Red Burn Time

[gloog]

Trying to return from Mun, have plenty of fuel as can be seen in image but I have a red burn time????
All fuel tanks are full btw...!

 

https://imgur.com/a/95zCUwI

 

[Gargamel]

Moved to GamePlay Questions. 

[Laie]

The dV thingy in the staging list says you have 108m/s. The maneuver you're trying to do requires more than that. That's why the indicator is red: it thinks you cannot finish the maneuver you have planned.

[Zeiss Ikon]

You have full tanks, but the tankage in that module seemingly only holds about 53-54 units of LFO -- it's enough to run your engine for about a second, and your intended burn is four seconds.

[Streetwind]

Assuming that you have more than just that one Baguette left:

There is a concept in this game called "fuel crossfeed". Basically, there are certain parts across which fuel will not flow, such as decouplers. If you have such a part between the majority of your fuel tanks and the engine, then the engine will not "see" those fuel tanks as valid sources of fuel. It will run out, even though you are still carrying plenty.

Your design looks very compact and heavily featuring surface-attached parts, which is why I cannot easily see from the image whether or not you have a crossfeed problem. You should be able to check this yourself in the VAB. Should you discover a crossfeed problem, worry not, all is not lost: many crossfeed-blocking parts, like decouplers, give you the option to enable crossfeed in the rightclick menu. It's just turned off by default so that engines don't steal from fuel tanks in other stages.