Planetary Gravity and improper orbits

Hey everyone! I have started working on creating orbits in unity using planetary gravity. using UnityEngine; using System.Collections;

 public class PlanetaryGravity : MonoBehaviour {
 
     GameObject planet;
 
     // Use this for initialization
     void Start () {
         planet = GameObject.FindGameObjectWithTag("Planet");      
     }
     
     // Update is called once per frame
     void FixedUpdate () {    
         GetComponent<Rigidbody>().AddForce(((planet.transform.position - transform.position).normalized)  * 364500.487f, ForceMode.Acceleration);
     }
 }

this is put on my satellite. I also have another script that does this

 GetComponent<Rigidbody>().velocity = (new Vector3(0,0,7676f));

this should, in theory put the satellite in an elliptical orbit around the center object, tagged planet. Instead it does this.

https://www.youtube.com/watch?v=LZRmQA3qRbM&feature=youtu.be

It makes this strange pattern that makes me think that the orbital path is rotating around the center as the object orbits. Any idea what may be causing this?