C#: Why the rotation and moving of spaceship are conflict when I was using C#

Help
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1

Godot Version

4.2.2

Question

Recently I was learning how to programming Godot 3D game in C#.
I plan to let the player’s spaceship (rigid body 3D) move forward and tilt a little bit when it turn left or right. However, it looks conflict, when I using the function rotate the z axis according to the Input.x, but the spaceship can not move. On the contrary condition, it can not rotate.
Thank you very much for your help

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public partial class SpaceShip : RigidBody3D
{
private float speedX = 50.0f;
public Godot.Vector3 directionX = Godot.Vector3.Zero;

public override void _Ready()
{
}


// Called every frame. 'delta' is the elapsed time since the previous frame.
public override void _Process(double delta)
{
	float input_x = Input.GetActionStrength("ui_right") - Input.GetActionStrength("ui_left");
	float input_z = Input.GetActionStrength("ui_down") - Input.GetActionStrength("ui_up");
	directionX = new Godot.Vector3(input_x, 0f, input_z);
	directionX = directionX.Normalized();
	
	float targetTilt = input_x * 10f;
	float currentTilt = RotationDegrees.Z;
	float tiltSpeed = 5f;
	float newTilt = Mathf.Lerp(currentTilt, targetTilt, tiltSpeed * (float)delta);

	GD.Print(directionX);

	ApplyMovement(directionX);
	RollFlyDegree(newTilt);
}


private void RollFlyDegree(float side)
{
Vector3 RotationDegreesTemp = RotationDegrees;
RotationDegreesTemp.Z = side;
RotationDegrees = RotationDegreesTemp;
}

private void ApplyMovement(Godot.Vector3 dir){
	Godot.Vector3 force = dir * speedX;
	float deltaTime = (float)GetProcessDeltaTime();
	GD.Print(force);
	ApplyImpulse(force * deltaTime);
}

}

Blockquote