Hans Joachim Pabst von Ohain (14 December 1911 – 13 March 1998) was a German physicist and engineer who designed the first aircraft to use a turbojet engine. He worked with Frank Whittle and Anselm Franz, and together they are often called co-inventors of the turbojet engine. Before creating his own engine and filing a patent in 1935, von Ohain studied and gave feedback on Whittle’s earlier patents. In his biography, von Ohain wrote that his interest in jet propulsion began in the fall of 1933 during his seventh semester at Göttingen University. He did not know that others had previously considered similar ideas. Unlike Whittle, von Ohain had the support of Heinkel, an aircraft manufacturer that funded his work.
In 1935, von Ohain designed his engine layout, using a compact centrifugal impeller (a type of compressor) and a radial inflow turbine. However, this design had many issues and was not suitable for production. With help from Heinkel, a more advanced version was created to power the He 178. On 27 August 1939, von Ohain became known as the designer of the world’s first gas turbine engine used in an aircraft.
Von Ohain continued to focus on centrifugal designs, contributing to other projects like the HeS8 and 011 engines. However, none of his designs were produced in large numbers. Meanwhile, other German engineers at Junkers and BMW used axial designs, which were eventually made into working engines. These engines had some problems with power and durability. Despite this, von Ohain started Germany’s first jet engine industry, with many prototypes and production models built until 1945.
Von Ohain began his turbojet engine work later than Whittle but worked during the same time Whittle was developing his WU engine in Britain. Some say their designs were created independently at the same time. However, von Ohain explained that in 1935, before building his engine, his lawyer gave him a copy of Whittle’s patent. He read it and made changes to his own design to avoid copying Whittle’s work.
The core of von Ohain’s first jet engine, the Heinkel HeS 1, which he called his “hydrogen test engine,” was tested in March or early April 1937, though records show it was tested in September 1937. Modifications were made to fix overheating and to allow the engine to run on liquid fuel. By September 1937, these changes were completed. With Heinkel’s support, von 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 combat at nearly 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, while the Meteor saw limited use.
Both von Ohain and Whittle studied axial flow compressors but continued to improve centrifugal compressors for their respective aircraft until the end of World War II. Axial flow compressors were instead used by Anselm Franz (Junkers) and Hermann Oestrich (BMW) to create 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 honored with the Charles Stark Draper Prize for Engineering for their independent work on the turbojet engine.
Early life and jet development
Hans von 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 from the University of Göttingen. His PhD thesis, titled "An Interference Light Relay for White Light on an Optical Microphone to Record Sound Directly to Film," led to his first patent. At the time, the University of Göttingen was a major center for aeronautical research. Ohain attended lectures by Ludwig Prandtl, a well-known scientist. In 1933, while still a student, Ohain thought of an engine that did not require a propeller.
After earning his PhD in 1935, Ohain became a junior assistant to Robert Wichard Pohl, who was the director of the university’s Physical Institute. In 1936, while working with Pohl, Ohain registered a patent for his version of a jet engine, titled "Process and Apparatus for Producing Airstreams for Propelling Airplanes." His design used a radial in-flow turbine paired with a centrifugal compressor, arranged back-to-back with an annular combustion space around the rotor. This was different from Frank Whittle’s design, which used an axial flow turbine.
While working at the university, Ohain often took his sports car to a local garage, Bartles and Becker, for repairs. There, he met Max Hahn, an automotive mechanic. Ohain arranged for Hahn to build a demonstration model of his engine for 500 Reichsmarks. The model was larger in diameter than Whittle’s working engine from 1937 but shorter in length. When Ohain tested the model at the university, problems arose with the petrol fuel burning mostly after the turbine, causing flames to shoot 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 explained, "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 with a radial compressor and a radial turbine."
The model Ohain and 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, a company 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 the meeting, Heinkel said the current engine would not work, but the idea behind it was good. The engineers agreed, 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, Ohain said: "Because I wanted to test a combustion chamber that could last long enough for flight, I decided to separate the turbine problem from the combustion chamber problem by using hydrogen fuel. As a physicist, I knew that hydrogen burns much faster than petrol."
A study of the model's airflow led to several improvements over two months. Encouraged by these results, Ohain created a new prototype that used hydrogen gas from an outside pressurized source. The resulting engine, called the Heinkel-Strahltriebwerk 1 (HeS 1), was built by selecting some of the best machinists in the company. This made some shop-floor supervisors unhappy. Meanwhile, Hahn worked on the combustion problem, an area where he had some experience.
The engine was simple, mostly made of sheet metal. Construction started in the summer of 1936 and was finished in March 1937. Two weeks later, the engine ran on hydrogen, but the high heat from the exhaust caused the metal to burn. The tests were otherwise successful, and in September, the combustor was replaced, and the engine ran on gasoline for the first time. Running on gasoline caused the combustor to clog. Although the engine was not meant to be used in flight, it proved that the basic idea was workable. Ohain had finally caught up with Whittle. With more funding and support, Ohain would soon surpass Whittle.
It has often been said that Ohain did not know about Whittle's work. In a strict sense, this may be true because Ohain was not aware of Whittle's experiments at Lutterworth, where the RAF engineer tested the world's first jet engine on April 12, 1937. However, Ohain had received a copy of Whittle's patents from his lawyer before he began building his own engine.
In his biography, Ohain openly discussed Whittle's design:
In February 1937, the turbine section was tested on a stand. Ohain said, "We were now working on a machine that could power an aircraft, the forerunner of the He-S3B. I planned to place the combustion chamber between the compressor and turbine, as we did with the hydrogen unit, but Hahn suggested putting it before them. This was a good idea." The He-S3 turbine was tested by Erich Warsitz and Walter Künzel in a Heinkel He 118, adding extra thrust to the regular engine.
While work on the HeS 1 continued, the Pohl-Ohain team moved on to designing a flight-ready engine, the HeS 3. The main differences were using machined compressor and turbine parts instead of bent sheet metal and rearranging the engine layout to reduce its size by placing the annular combustor between the compressor and turbine. The original turbine was too small to work well.
At the start of 1939, the He-S3A was placed in the He 178 airframe for a display at Roggentin on July 3, 1939. However, this turbine was still not strong enough for flight. Ohain said, "We tried different combinations to improve the compressor diffuser and turbine nozzle vanes to increase thrust enough for the first flight. We found that a small diffuser behind the engine with a collar and splitter to redirect airflow worked better than high-speed flow through the entire tube. The final result of these changes was the He-S3B."
A new design, the HeS 3b, was proposed. It lengthened the combustor by placing the front part in front of the compressor's outer edge. While not as small as the original HeS 3 design, the 3b was still compact. The 3b first ran in July 1939 (some sources say May) and was tested in the Heinkel He 118 dive bomber prototype. The original 3b engine burned out quickly, but a second one was nearly finished at the same time as a new test airframe, the Heinkel He 178, which flew for the first time on August 27, 1939. This was the first jet-powered aircraft to fly, piloted by Erich Warsitz. Heinkel applied for a patent in Germany on May 31, 1939, for an "Aircraft power plant," invented by Max Hahn.
Work began immediately on larger versions, first the HeS 6, which was a bigger version of the HeS 3b, and then a new design called the HeS 8. This design rearranged the layout again, connecting the compressor and turbine with a large-diameter drum long enough to fit an annular combustion chamber between them. It was meant to be installed on the Heinkel He 280 fighter, but the airframe development went smoothly, and the engine had to be tested in gliding flights while work continued. A flight-ready HeS 8 was installed in late March 1941, followed by the first flight on April 2. Three days later, the aircraft was shown to a group of Nazi and RLM officials, who were impressed. Full development funds soon followed.
At this point, several turbojet projects were underway in Germany. Heinkel was so impressed with the concept that he arranged for Adolph Müller from Junkers to join the project. Müller was working on an axial compressor-powered design, which was later renamed the Heinkel HeS 30. Müller left Junkers after they bought the Junkers Motoren company, which had its own project, now called the Junkers Jumo 004. Meanwhile, BMW was making progress with its own design, the BMW 003.
Post-World War II
In 1947, Ohain was brought to the United States through Operation Paperclip and worked 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 was the Chief Scientist of the Aero Propulsion Laboratory at the same location.
During his time at Wright-Patterson, Ohain continued his personal research on various topics. In the early 1960s, he worked on designing gas core reactor rockets that kept nuclear fuel inside while using the working mass as exhaust. The engineering methods used for this purpose were also applied to other practical tasks, such as centrifuges and pumps. Later, Ohain used the basic mass-flow techniques from these designs to create a jet engine with no moving parts. In this engine, airflow created a stable vortex that acted as both the compressor and turbine.
Ohain’s interest in mass-flow led him to study magnetohydrodynamics (MHD) for power generation. He noted that hot gases from a coal-fired plant could be used to extract power from their speed as they exited the combustion chamber. These gases remained hot enough to power a conventional steam turbine, increasing overall efficiency. However, this design has been difficult to build because of a lack of suitable materials, such as high-temperature non-magnetic materials that can withstand chemically active exhaust. Ohain also explored other power-related ideas.
He invented the concept of the "jet wing," in which air from a jet engine’s compressor was directed to large "augmented" vents on the wings to provide lift for VTOL aircraft. A small amount of high-pressure air was blown into a venturi, which pulled a much larger volume of air along with it, creating "thrust augmentation." This idea was used in the Rockwell XFV-12 experimental aircraft, though interest in VTOL aircraft was short-lived. Ohain also contributed to several other patents.
Ohain influenced Paul Bevilaqua, one of his students at Wright-Patterson Air Force Base, to shift from studying math to engineering. This change later helped Bevilaqua invent the Rolls-Royce LiftSystem for the JSF F35B STOVL. Ohain also explained to Bevilaqua the practical meaning of TS-diagrams.
Ohain retired from Wright-Patterson in 1979 and became an associate professor teaching propulsion and thermodynamics at the nearby University of Dayton. He taught similar subjects during winter sessions at the University of Florida 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
Throughout his career, Ohain received many awards for his work in engineering and management. These included the American Institute of Aeronautics and Astronautics (AIAA) Goddard Astronautics Award, the United States Air Force Exceptional Civilian Service Award, the Systems Command Award for Exceptional Civilian Service, the Eugene M. Zuckert Management Award, the Air Force Special Achievement Award, and the Citation of Honor, which he received just before retiring. From 1984 to 1985, Ohain held the Charles A. Lindbergh Chair in Aerospace History, a special position for experienced scholars 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 awarded the Ludwig-Prandtl-Ring by the Deutsche Gesellschaft für Luft- und Raumfahrt (German Society for Aeronautics and Astronautics) for his outstanding work in aerospace engineering. In 1982, Ohain was added to the International Air & Space Hall of Fame at the San Diego Air & Space Museum. In 1990, Ohain was added to the National Aviation Hall of Fame.
Death
Ohain died 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.