Moving a Rocket problems

I am trying to get a rocket to move upwards(later it may move in other directions also) when I press the space bar. Right now it doesn't move at all. The rocket is going to be used to move an object as far as possible and then eventually get to the end goal such as Flight and Toss the Turtle as some random examples only mine will be in 3d. Here is my code.

var launchPower : float = 1.0;
var rocketFuel : int = 100;
var buttonPressed : boolean = false;

function Update ()
{
    if(Input.GetButton("Jump")) // Finds if your pressing the spacebar
    {
        buttonPressed = true;// If you are set buttonPressed to true
    }
    else
    {
        buttonPressed = false;// If not set to false
    }

    if(rocketFuel > 0 && buttonPressed == true)// If you have rocketfuel and are pressing the spacebar
    {
        rocketFuel -= Time.deltaTime;// Use rocketfuel
        constantForce.force = Vector3(0,-launchPower,0);// Move the rocket. This isn't working because the rocket doesn't move upwards
    }

    Debug.Log("Velocity is "+rigidbody.velocity);
    Debug.Log("Rocketfuel is "+rocketFuel);

}

Do you have a ConstantForce attached? I don't understand why you'd use that. Aside from that, the problem with movement could be that your default launch power value is too low to escape gravity.

Also, rocketFuel should be a float. Round it if you want for display. I don't see why you need to Log rocketFuel. You can watch it in the Inspector.

var fuelUse : float;    // per second.
var launchPower : float = 50;
var rocketFuel : float = 100;
var buttonPressed = false;

function FixedUpdate () {
    buttonPressed = Input.GetButton("Jump");

    if (rocketFuel > 0 && buttonPressed) {
        rocketFuel = Mathf.Max(rocketFuel - fuelUse * Time.deltaTime, 0);
        rigidbody.AddForce(Vector3(0, launchPower, 0));
    }

    Debug.Log("Velocity is "+ rigidbody.velocity);
}

And if that's all you need buttonPressed for, I'd get rid of it. I also never set up default values in code.

var rocketFuel : float;
var fuelUse : float;    // per second.
var launchPower : float;

function FixedUpdate () {
    if (rocketFuel > 0 && Input.GetButton("Jump")) {
        rocketFuel = Mathf.Max(rocketFuel - fuelUse * Time.deltaTime, 0);
        rigidbody.AddForce(Vector3(0, launchPower, 0));
    }

    Debug.Log("Velocity is "+ rigidbody.velocity);
}