SRC-449

Solar Power Satellite Program Review, final proceedings of the DOE/NASA program review held April 1980, CONF-800491 / NASA-TM-84183

Published claims resting on this source

• CLM-0964 To build two of these satellites a year, about 300 tonnes of material had to arrive at the orbital construction site every day. Getting it there was over a third of the whole cost.
• CLM-0974 The 1978 reference design shows every loss between sunlight and the power grid as a chain of numbered boxes, and the boxes multiply out exactly: about 7 per cent of the sunlight hitting the satellite reaches the grid. A rival 1980 design from Rockwell does the same sum and lands within about one per cent of its own published answer.
• CLM-0975 Depending on which published assumptions you take, a satellite needs between about 2 and 6 square kilometres of solar blanket for every gigawatt it generates. Nearly all of that spread comes from how efficient the cells are; degradation and pointing each shift it by ten per cent or so, and the exact sunlight value by under one per cent.
• CLM-1089 The higher industrial band would have shrunk the receiving field to a fifth or a third of its size, at the price of a satellite that could not shed its heat, a bigger electricity bill, and a beam that rain could knock out. Every time the programme costed it the answer was the same and 2.45 GHz stayed.
• CLM-1058 The often-repeated claim that the magnetron is 188 decibels quieter than its carrier traces to a conference abstract in which the tube maker said "180 to 190" for hand-picked tubes and said his instrument could not see below that outside a 60 megahertz window.
• CLM-1059 By spring 1980 the engineers, the reviewing panel and the ionosphere experimenters were all saying the beam-intensity ceiling the whole design hung on was too cautious; the table that priced relaxing it was published then, and reprinted unchanged in the 1981 summary.
• CLM-1060 The 1980 review did not agree with itself on how much of a satellite's cost was rockets: one paper said over a third, the programme's own table said a quarter of each satellite but nearly half of the money to get to the first one, and one paper's launch rate was double everyone else's.
• CLM-1061 In one 1980 volume the satellite cost anywhere from about 2,300 to 3,800 dollars a kilowatt depending on who added what - and the programme office said in print that none of it was official. The high-side cases, as printed, ran to four or five times the base, and one of those printed values may be a total carried into the wrong row.
• CLM-1062 In 1980 the launch vehicle that everything was costed on was said by its own designers to be arbitrarily big, and they proposed a rocket a third the size that would save five billion dollars up front for a three per cent higher running cost.
• CLM-1063 In 1980 the magnetron satellite was the lightest per kilowatt on paper and the most efficient tube on the bench, the klystron was the panel's safer bet on noise and voltage, and the panel warned that every efficiency budget so far used the most optimistic number for the tube.
• CLM-1064 The best transistor anyone had measured in 1980 was 72 per cent efficient at one watt and 60 per cent at five; the satellite designs assumed 80, and were heavier than the tube designs.
• CLM-1065 By spring 1980 the programme had decided to steer the beam tube by tube, having costed the extra hundred thousand receivers at under six hundred dollars each, and had tightened the amplitude tolerance about 26-fold in power (12-fold in voltage); its own review panel would rather have closed the loop from the ground.
• CLM-1066 Bees exposed for half an hour at up to twice the beam's peak came home and hatched about as well as unexposed bees; small birds sat through the beam's peak intensity with little more than occasional open beaks, less fluffing of feathers and possibly more resting, and a preliminary estimate put the level that would kill half of resting birds in winter at about six times that intensity.
• CLM-1067 The one primate experiment that looked alarming in 1980 - over half the infants dying in the highest-exposure group - did not repeat when rerun with more animals; the reviewer of the rodent work argued that a pregnant woman might absorb far less than the rats did, but that male fertility was the harder question.
• CLM-1068 The 1979-80 heating experiments warmed the lower ionosphere's electrons by a factor of up to about two to two and a half. Theory predicted it would thin by up to half low down and thicken by up to a fifth higher up. The navigation and broadcast signals passing through showed nothing anyone could measure.
• CLM-1069 Each launch would put about ten tonnes of nitrogen dioxide into a cloud over the pad, enough to breach a one-hour air standard on a bad day but not on its own, and make a shower of rain about as acid as ordinary polluted rain; the programme's own papers disagreed whether that happened 375 or 500 times a year.
• CLM-1070 Nobody in 1980 agreed whether the ion engines' argon would be caught by the earth's magnetic field or escape: one group had most of it caught within twenty seconds, another had all but a few per cent escaping, and the third had a sixth raining back into the atmosphere.
• CLM-1071 Running the programme at full stretch was reckoned to employ about half a million people on the ground, nearly all of them in factories, with roughly a thousand in orbit at any moment.
• CLM-1072 In 1980 the radio astronomers expected to lose a twenty-degree circle of sky around the satellites and two of their bands, the spectrum managers found the beam's skirts spilling into the neighbouring broadcast band and its third harmonic into a government satellite band, and the military found the transmitter's hundred thousand tubes would together hiss over a five-hundred-kilometre radius.
• CLM-1073 A satellite flying through the beam would get a few seconds of noisy pictures and garbled data and then recover; with a hundred satellites up, one would cross a given beam about monthly; and the rectennas would have to keep fifty to a hundred and fifty kilometres from observatories, radar ranges and airports.
• CLM-1074 One set of 1980 papers said each satellite would look like Venus and sixty of them like a slim moon; the contractor who actually worked the geometry said ten times Venus, with the transmitter flashing as bright as a full moon for two minutes at the equinoxes unless the panels were tilted or roughened.
• CLM-1075 Keeping the satellite on station against sunlight pressure was reckoned at eight per cent of its mass in argon over thirty years and 34 megawatts of its power; the antenna had to stay flat to half a metre across nearly two kilometres; and the review panel said confidence in all this rested on hope rather than evidence.
• CLM-1076 In 1980 the electronics that would condition the satellite's power weighed, at the state of the art, more than the whole satellite was allowed to; the design needed them fifty times lighter, and the arrays to run at fifty times the voltage anyone had flown.
• CLM-1077 The ground station was seven million panels holding thirteen billion little antennas, costed at about two and a half billion dollars, about 1.7 million tonnes of steel and nearly seven million cubic yards of concrete, and built by three thousand people in two years.
• CLM-1078 Put on stilts in fifty metres of North Atlantic the 1980 rectenna cost fourteen times its land price; strung from cables without its ground screen it came down to about twice, and Europe had a dozen shallow patches of sea to put one in.
• CLM-1079 The one outside firm asked to audit the 1980 cost estimates found the ground-station civil works priced at a third to a fifth of what construction experience said, the solar cells three to thirty times too cheap, and the slip rings ten to twenty times, and said the whole thing assumed breakthroughs it could not count on.
• CLM-1080 On the utilities' usual accounting the 1980 satellite could not beat coal or nuclear; on Boeing's whole-life accounting, which counted forty years of fuel, it cost less than half as much; and the economists said either way it would soak up a tenth to a quarter of the country's growth capital.
• CLM-1081 The people who would have to buy the power said in 1980 that a five-gigawatt block that could vanish within minutes in the spring and autumn eclipse periods might need six gigawatts of standby, that the ground station would lose two hundred thousand diodes a year, and that American utilities were unlikely to own one until there were some ten.
• CLM-1082 Two-fifths of the lower forty-eight states were nominally open to ground stations and sixty of them could be placed near the cities they served; the gallium for one satellite was sixteen times the world's yearly output; and the ground-station dipoles would come off the line at six hundred a second.
• CLM-1083 Building and keeping sixty satellites was reckoned at fifty thousand working years in orbit, mostly at geosynchronous altitude where the radiation is worst; a preliminary estimate expected that a five-year career there might raise a worker's cancer risk by about an eighth, and nobody knew what heavy cosmic-ray ions would do to eyes.
• CLM-1084 When the programme asked the public in 1979-80, one respondent in seven wrote back; the environmental and consumer groups were mostly against, the students split, the space enthusiasts for, and most people had never heard of it.
• CLM-1085 By 1980 both contractors' satellites had grown about 2.3 to 3.5 times heavier per kilowatt than the 1974 sketch; the gallium arsenide cell assumed for 1990 was two points above the best in any laboratory, and the silicon array would lose almost a third of its output in thirty years unless it could be annealed in orbit.
• CLM-1163 Between the spring conference paper and the autumn final report, Boeing's figure for how bright a satellite would glow at night fell twelve-and-a-half-fold, from ten times Venus to about Venus, and the report does not say why; the factor is almost exactly what a 4-pi slip in the diffuse-reflection formula would give.
• CLM-1173 A 1980 European survey for offshore receiving stations looked only at the North Sea and the Channel, left the Atlantic and Mediterranean for later, and listed distance to the grid among its siting factors, though it chose the areas on its offshore factors alone. Because the beam's footprint stretches north to south at those latitudes, coasts running east to west fitted badly.
• CLM-1207 The 1980 paper that estimated how often a satellite would meet the beam used a simple picture: the beam turns with the Earth once a day, so a given satellite gets about two chances a day to cross it, and whether it does depends on where in its orbit it happens to be. The paper does not say how wide it took the beam to be, or show its sums.
• CLM-1438 The ring of geostationary orbit lies over the Earth's equator. That ring is tilted by about 23.4 degrees to the flat plane in which the Earth travels round the Sun. So for most of the year the Sun is above or below the ring, and it lines up with the ring only around the two equinoxes.
• CLM-1487 In Britain, the amount of fast back-up power kept ready depends mainly on the biggest single block of power that could be lost at once; the rules do not set it by fuel. So a space solar station would need about the same fast back-up as a gas power station whose biggest single loss is the same size. A 2 GW space plant would be a bigger single loss than the 1,800 MW Britain now plans for, if one fault could take all of it. A satellite in geostationary orbit also passes through the Earth's shadow each night for about six weeks around each spring and autumn equinox, for up to about 70 minutes. Those times can be predicted exactly, and other power stations would have to cover them.

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