Flight times versus fuel levels

I’m setting a flight to another system and noticed some odd behavior.
I set the ship to take it’s time to get there, slowest speed both STL and FTL.

It says 1 day 23 hours. However when I remove SF from the ship’s tank, in this case 1k SF, it takes a little less fuel for the trip which makes sense, but it also slows it down to an absurd 7 days 7 hours despite using very similar fuel amounts.

I would expect the time needed to be less since less fuel means lower mass and better acceleration but instead we get the opposite to an extreme. All this added time is from departing the starting system. It goes from using 10 units of fuel to only 1 for no reason.

Sometimes 12 SF has an exponential impact on flight time as you need enough velocity to escape Montem’s gravity well.

The departure from Montem using 10 SF is orders of magnitude faster than trying to depart Montem with 1 SF (displayed in the second picture). Using BLU in a new buffer, players can determine what kind a fuel expenditure they should expect from point A to point B.

The Fuel Usage slider functions depending on how much gas is in the fuel tank. MIN fuel with 200 SF is way different than MIN with 1200 SF in the tank.

You should subtract the take-off and landing fuel, because those are just fixed numbers regardless of total burn. Once you do that, you should see that you’re burning about 7x as much for the actual flying (or at least a much more reasonable ratio).

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The fuel sliders are percentages of the fuel in the tank. So although the % of fuel used is the same the amount used changes with your fill level.
The numbers in the top right of the flight plan are the best guide as to how much fuel will be used for the trip.

I think the point is mainly: Pengo put the sliders to MIN in both cases.
Why does the MIN fuel required to do the trip shift so much even though the mass of the ship only changed 27t (out of 1251t)?

It’s not about the mass. It’s about available fuel. MIN might be 1% of total tank after landing/lifoff fuel is deducted(it’s constant). We can see it burned 10 STL getting away from Moria in first case and 1 STL in second case. 10% of thrust will lead to much longer flight times.

Well, then that is either a bug or a shortcoming of the system, because I don’t see how the minimum amount of fuel to get somewhere should change depending on how much fuel you’re carrying

There’s no minimum amount of fuel required to get anywhere. A millisecond thrust pulse is enough to get you anywhere since there’s no drag in space. It will simply take a very long time.

I agree though that the slider is misleading, but it would be impossible to set meaningful values on that slider. The problem might be the percentage they use at MIN. If it’s 1%, then that’s where the issue comes from. It could be 1 instead of 1% and MAX could still be 100%. Although that’s somewhat minor because you rarely want to burn the minimal amount of STL fuel since it takes forever.

That’s just a completely wrong statement. You really gonna need to look into orbital mechanics, gravity potentials and gravitational drag.
Here’s a youtube video explaining a bit of it: The Most Confusing Things About Spacecraft Orbits - YouTube

I know that, but considering the game sometimes generates a path that is the opposite of planet orbits makes me believe it doesn’t really do orbital mechanics. As in, it starts the ship at 0 velocity and reduces to 0 at destination with potentially some planetary movement taken into account. Otherwise you wouldn’t be able to escape Moria with 1 STL fuel.

You’re forgetting that burning to escape a gravity well and orbit are one thing, but accelerating a decellerating for a long journey are another. You need X fuel to get X mass out of a gravity well, no matter what, but you can reduce fuel for the longer journey by just… not accelerating at all, and simply taking years to get somewhere you know? So while minimum fuel as a set number applies some bits of the journey, other bits will be proportionally inverse to the time taken, so going for ‘minimal’ fuel spent can exponentially increase time taken.