From Halopedia, the Halo wiki
The Exodus Project was an Insurrectionist plan to convert an asteroid of the Rubble into a mobile habitat. Initially, Habitat Exodus was to be used as an emergency in-system retreat, to ferry one million civilians into the Oort cloud on the edges of the 23 Librae system in the event of a Covenant return. The plan was later altered, calling for the Habitat to be outfitted with Shaw-Fujikawa Translight Engines which would allow it to travel far away from UNSC or Covenant space. The Exodus project is especially noteworthy for being the only major secret in the democratic Rubble settlement.
From the start, the largest rock in the Rubble was set aside and coated for stealth. The project did not reach its ultimate objective because an insufficient number of Slipspace Drives were installed to make the desired jump. Instead, the Exodus ferried the refugees of the Rubble to the 18 Scorpii system, where they were evacuated to the UNSC colony Falaknuma when the asteroid disintegrated due to slipspace resonance-induced friction.
List of appearances