Boosted from the Sea

Rockets consume a great part of their fuel in their first few feet of flight. The process is wasteful, but despite years of effort, rocket engineers have been unable to do much about it. The big engines have no propulsive efficiency at all while standing still; their thunderous flames spend most of their energy moving air as the bird struggles to leave the ground. Only when it is moving fast does a rocket's efficiency rise.

Engineer G. Corry McDonald of Sandia Corp., Albuquerque, is sure that an old-fashioned approach will solve the problem of the modern missileman. McDonald's advice to his colleagues: Go back to the launching method used by Jules Verne in his From the Earth to the Moon. Verne's fictional spaceship of 1865 was fired out of a giant cannon--and the shot would have failed, for several reasons. For one thing, air resistance would have slowed the moon-bound vehicle. But McDonald argues for a sophisticated, factual approach to the Verne fiction.

To launch a 100,000-lb. rocket (about the weight of a Delta rocket), McDonald proposes to use a steel tube 8 ft. in diameter, 1,160 ft. long, anchored vertically in the sea. At the bottom, a door that keeps water out will open only when the pressure inside exceeds 500 lbs. per sq. in. The rocket will be suspended just above a mass of auxiliary fuel at the bottom of the tube. The top of the tube will be closed by airtight doors, and most of the air inside will be pumped out.

When the rocket is launched, its engine and the auxiliary fuel will be ignited at the same instant. The trapped combustion gases will produce a pressure of 500 lbs. per sq. in. that will drive the rocket upward with 3,600,000 lbs. of thrust and about 35 Gs of acceleration. It should reach the end of the tube in 1,205 sec. Air pressure will open the doors to let it pass, and it will pop out with the respectable speed of 1,000 m.p.h. Only 2,500 lbs. of its own fuel will have burned, and it will be moving so fast that its engine will have excellent propulsive efficiency.

McDonald estimates that the complete tube launching system would cost about $400,000 and that it could be reused many times. An equivalent rocket launched from some landlocked pad would use more than ten times as much fuel to reach the same speed.

This file is automatically generated by a robot program, so reader's discretion is required.