SRC-554

Satellite Power System Concept Development and Evaluation Program, Volume II, System Definition; NASA TM-58236; July 1981

Commissioned by National Aeronautics and Space Administration, Lyndon B. Johnson Space Center; in-house report, no contract number printed. 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-0911 If the steering signal from the ground stops, the 1978 design's beam does not carry on pointing somewhere. It falls apart, and the power on the ground drops by a factor of about eight thousand, to below the Soviet guideline plotted in the report. The size of that drop turns out to match the number of independently steered pieces the antenna has, which suggests the same arithmetic could give a rough estimate for other designs.
• CLM-1017 By 1981 the programme itself said the ionospheric limit it had designed to was probably too cautious, and worked out what relaxing it to more than double would be worth: nearly twice the power from a slightly larger antenna, at a third of the cost penalty.
• CLM-1018 Three years of study left the efficiency chain exactly where 1978 put it, and Boeing's own version says out loud the solar constant the 1978 figure only implied.
• CLM-1019 The programme gave three reasons for choosing the klystron; the company that designed the satellite said the choice was more or less arbitrary and the magnetron might be better. The 85 per cent tube efficiency that every cost chain uses is the contractor's estimate.
• CLM-1020 By 1981 the programme was confident the beam could be pointed and formed, and named the network that carries the timing reference across the transmitter as the part it was least sure of, with the choice between cable, fibre and a broadcast reference still open.
• CLM-1022 A loss you can make up by adding solar panels costs about 56 million dollars per percentage point; a loss at the ionospheric ceiling costs eleven times that, because there is no more beam to give. That is why the ionospheric limit matters economically, and it is the first price on the timing-error budget.
• CLM-1087 When the programme wrote down why it used 2.45 GHz, its reasons were consistent: each time it named the industrial band and how the beam passes through the atmosphere, and some documents added rain, good efficiency, antenna size or the outlook for the equipment.
• CLM-1091 The people running the programme said 2.45 GHz was sensible and also said, in the same breath, that nobody international had agreed to it and the choice was open. Their own account of the 1979 world radio conference is that no frequency was given and one might be, if the environmental case were made.
• CLM-1478 Almost everything that can go wrong with this design makes the beam fall apart and become harmless, which is the right way to fail. Two things do not. If someone fakes the ground signal, the satellite aims at the fake. And if the internal reference cabling drifts, the beam weakens and wanders rather than switching off.

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