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 15

３．Estimating the causes of mulfunction

(1) Fault Tree Analysis (FTA)

We conducted an FTA with the following events at tree top in order to estimate where LV2 mulfunction occurred.

・ A command had been sent from the ground for opening of LV2 and LVDT did show that LV2 was open. However, in reality the opening was minimal and the flow rate was very small. The result of this FTA is shown on the table II-2-5. We at JAXA did exchange information with the US valve manufacturer after the accident. However, as mentioned earlier, the information relating to the valve structure etc was limited in availability.

We summarised the possible mulfunction candidates based on the FTA analysis as shown under (2) below.


(2) Possible mulfunction candidates

1) Bad sliding motion of the plug

One strtucural problem with LV2 is that the plug and the inner piece are separated physically. In addition, there is a possibility of the material surface of the sliding component inside the valve suffered from a fletching wear due to the valve motion and this led to the issue of valve material's compatibility with the oxidiser.

It is thought possible that these two factors might have led to bad sliding motion of the valve.


(note 6) : fletching wear

surface damage arising from repeated slidings at the sliding area


a) Valve structure


We did conduct a repeat evaluation on the past flight records and had confirmation that valves with this particular material had flown many times in the past. However, these valves had a monostructure of the plug and the inner piece and the valve was forced to activate with an electromagnet.


With respect to the valve that we used its (valve) open mode was similar to that of so called check valves in that it opens passively when there is a diffential pressure before and after the plug. The driving force arising from this differential pressure was smaller compared with the force originally ensured by an electromagnet and the valve could have suffered if the plug's sliding force resistance (note 7) had increased.


（note 7） : sliding force resistance (please note that this sentence astrides pages 15 and 16)

The resistance against the sliding motion involving two objects in contact. If this force becomes large

- 16 -

then objects become harder to slide against each other, requiring a larger force for sliding.

end of page 15

P