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It's still a mystery whether Wenchang will see a launch over this weekend. What's sure is that there's a rocket delivery there today with the Yuan Wang 22, 1 of the 2 official Chinese rocket delivery ships, arrived w/ apparently a Long March 7A 1st stage for its re-flight. (1/5)pic.twitter.com/Zbd8ehb7Qx
The failure of the 1st Long March 7A last March was never explained publicly, but just after the LM-8 flight last December there was an official report that the LM-7A 2nd stage "lost pressurization a few seconds after stage separation". http://www.spaceflightfans.cn/85001.html (2/5)
The same article mentioned that vibration analysis were done on mock-ups for a pipe burst scenario. Alternatively there were rumors that the LM-7A reduced helium bottles capability on the 2nd stage from the LM-7 to save mass, but that turned out to be inadequate. (3/5)
There were testing issues pre-launch during engine gimbal tests too when it went too far & broke electric cables. Disputes were on w/ the structural dept. blamed inadequate testing procedures & the testing chief blamed inadequate cable alignment! http://t.cn/A64ZGyqY?m=4542691164034089&u=3279752321 … (4/5)
According to previous reports an "XJY-6-02" is in final assembly late last year, so it's probably going on the re-flight replacing the original one lost last year. Flight timeline of the 1st was leaked recently. Planned orbit was a 270 x 35991 km x 19.56° standard GTO. (5/5)pic.twitter.com/hMrnSIqHRA
So after the successful LM-7A RTF the official results of this investigation was revealed, confirming the loss of pressurization theory...but that happened on 1 of the 4 boosters' engine inlet & not the 2nd stage as reported above. This happened at T+168s, 5 seconds before MECO.
From the words of CALT's LM-7 program vice-chief: "We clearly saw on the rocket cameras that the rocket disintegrated during 1st stage separation." An early shutdown on 1 of the boosters would easily knock off the LV's attitude as the (combined) 1st stage/boosters separate.
This would explain the explosion a few seconds after MECO as seen from the ground in a video taken last year. It looks like "manufacturing defect" wasn't mentioned in the reports so the design fault theory mentioned above seems to be correct.
Liquid fuel rocket engines' pressurization has always been a thinly balanced act - the latest Starship woes a classic example - and this is yet another example that highly reliable rocketry is still some years away. Sources: https://video.weibo.com/show?fid=1034:4613833658925075 … /https://baijiahao.baidu.com/s?id=1693976852840836422 …
This article essentially stated that the team found that there was cavitation at one of the booster's LOX tank outlet: https://mbd.baidu.com/newspage/data/landingsuper?context=%7B%22nid%22%3A%22news_10130346967978642169%22%7D&n_type=-1&p_from=-1 …
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