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 16

oxidiser resistance of the material

Material combination of the sliding parts is austenite (spelling unsure, P) stainless steel at the sliding area of the plug, and ferrite staeinless steel for the valve body. Ferrite stainless is magnetic by nature and is used extensively with electromagnetically activated valves. On the other hand it is slightly less resistant against NTO compared with non magnetic austenite stainles steel.

It is thought possible that fletching wears would have led to corrosion of the valve body area in question after being filled with NTO, itself further leading to an increase in the sliding friction.

2) Gritting of the plug into the opening area

It is thought possible that the plug which had been pressed against the opening area for a long time might have gritted into the opening, making the plug less mobile. It is also thought that from the status of the lowering of the oxidiser tank pressure a small amount of helium gas was still being supplied to the oxidiser tank and that in the event of plug gritting this might have led to , with a high possibility, the complete closure of the sealing area.

With respect to LV2, the duration in which it was kept closed immediately prior to TMI operation was not especially long compared with similar operational duration with other launches. For that reason it is thought that LV2 did not suffere from the same trouble. For your information the history of LV2 use in operation is shown on the table II-2-6.


3) Plug mis-allignment

The valve in question had been subjected to Quality Test (QT) and undergone more than 1,000 times of open/close operation. All this was monitored using LVDT monitor and also pressurised heilum gas flow confirmed the valving actions. Also, quantitative flow volume tests had been put into action before and after this open/close test and it was confirmed that everything was normal as designed.

For these reasons we consider that there was no design problem with the clearance between the valve body and the plug.

In order for this particular mulfunction to take place we could suspect, as its cause, bad manufacturing of the valve. However, the valve in question operated normally 42 times before mulfunction including the period immediately after launch and there was no sign of bad manufacturing.

Furthermore, the valve continued to function normally even after the occurrence of the mulfunction and we believe that the valve is not a culprit.


4) Glitching by foreign pieces

The diamterwise clearance between the plug and the valve supporting body is such that if foreign pieces larger than the gap migrate into

栓とバルブ本体の直径クリアランスは、より大きい異物がバルブ内に入り込むと噛

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the area inside the valve they may cause gritting there. However, the pre-launch gas filling was done using a filter whose mesh is smaller than the clearance dimension and it is thought unlikely that there were foreign pieces of that size present inside the piping system and that foreign pieces were the culprit.

Also, generally speaking, once gritting takes place it is rare for the system to resume normal operation immediately. However, in this case we are looking at the function of LV2 returned to normal after the hitch and consequently it is thought highly unlikely that this phenomenon happened to LV2.

end of page 16