Why no fuel in wings?

[Deadweasel]

With all the mod parts I played with so far, though some of them can cross-feed, why do none of them act as fuel tanks?

B9 Aerospace in particular has these massive things, but even though their real world counterparts do it, these carry no fuel at all.

Is there a reason why? Without that potential capacity, we're forced into dealing with a fuselage design that's larger than it would need to be otherwise, just to bring enough fuel to make the design useful for more than buzzing the KSP tower. Is it not possible for a part to have aerodynamic properties and carry fuel as well? Is there a way to add the capability (and keep the values at least somewhat in-line with the rest of the game parts)?

I know it's not really feasible to balance fuel evenly between tanks and this would likely cause a problem with planes, but I'm willing to bet somebody could come up with a creative means to make it work well on a craft anyway.

EDIT: Umm... So I just went back to the B9 wing, and it looks like fuel is indeed part of its config... I don't know if that's a new thing since the .20 update or what, but I've never been able to actually access fuel from those wings before. Looks like it's time for some more experimentation.

Pardon the interruption. >_>

Edited May 28, 2013 by Deadweasel

[rodion_herrera]

I second the motion. I can still smell the avgas the last time I remember a friend refueling a Cessna by pumping it into the bladders inside the wings...

[_Aramchek_]

Without that potential capacity, we're forced into dealing with a fuselage design that's larger than it would need to be otherwise, just to bring enough fuel to make the design useful for more than buzzing the KSP tower.

Iagree that wings should carry fuel, but the quoted text isn't correct, making sub orbital hops you can go around the planet almost two entire times with just one tank of fuel.

[Deadweasel]

Iagree that wings should carry fuel, but the quoted text isn't correct, making sub orbital hops you can go around the planet almost two entire times with just one tank of fuel.

Yes, if you're only flying with jet engines. Put a rocket on there for a SSTO though, and it's going to be dry in no time flat, unless you have a lot more fuel. Even my favorite SSTO V/STOL (amphibious) ship needs lots of tanks just to get to orbit. Imagine if all the wings people are using for body structure could carry optional fuel as well!

After going back to take a look at my Silverhawk design, which uses those big honking B9 wings, they indeed don't offer any fuel capacity, even though there seems to be an accommodation for it in their config:

// --- standard part parameters ---
mass = 1.95
dragModelType = override
maximum_drag = 0.02
minimum_drag = 0.02
breakingForce = 600
breakingTorque = 600
angularDrag = 2
crashTolerance = 20
maxTemp = 3400
explosionPotential = 0.1
fuelCrossFeed = True
// --- winglet parameters ---
// dragCoeff will override the maximum_drag value
dragCoeff = 0.21
deflectionLiftCoeff = 38.93


[B]{[/B]
[B] name = LiquidFuel[/B]
[B] amount = 400[/B]
[B] maxAmount = 400[/B]
[B]}[/B]

So maybe with a little more tweaking somehow, they might be modded to actually offer up that capacity, but I still don't even get a context menu on them. Might be time to look at comparing some fuel tank configs to see what might be missing...

[Deadweasel]

Seems I'm not the first to have this idea, but... Seriously? Nobody's tried to do anything about this in a year? Is there really something in the game mechanic that prevents a part with lift properties from acting as a fuel tank too? :/

http://forum.kerbalspaceprogram.com/showthread.php/16809-Lifting-bodies-and-fuel-in-wings

[Deadweasel]

Oh.

http://wiki.kerbalspaceprogram.com/wiki/CFG_File_Documentation#Valid_Part_Modules

So it is a limitation of the game itself. Something that uses the "Winglet" module to offer aerodynamic control can't also bring in the "FuelTank" module to be a container for resources.

That's.... lame.

[Fel]

There is no limitation to having fuel in the wing... I have no clue what your rant is about.

"Winglet" is a Part, and all parts have the ability to have "Resources."

Only change is probably around "attachRules = X,X,X,1,X" (Leave the "X" values alone)

Since this is a radial tank, it has to have a fuel-line to attach it together.

Okay, I see... "class FuelTank" seems to... add in explosions and nothing more.

"class Winglet" adds in aerodynamics; but it extends "class Part" which has fully operational resource capabilities.

Edited May 28, 2013 by Fel

[numerobis]

That documentation is old, I'm pretty sure. All parts are module = Part now, and you can add modules to a part (in Unity land, they are Components, IIRC).

[Fel]

That documentation is old, I'm pretty sure. All parts are module = Part now, and you can add modules to a part (in Unity land, they are Components, IIRC).

No that isn't exactly true. Wings ARE type "Winglet" but "Winglets" inherit Part, which controls pretty much everything having to do with resources. (We also have partmodules, but that is a different concept)

I'm not exactly certain why it isn't a part module...

[Deadweasel]

Well, this may not be an apt comparison here, but I went looking at related stock components, compared to the one I'm considering trying to "fix".

The delta wing has this in its config:

// --- general parameters ---
name = deltaWing
module = Winglet
author = C. Jenkins

fuelTankSmall has this:

// --- general parameters ---
name = fuelTankSmall
module = Part
author = Mrbrownce

The B9 HW21 Heavy Wing has this:

// --- general parameters ---
name = B9_Aero_Wing_HW21
module = Winglet
author = bac9

The "module = " lines in particular are what had me believing there's only one type allowed, and that type declaration determines what a part can actually do. So a "part" has general capabilities, but no aerodynamic properties other than drag. A "winglet" has nothing but aerodynamic properties, bringing in deflection drag, lift coefficient etc.

I don't suppose it's possible to declare multiple module types in that line, is it?

[Fel]

PART
{
// --- general parameters ---
name = winglet
module = Winglet
author = HarvesteR

// --- asset parameters ---
mesh = model.mu
scale = 0.1


// --- editor parameters ---
cost = 500
category = Aero
subcategory = 0
title = AV-T1 Winglet
// manufacturer = Kerlington Model Rockets and Paper Products Inc.
// description = 
// attachment rules: stack, srfAttach, allowStack, allowSrfAttach, allowCollision
attachRules = 0,1,0,1,1

// --- node definitions ---
// definition format is Position X, Position Y, Position Z, Up X, Up Y, Up Z
node_attach = 5.10736, -0.589634, 0.0, 1.0, 0.0, 0.0


// --- standard part parameters ---
mass = 0.05
dragModelType = override
maximum_drag = 0.02
minimum_drag = 0.02
angularDrag = 5
crashTolerance = 12
maxTemp = 3400
explosionPotential = 0.1

mirrorRefAxis = 0, 0, -1

// --- winglet parameters ---
// dragCoeff will override the maximum_drag value
dragCoeff = 0.5
deflectionLiftCoeff = 0.3

RESOURCE
{
 name = LiquidFuel
 amount = 360
 maxAmount = 360
}
RESOURCE
{
 name = Oxidizer
 amount = 440
 maxAmount = 440
}
}

This works, I did try this (although with a rocket motor)... IF you attach a fuelline from it to your ship.

"module = " is actually a misnomer, that changes the TYPE the part is, and the only thing "fueltank" does is explode on collision (seriously, that is the ONLY reason to use "module = fueltank")

All "module = X" will have "module = Part" because "Part" is the base class.

*And only if you use a "Typeless" language like Javascript or ObjC will you be able to call 1 "type" multiple "Child Types" [if I am wrong with C# supporting this, I strongly disagree with the notion]... as I said, "module =" is a misnomer, it is the "type" of the part, so just like a String cannot be treated as an int, a "Winglet" cannot be treated as a "FuelTank"... but this is complicated programming talk. The point is, you do not NEED "module = fueltank" for it to work.

Edited May 28, 2013 by Fel

[urablahblah]

One reason Bac9 mentions that he does not add fuel to wings is the stock drag system. The drag is dependent on multiple factors, one of which is weight. If you have fuel in a wing and begin to drain it, the part weight will change which results in a drag reduction. This can lead to all sorts of instabilities in aircraft design.

[RSF77]

Sorry about the necromancy here, but I was just going to try this out myself and I also think that wings should be able to carry fuel in KSP as they do in real life, not to mention that it alleviates many CoM/CoL problems. If the above post is true then couldn't you modify the wing part to have very little drag?

Anyone know if any changes have been made since this or any other recent information about it?

[Javster]

Swept wings should have 100 units of fuel, delta wings 150 (the stock wings)

[Dirt_Merchant]

Guys, if you want to use fuel in the wings, you should go ahead and treat yourself to FAR mod. Once you have FAR mod PM me for help with this. I've spent the last year with fuel bearing wings for all of my in-atmo craft and would be happy to hook you up with what I've come up with. Without FAR this would be folly however, as the stock drag system is not compatible with this idea. Drag != mass IRL, and neither does it in FAR.

Here is my KSP Aircraft Resume`: http://dirt66merchant.imgur.com/all

[rpayne88]

Yes, if you're only flying with jet engines. Put a rocket on there for a SSTO though, and it's going to be dry in no time flat, unless you have a lot more fuel. Even my favorite SSTO V/STOL (amphibious) ship needs lots of tanks just to get to orbit. Imagine if all the wings people are using for body structure could carry optional fuel as well!

After going back to take a look at my Silverhawk design, which uses those big honking B9 wings, they indeed don't offer any fuel capacity, even though there seems to be an accommodation for it in their config:

// --- standard part parameters ---
mass = 1.95
dragModelType = override
maximum_drag = 0.02
minimum_drag = 0.02
breakingForce = 600
breakingTorque = 600
angularDrag = 2
crashTolerance = 20
maxTemp = 3400
explosionPotential = 0.1
fuelCrossFeed = True
// --- winglet parameters ---
// dragCoeff will override the maximum_drag value
dragCoeff = 0.21
deflectionLiftCoeff = 38.93


[B]{[/B]
[B] name = LiquidFuel[/B]
[B] amount = 400[/B]
[B] maxAmount = 400[/B]
[B]}[/B]

So maybe with a little more tweaking somehow, they might be modded to actually offer up that capacity, but I still don't even get a context menu on them. Might be time to look at comparing some fuel tank configs to see what might be missing...

I think you need "Resource" above the first bracket. I've never modded anything, though.

[Deadweasel]

I think you need "Resource" above the first bracket. I've never modded anything, though.

That's very true.

[RSF77]

Guys, if you want to use fuel in the wings, you should go ahead and treat yourself to FAR mod.

I have FAR (lol) too many stock aircraft to switch now, plus I didn't really like it as it made aircraft more difficult to construct and fly than they already are now. Truth be told I have trouble making aircraft that realistically should be able to take off fine, but swerve out of control on the runway because the landing gear isn't precisely straight to a millionth degree... which is incredibly aggravating and should probably be fixed to be more lenient.

[The Destroyer]

When these modules were added, it said in the dev blog: Now you can have wings with fuel!

I'm sure some mods actually have wings with fuel.. hm...

[Captain Sierra]

In reference to an earlier post in this thread (prior to the bump), KSP's drag equation is weird. In short, it approximates cross-sectional area in the drag formula using a sub-formula deriving it from mass. According to KSP physics, as a part get's lighter, the ammount of surface area facing the airstream get's smaller. I know, logic.

Basically, to add the factor of variable mass to wings would likely make KSP very unhappy. I'd even go so far as to warn of the possibility of a kraken attack.

You'll first need to fix the aero model which means running FAR. That aside, it's entirely doable if you can somehow bypass the aero weirdness.

[RSF77]

Well I made an entry in the deltaWing part, simply copied the whole cfg and pasted another below it with the only real change being the added RESOURCE module at the bottom and I also changed the numbers related to drag (thought I did not try it out before I changed the latter), both are in bold.

Everything seemed to work just as it would have in stock KSP, I made a simple small jet and tried it with 100% then 20% fuel and didn't notice any changes. Once the fuel started depleting and the CoM moved back toward the engine it couldn't keep a heading without a reaction wheel (I had already put one on but toggled it off just to see), but this is just the same as it was with such a low mass aircraft with standard parts and fuel tanks. I think it was only about 10 parts or so, just a couple of the modified delta wing tanks, a standard tail, some structural fuselages, a stock mk1 pod, the reaction wheel, basic jet engine, 2 radial intakes, landing gear and a decoupler just because. CoL was ever so slightly behind the CoM, and even with the fuel gone it wasn't that far ahead of it.

Fuel lines from the modified delta wing part to the fuselage were required for it to work though, just as a previous poster said.

The main reason I wanted to do this was because I wanted to keep a more constant CoM in relation to the CoL, which is I guess why they do it in real life aircraft. Some pretty awesome stable aircraft could be made I think if procedural wings could carry a variable amount of fuel based on their size, like it does with lift and whatnot.

PART
{

// --- general parameters ---
name = deltaWingtank
module = Winglet
author = C. Jenkins

// --- asset parameters ---
mesh = c7deltawing.DAE
scale = 0.1

// --- editor parameters ---
TechRequired = supersonicFlight
entryCost = 5400
cost = 500
category = Aero
subcategory = 0
title = Delta Wing Fuel Tank
manufacturer = C7 Aerospace division
description = Standard Delta configuration wings. These wings provide high lift and a stable center of gravity for your everyday lifting needs.

// attachment rules: stack, srfAttach, allowStack, allowSrfAttach, allowCollision
attachRules = 0,1,0,1,1

// --- node definitions ---
// definition format is Position X, Position Y, Position Z, Up X, Up Y, Up Z
node_attach = 0.0, 0.0, 0.0, 1.0, 0.0, 0.0


// --- standard part parameters ---
mass = 0.07
dragModelType = override
[B]maximum_drag = 0.0001
minimum_drag = 0.0001
angularDrag = 0.001[/B]
crashTolerance = 15
maxTemp = 3400
explosionPotential = 0.1
fuelCrossFeed = True
// --- winglet parameters ---
// dragCoeff will override the maximum_drag value
[B]dragCoeff = 0.0001[/B]
deflectionLiftCoeff = 1.9

[B]RESOURCE
{
 name = LiquidFuel
 amount = 100
 maxAmount = 100
}[/B]

}

Edited March 7, 2014 by RSF77

[CountLagula]

Sorry for the AGAIN necromancy, I just was playing around with the numbers with FAR installed, and it looks like the optimal amount of liquid fuel for one delta wing is around 220. Most designs will still take off quite easily this way, and depleting the fuel has no real effect on the drag with FAR installed, so nothing else needs to be changed. I sent a message to one of the devs, and am hoping for a workaround that lets us get rid of he fuel line, and I will update if I hear back.

[lammatt]

you can just add the few lines in the cfg files.

[JonBar]

Procedural wings with fuel(optional) would be amazing!

[CountLagula]

you can just add the few lines in the cfg files.

I have added the resource lines, but I'm trying to figure out a way to make the engine pull fuel from the wings without a fuel line attached.