var projectile : Rigidbody;
var speed = 20;
function Update ()
{
    if(Input.GetButtonDown("Fire1"))
    {
        var instatiatedProjectile : Rigidbody = Instantiate(
            projectile, transform.position, transform.rotation);

        instatiatedProjectile.velocity =
            transform.TransformDirection(Vector3(0,0,speed));

        Physics.IgnoreCollision( instantiatedProjectile.collider,
            transform.root.collider );
    }
}