Monday, December 17, 2012

Grid-sphere passive communications satellite



"In 1959 the USAF became interested in the use of satellites as space reflectors for long distance communications. One possibility was a metalized balloon-type structure that could be boosted into space in a small container and inflated after it reached orbit. The NASA ECHO I, launched Aug. 12, 1960, was one of these. Unfortunately, the closed structure of the inflated balloon satellite was, in time, deformed and pushed out of orbit by the pressure created by the sun's radiation. Furthermore, small space particles caused drag which eventually reduced the balloon's speed. These minuscule influences were enough to prevent the balloon satellite from staying in a long-term orbit. It was gradually slowed and eventually fell from orbit.

To reduce the effects of solar pressure and space drag, the USAF contracted with the Goodyear Aerospace Corp. for construction of a 30-foot diameter grid-sphere balloon. It was made of a soft aluminum wire grid embedded in a special plastic designed to dissolve in space under the sun's strong ultraviolet rays. On July 13, 1966, the USAF grid-sphere payload was launched from Vandenberg Air Force Base, Calif., atop an Atlas booster. It went into orbit 620 miles above the earth and was automatically inflated with helium. The plastic covering soon dissolved, leaving a 30-foot diameter open aluminum structure orbiting the earth. Tests indicated that the satellite would remain in orbit for at least 11 years and that it had a reflective power five times greater than that of a solid sphere."

National Museum of the US Airforce

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