Heinkel HeS 30

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The HeS 30 was an early jet engine, originally designed by Adolf Müller at Junkers, but eventually built and tested at Heinkel. It was possibly the best of the "Class I" engines, a class that included the more famous BMW 003 and Junkers Jumo 004, but work on the design was stopped by the RLM as they felt the Heinkel team should put all their efforts into other designs. The "official" name for the engine is the 109-006, and it would normally be known as the HeS 006, but development was ended just as these names were being introduced by the RLM, and thus the "HeS 30" name remains much more common.

Herbert Wagner started engine developments at Junkers in 1936, placing Adolf Müller in overall charge of the project. In 1938 Junkers purchased Junkers Motoren (Jumo), formerly a separate company. In October 1939, under pressure from the RLM, Junkers moved all their engine work to Jumo's Dessau factories from their main Junkers plants at Magdeburg. Müller would have ended up in a subordinate role after the move, and decided to leave instead. He and about half of the original Junkers team were scooped up by Ernst Heinkel and moved to his Rostock campus, where Hans von Ohain was working on the Heinkel HeS 3 engine.

Of all of the designs Müller brought with him, what soon became known as the HeS 30 was the simplest and easiest to build. Müller had already built a test engine while still at Junkers, however it was only able to run at about half speed, and then only with continuous supply of external compressed air. The design was abandoned when Müller left, the Jumo team's simpler design being used instead. Müller promised Heinkel that he could have the engine up and running on a testbed within one year of completing the move, a promise he was ultimately unable to meet.

Key to the engine's working cycle was an axial compressor of then-unique construction. Most German engines of the era had the stators do all of the actual compression, with the rotors speeding up the air for them to compress. In the HeS 30, the rotor and stators shared compression, about 50-50, a design originally provided by Rudolph Friedrich of Junkers. Overall the engine had a five-stage compressor providing air at a 3:1 compression ratio to ten flame cans, which powered a single-stage turbine. The turbine was also unique for the era, using a set of guide vanes that were adjustable for various operating speeds. Like most German axial engines, the engine also included a variable exhaust cone to lower back pressure when starting, and an electric starter motor.

Due to the move, it took considerable time for the team to restart work on the design, and even though three experimental engines were ordered as the 109-006 in 1939, it was not until May 1942 that the first engine actually ran. In addition to problems with move, the compressor turned out to provide more mass flow than initially suspected, forcing a redesign of the turbine. Additionally, in May Müller and Heinkel had an argument that eventually led to Müller quitting.

Work on the engine continued, and by October it was running at full speed. Of all of the early engines, the HeS 30 was by far the best design. It produced a thrust of 860 kg, about the same as contemporary designs, but weighed only 390 kg, providing a much better power-to-weight ratio. The engine also had better specific fuel consumption and was smaller in cross-section as well. It has been said that the overall performance was not matched until 1947.

Helmut Schelp, in charge of engine development at the RLM, refused to give Heinkel a production contract, an event that Hans von Ohain claims brought Ernst Heinkel nearly to tears. Schelp noted that while the design was excellent, BMW and Jumo were so far ahead that they simply didn't need another "Class I" engine – something that would prove to be rather ironic in another two years.It also appears he had some misgivings about the compressor arrangement, but if this was the case it was never official. He also canceled von Ohain's Heinkel HeS 8 at the same time.

Instead of "yet another" Class I engine, Schelp asked Heinkel to continue work on a "Class II" engine of about 1,300 kg thrust, which would be needed for reasonably sized single-engine fighters, as well as useful twin-engine bombers. Thus work on the HeS 30 and HeS 008 ended, and Heinkel turned, gudgingly, to the Heinkel HeS 011, which would not enter production before the war ended. The remains of Müller's team were then moved to the Heinkel-Hirth plants to work on the new engine.

Starting some time in 1940 or 41, the basic mechanical layout of the HeS 30 was also used on an experimental constant-volume engine known as the Heinkel HeS 40.