My asteroid dont move after shoot - why?

Hello, I have two scripts - one for my beam and one for asteroid. The problem is, that after my beam shoot asteroid, the asteroid is only move up along Y axis and rotate, but not change z or x position. I thought, that if i attach a rigidbody and cofigurable joint to my asteroid, it will move properly. What I missing?

Here is my beam script

 using UnityEngine;
 using System.Collections;
 
 public class Beam : MonoBehaviour {
 
     public float beamVelocity;
     public GameObject miniExplosion;
     public GameObject go;
     
     
     
     public void Go (Vector3 shipVelocity) 
     {
     
     rigidbody.AddForce(transform.forward + shipVelocity, ForceMode.VelocityChange);
         
     }
     
     void FixedUpdate()
     {        
         rigidbody.AddForce(transform.forward * beamVelocity, ForceMode.Acceleration);
         
     }
     
     void OnTriggerEnter(Collider innyobiekt)
     {
         Asteroid ast = innyobiekt.transform.GetComponent<Asteroid>();
         if(ast != null)
         {
             ast.Hit();
             go = (GameObject)Instantiate(miniExplosion, transform.position, transform.rotation);
             Detonator det = go.GetComponent<Detonator>();
             det.size = 1;
             Destroy(this.gameObject);
             
             
         }
     }
     
 }

And here is my Asteroid script:

 using UnityEngine;
 using System.Collections;
 
 public class Asteroid : MonoBehaviour {
     
     
     public float maxAsteroidVelocity;
     public float minAsteroidVelocity;
     public AudioClip explosionSound;
     public GameObject explosionPrefab;
     GameObject go;
     
     private Vector3 velocity;
     private float asteroidHitPoints = 100;
 
     // Use this for initialization
     void Start () 
     {
     
     }
     
     // Update is called once per frame
     void FixedUpdate () 
     {
          
     }
     
     public void Hit()
     {
         asteroidHitPoints--;
         if(asteroidHitPoints <= 0)
         {
             Explode();
         }
     }
     
     public void Explode()
     {
         go = (GameObject)Instantiate(explosionPrefab, transform.position, transform.rotation);
         Detonator det = go.GetComponent<Detonator>();
         det.size = 1;
         Destroy(this.gameObject);
     }
     
 }