Tweakable fuel tanks

[LethalDose]

I know it's early in KerbalKon to start complaining, but, oh well.

I REALLY think they dropped the ball on the tweakable fuel tanks. For anyone that hasn't watched the videos, here's how a tweakable tank works, with an FL-T 800 as an example:

The FL-T 800 may hold up to 360 fuel and up to 440 oxidizer.

You may tweak the amount of fuel in the tank at launch to anywhere between 0 and 360 using a slider.

You may tweak the amount of oxidizer in the tank at launch to anywhere between 0 and 440 using a slider.

But the amount of fuel you select has no effect on the amount of oxidizer you can take, and vice-versa. So you if you want to take 400 fuel and 400 oxidizer, you have to put a totally separate tank on the ship for that extra 40 units of fuel...

WHY!?!?!

Disappointing guys.

[Dvarx]

you sure it's like that? :/ I think it'll be fixed by mod then..

[Eric S]

I noticed that too. I'm assuming that that will happen later, since it's the main reason I want tweakables.

[LethalDose]

It's what was demonstrated before Squad showed up. It's in the RAPIER demo video. The guy (Yarg?) showed how to set fuel and oxidizer maxes separately, the slider's didn't exceed the current max values.

Also, in the RAPIER demo video, he pointed out that you could reduce the volume of oxidizer and fuel, but the max values were each were still set.

It seems pretty clear that the max tank volumes for tanks are locked per reactant.

[Retread]

This seems pretty rooted in reality - inside each fuel tank are separate, pressurized tanks for fuel and oxidizer. When you tweak the fuel tanks, you are changing to what percentage each one of those is filled - not the capacity of the tanks.

Edited December 12, 2013 by Retread
grammar

[regex]

I can think of two reasons: Ease of coding and incentive to use different parts. Whether those are good reasons or not is debatable.

E:

This seems pretty rooted in reality - inside each fuel tank are separate, pressurized tanks for fuel and oxidizer. When you tweak the fuel tanks, you are changing how to what percentage each one of those is filled - not the capacity of the tanks.

Is another good reason.

[LethalDose]

I can think of two reasons: Ease of coding and incentive to use different parts. Whether those are good reasons or not is debatable.

E:

Is another good reason.

You're suddenly concerned about coding difficulty? ... wow...

Also odd seeing you invoking "incentives to use different parts" after you flipped out about designers telling you how to play.

As far as different separate tanks, yes, you're changing it. At launch, you "tweak" the part and partition it differently. I'm not talking about changing max values in flight, I'm talking about changing them during craft design. And the coding would be easy, even for you.

But I guess giving players more control just frightens some people.

[THE META]

i'm sorry, but tweakables were always meant to be like this. if you could tweak the max fuel of tanks in the VAB, then every one would just be setting the fuel tanks to ridiculously high amounts of fuel capacity and people would just say that it wasn't cheating since it's a in game feature.

[_Aramchek_]

The overall volume of liquid wouldn't be changed, for instance instead of 400 fuel 400 ox, you could have 600 ox 200 fuel.

Or whatever combination up to 800 units of liquid volume.

[Karriz]

i'm sorry, but tweakables were always meant to be like this. if you could tweak the max fuel of tanks in the VAB, then every one would just be setting the fuel tanks to ridiculously high amounts of fuel capacity and people would just say that it wasn't cheating since it's a in game feature.

That's not what people want. Having the ability to replace the oxidizer space with fuel would be cool. Of course you couldn't go above that.

[regex]

As far as coding difficulty, I suppose it comes down more to GUI design and expected behavior. Adding two sliders is pretty easy, but when you are able to affect the values of one by sliding the other things get a bit hairy, especially when you deal with different densities (and maximums at that point). Then you need a reset button, how to allow reset from sliders, increment steps, what is intuitive, etc... It's not actually that much more code for sure, but making it playable takes some thought. Refinement may come with time.

There is the matter of a nod to realism that Retread brought up, I think that's a much more compelling argument.

[LethalDose]

The overall volume of liquid wouldn't be changed, for instance instead of 400 fuel 400 ox, you could have 600 ox 200 fuel.

Or whatever combination up to 800 units of liquid volume.

This. It's the volume total that matters.

[Firov]

It really should be like the modular fuel tanks mod, where you can have any combination of fuel up to the maximum volume for that tank. For example, lets say you have a fuel tank with 200 units of fuel, then you might have 175 fuel, 75 oxidizer, and 50 units of monopropellant.

The only thing that should be limited is the overall volume of the tank, beyond that, we should be free to do as we please.

[superm18]

Well the oxidizer and the fuel surely can't be mixed. Not before ignition anyways

[PakledHostage]

As far as different separate tanks, yes, you're changing it. At launch, you "tweak" the part and partition it differently. I'm not talking about changing max values in flight, I'm talking about changing them during craft design.

But I think where people here mention that it is rooted in reality, they are talking about the capacities of the physical partitions within the tank assembly being fixed. You may be able to customize the fuel load for a rocket that is on the pad by loading more or less fuel/oxidizer, but you can't realistically expect to be able to change the size of the partitions within the tank assembly on the pad.

[Dizzle]

This. It's the volume total that matters.

Agreed. Would help a lot with SSTO building. No more lugging around tons of useless liquid fuel.

[THE META]

well if that's what you want, then I guess that's a lot better, and probably a hell of a lot more useful. maybe in .24, we will get more advanced tweakables.

[LethalDose]

As far as coding difficulty, I suppose it comes down more to GUI design and expected behavior. Adding two sliders is pretty easy, but when you are able to affect the values of one by sliding the other things get a bit hairy, especially when you deal with different densities (and maximums at that point). Then you need a reset button, how to allow reset from sliders, increment steps, what is intuitive, etc... It's not actually that much more code for sure, but making it playable takes some thought. Refinement may come with time.

There is the matter of a nod to realism that Retread brought up, I think that's a much more compelling argument.

I don't know why I even bothered responding to you. I directly addressed the 'nod to realism' in what I wrote, but you keep on ignoring it.

[Urban_K]

This seems pretty rooted in reality -

And just like has happened in reality we should of course have the option of filling one with too much LOX.

[regex]

I directly addressed the 'nod to realism' in what I wrote

Yeah, I don't agree with that, certainly not on the pad and during design it reduces the incentive to use differing parts. I'm sure we'll see what you want in a mod though, and maybe later in the iterative process. Why not make a suggestion?

[LethalDose]

well if that's what you want, then I guess that's a lot better, and probably a hell of a lot more useful. maybe in .24, we will get more advanced tweakables.

Yeah, I was never asking to be able to set the fuel capacity to any value. That'd be nuts.

[Retread]

Another way to approach this would be to allow separate tanks for fuel and oxidizer and release them in pairs sized in appropriate ratios. Want to build a standard rocket? Instead of the current orange tank, use the orange fuel tank plus the orange oxidizer tank. Building a spaceplane? Add more fuel tanks than oxidizer to cover the air-breathing portion of the flight. Have a refueling station in orbit that only needs fuel, not oxidizer? Make your payload a fuel-only tank. Both types of tanks could tweakable, and only require one slider each.

[El wonso]

I am really disappointed. I hope Squad will fix that before 0.24, I don't want to wait for months for such thing.

[Palleas]

Then ignoring the feature and play as before, enjoying optimisations, is your option.

[vetrox]

Its not just about balancing fuel.

Tweakables (note the name, you can tweak things) are quite usefull in other areas that wernt in the rapier vid such as changing how wings work. Also note the ability to tweak the srb thrust. This will totally change how I use srb's

But the amount of fuel you select has no effect on the amount of oxidizer you can take, and vice-versa. So you if you want to take 400 fuel and 400 oxidizer, you have to put a totally separate tank on the ship for that extra 40 units of fuel...

Why would u need 400 units of each? you will run out of oxidiser too soon