Nozomi in perspective, Revisiting the causes of failure |
Nozomi in perspective, Revisiting the causes of failure |
Oct 23 2011, 09:12 AM
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Member Group: Members Posts: 817 Joined: 17-April 10 From: Kamakura, Japan Member No.: 5323 |
http://www.mext.go.jp/b_menu/shingi/uchuu/...ts/04061101.pdf
Above pdf file will be translated for aspiring students in aeronautics, control engineering etc. so that in future lay people like me will be able to enjoy planetary scenes and events without worrying about failures. The overall title is "Looking into the causes of failure and trying to find the right measures to take for the future with respect to the 18th scientific satellite (PLANET-B ) not inserted into Mars orbit as planned" and it is dated 21 May 2004. This file is very much detailed at 1.1 megabytes and the number of pages is about 40, I think. In addition, I will be translating 3 more files after this particular file. They will be; 1. ISAS file with views and comments on the failure 2. Another ISAS file, a newsletter written out in a series of 4 individual letters. 3. JAXA file, which is a press release and it is a very concise document with just sufficient details. Re concise link making I tried a few times, but I simply failed and all the links will be fully pasted out as required. Pandaneko |
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Nov 16 2011, 09:49 AM
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Member Group: Members Posts: 817 Joined: 17-April 10 From: Kamakura, Japan Member No.: 5323 |
above for ease of reference page 22 2.Estimated causes of mulfunction (1) Fault Tree Analysis (FTA) 1) We conducted a fault tree analysis (FTA) with the fact at the top of the tree that we received no waves despite being in the telemetry mode (TLM_ON). The result of this particular FTA is shown on the schematic (or graph) III-2-1. ① As for the possibility of data processing unit mulfunctioning we discarded it because command(s?) were issued normally and we were able to obtain data. ② As for the possibility of TMX mulfunctioning we discarded it because it fails to explain why we could not change attitudes and also because there was no abnormal current consumption by TMX. ③The fact that TCI power was OFF, that is to say we could not keep CI-PSU to be ON can explain without contradiction why we could not change attitudes. It also explains why we could not swtich between beacon and telemetry modes. 2) We conducted another FTA, following one of the the results of above FTA, that is to say ③of 1) above, with the fact at the top of the tree that we could not keep CI-PSU power to be ON all the time. The result of this particular FTA is shown on the schematic (or graph) III-2-2. There are three causes we could think of as follows. ① There was an anomally in the function whereby CI-PSU inside the satellite power source (PCU) is turned ON/OFF and this resulted in power not being available to CI-PSU. ② There was a mulfunction inside the primary side of CI-PSU and this meant that although the power was being supplied to CI-PSU the overcurrent protection mechanism worked and CI-PSU could not be brought to be ON. ③ There was a short circuiting inside the secondary side of CI-PSU and although the function of CI-PSU was normal the fact that there was an excessive current flowing downstream meant that protection mechanism activated within a few milliseconds, bringing the CI-PSU to be OFF. 3) Discussions about the result of above FTAs mentioned in section 2) These are as follows. As for ① of 2) above this was thought to be unthinkable because all other functions inside PCU were - 23 - normal. (this particular paragraph continues into page 24 and is rather lengthy for it being translated as part of page 23. So, I stop here and will continue immediately after this as page 24) end of page 23 P |
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