SRC-111

PNL-2482: Initial Assessment of Electromagnetic Compatibility of the SPS Microwave Power Transmission System

Commissioned by US DOE. Who paid for a study is recorded because it bears on how its conclusions should be read, not because it makes them wrong.

Published claims resting on this source

• CLM-0918 The 1978 study of what a solar power satellite would do to the radio spectrum found two things. Its transmitter NOISE would exceed what radio astronomy and deep space tracking are protected against. And its HARMONICS would breach recommendations and in one case the international regulations - though for the harmonics it said it could not make the comparison properly, because that figure had no bandwidth on its scale. It was a preliminary draft.
• CLM-0919 In 1978 there was no rule allowing a solar power satellite to transmit power, and the industrial band everyone assumed it would use permits unlimited power only on the exact frequency while separately forbidding the spurious and harmonic emissions the same report expects. A ground-based industrial heater interferes to the horizon; a satellite covers half the planet.
• CLM-0920 The 1978 study says a solar power satellite cannot keep its beam entirely on the receiving station - the physics of beams forbids it - so some energy reaches everywhere the satellite can be seen from. Most equipment is partly protected by its metal case and could be made to work with care. Microwave receivers are the exception it leaves open, because a receiver is built to be sensitive to exactly what is spilling; they could be modified, but nobody had worked out at what cost or how well.
• CLM-0921 The 1978 report says the power density a solar power satellite apparently needs to make economic sense was thought to be about the same as the density at which heating starts to produce irregularities in the ionosphere. So the design was thought to sit at that threshold, not below it, and the report says understanding of the interaction was not adequate to predict the severity of all its effects.
• CLM-0959 The original 1975 calculation found the satellite's radio noise would be fine for ordinary and troposcatter radio links and a problem only for radio astronomy. The 1978 review that redrew its chart swapped the two "fine" limit lines for stricter ones and then listed troposcatter as a problem. The disagreement is over which limit to apply, not over the arithmetic.
• CLM-0960 The 1975 study found the satellite's harmonics - the multiples of its transmit frequency - would trouble radio astronomy at the second and third harmonic, would trouble ordinary radio only at the klystron's second harmonic unless a filter was added, and would be clear at the fourth. A later reading of a redrawn chart says all three harmonics exceed everything. The original does not say that.
• CLM-0961 Everything in the 1975 interference analysis is for one satellite. The study itself says that a hundred of them would raise the noise and harmonics a hundredfold - 20 decibels - and that nobody had looked at what that would mean.
• CLM-1315 The 1975 estimate of the satellite's radio noise, taken at its own frequency, is about a hundred million times above today's threshold for spoiling radio astronomy. The noise in the astronomy band itself would be lower, by an amount nobody has yet read from the 1975 study.

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