def forceFromCoefficients(rocketState, environment, Cd, Cl, CMx, CMy, CMz,
CPLocation, refArea, refLength):
''' Initialize ForceMomentSystem from all aerodynamic coefficients '''
q = AeroParameters.getDynamicPressure(rocketState, environment)
if q == 0.0:
# No force without dynamic pressure
return ForceMomentSystem(Vector(0, 0, 0))
nonDimConstant = q * refArea
#### Drag ####
localFrameAirVel = AeroParameters.getLocalFrameAirVel(
rocketState, environment)
dragDirection = localFrameAirVel.normalize()
dragForce = dragDirection * Cd
#### Lift ####
# Find the lift force direction
# Lift force will be in the same plane as the normalForceDirection & rocketFrameAirVel vectors
# But, the lift force will be perpendicular to rocketFraeAirVel, whereas the normalForceDirection might form an acute angle with it
# Rotate the normal force direction vector until it's perpendicular with rocketFrameAirVel
normalForceDir = AeroParameters.getNormalAeroForceDirection(
rocketState, environment)
rotAxis = localFrameAirVel.crossProduct(normalForceDir)
angle = math.pi / 2 - localFrameAirVel.angle(normalForceDir)
rotatorQuat = Quaternion(rotAxis, angle)
liftDirection = rotatorQuat.rotate(normalForceDir)
liftForce = liftDirection * Cl
# Combine and redimensionalize
totalForce = (dragForce + liftForce) * nonDimConstant
#### Moments ####
moments = Vector(CMx, CMy, CMz) * nonDimConstant * refLength
return ForceMomentSystem(totalForce, CPLocation, moments)
def getAppliedForce(self, rocketState, time, environment, CG):
'''
Calculates force/moment applied by the recovery system using a simple drag coefficient + area model
'''
#### Calculate Aero Force ####
if self.currentStage == 0:
# No recovery system deployed yet
return ForceMomentSystem(Vector(0,0,0))
else:
# 3DoF force-only aero
airVel = AeroParameters.getAirVelRelativeToVehicle(rocketState, environment)
dragForceMagnitude = self.chuteCds[self.currentStage] * self.chuteAreas[self.currentStage] * AeroParameters.getDynamicPressure(rocketState, environment)
totalForce = airVel.normalize() * dragForceMagnitude
return ForceMomentSystem(totalForce)
def getAppliedForce(self, rocketState, time, environment, CG):
#### If control system exists, use actuator deflections 1:1 to set fin angles ####
if self.controlSystem != None:
# Update fin angles
for i in range(self.numFins):
self.finList[i].finAngle = self.actuatorList[i].getDeflection(
time)
#### Pre-calculate common properties for all child Fins ####
precomputedData = self._getPreComputedFinAeroData(
rocketState, environment, CG)
#### Add up forces from all child Fins ####
aeroForce = ForceMomentSystem(Vector(0, 0, 0), self.position)
for fin in self.finList:
aeroForce += fin.getAppliedForce(rocketState, time, environment,
CG, precomputedData)
# TODO: Correct for sub/transonic rolling moment fin-fin interference from a high number of fins
# Apply fin-body interference factor to total forces in the normal (X/Y) directions and moments
totalInterferenceFactor = self.bodyOnFinInterferenceFactor * self.finNumberInterferenceFactor
aeroForce.force.X *= totalInterferenceFactor
aeroForce.force.Y *= totalInterferenceFactor
aeroForce.moment.X *= totalInterferenceFactor
aeroForce.moment.Y *= totalInterferenceFactor
return aeroForce
def forceFromCdCN(rocketState,
environment,
Cd,
CN,
CPLocation,
refArea,
moment=None):
'''
Convenience function for Barrowman Aero methods
Initialize ForceMomentSystem from aerodynamic coefficients Cd and CN
Cd should NOT already be adjusted for angle of attack
Moment should be a dimensional moment vector
'''
angleOfAttack = AeroParameters.getTotalAOA(rocketState, environment)
q = AeroParameters.getDynamicPressure(rocketState, environment)
#### Axial Force ####
CA = getDragToAxialForceFactor(angleOfAttack) * Cd
axialForce = Vector(0, 0, -CA) #Axial force is in the negative Z-direction
#### Normal Force ####
normalForce = AeroParameters.getNormalAeroForceDirection(
rocketState, environment) * CN
totalForce = (axialForce + normalForce) * refArea * q
return ForceMomentSystem(totalForce, CPLocation, moment)
def __init__(self, componentDictReader, rocket, stage):
self.rocket = rocket
self.stage = stage
self.componentDictReader = componentDictReader
self.name = componentDictReader.getDictName()
mass = componentDictReader.getFloat("mass")
# Position in simulation definition is relative to stage position
self.position = componentDictReader.getVector(
"position"
) + stage.position # Store position relative to nosecone here
# CG in simulation definition is relative to component position
cg = componentDictReader.getVector(
"cg"
) + self.position # Store cg location relative to nosecone here
try:
MOI = componentDictReader.getVector("MOI")
except:
MOI = Vector(mass * 0.01, mass * 0.01,
mass * 0.01) # Avoid having zero moments of inertia
self.inertia = Inertia(MOI, cg, mass)
self.zeroForce = ForceMomentSystem(Vector(0, 0, 0))
def uniformlyAcceleratingRotationTest(self, integrationMethod):
constantZMoment = ForceMomentSystem(self.zeroVec,
moment=Vector(0, 0, 1))
restingState = RigidBodyState(self.zeroVec, self.zeroVec,
self.zeroQuat, self.zeroAngVel)
def constZMomentFunc(*allArgs):
return constantZMoment
def constInertiaFunc(*allArgs):
return self.constInertia
acceleratingZRotBody = RigidBody(restingState,
constZMomentFunc,
constInertiaFunc,
integrationMethod=integrationMethod,
simDefinition=self.simDefinition)
acceleratingZRotBody.timeStep(1)
newOrientation = acceleratingZRotBody.state.orientation
newAngVel = acceleratingZRotBody.state.angularVelocity
#print("{}: {}".format(integrationMethod, newOrientation))
assertAngVelAlmostEqual(
self, newAngVel,
AngularVelocity(axisOfRotation=Vector(0, 0, 1), angularVel=1))
if integrationMethod == "Euler":
assertQuaternionsAlmostEqual(
self, newOrientation,
Quaternion(axisOfRotation=Vector(0, 0, 1), angle=0))
else:
assertQuaternionsAlmostEqual(
self, newOrientation,
Quaternion(axisOfRotation=Vector(0, 0, 1), angle=0.5))
def uniformXAccelerationTest(self, integrationMethod):
constantXForce = ForceMomentSystem(Vector(1, 0, 0))
movingXState = RigidBodyState(self.zeroVec, self.zeroVec,
self.zeroQuat, self.zeroAngVel)
def constInertiaFunc(*allArgs):
return self.constInertia
def constXForceFunc(*allArgs):
return constantXForce
movingXBody = RigidBody(movingXState,
constXForceFunc,
constInertiaFunc,
integrationMethod=integrationMethod,
simDefinition=self.simDefinition)
movingXBody.timeStep(1)
newPos = movingXBody.state.position
newVel = movingXBody.state.velocity
assertVectorsAlmostEqual(self, newVel, Vector(1, 0, 0))
if integrationMethod == "Euler":
assertVectorsAlmostEqual(self, newPos, Vector(0, 0, 0))
else:
assertVectorsAlmostEqual(self, newPos, Vector(0.5, 0, 0))
def setUp(self):
self.appliedForce1 = ForceMomentSystem(Vector(0, 0,
10), Vector(1, 0, 0),
Vector(0, 0, 0))
self.appliedForce2 = ForceMomentSystem(Vector(0, 0,
10), Vector(2, 0, 0),
Vector(0, 0, 0))
self.appliedForce3 = ForceMomentSystem(Vector(10, 0,
0), Vector(0, 1, 0),
Vector(0, 0, 0))
self.correctForce1 = ForceMomentSystem(Vector(0, 0, 20),
Vector(0, 0, 0),
Vector(0, -30, 0))
self.correctForce2 = ForceMomentSystem(Vector(10, 0, 10),
Vector(0, 0, 0),
Vector(0, -10, -10))
def test_fixedForceInit(self):
simDef = SimDefinition("MAPLEAF/Examples/Simulations/FixedForce.mapleaf", silent=True)
rocketDictReader = SubDictReader("Rocket", simDef)
rocket = Rocket(rocketDictReader, silent=True)
fixedForce = rocket.stages[0].getComponentsOfType(FixedForce)[0]
expectedFMS = ForceMomentSystem(Vector(0,0,0), Vector(0,0,0), Vector(0,1,0))
assertForceMomentSystemsAlmostEqual(self, fixedForce.force, expectedFMS)
def test_CPZ(self):
force = Vector(0, 1, 0)
location = Vector(0, 0, 0)
moment = Vector(1, 0, 0)
testForce = ForceMomentSystem(force, location, moment)
expectedCPZ = -1
calculatedCPZ = AeroFunctions._getCPZ(testForce)
self.assertAlmostEqual(expectedCPZ, calculatedCPZ)
def __init__(self, componentDictReader, rocket, stage):
self.rocket = rocket
self.stage = stage
self.componentDictReader = componentDictReader
self.name = componentDictReader.getDictName()
self.zeroForce = ForceMomentSystem(Vector(0, 0, 0))
inertiaTableFilePath = componentDictReader.getString("filePath")
self._parseInertiaTable(inertiaTableFilePath)
def test_zeroSag(self):
unadjustedForce = ForceMomentSystem(Vector(10, 9, -10),
moment=Vector(10, 11, 12))
adjustedForce = self.rail.applyLaunchTowerForce(
self.initState, 0, unadjustedForce)
# Check that force is zero (don't let object sag/fall)
assertVectorsAlmostEqual(self, adjustedForce.force, Vector(0, 0, 0))
# Check moments are zero
assertVectorsAlmostEqual(self, adjustedForce.moment, Vector(0, 0, 0))
def test_getFixedForce(self):
simDef = SimDefinition("MAPLEAF/Examples/Simulations/FixedForce.mapleaf", silent=True)
rocketDictReader = SubDictReader("Rocket", simDef)
rocket = Rocket(rocketDictReader, silent=True)
fixedForce = rocket.stages[0].getComponentsOfType(FixedForce)[0]
force = fixedForce.getAppliedForce("fakeState", 0, "fakeEnv", Vector(0,0,0))
expectedForce = ForceMomentSystem(Vector(0,0,0), moment=Vector(0,1,0))
self.assertEqual(force.force, expectedForce.force)
self.assertEqual(force.moment, expectedForce.moment)
def getAppliedForce(self, rocketState, time, envConditions, rocketCG):
mag = -2000 * self.getTankLevelDerivative(
time, rocketState
) # Force magnitude proportional to flow rate out of the tank
forceVector = Vector(0, 0, mag)
self.rocket.appendToForceLogLine(
" {:>6.4f}".format(mag)
) # This will end up in the log file, in the SampleZForce column
return ForceMomentSystem(forceVector)
def test_LeaveRail(self):
unadjustedForce = ForceMomentSystem(Vector(10, 9, 11),
moment=Vector(10, 11, 12))
self.initState.position = Vector(4, 0, 4) # Greater than 5m away
adjustedForce = self.rail.applyLaunchTowerForce(
self.initState, 0, unadjustedForce)
# Check that forces/moments are unaffected
assertVectorsAlmostEqual(self, adjustedForce.force, Vector(10, 9, 11))
assertVectorsAlmostEqual(self, adjustedForce.moment,
Vector(10, 11, 12))
def test_alignForceWithRail(self):
unadjustedForce = ForceMomentSystem(Vector(10, 9, 11),
moment=Vector(10, 11, 12))
adjustedForce = self.rail.applyLaunchTowerForce(
self.initState, 0, unadjustedForce)
# Check that force direction is now aligned with rail
forceDirection = adjustedForce.force.normalize()
assertVectorsAlmostEqual(self, self.rail.initialDirection,
forceDirection)
# Check moments are zero
assertVectorsAlmostEqual(self, adjustedForce.moment, Vector(0, 0, 0))
def getAppliedForce(self, rocketState, time, environmentalConditions,
rocketCG):
# Only apply damping force if current stage's engine is firing
# (Other stage's motors will have different exit planes)
if time > self.stage.motor.ignitionTime and time < self.stage.engineShutOffTime:
currentRocketInertia = self.rocket.getInertia(time, rocketState)
# Differentiate rate of MOI change
dt = 0.001
nextRocketInertia = self.rocket.getInertia(time + dt, rocketState)
MOIChangeRate = (currentRocketInertia.MOI.X -
nextRocketInertia.MOI.X) / dt
dampingFactor = MOIChangeRate * self.dampingFraction
angVel = rocketState.angularVelocity
dampingMoment = Vector(-angVel.X * dampingFactor,
-angVel.Y * dampingFactor, 0)
return ForceMomentSystem(Vector(0, 0, 0), moment=dampingMoment)
else:
return ForceMomentSystem(Vector(0, 0, 0))
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 __init__(self, componentDictReader, rocket, stage):
''' A Zero-inertia component that applies a constant ForceMomentSystem to the rocket '''
self.componentDictReader = componentDictReader
self.rocket = rocket
self.stage = stage
self.name = componentDictReader.getDictName()
# Object is just a force, inertia is zero
self.inertia = Inertia(Vector(0, 0, 0), Vector(0, 0, 0), 0)
force = componentDictReader.getVector("force")
forceLocation = componentDictReader.getVector("position")
moment = componentDictReader.getVector("moment")
self.force = ForceMomentSystem(force, forceLocation, moment)
def test_combineForceMomentSystems_2(self):
# Example Question 16 - http://www.ce.siue.edu/examples/Worked_examples_Internet_text-only/Data_files-Worked_Exs-Word_&_pdf/Equivalent_forces.pdf
# Define Force-Moment 1
force1 = Vector(0, -3.464, -2)
m1 = Vector(0, -51.962, -30)
location1 = Vector(4, 1.5, 4.402)
fms1 = ForceMomentSystem(force1, location1, m1)
# Define Force-Moment 2
force2 = Vector(-6, 0, 0)
m2 = Vector(-80, 0, 0)
location2 = Vector(8, 1.5, 1)
fms2 = ForceMomentSystem(force2, location2, m2)
# Combine
combinedForce = fms1 + fms2
combinedForceAtOrigin = combinedForce.getAt(Vector(0, 0, 0))
# Define correct/expected result
expectedResultantForce = Vector(-6, -3.464, -2)
expectedResultantMoment = Vector(
12.249, 2, -4.856
) # Only includes moments generated by forces, not the moments applied
resultantLocation = Vector(0, 0, 0)
expectedResult = ForceMomentSystem(expectedResultantForce,
resultantLocation,
expectedResultantMoment)
# Compare
from test.testUtilities import assertVectorsAlmostEqual
assertVectorsAlmostEqual(self, combinedForceAtOrigin.force,
expectedResult.force)
assertVectorsAlmostEqual(self, combinedForceAtOrigin.location,
expectedResult.location)
assertVectorsAlmostEqual(self, combinedForceAtOrigin.moment - m1 - m2,
expectedResult.moment, 3)
def setUp(self):
self.zeroVec = Vector(0, 0, 0)
self.zeroQuat = Quaternion(axisOfRotation=Vector(1, 0, 0), angle=0)
self.zeroAngVel = AngularVelocity(axisOfRotation=Vector(1, 0, 0),
angularVel=0)
self.zeroForce = ForceMomentSystem(self.zeroVec)
self.oneVec = Vector(1, 1, 1)
self.simDefinition.setValue(
"SimControl.TimeStepAdaptation.minTimeStep", "1")
#TODO: Get some tests for the higher order adaptive methods in here
self.integrationMethods = [
"Euler", "RK2Heun", "RK2Midpoint", "RK4", "RK12Adaptive"
]
self.constInertia = Inertia(self.oneVec, self.zeroVec, 1)
def getGravityForce(self, inertia, state) -> ForceMomentSystem:
'''
Inputs:
inertia: (`MAPLEAF.Motion.Inertia`)
state: (`MAPLEAF.Motion.RigidBodyState`/`MAPLEAF.Motion.RigidBodyState_3DoF`)
Returns:
gravityForce: (ForceMomentSystem) defined in the rocket's local frame
'''
# Get gravity force in the global frame
gravityForce = self.earthModel.getGravityForce(inertia, state)
try:
# Convert to local frame if in 6DoF simulation
gravityForce = state.orientation.conjugate().rotate(gravityForce) # rotate into local frame when in 6DoF mode
except AttributeError:
pass # Don't do anything in 3DoF mode (No local frame exists)
return ForceMomentSystem(gravityForce, inertia.CG)
def getAppliedForce(self, state, time, environmentalConditions, rocketCG):
'''
Computes the aerodynamic force experienced by the stage.
Does not include gravitational force - gravity is added at the rocket level.
'''
# Add up forces from all subcomponents
totalAppliedComponentForce = ForceMomentSystem(Vector(0, 0, 0),
rocketCG)
for component in self.components:
componentForce = component.getAppliedForce(
state, time, environmentalConditions, rocketCG)
# Log applied forces and moments if desired
if hasattr(component, "forcesLog"):
component.forcesLog.append(componentForce.force)
component.momentsLog.append(componentForce.moment)
totalAppliedComponentForce += componentForce
return totalAppliedComponentForce
def applyLaunchTowerForce(self, state, time, unadjustedForce):
'''
If on launch tower, projects forces experienced onto the launch tower directions and sets Moments = 0
Returns two values: onTower(Bool), adjustedForce(Motion.ForceMomentSystem)
'''
distanceTravelled = (state.position - self.getPosition(time)).length()
if distanceTravelled < self.length:
# Vehicle still on launch rail
# Project total force onto the launch rail direction (dot product)
adjustedForceMagnitude = unadjustedForce.force * self.getDirection(
time)
adjustedForceVector = self.initialDirection * adjustedForceMagnitude
# No resultant moments while on the launch rail
adjustedForce = ForceMomentSystem(adjustedForceVector)
return adjustedForce
else:
# Vehicle has left the rail
return unadjustedForce
def test_nonPrincipalAxisRotation(self):
initAngVel = AngularVelocity(rotationVector=Vector(1, 0, 1))
rotatingZState = RigidBodyState(self.zeroVec, self.zeroVec,
self.zeroQuat, initAngVel)
constForce = ForceMomentSystem(self.zeroVec)
def constForceFunc(*allArgs):
return constForce
constInertia = Inertia(Vector(2, 2, 8), self.zeroVec, 1)
def constInertiaFunc(*allArgs):
return constInertia
rotatingZBody = RigidBody(rotatingZState,
constForceFunc,
constInertiaFunc,
integrationMethod="RK4",
simDefinition=self.simDefinition)
dt = 0.01
nTimeSteps = 10
totalTime = dt * nTimeSteps
for i in range(nTimeSteps):
rotatingZBody.timeStep(dt)
finalAngVel = rotatingZBody.state.angularVelocity
omega = (constInertia.MOI.Z - constInertia.MOI.X) / constInertia.MOI.X
expectedAngVel = AngularVelocity(
rotationVector=Vector(cos(omega * totalTime), sin(omega *
totalTime), 1))
assertAngVelAlmostEqual(self, finalAngVel, expectedAngVel)
def step1MomentFunc(*allArgs):
return ForceMomentSystem(
self.zeroVec, moment=Vector(0, 0.5, 0)
) #Acceleration and deceleration steps to give 90 degree rotations in each axis
def step2MomentFunc(*allArgs):
return ForceMomentSystem(self.zeroVec, moment=Vector(
0, -0.5, 0)) #using a time step of pi
def step3MomentFunc(*allArgs):
return ForceMomentSystem(
self.zeroVec, moment=Vector(0, 0, 0.5)
) #There is one acceleration and one deceleration for each rotation to make it static
def step4MomentFunc(*allArgs):
return ForceMomentSystem(self.zeroVec, moment=Vector(0, 0, -0.5))
def _barrowmanAeroFunc(self,
rocketState,
time,
environment,
precomputedData,
CG=Vector(0, 0, 0),
finDeflectionAngle=None):
'''
Precomputed Data is a named tuple (PreComputedFinAeroData) which contains data/results from the parts of the fin aerodynamics calculation
that are common to all fins in a FinSet (drag calculations mostly). These calculations are performed at the FinSet level.
Only the parts of the Fin Aero Computation that change from fin to fin (normal force mostly, since different fins can have different angles of attack) are computed here
'''
Mach = AeroParameters.getMachNumber(rocketState, environment)
dynamicPressure = AeroParameters.getDynamicPressure(
rocketState, environment)
if finDeflectionAngle == None:
finDeflectionAngle = self.finAngle # Adjusted by parent finset during each timestep, when the FinSet is controlled
# Unpack precomputedData
airVelRelativeToFin, CPXPos, totalDragCoefficient = precomputedData
#### Compute normal force-----------------------------------------------------------------------------------------------------------------
# Find fin normal vector after fin deflection
finDeflectionRotation = Quaternion(
axisOfRotation=self.spanwiseDirection,
angle=radians(finDeflectionAngle))
finNormal = finDeflectionRotation.rotate(self.undeflectedFinNormal)
# Get the tangential velocity component vector, per unit radial distance from the rocket centerline
rollAngVel = AngularVelocity(0, 0, rocketState.angularVelocity.Z)
unitSpanTangentialAirVelocity = rollAngVel.crossProduct(
self.spanwiseDirection) * (-1)
def subsonicNormalForce(Mach): # Subsonic linear method
tempBeta = AeroParameters.getBeta(Mach)
CnAlpha = getFinCnAlpha_Subsonic_Barrowman(self.span,
self.planformArea,
tempBeta,
self.midChordSweep)
return getSubsonicFinNormalForce(airVelRelativeToFin,
unitSpanTangentialAirVelocity,
finNormal, self.spanwiseDirection,
self.CPSpanWisePosition.length(),
CnAlpha, self)
def supersonicNormalForce(Mach): # Supersonic Busemann method
gamma = AeroFunctions.getGamma()
tempBeta = AeroParameters.getBeta(Mach)
K1, K2, K3, Kstar = getBusemannCoefficients(Mach, tempBeta, gamma)
# Mach Cone coords
machAngle = asin(1 / Mach)
machCone_negZPerRadius = 1 / tan(machAngle)
machConeEdgeZPos = []
outerRadius = self.spanSliceRadii[-1]
for i in range(len(self.spanSliceRadii)):
machConeAtCurrentRadius = (
outerRadius - self.spanSliceRadii[i]
) * machCone_negZPerRadius + self.tipPosition
machConeEdgeZPos.append(machConeAtCurrentRadius)
return getSupersonicFinNormalForce(
airVelRelativeToFin, unitSpanTangentialAirVelocity, finNormal,
machConeEdgeZPos, self.spanwiseDirection,
self.CPSpanWisePosition.length(), K1, K2, K3, Kstar, self)
if Mach <= 0.8:
normalForceMagnitude, finMoment = subsonicNormalForce(Mach)
elif Mach < 1.4:
# Interpolate in transonic region
# TODO: Do this with less function evaluations? Perhaps precompute AOA and Mach combinations and simply interpolate? Lazy precompute? Cython?
x1, x2 = 0.8, 1.4 # Start, end pts of interpolated region
dx = 0.001
# Find normal force and derivative at start of interpolation interval
f_x1, m_x1 = subsonicNormalForce(x1)
f_x12, m_x12 = subsonicNormalForce(x1 + dx)
# Find normal force and derivative at end of interpolation interval
f_x2, m_x2 = supersonicNormalForce(x2)
f_x22, m_x22 = supersonicNormalForce(x2 + dx)
normalForceMagnitude = Interpolation.cubicInterp(
Mach, x1, x2, f_x1, f_x2, f_x12, f_x22, dx)
finMoment = Interpolation.cubicInterp(Mach, x1, x2, m_x1, m_x2,
m_x12, m_x22, dx)
else:
normalForceMagnitude, finMoment = supersonicNormalForce(Mach)
# Complete redimensionalization of normal force coefficients by multiplying by dynamic pressure
# Direct the normal force along the fin's normal direction
normalForce = normalForceMagnitude * dynamicPressure * finNormal
finMoment *= dynamicPressure
#### Get axial force-----------------------------------------------------------------------------------------------------------------------
avgAOA = getFinSliceAngleOfAttack(
self.spanSliceRadii[round(len(self.spanSliceAreas) / 2)],
airVelRelativeToFin, unitSpanTangentialAirVelocity, finNormal,
self.spanwiseDirection,
self.stallAngle) # Approximate average fin AOA
totalAxialForceCoefficient = AeroFunctions.getDragToAxialForceFactor(
avgAOA) * totalDragCoefficient
axialForceMagnitude = totalAxialForceCoefficient * self.rocket.Aref * dynamicPressure
axialForceDirection = self.spanwiseDirection.crossProduct(finNormal)
axialForce = axialForceDirection * axialForceMagnitude
#### Get CP Location ----------------------------------------------------------------------------------------------------------------------
CPChordWisePosition = self.position - Vector(
0, 0, CPXPos
) # Ignoring the change in CP position due to fin deflection for now
globalCP = self.CPSpanWisePosition + CPChordWisePosition
#### Assemble total force moment system objects--------------------------------------------------------------------------------------------
totalForce = normalForce + axialForce
return ForceMomentSystem(totalForce,
globalCP,
moment=Vector(0, 0, finMoment)), globalCP
