AAWSAP DIRD, MHD Air Breathing Propulsion and Power for Aerospace Applications, November 2010
DOW-UAP-D149 · page 13 of 32
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UNCLASSIFIED//FOA OFFl&IAk WSE 8HLV Electromagnetic thrusters use electromagnetic body forces (ExB) of Lorentz force to accelerate a propellant plasma as shown in Figure 4. 16, 17 The electric field is applied using electrodes within the thruster. The Lorentz or ExB force accelerates both positively charged ions and negatively charged electrons or negative ions in the same direction. The magnetic field can either be applied externally (applied field thruster) or generated by a very high current (typically thousands of amps) plasma discharge (self-field thruster). The current also serves to ionize the propellant. It is the interaction of the electric and magnetic fields that pushes the plasma out of the thruster at high velocity via the Lorentz force that acts mutually perpendicular to the electric and magnetic fields. Spacecraft electromagnetic thrusters are capable of processing much higher power densities (SO kW to tens of MW) and much higher thrust densities than electrostatic thrusters (hundreds to thousands of N/m2). U1n Faraday Field Orientation 0.. E ExB Figure 4. Electromagnetic Accelerator Field Configuration and Self-Field Electromagnetic Spacecraft Thrusters. Left: Illustration of the electric and magnetic field configuration. Center: Photograph of a MW-class pulsed magnetoplasmadynamic (MPD) thruster being tested at Princeton University. Right: Photograph of a 50-kW steady-state MPD thruster being tested at Princeton University. An example of an air-breathing electromagnetic accelerator system for high speed and high-altitude flight is shown in Figure 5. Air enters through the inlet on the left. The center section both accelerates the flow via electromagnetic body forces and heats the gas through Ohmic heating. The gas is then further accelerated using a diverging gas-dynamic nozzle. UNCLASSIFIED/,50B AFFIGilrAk Wlili 8HLY 9