Value chain · CLM-0995
In plain terms
The whole ten-kilometre satellite was designed to sway once every fourteen minutes, and the antenna was required to be at least as stiff as once every ten minutes so that ordinary control could keep it pointed to a twentieth of a degree.
The claim as recorded
Grumman's 1978 design data for the Boeing Phase I satellite state its natural frequency "including solar cells and antennas" as 0.0012 Hz and the solar blanket's as 0.0024 Hz at a 4.285 N/m preload; Rockwell's 1981 requirements databook sets a minimum modal frequency of 0.0016 Hz for its 1 km tension-web antenna, because "classical control techniques require the first modal frequency of this configuration (Figure 3.1-27) to be above 0.0016 Hz" to hold earth pointing to 0.05 degree. Boeing's design rule orders the frequencies: blanket above satellite, power bus an order of magnitude above satellite, antenna on its compliant joint below the control-moment-gyro band.
Evidence behind this: T3-contractor design data and a contractor requirement; neither is a computed mode for the 1 km antenna.
Scope and limits
TWO DIFFERENT STRUCTURES, AND NEITHER IS THE ONE CALC-109 MODELLED. Grumman's 0.0012 Hz is the whole 10.7 x 5.3 km satellite; Rockwell's 0.0016 Hz is a requirement on a 1 km tension-web antenna, not a computed value; CALC-109's band of 0.088 to 0.69 Hz is for a 1 km, 40 m deep antenna structure and sits two decades higher because the structure is fifty times shorter. Rockwell's Figure 3.1-27, the configuration the requirement applies to, has not been rendered and may carry a computed value.
What it assumes
No assumptions are recorded against this claim.
Where it comes from
printed p.9, raw: "SPS NATURAL FREQUENCY INCLUDING SOLAR CELLS & ANTENNAS - 0.0012 Hz"; "SOLAR BLANKET NATURAL FREQUENCY - 0.0024 Hz"; blanket preload 4.285 N/m; masses solar arrays 5.178e7 kg, antennas 2.521e7 kg, growth 2.051e7 kg, total 9.75e7 kg. SRC-582 printed 3-95, normalised: "(3) minimum modal frequency to be compatible with overall minimum of 0.0016 Hz"; printed 3-96: "the integrated structure/control system must maintain the earth pointing accuracy of the antenna to within 0.05 degree. For that requirement, classical control techniques require the first modal frequency of this configuration (Figure 3.1-27) to be above 0.0016 Hz." Boeing's ordering: SRC-495 printed p.22-area (PDF 38) and SRC-456's Phase I companion Vol III, the bus tensioned "to maintain the natural frequency of the power bus system higher than that of the satellite"; SRC-495 PDF 132, the antenna hung on "a highly compliant mechanical joint so that the natural frequency of the antenna in its mechanical supports is below the control frequency bands for the CMG's".
Basis: Hz, first natural frequency
Related records
- Answers question
- QST-013 not published in this release
Cite this
energyaperture.com/c/clm-0995
CLM-0995, Energy Aperture, as of 1981.
Connected records
Other published records linked to this one. A list, not a judgement.
- Also from SRC-456
- CLM-0977In 1978 Boeing worked out how the timing reference should fan out across the kilometre-wide transmitter. The choice of how many branching...CLM-0979The three designs disagreed about what the guide signal from the ground should look like. One used a pair of tones either side of the...CLM-0981Smaller patches tolerate more bending: halving the patch from 10 m to 5 m doubles the allowed tilt for the same half-per-cent loss. A...CLM-0998With the top of a five-kilometre section of the satellite two hundred degrees Fahrenheit hotter than the bottom, the estimate has its free...
- Also from SRC-582
- CLM-0996The beams the reference satellite would be built from are specified down to the wall thickness, and two contractors give the stiffness...CLM-0997The designers said how flat the antenna had to stay: within about half a metre overall, with the surface elements out of true by no more...CLM-0999Rockwell hung a small transmitter above the antenna to give every patch the same timing reference, and each patch corrected its own...CLM-1432Rockwell's chart puts a price in mass on a flatter antenna. The frame for the 1,000 m radius weighs about 85 tonnes if it may deviate by 48...