[1.8+] Real Fuels

[regex]

What on EARTH are you talking about?

The *only* thing you could argue is unrealistic is that there is just a single ISRU refinery part that "does it all"

10 characters

[Northstar1989]

10 characters

May I remind you that all the functions *could* realistically fit into a 5-meter diameter ISRU refinery (not a 2.5 meter one, but remember, KSP parts are 50% or less real-world scale...)

Regards,

Northstar

[regex]

May I remind you that all the functions *could* realistically fit into a 5-meter diameter ISRU refinery (not a 2.5 meter one, but remember, KSP parts are 50% or less real-world scale...)

And? My statement still stands: "you could probably make a case for Interstellar". You clearly have, good for you.

[Starwaster]

May I remind you that all the functions *could* realistically fit into a 5-meter diameter ISRU refinery (not a 2.5 meter one, but remember, KSP parts are 50% or less real-world scale...)

Regards,

Northstar

While I have certainly spoken out on behalf of integrating Real Fuels with just about anything you might want to integrate it with, your expectations aren't realistic. If you want to say that you're abstracting your monolithic universal refinery into a 2.5m part for the sake of gameplay, that would be a reasonable thing to say.

Sabatier reactors need to be scaled up to be useful for anything more than supplying a handful of astronauts with drinking water and breathable oxygen. Because that's what your fridge sized unit is doing. Do you want to use it to produce methane for rocket fuel? You're going to need something substantially larger. And that's just to produce enough methane over a period of months in advance of a small team of explorers in a small ship to escape Mars and return to Earth. (less so if they have a ship waiting in orbit to take them back. More so if their return vehicle also has to carry them back to Earth)

Harvest uranium from seawater? With just a centrifuge? Not even remotely. The process (still experimental with today's technology) is far more involved than that requiring the use of consumables in the form of materials to bind the uranium to fibrous mats and then more to wash the uranium out. How long does that take? How much of it is reusable and how much is consumed in the process? Do you even know? Does Interstellar's creator even know? (it seems unlikely if they think that all you need is a centrifuge)

I could go on, but honestly there's no point to it. I already provided you with all the justification you need to pursue Real Fuels integration. If you want to drag realism into this then it's a losing proposition because it's NOT realistic. But that's ok because when it comes to game design it's perfectly ok to abstract things. Unless you're Derek Smart.

[dreadicon]

Regarding RealFuels, KSPI, and realism, another point to keep in mind is that KSPI has a fusion reactor, an antimatter reactor, and a warp drive. KSPI is what is known as "Hard SciFi". It's very firmly inspired by real science, but many of the things it does are just past the realm of tested science and into the realm of hypothesis and near-fiction. Nothing wrong with that; in fact I quite like it! I love to see what's just over the horizon technologically, what would happen if hypothesis became tested practice. It's also fine to take some liberties like improving the tested stats to make it game-viable without game-breaking. But when it comes to these liberties, we will all, always, have to agree to disagree when we see things differently. If talking hard science, it must be kept as hard science.

In KSP, fusing too many parts together is arguably tantamount to cheating in some people's eyes. It's why I don't use mods that add space shuttles in 4 parts; what's the point? It's all designed to fit together in one way, for one purpose, with highly limitted options. As an engineer, I see that as, if not cheating, a pointless mod for myself. No offense to those who would rather focus on flying missions, but my joy is in seeing the craft I built work beautifully, and if it's all just a prefab 'magic box' part, then how is it my creation? I never followed directions for lego sets as a kid, because if I did then it wouldnt have been my creation! So that is my KSP. If yours is different, that's fine. More than fine, it's great! You probably fly more missions and go more places than I do, typically holed up in the VAB/SPH for hours on end perfecting every aspect. We all enjoy the game in different ways. Rejoice that most of your wants and needs for KSP have been taken care of for you by the amazing community, no matter what kind of a player you are!

Now, before we get too far off topic here, let me just say that I love RealFuels. For me it is the golden standard for resources and realism. I am working on some code to try and implement fuel-filled wings for Procedural Dynamics specifically for Real Fuels tanks. Not easy though; his code is kinda like spaghetti xD very hard to make a standalone addon that doesn't trample it, lol.

[NathanKell]

Oh snap! I keep meaning to do that, and never getting around to it. Send me a PM, or find me on IRC (easier, because realtime) and let's chat about that.

(Wet wings)

[Northstar1989]

Wet wings would be awesome!

@Starwashed

I wasn't aware of the difficulties in Uranium extraction, Starwasher, although the ways to extract nuclear fuels offworld always seemed to be the questionable ones to me...

But there's no oversimplification that goes into the Sabatier or Anthaquinone Reactions being able to take place in very small units. Rate of reaction is another matter entirely, but the KSP-Interstellar refineries actually work at quite a slow pace (it will take MONTHS in time-warp to fill a large rocket). And, I have to remind you, whenever we're talking scale, everything in KSP is 50% scale. so if it's 2.5 meters in Interstellar, it's 5 meters in real life. In a 5 meter refinery you can EASILY fit a decent-sized Sabatier. If a unit to serve a handful of astronauts (and by the way, even that unit could produce a rather substantial volume of methane over the course of a few months, if provided with enough CO2/H2O and electricity- the unit on the ISS only operates at a *fraction* of its rated capacity...) is only the size of a *mini* fridge (not a full-sized fridge, let's get this straight), then one taking up, say, a third of the volume of a 5 meter refinery, could work a lot faster.

And in KSP-Interstellar, size DOES matter. You usually need either a 3.75 meter refinery or two 2.5 meter refineries to meet really high fuel demands...

@Dreadicon

It's Hard Science Fiction alright, but the hard Scifi of today is often the scientific commonplace of tomorrow. Especially when what's in KSP-Interstellar goes beyond merely plausible- most of this stuff has been the subject of extensive engineering studies PROVING its viability- and there are just certain missing materials or devices that we need to wait to be developed, but are sure will one day be around. The exception to this, of course, is the warp drive- but even NASA took that seriously enough to decide to encourage the scientists who were looking into it with a little conceptual art...

I don't play with mods like the 4-piece shuttles by the way. I often spend hours in the VAB/SPH as well. But for the sake of my poor old CPU, merging 9 or 10 different pieces of SMALL ISRU equipment into a single refinery part is probably a good idea. And like I said, FractalUK has given some thought to possibly making it tweakable in the future as to what the loud-out is of a given ISRU refinery...

By the way, shoot me a PM- what's the status of that integration config? We need to make sure the MM engine part patches are kicked over to Raptor831 in the "Stockalike" engine config (not just the Raptor engine- which I still want to fix the TWR and ISP for- but also the Aluminum Hybrid Rocket and DT-Vista, which AFAIK only need their resource names changed), whereas the fuels stuff goes to NathanKell/Regex for addition to the main thread. And, what was it you were talking about regarding the conversion rates for Ammonia?

Regards,

Northstar

Edited October 25, 2014 by Northstar1989

[BLUAV8R]

Sorry if this has already been answered, but using this pack and the stockalike configs and engine packs, I find that all tweakscale capabilities on engines are no longer visible or changeable, anybody know why?

Any help is appreciated!

[NathanKell]

Working as designed.

[mdosogne]

mdosogne: nuke RF and TS; redownload both fresh; install TweakScale; install RF. That should work, and if it doesn't, please let me know on the RF thread.

Reinstalling didn't help, but I did find a fix/workaround: I moved TweakScale_RealFuels.dll from GameData/TweakScale/TweakScaleInteraction into GameData/TweakScale/plugins/ and it now seems to work.

[Felbourn]

I was reading about the V2 and saw it used 75% ethanol and 25% water for fuel. I then looked up ethanol and saw it was 0.789 kg/L. I looked in the RealFuels config and saw an entry for Ethanol75 indicating the exact same fuel mass. I'm confused by that though, since if Ethanol75 is only 75% ethanol and 25% water then shouldn't the mass be (0.75 * 0.789) + 0.25 = 0.84175? Or am I supposed to add a tank of water to balance out the mass if I were going to make V2 fuel? Or is the Ethanol75 already accounting for that like this: (0.75 * 0.71867) + 0.25 = 0.789?

[Northstar1989]

@NathanKell

Any progress about fixing the boil-off equations to be based on the 4/9th power of tank surface area rather than proportional to maximum volume?

Also, we still *really need* the ability to actively cool tanks to reduce boil-off (several such systems have been designed for spacecraft fuel tanks in real life- just not implemented, as it is only useful for deep-space missions or fuel depots using cryogenic fuels, and works best with large craft rather than probes- as the cooling equipment doesn't scale down very efficiently mass-wise, and smaller craft require relatively more cooling for their volume due to the Square-Cube Law to begin with...)

The cooling equipment could be a separate part radially/stack-attached to the fuel tanks it cools, or somehow built into the fuel tanks themselves. If it were a separate part, it should come in two sizes- a large and a small variant, with the larger variant being more powerful for its mass to reflect reality (REALLY BIG fuel tanks should need multiple large units, and would thus fail to benefit further, though).

The balance of cooling requirements also needs to be account for the Square-Cube law and tank geometry- i.e. cooling requirements should be proportional either to tank Surface Area (if there is a way to find that directly) or the 2/3rd power of tank volume (the exponent at which heat leakage scales- boil-off is proportional *both* to heat leakage and the available surface area for fuel to leak through, and thus the 4/9th rather than 2/3rd power though...) And cooling a tank should reduce (to about 1/10,000th the normal rate) but not eliminate boil-off, like in real life- so larger tanks would still experience relatively less boil-off, and tanks of any finite size could still not hold cryogenic fuel indefinitely.

A final note- saying heat leakage scales with the 2/3rd power of tank volume is a *very* rough approximation, even with a cuboidal or cylindrical fuel tank. This is because fuel tanks are essentially pressure vessels (internal pressure vs. vacuum of space), and their walls become thicker the relatively less surface area they have for their volume (this is also why their mass scales linearly with volume, rather than with the Square-Cube Law). So larger tanks not only have relatively less surface area, they also have thicker tank walls- which are inherently better at insulating the fuel (a 2-inch thick aluminum sheet is a better insulator than an aluminum sheet a few cm thick...) And if you add actual insulation (most real fuel tanks have at least a little light added insulation), the insulation mass is spread over a relatively smaller surface area- which means the same relative mass of insulation will be coated on in a thicker or larger number of (thus more effective) layers... In short- heat leakage scales at *LESS* than the 2/3rd power of volume...

Regards,

Northstar

P.S. One of the subtle, and not-so-obvious consequences of scaling heat leakage with the 2/3rd power of tank volume, and overall boil-off with the 4/9th power, is than two 1000 L tanks laid end-to-end actually experience slightly more boil-off than a double-length tank with 2000 L volume. This is actually both expected and accurate/realistic- the longer tank would actually have thicker outer walls than the shorter tanks. Taken to an extreme, compare the wall thickness of, say, a single monolithic tank, and a honeycomb structure of smaller tanks with the same total volume (remember, tank mass scales linearly with volume- and larger tanks require thicker walls) to see drastic differences in outer wall thickness...

Edited October 27, 2014 by Northstar1989

[regex]

I was reading about the V2 and saw it used 75% ethanol and 25% water for fuel. I then looked up ethanol and saw it was 0.789 kg/L. I looked in the RealFuels config and saw an entry for Ethanol75 indicating the exact same fuel mass. I'm confused by that though, since if Ethanol75 is only 75% ethanol and 25% water then shouldn't the mass be (0.75 * 0.789) + 0.25 = 0.84175? Or am I supposed to add a tank of water to balance out the mass if I were going to make V2 fuel? Or is the Ethanol75 already accounting for that like this: (0.75 * 0.71867) + 0.25 = 0.789?

I didn't change or check existing fuel density, sorry for that. We renamed Alcohol to Ethanol75 as that is what NathanKell indicated he had originally intended so I suppose it should be corrected to the proper density. Encyclopedia Astronautica indicates it should probably be 0.87g/cc.

[cremasterstroke]

@NathanKell

Also, we still *really need* the ability to actively cool tanks to reduce boil-off (several such systems have been designed for spacecraft fuel tanks in real life- just not implemented, as it is only useful for deep-space missions or fuel depots using cryogenic fuels, and works best with large craft rather than probes- as the cooling equipment doesn't scale down very efficiently mass-wise, and smaller craft require relatively more cooling for their volume due to the Square-Cube Law to begin with...)

The cooling equipment could be a separate part radially/stack-attached to the fuel tanks it cools, or somehow built into the fuel tanks themselves. If it were a separate part, it should come in two sizes- a large and a small variant, with the larger variant being more powerful for its mass to reflect reality (REALLY BIG fuel tanks should need multiple large units, and would thus fail to benefit further, though).

Erm, there's a thermal fin (under the Science tab) that already does that - there's only one size, but it should be easy to make a cfg for larger/smaller versions, or just use multiple.

[Starwaster]

Erm, there's a thermal fin (under the Science tab) that already does that - there's only one size, but it should be easy to make a cfg for larger/smaller versions, or just use multiple.

It doesn't currently work properly though. There's still some issues with the code and the part's config.

[Felbourn]

I didn't change or check existing fuel density, sorry for that. We renamed Alcohol to Ethanol75 as that is what NathanKell indicated he had originally intended so I suppose it should be corrected to the proper density. Encyclopedia Astronautica indicates it should probably be 0.87g/cc.

Thanks for checking on it. I'll MM a change to it locally.

[Northstar1989]

@NathanKell/Regex

Some crew capsules (in stock, NovaPunch2, and Firespitter) that carry Monopropellant currently haven't yet been configured to carry Hydrazine or act as Modular RCS Tanks (so that we can choose which RCS fuel we want to use, instead of being limited to just Hydrazine) yet.

This (along with the fact the KSP-Interstellar's ISRU produces Monopropellant, not Hydrazine, and Dreadicon's new integration config hasn't done anything to fix that yet- something I *just now* left him a post about on his dev thread...) is one of the main issues holding me back from switching over to ModuleRCSFX instead of continuing to use Monopropellant.

Currently, I have ModuleRCSFX deleted, as per the instructions on the "Stockalike" engine config (which still hasn't yet done anything to fix the O-10 Monopropellant engines to be able to use RealFuels RCS resources such as Hydrazine) in order to use Monopropellant instead as a result, but would like to be able to switch over to realistic RCS fuels relatively soon...

Regards,

Northstar

[Lilienthal]

Hi Nathan and all,

could I suggest to lower the costs of ElectricCharge and SolidFuels? As mentioned in a post above, ElectricCharge can now be a huge factor in cost of vessels. (At least in RO). Charging a battery costs more than the battery itsself. IMHO it would make the game more balanced if it is lowered by two orders of magnitude (i.e. *=0.01) or even set to 0.

Similarly, I found that using solid state rockets is totally not economic with the very high price of solidstate fuel. It is now about 1000 times or so more expensive per kg, than e.g., kerosene.

Unfortunately, I don't know the units you are using for prices, so it is difficult for me to propose a value. Edit: I now saw in release notes: 1 fund = $1000 in 1965 US Dollars.

@RESOURCE_DEFINITION[ElectricCharge]:FOR[RealFuels]

{

@density = 0

@unitCost = 0.05

}

@RESOURCE_DEFINITION[intakeAir]:FOR[RealFuels]

{

@density = 0.001

@unitCost = 0

}

@RESOURCE_DEFINITION[solidFuel]:FOR[RealFuels]

{

@density = 0.00178

@unitCost = 0.4005

}

Edited October 28, 2014 by Lilienthal

[Northstar1989]

Hi Nathan and all,

could I suggest to lower the costs of ElectricCharge and SolidFuels? As mentioned in a post above, ElectricCharge can now be a huge factor in cost of vessels. (At least in RO). Charging a battery costs more than the battery itsself. IMHO it would make the game more balanced if it is lowered by two orders of magnitude (i.e. *=0.01) or even set to 0.

Similarly, I found that using solid state rockets is totally not economic with the very high price of solidstate fuel. It is now about 1000 times or so more expensive per kg, than e.g., kerosene.

Unfortunately, I don't know the units you are using for prices, so it is difficult for me to propose a value.

@RESOURCE_DEFINITION[ElectricCharge]:FOR[RealFuels]

{

@density = 0

@unitCost = 0.05

}

@RESOURCE_DEFINITION[intakeAir]:FOR[RealFuels]

{

@density = 0.001

@unitCost = 0

}

@RESOURCE_DEFINITION[solidFuel]:FOR[RealFuels]

{

@density = 0.00178

@unitCost = 0.4005

}

Those appear to be per-unit prices. Mutliply the number of units by the density to get the mass for the SolidFuel (in metric tons, I believe.) So, just figure out the number of units that comprises a metric ton with the current density settings, and compare them to real-world prices to figure out if they're accurate. My guess is they're too high, based on their relative pricing per-ton to Kero/LOX... (which only comprises 0.3% of the launch costs of a Space-X Falcon 9)

As for the Ec, it has been heavily debated what the units are supposed to stand for. KSP-Interstellar make the (slightly generous) assumption that each Ec represents a kW, based on cutting-edge modern-day solar technology (of the sort used on spaceships- where the very best solar panels available are typically used) and everything being Kerbal-scale, whereas estimates based on the MUCH less efficient photovoltaic technology of the 1960's/70's and taking the soalr panel area as what it actually is rather than a downsized version of real panels leads to an estimate of each Ec unit being about 3.3 Watts...

@NathnaKell

Also, any news on fixing the crew capsules that still carry only Monopropellant? That should be a base-mod fix, rather than anything to do with one of the engine configs...

Regards,

Northstar

Edited October 28, 2014 by Northstar1989

[Lilienthal]

Those appear to be per-unit prices. Mutliply the number of units by the density to get the mass for the SolidFuel (in metric tons, I believe.) So, just figure out the number of units that comprises a metric ton with the current density settings, and compare them to real-world prices to figure out if they're accurate. My guess is they're too high, based on their relative pricing per-ton to Kero/LOX... (which only comprises 0.3% of the launch costs of a Space-X Falcon 9)

so, the price for solid fuel seems to be .4005/1.78 = $225 per kg or $400.5 per litre (1965 US$) Probably somewhat high. Also definitely making sure nobody uses solid states anymore.

Liquid oxygen is 4.564 Ct/litre. and 0.001141 4 Ct/kg.

As for the Ec, it has been heavily debated what the units are supposed to stand for. KSP-Interstellar make the (slightly generous) assumption that each Ec represents a kW, based on cutting-edge modern-day solar technology (of the sort used on spaceships- where the very best solar panels available are typically used) and everything being Kerbal-scale, whereas estimates based on the MUCH less efficient photovoltaic technology of the 1960's/70's and taking the soalr panel area as what it actually is rather than a downsized version of real panels leads to an estimate of each Ec unit being about 3.3 Watts...

Not meaning ot overly patronizing, but the electricityResource hast to have a unit of energy, not power, so neither of those units can be true for the electricityResource. Anyway, my suggestion would be to set the costs just to 0. We also don't cost the electricity for lighting the place etc.

[NathanKell]

1. Solid fuel is weirdly high, yes. Not sure quite what I was thinking, it should be about $12-15 per kg (based on series production of UA1205s, assuming about half the cost is the fuel, half the casing, which IIRC is about right.)

2. RealFuels considers 1EC to be 1 kJ. It's that simple. That said, I have very limited information on how much (space) batteries cost in 1965. But I agree that $50/kJ is probably too much. Does $1800 per kWhr sound about right?

Northstar1989: Yes, thank you for that explanation. The problem is that if I simply declare boiloff to be the 4/9th power, it will mean that to get realistic boiloff for large tanks, it will be impossible to create fuel cells that don't boil everything off very quickly. In real life, insulation mass is going to be increased for the small tanks to prevent that, and I'm really unsure I want to go so far into the details as for RF to model insulation mass, *especially* given that it cannot know surface area except by the roughest approximation.

As to the capsules: Yes, I'm aware, I saw when you mentioned it the first time, and thanks! (And if you check git, you'll see regex has added most missing stuff; I have to do a final pass to check everything and we're good to go). Please don't pester, though, all it makes modders want to do is delay the updates... >.>

[Rabada]

I have a couple quick questions regarding liquidhydrogen boiloff and Exteroir Thermal Fins.

1) I believe I read that with enough Exterior Thermal Fins it is possible to reduce the hydrogen boiloff in my cryogenic tanks to 0. Is this true?

2) What is the ideal temperature range for liquid hydrogen Cryogenic tanks? In other words, how many Exterior thermal fins should i add to these tanks?

[Lilienthal]

1. Solid fuel is weirdly high, yes. Not sure quite what I was thinking, it should be about $12-15 per kg (based on series production of UA1205s, assuming about half the cost is the fuel, half the casing, which IIRC is about right.)

sounds reasonable. Once I am back at my desktop, I'll design a few more rockets and what are the design choices resulting from this.

2. RealFuels considers 1EC to be 1 kJ. It's that simple. That said, I have very limited information on how much (space) batteries cost in 1965. But I agree that $50/kJ is probably too much. Does $1800 per kWhr sound about right?

IMHO, the price of EC should not include the battery, only the cost to charge it. Battery price should be included in the costs of the "tank", shouldn't it. Then $0.50 sounds about right for 1 kWh. Or did I miss something?

[Lilienthal]

The boiloff rate is calculated for Hydrogen using:

loss= tank.maxAmount * tank.loss_rate * (Temp-(-253 C))* deltaTime;

So if I understand it correctly (@Nathan, please correct if wrong), you need to cool the hydrogen tank to -253C to stop boiloff. For Oxygen the temp is -183C

cf: https://github.com/NathanKell/ModularFuelSystem/blob/master/RealFuels/Resources/RealTankTypes.cfg

[Starwaster]

I have a couple quick questions regarding liquidhydrogen boiloff and Exteroir Thermal Fins.

1) I believe I read that with enough Exterior Thermal Fins it is possible to reduce the hydrogen boiloff in my cryogenic tanks to 0. Is this true?

2) What is the ideal temperature range for liquid hydrogen Cryogenic tanks? In other words, how many Exterior thermal fins should i add to these tanks?

The current implementation for radiators is flawed. You can get tank temperature low enough but it takes a lot of fins. Something like 12 of them will stop boiloff IIRC.