The Men Who Fell.

Two convicts, held in an orbiting detention facility above a post-apocalyptic earth, are hired by mega-corporation Hunsinger to perform a risky salvage mission down on the planet. They land, and work their way into a gigantic underground industrial complex, following a map to their ultimate destination, to retrieve and salvage... the item. Being prisoners, they are given little info, and are given credit toward early release as payment. They get more than they expected, and things go from bad to evil.