def evaluate(self, state, diff, dt):
new_state = State(
state.position + diff.drdt * dt,
state.velocity + diff.dvdt * dt,
state.log_mass + diff.dmdt * dt,
)
if new_state.log_mass < -100:
raise OverflowError
coordinates = new_state.position.to_WGS84()
air_density = atmosphere.air_density(coordinates.alt)
speed = new_state.velocity.norm()
reynolds = atmosphere.Reynolds_number(self.radius, new_state.velocity.norm(), air_density / constants.AIR_VISCOSITY)
gamma = 1 #atmosphere.drag_coefficient_smooth_sphere(reynolds)
drag_vector = -(gamma * self.shape_factor * air_density * speed / (np.exp(new_state.log_mass / 3) * self.density**(2 / 3))) * new_state.velocity
gravity_vector = -constants.GRAVITATIONAL_CONSTANT * constants.EARTH_MASS / new_state.position.norm()**3 * new_state.position
coriolis_vector = -2 * EARTH_ROTATION ^ new_state.velocity
huygens_vector = -EARTH_ROTATION ^ (EARTH_ROTATION ^ new_state.position)
log_mass_change = -(self.heat_transfer * self.shape_factor * air_density * speed**3 * np.exp(-new_state.log_mass / 3) * self.density**(-2 / 3) / (2 * self.ablation_heat))
return Diff(
new_state.velocity,
drag_vector + gravity_vector + coriolis_vector + huygens_vector,
log_mass_change,
)
def save_snapshot(self, state, *, wgs84):
coordinates = self.position.to_WGS84() if wgs84 else self.position.to_spherical()
speed = self.velocity.norm()
self.air_density = atmosphere.air_density(coordinates.alt)
self.velocity_altaz = self.velocity.dxdydz_to_altaz_at(self.position)
self.mass = np.exp(self.log_mass)
self.radius = ((3 * self.mass) / (4 * np.pi * self.density))**(1 / 3)
self.reynolds_number = atmosphere.Reynolds_number(2 * self.radius, speed, self.air_density)
self.gamma = atmosphere.drag_coefficient_smooth_sphere(self.reynolds_number)
self.dynamic_pressure = self.air_density * speed**2
self.acceleration = state.dvdt.norm()
self.mass_change = self.mass * state.dmdt
self.luminous_power = -(radiometry.luminous_efficiency(speed) * self.mass_change * speed**2 / 2.0)
self.absolute_magnitude = radiometry.absolute_magnitude(self.luminous_power)
self.frames.append(models.frame.Frame(self))
def testDensity10km(self):
self.assertAlmostEqual(atmosphere.air_density(10000), 0.42, delta=0.01)
def testDensityTooHigh(self):
self.assertEqual(atmosphere.air_density(600000), 0)