AARADCOM/DARPA Compact Homopolar Generator
If electromagnetic (EM) rail guns are to be used to propel substantial projectiles, large amounts of energy must be delivered in a fast, high-current pulse. Homopolar generators (HPGs) store megajoules (MJ) of energy in the inertia of a flywheel and then .electromagnetically convert this energy into megampere (MA) current pulses that typically have a duration between a thousandth of a second and a second. These machines appear to be the most likely power supply for military rail guns, space launchers, and other large EM propulsion schemes. However, HPGs now exist only as large prototype fixed installations. In order to serve as field power supplies, HPGs must be suitably designed for production, have reduced auxiliary requirements, and generate more power and store more energy per unit mass than the present generation of HPGs. The Center for Electromechanics at the University of Texas at Austin (CEM-UT) conducted a study comparing variolrs HPG operating schemes and machine configurations.C1] The study concludedthat R. A. Marshall's all-iron-rotating (A-I-R) concept (figure 1) in which most of the magnetic circuit is rotated, maximizing energy density, is the best HPG configuration for powering a military rail gun.