Flight Question Air Drag Coefficient Cd - Orbiter-Forum

Philosophaie · 06-19-2012, 12:48 AM

Looking for Air Drag Coefficient, Cd, and the Surface Area, A, for the Space Shuttle, Saturn V and other rockets so I can calculate the Air Drag Force on the Shuttle.

I know the Air Density as it varies with km height. density @sea level is about 1.2kg/m^3

http://www.engineeringtoolbox.com/ai...ume-d_195.html

The equation is:

Fd = Cd * density * Velocity^2 / 2 * A

accelerationd = Fd / mass

The mass lessens as rocket fuel and hardware are used up.

RisingFury · 06-19-2012, 02:09 AM

It's not as simple as that.

For one, this equation only applies at subsonic regions, up to mach 0.8 or so. After that, the trans-sonic effects come into play. Once you cross the speed of sound, drag becomes quite different.

Second, the frontal area will change with the angle of attack, but you can get that by using one of the utilities that comes with Orbiter.

Third, coefficient of drag is a function of airspeed, angle of attack, yaw angle and a few other variables. It's not a constant.

I suggest you keep any further questions in your other thread, to spare the mods of this forum some headaches and reduce the clutter:
http://www.orbiter-forum.com/showthread.php?t=27914

I also suggest you abandon your project in the form you're doing now. You'd be better off by taking one of the existing shuttle simulations written for Orbiter. The aerodynamics of Orbiter isn't very accurate in the supersonic regime, but all of it combined is already more accurate than you will be able to do with your very limited understanding of Physics.

I suggest you look into the Orbiter API. That way you can write a program for Orbiter that allows you to extract whatever data from the simulation that you need.

06-19-2012, 12:48 AM	#1
Philosophaie Orbinaut	Air Drag Coefficient Cd Looking for Air Drag Coefficient, Cd, and the Surface Area, A, for the Space Shuttle, Saturn V and other rockets so I can calculate the Air Drag Force on the Shuttle. I know the Air Density as it varies with km height. density @sea level is about 1.2kg/m^3 http://www.engineeringtoolbox.com/ai...ume-d_195.html The equation is: Fd = Cd * density * Velocity^2 / 2 * A accelerationd = Fd / mass The mass lessens as rocket fuel and hardware are used up. Last edited by Philosophaie; 06-19-2012 at 02:06 AM.

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06-19-2012, 02:09 AM	#2
RisingFury OBSP developer	It's not as simple as that. For one, this equation only applies at subsonic regions, up to mach 0.8 or so. After that, the trans-sonic effects come into play. Once you cross the speed of sound, drag becomes quite different. Second, the frontal area will change with the angle of attack, but you can get that by using one of the utilities that comes with Orbiter. Third, coefficient of drag is a function of airspeed, angle of attack, yaw angle and a few other variables. It's not a constant. I suggest you keep any further questions in your other thread, to spare the mods of this forum some headaches and reduce the clutter: http://www.orbiter-forum.com/showthread.php?t=27914 I also suggest you abandon your project in the form you're doing now. You'd be better off by taking one of the existing shuttle simulations written for Orbiter. The aerodynamics of Orbiter isn't very accurate in the supersonic regime, but all of it combined is already more accurate than you will be able to do with your very limited understanding of Physics. I suggest you look into the Orbiter API. That way you can write a program for Orbiter that allows you to extract whatever data from the simulation that you need.