GASP based mass subsystem for BWB

[xjjiang]

Summary

• For design load, variable Aircraft.Wing.LOADING is replaced by Mission.Design.GROSS_MASS / Aircraft.Wing.EXPOSED_WING_AREA. As a result, BWBLoadSpeeds and BWBLoadFactors replace LoadSpeeds and LoadFactors. A new group BWBDesignLoadGroup is created to include these two new components.

• Equip And Useful Load

  • EquipAndUsefulLoadMass is a big components that includes the computations of 19 items. Ideally, each of them should be done in its own component and one group has them all. This is a long time goal. For now, it is separated to two components EquipMassPartial and UsefulLoadMass and air conditioning and furnishing masses are singled out because they need to be modified for BWB.
  • A new variable Aircraft.Electrical.SYSTEM_MASS_PER_PASSENGER is added which corresponds to CW(15) in GASP. Its value is different for conventional aircraft and BWB.
  • Two new classes BWBACMass and BWBFurnishingMass are added to equipment_and_useful_load.py. Unit tests for BWB model are created. Our outputs match with GASP run result.
  • Note: GASP Fortran code has new updates that are not included in Aviary. We will update Aviary for furnishing mass but other masses need to be checked.
  • Note: EquipAndUsefulLoadMass has implementation errors for the computations of Aircraft.APU.MASS, Aircraft.Avionics.MASS, Aircraft.AntiIcing.MASS, Aircraft.Furnishings.MASS, and Aircraft.Design.EMERGENCY_EQUIPMENT_MASS. As a result, Aviary always uses user provided masses (not empirical formulas). We should use Aviary's feature of overriding for thf overridinose variables. All the outputs of 9 unit tests in test_mass_summation.py` are updated.

• Wing Mass Model

  • For wing mass, variable Aircraft.Wing.SPAN has to deduct cabin width (i.e. Aircraft.Fuselage.AVG_DIAMETER). As a result, WingMassSolve component is replaced by BWBWingMassSolve component. BWBWingMassGroup is created to pair BWBWingMassSolve and WingMassTotal.
  • In geometry/gasp_based/wing.py, Aircraft.Fuel.WING_VOLUME_GEOMETRIC_MAX is moved out of WingParameters class. In stead, a class WingVolume is created to compute Aircraft.Fuel.WING_VOLUME_GEOMETRIC_MAX. For BWB, another class BWBWingVolume is created for the same purpose. The algorithm is quite different for BWB.
  • In geometry/gasp_based/wing.py, WingFold class is split to two: WingFoldArea and WingFoldVolume. The first computes Aircraft.Wing.FOLDING_AREA and the second computes Aircraft.Fuel.WING_VOLUME_GEOMETRIC_MAX. For BWB, another class BWBWingFoldVolume is created to do the same job. Note that for BWB, BWBWingFoldVolume uses the result in BWBWingVolume.
  • A BWBWingGroup is created to put all these pieces together.
  • Unit tests are added in geometry/gasp_based/test/test_wing.py to make sure that the Aviary result is the same as GASP model.

• Fuel Model

  • FuelMassGroup groups all fuel related components. In case of BWB, BWBFuselageMass is in place of FuselageMass. This group has a nonlinear solver. In order for it to converge, one must provide good initial guesses for the inputs. Otherwise, it may claim that convergence is reached but gives rise to a strange solution.
  • The computation in BodyTankCalculations of fuel.py can not be matched in GASP Fortran code. It is not very clear if it is correct. It is possible that extra_fuel_volume becomes negative. I added code to make sure that it is always positive.
  • For fuselage mass, the empirical weight equation is quite different. It is computed in FuselageAndStructMass component. This component has two parts: fuselage mass and structural mass. In order to reuse the code for structural mass, this component is split into two components: FuselageMass and StructMass. For BWB, FuselageMass is replaced by BWBFuselageMass.
  • Note: The historic name of Mission.Design.FUEL_MASS_REQUIRED is INGASP.WFAREQ, but WFAREQ includes fuel margin in GASP while Mission.Design.FUEL_MASS_REQUIRED doesn't. The historic name of Mission.Summary.TOTAL_FUEL_MASS is INGASP.WFA, but does not include fuel margin in GASP while Mission.Design.FUEL_MASS_REQUIRED does.
  • Note: GASP Fortran code has items that are not implemented in Aviary (e.g. tail boom support, tip tank weight, fuselage acoustic treatment, pylon, acoustic treatment).

• In MassPremission group, a BWB mass group is built. Unit test is added for BWB model.

• Comparison to GASP model

Aviary		GASP		Observation
Aircraft.Nacelle.AVG_DIAMETER	7.18	DBARN	6.95	Different algorithms. Aviary use Aircraft.Engine.REFERENCE_DIAMETER
Aircraft.Design.FIXED_USEFUL_LOAD	5972	WFUL	5775	different unit weight of pilots and attendents
Aircraft.Wing.HIGH_LIFT_MASS	1069	WHLDEV	974	In GAST, wing loading is a variable, but in Aviary, it is a constant
Aircraft.Wing.MASS	7056	WW	6962	GASP includes winglet (7645 - 682.6)
Mission.Design.FUEL_MASS	35320	WFADES	33268	BodyTank algorithm is different
Aircraft.Fuel.TOTAL_CAPACITY	36836	WFAMAX	33268	BodyTank algorithm is different

Related Issues

• Resolves #

Backwards incompatibilities

None

New Dependencies

None

[jkirk5]

Documentation is very thorough, thanks for taking the time to add that detail
I have some minor change requests