Value chain · CLM-1075
In plain terms
Keeping the satellite on station against sunlight pressure was reckoned at eight per cent of its mass in argon over thirty years and 34 megawatts of its power; the antenna had to stay flat to half a metre across nearly two kilometres; and the review panel said confidence in all this rested on hope rather than evidence.
The claim as recorded
Rockwell's April 1980 attitude-control and station-keeping budget for the GaAs reference satellite: solar pressure (E-W) 282.5 m/s per year and 6.65 per cent of spacecraft mass over 30 years, solar/lunar perturbation (N-S) 53.3 and 1.25, earth triaxiality (E-W) 2.1 and 0.05, microwave radiation pressure negligible, station change manoeuvres 1.1 and 0.03, total 339.0 m/s per year and 7.98 per cent at "Isp = 13,000 sec"; "If uncorrected, the solar pressure perturbation will cause a +/-2.5 deg cyclical change in longitude with a one-year period"; the AC&SK system is "Nominally 36 thrusters ... however, 64 are provided", 13 N argon ion thrusters at 1275 kW each, "The average operating power is 34 megawatts", mass 23.07 t dry with 85.39 t of argon a year; the solid-state dual configuration needs "27.5%" of spacecraft mass over 30 years and an asymmetric single one "41.1%". The structures papers: antenna flatness "essentially 0.5 m across a diameter of 1700 m", achievable at "2 arc minutes" with a low-CTE composite; "the entire solar pressure and gravity gradient load on a 1700-m-diameter aperture antenna is less than the design load on 13 cm2 of the orbiter crew module (142 N)"; and the January 1980 structures and control workshop: "such optimism would be based more on wishes and past success than on hard evidence. The work to date has simply not gone far enough or looked deep enough to provide real confidence in the ultimate viability of the SPS."
Evidence behind this: T3, Rockwell's attitude-control budget from two rendered tables, two structures abstracts and the January 1980 workshop's judgment.
Scope and limits
Rockwell's budget is for its own configuration; Boeing's silicon satellite is not budgeted here. Power processing mass "TBD".
What it assumes
Isp 13,000 s argon ion thrusters (against the EOTV's 7,963 to 8,000 s); the GaAs CR=2 configuration's area-to-mass ratio.
Where it comes from
PDF p.190 / printed 168, Table 1, render read: rows as stated; text "the solar pressure stationkeeping perturbation becomes dominant rather than the solar-lunar gravitational perturbation"; the +/-2.5 deg sentence; orbit trade "EQUATORIAL 0 0 46 M/SEC 1.25" against "ECLIPTIC 23.4 88.5%". PDF p.191 / printed 169, normalised: "Nominally 36 thrusters are required; however, 64 are provided to accommodate for failures and servicing"; PDF p.192 / printed 170: "THRUST - 13N; SPECIFIC IMPULSE - 13,000 SEC; POWER - 1275 KW; APERTURE - 1M; MASS ... 120 KG; ... OPERATING LIFE (GRIDS & CATHODES) - 5000 HR"; "is 0.08% of the spacecraft mass (dry) and 0.37% with annual propellant requirement. The average operating power is 34 megawatts"; "low SPS structural frequencies in the order of 6 cycles/hour". PDF p.193 / printed 171, Table 2, render read: 0.32, 7.68, 15.07, TBD, 85.39, 23.07, 108.46 (x 10^3 kg); "PROPELLANT REQUIRED IS 27.5% SPACECRAFT MASS OVER 30 YEARS (ISP = 13,000 SEC)"; "(41.1% of spacecraft mass over 30 years)". PDF p.194 / printed 172: the 0.5 m and 142 N sentences; PDF p.195 / printed 173: graphite "a = 0.36 x 10-6 m/m C", thermal loads "1 to 3%" against "20 to 40%" for aluminium. PDF p.187 / printed 165: "the desired flatness of 2 arc minutes could be achieved by state-of-the-art manufacturing tolerance"; "a 7% scale system (.4% full scale energy) in low earth orbit can provide a reasonable similitude for verification testing". PDF p.211 / printed 189: the workshop sentences as quoted; PDF p.212 / printed 190: "Current SPS structural designs utilize forms which basically derive from 19th century bridge-building technology"; "the controls problem had received disproportionately little attention"; "much additional work was required to provide a confidence level necessary for the selection of graphite composite".
Basis: m/s per year of station-keeping dV; per cent of spacecraft mass over 30 years; kg of AC&SK hardware and propellant; MW; m of flatness
Related records
- Answers question
- QST-013 not published in this release
Cite this
energyaperture.com/c/clm-1075
CLM-1075, 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.