SSTOs - burning off excess Liquid Fuel in space.

[Silverchain]

Is there a simple (and stock) way to get rid of Liquid Fuel in space without relying on a drop tank? I have a plane I want to fly to Duna, where its turbojets will not work, and so I want to get rid of all the 'spare' liquid fuel, the fuel which I do not have enough oxidiser to react against, so as to improve the performance.

I've tried running the turbojets but they flame out, and I've tried running the rocket with only liquid fuel available. I seem to remember that doing so would use to drain fuel, but that isn't happening now. Anyone?

(The plane is in LKO, so it would be trivial to rendezvous with another ship and transfer off the fuel, but more generally I might want to do this at harder to reach locations.)

[thereaverofdarkness]

I know that when I am running rocket engines and the oxidizer runs out, the liquid fuel will continue to drain even though I am getting no thrust. It seems to work any time there is only one side of the fuel needs provided and the engines are otherwise capable of running, and I have thrust above zero. Are you sure your rocket engines are on? Maybe you could try moving a tiny bit of oxidizer to the tanks that the rocket engines can access, to get them started.

[Rhomphaia]

Prior to 0.23 running the jets without intake air, or rockets without oxidizer would work, but it no longer does.

Now your best bet is to get rid of excess fuel in the VAB using tweakables. better still, just use LF/Ox tanks and get rid of the excess oxidizer.

[tavert]

Up to 0.22, if an engine was deprived of one but not all of the resources it required (which you could always do manually by disabling flow of that resource from all sources), it would continue to drain the remaining resource types while throttled up.

The behavior changed in 0.23 along with the introduction of tweakables (or maybe unrelated?). I don't think there's a stock way to do this right now, you either need a mod, or dock with something that has extra space, or rely entirely on setting your tweakables exactly right before you even launch. Would be nice to get in-flight fuel/oxidizer dumping capability back in stock somehow.

[Markus Reese]

Unless you have already set up for it, there is no way that I know of once in space. The way I would do it is to burn up most of it during takeoff phase if I knew I wasn't going to use the jets much anymore. I would burn it down to what I would need to land, then launch or adjust what you take with you on launch so they burn out equally.

However, I think the most efficient way would be a drop tank. Just transfer into a tank that is empty or emptied on launch then jettison else you are editing the persistence file.

[Silverchain]

Thanks everyone.

[ThermalShark]

If your plane has turbojets and is meant to fly in duna, i suppose it's an SSTO and the turbojets are for kerbin take-off. In that case, i suggest launching with you only the LF you will actually use, and/or get rid of the turbojets and their fuel tanks once you are in space or in duna (staging).

[Tank Buddy]

Running jet engines that are oxidizer/ O2 deprived will dump fuel.

[Skorpychan]

Use the VAB to reduce the liquid fuel you're carrying at launch. Test, tweak, and test until you're making it to orbit with less and less of it remaining.