“The jet plane carries no oxygen for its engine: its jet propulsion engine uses oxygen from the air. This engine has fewer parts and is of simpler construction than the traditional engine. It operates a mechanism which compresses the air. This air is mixed with atomized fuels such as gasoline, kerosene, alcohol, or some other fuels of the hydrocarbon family, rich in hydrogen. From that point forward the operation is the same as in the rocket engine; that is to say, the gas is released and ignited, the resulting expansion and emission through the jet providing the power.... “The development of the jet engine was made possible by a number of recent scientific achievements. One was the development of new alloys capable of withstanding extreme heat. The gases in combustion produce temperatures of 1500 degrees and over, and it is only in recent years that materials to resist such temperatures have been produced.... “Smoothness, simplicity, and evenness of power are three of the principal characteristics reported by pilots who have flown the new fighter plane powered by jet propulsion.... “Says one flier who has flown this plane: ‘It is the smoothest ride I’ve ever experienced in any plane. The first time I climbed into the cockpit I was naturally a little nervous about first contact with an entirely new method of propulsion. My nervousness persisted while I started the engines and until I started to taxi across the field for the take-off; then it dawned on me that this plane was even simpler to operate than a primary trainer. I flew it through all the maneuvers I wanted for twenty minutes, then landed, and taxied up to the line. “‘I wanted to check the fuel before resuming flight, so before turning on the main switch to read the electrical fuel gauges, I stuck my head out of the cockpit and shouted, to warn the mechanics to stay clear of the propeller, completely forgetting that I didn’t have any propeller.’... “Jet propulsion is necessary if we are to exceed the possibilities of propellers. A propeller literally screws its way through the air. The blades cause a partial vacuum. The greater the density of the air, the greater is the efficiency of the propeller. As we rise, the air becomes thinner. Finally a point is reached at which no propeller will ‘bite.’ The ceiling has been attained. “With jet propulsion, exactly the opposite holds good. The less air there is, the more efficient is the motor. If the ejected gas has an expansion efficiency at rest of 40 feet in one-hundredth of a second—a rate of 4,000 feet a second—the same force exerted in motion would increase the speed up to a point where the maximum efficiency is reached at something like 10,000 miles an hour. Jet propulsion gets better and better as speed and height increase. “As a matter of fact, with a fuel composed of liquid oxygen and gasoline, jet velocities of 12,000 feet a second have been obtained.”