Nozomi in perspective, Revisiting the causes of failure Options

[pandaneko]

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

[pandaneko]

http://www.mext.go.jp/b_menu/shingi/uchuu/...ts/04061101.pdf

above for ease of reference

page 25

Destruction/EM interference by high voltage instruments discharging

In the case of Nozomi all high voltage devices were thoroughly designed as shown per below so that they do not affect the working of other instruments and it is not thinkable that the secondary side of CI-PSU were affected.


① Dust counter (MDC)（±200V）

The high voltage part of the high energy particle counter (EIS)(3kV) is shrouded by the secondary ground of the instrument and even if discharges happen the design is such that no current will directly flow into the satellite structure.


② Ultraviolet imaging system (UVS)(3kV)

The sensor area which receives the high voltage is contained in a vacuum filled glass case. The part exposed to the external area is only the connecting part of the high tension cables and even those are designed so as not to affect the satellite structure.

(3) Estimating the causes of mulfunction

In the discussion concerning (2) above it is true that Nozomi did encounter a very rare magnitude of solar flare which produced groups of high energy partilces. However, there is no data available to verify the relationship between the mulfunction and the the solar flare. Furthermore, the possibility of destruction/EM interference by discharging is thought to be extremely low given the degree of thorough preparation at design stages.

For these reasons the only remaining cause of mulfunction is an accidental component failure. However, here again, the candidate component groups which could lead to single point of failure were rated at quality assurance level as class S equivalent (space use components) and from the viewpoint of failure rate the possibility of failure isthought to be low.

Table III-2-1 shows the accidental failure rates of main class S components.

Those components which may cause mulfunction are those that exist in the secondary side of the circuit and failure candidates and their properties are as follows.


①Ceramic condensors (２４ of them)

Even the largest accidental failure rate per one component is something like once in 90,000 years and this rate is regarded as extremely low as the single failure candidate. For your information, in the case of Nozomi, all the ceramic condensors were selected on the basis of anti-deteriolation and anti-high tension.

② Resisters （７ of them）

Here, the largest accidental failure rate is something like once in 20,000 years and furthermore, the possibility of line breakage leading to mulfunction is more likely. Thus, we do not believe that they were the causes of single failure event.

- 25 -

For your information, in the case of Nozomi, all resister were selected on the basis of anti-power deteriolation.

end of page 25

P