It is unknown whether the Hellion is in a working condition, as Calculator may have already abandoned it for some reason, for example the lack of resourses to use it. With the destruction of nuclear reactor, the Calculator loses its chance to use the craft, and the Brotherhood surprisingly ignores its existence, likely due to the war with the robots.
The game takes place in 2197 in the American Midwest. The Eastern Brotherhood of Steel is trying to claim territory surrounding Chicago. The Warrior, the player character, is a new recruit to the Brotherhood, tasked to lead a squad of soldiers made up of available initiates.