def __init__(self,
initial_radius=0.0,
final_radius=0.0,
gravitational_parameter=0.0,
transfer_apoapsis=0.0,
start_time=0.0):
"""
:param initial_radius: (float) The radius of the initial circular orbit.
:param final_radius: (float) The radius of the final circular orbit.
:param gravitational_parameter: (float) Gravitational parameter.
:param transfer_apoapsis: (float) The apoapsis distance of the transfer orbits.
:param start_time: (float/datetime object) The starting time of the maneuver (default is 0.0s).
"""
self.initial_radius = initial_radius
self.final_radius = final_radius
self.gravitational_parameter = gravitational_parameter
self.transfer_apoapsis = transfer_apoapsis
self.start_time = start_time
self._semi_major_axis_one = semi_major_axis(
radii=True,
radius_one=self.initial_radius,
radius_two=self.transfer_apoapsis)
self._semi_major_axis_two = semi_major_axis(
radii=True,
radius_one=self.final_radius,
radius_two=self.transfer_apoapsis)
def __init__(self,
initial_radius=0.0,
final_radius=0.0,
gravitational_parameter=0.0,
transfer_eccentricity=0.0,
start_time=0.0):
"""
:param initial_radius: (float) The radius of the initial circular orbit.
:param final_radius: (float) The radius of the final circular orbit.
:param gravitational_parameter: (float) Gravitational parameter.
:param transfer_eccentricity: (float) The eccentricity of the desired transfer orbit.
:param start_time: (float/datetime object) The starting time of the maneuver (default is 0.0s).
"""
self.initial_radius = initial_radius
self.final_radius = final_radius
self.transfer_eccentricity = transfer_eccentricity
self.gravitational_parameter = gravitational_parameter
self.start_time = start_time
a = semi_major_axis(radii=True,
radius_one=self.initial_radius,
radius_two=self.final_radius)
semi_latus_rectum = a * (1 - self.transfer_eccentricity**2)
periapsis = periapsis_length(semi_latus_rectum,
self.transfer_eccentricity,
semi_major_axis=False)
apoapsis = apoapsis_length(semi_latus_rectum,
self.transfer_eccentricity,
semi_major_axis=False)
if (periapsis > min(self.initial_radius, self.final_radius)) or \
(apoapsis < max(self.initial_radius, self.final_radius)):
raise Exception(
'Invalid initial_radius, final_radius, and/or transfer_eccentricity value(s).'
)
self._angular_momentum_transfer = (self.gravitational_parameter *
semi_latus_rectum)**0.5
self._initial_speed_circular = circular_speed(
self.initial_radius, self.gravitational_parameter)
self._initial_speed_transfer = vis_viva(self.initial_radius, a,
self.gravitational_parameter)
self._final_speed_transfer = vis_viva(self.final_radius, a,
self.gravitational_parameter)
self._final_speed_circular = circular_speed(
self.final_radius, self.gravitational_parameter)
def transfer_time(initial_radius,
final_radius,
eccentricity=0.0,
rounding=None,
gravitational_parameter=Earth.gravitational_parameter):
""" The time of flight during a hohmann, bi elliptic, or general transfer orbit.
:param initial_radius: (float) The periapsis distance of the transfer orbit.
:param final_radius: (float) The apoapsis distance of the transfer orbit.
:param eccentricity: (float) The eccentricity of the transfer orbit; only needed for general transfers
(default is 0.0).
:param rounding: (int or None) Number that indicates the amount of decimal places to round to (default is None).
:param gravitational_parameter: (float) Gravitational parameter (default is Earth.gravitational_parameter).
:return: (float) The transfer time.
"""
a = semi_major_axis(radii=True,
radius_one=initial_radius,
radius_two=final_radius)
if eccentricity == 0:
if rounding is None:
return period(a, gravitational_parameter) / 2
else:
return round(period(a, gravitational_parameter) / 2, rounding)
else:
p = a * (1 - eccentricity**2)
true_anomaly_one = math.acos(
(((p / initial_radius) - 1) / eccentricity))
true_anomaly_two = math.acos((((p / final_radius) - 1) / eccentricity))
time = flight_time(eccentricity,
p,
true_anomaly_one,
true_anomaly_two,
gravitational_parameter=gravitational_parameter)
if initial_radius > final_radius:
time *= -1
if rounding is None:
return time
else:
return round(time, rounding)
def semi_major_axis(self):
""" The semi-major axis of the orbit. """
return semi_major_axis(semi_latus_rectum=self.semi_latus_rectum,
eccentricity=self.eccentricity)