// Update is called once per frame
 void Update()
 {
     if (Input.GetKeyDown(KeyCode.Space))
     {
         // toggle the engine
         if (rocketEngine.engineOn)
         {
             rocketEngine.SetEngine(false);
             ge.BodyOnRails(shipNbody, centerNbody);
         }
         else
         {
             rocketEngine.SetEngine(true);
             Vector3d vel = ge.GetVelocityDoubleV3(shipNbody);
             rocketEngine.SetThrustAxis(vel.ToVector3().normalized);
             ge.BodyOffRails(shipNbody, ge.GetPositionDoubleV3(shipNbody), vel);
         }
     }
 }