The asteroids that made up the Rubble were mined and constructed by a mix of Kig-Yar and Humans. The Humans that lived on the Rubble were either Insurrectionists, sympathizers, or surviving colonists from the UNSC world Madrigal. The habitats were made up of many asteroids that were linked together with docking tubes. Each of these asteroids had its own means of propulsion, and they were kept together by the machinations and calculations of the "smart" A.I. Juliana. She had been operating far past her normal 7 year life span and was approaching rampancy, but she had to remain in operation because the tasks that she performed were too difficult for humans.