SRC-085

Satellite Power System (SPS) Concept Development and Evaluation Program - Reference System Report, DOE/ER-0023

Published claims resting on this source

• CLM-0013 The paper that modern UK studies rely on for the beam figure calls anything below 1 kilowatt per square metre safe, with 230 watts per square metre as the typical value, and cites nothing at all to support the word safe.
• CLM-0020 The original 1978 design set the beam at 230 watts per square metre in the middle of the receiving site, about one twenty-third of that at its edge, and about one two-hundred-and-thirtieth of that at a fenced boundary further out.
• CLM-0023 In the 1978 reference design, two limits set the size of the transmitter and the receiving site: how much heat the transmitter can shed, and an upper limit on beam strength taken from studies of the ionosphere.
• CLM-0039 The 1978 report set the figure to protect radio and navigation systems from a disturbed ionosphere, called the number theoretical and untested, and said experiments were underway.
• CLM-0045 The apparent conflict between 12 and 23 was not an error. The underlying study gave a range, and the figure adopted sits near the top of it.
• CLM-0101 The 1978 contract required the researchers to report fixes if ionospheric disturbance pushed the pilot-beam phase error past 2 to 3 degrees, and a 1981 NASA report allowed 10 degrees of phase error for the whole pointing system. The requirement to hit the receiver within about 300 metres from geostationary orbit was stated in 2007, not in the 1978 design, which left that number open.
• CLM-0137 In four major space solar power studies from 1978 to 2007, none put a number on how much of the beam's energy would be lost if the beam sets up fine stripes of uneven density in the upper atmosphere; they mention the concern but do not measure or calculate it.
• CLM-0138 The original 1978 government design for beaming power down from space adds up all the expected energy losses to get 63% overall efficiency, but the list of losses does not include any allowance for the upper atmosphere scattering the beam.
• CLM-0182 When two different research teams assessed the exact same 1978 space solar power design, the older accounting method (which spreads emissions across whole economic sectors) found about 20 grams of CO2 per kWh, while a newer, more detailed method that traces actual physical processes found 5 to 6 times more - showing that the choice of carbon-accounting method and what it covers can swing a headline SBSP carbon number by a factor of five or six.
• CLM-0204 In this 1978 design, heat from the power-conversion tubes, not the RF electronics themselves, set the top limit on how much power the transmitting antenna could handle per square metre.
• CLM-0206 The heat-management equipment on the transmitting antenna alone was expected to weigh about 2,500 tonnes, roughly one-twelfth of the whole satellite's dry weight.
• CLM-0210 A 1978 US government design for a solar power satellite planned to move its power around at 40,000 volts DC because it judged that this would save weight compared with AC, but the same report lists the high-voltage DC switches and cable insulation needed to do this as still to be developed.
• CLM-0211 The 1978 design includes a small backup battery, but its only job is to keep the microwave tubes' heaters warm during the brief periods each year when the Earth blocks the sun from the satellite. It is not a battery for storing the satellite's main power output.
• CLM-0212 In the 1978 design, the equipment that moves and controls electrical power on board makes up about one fifth of the satellite's total dry weight.
• CLM-0430 Each of the 228 power converters in this old design needed a radiator bigger than a tennis court just to shed its own waste heat and stay within its operating temperature band.
• CLM-0331 Rockwell International's 1978 design study estimated the satellite would need about 93 tonnes of thruster fuel resupplied every year, a very small fraction of its roughly 30,000-tonne mass.
• CLM-0332 The 1978 design's steering system used 64 ion thrusters running on argon gas, grouped into eight clusters, to keep the satellite pointed correctly.
• CLM-0333 In one 1978 design, structure and mechanisms made up about 18% of the satellite's dry mass; a 2010 paper gives about 20% as a general rule for the main structure of aerospace systems. The two figures measure different things, so they are not two estimates of one share.
• CLM-0336 Different design studies over four decades have each simply assumed a different working lifetime for a solar power satellite, from about 15 years to 30 years; none has actually operated one long enough to know which is right.
• CLM-0337 The 1978 study expected the satellite's mirrors to lose about a fifth of their reflectivity over 30 years in space, though the same document gives two different numbers for this in two different places.
• CLM-0338 The 1978 design assumed each steering thruster would fail on average once every five years, and that its grids would wear out after about 5,000 hours (roughly seven months) of running. It carried 64 thrusters so that spares could cover failures between yearly maintenance visits.
• CLM-0533 All the rockets in the world together put about 2.7 million kilograms into orbit in 2025, about a fourteenth of the mass of one solar power satellite design from 1978 (about a thirteenth for the main 1978 reference design).
• CLM-0867 The 1978 report states a peak beam intensity, a collection efficiency and a total radiated power. Those three numbers cannot all be right together: they imply a beam about 5 to 7 per cent more sharply peaked than the antenna design described in the same report can produce.
• CLM-0868 (low confidence) The beam shape drawn in the 1978 report narrows slightly faster just outside its peak than the antenna design in the same report can produce. The gap is three to four per cent, which is small and near the limit of what a hand-drafted figure can be read to.
• CLM-0869 The 1978 reference report gives two different figures, 88 and 89 per cent, for how much of the beam lands inside the same 5 km circle on the ground.
• CLM-0870 Recomputing the 1978 design from its own stated parameters reproduces its beam, its power and its own intercept figure of 95 per cent; the 88 per cent quoted elsewhere in the same report matches a different term in another breakdown of the same losses, and on the knowledge base's arithmetic the two breakdowns agree to about 0.3 per cent.
• CLM-0871 A table in the 1978 report has two arithmetic slips, and the report's own column total is enough to show which figure is wrong in each case.
• CLM-0872 A 1978 efficiency diagram has two of its numbers in the wrong boxes, which its own intermediate figures reveal and its bottom-line total cannot.
• 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-0962 The 1978 US government reference design assumed two satellites would be finished every year for thirty years. That was a starting assumption for the cost work, not something the study worked out.
• CLM-0963 The 1978 reference design expected each satellite to take six months to build in orbit, using a crew of roughly 550 to 700 people. Two figures in the same report disagree about how many of them were in low orbit.
• CLM-0972 If you take a 1975 estimate of how fast people could build structure in space, checked against one Skylab task, and apply it to the 1978 design's framework, you get a crew of a few hundred to build it in six months, which is roughly what the design said. For the framework, the 1978 numbers add up.
• CLM-0973 Apply that same measured pace to the whole satellite rather than just its framework, and the 1978 design would have needed several thousand people, not a few hundred, to finish in six months. The design assumed something made people two to fourteen times more productive and never said what.
• 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-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-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-1092 The famous 23 milliwatts per square centimetre is measured face-on to the beam, which is how the receiving panels are tilted, and is the same number the beam carries through the upper atmosphere. Spread over flat ground at the reference site in the southern United States, where, if the satellite is due south of the site, the beam comes in at about 50 degrees above the horizon, the same beam delivers about a quarter less per square metre of ground, 17 to 18 rather than 23.
• CLM-1093 Working the 1978 antenna design forward gives 25 mW/cm2 straight down from the satellite. The report prints 23. That drop can be explained by the extra distance to a site in the southern United States, or by the report's own allowance for phase errors and failed tubes, but not by both, and each explanation alone is worth the same 7 per cent. The report's own labelling suggests the errors were included, in which case the figure at the actual site is about 21.5.
• CLM-1094 The 1978 Rice report the archive holds is the follow-on to the 1977 one that the reference system cites, and the 1977 report, obtained the same day, gives about 20 milliwatts per square centimetre with no band and no derivation. The 12 milliwatts per square centimetre figure is worked out in the 1978 report from a simple heating-versus-cooling balance, and the authors say their simplifications make the real threshold higher, not lower, and that nobody had observed the effect.
• CLM-1222 The fourth paper the 1978 design cites for its beam limit also calls the limit a theory that had not been tested. The one experiment it reports, at Arecibo in 1977, heated the upper atmosphere less strongly than the satellite would and found nothing, so it did not test the limit.
• CLM-1413 A 1977 NASA-funded report says the metal mesh behind a receiving station's antennas can be about three-quarters open to light while letting through only about half a per cent of the microwave power. The 1978 reference design used a steel mesh about that open.
• 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-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.
• CLM-1481 Worked out from the 1978 report's own figures: if the design's thousands of antenna sections fall out of step, the beam does not fill half the sky. It spreads to a patch roughly 400 km wide, and the power in it, on average, is close to the report's own figure for that case, several thousand times weaker than at the centre of the working beam.

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