[@Willy Vereb]
This seems acceptable =)

[@Lauder]
May I inquire to the purpose? If the purpose is for your homeworld to be unconquerable (is that a word?) then I think you would need something greater than that =) That said, it's in the ballpark. If you want only exactly what you described thus far, then as long as it has some mechanism on how to fire all around the planet, I don't see a problem with it.