Rocket Explosive Force

Hi, I am using a rocket launcher script which fires this rocket prefabs, which have this script attached :

 // The reference to the explosion prefab
 var explosion : GameObject;
 var timeOut = 3.0;
 var radius = 5.0;
 var power = 10.0;
 
 // Kill the rocket after a while automatically
 function Start () {
     Invoke("Kill", timeOut);
      // Applies an explosion force to all nearby rigidbodies
     var explosionPos : Vector3 = transform.position;
     var colliders : Collider[] = Physics.OverlapSphere (explosionPos, radius);
     
     for (var hit : Collider in colliders) {
         if (!hit)
             continue;
         
         if (hit.rigidbody)
             hit.rigidbody.AddExplosionForce(power, explosionPos, radius, 3.0);
     }
 }
 
 
 function OnCollisionEnter (collision : Collision) {
     // Instantiate explosion at the impact point and rotate the explosion
     // so that the y-axis faces along the surface normal
     var contact : ContactPoint = collision.contacts[0];
     var rotation = Quaternion.FromToRotation(Vector3.up, contact.normal);
     Instantiate (explosion, contact.point, rotation);
 
     // And kill our selves
     Kill ();    
 }
 
 function Kill () {
     // Stop emitting particles in any children
     var emitter : ParticleEmitter= GetComponentInChildren(ParticleEmitter);
     if (emitter)
         emitter.emit = false;
 
     // Detach children - We do this to detach the trail rendererer which should be set up to auto destruct
     transform.DetachChildren();
         
     // Destroy the projectile
     Destroy(gameObject);
 }
 
 
 @script RequireComponent (Rigidbody)

But when they hit another rigidbody it doesn't gets any effect from the rocket, any idea why?