The Birth of the Jet: The Engine that Shrunk the World

In today’s time it is easy to take for granted the complex inventions that alleviate our everyday life. The modern jet propelled airplanes for example, are one of the biggest drivers behind rapid globalisation and play a major role in world trade. Nevertheless, the development that revolutionised aviation and inaugurated the era of jumbo jets came in a time of European and World conflict. It was at the dawn of World War II that two engineers from opposing sides of the war, separately and unaware of the other’s contribution, engineered the Jet Engine that would shrink the world in the 20^th century and set the groundwork for other milestones in aviation such as supersonic flight and space exploration.

The notion of jet propulsion has been around for centuries. The concept of jet engines can actually be traced back to the first century AD, when Hero of Alexandria introduced the “aeolipile”. This machine used pressurised steam forced through two jet nozzles placed on the surface of a sphere so as to force the sphere to spin rapidly on its axis [1]. Jet propulsion got off to its “flying start” with the Chinese invention of the rocket used for fireworks in the 11th century. By the early 20th century jet propulsion was a known principle and viewed as a potential alternative to standard propeller engines, especially in high-speed flight. By the 1920s jet engines, powered by an external power source, were used to propel racing planes but proved to be inefficient for low-speed flight.

On the German side of WWII a young German physicist, Hans von Ohain, was at the forefront of research into jet propulsion [2]. Hans von Ohain was born in

Heinkel He 178, the world’s first aircraft to fly purely on turbojet power, using an HeS 3 engine (Photo credit: Wikipedia)

Dessau on December 14, 1911 and received his Ph.D. in Physics and Aerodynamics from the University of Göttingen. During his studies he established the notion that one could build “an engine that did not require a propeller.“ Von Ohain’s first attempt to build a jet engine, which he patented in 1936, was not a great success. The jet engine had been built by an automotive engineer, Max Hahn, but ran into serious problems with combustion stability [3]. Most of the fuel would not ignite within the engine but would combust in the outside air. This caused flames to shoot out the back and prompt the electric motor powering the compressor to overheat. When Ernst Heinkel, one of the largest German aircraft manufacturers of the time, heard of von Ohain’s work he recognised the promise of the design and started to provide financial and technical funding [1].  After a two-month period of research on the airflow in the engine Max Hahn, von Ohain and Heinkel’s best engineers completed construction of a totally new engine that ran on hydrogen. As the high-temperature hydrogen exhaust damaged the metal framework, the old HeS 1 engine was refined to run on gasoline, a centrifugal compressor and axial turbine stages. This new engine, the HeS 3b, was then fitted to a new test airframe, the Heinkel He178. On August 27, 1939 the Heinkel He178 took off from Marienehe aerodromand was thus the first jet-powered airplane. In 1940 the engine designer Anselm Franz developed the Jumo 004 engine with an axial-flow turbojet, as opposed to the centrifugal-flow designs [4] of the original von Ohain engines. This engine was used to propel the Messerschmitt Me262 in 1942, the only jet fighter airplane in WWII.

At about the same time in England Frank Whittle, born on June 1, 1907 in Earlsdon as the son of a mechanic, developed his version of the jet engine unaware of von Ohain’s achievements. In a 1928 in an astonishing student essay Future Developments in Aircraft Design Whittleshowed that at increasing altitudes of flight the lower outside pressure and density of air would reduce drag with subsequent improvements in fuel efficiency and flight speed. In these conditions Whittle

The Whittle W.2/700 engine flew in the Gloster E.28/39, the first British aircraft to fly with a turbojet engine, and the Gloster Meteor (Photo credit: Wikipedia)

contemplated speeds of 600 mph at 60,000 feet when at the time the fastest RAF plane flew at 150 mph at a maximum altitude of 15,000 feet. However, current designs based on the internal combustion engine were being starved of oxygen at higher altitudes, which essentially limited current fighter planes to lower and slower flight conditions. Whittle therefore proposed a new form of propulsion – the jet engine.

Whittle’s patent showing a centrifugal-flow engine with a multi-stage axial followed by a centrifugal compressor was granted in 1932. Unluckily Whittle was unable to excite either RAF nor the government to fund his work. Therefore he, Rolf-Dudley Williams and J. Tinling, two ex-RAF men who were interested in his work, incorporated the Power Jets Ltd. Even though the company only received minimal funding from outside investors, Power Jets were able to complete and run their first engine, the Whittle Unit, on April 12, 1937. This achievement triggered the interest of the Air Ministry, which now started to grant minimal amounts money in order to develop a flyable version. On May 15, 1941 the revised engine W.1 with 3.8 kN thrust and manufactured by Rover was fitted to the Gloster E.28/39 airframe and took off for a flight of about 17 minutes with a maximum speed of 545 km/h. Rolls-Royce then took over the development and production of the Whittle engine, which led to the Whittle-type Rolls-Royce Welland and the W.2 engines [5]. These new designs were used to propel the interceptorGloster Meteor 1 in 1944.

After the war the British shared Whittle’s technology with the United States, enabling the engine-builder General Electric (GE) to build jet engines for America’s first jet fighter, the Bell XP-59. Another American jet engine designer Pratt & Whitney improved the fuel economy of jet engines, while a General Electric engineer named Gerhard Neumann introduced the variable stator; preventing jet engines from gulping in too much air and restraining them from losing all their thrust [5].

During the last 40 years jet engines have been improved in a variety of ways. For example, manned superplanes like the X-15 can fly almost 7 times the speed of sound, while the new A380 can transport up to 800 passengers in a luxurious ambience. It is remarkable to say that the early steps taken by Whittle and von Ohain laid the foundation for all these new magnificent aircraft.

Diagram of a typical gas turbine jet engine (in English). Air is compressed by the fan blades as it enters the engine, and it is mixed and burned with fuel in the combustion section. The hot exhaust gases provide forward thrust and turn the turbines which drive the compressor fan blades. (Photo credit: Wikipedia)