Hey everyone,
I'm currently working on a lifting caspule Soyuz module.
I have Literature values that state, that the Soyuz flies with a changing trim angle of attack for different Mach numbers.
The Soyuz has a shifted CoG (Cetner of Gravity/Mass) and I set the CoP (Center of Pressure) in a way to achieve a sepcific angle of attack (currently 17,5°). For Lift/drag calculations I have 2 airfoils defined, one for vertical and one for horizontal lift, as recommended in the API Guide.
There are two troubles here though:
First: The Soyuz doesn't keep the given AoA for the whole re-entry phase. That has (from my understanding) to do with the change in the pitch moment coefficient over the range of mach numbers. The data for the pitch moment coefficient is the following:
The actual coefficient is then interpolated for the current speed and angle of attack.
Secondly: I give the initial CoP to the airfoil via the creatAirfoil2 function. And I know that I can Change Airfoils via the EditAirfoil function. However, to me, that seems to be one time action (to use for example for separation or damage to structure that "contains" an airfoil). I want to update the CoP with every time step though.
So, my questions are:
1. Is Setting up the CoP for the airfoils the right/best way to achieve a trimmed angle of attack != 0?
2. Is my assumption that the AoA changes due to the changing pitch moment coefficient correct?
3. How do I update the CoP with every time step? Can I put the EditAirfoil function in the clbkPostStep to have it as part of the update loop? Are there better/easier options?
Thanks in advance for your time and effort
PS: I'm an aerospace engineering student, so I do have basic knowledge of aerodynamics and space stuff
I'm currently working on a lifting caspule Soyuz module.
I have Literature values that state, that the Soyuz flies with a changing trim angle of attack for different Mach numbers.
The Soyuz has a shifted CoG (Cetner of Gravity/Mass) and I set the CoP (Center of Pressure) in a way to achieve a sepcific angle of attack (currently 17,5°). For Lift/drag calculations I have 2 airfoils defined, one for vertical and one for horizontal lift, as recommended in the API Guide.
There are two troubles here though:
First: The Soyuz doesn't keep the given AoA for the whole re-entry phase. That has (from my understanding) to do with the change in the pitch moment coefficient over the range of mach numbers. The data for the pitch moment coefficient is the following:
Code:
/* Pitch Moment Coefficient
for |aoa| = { 0, 5, 10, 15, 20, 25, 30 } deg
and for all reference mach numbers. */
const double aero_cm[6][7] = {
/* |aoa| 0 5 10 15 20 25 30 deg*/
{ -0.0300, -0.0200, -0.0100, +0.0035, +0.0153, +0.0247, +0.0318 }, // Ma = 0.60
{ -0.0359, -0.0241, -0.0141, -0.0059, +0.0012, +0.00711, +0.0094 }, // Ma = 0.95
{ -0.0388, -0.0282, -0.0188, -0.0094, -0.0012, +0.0053, +0.0082 }, // Ma = 1.10
{ -0.0447, -0.0400, -0.0300, -0.0176, -0.0041, +0.0082, +0.0112 }, // Ma = 1.78
{ -0.0500, -0.0412, -0.0300, -0.0176, -0.0041, +0.0082, +0.0112 }, // Ma = 2.52
{ -0.0535, -0.0435, -0.0329, -0.0224, -0.0118, +0.0000, +0.0100 } // Ma = 5.96
};
The actual coefficient is then interpolated for the current speed and angle of attack.
Secondly: I give the initial CoP to the airfoil via the creatAirfoil2 function. And I know that I can Change Airfoils via the EditAirfoil function. However, to me, that seems to be one time action (to use for example for separation or damage to structure that "contains" an airfoil). I want to update the CoP with every time step though.
So, my questions are:
1. Is Setting up the CoP for the airfoils the right/best way to achieve a trimmed angle of attack != 0?
2. Is my assumption that the AoA changes due to the changing pitch moment coefficient correct?
3. How do I update the CoP with every time step? Can I put the EditAirfoil function in the clbkPostStep to have it as part of the update loop? Are there better/easier options?
Thanks in advance for your time and effort
PS: I'm an aerospace engineering student, so I do have basic knowledge of aerodynamics and space stuff