Science: More Power to You

Bolted motionless on a test stand, the little monster is not impressive. It has no coolly symmetrical propeller, no phalanx of cylinderheads, none of the hard geometrical grace of the conventional aircraft engine. Yet the unprepossessing turbojet engine has thrown the air designers into ecstatic confusion: nobody yet knows how fast the jet will enable man to fly, but the old speed ceilings are off. In their less guarded moments, sober designers talk of speeds so high that aircraft will glow like meteors.

The coming of the turbojet does not mean that the engine in use since the first days of the Wright brothers (pistons and propellers) is done for. It will be a long time, if ever, before that old stand-by disappears; it still has the edge over jets for many purposes, including long-range bombers. But where the power range of the old engine stops, the power of the jet begins. An air revolution is beginning too.

Next Moment, Whoom! To watch* a jet engine spring into life is to feel that power. Dimly visible inside is the turbine, like a small windmill with close-set vanes. When the starting motor whines, the turbine spins. A tainted breeze blows through the exhaust vent in the tail, followed by a thin grey fog of atomized kerosene. Deep in the engine a single sparkplug buzzes. A spot of fire dances in a circle behind the turbine. Next moment, with a hollow whoom, a great yellow flame leaps out. It cuts back to a faint blue cone, a cone that roars like a giant blowtorch. The roar increases to thunder as the turbine gathers speed. Then it diminishes slightly, masked by a strange, high snarl that is felt rather than heard. This is "ultrasonic" sound (a frequency too high for the ear to hear). It tickles the deep brain, punches the heart, makes the viscera tremble. Few men like to stay in a test room when a jet is up to speed.

The engine now has the fierce beauty of power. Its massive rotor, the principal moving part, is spinning some 13,000 times per minute (though with only the faintest vibration). The fire raging in its heart would heat 1,000 five-room houses in zero weather (though much of the engine's exterior is cool). From the air intake in its snout, invisible hooks reach out; their suction will clasp a man who comes too close and break his body. The blast roaring out the tail will knock a man down at 150 ft. The reaction of the speeding jet of gas pushes against the test stand with a two-ton thrust. If the engine were pointing upward and left unshackled, it would take off like a rocket, each pound of its weight overbalanced by more than two pounds of thrust.*

"Get Busy." When an airplane designer looks at this engine, his gloating eyes light up. He knows that it develops some 5,000 horsepower—even more when moving through the air at high speed. But it weighs less than half as much as an equivalent piston engine, and is much more simple to build.