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 20th 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 DesignWhittleshowed
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)