In 1933, Hans von Ohain wrote his PhD thesis at the University of Göttingen on the topic of an optical microphone that could be used to record sound directly to film.

In February 1936, Pohl wrote to Ernst Heinkel on behalf of von Ohain, telling him of the design and its possibilities.

The engineers were convinced, and in April, von Ohain and Hahn were set up at Heinkel's works at the Marienehe airfield outside Rostock, Germany in Warnemünde.

Much happier with the results, they decided to produce a completely new engine incorporating all of these changes, running on hydrogen gas.

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.