Source code for RCAIDE.Library.Mission.Segments.Cruise.Constant_Mach_Constant_Altitude
# RCAIDE/Library/Missions/Segments/Cruise/Constant_Mach_Constant_Altitude.py
#
#
# Created: Jul 2023, M. Clarke
# ----------------------------------------------------------------------------------------------------------------------
# IMPORT
# ----------------------------------------------------------------------------------------------------------------------
# RCAIDE
import RCAIDE
# Package imports
import numpy as np
# ----------------------------------------------------------------------------------------------------------------------
# Initialize Conditions
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[docs]
def initialize_conditions(segment):
"""
Initializes conditions for constant Mach cruise at fixed altitude
Parameters
----------
segment : Segment
The mission segment being analyzed
- altitude : float
Cruise altitude [m]
- distance : float
Ground distance to cover [m]
- mach_number : float
Mach number to maintain [-]
- sideslip_angle : float
Aircraft sideslip angle [rad]
- state:
numerics.dimensionless.control_points : array
Discretization points [-]
conditions : Data
State conditions container
- analyses:
atmosphere : Model
Atmospheric model for property calculations
Notes
-----
This function sets up the initial conditions for a cruise segment with constant
Mach number and constant altitude. The true airspeed is determined from the
Mach number and local speed of sound.
**Calculation Process**
1. Get atmospheric properties at altitude
2. Calculate true airspeed from Mach number:
V = M * a where:
- M is Mach number
- a is speed of sound
3. Calculate time required based on distance and speed
4. Discretize time points
5. Decompose velocity into components using sideslip angle
**Major Assumptions**
* Constant Mach number
* Constant altitude
* Standard atmosphere model
* Small angle approximations
* Quasi-steady flight
* No wind effects
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]
See Also
--------
RCAIDE.Framework.Mission.Segments
RCAIDE.Library.Mission.Common.Update.atmosphere
"""
# unpack
alt = segment.altitude
xf = segment.distance
mach = segment.mach_number
beta = segment.sideslip_angle
conditions = segment.state.conditions
# 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]
segment.state.conditions.freestream.altitude[:,0] = alt
# Update freestream to get speed of sound
RCAIDE.Library.Mission.Common.Update.atmosphere(segment)
a = conditions.freestream.speed_of_sound
# check for initial velocity
if mach 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])
else:# compute speed, constant with constant altitude
air_speed = mach * a
# dimensionalize time
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
v_x = np.cos(beta)*air_speed
v_y = np.sin(beta)*air_speed
# 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[:,0]
segment.state.conditions.frames.inertial.velocity_vector[:,1] = v_y[:,0]
segment.state.conditions.frames.inertial.time[:,0] = time[:,0]
