VC06 Beam link and propagation
Depth of coverage
At its target depth of L3. What the depth levels mean.
What this layer covers
Link budget, diffraction and beam geometry, atmospheric effects, pointing accuracy and safety, frequency choice and beam power density
Where it ends
Ends at the receiver aperture; no hardware lives here
Deep area
This layer is studied in more depth than most. It belongs to the deep area RF conversion and phased arrays.
The beam
A power satellite in geostationary orbit, the high orbit where a satellite stays over one point on Earth, cannot focus its beam to a point. Diffraction, the natural spreading of waves, spreads it over a patch kilometres wide (CLM-0889). Every source found that gives the design figure of 230 W/m2 at the centre of the receiving site traces it to one 1978 American report (CLM-0020, CLM-0044). The 1978 report itself says heating of the ionosphere, the electrically charged upper atmosphere, may limit the beam to about this level, a theoretical threshold (CLM-0039). Accounts of why the figure was chosen disagree (CLM-0111). No experiment has been found that tests that limit at the beam's frequency (CLM-0030). On the ground, power has been beamed over 1 to 2 km: 30 kW of DC by 1976 (CLM-1097), and 1.65 kW at the peak of short pulses in a 2022 US Navy test (CLM-1125). A 2024 test from a jet did not report any delivered power (CLM-0294).
Records
295 of the 344 records tagged to this layer are published. The rest are not yet published. A record is published only after a second reader has checked it and it has passed every publication check. What the gate checks.
| Record | In plain language | Tier | Confidence |
|---|---|---|---|
| CLM-0001 | The UK government's own feasibility study describes a system beaming microwaves at about 230 watts per square metre onto the ground. | T4 | HIGH |
| CLM-0002 | The summary report says the beam is strongest at the middle of the receiving site, at about 240 watts per square metre, and argues that this makes it safe because sunlight is stronger. | T4 | HIGH |
| CLM-0004 | The author of the 2019 CASSIOPeiA paper states the beam's strongest point is about 230 watts per square metre, and says that figure was chosen because it makes the economics work. | T2 | HIGH |
| CLM-0006 | None of the five main studies mentions the international radio-frequency exposure limits, or any safety standard, or a restricted area around the receiving site. | T0 | HIGH |
| CLM-0007 | The UK study's own experts expect the beam to interfere with electronics in its path, and think it unlikely to have much effect outside the receiving site. | T4 | MED |
| CLM-0009 | For the UK reference design, averaging the limit over half an hour and over a whole body does not help, because the beam does not switch off and it is far wider than a person. | T0 | MED |
| CLM-0010 | At its strongest, the beam is around 23 times the level the international guideline sets for the general public, and around 5 times the level set for workers. | T0 | MED |
| 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. | T3 | HIGH |
| CLM-0015 | An independent Japanese authority on power beaming records the American reference design's beam strength as 23 milliwatts per square centimetre at the receiving site, which is 230 watts per square metre. | T2 | MED |
| CLM-0018 | The most recent UK government report calls 230 watts per square metre a limit to be reached because it lowers cost, and cites an earlier report by the same consultancy as the reason for using it. | T4 | HIGH |
| 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. | T3 | HIGH |
| 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. | T3 | HIGH |
| CLM-0030 | A 2026 search found no test of the effect at the frequency space solar power would use. The facilities that can heat the ionosphere work at radio frequencies a thousand times lower. | T2 | MED |
| CLM-0032 | In 2007 the international radio science union published a white paper saying that nobody had measured this heating effect from the ground at these frequencies, and only calculations existed. The 1978 figure was repeated not in that white paper but in the longer report attached to it, which is a separate document. | T4 | HIGH |
| CLM-0033 | Apart from a 1981 NASA review that found no evidence for the number and suggested a higher one, nobody was found to have revisited it, and a 2014 proposal for experiments on beam effects in the atmosphere does not appear to have gone ahead. | T5 | LOW |
| 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. | T3 | HIGH |
| CLM-0042 | The 230 watts per square metre figure applies to one frequency and one design lineage. Japanese designs at a higher frequency allow up to about eight times as much. | T0 | MED |
| CLM-0043 | The study the 1978 reference system cites put the level where the beam may start to disturb the ionosphere at about 20 milliwatts per square centimetre. A July 1978 follow-up predicted 12, give or take a factor of two, for runaway heating, and noted the beam affects the ionosphere less at the higher frequency. | T3 | MED |
| CLM-0044 | Every mention of the figure in the whole collection can be traced back to the same 1978 American report, restated at least nine times over 48 years, and no source arrives at it independently. | T0 | HIGH |
| 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. | T0 | MED |
| CLM-0047 | Heating falls with the square of frequency. In 2007 no ground-based measurement of it was available at gigahertz frequencies, and theoretical estimates at 3 gigahertz said a rise in electron temperature from 200 K to 1000 K in the E layer might occur at 500 watts per square metre. | T2 | HIGH |
| CLM-0048 | An international scientific body reviewed the proposed figures, found them ranging from 230 to 1,000 watts per square metre, and chose 300 on health grounds, with 10 at the edge of the receiving site. | T2 | HIGH |
| CLM-0054 | None of the seven ITU documents on wireless power transmission that were searched mentions what a power beam does to the ionosphere. | T0 | MED |
| CLM-0057 | There is a formula for the instability threshold. It depends on electron density cubed, electron temperature to the fourth power, and frequency cubed, and it has no single value because it assumes how far the beam travels while the instability grows. | T2 | MED |
| CLM-0058 | A 2026 modelling paper finds that a reference space solar power beam stays well below the instability thresholds at both candidate frequencies. | T5 | LOW |
| CLM-0059 | The two fields were largely the same people from the 1970s, and papers linking them were still appearing after 1991. | T2 | MED |
| CLM-0060 | In 1981 a NASA review panel said the 230 watts per square metre figure rested on an obsolete theory with no experimental support, and made resolving it the top priority. | T3 | HIGH |
| CLM-0061 | The experiments were done. They found heating two or three times stronger than normal, not the tenfold effect predicted, no irregularities forming, and effects far smaller than a solar flare produces naturally. | T3 | HIGH |
| CLM-0062 | By 1981 the theory was being revised to a steeper frequency dependence, which would raise the permitted power density. | T3 | HIGH |
| CLM-0063 | NASA suggested in 1981 that 550 to 600 watts per square metre might be reasonable, roughly two and a half times the figure still in use, and said the parameter decides the system size and has billions of dollars of cost impact. | T3 | HIGH |
| CLM-0065 | A Raytheon study eight months earlier, by the same authors as the lost memorandum, gave a critical power of 15 milliwatts per square centimetre, said irregularities were possible above 20, and gave a strong likelihood of significant disturbance above 50 to 70. | T3 | MED |
| CLM-0066 | The figure adopted in 1978 was higher than each of the lower figures in the studies it cited, though those figures were themselves uncertain by up to a factor of two. | T0 | HIGH |
| CLM-0067 | According to a 2007 international report, Japanese designs of the time chose their beam strength on cost and land grounds; the report does not give the ionosphere as the reason. | T2 | HIGH |
| CLM-0069 | The runaway threshold barely changes with atmospheric conditions. It is decided by the choice of frequency, not by the state of the atmosphere. | T0 | MED |
| CLM-0072 | The 1978 study gives 12 milliwatts per square centimetre for runaway, give or take a factor of two, and says no threshold can be set in the usual way for the self-focusing effect, though its summary repeats an earlier study's figure of 20 for it. | T3 | HIGH |
| CLM-0075 | When ESA revisited the question in 2004 it used the 1978 theory and did not cite the 1979-81 Platteville tests or NASA's 1981 revision of the figure. | T2 | HIGH |
| CLM-0076 | The 1980 programme report says the three-year programme was due to end in 1980, that the heating experiments still needed data to confirm them, and names no follow-on experiment. It offers its findings as a basis for a policy decision rather than making one. | T0 | MED |
| CLM-0079 | The 1978 paper modelled both a ground facility and a satellite case, and its 500 watts per square metre figure is a power flux for a given temperature rise, not a power rating. | T2 | MED |
| CLM-0081 | The ten-and-a-half order range assumed density and temperature vary independently. They probably do not, which means the real range is narrower. | T0 | MED |
| CLM-0082 | The formula is the right one for the conditions space solar power would create. It was written for this case, not borrowed from a different one. | T3 | HIGH |
| CLM-0083 | The formula is the right type but nobody has said how far it can be pushed, and at space solar power frequencies the wave is about 200 times the plasma frequency. The field's own 2007 review says the case is unclear. | T3 | HIGH |
| CLM-0085 | The 1978 formula does not give a threshold. It relates threshold power to the width of the plasma structures produced, so getting a single number out of it requires deciding which width matters. | T0 | HIGH |
| CLM-0087 | The biggest thing deciding this threshold is a human choice about which plasma structure size matters. The choice of radio frequency matters least. The two atmospheric terms are upper bounds, not clean figures, because they were varied independently when they are actually linked. | T0 | HIGH |
| CLM-0088 | The published abstract of the original paper states a testable condition for whether self-focusing can happen at all, and gives the growth length as 25 km in the upper ionosphere and 1 km lower down. Its formulas are set at 15 MHz and carry two factors the abstract does not explain. | T1 | HIGH |
| CLM-0089 | Self-focusing can only happen when the ionosphere is dense enough. At 2.45 GHz, with an assumed growth length of 25 km, that means roughly the denser half of modelled conditions in the upper ionosphere. In the lower ionosphere it cannot happen at all. | T0 | MED |
| CLM-0092 | Duncan's own 1980 paper says the flawed earlier calculation was Holway and Meltz's, and praises Perkins and Roble's as the first thorough one. It does not say Perkins and Roble were wrong. | T3 | MED |
| CLM-0093 | The thousand-fold disagreement between the two published versions was a lost micro prefix in the abstract I was working from. The papers agree. | T0 | HIGH |
| CLM-0095 | My earlier duty-cycle figures were percentages of a filtered subset, not of all measured conditions, but were written as though they were of all conditions. The correct all-conditions figures are 23.8 per cent and 1.5 per cent, not 38.5 and 4.9. | T0 | HIGH |
| CLM-0096 | Using mid-latitude radar measurements rather than sub-auroral ones, a 230 watt per square metre beam is over the self-focusing threshold in about 11 per cent of measured conditions at 2.45 gigahertz and about 4.5 per cent at 5.8 gigahertz, from four days of data. | T0 | MED |
| CLM-0098 | Moving to 5.8 gigahertz helps much less at the mid-latitude radar site measured (Millstone Hill) than at the high-latitude one (Sondrestrom), and by one reasonable measure it is worse there. | T0 | MED |
| 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. | T3 | MED |
| CLM-0102 | A 1979 field test found no heating effect on the two navigation systems tested, but did find cross-modulation on time-signal stations and on one AM radio station. | T3 | MED |
| CLM-0103 | Solar flares during the same campaign disturbed the same navigation signals far more than any effect that could be put down to the heater, which was too small to detect. | T3 | MED |
| CLM-0104 | A separate Japanese review worked out the same threshold from the original paper and got 32 and 425 watts per square metre. My own calculation gives 32.01 and 424.73. That is an independent check on the coefficient everything here depends on. | T2 | HIGH |
| CLM-0105 | A third party looked at the 230 watt per square metre design figure and said self-focusing may happen at 2.45 gigahertz but not at 5.8 gigahertz. | T2 | HIGH |
| CLM-0106 | Self-focusing has actually been seen in experiments, at Arecibo and at HAARP, not just calculated. | T1 | MED |
| CLM-0108 | A 2004 ESA review found that during the October 2003 solar storm, just under 20 per cent of a space solar power beam would have been absorbed before reaching the ground. In quiet conditions the loss is under 0.3 per cent. | T3 | HIGH |
| CLM-0109 | In normal conditions the ionosphere takes essentially none of the beam. In a severe solar storm it could take a little under a fifth of it. | T0 | MED |
| CLM-0111 | An authoritative 2013 review says the 230 watt per square metre figure was chosen early in the design as a cautious maximum. It does not describe it as a measured or derived limit. | T2 | HIGH |
| CLM-0112 | The same review says modern work finds about 1 kilowatt per square metre acceptable at 5.8 gigahertz, more than four times the older figure, and that commercial designs assume it. | T2 | MED |
| CLM-0113 | As of 2013 the experiment needed to check these predictions had still not been done. | T2 | HIGH |
| CLM-0114 | The Russian treatment says self-focusing is triggered by lumpiness already present in the ionosphere, not by beam power crossing a line. That lumpiness is almost always there, so in practice the threshold nearly always is met. | T2 | MED |
| CLM-0115 | The Russian and American researchers were talking to each other from at least 1974, so they are not two fully independent traditions. | T2 | HIGH |
| CLM-0116 | The Russian formulas are a different shape from the 0.43 relation, so they cannot be used to check it either way. | T0 | MED |
| CLM-0126 | The 1982 source behind the disputed 10 per cent absorption figure actually says absorption is 0.002 per cent, and never mentions solar activity at all. | T3 | HIGH |
| CLM-0128 | A 2013 review gives three references for the 1 kilowatt per square metre figure: two Japanese papers from 1995 and 1996, and a 1981 paper by Perkins and Goldman. | T2 | HIGH |
| CLM-0130 | The quiet-condition absorption figures from four sources do not disagree. One of them states an upper bound and the others sit inside it. | T5 | HIGH |
| CLM-0131 | Even the most extreme kind of sudden, lightning-caused heating of the upper atmosphere considered in this 2004 study would only block about 3% of a space solar power beam, at most. | T2 | MED |
| CLM-0132 | A 1978 NASA-funded study calculated that a beam of about 12 milliwatts per square centimetre at 2.45 GHz would be the point where the ionosphere starts heating itself out of control. | T3 | MED |
| CLM-0133 | A 2013 review paper says calculations suggest a stronger microwave beam than the usual safety limit would still be fine at a higher frequency, but the paper itself says these predictions still need to be fully checked in space experiments. | T2 | MED |
| 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. | T3 | MED |
| 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. | T3 | MED |
| CLM-0139 | Real measurements at the Arecibo Observatory in 1980, in the same physical regime relevant to space solar power beams, found electron density varying by about 2%, occasionally up to 4%, inside large patches of disturbance that formed during high-power radio heating; the authors could not say whether the heating caused them. | T3 | MED |
| CLM-0141 | A Chinese government-linked design study calculated that, outside the main beam of its proposed satellite, stray sidelobe power on the ground would fall to about 22 watts and then 7.5 watts per square metre. | T2 | MED |
| CLM-0142 | A major Chinese government-linked design paper on a specific space solar power concept does not mention the upper atmosphere at all, and does not reference any of the classic Western physics papers on beam-ionosphere interaction. | T2 | MED |
| CLM-0146 | A 1975 Soviet theory paper calculated an exact minimum radio-wave strength - about 300 millivolts per metre in daytime, ten times less at night - below which a specific kind of upper-atmosphere plasma instability simply does not start. | T2 | MED |
| CLM-0147 | A major 2007 physics review gives a different mathematical formula, with different dependence on temperature and frequency and no dependence at all on plasma density, for a related but distinct instability than the one usually used to set space solar power's safety threshold. | T2 | MED |
| CLM-0149 | A 1982 Japanese government radio-research review says the famous 230 watts-per-square-metre figure was only ever a theoretical calculation from the 1978 US design study, and had never actually been tested by 1982. | T3 | MED |
| CLM-0150 | A 1982 Japanese review notes that, at the time, the American and Soviet safety limits for microwave exposure were far apart (1000 times, by our arithmetic), and that the proposed space solar power design's own human-safety figure was ten times stricter than the US limit of that era. | T3 | MED |
| CLM-0152 | Two UK industry planning documents, from 2022 and 2025, each state a beam-intensity design figure in the 230-245 watts-per-square-metre range, but neither traces that number back to any official safety or interference standard: the 2022 report gives no source for its figure, and the 2025 report, for a system planned to launch in 2033, cites only an earlier internal Frazer-Nash report. | T4 | MED |
| CLM-0153 | A 1980 US government environmental assessment argues, without a formal calculation or test, that an aeroplane's metal body would shield passengers from most of a space solar power beam's intensity if the aircraft flew through it. | T3 | MED |
| CLM-0154 | A 2004 study using seven years of real radio-wave-absorption measurements from northern Finland found a rough mathematical relationship between geomagnetic storm strength and radio absorption, but the relationship only weakly predicts what actually happens on any given day. | T1 | MED |
| CLM-0155 | A calculation from existing UK magnetic-field data shows the UK sits just inside the zone where NOAA says a strong (G3-level or worse) geomagnetic storm's aurora becomes visible, and right on the edge of where a moderate (G2) storm's aurora would be seen. | T0 | MED |
| CLM-0157 | The published abstract of a 1981 physics paper on self-focusing gives its threshold formulas scaled to 15 MHz, about 160 times lower than the 2.45 GHz often planned for space solar power, and shows no example at gigahertz frequencies. | T2 | MED |
| CLM-0158 | Neither of the two sources read at the page, a 2004 review by Robinson and others and Gurevich (2007), states the range of conditions under which this 1981 low-frequency theory is valid at the much higher microwave frequencies space solar power plans to use; the 2004 review applies a similar formula at 2.48 and 5.8 gigahertz without stating one. | T3 | MED |
| CLM-0161 | Satellite-link observations show that natural disturbances in the upper atmosphere can make a 2.48 GHz radio signal's strength swing by close to 100%; these disturbances are worst near the equator and the poles, and Western Europe is less affected except in rare severe conditions. | T3 | MED |
| CLM-0163 | On the exact same navigation-radio circuits used to test simulated space-solar-power heating of the upper atmosphere, a single ordinary solar flare produced a signal disturbance several times larger than anything the simulated heating produced. | T3 | MED |
| CLM-0164 | Two international radio-regulation reports and a radio-science white paper on beaming power from space never mention GPS-type satellite navigation in connection with heating the upper atmosphere, and none of them gives a figure in metres for how far off such navigation could be thrown. | T2 | MED |
| CLM-0165 | A search for other, independent scientific papers that might confirm or challenge the well-known formula used to set space solar power's self-focusing safety threshold found none that actually give a comparable formula to check it against - and the papers most likely to have one could not be accessed at all. | T2 | MED |
| CLM-0166 | A 2007 physics paper builds on an earlier, different Perkins paper - not the one usually cited for space solar power's safety threshold - and points out what it says is a genuine mistake in a 1993 paper's mathematics. | T2 | MED |
| CLM-0167 | A 2002 computer simulation, done because of two Japanese space-solar-power rocket experiments, modelled a different kind of plasma instability from the "self-focusing" usually discussed, and found its growth rate scales with the beam's strength. To keep the computing time down it ran at a frequency ratio far from a real microwave beam's. | T2 | MED |
| CLM-0168 | In this 2008 Japanese review, the absorption figures of under 1% normally and up to about 10% at increased solar activity are not tied to any radio frequency, in their section or in the citation line for their source. | T2 | MED |
| CLM-0169 | The 2008 Japanese review that gives the well-known 32 and 425 watts-per-square-metre self-focusing thresholds only ever says self-focusing "might" happen at the lower frequency and is "thought" not to happen at the higher one - it never states either outcome as a settled fact. | T2 | MED |
| CLM-0294 | In December 2024 a Japanese team beamed 5.8 GHz microwaves from a business jet flying at 7,000 metres down to a receiving site about 5 kilometres below, 40 times over four flights, and the measured beam shape matched theory closely. The report gives the strength of the received signal only in decibels, and states no transmitted power, no received electrical power and no efficiency, so it shows that the beam could be formed and aimed at that range, not that any useful amount of power was delivered. | T4 | MED |
| CLM-0400 | Millstone Hill sits at almost exactly the UK's magnetic dip angle, and the UK's modelled density range fits entirely inside what Millstone Hill measured. So Millstone Hill data can be used for the UK without extrapolating across latitude, though it is not a UK measurement. | T0 | HIGH |
| CLM-0401 | A 2004 review calculated that, under some of the most extreme conditions measured during a large solar storm in October 2003, only just over four fifths of a microwave power beam would get through the ionosphere and atmosphere to the ground, against more than 99.7 per cent normally. The storm lasted more than a day, but conditions varied, so a loss that large probably (our inference) did not last throughout. The standard 1978 efficiency figures include no allowance for it. | T3 | MED |
| CLM-0405 | A 1994 Japanese article says the numbers behind its 230 figure came from a 1993 Master's thesis, which has not been found in any index searched. | T5 | MED |
| CLM-0420 | NASA's 1981 report says the experiments found nothing supporting the 23 milliwatt limit, that the measured heating was two or three times, not ten times, and that the theory was being rewritten. Its review panel called the basis obsolete and unsupported. | T3 | HIGH |
| CLM-0440 | A 2026 computer model of a gigawatt-class space solar power beam finds it would barely disturb the density of the upper atmosphere's electrically charged layer, but would locally heat one part of it (the F-region) by several thousand degrees. | T5 | LOW |
| CLM-0460 | The URSI working group's report proposes about 250 watts per square metre on bird-welfare grounds, and says the figure does not change with frequency. | T2 | HIGH |
| CLM-0461 | The ionosphere absorbs about one part in a hundred thousand of the beam. It is not a meaningful loss. | T0 | MED |
| CLM-0500 | The same formula for how much microwave power a beam can carry before it destabilises the upper atmosphere gives 425 watts per square metre at one textbook set of conditions and a typical 189 across thousands of real radar measurements. That is not two methods disagreeing; it is one method fed different starting numbers. | T2 | MED |
| CLM-0501 | A 2024 Chinese satellite design concept plans to beam down microwaves twice as strong as CASSIOPeiA's own typical figure, and its designers do not appear to have considered the upper-atmosphere stability question at all. | T2 | MED |
| CLM-0504 | None of the main CASSIOPeiA-related documents in the register mentions any named safety or exposure standard, or describes any restricted area around the receiving site, anywhere in nearly 300 pages. | T2 | HIGH |
| CLM-0511 | The first real, built, and measured version of CASSIOPeiA's beam-steering hardware converts electricity to radio power at 42%, against about 80% for the amplifier alone and 65% for the amplifier with its circulator, once every real component is counted rather than just the amplifier chip. | T2 | HIGH |
| CLM-0512 | The small prototype achieved a beam strength close to what a real system would use, but only over an area the size of a small table, using about 672 watts of radio power. | T2 | MED |
| CLM-0513 | The most credible real, flown demonstration of space-based wireless power transmission achieved milliwatts of power over centimetres inside a single small satellite, at a little over half its own predicted efficiency, and its own scientists do not attempt to say what this means for a full-scale power station. | T1 | HIGH |
| CLM-0516 | Public money funded a real piece of hardware that was built and tested, not just another report -- a rare outcome in this field -- even though what it found was not entirely flattering to the design. | T3 | MED |
| CLM-0539 | A UK consultancy, working for the European Space Agency and using the same design as its reference point, actually published a full weight breakdown -- something the original 2019 paper never did. It comes out lower than the headline claim, at about 0.70 kilowatts per kilogram rather than 1, even though it leaves out several categories of weight altogether. It also rates one of the satellite's power-conversion stages as barely more than an idea on paper, and its input notes say the lightest case for the radio equipment is an expert's judgement, not something anyone has measured or built. | T4 | MED |
| CLM-0693 | The formula used here for when a microwave beam starts to focus itself in the ionosphere has now been checked against the original 1980 paper that first published it. Every part matches: the constant, the way it scales with frequency, density and temperature, and the assumption that one correction factor is about one. | T3 | HIGH |
| CLM-0694 | The scientist who published the threshold formula says a single threshold number does not really exist. Whether the beam becomes unstable depends on the size of the ripples it is making, and as the beam gets stronger, smaller ripples start to grow too. He also warns the threshold drops very low when the beam happens to run almost along the Earth's magnetic field. | T3 | HIGH |
| CLM-0695 | The 1980 paper says the SPS beam is expected to cause the ionosphere to focus it. It backs this with radar measurements from Arecibo, made in a different heating regime from the one an SPS beam would create, showing the predicted ripple sizes actually appear, roughly a kilometre across, and that they change the local electron density by about 5 per cent. The ripples form in seconds and fade in minutes. | T3 | HIGH |
| CLM-0860 | An open-source antenna modelling package puts the first side peak of a beam in the right place, to better than three parts in ten thousand, for the one antenna layout tested. A separate finding about how strong it reports one feature to be has been withdrawn, because it reversed when the aperture was reconstructed in an equally reasonable way. | T0 | HIGH |
| CLM-0862 | Switching a power satellite to the higher of the two candidate frequencies makes the beam five and a half times more intense on the ground, not less - but only if the antenna can keep its beam actively focused on the receiver. | T0 | HIGH |
| CLM-0863 | A published figure suggesting that modelling a solar power satellite beam needs ten million million times more rays than the available software could handle turns out to describe the cost of one way of doing the sum, not the difficulty of the problem. | T0 | HIGH |
| CLM-0864 | The whole beam calculation for a gigawatt power satellite runs in fifteen seconds on one core of a laptop. | T0 | HIGH |
| CLM-0865 | For a power satellite in high orbit, the beam is almost exactly as concentrated where it passes through the ionosphere as it is at the ground, so the two figures can be compared. For a low-orbit satellite they cannot. | T0 | HIGH |
| 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. | T0 | MED |
| CLM-0868 | 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. | T0 | LOW |
| 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. | T3 | HIGH |
| 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. | T0 | MED |
| 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. | T0 | HIGH |
| 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. | T0 | HIGH |
| CLM-0889 | A beam sent from geostationary orbit cannot be focused to a small point. Diffraction sets a floor of kilometres across, and that floor is fixed once the antenna size and frequency are chosen. The only ways to make the beam more intense are a bigger antenna or more power, both of which are large and obvious. | T0 | HIGH |
| 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. | T3 | HIGH |
| 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. | T3 | HIGH |
| 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. | T3 | HIGH |
| 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. | T3 | HIGH |
| CLM-0927 | The 1978 review found an interference route the report it was reviewing never considered: the power beam bouncing off rain, hail or blown sand into a ground microwave receiver that happens to share the frequency. It calculated the result and found it far above what international rules permit as unwanted signal. It also picked out the third harmonic, at 7350 megahertz, as the one most likely to cause trouble, because it lands in a government satellite band. | T3 | MED |
| CLM-0929 | A search of the 2011 international assessment finds no power-density limit set by the ionosphere, and it mentions the ionosphere only twice in substance: once to say that tests from low orbit to the ground would be useful for understanding the beam's interaction with it, and once in a historical table of past experiments. The search used set terms and could miss a limit written in other units or other words. | T4 | MED |
| CLM-0931 | A 1989 NASA workshop records that the receiving antenna on the ground is not just a receiver - it radiates too. One contribution lists harmonic radiation as a negative feature of the current design. Another reports that on a microwave-powered aircraft, by inference the Canadian SHARP aircraft that first flew on microwave power in 1987, the receiving antenna was noisy in three different ways, and that Canadian regulators nearly stopped the test flight over interference concerns. | T3 | MED |
| CLM-0946 | A rectenna under test emitted a spurious signal. The cause was the resistor they hung on its output, not the rectenna itself, and swapping the resistor made it stop. The diode's own harmonics were measured separately and plotted. | T3 | HIGH |
| CLM-0947 | A 1982 Japanese review calculates that the ionosphere absorbs about one part in fifty thousand of a 2.45 GHz power beam - around 0.1 MW from a 5 GW beam. That is nothing to the power system. The same sentence says it is still enough to warm the E-region, especially at night. | T3 | HIGH |
| CLM-0949 | There is a standard international curve describing how quickly an antenna's stray radiation should fall away off-axis. The SPS pattern stays under that curve everywhere except at its grating lobes - the repeating spikes caused by building the antenna out of subarrays - and the report says that because of those spikes the standard curve cannot be used to describe the SPS safely. | T3 | HIGH |
| CLM-0950 | A solar power satellite in geostationary orbit cannot make its beam any tighter than its design figure, because it is too far away to focus more sharply. The same antenna in low orbit could concentrate the beam a thousand times harder, and what stops it is the air breaking down at about 45 km up rather than anything in the satellite. | T3 | HIGH |
| CLM-0951 | The usual way to stop a strong transmitter interfering with other radio users is to smear its power across a wide band. For a solar power satellite the report calculates that the smear would have to be about 3200 GHz wide to satisfy the protection limit for microwave relay links - about 32,000 times the 100 MHz band the satellite would use. The beam is strong enough to overload a relay receiver even at frequencies well away from its own. | T3 | HIGH |
| CLM-0952 | A solar power satellite would have to stay below published interference limits, and the limits differ by who is being protected. Microwave relay links get a limit per 4 kHz of bandwidth. Radio astronomy and deep space research get limits stated per hertz, which cannot be ranked directly against the relay limits. The radio astronomy and deep space limits are recommendations rather than binding rules, and the report says what protection radio astronomy really has is not clear. | T3 | MED |
| 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. | T3 | HIGH |
| 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. | T3 | HIGH |
| CLM-0977 | In 1978 Boeing worked out how the timing reference should fan out across the kilometre-wide transmitter. The choice of how many branching levels to use was tied to how big each controlled patch of antenna could be and how tightly each level had to hold its timing: bigger patches need more levels controlled down to the individual tube, and each level then gets only two degrees of timing error at the reference frequency. | T3 | HIGH |
| CLM-0978 | In 1979 Boeing wrote down where the timing errors in the transmitter would come from. Most of the allowance, about six of the seven degrees, went to the cables and waveguides carrying the reference around the structure; the electronics at each tube got about one degree each. | T3 | HIGH |
| CLM-0979 | The three designs disagreed about what the guide signal from the ground should look like. One used a pair of tones either side of the target frequency; one used exactly the transmitter's own frequency and worried about telling the two apart; and by 1979 the reference design had moved to a coded, spread-out signal, the same family of technique that satellite navigation uses. | T3 | HIGH |
| CLM-0980 | The company that designed the timing system in 1978 handled the bending of the transmitter by dividing it into groups of patches, each with its own small computer working out the correction from where the guide beam appeared to come from and where that group's elements actually were. How big a group could be depended on how much the structure bent. The report also shows how much cable length matters: two centimetres of mismatch between levels is about 58 degrees of error at 2.48 GHz but under two degrees at 70 MHz, and its remedy is to keep the cable lengths matched. | T3 | HIGH |
| CLM-0981 | Smaller patches tolerate more bending: halving the patch from 10 m to 5 m doubles the allowed tilt for the same half-per-cent loss. A separate team found that a metre of bending is close to the limit of what a pointing sensor can tell apart, and that a pointing sensor can use at most three patches while keeping within an arc-minute of error. The tilt limit was set by the Soviet exposure standard at the first grating lobe. | T3 | MED |
| CLM-0989 | The same figure, minus 160, appears in two 1970s papers meaning two different things: in one it is the noise reaching the ground, in the other it is the noise of a single tube compared with its own signal, which after adding up ninety thousand tubes and the distance to the ground comes out 27 decibels lower. Anyone quoting "minus 160" has to say which. | T3 | HIGH |
| CLM-0993 | Space Solar has won a 1.3 million pound research contract from the research agency ARIA to help solar-powered high-altitude aircraft keep flying through the winter at UK latitudes by beaming them microwave power from the ground, at 5.8 GHz, into an antenna built into the wing. The programme's goal is a few hundred watts to a small payload for a week at a time. | T5 | HIGH |
| CLM-0995 | The whole ten-kilometre satellite was designed to sway once every fourteen minutes, and the antenna was required to be at least as stiff as once every ten minutes so that ordinary control could keep it pointed to a twentieth of a degree. | T3 | HIGH |
| CLM-0997 | The designers said how flat the antenna had to stay: within about half a metre overall, with the surface elements out of true by no more than a twelfth of a degree, under sunlight, gravity and a 24 degree temperature difference across the frame. | T3 | HIGH |
| CLM-0999 | Rockwell hung a small transmitter above the antenna to give every patch the same timing reference, and each patch corrected its own received timing back to what a perfectly flat antenna would see. | T3 | HIGH |
| CLM-1001 | Besides the deliberate beam and the tubes' noise, the satellite's fifty square kilometres of warm solar array glow faintly at radio frequencies; the 1981 study put that glow at a level far below anything else and noted that the tube noise would change if magnetrons or other tubes replaced the klystrons. | T3 | HIGH |
| CLM-1003 | For a transmitter built from millions of small solid-state amplifiers instead of tubes, the 1980 study worked its noise budget down to the ground and found about 27 decibels of headroom against the limit it used; it also noted that for such a large array the second harmonic's grating lobes miss the earth altogether, so the worry moves to the third harmonic, and that a separate frequency allocation for harmonics might be needed. | T3 | HIGH |
| CLM-1004 | In 1980 the systems contractor's own table said magnetrons were about three billion times (95 dB) noisier than klystrons; a year later the same contractor was quoting the tube maker's claim that a magnetron run without its heater was quieter than a klystron, while also listing proper noise measurements as work still to be done. Anyone citing "the magnetron's noise advantage" from this period has to say whose figure it is. | T3 | HIGH |
| CLM-1011 | In 1980 the programme used two different rules to translate its low-frequency experiments to the real beam, one for heating and one for the instability. It said the rules were believed sound, and in the same document that the instability rule had never been tested. | T3 | HIGH |
| CLM-1012 | In the DOE's 1980 summary the Platteville heating tests showed no effect on the navigation and broadcast radio it listed at the beam's equivalent strength (a separate 1980 report on the trials records cross-modulation on time-signal stations and one AM station), warmed the lower ionosphere by roughly the amount theory predicted, but did not produce the density change the same theory predicted. The programme concluded 23 was safe for these systems and said bigger facilities were needed to find the ceiling. | T3 | HIGH |
| CLM-1013 | By 1980 the programme had made the upper ionosphere ripple with a heater running at what it reckoned was four to twelve times the beam's strength, and seen satellite signals flicker as a result, while a radar looking for the same ripples saw nothing. Whether any of this applied to the real beam depended on a scaling rule nobody had tested. | T3 | MED |
| CLM-1015 | The 1980 assessment expected each big orbit-transfer burn to punch a hole in the upper ionosphere the size of the continental United States, once or twice a month, with smaller daily holes from the launcher, and a permanent thinned ring around the launch latitude. It could not say what that would add up to. | T3 | MED |
| 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. | T3 | HIGH |
| 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. | T3 | HIGH |
| 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. | T3 | HIGH |
| 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. | T3 | HIGH |
| CLM-1021 | Boeing ran the timing reference down glass fibre in four stages, measured each fibre's delay by sending the signal back, and used a second tone at half the frequency to tell which cycle it was in - the same trick satellite navigation uses. Every one of the hundred thousand tubes got its own phase corrector. | T3 | HIGH |
| 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. | T3 | HIGH |
| CLM-1036 | The programme's own sizing arithmetic, with its rate of return stated: in the cases studied a bigger antenna always raised the cost, but much less if the ionospheric limit rose with it. The 152.3 in its cost formula is the capital-recovery factor for 15 per cent over thirty years. | T3 | HIGH |
| CLM-1037 | By the end of 1980 the programme office was saying in writing that its own design limit was too cautious, that fifty or sixty might be reasonable, and that the cost case depended on raising it. | T3 | HIGH |
| CLM-1043 | With the heater off and a tuning circuit on the cathode, one hand-picked oven magnetron was as quiet as the instrument could measure: about 197 decibels below its carrier per hertz of bandwidth, 50 megahertz away from the carrier. Detuning the cathode circuit cost 20 decibels; turning the heater on swamped the display. | T3 | HIGH |
| CLM-1044 | In 1980 the quiet oven magnetron was already beyond the instrument's reach: at least 155 decibels below carrier per hertz away from the carrier, quieter at low magnetic field and high current, unaffected by drive level. Close to the carrier its added phase noise was about 114 decibels down per kilohertz at 50 kilohertz. | T3 | HIGH |
| CLM-1045 | Raytheon's own numbers had the klystron just failing the interference limit at the band edge and the magnetron clearing it by 45 decibels, while conceding nobody had measured a klystron that close to its carrier and that near the carrier the klystron was slightly quieter. | T3 | HIGH |
| CLM-1046 | The number Raytheon wrote into the design table for the satellite tube was about fifty times noisier than its best laboratory reading, because it did not yet know where the noise came from; the only work on that question was Raytheon's own unfunded research. | T3 | HIGH |
| CLM-1047 | The oven magnetron's second harmonic came out about 70 decibels below its carrier, a tuned stub took another 40 off, and the antenna's own pattern was credited with 65 more, so Raytheon reckoned the whole satellite's second harmonic would arrive on the ground fifty decibels under the limit. The third, fourth and fifth were measured but never filtered, and the fifth was unexpectedly strong. | T3 | HIGH |
| CLM-1048 | A cheap oven magnetron run cold and hard converted 81.7 per cent of its DC input to microwaves, measured carefully by heating water. Raytheon's point was that theory said 94 and a lower-frequency tube already did 93, so the 2.45 GHz tube was leaving six points on the table nobody had explained. | T3 | HIGH |
| CLM-1049 | The fifty-year magnetron rests on a cathode that runs cool because the tube heats it only as much as it needs, on tube-life curves from 1950s transmitter valves, and on twelve radio-station valves that ran ten years without failing. No magnetron had been life-tested that way, and the test tubes Raytheon looked into poisoned themselves in under an hour. | T3 | MED |
| 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. | T3 | HIGH |
| 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. | T3 | HIGH |
| 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. | T3 | HIGH |
| 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. | T3 | HIGH |
| 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. | T3 | HIGH |
| 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. | T3 | HIGH |
| CLM-1086 | The number 2.45 GHz has a birthplace: a 1975 study for NASA that swept frequency from 1 to 5 GHz against cost, found a broad flat region near 2 GHz, and picked the industrial band sitting in it. The atmosphere was checked separately and found nearly transparent below 3 GHz. | T3 | HIGH |
| 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. | T3 | HIGH |
| 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. | T3 | HIGH |
| 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. | T0 | HIGH |
| 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. | T0 | MED |
| 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. | T3 | HIGH |
| CLM-1099 | Boeing's 1977 sum gave the ground receiver 85 per cent, said it was probably a little low, and drew the trade that sets a rectenna's size: spreading the power evenly across the transmitter needs the smallest transmitter but wastes the most power outside the receiver's edge, and tapering the power towards the transmitter's edge makes the transmitter bigger and wastes less. | T3 | HIGH |
| CLM-1123 | A five-metre dish and a 100 kW radar-type pulsed tube a kilometre away, bounced partly off the ground on purpose to get more power onto the receiver, then deliberately blurred so the diodes would not be burnt out: about 550 watts per square metre landing on the array, from a beam that could have delivered three times that. | T1 | HIGH |
| CLM-1127 | As flown, under two per cent of the microwave power fed to the dish came out of the receiver as electricity, because the beam had to be blurred to protect the diodes. The authors' arithmetic says a properly focused beam onto a receiver seven to twenty-two times larger would get a quarter to nearly half of it through; nobody has built that. | T1 | HIGH |
| CLM-1130 | A quick way to size a ground-to-ground beam: at the distance where the dish stops focusing, the cone holding half the power is about twice the dish's radius and the cone holding nine-tenths about four times; anything on the ground poking into the wider cone costs you power, and the usual radio-link clearance rules overstate how high you must build. | T2 | HIGH |
| CLM-1131 | They ran a radio-propagation model over a map of the actual ground and found that, aimed just right, the beam plus its reflection off the ground would land nearly twice as much power on the receiver as the direct beam alone; a perfect mirror-flat ground would give almost four times, the theoretical best. | T2 | HIGH |
| CLM-1132 | They then measured it: raising the receiver through five metres above the ground the received power jumped by about 70 per cent, close to the model's 87 per cent; the beam was as narrow as in free space side to side and a little wider up and down; and because the ground reflection varies across the receiver, they had to map the arriving power point by point rather than swing the transmitter past a fixed probe. | T1 | HIGH |
| CLM-1133 | The exposure limits the paper cites at this frequency are 10 watts per square metre for the public, 50 for workers and 100 on military sites. Their pulsed test averaged below those everywhere except right beside the dish's feed; but had the 100 kW run continuously, the 100 W/m2 zone would have skimmed within three metres of the ground for nearly four kilometres, which is why the receiver itself has to be big enough to catch the beam, and why aircraft overhead are a separate question. | T2 | HIGH |
| CLM-1134 | The field's own 2021 scorecard: the two records were both set in 1975 (30-35 kW across about a mile, and 54 per cent DC in to DC out at short range), and in the 45 years since, nobody listed has reported more than about a kilowatt of DC delivered, or more than about a fifth of the wall-plug power coming out as DC. | T2 | MED |
| CLM-1136 | The famous 1964 helicopter hung fifteen metres up for ten hours on beamed microwaves, rectified by four and a half thousand diodes; then the Air Force lost interest and the idea went to NASA. | T2 | MED |
| CLM-1137 | In 1987 a Canadian model plane with a four-and-a-half-metre wingspan flew for twenty minutes at 150 metres on nothing but a microwave beam from a dish below, 150 watts to the motor from 400 watts per square metre at the aircraft. | T2 | MED |
| CLM-1138 | A 1994 Japanese test sent five kilowatts from a three-metre dish to an eleven-square-metre rectenna 42 metres away and caught about three-quarters of the beam; what came out as DC is not stated. | T2 | MED |
| CLM-1139 | A 1995 Japanese blimp carrying a three-by-three-metre rectenna flew for four minutes at fifty metres on ten kilowatts of microwaves from two magnetrons and a dish. | T2 | MED |
| CLM-1142 | In 2015 Mitsubishi Heavy sent ten kilowatts of microwaves half a kilometre along a Kobe pier to an eight-by-eight-metre receiver, enough to light up its logo; the review gives no figure for how much came out the other end. | T2 | MED |
| CLM-1144 | In 2019 the same Japanese array put four kilowatts per square metre onto a paperback-sized rectenna under a hovering drone ten metres up, giving about 60 watts, not enough to fly it but enough to stretch the battery. | T2 | MED |
| CLM-1169 | Under the 2020 international guidelines, which keep the 1998 values, for a microwave beam at either SBSP frequency the public may be exposed to ten watts per square metre and trained workers to fifty, averaged over half an hour and over the whole body; both come from the absorbed power that raises core temperature by one degree, divided by fifty and by ten, and close in to the antenna the power-density number stops being usable at all. | T1 | HIGH |
| CLM-1170 | In the 2020 international guidelines, besides the half-hour whole-body limit there is a six-minute limit on the hottest spot on the body, 40 watts per square metre for the public and 200 for workers at these frequencies, and a rule for bursts shorter than six minutes that lets a single brief pulse carry at most about 720 joules per square metre for the public. | T1 | HIGH |
| CLM-1171 | In the 2020 international guidelines, the lower public limit exists because the public includes children, the sick and the unaware, and anyone pregnant counts as public even at work; you may show compliance by either the external field number or the absorbed-power number, and need not show both; and ICNIRP admits that its public limits between 1 and 4 GHz, which include 10 W/m2 at 2.45 GHz, can over-expose a small child by up to 40 per cent, and has chosen not to lower them. | T1 | HIGH |
| CLM-1189 | A 1990 NASA study of powering a Moon base from orbit put the satellites in circles over the Moon's equator, beaming down to a flat receiver at an equatorial base that can see a wide cone of sky. The higher the orbit, the fewer satellites it takes to keep one always in view: 30 at 90 km, 4 at about 2,500 km, 3 at about 10,600 km. | T3 | HIGH |
| CLM-1191 | The study sized its transmitting and receiving antennas with a standard beam formula, assumed about half the transmitted power would be caught on the way down, and found that above 35 GHz the antennas are small enough that they stop mattering much to the total mass, and that going beyond 100 GHz gains little. | T3 | MED |
| CLM-1193 | A 1979 study for NASA drew the pilot transmitter's beam about three-quarters of a degree wide, a few hundred kilometres across by the time it reaches the satellites, and argued that with 100 satellites spread along a sixth of the orbit only one would sit in each pilot beam; the others would see a site's pilot only through its much weaker side lobes. | T3 | MED |
| CLM-1197 | The company beams at 10 GHz and claims its beam loses nothing in space on the way down, where the other designs in its own table lose between a sixth and a half. | T4 | MED |
| CLM-1199 | On its long, looping 12-hour orbit each array hangs over one region for about 11 and a half hours, then on the next loop serves a region about halfway round the world; the company plans 16 of them. | T4 | MED |
| CLM-1200 | A 2025 UK study says Virtus Solis counts the power its receiving site catches in a way the other designs do not: on their common method, a receiver that collects only the central spot of the beam can catch at most about 84 per cent of it. | T4 | MED |
| CLM-1203 | Caltech's receiving station on the ground is a circle about 1.6 kilometres across, just large enough to catch the whole central spot of the beam. Batteries keep its output steady through the short eclipse seasons and the dips while the craft turn. | T2 | MED |
| CLM-1204 | A 1981 US government study worked out what happens when an airliner flies through the beam. Its wings would reflect some of the beam, mostly away from the cabin. It judged the passengers' exposure insignificant, because the windows are small and the plane is in the beam for under a minute. | T3 | MED |
| CLM-1205 | A 1981 US study worked out what a satellite in low orbit feels when it flies through the beam. For a craft like LANDSAT, the strongest part lasts about a second and the whole crossing about 13 seconds. In tests, one of its cameras failed completely when enough of the beam's power shone into it. The study suggested such satellites could pause commands during a crossing for now, and be redesigned later. | T3 | MED |
| 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. | T3 | MED |
| CLM-1208 | A start-up, TerraSpark, says Luxembourg is paying it, through a European Space Agency contract, to build a test that sends power without wires over 100 m on the ground, plus research on solar cells and receiving antennas for power satellites in low orbit. Only the company has said so. | T6 | MED |
| CLM-1209 | TerraSpark says it has sent power without wires across half a metre, is testing over a longer distance in the lab now, and plans a test in space in 2027 paid for privately. Only the company has said so. | T6 | MED |
| CLM-1214 | The company says its beam will be on 99.9 per cent of the time, and that a 2 million dollar development agreement with a US government energy agency (ARPA-E) supports its work. It plans a public power-beaming demonstration in March 2027 and says it expects record efficiency. None of this is independently confirmed. | T6 | LOW |
| 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. | T3 | HIGH |
| CLM-1225 | A US start-up said in late 2025 that it had beamed power from a plane to the ground, and planned an orbital test in 2028 and its first megawatt from space in 2030. | T6 | MED |
| CLM-1227 | China's state broadcaster said in 2022 that China planned a 10 kW orbital test in 2028, 10 MW by 2035 and a 2 GW commercial plant by 2050. | T5 | MED |
| CLM-1228 | A US start-up said its first power-beaming satellite would launch in October 2026 and try to send power to another spacecraft. | T6 | MED |
| CLM-1229 | A lunar lander company said in late 2025 that it would carry a power-beaming receiver to the Moon for a start-up planning orbital power missions from 2028. | T6 | MED |
| CLM-1232 | In 1978 a NASA contractor designed a satellite that would turn sunlight into an infrared laser beam and send it, by way of a mirror satellite high above the equator, to a ground station about 30 m across. The ground station would use the beam as heat to run turbines. On paper, about 5 to 6 per cent of the sunlight collected in space would reach the grid as electricity. | T3 | MED |
| CLM-1233 | The design's beam would be very intense at the receiver, about two thousand times stronger than sunlight, so the site would need a fenced zone a few hundred metres across. At the fence, the study says, the infrared light would be far below the eye-safety limit of the day. A passing jet would warm slightly, but a slow light aircraft might be harmed. | T3 | MED |
| CLM-1234 | A second NASA-funded study in 1980 imagined the standard power satellite with its microwave transmitters swapped for about twenty very large infrared lasers. On paper, about one-seventh of the electricity made on the satellite would reach the grid, a bit more on mountain sites. The receivers would again turn the beam into heat. | T3 | MED |
| CLM-1235 | Studies from around 1980 used an infrared safety limit of about one-tenth of strong sunlight for long, whole-body exposure, and ten times that for brief exposure of small areas. Meeting it meant fencing off a zone a few hundred metres across around each receiver and keeping aircraft out of the beam. | T3 | MED |
| CLM-1236 | Clouds block a laser beam far more than a microwave beam. A 1980 NASA-funded study found that over most of the United States a single laser receiver would be clouded out too often to be a dependable power station, so each beam would need two or three receivers hundreds of kilometres apart and would have to switch between them, sometimes every few hours. | T3 | MED |
| CLM-1237 | The colour of the laser light decides how much of it gets through the air. The calculations found almost no loss near 2 micrometres on a clear day, but the 10.6 micrometre carbon dioxide laser of the earlier designs would lose more than half its beam at sea level. | T3 | MED |
| CLM-1238 | In 1978 the US energy department asked whether lasers could replace the microwave beam. Its review said the lasers of the day were not good enough, mainly because they wasted too much electricity, but that they might become good enough in time. | T3 | MED |
| CLM-1239 | In 1993 US government laboratories and a satellite company planned to shine a powerful red laser from a New Mexico telescope at mirrors left on the Moon and then at a communications satellite, to see whether the satellite's solar panels would register it. The paper shows that without correcting for air turbulence almost all of the beam would miss a satellite that far away. | T3 | MED |
| CLM-1240 | In 1999 a US national laboratory sent infrared light from a bank of laser diodes across a lab room onto ordinary solar cells and got a few watts out, enough to turn a small motor. The beam was patchy and the run was cut short, so less than one per cent of the electricity put in came out at the far end. | T3 | LOW |
| CLM-1248 | By December 2025 Japan's space roadmap said hardware for a large-structure test had been handed over for a supply-ship flight, and a satellite to beam power from low orbit to the ground had been built. | T3 | HIGH |
| CLM-1249 | Japan's December 2025 space roadmap plans to launch a solar power demonstration satellite, OHISAMA, on a private Kairos rocket in the year from April 2026, to beam power from low orbit to the ground. | T3 | HIGH |
| CLM-1250 | In a 2015 ground test in Japan, a 1.8 kW microwave beam sent over 55 m delivered about a third of a kilowatt when the steering corrected a deliberate panel misalignment, and about 90 W, roughly a quarter of that, when it did not. | T5 | MED |
| CLM-1267 | ESA also wanted to know whether beaming solar power from a satellite could power Mars and Moon bases or distant probes, because Europe had no nuclear space power sources of its own and building them would be costly. | T3 | HIGH |
| CLM-1277 | A 2026 expert commentary says the 1970s studies behind the 230 watt beam limit looked only at calm conditions over mid-latitudes. In the author's view, the single limit should be replaced by one that changes with the state of the upper atmosphere. | T2 | MED |
| CLM-1278 | A 2026 expert commentary points out that the upper atmosphere would scatter a small share of a power beam, as it does a research radar's signal, but far more strongly, so it needs checking against Wi-Fi limits. Rocket tests that made the beam produce other radio signals measured them only close by, so how far those signals could travel is unknown. | T2 | MED |
| CLM-1279 | A 2026 expert commentary suggests that power-satellite and grid operators at mid-latitudes might get about an hour's notice of space storms that would weaken the beam, enough to adjust, though not ideal. | T2 | MED |
| CLM-1284 | In 1981 the US Congress's technology office said there was not enough evidence to judge the health risk of living near a power-satellite receiver for years. It expected little harm outside the site, could not rule out effects inside it, and said this research should come first. | T3 | MED |
| CLM-1285 | In 1981 the Soviet limit for workers was a thousand times stricter than the US one, and the US had no public limit at all. Congress's technology office expected US limits to tighten and said the design should be checked against that. | T3 | MED |
| CLM-1286 | The 1981 congressional assessment listed who would be exposed to the beam and how strongly. Levels ran from a ten-thousandth of a milliwatt per square centimetre for the public to about 2 watts for workers at the satellite's antenna, and it said no one could yet say what was safe for workers. | T3 | MED |
| CLM-1290 | A 1963 US aviation agency study set the safe level for an aircraft flying through a radar or radio beam at the then human exposure limit, 10 milliwatts per square centimetre, and ten times lower for aircraft carrying explosive devices. | T3 | MED |
| CLM-1291 | The 1963 study assumed an aircraft crosses a radar beam in a few seconds at most, too short to wear out its radio parts, though a switched-off radar set could still be damaged by a strong pulse. | T3 | MED |
| CLM-1296 | A 1977 paper suggested that a solar power satellite's beam, if moved to a frequency that water vapour absorbs, could heat water vapour, cloud and rain to change the weather. It took the beam at the ground to be 100 to 1000 W/m2, which is roughly half to four times the later 230 W/m2 design centre. | T1 | MED |
| CLM-1299 | The 1982 US limit was set by taking the lowest dose at which animals' trained behaviour was disrupted, about 4 W/kg, and dividing by ten. The standard admits the factor of ten was a safety margin without a quantitative justification, and one biologist dissented on that point. | T1 | HIGH |
| CLM-1300 | Pregnant rats kept almost all day in a microwave field at a fence-line level (5 W/m2, about a fiftieth of the 1978 beam centre) had more pups die in the first week and pups that developed a day late. The authors called for replication. | T3 | LOW |
| CLM-1301 | The pregnant rats absorbed about 0.4 W per kilogram, the same as the whole-body figure the 1982 US standard later used as its limit, yet the litters still showed the early deaths and delays reported in the companion paper. | T3 | LOW |
| CLM-1302 | Months of night-time exposure at about a fifth of the 1978 beam centre made rats eat and drink less, but changed nothing else that was measured. The authors argue that absorbed dose, not frequency, explains the result. | T3 | LOW |
| CLM-1303 | Hamsters kept in a field from under half to slightly above the 1978 beam-centre level for most of each day showed small brain-cell changes under the microscope in some animals. The author thought the changes would reverse but did not test that. | T3 | LOW |
| CLM-1304 | Rabbits kept for six months in a field of about 70-100 W/m2, below the 1978 beam centre, showed no tissue damage and no clear blood changes. Their immune cells responded somewhat less to one stimulant in the test tube a month later. Four animals per group is too few to settle it. | T1 | MED |
| CLM-1305 | Six months nearly round the clock in a field of about 100 W/m2 at the head did not cause cataracts or other eye changes in four rabbits. Acute cataracts in rabbits in the cited earlier work needed more than 100 mW/cm2. | T1 | MED |
| CLM-1314 | The international radio-astronomy standard says how weak a stray signal must be before it spoils a sensitive observation. In the radio-astronomy bands just above the 2.45 GHz and near the 5.8 GHz power-beam frequencies, that level is about 10^-24.7 and 10^-24.1 watts per square metre per hertz. Longer observations and satellites in geostationary orbit make it stricter still. | T2 | HIGH |
| 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. | T3 | MED |
| CLM-1320 | The radio regulator's 2026 report on beamed power now has a section on power satellites, built around a UK design, and repeats that UK and European studies found it workable. It says nothing about effects on the upper atmosphere. | T1 | MED |
| CLM-1322 | Around 1970 an author at Atomics International (North American Rockwell) reviewed Soviet research and asked why Soviet limits were up to a thousand times stricter. He found the Soviets took non-heating effects seriously, reported long-term symptoms in workers, and turned that concern into lower limits through shorter lines of communication than the US did. | T5 | LOW |
| CLM-1323 | By 1970 most western countries used a limit of 10 milliwatts per square centimetre, first chosen in 1957 for lack of better data. The Soviet Union and Poland allowed a thousand times less, because they accepted evidence of effects that do not come from heating. | T2 | MED |
| CLM-1324 | In 1981 two US officials said America still had no enforced microwave exposure standard and that its proposed limit was among the most permissive in the world. They reported the view of some that the gap with the Soviet Union came from different evidence and different readings of it, and said closer medical checks on Soviet workers may explain why Soviet studies report many mild, reversible symptoms at very low levels. | T5 | LOW |
| CLM-1325 | In 1979 American and British radiation officials worked out that the then-standard limit of 10 milliwatts per square centimetre was safe at 2.45 GHz (the frequency planned for power satellites; our context, not on the page), about nine times below the level that warms the body by 1 C (our arithmetic). They said it was too loose at much lower frequencies, where the body absorbs more. | T2 | MED |
| CLM-1326 | A 1980s US federal health review of animal studies put the onset of harm at about 2 watts absorbed per kilogram of body, mostly from heating. Below about a tenth of that it found few effects and none it judged harmful, though a cancer-promotion result at 2-3 W/kg was unconfirmed. | T3 | MED |
| CLM-1327 | In 1972 the experimental evidence put the onset of microwave cataracts at about 10 times the then US limit, for acute exposures, and found the 1-3 GHz band the most effective. Nobody had tested years of low-level exposure. | T2 | MED |
| CLM-1328 | Studies of radar and microwave workers up to 1972 found small lens changes but no clear cases of cataract below about ten times the US limit. The reviewers saw no harm at the limit but said nobody had shown that years of low-level exposure were harmless. | T2 | MED |
| CLM-1329 | A 1972 US government-funded report found that cataracts in animals needed about ten times the worker limit for an hour or more, and that the range between the limit and that level had never been properly studied in people. | T3 | MED |
| CLM-1330 | A 1964 Polish study found that workers exposed for longer to weak radio and microwave fields reported more headaches, sleep problems and similar complaints, and argued that safety limits based only on heating were too lax. | T2 | LOW |
| CLM-1332 | By the mid-1980s Western limits were set from the energy the body absorbs, with a tenfold margin below the level that upset animal behaviour. The Soviet limit for a working day stayed far lower. | T2 | MED |
| CLM-1333 | By 1986 one early long-term rat study had hinted at more tumours at the level US rules called safe, but it was unconfirmed. Eastern European reports of nerve symptoms had not been confirmed by careful studies, and experts said there was no theory to predict any non-heating effects. | T2 | LOW |
| CLM-1334 | In 1978 the US environment agency calculated that the American safety limit of the time could, at some radio frequencies, heat parts of the body far more than normal metabolism does. It found that a cautious heat-based limit would land close to the much stricter Soviet limit. | T3 | MED |
| CLM-1336 | An old reviewer's note says the US microwave limit came mainly from a heat-balance calculation for an average man, after an earlier limit ten times higher, and not from laboratory evidence of harm. | T3 | LOW |
| CLM-1338 | A 1970 experiment found that microwave cataracts in dogs needed the lens to heat up: the same repeated doses that clouded a warm eye did nothing when the eye was kept cool. | T2 | MED |
| CLM-1339 | A 1950s experiment found that 3 GHz microwaves have to be about four times stronger than infra-red heat before skin starts to hurt, because most of the microwave heat goes deeper than the nerves that sense pain. Pain began at about half a watt per square centimetre. | T1 | MED |
| CLM-1340 | In an early-1960s US Air Force study, two dogs spent thousands of hours in a microwave beam of 20 milliwatts per square centimetre and showed no clear harm, though both put on less weight than expected. Two animals are far too few to show that the level is safe. | T3 | MED |
| CLM-1341 | In a year-long experiment from the early 1960s, mice given a short daily microwave dose that warmed them by about 3 degrees lived as long as unexposed mice, but more of them showed testicular damage. A link with white-blood-cell cancers appeared in two comparisons and not in a third. | T1 | MED |
| CLM-1342 | A US mouse study, with tests run in 1957 and published in 1961 or later, found that repeated short microwave doses too weak to warm the animals still made them put on a little extra weight. The authors argued that the safety limit of the day had been picked without a sound basis. | T3 | LOW |
| CLM-1345 | A 1972 medical paper says sailors on a warship's signal bridge could stand in radar fields up to about five times the US limit of the day. Under the thinking of the time, they would still be below the level expected to harm the eye. | T5 | LOW |
| CLM-1347 | In 1972 a leading American review said microwaves were only known to harm people by heating them. It called the evidence for other effects weak, so it argued against copying the far stricter Soviet limit. | T2 | MED |
| CLM-1348 | People feel microwave warmth only at fairly high strengths: tens of milliwatts per square centimetre for a second or so on the forehead, and less if more of the body is exposed. Pain needs tens of times more. So feeling nothing does not mean a person is below the limit. | T2 | MED |
| CLM-1354 | Rats exposed most of every day for a whole pregnancy at about 200 W/m2, close to the 230 W/m2 design centre, had normal pups and normal grand-pups on the tests used. | T3 | MED |
| CLM-1358 | At and below 180 W/m2, rats warmed slightly but less than they do from being handled, and they slept through it. At 360 W/m2, they had to use emergency cooling. | T3 | MED |
| CLM-1359 | Rabbit eyes needed a local field more than six times the 230 W/m2 design centre, held for over an hour and a half, to form a cataract; repeated daily exposures at about four times the design centre did not cause one. | T3 | MED |
| CLM-1360 | Mice kept 16 hours a day for four days in fields around and above the design centre showed no sperm damage, though modest direct heating of the testes did cause it. | T3 | MED |
| CLM-1361 | The same lab that once reported microwaves made mice grow faster repeated the test properly and found no effect, and said its earlier result should not be relied on. | T1 | MED |
| CLM-1362 | Two hours a day at about 100 W/m2 warmed rats by about a degree and shifted blood counts for a while, without lasting harm on the tests used; 500 W/m2 overheated them quickly. | T1 | LOW |
| CLM-1363 | With an aircraft's own radar aimed at the cockpit, the metal front of the fuselage kept the cockpit below what the meter could detect. | T3 | MED |
| CLM-1364 | Inside a radar aircraft in flight, crew areas got under a thousandth of the old limit from the big radars; the one weak spot was a glass dome next to a radio antenna. | T3 | LOW |
| CLM-1378 | The 1981 report found online is by the same author about the same heating experiments, but it is not the 1979 memo the 1980 government report relied on. In it, the temperature figures are calculations, not measurements, so it cannot stand in for the missing measurement. | T3 | MED |
| CLM-1432 | Rockwell's chart puts a price in mass on a flatter antenna. The frame for the 1,000 m radius weighs about 85 tonnes if it may deviate by 48 cm and about 226 tonnes if only 12 cm is allowed. The 500 m frame goes from about 16 to about 30 tonnes over the same range. | T3 | MED |
| CLM-1433 | In the 1975 study, at 300 dollars a kilogram to launch and assemble, a 1 GW station cost about 1.7 to 3.5 times as much per kilowatt as a 20 GW one. The large stations were cheapest at about 1.25 to 2.25 GHz, but their curves are shallow: about 1,900 to 2,300 dollars per kilowatt across the whole band for the largest. | T3 | MED |
| CLM-1434 | With launch and assembly at a third of the price and a cheaper power source, the 1975 study's costs per kilowatt fall at every size, by about 40 per cent for 1 GW and about two thirds for 20 GW. The largest stations still sit at their cheapest between about 1.5 and 3 GHz, around 610 dollars per kilowatt for 20 GW. | T3 | MED |
| CLM-1439 | Microwaves, radio waves and visible light are the same kind of thing: electromagnetic waves. What sets them apart is the length of the wave. Light waves are less than a thousandth of a millimetre long, microwaves are from a few millimetres to about a metre long, and broadcast radio waves are longer still. | T2 | MED |
| CLM-1452 | By our rough arithmetic, the beam of the UK's full-size reference design would carry about a million times more power than the power-beaming tests checked here that have a stated power: a Chinese ground test in 2022 that sent about 2 kilowatts across 55 metres, and two figures of about a kilowatt reported in the press in 2026, one for a Japanese satellite that is planned and not shown to have flown (a Japanese space agency researcher's 2025 lecture shows the same plan) and one for another Chinese ground test. At the design's peak beam strength, such a test could cover less than ten square metres, against tens of square kilometres for the design, so none of these tests comes close to the full-size beam that the worry about disturbing the upper atmosphere concerns. No output power is stated in the documents held here for a third test, a US Air Force flight test that nothing held shows has launched. | T0 | MED |
| CLM-1454 | The 2020 international limit for public exposure, 10 watts per square metre, is about 19 to 42 times lower than the beam strengths at which one theory says the beam might start to focus itself in the upper atmosphere (42 times uses a 2008 estimate, 19 times uses measured conditions), and 23 times lower than the 230 that a 2019 CASSIOPeiA paper gives as a typical peak. Those atmospheric figures are estimates, not hard limits. A 2026 international radio report that takes CASSIOPeiA as its example says the beam can be designed to fall below the public limit at the edge of the receiving site, with a safety zone over the beam's footprint; it gives no figure for the beam's strength at that edge, and a diagram in it shows the receiving site taking 245 watts per square metre. | T3 | MED |
| CLM-1461 | A 1981 computer model predicted that a space solar power beam would make electrons in the lower ionosphere two to three times hotter and change their number by up to half, and the study found that radio measurements during ground-based heater tests in Colorado broadly matched its model, though by day the heater could not reproduce the beam's full effect at the greater heights. A 1980 US government report said measurements during the Colorado tests showed the electrons' temperature changing while the heater was on, and that calculations by the same lead author matched another researcher's figure for how far such a heater can raise it; the memo behind that figure is not held, so whether it was measured cannot be checked. | T3 | MED |
| CLM-1466 | The pilot method works out of each antenna's own measurement, not out of a plan of where the antennas should be. Each antenna times its reply from when the pilot reached it. So if one antenna has moved, its timing changes by just the right amount, and all the replies still arrive together where the pilot came from. A 1980 NASA memorandum set out the principle; it does not discuss a moved antenna, but its working covers one. | T3 | MED |
| CLM-1467 | Keeping people out of the area where the beam is strong is a plausible way for a strong beam to meet the 2020 international limit for public exposure, and international exposure guidance accepts limiting access as a way to comply. Other designs have worked this out: a 2013 Japanese review plans a no-entry area 3.5 kilometres across, and a 2007 international study sizes a 4-kilometre receiver this way. A 1977 US study set aside 204 square kilometres for one receiving site, without saying in its cost table what fixed that size, and costed buying and preparing that land. A 2026 international radio report that takes CASSIOPeiA as its example says the beam can be designed to fall below the public limit at the edge of the receiving site, with a safety zone matching the beam's footprint, about 3.5 to 6.5 by 7 to 13 kilometres in the UK. A diagram in it shows the receiving site taking 245 watts per square metre, but the report gives no figure for the beam's strength at the edge and no cost for the zone. A 2021 UK cost model for a CASSIOPeiA design includes the land for the receiving site but names no safety zone. | T4 | LOW |
| CLM-1479 | A 1981 NASA summary says that if the timing across the 1978 design's antenna were lost, its beam would spread out to the width that one of its small radiating sections makes on its own, covering a very large area. Far from the receiving site the power could rise, but the summary says it would stay well below even the strictest safety limits of the time. | T3 | MED |
| CLM-1480 | A 1981 survey for the US energy department says that a beam steered by a signal from the ground cannot form without that signal. If the signal fails, the antenna's parts fall out of step, the power spreads over half the sky, and what reaches the ground is as weak as a radio signal. The survey takes this to mean the beam could not be aimed anywhere except at the signal. | T3 | MED |
| 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. | T0 | MED |
| CLM-1482 | A 2007 report by the international radio science union, answering whether a power satellite would be safe, says government rules let a microwave oven leak up to 5 milliwatts per square centimetre, and that Japan allows 1 milliwatt per square centimetre measured 5 centimetres from the oven. | T2 | MED |
| CLM-1483 | US rules in force in October 2026 set how much a microwave oven made since late 1971 for homes, restaurants and similar places may leak: measured 5 centimetres or more from its outside, no more than 1 milliwatt per square centimetre when new, and no more than 5 at any later time. | T1 | MED |
| CLM-1485 | The patent behind the CASSIOPeiA design, both the 2018 application and the granted patent published in 2021, mentions 230 watts per square metre in passing as an ideal and safe figure while describing the design. Neither version sets out to show that the figure is safe, and neither cites any safety standard. | T3 | HIGH |