Biggest Booster Yet

A brilliant flame, 700 ft. tall, towered over the swampy coast near Brunswick, Ga., as the loudest continuous sound ever made by man shook both land and sea. For 64 roaring seconds the gigantic flame rivaled the sunlight while a column of light brown smoke climbed high in the sky. Then the fire stopped abruptly. The first static test of the most powerful rocket motor ever built was a complete success.

Inside Out. The 3,000,000-lb.-thrust engine was constructed by Thiokol Chemical Corp. to prove the feasibility of very large, solid-propellant boosters. It is 100 ft. long, 156 in. in diameter, paced with 800,000 Ibs. of ammonium perchlorate and powdered aluminum held together with synthetic rubber. This potent stuff is cured in a single carefully shaped "grain" with a star-shaped cavity and burns from the inside out. The nozzle is made of plastic, spun silica and fibrous graphite.

No motor nearly this big had ever been fired before, but the fuel burned so evenly, and its outside layers were such a serviceable insulator, that all parts of the steel casing remained at air temperature. The nozzle was meant to erode slightly as the corrosive exhaust gases raced out at supersonic speed. But after its throat cooled, the big nozzle looked almost new; about half an inch had been tooled smoothly away as if by a delicate grinding machine. If X rays show no internal damage, the nozzle can be used again.

Traditional Cluster. Propulsion Chief A. O. Tischler of the National Aeronautics and Space Administration, who watched the firing, pronounced the test "an unmitigated, unqualified, unequivocal, unadulterated success." Such strong language does not match NASA's traditional coolness toward solid-propellant boosters. Its ambitious Apollo program to land men on the moon by 1970 is based on North American's liquid-fueled F-l engine, which generates only 1,500,000 Ibs. of thrust. Five Fls will have to be clustered together to boost the Apollo rocket off the ground.

The F-l is reported doing well after five years and $289 million of development cost, but it has not flown yet; and even more money and time must be lavished on it before a cluster of F-1s can be considered a safe enough booster for the ride to the moon. Thiokol's 156-in. motor, twice as powerful as the Fl, worked the first time. Its development cost was only $6,500,000.

President Harold Ritchie of Thiokol is confident that in 2 1/2 years he can have a cluster of four solid-fuel motors with 28 million Ibs. of thrust flying at a cost far below the price of an equivalent liquid-fuel booster. A cheap backup booster with such enormous power might easily save the moon program from half a decade of frustration.

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