API Question Understanding of CreateAirfoil and Airfoils themselves

[birdman]

Hello you guys,

I'm trying to implement the lift of a rotationally symmetric blunt reentry vehicle, with a shifted CoG.
It should be possible to flatten or steepen the flight route by rotating the vessel, thereby changing the position of the CoG and creating or reducing lift, depending on the CoG position and the direction the roll angle is applied.

The CoP is positioned aft the CoG and lies in the symmetry axis of the vessel.


In the API_Guide it is recommended to use at least two airfoils (LIFT_HORIZONTAL and LIFT_VERTICAL).

At the moment I positioned them both in the CoP and use the same aerodynamic parameters for both airfoils.
Probably not the best idea, or is it possible it could work out as I expect it to?
(unspecified question, but maybe it comes clear what I want to achieve over the next lines).

What I'm trying to understand right now is the look/physical appearance of the airfoils, when created.

1. Question:
Do they match the shape of the mesh, or do I have to imagine the shape more like a plane wing. And the LIFT_VERTICAL airfoil and LIFT_Horizontal airfoil are standing orthogonal on each other.
If it's not understandable, what I mean, I can provide some drawings if it would help.

2. Question
Do the airfoils interact?
Could it be possible that I produce more lift with just one airfoil in comparison with a second simulation run, with the exact same flight path and a second airfoil?

3. Question
If my CoG would be in the axis of symmetry. I would need to have a lifting force which is the same for every roll angle.
Is this achievable with two airfoils?

4. Question
Is this the best way to accomplish this?

Thank you very much in advance =)

Have a nice weekend
birdman

 

[martins]

1. Question:
Do they match the shape of the mesh, or do I have to imagine the shape more like a plane wing. And the LIFT_VERTICAL airfoil and LIFT_Horizontal airfoil are standing orthogonal on each other.
If it's not understandable, what I mean, I can provide some drawings if it would help.

The mesh doesn't influence the physics engine in any way. This includes the aerodynamics. It's up to you to provide airfoil definitions that make sense given the physical appearance of the vessel. The "airfoil" concept is derived from winged bodies, but can be applied to general aerodynamic interactions for lifting bodies. The LIFT_VERTICAL and LIFT_HORIZONTAL airfoils are orthogonal to each other.

2. Question
Do the airfoils interact?
Could it be possible that I produce more lift with just one airfoil in comparison with a second simulation run, with the exact same flight path and a second airfoil?

Orbiter calculates the airfoil-induced forces independently from each other. However there can be an indirect interaction between airfoils (e.g. one airfoil induces a rotation which changes the lift and drag forces of the other airfoils). Take for example a normal aircraft with wings and horizontal stabilisers in the tail. Generating negative lift in the tail by using the elevators will increase the AOA and thus increase (positive) lift in the main wings.

3. Question
If my CoG would be in the axis of symmetry. I would need to have a lifting force which is the same for every roll angle.
Is this achievable with two airfoils?

Yes, this should be possible with a VERTICAL and HORIZONTAL airfoil. Their lift and drag functions should be identical, and the functions themselves should also be symmetric about the AOA=0 angle, and they should have the same attack point at the CoP.

4. Question
Is this the best way to accomplish this?

Yes.

 

[birdman]

Thank you again, that helped a lot to understand the functionality of the airfoil.