def _getFuelInertia(self, timeSinceIgnition):
if self.initialFuelWeight == 0:
return Inertia(Vector(0, 0, 0), Vector(0, 0, 0), 0)
#See comments in _getOxInertia()
fuelWeight = linInterp(self.times, self.fuelWeights, timeSinceIgnition)
fuelBurnedFrac = 1 - (fuelWeight / self.initialFuelWeight)
fuelCG_Z = self.initFuelCG_Z * (
1 - fuelBurnedFrac) + self.finalFuelCG_Z * fuelBurnedFrac
fuelCG = Vector(0, 0, fuelCG_Z)
fuelMOI = linInterp(self.times, self.fuelMOIs, timeSinceIgnition)
return Inertia(fuelMOI, fuelCG, fuelWeight)
def _getOxInertia(self, timeSinceIgnition):
if self.initialOxidizerWeight == 0:
return Inertia(Vector(0, 0, 0), Vector(0, 0, 0), 0)
oxWeight = linInterp(self.times, self.oxWeights, timeSinceIgnition)
# Find fraction of oxidizer burned
oxBurnedFrac = 1 - (oxWeight / self.initialOxidizerWeight)
#Linearly interpolate CG location based on fraction of oxidizer burned
oxCG_Z = self.initOxCG_Z * (
1 - oxBurnedFrac) + self.finalOxCG_Z * oxBurnedFrac
#TODO: Allow motor(s) to be defined off-axis
oxCG = Vector(0, 0, oxCG_Z)
# Get MOI
oxMOI = linInterp(self.times, self.oxMOIs, timeSinceIgnition)
return Inertia(oxMOI, oxCG, oxWeight)
def getAppliedForce(self, state, time, environment, CG):
#TODO: Model "thrust damping" - where gases moving quickly in the engine act to damp out rotation about the x and y axes
#TODO: Thrust vs altitude compensation
timeSinceIgnition = max(0, time - self.ignitionTime)
# Determine thrust magnitude
if timeSinceIgnition < 0 or timeSinceIgnition > self.times[-1]:
thrustMagnitude = 0
else:
thrustMagnitude = linInterp(self.times, self.thrustLevels,
timeSinceIgnition)
# Create Vector
thrust = Vector(0, 0, thrustMagnitude)
return ForceMomentSystem(thrust)
def _getAeroCoefficients(self, state, environment):
keys = AeroParameters.getAeroPropertiesList(self.parameterFunctions,
state, environment)
if len(keys) > 1:
# Multi-dimensional linear interpolation
interpolatedCoefficients = self._interpAeroCoefficients(keys)[0]
else:
# 1D linear interpolation
interpolatedCoefficients = linInterp(self.keys, self.values,
keys[0])
aeroCoefficients = [0.0] * 5
for i in range(len(interpolatedCoefficients)):
indexInCoeffArray = self.aeroCoeffIndices[i]
aeroCoefficients[indexInCoeffArray] = interpolatedCoefficients[i]
return aeroCoefficients
def getInertia(self, time, state):
inertiaData = linInterp(self.times, self.inertiaData, time)
# MOI is last three columns, CG is the three before that, and mass is column 0
return Inertia(Vector(*inertiaData[-3:]), Vector(*inertiaData[1:4]),
inertiaData[0])
def test_linInterp(self):
self.assertEqual(linInterp([0, 1], [0, 1], 0.5), 0.5)
self.assertEqual(linInterp([0, 1, 2, 3], [0, 1, 3, 5], 1.5), 2)
self.assertEqual(linInterp([0, 1, 2, 3], [0, 1, 3, 5], 3), 5)
def getAirProperties(self, ASLElevation, _=None):
return linInterp(self.keys, self.values, ASLElevation)
def getMeanWind(self, AGLAltitude):
return Vector(*linInterp(self.windAltitudes, self.winds, AGLAltitude))