bullet.js

var speed : float = 10.0;

function Update () {
    transform.position += speed * Time.deltaTime;
}
function OnTriggerEnter(other:Collider){
    if(other.gameObject.tag == "Asteroid"){
        Debug.Log("hit");
        Destroy(other.gameObject);
        } else if (other.gameObject.tag == "cube"){
        Destroy(this.gameObject);
    }
}