Of all of the designs Müller brought with him, the HeS 30 was 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 its designed RPM, which limited compression and required a continuous supply of external compressed air. Junkers abandoned the design when Müller left, choosing to develop the Jumo team's simpler design instead. Müller promised Heinkel 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 keep.