Power beaming for space-based electricity on earth: Near-term experiments with radars, lasers and satellites

Power beaming experiments thus far have been done over distances close enough where receiver apertures approximately the same diameter as transmitters can capture most of the beam (the "nearfield"). The best experimentally verified wireless power transmission DC-to-DC efficiencies are 54% for a microwave transmission measured over a short distance; the longest range wireless power transmission stands at 1.6 km in 1975 (Brown, 1998; Dickinson, 1975, 2002). The next logical step is longer-range, "far-field" power beaming, particularly Space-to-Earth, or its reciprocal, Earth-to-Space, to validate beam propagation models and establish a solid experimental basis for power transmission through the atmosphere. To minimize costs, we propose adapting ground-based microwave transmitters designed for radio astronomy (Arecibo), planetary communications (NASA Deep Space Network) and detection (USAF Space Surveillance Network) for Earth-to-Space beaming tests. The receiving end could, in principle, be an NRO satellite antenna reportedly orbiting today and/or rectennas unfurled by the International Space Station (ISS). Laser SSP has lower transmission efficiency; but smaller, more flexible, and potentially cheaper components make it worth exploring. Lasers require smaller components because diffraction effects are less at optical than at microwave wavelengths The Air Force Maui Optical Station (AMOS), with facilities for accurately firing lasers through ground-based telescopes with adaptive optics at targets in space, appears ideal for laser beaming tests in conjunction with orbiting PV arrays targets. Platforms like the ISS and/or GEO communication satellites may likewise have (or could easily have) lightweight PV arrays capable of converting light to DC for end-to-end power efficiency tests. If successful, these experiments might be followed with impressive demonstrations of SSP technology such as illumination of lamps visible from Earth's surface on orbiting satellites, or lighting up homes or schools in small towns and villages using modest amounts of power beamed from Space. The proposed tests offer cost-effective and credibility-building steps to evolving space power prior to SSP satellites and space infrastructure constructed from scratch (NASA Mankins, NRC, 2001).