Asteroid disappears for no reason

For my space shooter game I need to make some asteroids move towards the player.

I’ve created the asteroid, made it rotate and destroy on impact.

But when I add my movement script for it, it simply just disappears when testing the game.

This is my movement script:

using UnityEngine;
using System.Collections;

public class Mover : MonoBehaviour 
{
	public float speed; //public float tilføjes så værdien kan ændres i selve unity istedet for at være kodebaseret
	void Start ()
	{
		rigidbody.velocity = transform.forward * speed; //transform forward er bevægelsen langt z-aksen.
	}
}

Ignore the danish notes, please.

It might be moving off camera when Start() is called? Try logging its position to the console to see what’s happening with it, or reducing the speed.

I suspect it’s just going off screen, unless some other code is killing it. Best bet - pause the game as soon as it runs, find the object in the scene view and see where it’s gone!

Speed or wrong direction is what I have found to be the first questions to ask oneself since this is a dynamic graphics environment.
From ‘One who has lost many in play…’