More Fun with Fuel 2014 edition.

[kellven]

Well, I was trying to work out the fuel numbers again with 0.35 1/2 parts, but it seems someone last year figured out resource densities only make sense using 5L volume units. That is a huge problem when we figured out back in 2012 Isp only make sense if the volume units are liters, which you might just shrug off, until you realize the engine code doesn't have any concept of fuel consumption anymore, it works backward from an Isp and thrust value. Anyone want to try working the math again, and post what they come up with today? Anyone care to take a stab at what fuel the math resembles now? The forum ate my thread from the last time I went through it, and can't make myself face it again.

There were 2 other unresolved physics issues I was aware of when I gave up in 2012:

-Atmospheric density was never connected to the temperature curve; so local mach velocity is invariant, and molar mass fluctuates wildly instead. Is this still true?

-Unity does not consider units for physics calculations. KSP scales the mass to Megagrams to get around unity mass limits, and this necessitates KN for force as the acceleration is locked to m/s^2. No scaled exponents, so no problem, until you get to big G, where it turns around and rips your head off. Luckily, KSP never actually touches big G, it just uses the shortcut of gravitational parameters handed over precomuted, which keeps the game from exploding, but doesn't make them any less bogus. Is this still true, or even verifiable given all the differing values the game reports? This was a particular pain to test with a plugin, and the numbers just did not add up.

I realize Harv et al are human, but the team has a nasty tendency to use shortcuts with engineering equations that have critical underlying assumptions, forget about those assumptions, and scale something screwball. The problem is they make a plan to "fix it in a future update", then cancel the update so they can add more graphics, and it snowballs when they start coding again having forgotten about the problem.

[K^2]

If you can formulate specific questions, I can go through the code and find out for you. I need to know very specifically where you see the numbers being reported, so I can find the GUI code that handles the particular menu or HUD item and trace it through the routines to whichever function actually computes it. I was able to use this to resolve many questions with drag and I_SP curves for engines.

[Streetwind]

My question being: why make it difficult for you if you could have it easy? Volume units in KSP are arbitrary. Just take them as they are. If they only make sense in 5 liter chunks, then use 5 liter chunks. As I said in another thread, Kerbals might just as well measure liquid volume as "this tank holds 20 Kerbonaut helmets full of liquid". It's no more and no less arbitrary than a liter or a gallon.

Calculate the volume of an existing part. Then calculate the volume of one of your parts. Calculate what fraction of the existing part's volume your part possesses. Assign that fraction of the existing part's fuel capacity to your part, and you're done. Why worry what kind of unit the utterly arbitrary fuel tank numbers represent?

[Seret]

Do you have an objective in mind for your analysis kellven, or is it just curiosity?