AERODYNAMICS
By José Pablo Luna Sánchez. 2008
Spacecraft3.dll can handle the following control surfaces:
Each surface need the following properties to be defined.
Do not worry about the apparently mysterious nature of each parameter.
This first part is about concepts.
- Angle of Attack (AoA)
Angle of incidence. The angle between the longitudinal line of the fuselage and the chord line.- Lift coefficient (CL)
It determines the magnitude of the force that keeps the airplane flying- Moment Coefficient (CM)
Moment could be understood as the torque that tries to align the airfoil with the direction of motion.
Airfoil efficiency = wing span ^ 2 / wing area
Now you may wonder how to calculate those esoteric numbers.
With this tutorial you will find a tool called VLM.EXE
Click HERE so you find out how to obtain and understand some of those numbers.
Here is a table that shows what data you need for every control surface.
ATTACK |
CHORD |
AREA |
ASPECT |
LIFT |
EFFICIENCY |
DRAG |
CD0 |
ANIM |
|
VAIRFOIL | x |
x |
x |
x |
x |
x |
x |
x |
- |
HAIRFOIL | x |
x |
x |
x |
x |
x |
x |
x |
- |
ELEVATOR | x |
- |
x |
- |
x |
- |
- |
- |
x |
RUDDER | x |
- |
x |
- |
x |
- |
- |
- |
x |
AILERON | x |
- |
x |
- |
x |
- |
- |
- |
x |
ELEVATOR TRIM | x |
- |
x |
- |
x |
- |
- |
- |
x |
RUDDER TRIM | x |
- |
x |
- |
x |
- |
- |
- |
x |
FLAPS | - |
- |
x |
- |
x |
- |
- |
- |
x |
SPEEDBRAKE | x |
- |
- |
- |
- |
- |
x |
- |
x |
For vertical and horizontal airfoil, drag data required is wave drag.
For flaps, drag refers to the maximum drag when fully deployed.
Aileron animation must be composed by two sequences, one for left aileron and another for right aileron.
Example:
[AERODYNAMICS]
VAIRFOIL_ATTACK=(0,0,-0.2)
VAIRFOIL_CHORD=5
VAIRFOIL_AREA=90
VAIRFOIL_LIFT=4
VAIRFOIL_ASPECT=1.5
HAIRFOIL_ATTACK=(0,0,-4)
HAIRFOIL_CHORD=2
HAIRFOIL_AREA=15
VAIRFOIL_LIFT=2
HAIRFOIL_ASPECT=1.5
AILERON_ATTACK=(7.5,0,-7.2)
AILERON_AREA=0.2
AILERON_LIFT=1.5
AILERON_RIGHT_ANIM=9
AILERON_LEFT_ANIM=8
ELEVATOR_AREA=1.2
ELEVATOR_LIFT=1.5
ELEVATOR_ATTACK=(0,0,-7.2)
RUDDER_AREA=0.8
RUDDER_LIFT=1.5
RUDDER_ATTACK=(0,0,-7.2)
RUDDER_ANIM=6
SPEEDBRAKE_DRAG=4
SPEEDBRAKE_ATTACK=(0,0,-8)
SPEEDBRAKE_ANIM=10
There is still some room for exploring here.
You may have questions, and probably you may need to experiment a bit and share what you learn at the forums.
Aerodynamics is uncharted territory for many addon makers.
So your contribution in this arena could be very valuable.
REFERENCE
If you would like to learn more about aerodynamics, visit these sites
XFOIL
Subsonic Airfoil Development System (free software tool)
http://web.mit.edu/drela/Public/web/xfoil/
Airfoil Design
http://www.aerospaceweb.org/question/airfoils/q0035.shtml
Ask a Rocket Scientist Archive
Site with many interesting topics on aeronautics
http://www.aerospaceweb.org/question/list.shtml
Aerodynamics for students
http://www.ae.su.oz.au/aero/contents.html
NASA - Welcome to The Beginner's Guide to Aeronautics
http://www.grc.nasa.gov/WWW/K-12/aerosim/
Vortex Lattice Method (3-D)
For developers with some knowledge on aerodynamics (free software tool)
http://www.ae.su.oz.au/aero/vlm/vlm.html