Short flight test of control system with a low altitude auto rotation. The thrust drive system converts thrust generated utilizing a jet engine, ducted fan, or propeller into useful rotor shaft torque needed to power helicopter rotor blades.

Testing responsiveness of power system. The electric propulsion system in this prototype demonstrated great performance at both low and high power settings. Later testing with ducted fans showed further improvement in efficiency compared to propellers. Larger versions can utilize electric or turbojet engines to generate the required thrust. Existing battery energy density only offers a fraction of the range that can be provided by jet or hydrogen fuels. In a hybrid configuration both electric and gas engines can be combined or substituted completely with hydrogen fuel for a completely zero-emissions helicopter. Another advantage is hydrogen’s energy density. Diesel fuel used in our turbine engine has an energy density of 45.5 megajoules per kilogram (MJ/kg), slightly lower than gasoline, which has an energy density of 45.8 MJ/kg. By contrast, hydrogen has an energy density of approximately 120 MJ/kg, almost three times more than diesel or gasoline. In electrical terms, the energy density of hydrogen is equal to 33.6 kWh of usable energy per kg, versus diesel which only holds about 12–14 kWh per kg. What this really means is that 1 kg of hydrogen, used in a fuel cell to power an electric motor, contains approximately the same energy as a gallon of diesel. Hydrogen used in fuel cells has the energy to weight ratio ten times greater than lithium-ion batteries. Consequently, it offers much greater range while being lighter and occupying smaller volumes.

Prototype test flight with more aggressive power curve settings and high altitude autorotation. The thrust drive system converts thrust generated utilizing a jet engine, ducted fan, or propeller into useful rotor shaft torque needed to power helicopter rotor blades

During this flight we were looking for any negative flight performance impact from adding additional weight to the aircraft including any noticeable vortex ring state issues which none were observed. The thrust drive system converts thrust generated utilizing a jet engine, ducted fan, or propeller into useful rotor shaft torque needed to power helicopter rotor blades

Test run of the power system with 40 lbs thrust turbojet delivering 37 lbs of thrust at tube outlet. 37 lbs of thrust applied 10 feet out from the rotor shaft equates to 370 ft/lbs of shaft torque delivered per engine. This particular engine weighs only 3.2 lbs. Larger engines demonstrate even greater power to weight ratios.