Tweakable fuel tanks

[Killerdude8]

I can't possibly fathom the reason why ANYONE could possibly be against what OP wants at ALL.

All he wants to do is to be able to send up a full tank of one type of fuel, IE; Replace the space usually taken up by Liquid fuel with Oxidizer instead.

That would so incredibly useful for Spaceplanes, You people have no idea.

[CaptRobau]

I wonder how they're planning to do single fuel nuclear rockets with the way they implemented it now.

[Murph]

The way I see this playing out for spaceplanes, without any further changes to tweakables, is simply to use it to reduce the starting fuel in your jetfuel tanks, and keep the rocket tanks for the rockets. I really don't see that there's a major game-breaking problem by not being able to randomly move the internal bulkheads inside standard tanks (which is essentially what's being asked for, and is unlikely to be done in the real world).

We now get to choose the precise total fuel load in the VAB, save that as part of our craft file. If we need extra fuel-only space, we have that via the jet fuel tanks. The stock game has very little requirement for extra oxidiser-only tank space since we have a generous selection of perfect-ratio fuel+oxidiser tank sizes. What we may well need, is half and double size jet fuel tanks, but that's a separate issue from tweakable fuel load.

Creating some new parts which are oxidiser-only or different sized fuel-only tanks is pretty easy, really. At the simplest level, it's just a copy of an existing part.cfg with some minor changes. For bonus points, it additionally does some minor texture editing to help you visually identify the part.

So, to sum up, my opinion is that fuel tweakables are just fine as-is, but there may be some additional stock tank types/sizes which should be added.

[Brotoro]

This is certainly a disappointment, and not what I was hoping for. I was hoping that I would be able to set the FL-T400 tank (for example) in the VAB or SPH to hold 400 units of whatever I wanted. I don't see why this is physically unreasonable. When building a tank on a real life spaceship, we don't leave room in the tank for types of propellant we don't need. THAT would be physically unrealistic.

[Eric S]

I wonder how they're planning to do single fuel nuclear rockets with the way they implemented it now.

True, that was waiting on tweakables so that they didn't have to have multiple types of every fuel tank. This is one of the reasons I think they're not done with tweakables. Changing the atomic rocket engine to only use liquid fuel and not letting us use fuel tanks that pack in more liquid fuel with the same dry mass would kill the usefulness of them.

[Superfluous J]

How often do real space programs carry dead weight just to reuse common parts?

Other than the Space Shuttle?

[geb]

I was hoping to be able to fill 2.5m tanks with xenon. I guess we won't be getting that in 0.23

Ok, granted it would give me a craft with about the same thrust-to-weight ratio as a flashlight, but it still would have been cool.

[Albert VDS]

To me the whole idea seems to be based on the inside of the fuel tank.

Just look at the cutaway image of the Saturn V bellow, each stage has 2 fuel containers.

Of course these containers are not changeable, unless you rebuild the while tank.

Each tank in KSP works on the same principle. They are prebuilt tanks which can't be structurally changed.

Just like the landing wheel tires can't be changed in size.

At least that is what I think Squad's reasoning is behind this.

[Garek]

Of course these containers are not changeable, unless you rebuild the while tank.

Each tank in KSP works on the same principle. They are prebuilt tanks which can't be structurally changed.

But it shouldn't it be possible to switch which kind of fuel goes in which tank? So you couldn't lower one slider to increase the other, but you could assign which slider has which fuel.

Just like the landing wheel tires can't be changed in size.

I don't care about the tires themselves, but I really want to be able to edit the ground clearance.

[lajoswinkler]

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.

You can't stuff oxidizers in the containers for reducers (kerosene, LH2, etc.). It's a fact and it destroys all the whining on this thread.

[NovaSilisko]

Kind of strange that there's actually an argument about this, to me... You're building the vehicle, you're fitting tanks and bolting stuff together, routing wires through stuff, etc. It's just not really visually shown ingame. As such it stands to reason that the kerbals are also capable of altering the interior dimensions of a fuel tank, to allow it to hold just oxidizer or just fuel. That's what I was expecting of tweakables, not some "oh we just leave that part of the tank empty" deal...

[KerbMav]

It is the first go at tweakables, either it will be in another patch or we will have to use mods/different parts for what we want to build.

But actually it opens up a design possibility too: start a spaceplane with just enough fuel to reach high altitude and a bit oxidizer to reach orbit. Then fill it all up at a spacestation and off to other places you go. So, no need to carry up all the unnecessary fuel to orbit in tanks large enough for the voyage or squeeze in an extra tank for atmospheric flight only.

[FlamedSteak]

I can see both side of the argument, that being said, it makes more sense to me to have additional tank parts containing only oxidizer or fuel.

[Ringkeeper]

Kind of strange that there's actually an argument about this, to me... You're building the vehicle, you're fitting tanks and bolting stuff together, routing wires through stuff, etc. It's just not really visually shown ingame. As such it stands to reason that the kerbals are also capable of altering the interior dimensions of a fuel tank, to allow it to hold just oxidizer or just fuel. That's what I was expecting of tweakables, not some "oh we just leave that part of the tank empty" deal...

Well, then why the mighty builders dont use just a "fuel only" or "oxygen only" tank ? But try to use a tank, that is build for 2 different fuel types to use only one?

[KerbMav]

Well, then why the mighty builders dont use just a "fuel only" or "oxygen only" tank ? But try to use a tank, that is build for 2 different fuel types to use only one?

Part count and stability - although it would balance the shift of CoM.

[Mr. Scruffy]

So how about this: Players could make copies of fuel tank types and adjust their storage capacities as being suggested in this thread (= very freely). Each new copy costs a certain amount of credits (for internal adjustement & prototyping).

UI-wise: Right-click on part (tank) in VAB. Pick ´copy´ (or ´new prototype´) from the popup-menu. A window comes up, in which you set contents by freely distributing the total capacity among all kinds of fuel you desire. Hit the ´Accept & Pay´ button if you are pleased with your new fuel-tank, hit ´cancel´ if you cant make up your mind just yet. You pay for the prototype instantly, before launch or even implementation of the new tank into the VABs menus.

BTW: I am also for an 1:1 consumption ratio.

[vexx32]

I think that's far too much for something that could conceivably be done with some modifications to the present system.

If you change the sliders to work in percentages, you can easily determine ratios of fuels... I think setting levels should be one slider (increasing/decreasing starting fuel level of both oxidiser and fuel in the set ratio), and setting ratio of fuel:oxidiser should be the other slider. The same number of sliders, but with that, it becomes a piece of cake to fill/empty and fill the tank with different amounts of fuel and oxidiser.

[allmappedout]

You can't stuff oxidizers in the containers for reducers (kerosene, LH2, etc.). It's a fact and it destroys all the whining on this thread.

Why not? If I want to mix Hypergolic propellants together in a tank prior to take off, I should be able to blow myself up

[Paul Kingtiger]

Ultimately it would be nice to have fuel tanks, with sliders or all fuel types, Oxidizer, Liquid, monoprop and xenon. Then you could cut down on your parts list to just different sized tanks and allow people to build the tank they need.

To do so you'd have to decided what one unit of fuel represents (weight or volume) and add in the ratio for each type (are fuels bulky for their weight or compact).

Is this too procedural? Maybe for some people, but I'm sure we'll see it as a mod either way.

[GROOV3ST3R]

So you can't stuff fuel into oxidizer tanks - but when building, you adjust the proportions of those tanks. Isn't it natural that you would make one of them purposefully smaller to accommodate less oxidizer and more liquid fuel for an SSTO craft? When it's done, it's done. But before that, it should allow you to select what portion of the entire thing will be devoted to which kind of propellant.

Maybe it could be done in a ''procedural'' kind of way - you would have a slider which would adjust max values for each propellant in your tank and THEN you can choose how much of these tanks you want to fill up with fuel. I see advantages that could be obtained by starting half-empty or by having balancing tanks for crafts with offset centre of mass. But while building, we should be able to select how big the Liquid Fuel part of the tank is in relation to the Oxidizer part. Just my 2cents, I'm sure it's been said before ^^

[Danish_Savage]

I have the solution guys:D

In the ''normal'' fuel-tanks you have two internal tanks, because that is how it is in reality.

However you can chose from a list what goes in these tanks.

Like I could say both where oxygen.

Then for each tank there is a slider too.

[PakledHostage]

Kind of strange that there's actually an argument about this, to me... You're building the vehicle, you're fitting tanks and bolting stuff together, routing wires through stuff, etc. It's just not really visually shown ingame. As such it stands to reason that the kerbals are also capable of altering the interior dimensions of a fuel tank, to allow it to hold just oxidizer or just fuel.

I don't want to be pedantic but aren't most of our rockets assembled from parts that were found laying by the side of the road?

[Dweller_Benthos]

I don't see a problem with having a tank that can contain any type of fuel in any ratio the player wants. If you're building the rocket/plane, aren't you also deciding what is needed for the mission? You don't put lander legs on it if it's never meant to land.

Should be as simple as a set of sliders, one for each type of fuel. The default for that tank is set when you place the tank in the VAB/SPH. You should then be able to move fuel around any way you want, if you move one slider all the way to the capacity of the tank, the rest either go down automatically or become unavailable. To make room for more fuel of one type, you have to reduce the other types.

Once you get to the launchpad though, that should no longer be possible, you don't go swapping fuel around at the last minute. Also, once economy and funding becomes part of the game, creating a custom tank will cost more than using the one "off the shelf", and cost will be determined by how much you customize it. Just dumping the oxidizer and leaving the fuel will actually cost a bit less, but doing a completely custom tank with more types of fuel would cost a bit more.

Once in flight, that tank is locked to those types of fuel, so even empty, if a tank never carried oxidizer, you can't then fill it from another tank that does have oxidizer, it wasn't made for it.

[SunJumper]

I'd say that the uses for independently scaling resources with respect to the total capacity is less useful due to the fact that the rocket engines are engineered to have a standard fuel consumption ratio. Here's the scenarios I can imagine:

1) The fuel levels of both resources are at a 45:55 ratio and the tank is full. The stock scenario we are all used to.

2) Same as above, but the tank is partially full. You have now tuned the craft to have a TWR of 1.05/1.5/2.0/whatever. Or, you have tund it to fly around the world, carrying less mass and hence giving you an edge over 0.22 entries.

3) The ratio is the same but the tank is empty. You launch these into orbit with hab space or whatever, and refuel with special refuellers. Or you could have those tanks be full of fuel and burn that fuel for orbit, saving a little more mass. This may be useful for mission simplicity, however.

4) The fuel is whatever and the ratio is different. All engines have the same ratios. You now waste one reactant, depending on mission profile.

5) Same as above, but some engines have different ratios. Rather than manually setting the ratio with the resource sliders, a discrete ratio slider is used, to prevent wastage.

6) Spaceplane time. The rocket fuel tanks have the oxidizer removed, and in terms of mass ratio, the tank still outperforms the stock jet fuel tanks. Oxidizer is not wasted. Perhaps the oxidizer is replaced with more liquid fuel, if the player can do that.

I thought for a while and couldn't think of any more scenarios. Maybe with nuclear reactors, they may be launched without nuclear material for 'safety' in the event of a launch failure (set Testium to zero). Who knows.

[Eric S]

Well, then why the mighty builders dont use just a "fuel only" or "oxygen only" tank ? But try to use a tank, that is build for 2 different fuel types to use only one?

The devs have specifically stated that they wanted to avoid having to have separate parts for all the different variations on fuel combinations, and that tweakables were how they were going to avoid this. So far, tweakables aren't doing a good job of replacing the need for multiple variants of the same parts, which is why I suspect that they're not done with tweakables.

Other than the Space Shuttle?

If you're talking the philosophy of it, then yes, the space shuttle was excessive for what it was used for most of the time.