ton of players crying for complexity is the players are content with the way things are. If you're happy, you won't complain and remain silent. 

Think about the player base, the number of players calling for more complexity, and the number of players saying no. Now the silent part is either happy the way things are, or could care less what happens. (Until something happens they don't like, then will say something.)

I don't mean for this to be harsher than it is, but this is fundamentally a disagreement between those who recognize that a solar system becomes a lot less interesting when you eliminate its inherent diversity of resources, and those that are apparently overwhelmed by 6th grade chemistry concepts. On an absolute scale, KSP is not a complicated game. Saying the word "methane" is not going to break anyone's brain. The engineering considerations of different fuels make for inherently good gameplay, and I'm excited about the educational possibilities KSP2 opens up.

Ultimately this is a moot point anyway. From the dev diaries, we've seen they're going in the direction of things like "cesium doped metallic hydrogen," which is further than even I would argue is necessary.

[Guest]

Complexity for the sake of complexity or realism is useless, but complexity for the sake of gameplay could be fun.

New players are not a problem, you can start the game with Kerolox and solid boosters like is now, ad Hydrolox when developing the IRSU on Mun-Minmus bases and the Methalox when making the first bases on Duna-Eve and then gradually adding the more exotic fuels.

[SciMan]

I've given this a bit more thought, and my opinion has changed. We might need two fuels to fully represent what Liquid Fuel is. Because to be quite honest, I agree with the argument that fuel cells and the LV-N Nerv (and maybe even the Mammoth and Vector) should use Hydrogen, which would be less dense than the current Liquid Fuel.

The only reason I'm opposed to splitting out further between Methane and Kerosene is that it would make many of the engines already in the game only able to be re-fueled by landing back on Kerbin or another life-bearing and geologically active planet. Of course that is unless they decide to make any engine able to use any fuel by configuration in the VAB, but then the question becomes "why did you bother adding in all that complexity when the end result is the same?". Sure it would be more realistic but it's just a lot of effort for minimal gain.

When you have a fundamental difference in how the rocket engine works, that is a good enough reason to have a different fuel.
Therefore, it makes sense to have a different fuel for the LV-N, the Orion drives, the Metallic Hydrogen engines, the fusion drives, etc.

However, for most of the rocket engines in KSP1, they all work pretty much the same. The plumbing (which rocket engine cycle they use) may be different between them, but they all take in fuel and oxidizer, combust it, and expel the reaction products out the exhaust nozzle to create thrust.
So for that purpose, with the exceptions of the KS25x4 Mammoth and KS25 Vector which are inspired by real life hydrogen-oxygen (hydrolox) engines, all the other combustion-based engines could be said to use the same generic "LiquidFuel" fuel and "Oxidizer" oxidizer.
Note I said "combustion-based engines", that excludes the monopropellant engine, LV-N Nerv, and the ion engine.

The only reason the KS25x4 Mammoth and the KS-25 Vector would get special treatment is because they are inspired by real life hydrolox engines.
Obviously this would mean that they would both need balance changes since they are changing what fuel they use.
My thoughts are that the Vector should have the following stats: Sea-Level ISP 320s, Vacuum ISP 370s, Vacuum Thrust 750 kN, Mass 3.25 ton (I kept the vacuum TWR very close to what the original is in KSP1).
As for the Mammoth, it would have the following stats: Sea-Level ISP 320s, Vacuum ISP 370s, Vacuum Thrust 3000 kN, Mass 14.0 ton (I kept the vacuum twr as close as possible to what it is in KSP1, with a caveat explained below).
Yes, I reduced the mass of the Vector some. There's a reason for that. For some reason when you take a Mammoth apart you end up with this magical massless thrust structure and aerodynamic shroud that the 4 Vectors mount to. I'm reducing the Vector's mass some to account for that and give that part some mass.

Side thought, it would also be nice if we had another structural part that looked just like the Mammoth's engine mount but let you put whatever you want where the 4 engines go. Also would be nice to have a single engine KR-1 engine from the Twin-Boar, minus the structural mass of the tanks and one of the engines of course (that way we don't have to go over the same ground I just went over with the Mammoth and it's magical massless thrust structure).

It would be nice to have an RL-10 analogue as well, since IRL it's made by Rocketdyne, I'd have it be made in-game by Kerbodyne and I'd call it the "KL-10" (you think up a nickname for it tho, that's beyond me at the moment).
This would be a vacuum optimized small hydrolox engine that is great for clustering, and would be unlocked before the Mammoth and Vector in the tech tree. IRL, the RL-10 gets very close to 465s vacuum ISP at 110 kN thrust (and just 277kg mass, or 0.277 metric tons) so the one for KSP might be a small-ish engine with around 400s vacuum ISP, 75 kN vacuum thrust, and maybe 0.5 tons mass (I kinda hate how everything in KSP is made of lead, but I guess that's how you limit delta-V when the solar system is so tiny). Size would be 2.5m diameter with the "tank-butt", with an alternate version available for 1.875 tanks, and a 1.25m "bare" size for clustering.

The low thrust of the hydrogen engines would be partially offset by the lower mass of the Hydrogen part of the fuel.
Just like IRL, a rocket stage using hydrolox would be simultaneously larger and less massive when fully fueled compared to a rocket stage of similar delta-V using kerolox or Methalox.

[Tweeker]

       I don't think it is strictly necessary to change to real life fuels, but it would be nice to have a few more realistic options. 

Alot of the fuels can be condensed into groups based on how dense they are, how storable they are,  and how well they perform,  

In KSP currently you have, 

Monoprop, 

Solid fuel, 

Liquid fuel/oxidizer which is a rough analog of hypergolics

LFO for the LV-N, 

and Xenon. 

Generally speaking I am a proponent of keeping things simple,   But I think there is value in adding an analogue for cryonic fuels,  and a "fluffier" fuel as a LH analog. 

Most of the hypergolic fuels, and KER/LOX  are of similar density, and produce about the same ISP, ~290 to 340, and I think could be considered to be "liquid fuel"   LH/LOX is about 3X fluffier than this, but produce 400-460 ISP, and could be represented by a 2nd type of liquid fuel. The LFO Nerva should have propellant that is 7X fluffier than it currently is, LH being 7X  less dense than kerosene. CH4/LOX seems to slot in between the 2, Being slightly significantly denser than LH, and providing ISP in the 330-380+ range.  

So maybe 8 fuels,

Monoprop,

Solid Fuel,

LF 1 ---- A Ker/lox or hypergolic analog, 300-330 ISP

LF 2 ---- A LH/LOX Analog, 3X  less dense 375-430 ISP 

LF 3 ----  A Meth/LOX analog, Maybe 1.2X less dense than LF 1 {a  guess}  and 320 to 370 ISP. 

LFO --- NERVA and NTR rockets, 7X less dense than it currently is. 

Xenon. 

Future fuels such as Metallic hydrogen. 

 

In my experience most real life engine can be converted to KSP fairly simply,  divide the  IRL engine thrust by either A) (1000 for LBF) or  b) (4.5 for KN) to get KSP thrust. ISP seems to vary a bit  for KSP engines compared to  real life, Clydesdale has  235 VS 242 isp --- 3% lower, the Mainsail/Mastosdon  have a  ISP of 280-290 SL, VS 260 for the F1.   I think real world ISPs could translate  with a 5-10% reduction.   

It is important to remember the Mammoth's stats were badly distorted by the fact that the kickback was greatly undersized for the job when it was rolled out in  0.23.5. The mammoth was greatly overpowered to compensate for this. When the Vector was split of from the Mammoth in 1.0.5  it was likewise OP.  Now that there is a proper booster in the form of the Cyldsdale, it is possible to re-scale the mammoth and booster. 

The Vector/ Mammoth for example should have stats more like this:

1.875M engine ~75% scale.   

SL ISP, 330-350, 

Vac ISP 405-430

SL Thrust  420

Vac thrust 510

for the Mammoth  thrust would be 1680 SL, 2040 vac. 

An RL-10s are difficult to characterize because there have been SO MANY of them, however almost all of the have ~25,000 LBF thrust and  ~450 Vac ISP.  They are very rarely used at sea level, with the exception of the   RL10A-5. IRL RL10s  have a nozzle diameter  betweens 1.16 and 2.1M, and KSP seems to be about 66% scale so 2.5M would be vastly oversized. 1.25M seems workable., then they could make 2.5m  or 3.75m clusters like the Centaur, DUUS or EUS  or ICPS. 

At a guess  it should have stats something like this:

1.25m  ~66-75% scale. 

SL ISP 300-320,

Vac ISP 420-435

SL Thrust 10

Vac Thrust 25

I would like to see the option to switch out nozzles for different applications, for example having a sea level nozzle that is more compact, but lower thrust.  Then a vacuum nozzle  that make poor sea level thrust, and ISP, but is good in space. Maybe even an Eve optimized nozzle.  

 

--Just my 2 cents. 

 

 

 

 

 

 

[NoMrBond]

A basic split of fuel types should work, since you're going to have multiple fuel types later on KSP2 should introduce them throughout the game on to get players used to the idea (and also that you need to bring the right fuel for the chosen propulsion/engine/s)

A super simplified Hypergol & LF (RP-1) & Cryo (LH2) with Ox staying the same throughout may work. Perhaps being LOx and applicable everywhere, which is a bit of a stretch but would cover basically everything up to almost current era with some research progression.

Maybe you want to go a step further and give Hypergolics their own oxidiser (engines and bipropellant RCS using the hypergol F/O, and monopropellant RCS using the hypergol-fuel), but that leaves hypergolic oxidiser fairly lonesome with little other commonality. Can you live with a semi-orphan resource/chemical, or tolerate oxidiser commonality?

But what about mechanics, does stuff boil off, or freeze, what are your reasons for each fuel and what game purpose does it serve (if Ox being LOx is going to boil off, then you can argue to keep Hypergolic Ox which doesn't boil off since it occupies a game niche rather than become redundant).

Need to consider what works at a game level without making things a chore as well, but a lot of that could be hidden behind difficult (i.e. abstracted fuel/ox like present at low difficultly, with more complexity as difficulty increases, but that's added complexity plus all that needs balancing)

[Dirkidirk]

On 5/29/2020 at 3:50 PM, SciMan said:

I've given this a bit more thought, and my opinion has changed.

same.

[desert]

On 5/17/2020 at 7:13 PM, GluttonyReaper said:

In my mind, this is the problem with hydrazine and methalox engines.

You are making good points about them, now I am less sure we need these fuels :-)

On 5/17/2020 at 7:13 PM, GluttonyReaper said:

It's more expensive and much less dense than Liquid Fuel, but has a much higher ISP, which makes it plenty distinct enough

Yes, and making orbital depots with huge solar panels, radiators and maybe even engineers to reduce boil-off will be interesting. The only problem with LH is that we will have two different fuels named specifically after Hydrogen: Liquid and Solid, while usual fuel will remain generic Liquid Fuel. It seems like disproportion. Maybe calling LH just "Cryogenic Fuel" will be better?

[Pthigrivi]

On 5/29/2020 at 3:50 PM, SciMan said:

The only reason I'm opposed to splitting out further between Methane and Kerosene is that it would make many of the engines already in the game only able to be re-fueled by landing back on Kerbin or another life-bearing and geologically active planet. Of course that is unless they decide to make any engine able to use any fuel by configuration in the VAB, but then the question becomes "why did you bother adding in all that complexity when the end result is the same?". Sure it would be more realistic but it's just a lot of effort for minimal gain.

I think this is the right balance--keeping a generic "liquid fuel" stand-in for hydrocarbon fuels and adding LH2 for more advanced liquid rockets. The other advantage as others have pointed out is the former could be produced in situ on bodies with ice and the latter could be produced with CO2 atmospheres (Duna and maybe Eve?). I know this is more controversial but I also like that this could feed into a life-support resource. The chemistry itself could be abstracted and simplified and still retain the basic principal--that LF/O can be converted into "life-support" and back using electricity. I also think for simplicity you could have a single generic nuclear fuel which could be used by NERVAs, Nuclear reactors, and maybe later fusion engines. That would give you the following resources:

Monoprop
Solid Fuel
Liquid Fuel
Oxidizer
Hydrogen
Nuclear Fuel
Xenon
Metalic Hydrogen
Electricity
Life Support

With these potential conversions:

E + ISRU processor = M, H2, O

E + IRSU processor + Atmospheric processor = LF

E + ISRU processor + Nuclear processor = NF

E + ISRU processor + Greenhouse = LS

E + Atmospheric processor = O, X

NF + Nuclear reactor = E

H2 + O + Fuel Cell = E

LF + O + E + Life support converter = LS (and back)

H2 + NF + Hydrogen Metalizer = MH

Im tempted to separate out water and food for this but folks go ballistic when you suggest we should have any life support let alone a 2 part resource. I also figure if we're building parts from mined resources we'll want Ore + a couple of consolidated crafting resources, maybe Metals, Polymers, + Rare Elements. Most parts would just be metallic, with polymers for living spaces + spaceplane parts and rare elements for fancy engines and equipment. This would keep mineable resource values differentiated without ending up with too many. If an area is high in ice you can produce more H2 + oxidizer, high in carbon for polymers and LF + LS, or high in metals for metals, rare elements, + nuclear fuel. With 3 overall values you'd have to think a bit about the best places to set up shop and you'd be incentivized to build supply connections between colonies to provide any resource that's lacking. 
 

Edited June 2, 2020 by Pthigrivi

[Selective Genius]

I just want to play a fun goofy space simulator, not a rocket engine design simulator..... Tbh, it would be far more interesting if KSP2 keeps the fuel resources same, but allows us to change the Oxidizer/Fuel mixture ratio. That in itself would open up a lot of opportunities...

[Kerbart]

More fuel realism? No thank you. Kerosene freezing up because your kerosone tanks are sandwiched in between liquid O₂ tanks, highly corrosive hypergols eating away your tanks when staying too long on the platform, Jeb killing everyone onboard including himself because he returned from an EVA covered in Hydrazine? It sounds like fun until yet another Duna mission gets ruined by a corroded tank.

More fuel challenges? Absolutely! Even a simple distinction between Hydrazine, Kerosene, H₂ and O₂ (and Xenon gas of course) would add some interesting considerations to building spacecraft and stations. It would also revive the tech tree as better-but-harder-to-tame fuel combinations become available later in the game.

[Jacke]

On 6/1/2020 at 9:29 PM, Kerbart said:

...highly corrosive hypergols eating away your tanks when staying too long on the platform....

That problem was solved in the 1950s.  It's why the oxidizer became IWFNA and IRFNA.  N₂0₄ has this problem even less.  AFAIK, the fuels (Hydrazine, UDMH, 50-50, MMH) never had tank corrosion issues.  How to formulate them, how to tank and transfer them are solved problems.  They really became storable.  As in years.  Toxic, hell yes.  Tricky to handle, all propellants are one way or another.