Wave Drag Function source?

[missleman01]

Howdy all. In trying to develop a reentry planner for Project Mercury, I am in need of many physical properties from orbiter.

One of the last ones I do not have is the wave drag computation in orbiter. I have been through the Project Mercury source, found the function calls, and then looked in the Orbiter source included in the SDK. I have found what looks like a class definition, but no logic for it.

Can anyone, perhaps Martins, help me and show me where I might find the wave drag computation code, or show me what equations are used to compute it?

If you could I would appreciate it.

 

[martins]

Orbiter doesn't try to do anything clever when calculating lift and drag forces. It simply takes the lift and drag coefficients it obtains from the callback function defined during the instantiation of the airfoil, and multiplies them with dynamic pressure and wing area. This directly gives the magnitude of the lift and drag vectors.

There are helper functions for induced and wave drag computations that the addon programmer can use in the body of the callback function (but isn't forced to do so). The algorithm of the wave drag computation used by oapiGetWaveDrag is described in the API reference manual. It is a simple piecewise polynomial function of Mach number, with some user-defined parameters. But again, orbiter doesn't know what parameters were used by a particular vessel, or even if oapiGetWaveDrag was called at all. The vessel addon programmers have complete freedom to substitute their own drag calculations.

 

[missleman01]

Alright. Thanks Martins. Based on that it would seem that I need to look more in the Merc 5.0 source. I just dont think i saw any user supplied logic for the wave drag call.

Ill keep poking around.

Thanks