Space ship controllers not working

Hi, I am trying to do a simple controls for a space ship. My code works, but only in the X and Y axis. Can you tell me what should I add to it to make movement forward for the ship? Actually, when I press W and S key it takes object up and down, and the A/D keys moves it left and right. I am working on moving ship forward using UpArrow key. Do you have any idea?

pragma strict

var CurrentSpeed : float = 0;

var strafeSpeed : float = 0;

function Update () {

transform.Translate(Vector3.forward Time.deltaTime CurrentSpeed , Space.Self);

if(CurrentSpeed < 0) {

CurrentSpeed += 0.25 * Time.deltaTime;

} else {

CurrentSpeed -= 0.25 * Time.deltaTime;

}

if(Input.GetKey(KeyCode.W)){

CurrentSpeed += Time.deltaTime; }

if(Input.GetKey(KeyCode.S)){

CurrentSpeed -= Time.deltaTime; }

if(Input.GetKey(KeyCode.D)){

transform.Translate(-Vector3.right strafeSpeed Time.deltaTime); }

if(Input.GetKey(KeyCode.A)){

transform.Translate(-Vector3.left strafeSpeed Time.deltaTime); } }