V. Program Design Examples Space to Space Part of our assignment was to investigate a space to space demonstration that could be completed within five years and cost less than US $80 Million. The near-term demonstration we propose is to beam microwave power from the Mir space station to the unmanned servicing spacecraft Progress. Keeping logistics as its primary mission, Progress will carry the hardware for the beaming experiment (phased array antenna, rectenna, structures, control equipment, etc.) to the Mir space station. While Progress is docked to Mir, the rectenna will be deployed automatically and the antenna will be installed on Mir by a cosmonaut EVA. The beaming experiment will then be carried out after separation of Progress from Mir (see Figure 4, located at the end of Section VI). The mission will cover a variety of technical and scientific objectives such as demonstrating the functionality of a phased array in space, target acquisition, and beam control. This will be an important step towards possible larger scale application of space solar power systems. Beaming power to Progress could demonstrate the feasibility of a future free-flying high quality microgravity laboratory without solar arrays in the vicinity of a space station. Finally the associated plasma diagnostics could give important scientific information on plasma composition, plasma energy dispersion, plasma waves, and microwave-plasma interactions. This design example proposes an antenna and rectenna size both equal to 2m x 2m, a beaming distance of about 80 m, and a frequency of 2.45 GHz. With this configuration the overall DC to DC transmission efficiency would be better than 3.7 %, with the antenna transmitting 5 kW and the rectenna receiving 186 W of usable power on the Progress vehicle. Scheduling and costing analysis show that the demonstration project is feasible within 3 years and a total budget of approximately US $78M. Projects like this are extremely useful to a general program for space solar power, because they produce valuable data at reasonable costs. Other space to space examples that we considered, though not to the same level of detail, included a Space Station Freedom to Space Shuttle demonstration, which would be of particular use in ascertaining the difficulty of maintaining beam control on large space structures, and a Mir to Shuttle demonstration, which, aside from its technical worth, could be of great public relations value. Space to Earth We were also assigned the task of investigating a space to Earth demonstration, achievable in ten years, and budgeted for no more than US $800 Million. We decided that this second design example should be a demonstration of the ability to provide power from space to remote sites on Earth. Specifically, the concept originated as a plan to provide power to remote scientific research sites in Antarctica. The current cost of power for these sites is higher here than for anywhere else on Earth since fairly inefficient diesel generators are used which require fuel flown in by cargo aircraft at great expense. Non-financial considerations of this mission include measuring the environmental impact of small-scale space solar power with scientific instruments already in place in Antarctica and with Earth Observing Satellites that monitor atmospheric conditions over Antarctica. Since there is already a basis for international cooperation, a need for an environmentally more benign energy source, and a moderate power demand which might be economically achievable by space solar power in the foreseeable future, this mid-term project seemed reasonable to undertake. The time and cost constraints are major drivers of the satellite design. The relatively short time frame precludes the inclusion of revolutionary technological breakthroughs into the design of the satellite. In addition, the cost allocation quickly leads to the conclusion that a simple and straightforward system shall be built for the baseline system. This means one automatic satellite of limited size, deployment by a single launcher (no manned or robotic assembly in space), and placement into low Earth orbit for purposes of power maximization. The frequency of 35 GHz was chosen instead of 2.45 GHz for reasons of power maximization as well. The envisaged baseline system includes one 10 ton satellite deployed in a 1000 km, sun-synchronous orbit, with a period of 6h-18h local hours, beaming over a 1 km2 rectenna. As can be seen in Figure 5, the satellite makes use of a foldable 1000 m2 solar array and a 100 m2 phased array antenna operating at 35 GHz. A 35 GHz phased array of this size does not yet exist and would require
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