Hans von Ohain

Hans Joachim Pabst von Ohain (14 December 1911 – 13 March 1998) was a German physicist, engineer, and the designer of the first turbojet engine to power an aircraft.

Together with Frank Whittle he is widely described as the co-inventor of the turbojet engine.

Hans von Ohain was still a university student when in January 1930, Whittle filed his first patent for a turbojet engine.

Von Ohain stated in his biography, that "My interest in jet propulsion began in the fall of 1933 when I was in my seventh semester at Göttingen University. I didn't know that many people before me had the same thought.".

Born in Dessau, Germany, Ohain earned a PhD in physics in 1933, with his thesis on an optical microphone to record sound directly to film, at the University of Göttingen, then one of the major centers for aeronautical research, having attended lectures by Ludwig Prandtl.

In 1933, while still a student, he conceived what he called "an engine that did not require a propeller".

According to von Ohain, "My interest in jet engines began in about 1933. I found that the elegance of flying was spoiled by the enormous vibrations and noise from the piston engine/propeller combination. I came to the conclusion that a constant work process, i.e. constant compression, combustion, expansion, would have great advantages. Thus I chose a quite simple engine, a radial compressor with a radial turbine."

However, the model he and Max Hahn built and tested in the courtyard of the Institute showed the combustion chamber needed further development.

As a consequence, Pohl and von Ohain decided to approach Heinkel as someone who "doesn't back away from new ideas".

When in 1935 von Ohain designed his overall engine layout, he based it for compactness on a centrifugal impeller (centrifugal or radial compressor) and a radial inflow turbine.

However, von Ohain explains in his biography, that in 1935, while his own patent was being prepared,(and before he had begun construction of an engine) his lawyer gave him a copy of Whittle's patent which he read and critiqued.

As a result, he was forced to modify his own application, so as not to infringe on Whittle's design.

After receiving his second degree in Physics and Aerodynamics in 1935, Ohain became the junior assistant of Robert Wichard Pohl, then director of the Physical Institute of the university.

In 1936, while working for Pohl, Ohain registered a patent on his version of a jet engine, Process and Apparatus for Producing Airstreams for Propelling Airplanes.

Unlike Frank Whittle's Power Jets WU design with its axial flow turbine, Ohain used a radial in-flow turbine to go with a centrifugal compressor, placing them back-to-back with an annular combustion space wrapped around the rotor.

While working at the university, Ohain used to take his sports car to be serviced at a local garage, Bartles and Becker.

There he met an automotive mechanic, Max Hahn, and eventually arranged for him to build a demonstration model of his engine for.

In February 1936, Pohl wrote to Ernst Heinkel, telling him about Ohain's design and its possibilities.

Heinkel arranged a meeting between his engineers and Ohain, during which he argued that the current "garage engine" would never work, but that the concept upon which it was based was sound.

The engineers were convinced, and in April Ohain and Hahn began working for Heinkel at the Marienehe airfield outside Rostock, in Warnemuende.

Working with Engineer Gundermann and Hahn in Special Development, von Ohain states: "Under pressure of aiming to bring a combustion chamber of unknown endurance to flight readiness, I came upon the idea of separating the turbine problem from the combustion chamber problem by using hydrogen fuel. As a physicist, I knew of course that the diffusion and combustion speed of gaseous hydrogen was substantially greater than that of petrol."

A study of the model's airflow resulted in several improvements over a two-month period.

Encouraged by these findings, Ohain produced a new prototype that would run on hydrogen gas supplied by an external pressurised source.

The resulting Heinkel-Strahltriebwerk 1 (HeS 1), German for Heinkel Jet Engine 1, was built by hand-picking some of the best machinists in the company, much to the chagrin of the shop-floor supervisors.

Hahn, meanwhile, worked on the combustion problem, an area in which he had some experience.

The core of Ohain's first jet engine, the Heinkel HeS 1, which he described as his "hydrogen test engine" was run "in March or early April" according to Ohain (although Ernst Heinkel's diaries record it as September 1937).

Work on the hydrogen test engine continued but the engine required modifications to cure overtemperature problems and to fit a fuel system to enable it to run self-contained on liquid fuel which was achieved in September 1937.

The completed model was larger in diameter than Whittle's fully working engine of 1937, although much shorter.

Ohain took the model to the university for testing but ran into problems with combustion of the petrol fuel, which took place mostly after the turbine, sending flames shooting out from the exhaust duct.

The lack of combustion before the turbine contributed to the engine being unable to run without the assistance of the electric motor which subsequently overheated.

Ultimately this configuration had too many shortcomings to be to be put into production, however aided by the enormous resources of the Heinkel Aircraft Company, a developed version was sufficient to power the He-178, and on 27 August 1939, von Ohain entered history, as the designer of the world's first gas turbine to power an aircraft.

Von Ohain stayed with centrifugal designs, contributing his research to Heinkel's other projects, such as the combined centrifugal/axial HeS8 and 011 but ultimately, none of his designs were put into production and other competing German designers at Junkers and BMW, following the axial design layout, saw their engines in production, although they never solved some of the basic power and durability problems.

With the heavy backing of Heinkel, Ohain's jet engine was the first to power an aircraft, the Heinkel He 178 aircraft in 1939, which was followed by Whittle's engine within the Gloster E.28/39 in 1941.

Turbojet powered fighter aircraft from both Germany and Britain entered operational use virtually simultaneously in July, 1944,

the Me 262 on July 26 and the Gloster Meteor on July 27 of 1944, so the Me 262 was the first operational fighter jet and saw flight combat with hundreds of machines, while the few dozen Meteors saw limited action.

After the war the two men met, became friends and received the Charles Stark Draper Prize for Engineering "for their independent development of the turbojet engine."

Von Ohain nevertheless started the world's first jet engine industry in his homeland of Germany with many prototypes and series productions built till 1945.

Von Ohain, having entered turbojet design some time later than Whittle, began working on his first turbojet engine designs during the same period that Whittle was building his WU engine in Britain.

Their turbojet designs have been said by some, to be an example of simultaneous invention.

He quickly caught up with Whittle due to the support by Heinkel and his design, "an axial-flow engine as opposed to Sir Frank's centrifugal flow engine, that was eventually adopted by most manufacturers by the 1950's."