Help needed moving this gameobject

I'm currently developing a game based mainly on physics. I need help moving a gameobject via an attached thruster. The thruster won't just be moving forward. I have tried moving it using a rigidbody but that messes with other functions. I would really appreciated if you could help. My current thruster script is this.

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 [RequireComponent(typeof(Rigidbody))]
 public class Thruster : MonoBehaviour {
     public float fuelEffiecent;
     public float output;
     public KeyCode thrustButton;
     bool outOfFuel;
     Rigidbody rig;
 
     void Start () {
         rig = GetComponentInParent<Rigidbody>();
     }
 
     void Update () {
         Core core = GetComponentInParent<Core> ();
         if (Input.GetKey (thrustButton) && core.fuel >= fuelEffiecent) {
             core.fuel = core.fuel - fuelEffiecent;
             rig.AddForce(Vector3.forward * output);
         }
         if (Input.GetKeyUp (thrustButton) || core.fuel < fuelEffiecent && outOfFuel == false) {
             core.speed = core.speed - output;
             outOfFuel = true;
         }
         if (Input.GetKeyUp (thrustButton)) {
             core.speed = core.speed - output;
         }
     }
 }

This is still using the rigidbody code.