Source code for RCAIDE.Library.Mission.Segments.Cruise.Constant_Speed_Constant_Altitude
# RCAIDE/Library/Missions/Segments/Cruise/Constant_Speed_Constant_Altitude.py
#
#
# Created: Jul 2023, M. Clarke
# ----------------------------------------------------------------------------------------------------------------------
# IMPORT
# ----------------------------------------------------------------------------------------------------------------------
# Package imports
import numpy as np
# ----------------------------------------------------------------------------------------------------------------------
# Initialize Conditions
# ----------------------------------------------------------------------------------------------------------------------
[docs]
def initialize_conditions(segment):
"""
Initializes conditions for constant speed cruise at fixed altitude
Parameters
----------
segment : Segment
The mission segment being analyzed
- altitude : float
Cruise altitude [m]
- distance : float
Ground distance to cover [m]
- air_speed : float
True airspeed to maintain [m/s]
- sideslip_angle : float
Aircraft sideslip angle [rad]
- state:
numerics.dimensionless.control_points : array
Discretization points [-]
conditions : Data
State conditions container
initials : Data, optional
Initial conditions from previous segment
Returns
-------
None
Updates segment conditions directly:
- conditions.frames.inertial.velocity_vector [m/s]
- conditions.frames.inertial.position_vector [m]
- conditions.freestream.altitude [m]
- conditions.frames.inertial.time [s]
Notes
-----
This function sets up the initial conditions for a cruise segment with constant
true airspeed and constant altitude. The segment duration is determined by the
specified ground distance to cover.
**Calculation Process**
1. Check for initial conditions
2. Calculate time required based on distance and speed:
t = x/V where:
- x is ground distance
- V is true airspeed
3. Discretize time points
4. Decompose velocity into components using sideslip angle
**Major Assumptions**
* Constant true airspeed
* Constant altitude
* Small angle approximations
* Quasi-steady flight
* No wind effects
See Also
--------
RCAIDE.Framework.Mission.Segments
"""
# unpack
alt = segment.altitude
xf = segment.distance
air_speed = segment.air_speed
beta = segment.sideslip_angle
conditions = segment.state.conditions
# check for initial velocity
if air_speed is None:
if not segment.state.initials: raise AttributeError('airspeed not set')
air_speed = np.linalg.norm(segment.state.initials.conditions.frames.inertial.velocity_vector[-1])
# check for initial altitude
if alt is None:
if not segment.state.initials: raise AttributeError('altitude not set')
alt = -1.0 * segment.state.initials.conditions.frames.inertial.position_vector[-1,2]
# dimensionalize time
v_x = np.cos(beta)*air_speed
v_y = np.sin(beta)*air_speed
t_initial = conditions.frames.inertial.time[0,0]
t_final = xf /air_speed + t_initial
t_nondim = segment.state.numerics.dimensionless.control_points
time = t_nondim * (t_final-t_initial) + t_initial
# pack
segment.state.conditions.freestream.altitude[:,0] = alt
segment.state.conditions.frames.inertial.position_vector[:,2] = -alt # z points down
segment.state.conditions.frames.inertial.velocity_vector[:,0] = v_x
segment.state.conditions.frames.inertial.velocity_vector[:,1] = v_y
segment.state.conditions.frames.inertial.time[:,0] = time[:,0]
