# Percent Fuel: HUD value different to Lobby value #4684

Open
opened this issue Oct 3, 2019 · 4 comments

Contributor

### Observed behaviour

When the ship's fuel level is not completely full or completely empty, the percent fuel shown in the lobby is not the same as the percent fuel shown on the HUD. The value displayed on the HUD is always a little bit more.

### Expected behaviour

I think they should agree - unless I am missing something?

### Steps to reproduce

1. Start on Mars (or anywhere)... The percent fuel displayed on the HUD is 100%

2. Go to the lobby, reduce fuel from 100% to 50%

3. Switch to world view and take note of the percent fuel displayed on the HUD (56%)

Shouldn't they be the same? Or is the HUD value something else? The wiki's description of the value is "It shows the % of the tanks"...

My pioneer version (and OS):
Pioneer 20190203 (latest release)
Pioneer master (6fd8f02), approx. 20190915
Windows 10 Enterprise 1809 x64

Contributor

### nozmajner commented Oct 3, 2019 • edited

 Hmm, it seems that the hud is showing it as a percetangle of the total deltav and the other as percetangle of tank capacity? They should definitelly match. But on the other hand, you are not really interested in the physical percetangle during flight, but it's more relevant when you are filling the tank up.
Contributor Author

### craigo- commented Oct 4, 2019 • edited

 OK, I see... They're not actually measuring the same thing. Using the same test scenario: Fuel 100%, delta-v 9790 km/s (100% of maximum delta-v) Fuel 50%, delta-v 5503 km/s (56% of maximum delta-v) I did have an understanding that a certain reduction in fuel resulted in a smaller, nonlinear reduction in delta-v, because overall mass is less... The difference between these two values sort of quantifies that. I'll look into creating an account for the wiki and contribute a description update there. (Edit: done.) Thanks 😄
closed this Oct 4, 2019
Contributor

### nozmajner commented Oct 5, 2019

 Yes, you are correct. The deltaV reduction is not linear to fuel mass, because the overal mass decreases as you burn fuel.
Member

### impaktor commented Oct 5, 2019

 I'm re-opening, as I think we should discuss this more, because it's certainly going to confuse more players, so we need to make sure it's addressed in the best way. Main question is: do we want these numbers to be different? What makes most sense to show when landed (then we care about how much fuel we've loaded / will load) What makes sense in flight? (we want to know delta-V, fuel economy) If they should show different, then at least the mouse over tooltip should reflect that (i.e. need a pull request), + wiki edit, as mentioned.
reopened this Oct 5, 2019