The MAS Oppenheimer is an S4 freighter converted for military use.
It participated in the first battle of Atlantica, and housed the Magnetic Assembly's nuclear-tipped missiles. Their use towards the end of the battle would stop the American Union's advance and cause the battle lines to settle in place. It would also ensure that the American Union would use similar weapons during their second assault during the Atlantica Blitz in 2325. The Oppenheimer would again be present for this battle.