substantial development in the next few years, but we feel that this development is warranted given the possible benefits of 35 GHz and phased array technologies to space solar power. The satellite can also carry scientific payload as warranted. This system transmits 150 kW and can supply between 30 kW and 60 kW on the ground. However, the extremely low power flux density, which is less than one-thousandth the activation energy of the rectenna, requires the use of concentrating tracking dishes prior to rectification on the ground. But these concentrators are fixed and limit the time the rectenna can receive energy to less than 6 seconds. If a tracking system is installed on the ground to circumvent this problem, not only is the need for a phased array antenna eliminated, but more power will be needed on ground to perform satellite tracking than can be delivered to the satellite. This limits the purpose of the demonstration to technological and scientific purposes only, and at US $800 Million it becomes a very expensive research tool, which actually doesn't even perform very much science since by atmospheric standards 150 kW is a paltry amount of power. Therefore the idea of sending this little power at so much cost seems seriously flawed. More specifically, our analysis revealed that the mission concept of transmitting space solar power to Antarctica is also problematic. We find that even in an absolute best case scenario, where the amount and price of kilowatt-hours are maximized, only on the order of a few hundred million dollars can be collected from a single base over a ten year period, even though the cost of building and launching such a system will be on the order of a few billions of dollars. Therefore, we strongly recommend against a US $800 Million demonstration to beam power to Antarctica, since all that will be demonstrated is the ability to eventually lose billions of dollars. Furthermore, we also suggest that a space to Earth demonstration at the level of US $800 Million not be attempted at all, since the low power densities extremely limit the scope and hence the value of such a demonstration. Instead, we propose alternative ways that our client might better spend its money. The first is to fund research and development into more powerful transmitters and more sensitive rectennae that will help to make demonstrations of this scale more worthwhile. Secondly, finance a more varied assortment of space to space demonstrations at the US $80 Million level. A third option involves potentially even cheaper Earth to space experiments. A proposal for one such experiment is detailed below. Earth to Space The basic plan of this very near-term and very cheap (less than US $5 Million) design example is to use existing facilities to conduct a trans-atmospheric power beaming test. The technologies demonstrated would be high-power beaming through the atmosphere at long distances, power reception using rectennae in the space environment, degradation of said rectennae with long exposure to radiation and other space environmental factors, and deployment of large inflatable reflectors. Measurements would be taken of spatial and frequency dispersion effects, side-lobes, rectenna efficiency, and power reception as a function of both weather and position within the beam. Power would be transmitted from the 305 m diameter Arecibo dish at two frequencies. Power levels would be 400 kW from the 2.38 GHz transmitter and 2 MW from the 430 MHz transmitter. Power would be received in a satellite at about 780 km altitude sun-synchronous orbit and would be on the order of 60 W for the 2.38 GHz transmitter. This power would only be received for a short time (1/1 Oth to 1/2 of a second) and might be used to power a flash to illuminate a logo on the reflector for a picture to be transmitted back to Earth, along with the recorded scientific measurements. The receiving satellite will weigh about 100 kg, and we propose that it be launched on two positions of the European ASAP ring. A 10-m diameter inflatable reflector will be used to concentrate the incident microwaves onto a small rectenna at the focus about 12 m away (see Figure 7). The craft will be gravity-gradient stabilized. Total program costs are estimated to be under $5 million, with launch within 5 years and mission duration of about 2 years, for 120 measurements. Further consideration should be given to the possibilities of either using a large military radar system, for which data was not available, or conducting a larger experiment using a dedicated Pegasus (or other system) launch to put a 100 m diameter receiver capable of receiving kilowatts into a higher orbit. By comparing the amount of technical information they produce to their expense, it can be seen that ground to space demonstrations like this one are extremely practical,. For example, almost as much scientific information can be learned in ground to space experiments as can be gathered in space to ground demonstrations. In addition to ground to space demos, it may also be wise to pursue ground to ground applications of beamed technology. Given the large potential market for relayed power,
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