Setting ship world velocity every physics frame?

[Pixel of Life]

How do I do this? I'm trying to make the ship fly at a constant velocity in the direction it's pointed, as long as a button in a part's right click menu is enabled. Basically a warp drive/inertial damper of sorts. I've tried using the following:

bool active = false;
  
//Gui stuff for controlling the "active" variable goes here

public void OnUpdate()
{
  if(active == true)
  {
    vessel.SetWorldVelocity(new Vector3d(1.0d, 1.0d, 1.0d)); //Placeholder values for the speed
  }
}

However, instead of setting the ship's velocity like the API documentation says it will, SetWorldVelocity() adds to the ship's velocity and it just keeps accelerating forever. I don't think it's supposed to do that considering there's also a ChangeWorldVelocity() function. The ship will slowly accelerate even when I set the velocity argument to Vector3d.zero. How do I make the world velocity vector remain constant, while still being able to control pitch, roll and yaw to steer the ship?

Edit: I also tried putting the SetWorldVelocity() call in the GUI part so it's triggered whenever I hit the button in the part's right click menu, and repeatedly hitting the button adds to the velocity instead of setting it to a certain value like it should.

Edited November 7, 2017 by CaptainKorhonen

[Aelfhe1m]

Most "warp" drives don't work using the velocity methods. Instead they calculate the distance to be travelled since the last update then translate the vessels position along the forward velocity vector by that amount. (Example)

[sarbian]

Messing with the velocity directly will always lead to strange behaviors since you will fight with the orbits and FlightIntegrator.

SetWorldVelocity is one of those calls in KSP that should not be public, or even exist at all. The way it does things make me think it a a remmenant of the pre krakensbane era. 

 

If you want a constant velocity while maintaining control then write a cheat engine that provides the proper acceleration.

Edited November 7, 2017 by sarbian