Applying Force problem

I was using:

float thrust = Input.GetAxis("Vertical") * MainThrust;

To control the spaceship. Problem is that this code allows me to apply force into opposite direction with a equal amount of force.

So I decided to modify the code and let the force “UP”(y-axis) to be 100% of “MainThrust” and “Down” (y-axis) 20% of the “MainThrust”

Here is my current code: (I am getting a compiler error even though I commented the codes that I think its causing the problems)

using UnityEngine;
using System.Collections;

public class LMPhysicsScript : MonoBehaviour 
{
	public float EnterySpeed = 10;
	public float MainThrust = 20F;
	public float RollThrust = 1F;
	
	void Start () 
	{
		rigidbody.velocity = new Vector3 (EnterySpeed,0,0);
	}
	
	void Update () 
	{
		//float thrust = rigidbody.AddForce(Vector3.up * MainThrust);
		float rot = Input.GetAxis("Horizontal") * RollThrust;
		
		rigidbody.AddForce(transform.up * thrust);
		rigidbody.AddTorque(0,0,-rot);
		
		Debug.Log (thrust);
		
	}
}

//		float thrust = Input.GetAxis("Vertical") * MainThrust;
//		float rot = Input.GetAxis("Horizontal") * RollThrust;
		
//		rigidbody.AddForce(transform.up * thrust);
//		rigidbody.AddTorque(0,0,-rot);
		
//		Debug.Log (thrust);

At the very bottom outside the public class I have commented the code that worked.

you’ve commented out thrust and are trying to access it
//float thrust = rigidbody.AddForce(Vector3.up * MainThrust);

check line 20
rigidbody.AddForce(transform.up * thrust);

it tries to access a undeclared variable “thrust”;

I decided to stick with my old code for now.
Thank you for answering anyways!