SDK Question Why GetForceVector does not give the sum of the relevant forces during flight?

[fred18]

Hi guys,

very simple.

I just noticed that during flight (so no ground contact) if I sum the 4 force vectors (thrust, weight, lift and drag) and I compare it to the force I have from GetForceVector I get a difference along Z of around 50kN constant. This happens only if I apply thrust to my vessel, while it is almost 0 in all other circumstances. It happens at all the altitudes (so no atmo effect is involved) and also with complex flight and all the perturbations disabled.

Does anybody have an idea of why this happens? 50kN is not huge but still I don't understand why there is such a difference when thrust is applied.

Thanks!
Fred

 

[Face]

I just noticed that during flight (so no ground contact) if I sum the 4 force vectors (thrust, weight, lift and drag) and I compare it to the force I have from GetForceVector I get a difference along Z of around 50kN constant. This happens only if I apply thrust to my vessel, while it is almost 0 in all other circumstances. It happens at all the altitudes (so no atmo effect is involved) and also with complex flight and all the perturbations disabled.

Does anybody have an idea of why this happens? 50kN is not huge but still I don't understand why there is such a difference when thrust is applied.

(emphasis mine)

On return, F contains the sum of all forces acting on the vessel.
This may not be equal to the sum of weight, thrust, lift and drag vectors, because it also includes surface contact forces, user-defined forces and any other forces.

Perhaps the vessel code is doing some AddForce there?

 

[fred18]

(emphasis mine)


Perhaps the vessel code is doing some AddForce there?

nope, I made the test with a "clean" vessel which, apart from loading the physical part at the beginning, just print out the result in prestep

Anyway it was N not kN, sorry, I wrote it wrongly. still on all the circumstances it's 0.000 or 0.001 with thrust applied is 50...