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 52

Table II-2-1 Risks considered at time of LV2 selection

(here, I consider this table essentially to consist of 6 columns and 6 rows for ease of translation and that means tacit understanding that some of the table elements have more than one rows or columns)

(top left corner contains a caption): "Options available at time of selection"
(top right corner contains a caption): "Notes"

(top row with column numbers 3,4,5 contanis a caption): "Risks envisaged"

(hereafter I will use regular R and C numbers)

R2C3: mixture of hydrazine and NTO
R2C4: LV2 cannot be opened (valve reliability issue)
R2C5: LV2 open status cannot be monitored

R3C2: Extent of risk influence
R3C3: catastrophic
R3C4: serious
R3C5: local or localised

R4,5C1: LV2 is used
R6C1: LV2 is not used

(against these headers translated as above there are symbolic entries with either triangle, double circle, single circle and I will qualify these symbols after translating the rest of this table. Just to make sure we are using the same esignation there are triangles at R5C5 and R6C3)

R6C6: Valve is not used at all
R5C6: Valve with track records
R4C6: Valve modified to our spec

R4C2: Instruction for open/close is given
R5C2: Instruction for open/close is not given

(symbols are as follows)

◎： unthinkable from the viewpoint of principles
○： small risk (acceptable to the mission)
△： medium risk ( either acceptable to the mission or detailed assessment required)
×： too risky (unacceptable to the mission)

※Result of risk assessment

For the following reasons it was decided that we will carry LV2 and also add LVDT to go with LV2

・Vapour mixture of hydrazine and NTO

When vapour mixture takes place it will mean a very serious risk to the mission. If LV2 is used it means dual safety precaution given the role of CV2 and the risk is deemed small. However, safety precaution with CV2 only is medium in risk taking.


・LV2 cannot be opened

If LV2 is found not to open prior to TMI it will mean a very serious risk to the mission. However, by carrying out a prior checkup of LV2 the possibility of valve unopening can be reduced to a minimum, hence small risk.


・LV2 open/close status cannnot be monitored

Being unable to monitor LV2 status is not that serious and is localised. However, if we consider the burden on operators and human errors due to this burden we thought that having a monitor will reduce the risk to minimum. No monitor, then risk is deemed medimum.

end of page 52

P