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

for your information the reference for the (2) on page 9 is (schematic II-1-4)


page 11

Evaluation of OME supply system

We examined, in terms of OME functioning time, the pressure loss ratio of the gas and liquid systems due to OME burn during SFT and after the launch. All other indicators except that for the oxidiser system during TMI showed almost similar behaviours and we did not find any trace of characteristics change due to material deterioration and comcluded that the supply system was healthy. (schematics II-1-9 and II-1-10)

2) Operation of LV2

With Nozomi's propulsion system LV2 and CV2 prevent the reverse flow of vapour from mixing with hydrazine and leading to explosion. For an explosion to actually take place the vapour must condense upstream and a certain minimum amount must stay there.

However, it was confirmed that there was enough electrical power available from the track record of operation and that it was possible to maintain, due to the relaxation of the allowable tank temperature range, the temperature of the valve module A (VM-A) (schematic II-1-1) 10 degrees higher than that of the NTO tank.

Therefore, we concluded that even if LV2 is open we will be able to be free from above trouble with this newly acquired temp control leading to a dual safety mechanism with the use of CV2.

For this reason, the operation thereafter was such that both LV1 and LV2 were kept open all the time so as not to cause LV mulfunctioning.


２． History etc. of selecting LV2 for Nozomi

As shown above it became clear from the analysis of the telemetry data that the oxidiser gas system's latching valve LV2 developped a mulfunction. This LV2 in question had been selected and passed the verification test as shown below.

(1) History of LV2 selection

1) Method of valve selection

Valves for space use are little produced domestically. Therefore, in the case of Nozomi valves that met neccessary specs were procured from overseas. With this particular valve there was know-how related subtle technical information relating to its design and manufacturing. Therefore, details of its fine structure were not available and it was also prohibited to disassemble the valve in Japan.

LV2 was procured from a US manufacturer with excellent track records in space use. It was converted by the manufacturer, at the request of the then Institute of Space and Astronautical Sceinces (ISAS) so that it conformed to the structure of Nozomi by adding a status monitor (LVDT).

(from here on the remaining text spills into page 12)

LV2 is based on the combination of two components which have substantial flight records.　As mentioned above its delails are not available and what was done was to investigate the potential imaginable risks invloved upon selecting this particular valve. Detailed information of this investigation is shown in the table II-2-1.

end of page 11

P