Source code for RCAIDE.Library.Mission.Segments.Ground.Takeoff
# RCAIDE/Library/Missions/Segments/Ground/Takeoff.py
#
#
# Created: Jul 2023, M. Clarke
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# IMPORT
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# RCAIDE Imports
import numpy as np
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# unpack unknowns
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[docs]
def initialize_conditions(segment):
"""
Initializes conditions for aircraft takeoff ground roll
Parameters
----------
segment : Segment
The mission segment being analyzed
- altitude : float
Ground altitude [m]
- velocity_start : float
Initial ground speed [m/s]
- velocity_end : float
Rotation speed [m/s]
- ground_incline : float
Runway incline angle [rad]
- friction_coefficient : float
Ground friction coefficient [-]
- state:
numerics:
dimensionless:
control_points : array
Discretization points [-]
conditions : Data
State conditions container
unknowns:
ground_velocity : array
Ground velocity profile [m/s]
initials : Data, optional
Initial conditions from previous segment
- analyses:
weights:
vehicle:
mass_properties:
takeoff : float
Aircraft takeoff mass [kg]
Returns
-------
None
Updates segment conditions directly:
- conditions.frames.inertial.velocity_vector [m/s]
- conditions.ground.incline [rad]
- conditions.ground.friction_coefficient [-]
- conditions.freestream.altitude [m]
- conditions.frames.inertial.position_vector [m]
- conditions.weights.total_mass [kg]
Notes
-----
This function sets up the initial conditions for a ground takeoff segment with
acceleration from initial speed to rotation speed. The segment handles ground
effects, friction, and incline during the takeoff roll.
**Calculation Process**
1. Check initial conditions
2. Initialize velocity profile:
v = v0 + (vf - v0)*t where:
- v0 is initial speed
- vf is rotation speed
- t is normalized time/distance
3. Set ground conditions:
- Friction coefficient
- Ground incline
4. Set position and altitude
5. Set aircraft mass
**Major Assumptions**
* Constant friction coefficient
* Constant ground incline
* Linear velocity increase
* Quasi-steady acceleration
* Small minimum velocity for numerical stability
See Also
--------
RCAIDE.Framework.Mission.Segments
"""
# use the common initialization # unpack inputs
alt = segment.altitude
v0 = segment.velocity_start
vf = segment.velocity_end
# 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]
if v0 is None:
v0 = np.linalg.norm(segment.state.initials.conditions.frames.inertial.velocity_vector[-1])
# avoid having zero velocity since aero and propulsion models need non-zero Reynolds number
if v0 == 0.0: v0 = 0.01
if vf == 0.0: vf = 0.01
# intial and final speed cannot be the same
if v0 == vf:
vf = vf + 0.01
# repack
segment.air_speed_start = v0
segment.air_speed_end = vf
initialized_velocity = (vf - v0)*segment.state.numerics.dimensionless.control_points + v0
# Initialize the x velocity unknowns to speed convergence:
segment.state.unknowns.ground_velocity = initialized_velocity[1:,0]
# pack conditions
conditions = segment.state.conditions
conditions.frames.inertial.velocity_vector[:,0] = initialized_velocity[:,0]
conditions.ground.incline[:,0] = segment.ground_incline
conditions.ground.friction_coefficient[:,0] = segment.friction_coefficient
conditions.freestream.altitude[:,0] = alt
conditions.frames.inertial.position_vector[:,2] = -alt
conditions.weights.total_mass[:,0] = segment.analyses.aerodynamics.vehicle.mass_properties.takeoff
conditions.frames.inertial.position_vector[:,:] = conditions.frames.inertial.position_vector[0,:][None,:][:,:]
