H3X, a motor company started by three University of Madison, Wisconsin graduates, promotes its integrated motor/inverter power plant as “the next step in the evolution of electric propulsion technology.” With Their HPDM-250’s 13-kilowatt-per-kilogram continuous power ability, it meets ARPA-E’s (Advanced Research Projects Agency–Energy’s) criteria for powering large, 737-type aircraft. Electronics Weekly reports, “ARPA-E has determined that for a Boeing 737 to complete a typical five hour flight, the propulsion system must be >12 kW/kg continuous.” H3X adds, “These specifications are estimates based on electromagnetic thermal and structural simulations. Data from dynamometer will be available Q2 2021.” Their motor is roughly twice as power dense as MagniX motors of similar power, according to H3X. Weight reduction is an intrinsic part of aircraft design. In the days of internal combustion engines (still very much with us), conventional wisdom held that reducing power plant weight by one pound could help take two pounds off the airframe. Even today, ICE engines generally produce only …