Modeling of MHD power generation on board reentry vehicles

The possibility of MHD power generation on board of reentry vehicles is theoretically explored. The focus is on the ability to extract large amounts of electric power, at least several hundred kilowatts from square meter of the surface. Estimates of electrical conductivity in unseeded and alkali-seeded air and MHD performance, taking into account Hall and ion slip effects, are followed by the development of a coupled model of nonequilibrium hypersonic flow with MHD effects and power extraction. Simulations indicate that, with modest (∼1%) amount of alkali seed and modest values of magnetic field (0.1-0.2 Tesla), it should be possible to extract substantial amounts electric power, from several hundred kilowatts to a few megawatts per square meter of the surface, from a 3-5 cm thick boundary layer at altitudes of 45-60 km and flight velocities of 6-7 km/s. One possible use of the extracted power would be to heat the flow upstream of the vehicle in order to reduce the drag. In the non-optimized example case, the drag was reduced and the L/D ratio increased by 15%, and the reduction in drag power was 41.5 times the power extracted from the boundary layer and added upstream of the nose. Further exploration of this use of MHD-generated power could potentially result in significant enhancement of L/D of reentry vehicles. Additionally, controlled off-axis power deposition can be expected to result in considerable aerodynamic lifting or turning moments.