Improve Fuel Capacity/Volume/Density/Ratio variables

[cmbenne3]

Desired capability or behavior.

Fuel variables and calculations can be improved for usability.

'Capacity' naming is unclear - it should be made more explicit by being changed to volume or mass. Aircraft.Fuel.Capacity_Factor should be replaced as it is not clear what value this should take (16 = 50%, 23 = 70% default, 33 = 100% of the available wing volume is occupied with fuel see table below).

This is the derivation of the FLOPS fuel equations:

These could be updated to use some parameters such as:

1. wing_fuel_volume_fraction, unitless
2. wing_volume, m^3
3. allowing calculation of wing_fuel_volume, m^3
4. fuel density, kg/m^3 specified as absolute rather than a ratio (remove Aircraft.Fuel.Density_Ratio)
5. wing_fuel_mass, kg

to calculate the fuel mass / volume in a way that doesn't require the user to use a parameter with a scale of 0 - 33.

If these changes are made then the fortran_to_aviary conversion function needs to be updated to translate the FWMAX and FULDEN parameters correctly into an absolute fuel density, and a wing_fuel_volume_fraction.

Any changes should be updated in the documentation.

Is your feature request related to a problem? Please describe.

No response

Associated Bug Report

No response

[cmbenne3]

This would address the 'TODO' in line 2558 of variable_meta_data.py:

[cmbenne3]

Fuel Density also seems to swap between being specified as lbm/usgal and lbm/ft**3 within the fuel.py script for GASP based missions. This should be corrected for consistency. picture is extract from prob.model.list_inputs()