Oxidizer only tanks?

[Winderfo]

Sometimes, specially with the "Mainsail" engine, I run out of oxidizer when there is a lot of liquid fuel remaining, so it is a waste of resources and increases weight. I couldn't find an oxidizer-only tank. Is it planned in development or something?

[Tex_NL]

Engines only use fuel/oxidizer in two set ratios. Jet engines and nukes only use liquid fuel. All other (non mono-prop) engines use fuel:oxidizer 9:11. e.g 9 units of fuel to 11 units of oxidizer.
Fuel tanks also come in two ratios: Liquid fuel only and fuel:oxidizer 9:11. If you run out of oxidizer that can mean only two things: Either you have removed oxidizer from a tank. Or you have added liquid-fuel-only tanks to your craft.

If you only use regular rocket engines you should only use the 9:11 mixed tanks.

Edited December 19, 2015 by Tex_NL

[Winderfo]

3 minutes ago, Tex_NL said:

Engines only use fuel/oxidizer in two set ratios. Jet engines and nukes only use liquid fuel. All other (non mono-prop) engines use fuel:oxidizer 9:11. e.g 9 units of fuel to 11 units of oxidizer.
Fuel tanks also come in two ratios: Liquid fuel only and fuel:oxidizer 9:11. If you run out of oxidizer that can mean only two things: Either you have removed oxidizer from a tank. Or you have added liquid-fuel-only tanks to your craft.

If you only use regular rocket engines you should only use the 9:11 mixed tanks.

I usually set  two Rockomax Jumbo-64 fuel tanks with the Mainsail engines. Without adding or removing anything normally I have aprox. 1000 fuel left when it runs out of oxidizer.

[Tex_NL]

A Rockomax Jumbo-64 contains fuel in the exact ratio a mainsail engine uses it: 2880:3520 = 9:11.

There must be something going on in your game that adds oxidizer, removes liquid fuel or changes contents/consumption. In a stock unmodded and bug free game (as far as KSP can ever be bug free) what you're saying is not possible.

[Winderfo]

Well, I don't have heavy mods I think, just the mechjeb one and the near future propulsion. I don't know if this may be the cause but I haven't touched anything else.

[Red Iron Crown]

Can you show a pic of your rocket on the pad with the resource panel open, Winderfo? Tex_NL is correct, unless you've used some LF-only tanks or tweaked out some oxidizer then the LF and O should run out at the same time in the 2xOrange tank + Mainsail arrangement.

[Winderfo]

3 minutes ago, Red Iron Crown said:

Can you show a pic of your rocket on the pad with the resource panel open, Winderfo? Tex_NL is correct, unless you've used some LF-only tanks or tweaked out some oxidizer then the LF and O should run out at the same time in the 2xOrange tank + Mainsail arrangement.

Sure, here it is https://www.dropbox.com/s/l5ekl07zf8ptyrb/Captura%20de%20pantalla%202015-12-19%2014.39.06.png?dl=0 

[Red Iron Crown]

10 minutes ago, Winderfo said:

Sure, here it is https://www.dropbox.com/s/l5ekl07zf8ptyrb/Captura%20de%20pantalla%202015-12-19%2014.39.06.png?dl=0 

Two things I think might be happening:

1. Running the nuclear engines and Mainsails at the same time, and the nukes are drawing liquid fuel from the side boosters.
2. The Mainsails are drawing liquid fuel from the nuclear stage in the center.

Both of which are a bit odd since I don't see any fuel lines. Maybe try right clicking the radial decouplers and ensuring that fuel crossfeed is off?

[Winderfo]

3 minutes ago, Red Iron Crown said:

Two things I think might be happening:

1. Running the nuclear engines and Mainsails at the same time, and the nukes are drawing liquid fuel from the side boosters.
2. The Mainsails are drawing liquid fuel from the nuclear stage in the center.

Both of which are a bit odd since I don't see any fuel lines. Maybe try right clicking the radial decouplers and ensuring that fuel crossfeed is off?

Crossfeed in all decouplers is deactivated so that shouldn't be the issue if they are not bugged.

[Winderfo]

Here it is another image. About 2000 liquid fuel left while oxizider is almost finished https://www.dropbox.com/s/24f0843409wj3nh/Captura%20de%20pantalla%202015-12-19%2015.01.02.png?dl=0

[Red Iron Crown]

24 minutes ago, Winderfo said:

Here it is another image. About 2000 liquid fuel left while oxizider is almost finished https://www.dropbox.com/s/24f0843409wj3nh/Captura%20de%20pantalla%202015-12-19%2015.01.02.png?dl=0

That's expected, the liquid fuel is in the tanks in the center for the nukes. The resource panel is showing totals, not just for the stage. Try hovering your mouse over the little square to the left of "Liquid Fuel" in the resource panel, you'll see where the fuel is.  

6x400 unit tanks = 2400 units of LF, leaving 103 units in the side tanks to go with the 125 remaining oxidizer.

[Winderfo]

7 minutes ago, Red Iron Crown said:

That's expected, the liquid fuel is in the tanks in the center for the nukes. The resource panel is showing totals, not just for the stage. Try hovering your mouse over the little square to the left of "Liquid Fuel" in the resource panel, you'll see where the fuel is.  

6x400 unit tanks = 2400 units of LF, leaving 103 units in the side tanks to go with the 125 remaining oxidizer.

Oh my. I can't believe I made that mistake. Well after all everything was about the human factor :/

[Just Jim]

Perhaps this is a little off topic, but since it looks like the OP got an answer...

I would love to see oxidizer only tanks.  There have been a few times building SSTO's that I thought having a small oxy only tank, similar to the two radial mono-fuel tanks, could be very, very handy, instead of trying to balance rocket liq-oxy tanks and jet fuel only tanks to get the right balance.

[Tex_NL]

1 hour ago, Red Iron Crown said:

That's expected, the liquid fuel is in the tanks in the center for the nukes. The resource panel is showing totals, not just for the stage. Try hovering your mouse over the little square to the left of "Liquid Fuel" in the resource panel, you'll see where the fuel is.  

6x400 unit tanks = 2400 units of LF, leaving 103 units in the side tanks to go with the 125 remaining oxidizer.

See. I just knew I was right all along.

49 minutes ago, Just Jim said:

Perhaps this is a little off topic, but since it looks like the OP got an answer...

I would love to see oxidizer only tanks.  There have been a few times building SSTO's that I thought having a small oxy only tank, similar to the two radial mono-fuel tanks, could be very, very handy, instead of trying to balance rocket liq-oxy tanks and jet fuel only tanks to get the right balance.

KSPX used to have both tiny LF and Ox tanks similar in size as the cylindrified monopropellant tank.
Another option, which I use myself, is FSFuelswitch. A very useful feature to cycle through LF/Ox, LF  and Ox on all tanks.

[Red Iron Crown]

7 minutes ago, Tex_NL said:

KSPX used to have both tiny LF and Ox tanks similar in size as the cylindrified monopropellant tank.
Another option, which I use myself, is FSFuelswitch. A very useful feature to cycle through LF/Ox, LF  and Ox on all tanks.

I've been messing around with Modular Fuel Tanks for this, and I have to say it is quite slick. Mix and match tank contents (so a single tank could hold LF,O and MP simultaneously). Great for reducing part count.