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The above article says that Iran is able to make exact copies of American General Electric J85 and Williams FJ33/FJ44 jet engines.

Does this mean that they are able to design and develop a jet engine from scratch?

If NO, why?

user366312
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This certainly does not mean they are able to design and develop usefull jet engines from scratch.

This pdf-file from rand.org offers some insight to the projected and actual cost of designing jet engines, ranging form 100 million to 1.5 billion dollars. While cost is not the subject of this question, it is an extremely good indicator of the difficulty of the process. The paper is dated october 1982, and one can be certain that designing a jet engine from scratch has not become cheaper or easier over the years.

The difficulty in designing modern jet engines largely lies in metallurgy, and having high level of understanding of the "inner workings" of the engines, based on research data of actual engines. Computational fluid dynamics can never fully replace actual empirical data (there is a good question with good answers about that specific subject here, I'll try to find and link it). it takes decades to accumulate this data and build the understanding.

To copy a GE J85 jet engine form the 60's is not a miraculous achievement, I personally would not "flaunt" that. The copying of the FJ33/FJ44 is not all that wonderful either, it is not excatly the pinnacle of high tech. What also remains uncertain is whether either of these is actually a reliable unit, or even functional for that matter.

In fact, pretty much anyone can design and build a jet engine:

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The real question is, how functional the final product is from efficiency and reliability points of view.
Jpe61
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    "one can be certain that designing a jet engine from scratch has not become cheaper or easier over the years" – But dollars have, so the numbers would be even higher in 2022 money. – Jörg W Mittag Mar 24 '22 at 11:38
  • Absolutely, the multiplier is roughly 3, so in todays dollars the top end of the spectrum would be about 4.5 billion. Then again, methods have improved, so the same relative technological progress would not be as expensive. – Jpe61 Mar 24 '22 at 16:59