“A self-contained suit of advanced technology armor. Powered by a micro-fusion reactor, with enough fuel to last a hundred years.”— In-game desription
The Midwestern Brotherhood power armor, called simply power armor in the game, is a suit of armor, used by the Brotherhood of Steel. The T-51b power armor is seen only in the intro. In the game itself, it is replaced by this horned armor. A more technologically sophisticated version, the Midwestern Brotherhood advanced power armor, also exists.
The armor is a self contained suit of advanced technology armor. Powered by a micro-fusion reactor, with enough fuel to last a hundred years. Unlike leather and metal armors, which cannot be used by ghouls, both variations of power armor are suitable for ghouls.
According to the canceled Fallout d20, the Eastern Brotherhood power armor was based on a commercial variant that was available briefly before the Great War.
I would redo the sprite of the Power Armor to make it more retro. Not that there is anything technically wrong with the sprite, it's a great piece of art. It's just that it is a bit out of place in the Fallout Universe. But bear in mind that we had to design it over a year ago and Interplay approved everything we did. - Tony Oakden, producer of FOT (Freelancer interview)
Why does the Power armor look so different from previous models? - Different group of BOS, different technology. - Ed Orman (Freelancer news)