Gentlemen, I have a revelation. We have been underestimating the whole thing.
The mainstream posters here have been relaying Weibo/Guancha PLA gossipers. Gossipers who have hearsay but no real inside - Oh, I saw three nozzles, three! - Then, come up with some explanation with which their common sense is comfortable.
After 5 minutes of Google image search "NGAD TBCC" and a meditation.
I conclude that both 6-gen are using two TBCC (parallel turbofan + ramjet) engines right now!
How it works in J36:
The middle main shaft (engaged with two TBCCs through transmission) has a large low-pressure fan (LPfan) that is then serially connected to a small turbojet (APU). The flow out of the middle nozzle replaces the need for a large tail boom.
At low altitudes, the middle LPfan acts as extra bypass, thus two TBCCs in tubefan mode have higher bypass ratio.
At high altitudes, the shaft disengages from transmissions, and all engines act in turbojet mode.
At around Mach2, the inlet flow goes through LPfan and then diverts to the ramjet chamber of TBCCs.(there are 6 pipes that do this in J58), TBCCs switch to ramjet mode.
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Because of this unique configuration, the J36 prototype will only be made when TBCC is ready. The MD series is the platform testing various combined-cycle engines. In USA, SR-72 is the platform that indicates TBCC readiness.
The chief designer of J36, Wang haifeng, who is also the chief of the TBCC project, breakthrough in 2019.
Two things were revealed weeks before J36 debut.
1. MD-19 MD-22,
2. A 13 years research aims at broadbody hypersonic commercial jet. Test done at 6.56 Mach in 2021. The presentation shows this image.
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The Russia 6-gen project PAK DP, the designer claims 4-4.3 Mach, up to 45,000 meters.
SR-72 drawing with tail boom
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SR-72 drawing without tail boom
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"The J58 engine had a bypass system that allowed some of the air entering the inlet to be diverted around the engine core and into the afterburner. This bypass air provided additional thrust and cooling at high speeds and also reduced the compressor surge and the inlet pressure recovery."
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