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 18 2011, 09:25 AM
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#2
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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 24 c) Mulfunction by latch-up About the possibility of ICs latching-up (note 12) by high energy particles those ICs used on board except one of them (59MeV/(mg/cm)) had line (or linear, P) energy investment (this must be wrong and it is most certainly "tolerance" or something starting with T, because abbreviation is, P) (LET) of more than 75MeV/(mg/cm ). Even if we assume more than 59MeV/(mg/cm ) the possibility of latching-up by galactic cosmic rays is thought to be once in a thousand years or so. Furthermore, the solar flare of 21 April was such that protons should not have reached the sort of energy which might have caused the latch-ups. Even if we turn our attention to heavier particles such as iron they only appear during the initial stage of the event and it is unthinkable for them to cause failre after a few days of the solar flaring event. (note 12) : Latch-up Short circuiting inside ICs 2) Destruction/electromagnetic interferance by discharge It is possible that discharging may have caused a current flow through the satellite body and onboard instruments/devices may have been affected through latch-ups etc. About this discharging there are a few possibilities as follows. a) Charging and discharging by high energy particles Discharging could be caused by accumulation of a large amount of electric charge inside conductive layers which are not earthed. However, in the case of NOZOMI, because of observation requirements an absolute care had been taken regarding charging and discharging issues and as shown per below there are few places for charge accumulation and the possibility is considered to be extremely low. ・All external surfaces of the satellite These surfaces are earthed to the satellite frame structure with 1MΩ or below and only one exception are a few patches on the rear side of the solar cell panels. ・ Thermal blanckets (MLI) All layers with areas larger than 100cm (sic, P) are earthed. Also, the surface material is "Black C(or K, P) apton" (carbon coating) and no cracks are possible and for this reason earth lines being cut is unimaginable. ・Inside of the satellite - 25 - (here again, this should read 24 and when I checked this before translation with the original it was 24... I will no longer be yapping about this as it should not have been any of your concern, P) All conductors are earthed down to the level of shielding layers for electrical appliances and unearthed circuit ground pattern does not exist as far as the design is concerend. For this reason it is unimaginable for charge accumulation to take place which may lead to discharging. end of page 24 P |
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