Determining glide ratio/angle

[I_Killed_Jeb]

Hi all, recently as I've been designing some new spaceplanes to play around with, it occurred to me that their gliding ability, specifically the glide angle and flight speed, can probably be determined before the fact.

To me, due to the relatively simple aerodynamic model in KSP, it seems that you could very reasonably determine the glide ratio and speed based on lift number (as given by the part info in the SPH/VAB) and mass. Has anyone tried doing the math on this?

[NathanKell]

Nope. Glide ratio is the L/D ratio, and that depends very heavily on craft geometry; you need to find the glide angle that minimizes drag while maximizing lift. If all you know is wing area and mass, that tells you nothing about L/D and optimum glide angle.

[I_Killed_Jeb]

1 hour ago, NathanKell said:

Nope. Glide ratio is the L/D ratio, and that depends very heavily on craft geometry; you need to find the glide angle that minimizes drag while maximizing lift. If all you know is wing area and mass, that tells you nothing about L/D and optimum glide angle.

Considering KSP is agnostic to things like sweep angle I don't see why this couldn't be excellently approximated with a simplified formula, especially since most spaceplanes designs are by their nature low drag.

[NathanKell]

That's...really not how it works. Shape has a gigantic influence on drag, and non-wing drag will tend to be rather higher than wing drag, so your wing might have a higher L/D at one angle whereas your craft in total will have a higher L/D at another. Trying to make that kind of drag-from-mass estimate is exactly what KSP's old aero did, to cataclysmic effect.

[MaxL_1023]

FAR  (Ferram Aerospace Research) will tell you your L/D ratio in real time, but as it also changes aerodynamics around your values would probably be (at least slightly) different in stock.