X-40

X-40 was a Forerunner planet. Sometime after the Human-Covenant War, the UNSC discovered the planet, and used different locations on the planet for training simulations of the SPARTAN-IVs.

Given the installation's naming and appearance, it may be an orbital reformer.

Locations

 * Conduction Refinement Facility
 * Overwatch Construction Platform
 * The Fort

List of appearances

 * Halo: Spartan Assault