Hans Joachim Pabst von Ohain (14 December 1911 – 13 March 1998) was a German physicist, engineer, and the designer of the first aircraft to use a turbojet engine. He worked with Frank Whittle and Anselm Franz. These three men are often called co-inventors of the turbojet engine. Before building his engine and applying for his own patent in 1935, von Ohain read and reviewed Whittle’s patents. In his biography, von Ohain said, “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 idea.” Unlike Whittle, von Ohain had the advantage of being supported by Heinkel, an aircraft manufacturer that funded his work.
In 1935, von Ohain designed his engine layout. He used a centrifugal impeller (a type of compressor) and a radial inflow turbine to make the engine compact. However, this design had many problems and was not suitable for production. With the help of Heinkel’s resources, a more developed version of the engine powered the He 178. On 27 August 1939, von Ohain became known as the designer of the world’s first gas turbine to power an aircraft.
Von Ohain continued using centrifugal designs. He contributed his research to other Heinkel projects, such as the combined centrifugal/axial HeS8 and 011. However, none of his designs were produced. Other German engineers at Junkers and BMW, who used axial designs, had their engines built. These engines had some issues with power and durability. Despite this, von Ohain started Germany’s first jet engine industry. Many prototypes and engines were built until 1945.
Von Ohain began working on turbojet engines later than Whittle. He worked on his designs during the same time Whittle was building his WU engine in Britain. Some say their designs were created at the same time. However, von Ohain explained that in 1935, before he built his engine, his lawyer gave him a copy of Whittle’s patent. Von Ohain read and reviewed it, then changed his own patent to avoid copying Whittle’s design.
The core of Ohain’s first jet engine, the Heinkel HeS 1, which he called his “hydrogen test engine,” was tested “in March or early April” (though records show it was tested in September 1937). Work on the hydrogen test engine continued, but the engine needed changes to fix overheating and to use liquid fuel. These changes were completed in September 1937. With Heinkel’s support, Ohain’s engine powered the Heinkel He 178 in 1939. Whittle’s engine powered the Gloster E.28/39 in 1941. Turbojet-powered fighter planes from Germany and Britain were used in battle at the same time in July 1944: the Me 262 on 26 July and the Gloster Meteor on 27 July. The Me 262 was the first operational jet fighter and saw heavy use, while the Meteor had limited action.
Both von Ohain and Whittle knew about axial flow compressors, but they focused on improving centrifugal compressors for the He 178 and the Gloster E.28/39 until the end of World War II. Axial flow compressors were developed by Anselm Franz (Junkers) and Hermann Oestrich (BMW) for the Jumo 004 and BMW 003 engines. These designs became widely used by the 1950s.
After the war, von Ohain and Whittle met, became friends, and were awarded the Charles Stark Draper Prize for Engineering “for their independent development of the turbojet engine.”
Early life and jet development
Ohain was born in Dessau, Germany. He completed high school in 1930 at the Arndt-Gymnasium in Dahlem and earned a PhD in physics in 1935 at the University of Göttingen. His thesis was titled 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 a major center for aeronautical research at that time. Ohain 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, who was the director of the Physical Institute at the university. In 1936, while working for Pohl, Ohain registered a patent for his version of a jet engine, titled Process and Apparatus for Producing Airstreams for Propelling Airplanes. Unlike Frank Whittle’s Power Jets WU design, which used an axial flow turbine, Ohain’s design used a radial in-flow turbine paired with a centrifugal compressor. These components were placed back-to-back with an annular combustion space wrapped around the rotor.
While working at the university, Ohain took his sports car to a local garage, Bartles and Becker, for service. There, he met an automotive mechanic named Max Hahn. Ohain arranged for Hahn to build a demonstration model of his engine for 500 Reichsmarks. The completed model was larger in diameter than Whittle’s fully working engine from 1937 but much shorter. Ohain tested the model at the university but faced problems with the petrol fuel combustion, which mostly occurred after the turbine. Flames shot out from the exhaust duct. The lack of combustion before the turbine made the engine unable to run without an electric motor, which then overheated.
Ohain said, "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 concluded that a constant work process—constant compression, combustion, and expansion—would have great advantages. Thus, I chose a simple engine design: a radial compressor with a radial turbine."
However, the model Ohain and Max Hahn built and tested in the courtyard of the Institute showed that the combustion chamber needed further development. As a result, Pohl and Ohain decided to approach Heinkel, who was known for supporting 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."
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 engine was extremely simple, made largely of sheet metal. Construction, by the blacksmith in his village, started late in the summer of 1936 and was completed in March 1937. Two weeks later the engine was running on hydrogen, but the high temperature exhaust led to considerable "burning" of the metal. The tests were otherwise successful, and in September the combustor was replaced and the engine was run on gasoline for the first time. Running on gasoline caused the combustor to clog up. Although the engine was never intended to be a flight-quality design, it proved beyond a doubt that the basic concept was workable, and Ohain had at last caught up with Whittle. With vastly more funding and industry support, Ohain would soon overtake Whittle and forge ahead.
It has often been claimed that Ohain was unaware of Whittle's work. 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:
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.
While work on the HeS 1 continued, the Pohl-Ohain team had already moved on to the design of a flight-quality engine, the HeS 3. The major differences were the use of machined compressor and turbine stages, replacing the bent and folded sheet metal, and a re-arrangement of the layout to reduce the cross-sectional area of the engine by placing the annular combustor in an extended gap between the compressor and turbine. The original turbine was too small to work efficiently.
In the beginning of 1939, the He-S3A was fitted into the He 178 airframe for a standing display at Roggentin on 3 July 1939. Yet this turbine was still not powerful enough for flight. According to von Ohain, "We experimented with various combinations to modify the compressor diffuser and turbine nozzle vanes to increase thrust sufficiently to qualify the aircraft for the first flight demonstration. We found that a small diffuser behind the engine with a collar and splitter to divert flows functioned better than a high speed flow through the entire tube. The final result of the changes was the He-S3B."
A new design, the HeS 3b was proposed, which lengthened the combustor by placing the forward part of it in front of the compressor outer rim. While not as small as the original HeS 3 design, the 3b was nevertheless fairly compact. The 3b first ran in July 1939 (some references say in May), and was air-tested under the Heinkel He 118 dive bomber prototype. The original 3b engine soon burned out, but a second one was nearing completion at about the same time as a new test airframe, the Heinkel He 178, which first flew on 27 August 1939, the first jet-powered aircraft to fly by test pilot Erich Warsitz. Heinkel had applied, May 31, 1939, for a patent: US2256198 Espacenet – Original document, an 'Aircraft power plant', inventor Max Hahn. First application for this patent in Germany was May, 1938.
Work started immediately on larger versions, first the HeS 6 which was simply a larger HeS 3b, and then on a new design known as the HeS 8 which once again re-arranged the overall layout. The compressor and turbine were connected with a large-diameter drum long-enough to fit an annular combustion chamber between them. It was intended to install the engine on the Heinkel He 280 fighter, but the airframe development progressed much more smoothly than the engine, and had to be used in gliding tests while work on the engine continued. A flight-quality HeS 8 was installed in late March 1941, followed by the first flight on 2 April. Three days later the aircraft was demonstrated for a party of Nazi and RLM officials, all of whom were impressed. Full development funds soon followed.
By this point there were a number of turbojet developments taking place in Germany. Heinkel was so impressed by the concept that he arranged the transfer to the project of Adolph Müller from Junkers, who was developing an axial compressor-powered design, renamed as the Heinkel HeS 30. Müller left Junkers after they purchased the Junkers Motoren company, who had their own project under way, which by this time was known as the Junkers Jumo 004. Meanwhile, BMW was making good progress with its own design, the BMW 003.
By early 1942 the HeS 8, officially the 109-001 (HeS 001), was still not progressing well. Meanwhile, Müller's HeS 30, officially the 109-006 (HeS 006), was developing much
Post-World War II
In 1947, Ohain was brought to the United States by Operation Paperclip and began working for the United States Air Force at Wright-Patterson Air Force Base. In 1956, he became the Director of the Air Force Aeronautical Research Laboratory. By 1975, he held the position of Chief Scientist of the Aero Propulsion Laboratory at the same location.
While working at Wright-Patterson, Ohain continued his personal research on various scientific topics. In the early 1960s, he studied the design of gas core reactor rockets, which would hold nuclear fuel while allowing exhaust gases to be used as propulsion. The engineering principles from this work were also applied to practical systems like centrifuges and pumps. Later, Ohain used the mass-flow techniques from these designs to create a unique jet engine with no moving parts. In this engine, airflow created a stable vortex that acted as both a compressor and turbine.
Ohain’s interest in mass-flow led him to research magnetohydrodynamics (MHD) for power generation. He noted that hot gases from a coal-fired power plant could be used to generate electricity from their speed as they exited the combustion chamber. These gases would remain hot enough to power a conventional steam turbine, increasing overall efficiency. However, this design has been difficult to build because of the need for special materials that can withstand high temperatures and chemically active exhaust. Ohain also explored other power-related ideas.
He invented the concept of the "jet wing," which uses air from a jet engine’s compressor to provide lift for vertical takeoff and landing (VTOL) aircraft. A small amount of high-pressure air is directed into a venturi, which pulls in a larger volume of air, creating additional thrust. This idea was tested in the Rockwell XFV-12 experimental aircraft, though interest in VTOL aircraft declined quickly. Ohain also contributed to several other patents.
Ohain influenced Paul Bevilaqua, one of his students at Wright-Patterson Air Force Base, to switch from studying math to engineering. This change helped Bevilaqua later develop the Rolls-Royce LiftSystem for the JSF F35B STOVL aircraft. Ohain also helped Bevilaqua understand technical diagrams, such as TS-diagrams, which are used in engineering.
Ohain retired from Wright-Patterson in 1979 and became an associate professor at the nearby University of Dayton, teaching propulsion and thermodynamics. He taught similar courses at the University of Florida during winter sessions from 1981 to 1983. Ohain continued teaching at the University of Dayton until 1992, when health concerns led him and his wife, Hanny, to move to Melbourne, Florida.
Awards
During his career, Ohain received many awards for his work in engineering and management, such as 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 the Citation of Honor just before he retired. From 1984 to 1985, Ohain held the Charles A. Lindbergh Chair in Aerospace History, a special position for experienced professionals 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 chosen to be a member of the U.S. National Academy of Engineering (NAE).
In 1992, Ohain was given the Ludwig-Prandtl-Ring by the Deutsche Gesellschaft für Luft- und Raumfahrt (German Society for Aeronautics and Astronautics) for "outstanding contribution in the field of aerospace engineering."
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 passed away in Melbourne, Florida, in 1998, at the age of 86. He was survived by his wife and four children. One of his sons, Christopher von Ohain, served in the United States Marine Corps (USMC). Christopher’s son, Hans Christopher von Ohain, also served in the USMC; he died in a car accident in 2022.