>>14242848There is some pattern, however the pattern isn't consistent.
The 6 and 6A are both 3.35m kerolox(+SRB) rockets by CASC's 8th academy, whereas the 7/7A/8 are 3.35m kerolox rockets by CASC's 1st academy. So there the number differentiates the manufacturers and the letter differentiates the models. In terms of architecture, the 6A is more similar to the 7/7A/8 than the 6.
However, For 1-4, the number differentiates the launcher architecture and the letter differentiates manufacturers. The 2C and 2D are extremely similar, however 2C is by the 1st academy while the 2D is by the 8th academy.
The 5DY shares the 5m tank diameter and YF-100 engines with the 5/5B so it arguably has more in common with the 5 than any other CASC rocket.
