Magnetron directional amplifier space solar power beamer concept design

Current NASA studies of space solar power systems for delivery from GEO of electric power at 5.8 GHz envision use of a 500 m diameter phased array transmitting of order 2 GW to yield 1.2 GWe output to the electric grid from Earth based rectenna arrays. Phase injection-locked magnetron directional amplifiers (MDA) are one approach for the DC to RF converters on the beamer. This approach is based on earlier work by Bill Brown. The key element of the system is the proposed 5 kW output 85.5% efficient, 6 kV MDA with pyrolytic graphite thermal radiator operating at 350C. Slotted waveguide transmitting antennas are also proposed and their low-cost manufacture and multipacting breakdown margins under 25 kW/m/sup 2/ power flux density in the center of the 10 dB Gaussian tapered aperture are discussed. An average specific areal mass density goal of 35 kg/m/sup 2/ is proposed. EMC issues regarding the close-in carrier noise and harmonic levels are discussed. Grating lobe level maintenance requirements are discussed in regards to the few are minutes allowed tilt of the entire array, slightly larger are minute tilts of the individual 4 m subarrays, and maximum allowed random failures of about 2% of the subarrays.