All information now available concerning fast discharge homopolar machines is only theoretical. No such machine has ever been built and existing electrical machines do not approach the extremely severe conditions required for a fast discharge machine. The Energy Storage Group at the University of Texas at Austin has designed and is in an advanced stage of building a very fast discharge experimental homopolar machine which will explore fundamental mechanical and electromagnetic limitations to discharge times. The FDX is a fully compensated, pulsed field homopolar generator with two counterrotating rotors. It will discharge in 1. 03 milliseconds when short circuited. The applied field averages 4 Tesla and the equivalent capacitance is 16.64 F. When discharged from full speed into a load having 0.275 μH inductance and 60 μQ resistance, the discharge time will increase to 3.075 milliseconds and the efficiency of the discharge will approach 80 percent. This research has been funded by the Electric Power Research Institute (EPRI), Texas Atomic Energy Research Foundation (TAERF) and the U. S. Energy Research and Development Administration (ERDA).