Heinkel
In February 1936, Pohl wrote to Ernst Heinkel telling him of von Ohain's design and its possibilities. Heinkel arranged a meeting between his engineers and von 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 von Ohain and Hahn began working for Heinkel at the Marienehe airfield outside Rostock, in Warnemünde.
A study of the model's airflow resulted in several improvements over a two month period. Encouraged by these findings, von 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 started late in the summer of 1936, and completed in March 1937. It ran two weeks later on hydrogen, but the high temperature exhaust led to considerable "burning" of the metal. The tests were otherwise successful, and in September the combustors were replaced and the engine was run on gasoline for the first time. Von Ohain had at last, albeit 5 months after Whittle, run a self-contained turbojet. Running on gasoline proved to clog up the combustors, so Hahn designed a new version based on his soldering torch, which proved to work much better. Although the engine was never intended to be a flight-quality design, it proved beyond a doubt that the basic concept was workable. Von Ohain had caught up with Whittle at last. From now on, with vastly more funding and industry support, Von Ohain would soon overtake Whittle and forge ahead.
While work on the HeS 1 continued, the team had already moved on to the design of a flight-quality design, 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 as a whole by placing the flame cans in an extended gap between the compressor and turbine. The original design proved to have a turbine area that was simply too small to work efficiently, and increasing the size of the turbine meant the flame cans no longer fit in the gap correctly. A new design, the HeS 3b was proposed, which moved the flame cans out of the gap and modified their shape to allow the widest part of the cans to lie in front of the compressor's outer rim. In the 3b, compressed air was piped forward to the combustion chambers, and from there the now-hot air flowed rearward into the turbine inlet. While not as small as the original HeS 3 design, the 3b was nevertheless fairly compact. The 3b first ran July 1939 (some references say 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.
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 8 separated the compressor and turbine, connecting them with a long shaft, placing a single annular combustion chamber between them, replacing the individual flame cans. 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 had brought on Adolph Müller from Junkers, who was developing an axial compressor-powered design, renamed as the Heinkel HeS 30. Müller had 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 their 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 more quickly. Both engines were still some time from being ready for production, however, while the 003 and 004 appeared to be ready to go. In early 1942 the director of jet development at the RLM, Helmut Schelp, refused further funding for both designs, and ordered Heinkel to work on a new "pet project" of his own, eventually becoming the Heinkel HeS 011. Although this was the first of Schelp's "Class II" engines to start working well, production had still not started when the war ended. Work continued on the HeS 8 for some time, but it was eventually abandoned in the spring of 1943.
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