Value chain · CLM-1089
In plain terms
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.
The claim as recorded
The 5.8 GHz ISM band was costed as the alternative three times and never adopted. JSC 1977: "2450 MHz and 5800 MHz frequencies have similar end-to-end transmission efficiencies for lower transmit powers." and "Primary advantage of 5800 MHz frequency is reduced rectenna land area (1/5) but must be traded off against adverse weather degradations." Boeing 1977 recommended an integrated 5.8 GHz design definition for low-rainfall areas. JSC 1980-81 re-optimised at both frequencies and found the 5.8 GHz configurations "constrained by antenna thermal limitations rather than ionospheric limits", with klystrons at 80 per cent against 85, and selected for analysis a 0.75 km antenna delivering 2.72 GW to a 5.8 km rectenna, 33 per cent of the reference rectenna area at a 36 per cent electricity cost increase (64 mills/kWh), against 2.45 GHz alternatives of 1.36 km / 2.76 GW / 7.6 km at 50.2 per cent and, if the ionospheric limit rose from 23 to 54 mW/cm2, 1.53 km / 5.05 GW / 6.8 km at 17 per cent. TM-58232 summarised the 5.8 GHz system as costing "slightly more than the reference system" with rain degradation whose grid impact "is not known"; RP-1076 said a serious 5.8 GHz alternative needs "an in-depth study".
Evidence behind this: T3-three programme costings of the 5.8 GHz alternative, 1977-81; tabulated differential costs read at the page, with the sizing study's groundrules stated.
Scope and limits
DIFFERENTIAL COSTS AGAINST A 1979 BASELINE, IN 1980 MILLS PER kWh; TP-1804 says its purpose is relative cost and that absolute changes to the reference "should not have a great impact". The 5.8 GHz case is thermally limited only with klystrons; TM-58232's conclusion d (SRC-552 PDF p.68 / 52) says solid-state amplifiers give "a different thermal limit". No document costs 3 GHz or 10 GHz as alternatives; the 1975 sweep's 1 to 5 GHz axis and CR-2357's 2 to 4 GHz range are bounds, not costed options. The weather penalty is asserted from the loss tables in CLM-1090, which disagree with each other.
What it assumes
TP-1804's groundrules: the reference antenna error budget, rectenna sized for 88 per cent of transmitted power, Boeing D180-25461-2 (SRC-495) costs as baseline, 10 dB gaussian taper, and a 33 per cent better radiator for the 5.8 GHz case.
Where it comes from
PDF p.91 / IV.C.10, NORM: "The SPS reference system operates at 2.45 GHz, which is at the center of a 100 MHz band reserved for government and non-government industrial, medical, and scientific (IMS) use." and "This reduction in rectenna size must, however, be traded-off against the large temporary degradation in transmission efficiency under extremely adverse weather conditions at the higher frequency."; trade space 1 to 5 GW, 0.5 to 2 km antenna, 3.8 to 12 km rectenna, 77 to 90 per cent RF-DC, 2450 and 5800 MHz; reference link efficiency 62.88 per cent. PDF p.102 / IV.C.21, NORM, the two quoted conclusions; also that antennas under 1 km at 2450 MHz and 0.75 km at 5800 MHz "are not practical" (reported; "diameter@" run together). SRC-482 PDF p.217 / 198, TRANSCRIBED "The next higher industrial band at 5.8 GHz is particularly suitable in areas of relatively low rainfall." (text layer "partkularly", "ofrefatively"); NORM "An integrated design definition should be developed for a transmission system operating at 5.8 GHz." SRC-449 PDF p.319 / 297, NORM: "This thermal limitation is a severe constraint on higher frequency (5.8 GHz) systems which have lower efficiency klystrons (80%) and smaller antenna areas."; p.320 / 298: plant factors 0.92 and 0.90 for 2.45 and 5.8 GHz, 30 year life, 15 per cent return, 22 per cent mass growth. SRC-552 PDF p.26 / 10, NORM, the two quoted passages. SRC-556 PDF p.26 / 21, NORM: items 3, 5 and 6 with the tabulated numbers; PDF p.44 abstract restates 2.72 GW, 0.75 km, 5.8 km, 67 per cent rectenna reduction, 36 per cent cost increase; item 5's 33 per cent radiator improvement is the assumption. SRC-107 PDF p.60 / 31, NORM: "If a 5.8-gigahertz microwave system is to be seriously considered as an alternate to a 2.45-gigahertz system, an in-depth study of this area is required."
Basis: GHz; km antenna and rectenna diameters; GW; per cent relative rectenna area; per cent electricity cost increase; mills per kWh
Related records
- Answers question
- QST-017 not published in this release
Cite this
energyaperture.com/c/clm-1089
CLM-1089, Energy Aperture, as of 1977-1981.
Connected records
Other published records linked to this one. A list, not a judgement.
- Also from SRC-107
- CLM-0033 (low confidence)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...CLM-0060In 1981 a NASA review panel said the 230 watts per square metre figure rested on an obsolete theory with no experimental support, and made...CLM-0061The experiments were done. They found heating two or three times stronger than normal, not the tenfold effect predicted, no irregularities...CLM-0062By 1981 the theory was being revised to a steeper frequency dependence, which would raise the permitted power density.CLM-0063NASA 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...CLM-0101The 1978 contract required the researchers to report fixes if ionospheric disturbance pushed the pilot-beam phase error past 2 to 3...CLM-0160A 1978-81 NASA design study calculated that simply pointing the satellite's structure accurately enough, without any electronic correction...CLM-0420NASA's 1981 report says the experiments found nothing supporting the 23 milliwatt limit, that the measured heating was two or three times...More on the source page.
- Also from SRC-449
- CLM-0964To build two of these satellites a year, about 300 tonnes of material had to arrive at the orbital construction site every day. Getting it...CLM-0974The 1978 reference design shows every loss between sunlight and the power grid as a chain of numbered boxes, and the boxes multiply out...CLM-0975Depending on which published assumptions you take, a satellite needs between about 2 and 6 square kilometres of solar blanket for every...CLM-1058The often-repeated claim that the magnetron is 188 decibels quieter than its carrier traces to a conference abstract in which the tube...CLM-1059By spring 1980 the engineers, the reviewing panel and the ionosphere experimenters were all saying the beam-intensity ceiling the whole...CLM-1060The 1980 review did not agree with itself on how much of a satellite's cost was rockets: one paper said over a third, the programme's own...CLM-1061In one 1980 volume the satellite cost anywhere from about 2,300 to 3,800 dollars a kilowatt depending on who added what - and the programme...CLM-1062In 1980 the launch vehicle that everything was costed on was said by its own designers to be arbitrarily big, and they proposed a rocket a...More on the source page.
- Also from SRC-482
- CLM-1099Boeing'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...CLM-1100Boeing thought the receiving elements could be spaced almost twice as far apart as Raytheon's, halving their number, and that the receiver...
- Also from SRC-549
- CLM-1409A 1977 NASA study of how to hold up the receiving station's panels was told the ground underneath had to stay farmable, with a metal mesh...CLM-1486A 1977 NASA study of how receiving stations would join the US power grid looked at two kinds of shadow. For about six weeks around each...CLM-1487In Britain, the amount of fast back-up power kept ready depends mainly on the biggest single block of power that could be lost at once; the...
- Also from SRC-552
- CLM-1087When 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...
- Also from SRC-556
- CLM-1036The programme's own sizing arithmetic, with its rate of return stated: in the cases studied a bigger antenna always raised the cost, but...CLM-1037By 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...