Value chain · CLM-1085
In plain terms
By 1980 both contractors' satellites had grown about 2.3 to 3.5 times heavier per kilowatt than the 1974 sketch; the gallium arsenide cell assumed for 1990 was two points above the best in any laboratory, and the silicon array would lose almost a third of its output in thirty years unless it could be annealed in orbit.
The claim as recorded
The two photovoltaic reference options as their contractors stated them in April 1980. Rockwell GaAs: "9.52 GW of power at the array", "Array power output is calculated to be 352.6 W/m2" from "27.0 (10^6) m2" of cells, "a GaAs cell having a nominal efficiency of 20% (AMO, 28 C). Based on today's technology, 20% cell efficiency is expected by the year 1990. The best laboratory GaAs cells are presently around 18%", specific mass "0.252 kg/m2 versus 0.427 kg/m2" for silicon, annealing at "125 C threshold temperature ... versus >500 C", and "SPS mass estimates have grown by a factor of approximately 2.3 for GaAs configurations and 3.5 for Si configurations" since a 1974 estimate of "~2.3 kg/kW"; "Substitution of Si penalizes system by 22.2 x 10^6 kg or more". Boeing silicon: "The array area of 49.6 square kilometers generates 8766 megawatts (dc) electric power at 44 kV", "6700 megawatts of radiated RF power at 2450 megahertz", "101,552 high-efficiency Klystron power transponders", taper "from a maximum of 22 kW per square meter at the center of the antenna to 1/9 of this value at the edge", "About 85% of the power can be provided unconditioned from the solar array", and "an estimate of 30% output loss for the silicon satellite at the end of a 30-year book life period" before annealing. The February 1980 power-conversion workshop set "16% end-of-life efficiency (for GaAs) and 14% end-of-life efficiency (for silicon) after 30 years" as what "will need to be demonstrated", and Arthur D. Little judged GaAs cells "unlikely to be available before 1985 unless there is a near-term significant R&D program commitment".
Evidence behind this: T3, the two contractors' photovoltaic abstracts, a workshop's goals and a consultant's availability judgment, all design figures.
Scope and limits
Contractor abstracts; the 30 per cent loss is Boeing's estimate from "measured proton damage data for experimental 50-micrometer cells" extrapolated.
What it assumes
Nussberger's summer solstice input "1311.5 W/m2" (CLM-0975); Boeing's "generally pessimistic radiation model".
Where it comes from
PDF p.268 / printed 246, normalised: the 9.52 GW, 352.6 W/m2, 20 per cent, 18 per cent and 0.252 sentences as quoted; "solar cell degradation allowance (4% non-annealable loss), operating temperature of 113 C"; "The SPS design assumes that nearly all radiation damage can be self-annealed out or annealed out with sufficient time and proper temperature". PDF p.270 / printed 248: the growth-factor sentence; PDF p.271 / printed 249, Table 3: "Substitution of Si penalizes system by 22.2 x 10^6 kg or more"; "Total array cost $3130.2M". PDF p.272 / printed 250: the 49.6 km2, 8766 MW, 6700 MW and 30 per cent sentences; "the number of cells in series (about 77,000)". PDF p.273 / printed 251: the 101,552, taper and 85 per cent sentences. PDF p.293 / printed 271: the 16 and 14 per cent sentence; "Near term performance goals should be achievement of 16% efficiency in a suitable cell/substrate/cover structure". PDF p.286 / printed 264: the 1985 sentence; "The mass of the photovoltaic systems represents 40% of the mass of the SPS reference system" (PDF p.285 / printed 263).
Basis: per cent cell efficiency; W/m2; kg/m2; 10^6 kg; per cent output loss over 30 years; kg/kW growth factor
Related records
- Answers question
- QST-001 not published in this release
Cite this
energyaperture.com/c/clm-1085
CLM-1085, Energy Aperture, as of 1980-04.
Connected records
Other published records linked to this one. A list, not a judgement.
- 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.