Orbital, Attitude, and Deployment Considerations for a Passive Space Array
Special technical rept. 5, 1 Apr-30 Nov 1975
STANFORD RESEARCH INST MENLO PARK CA
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This report examines the feasibility of long-distance, jam-resistant satellite communication by means of a completely passive array of scattering elements that is attitude-stabilized by the earths gravity gradient. The orbital, attitude, and deployment considerations for this array are discussed in this report. A preliminary design was developed for a passive space array that meets electromagnetic, orbital, attitude, deployment, and manufacturability requirements. The central portion of the prototype consists of 10,000 spherical aluminum scattering elements uniformly space along a straight vertical line to form an array 150 meters long. The spheres are 1 cm in diameter and are resonant over the frequency range 10 or - 0.5 GHz. They are supported by 75 segments of stiff wire 1 mm 40 mils in diameter. These segments are connected by joints whose free motion is limited to 3 deg. The stiff sections were found to be needed to absorb transverse kinetic energy occurring during deployment. To provide needed damping of librational motions, each end of the array will be extended by a coil of the same construction as the main array, but prestressed to assume a pigtail shape when released in space. Each coil will have a radius of 5 meters and will carry 2000 spheres. These coils provide damping by converting librational energy into flexural motion, which in turn is subject to viscous forces in the joints. A damping time constant of less than two months was calculated.
- Unmanned Spacecraft
- Spacecraft Trajectories and Reentry
- Radio Communications