Page:Popular Mechanics 1928 11.pdf/18

 reaching the high mountains near the end of the journey, when his ship had been lightened by the consumption of most of its fuel.

Opel's rocket-car and rocket-plane experiments are important because the rocket offers the one method yet discovered for navigating space at high altitudes, above the earth's envelope of air. All existing motors depend on air for their operation, and all existing types of propellers screw their way through the self-same air. The rocket, on the other hand, can be shot out into space and attain tremendous speed by escaping the resistance of the air.

The rocket idea is not new. Prof. R. H. Goddard, at Clark University, Worcester, Mass., made some experiments and calculations as long ago as 1912 and 1913, to prove that it was technically feasible to shoot a rocket to the moon and explode a giant charge of magnesium powder, producing a flash big enough to be observed by telescopes on the earth.



Three German engineers, H. Oberth, W. Hohmann and Max Valier, and the work of the latter largely inspired Herr Opel's rocket car and plane. Valier has calculated that a rocket plane could be shot from Berlin to New York in ninety-three minutes, dividing the journey in three stages. He would start from the German capital and come down at Vigo, Spain, take off there for an island in the Atlantic, and make the third hop to New York. He would shoot his rocket into the air at the steep angle of seventy degrees in order to reach the region of rarefied air in the shortest possible time. A minute and five seconds after the take-off, the plane would be thirty miles above the earth and nearly forty-five miles from the starting point, and would have attained a speed of more than 4,500 miles an hour. Allowing 100 seconds to get under way and reach full speed and 1,500 seconds for gliding, Vigo would be reached in twenty-seven minutes from Berlin.

The only objection he sees to rocketing across the ocean is the weight of the explosives required. Fully sixty-nine per cent of the entire weight of the ship on the 