How are compound colliders used?

So you can create a compound collider from having colliders on the children, but is there a way to reference it? I have a ship with a bunch of separate mesh colliders but I need to reference a single collider for my script. The script is supposed to ignore collisions between the ship and the projectile. This is what it looks like:

var range = 2000.0;

var ship : GameObject;

function Start () {

}

var particle : GameObject;

function Update () {

var direction = transform.TransformDirection(Vector3.forward);

var hit : RaycastHit;

 if (Input.GetButtonDown ("Fire1")) 

 {

     // Construct a ray from the current mouse coordinates
     var ray : Ray = Camera.main.ScreenPointToRay (Input.mousePosition);
     Physics.Raycast(ship.transform.position, ray.direction, hit, range);
    // Physics.IgnoreCollision(this.collider, transform.root.collider);
    // sphere.transform.position = hit.transform.position;
    Physics.IgnoreCollision(ship.collider, hit.collider);
     if (Physics.Raycast (ray)) 
     {
         if (hit.collider)
         { 
         Instantiate (particle, hit.point, Quaternion.FromToRotation(Vector3.up, hit.normal));
         }
         // Create a particle if hit
         //Instantiate (particle, transform.position, transform.rotation);
     }
 }

}