CEO of TEI said the following:
"It's not the 35000lb thrust level that will challenge us in MMU's engine. We are confident that we will reach this level. There are some new technologies that will challenge us in MMU engine such as Converging Diverging nozzle technology that we are currently working on. Since the MMU engine is a new generation engine, it must be stealth"
And:
"The TF6000 is actually a technological preparation for the MMU's engine. When we increase the radius of the TF6000 by 15 cm, we will have reached the level of 35000lb thrust"
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With a inlet diameter of around ~60 cm, adding 15cm to its radius would mean an engine with ~90 cm inlet diameter providing 35000lb thrust! Very similar to the XF-9 diameter and thrust figure!