Fairing 4.2m and 5.2m, fuselage 3.8m. I got the kind of feeling that Tianbing is inhereting CASC 8th acadamy's work, see 2021 broshure from 8th academy. This is supposed to be the competitor to CZ-8 which is aiming at commercial launching market. 8th academy also worked on a CZ-5 or CZ-10 alternative using same components.
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Also in 2021, 800 factory of 8th acadamy made the 1st 3.8m tank.
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For a new company (2019) to quickly launch a totally new medium sized rocket in 2024, I don't think they start everything from scratch. I believe that after loosing the competion to CZ-8 within CASC, 8th academy is converting its investment and knowhow through commericial company. Very likely that 8th academy would act like supplier and manufacturer behind the scene. I think CASC and CASIC are acting as suppliers behind many commercial companies id nor moar, in area of manufacturing.
Here is another example. This engine Honglong-1 designed by a professor and NWPU, CZ-6 deputy chief designer, CZ-6 engine (special YF-100 variant) designer. Now he is the funder of this company.