Why wont this rigidbody move?

I have no idea why it isnt moving. I dont even get any errors.

 using UnityEngine;
 using System.Collections;
 
 public class RocketPropulsion : MonoBehaviour {
     public float speed; //meterspersecond
     public float burnTime;//How long is the rocket have thrust for?
     public float spinRate;//How many rotations per second
     public float velocityAtLauncherExit;//how fast does it exit the launcher
     public float accelerationInitial;
     public float accelerationFinal;
     public Rigidbody rocket;
 
     //Technical data for the rocketMotor
     void Fixedupdate(){
         Rocket ();
     }
 
     // Use this for initialization
     void Start () 
     {
         GetComponent<Rigidbody> ();
     
     }
 
     // Update is called once per frame
 
     void Rocket () 
     {
 
         rigidbody.AddForce(rocket.transform.up * speed * Time.deltaTime);//fires the rocket at the defined speed going in meters per second.
     
     }
 }