Value chain · CLM-1065
In plain terms
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.
The claim as recorded
The programme's April 1980 microwave summary changed four reference-system parameters and costed the first: "It is recommended that phase conjugation be performed at each of the 101,000 power modules rather than at the 7,220 subarrays", at the price of "94,000 additional phase control receivers", justified at the May 1979 symposium "if the phase control receivers were less than $600 each" with "A later Boeing Aerospace Company study indicates that these receivers can be built for less than $600 in high volume quantities", the location jitter then scattering "6 MW of power at the tube level as compared to 87 MW at the subarray level"; amplitude jitter tightened from "+/-1 dB" to "a +/-1% amplitude tolerance" because klystron "voltage and amplitude regulations ... have to be maintained to approximately 1%"; graphite/aluminium metal matrix waveguides in place of aluminium; and startup and shutdown sequences ("random, incoherent phasing, and concentric rings-center to edge") whose sidelobes "were lower than the steady-state levels", the satellite shutting down "87 times per year due to solar eclipses"; the updated system is 6.72 GW radiated, "63% (DC/RF Input to RF/DC Output)", 10 deg rms phase error per power module, "2% failed at any one time", one arc-minute antenna and three arc-minute subarray alignment. The January 1980 panel, meanwhile, "tended to favor a closed-loop phase control system over the retrodirective approach", listing for the retrodirective system that "inadequate provision has been made for security and anti-jamming protection" and that "ionosphere problems or other uplink disturbances or interruptions could lead to sudden and complete loss of function".
Evidence behind this: T3, the programme's microwave system summary abstract with its recommended parameter changes and simulation results, and the panel's view.
Scope and limits
The 6 and 87 MW are simulation results ("Recent simulation results indicate the off-axis grating lobes may be considerably reduced from the data shown in the figures"); the $600 is a cost study, not a quotation.
What it assumes
No assumptions are recorded against this claim.
Where it comes from
PDF p.299 / printed 277, normalised: "The power beam has approximately 88% of its energy within a 5 Km radius from the rectenna boresight, with a resultant beam width of 1.2 arc-minutes. Mechanical alignment of the 1 Km antenna is maintained within one arc-minute while electronic alignment has a 1.8 arc-second accuracy"; "Physically the present rectenna configuration ... covers approximately 75 square kilometers"; the recommendation as quoted; the page's last sentence carries "increased costs due to the 94,000 additional phase control receivers". PDF p.300 / printed 278: the $600 sentences, "This location jitter, which appears as a phase error, scatters 6 MW of power at the tube level as compared to 87 MW at the subarray level"; "The reference SPS system has a +/-1 dB amplitude jitter ... Therefore a +/-1% amplitude tolerance is recommended for the antenna error parameter. This change will not affect the microwave transmission efficiency budget"; "a graphite/aluminum metal matrix composite is now being developed as a possible replacement for the aluminum"; "The satellite will have to shut down 87 times per year due to solar eclipses by the earth"; "Thus no microwave radiation problems are anticipated during startup or shutdown operations". PDF p.301 / printed 279: suppressor rings "a 5 dB reduction in sidelobe levels at the expense of a loss in rectenna collection efficiency"; summary list as stated. PDF p.367 / printed 345: the panel's sentences as quoted, and "Work should proceed on both closed loop and open loop systems. None of the phase control systems presented are clearly superior at this time."
Basis: number of receivers; dollars per receiver; MW scattered; per cent amplitude; degrees rms
Related records
- Answers question
- QST-013 not published in this release
Cite this
energyaperture.com/c/clm-1065
CLM-1065, Energy Aperture, as of 1980-04.
Connected records
Other published records linked to this one. A list, not a judgement.
- Also from SRC-449
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