The NASA Glenn Research Center investigated, both through feasibility studies and experimental research, the possibility of using turbogenerators to produce electric power to drive electric motors to turn the propulsive fans or propellers of aircraft. Either jet fuel or hydrogen would power the turbogenerators. The demonstration of a hydrogen-powered aircraft would accomplish a NASA 21st century goal of pollution-free aircraft; and electrically driven fans or propellers offer alternative wing placements that could reduce noise, which continues to be a significant environmental problem. Conventional electric motors and their electronics are too heavy to use in these new systems and will likely require cryogenic cooling. Using superconducting coils on the rotor would eliminate the need for heavy rotor iron, and the cooling would be provided by a small cryocooler or would be available free if hydrogen fuel was stored on the airplane as a liquid.
Liquid-hydrogen-cooled, superconducting electric motor.
The superconducting alternating-current generator shown in the preceding illustration is being fabricated by Long Electromagnetics, Inc., (LEI), through NASA and U.S. Air Force contracts to serve as a testbed for evaluating superconducting and conventional materials in coil form in a realistic environment. The initial design will test second-generation bismuth strontium calcium copper oxide (Bi2Sr2CaCu2O8+δ, or BSSCO) superconducting rotor coils. Testing in coil form is important because current densities typically are reduced by an order of magnitude from wire form. The design accommodates easy replacement of the coils and windings.
Top: Glenn’s SMiRF location for LH2 testing. Bottom: SMiRF modified for aeropropulsion electric motor testing.
Glenn’s Small Multi-Purpose Research Facility (SMiRF), shown in the preceding photographs and used for general liquid hydrogen (LH2) testing, has been modified to allow LH2-cooled electric motor/generator testing. The modifications include concrete containment walls (see the bottom photograph), LH2 supply lines, and data acquisition and control. The generator test stand design (see the following figure) is complete. This work was supported by the Alternative Energy Foundation Technologies Project.
Motor test stand for LH2 testing.
Last updated: December 15, 2007
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