Hans Joachim Pabst von Ohain (14 December 1911 – 13 March 1998) was a German-American 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." Unlike Whittle, von Ohain had the significant advantage of being supported by an aircraft manufacturer, Heinkel, who funded his work.
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.
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".
After receiving his PhD 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 500 ℛ︁ℳ︁. 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.
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".
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.