def forceVector(self, flightPitch, AoA, v, altitude = 0, planet = planet.kerbin, includeGravity = False):
"""
Returns (x, y) forces due to the airfoil.
Includes drag, lift, and the parasitic drag due to lift.
If includeGravity is set, also includes apparent gravity (taking into
account centrifugal effects).
flightPitch: angle of velocity vector relative to the surface (degrees)
AoA: angle of the airfoil relative to the velocity vector (degrees)
"""
lift = self.liftForce(AoA, v, altitude, planet)
drag = self.dragForce(AoA, v, altitude, planet)
liftAngle = math.radians(flightPitch + 90)
dragAngle = math.radians(flightPitch + 180)
(liftX, liftY) = (lift * math.cos(liftAngle), lift * math.sin(liftAngle))
(dragX, dragY) = (drag * math.cos(dragAngle), drag * math.sin(dragAngle))
if not includeGravity:
return (liftX + dragX, liftY + dragY)
# now compute apparent gravity
vOrbital = planet.orbitalVelocity(altitude)
vSrfHorizontal = math.cos(math.radians(flightPitch)) * v
vOrbHorizontal = vSrfHorizontal + planet.siderealSpeed(altitude)
gravityAccel = planet.gravity(altitude)
centrifugeAccel = vOrbHorizontal * vOrbHorizontal / (vOrbital * vOrbital)
apparentGravityForce = (centrifugeAccel - gravityAccel) * self.mass
return (liftX + dragX, liftY + dragY + apparentGravityForce)
def zeroThrustForces(self, flightPitchDegrees, AoADegrees, v, altitude, planet):
"""
Return the forces other than thrust that this part produces.
Returns a tuple (drag, lift, apparentGravity) with quantities in kN.
Lift and drag are vectors; gravity is a number (just the y coordinate, positive means up).
"""
Cd = self._staticCd
Clift = 0
if isinstance(self._parttype, lift.wing):
Cd = self._parttype.dragCoeff(self._AoA + AoADegrees)
Clift = self._parttype.liftCoeff(self._AoA + AoADegrees)
elif isinstance(self._parttype, jets.intake):
Cd = self._parttype.dragCoeff(self._AoA + AoADegrees)
elif isinstance(self._parttype, jets.jetengine):
Cd = 0.2
elif isinstance(self._parttype, engine.engine):
Cd = 0.2
dragMagnitude = planet.dragForce(altitude, v, self.mass(), Cd)
liftMagnitude = v * planet.pressure(altitude) * Clift
flightPitchRad = math.radians(flightPitchDegrees)
cosPitch = math.cos(flightPitchRad)
sinPitch = math.sin(flightPitchRad)
horizontalSpeedSrf = v * cosPitch
horizontalSpeedOrb = horizontalSpeedSrf + planet.siderealSpeed(altitude)
vOrbit = planet.orbitalVelocity(altitude)
centrifuge = horizontalSpeedOrb * horizontalSpeedOrb / (vOrbit * vOrbit)
gravity = planet.gravity(altitude)
downForceMagnitude = self.mass() * (centrifuge - gravity)
dragVector = physics.vector(-cosPitch * dragMagnitude, -sinPitch * dragMagnitude)
liftVector = physics.vector(-sinPitch * liftMagnitude, cosPitch * liftMagnitude)
return (dragVector, liftVector, downForceMagnitude)
