Hans von Ohain

Hans Joachim Pabst von Ohain (14 December 191113 March 1998) was a German physicist, engineer, and the designer of the first aircraft to use a turbojet engine.

Together with Frank Whittle and Anselm Franz, he has been described as the co-inventor of the turbojet engine. Additionally, prior to building his engine and filing his own patent in 1935, von Ohain had read and critiqued Whittle's patents. 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."

Ultimately, this configuration had too many shortcomings 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 was put into production. Other competing German designers at Junkers and BMW, following the axial design layout, saw their engines brought into production, although they never solved some of the basic power and durability problems. Von Ohain nevertheless started the world's first jet engine industry in his homeland of Germany, with many prototypes and series productions built until 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. 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.

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 fix overtemperature problems and to fit a fuel system to enable it to run self-contained on liquid fuel, which was achieved in September 1937. 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. 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.

Although Von Ohain and Whittle both knew about axial flow compressors, they remained dedicated to improving centrifugal compressor engines to power respectively the Heinkel He 178 and the Gloster E.28/39 until the end of the Second World War. Axial flow compressor jet engines were instead developed in parallel by Anselm Franz (Junkers) and Hermann Oestrich (BMW) to design the similar Jumo 004 and BMW 003 engines, designs that were eventually adopted by most manufacturers by the 1950s.

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."

Early life and jet development

Born in Dessau, Germany, Ohain finished high school in 1930 at the Arndt-Gymnasium in Dahlem and earned a PhD in physics in 1935 at the University of Göttingen, with his thesis entitled An Interference Light Relay for White Light on an optical microphone to record sound directly to film, which led to his first patent. The University of Göttingen was then one of the major centers for aeronautical research, with Ohain 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". 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 . 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.

thumb|Mechanic Max Hahn and the major components of Hans von Ohain's test engine

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".

Heinkel

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." While in a very strict sense this may be true (in that he was unaware of Whittle's experiments at Lutterworth where the RAF engineer ran the world's first jet engine on the 12th of April 1937), nevertheless Ohain had been given a copy of Whittle's patents by his lawyer, while his own patent application being prepared and before he had begun construction of an engine.

In his biography, Ohain frankly critiqued Whittle's design:

"When I saw Whittle's patent I was almost convinced that it had something to do with boundary layer suction combinations. It had a two-flow, dual entrance flow radial flow compressor that looked monstrous from an engine point of view. Its flow reversal looked to us to be an undesirable thing, but it turned out that it wasn't so bad after although it gave some minor instability problems ... Our patent claims had to be narrowed in comparison to Whittle's because Whittle showed certain things." He then somewhat understandably justified their knowledge of Whittle's work by saying: "We felt that it looked like a patent of an idea ... We thought that it was not seriously being worked on."

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Developing the engine

In February 1937, the turbine section was running on a test stand. According to von Ohain, "We were now working on a machine capable of powering an aircraft, the forerunner of the He-S3B. I had intended to put the combustion chamber between the compressor and the turbine, as we had done with the hydrogen unit, but Hahn suggested putting it ahead of them, which was an excellent idea." The He-S3 turbine was test flown by Erich Warsitz and Walter Künzel in a Heinkel He 118, providing additional throttled thrust to the conventional engine.

Post-World War II

In 1947, Ohain was brought to the United States by Operation Paperclip and went to work for the United States Air Force at Wright-Patterson Air Force Base. in which the airflow through the engine created a stable vortex that acted as the compressor and turbine.

This interest in mass-flow led Ohain to research magnetohydrodynamics (MHD) for power generation, noting that the hot gases from a coal-fired plant could be used to extract power from their speed when exiting the combustion chamber, remaining hot enough to then power a conventional steam turbine. Thus an MHD generator could extract further power from the coal, and lead to greater efficiencies. Unfortunately this design has proven difficult to build due to a lack of proper materials, namely high-temperature non-magnetic materials that are also able to withstand the chemically active exhaust. Ohain also investigated other power related concepts.

He also invented the idea of the "jet wing", in which air from the compressor of a jet engine is bled off to large "augmented" vents in the wings to provide lift for VTOL aircraft. A small amount of high-pressure air is blown into a venturi, which in turn sucks a much larger volume of air along with it, thus leading to "thrust augmentation". The concept was used in the Rockwell XFV-12 experimental aircraft, although the market interest in VTOL aircraft was short-lived. He participated in several other patents.

Ohain was the influence in shifting the mind of Paul Bevilaqua, one of his students at WP-AFB, from math to engineering, which later enabled Bevilaqua to invent the Rolls-Royce LiftSystem for the JSF F35B STOVL: "in school I learned how to move the pieces, and Hans taught me how to play chess". Ohain also showed Bevilaqua "what those TS-diagrams actually mean".

Ohain retired from Wright-Patterson in 1979 and took up an associate professor position teaching propulsion and thermodynamics at the nearby University of Dayton,

Awards

During his career, Ohain won many engineering and management awards, including (among others) the American Institute of Aeronautics and Astronautics (AIAA) Goddard Astronautics Award, the United States Air Force Exceptional Civilian Service Award, Systems Command Award for Exceptional Civilian Service, the Eugene M. Zuckert Management Award, the Air Force Special Achievement Award, and just before he retired, the Citation of Honor. In 1984–85, Ohain served as the Charles A. Lindbergh Chair in Aerospace History, a competitive senior fellowship at the National Air and Space Museum. In 1991 Ohain and Whittle were jointly awarded the Charles Stark Draper Prize for their work on turbojet engines. Ohain was elected a member of the U.S. National Academy of Engineering (NAE).

In 1982, Ohain was inducted into the International Air & Space Hall of Fame at the San Diego Air & Space Museum.

In 1990, Ohain was inducted into the National Aviation Hall of Fame.

Death

Ohain died in Melbourne, Florida, in 1998, aged 86. He was survived by his wife and four children. One of his sons, Christopher von Ohain, joined the United States Marine Corps (USMC). Christopher's son, Hans Christopher von Ohain, also joined the USMC; he was killed in a car accident in 2022.

References

Sources

External links

Hans von Ohain, U.S. Centennial of Flight Commission.
entry of Hans von Ohain in Rostock Matrikelportal