Value chain · CLM-1059
In plain terms
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.
The claim as recorded
The programme said in April 1980, not first in December 1980 or 1981, that its 23 mW/cm2 ionospheric limit was probably too low, and it is the April 1980 JSC paper that costs the alternative: "The present ionospheric limit of 23 mw/cm2 is probably too low and should be raised after the ionospheric heating tests and studies are completed. For SPS cost considerations, it is very important to ascertain the true upper limit", with a table at 2.45 GHz of antenna diameter 1.36 km, rectenna DC grid power 2.76 GW, rectenna diameter 7.6 km, relative rectenna area 56 per cent, electricity cost increase 50.2 per cent and 70.6 mills/kWh at 23 mW/cm2, against 1.53 km, 5.05 GW, 6.8 km, 46 per cent, 17 per cent and 55 mills/kWh at 54 mW/cm2, and at 5.8 GHz with a 33 per cent improved thermal limit 0.75 km, 2.72 GW, 5.8 km, 33 per cent, 36 per cent and 64 mills/kWh; the January 1980 MPTS workshop panel called the number "based on an obsolete theoretical foundation and is without experimental support", and the Arecibo experimenters wrote that it "may be well below threshold for producing serious telecommunications impacts".
Evidence behind this: T3, a NASA JSC sizing study's abstract with a costed three-column table, and three other papers' judgments in the same volume.
Scope and limits
Differential costs only ("any future changes in the absolute costs for the reference system should not have a great impact"); the 5.8 GHz case "may have to be shut down under very poor weather conditions". The workshop's "obsolete theoretical foundation" names no paper.
What it assumes
The reference electricity cost implied by 70.6 at +50.2 per cent is 47 mills/kWh (1979 dollars, Boeing basis).
Where it comes from
PDF p.319 / printed 297, normalised: "Subsequent ionospheric heating tests conducted at Plattville, Colorado, and Arecibo, P. R. during the past year (the results of which are reported elsewhere at this conference) have indicated this 23 mw/cm2 threshold may be too low"; PDF p.320 / printed 298: the "probably too low" sentence as quoted; "Four constraints were considered: (1) the 23 mw/cm2 ionospheric limit (2) a higher (54 mW/cm2) ionospheric limit (3) the 23 KW/m2 thermal limit in the antenna, and (4) an improved thermal design allowing 33% additional waste heat"; "Transmit antenna diameters should be limited to 1-1.5 km for 2.45 GHz operation and .75-1.0 km for 5.8 GHz"; PDF p.321 / printed 299: "Multiple (two to four) antennas on a single solar satellite ... are definitely recommended"; the same page, render read: the three-column table as stated, with "Note: The rectenna areas and electricity costs are in comparison to those for the reference SPS system." Cost ground rules (PDF p.320 / printed 298): "30 year operating lifetime, plant factors of .92 and .90 for 2.45 GHz and 5.8 GHz operation respectively, 15% rate of return on investment capital, 22% mass growth factor ... 10 GW per year", costs from "Boeing Aerospace Final Report D180-25461-2, November 1979". Freeman, PDF p.369 / printed 347: "The panel believes that top priority should be given to determining a hard upper limit for the permissable microwave power density which can be sent through the ionosphere. The number being used, 23 mW/cm2 is based on an obsolete theoretical foundation and is without experimental support, and yet it is a constraining parameter in a number of the SPS design areas." Duncan and Gordon, PDF p.428 / printed 407: "These results indicate that significant ionospheric effects can be generated by SPS-equivalent heating. However, they indicate that the current SPS microwave-beam power density design limit of 23 mW/cm2 may be well below threshold for producing serious telecommunications impacts." Livingston, PDF p.114-115 / printed 91-92 (the sentence runs over the page break): "recent evidence that 23 mW/cm2 may be conservative".
Basis: mW/cm2 at the ionosphere; km; GW; mills/kWh
Related records
- Answers question
- QST-001 not published in this release
Cite this
energyaperture.com/c/clm-1059
CLM-1059, Energy Aperture, as of 1980-04.
Connected records
Other published records linked to this one. A list, not a judgement.
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