to one of the few guys on the planet--rlorenz--who has world-class expertise on spaceships, and also (apparently) an association with the mission; that's a big deal, that helps, that's a net good thing.

I have given some thought to these FTA pages translation. Rawwise translation scheme is just too complicated.

(Here, we go again. I have been thinking, secretly, that the failure was due to the frozen fuel, because somebody said earlier Nozomi was lost by that. However, this page seems to rule that out. So, that one way mechanical valve, how can such (seemingly simple system) a valve cause this much trouble? P)

Very fair question - not immediately obvious, perhaps. One of the key efforts in rocket science (arguably
something that actually is 'rocket science', as opposed to 'aerospace engineering') was to understand
the combustion and heat transfer processes in something that you have to build in such a way that it wont
melt.

I've always wondered why the cassini people would risk a stuck closed engine cover. The risk for such an impact must have been thought to be well above zero or just compleatly unknown.

2.5 With the fuel tank side, we use a rubber surface to achieve fuel vapour and fuel liquid seperation and prevent fuel reverse flow upstream by a CV-F valve.

2.6 With the oxidant tank side, since there is no rubber surface resistant enough to oxidant we used CV-O and GLV-1 to prevent vapour going upstream.

Question 3:

This section is supplemented by 4 image pages and I will work on those from tommorrow, then move on to the next question

Q5: Q title: Pressure at the start of OME and acceleration data

Here below on the same page, there is a graph and I will explain boxes with this graph on the next page, immediately following this.

P

Q 6: About RCS

1.2 With VOI-1 relevant data are shown with the next graph (graph 1). (Pressure, cumulative RCS burn: every 2 seconds, acceleration: every 1/8 seconds)

(This question 6 occupies 2 pages, this particular page and the next page which contains another graph, P)

More to follow on this question

Explanation on graph 1 here.

Oh, dear, I hoped to copy the remaining text of this page here, but I seem unable to paste it. In fear of loosing all above, I will uploard this as it is and continue with the next page.

P

Strictly speaking what follows just bellow was part of the earlier page with graph-1, but it is really about graph-2. Oh, dear, again. I cannot paste it here. PDF does not allow partial copying? What I will do then is to copy the whole of the earlier page and extract out the portion we need. P

Does accerlation increase or decrease if fuel over-supply happens?

Q 8: about rear throat burn, unstable burn, and injector status

Q contents: Are all these above related to insufficient supply of fuel?

Relevant section: pages 4 to 5 of Investigation 1-3

Answer by JAXA:
Answer contents:

1. We are right now carrying out more detailed FTA on those suspicious candidates reported at the 1st investigation meeting.

2. As a result we think that each of these candidates can be the reason for failure solely due to insufficient fuel supply.

3. We will report on these more detailed FTA result at the next investigation meeting

Q 9: Thermal stresses and insufficient fuel supply

Q contents:

Tell us more about above. Does insufficient fuel supply mean increased burn gas?, or does it mean lower gas temp? Also, does insufficient fuel supply mean increased accerlation, or decrease?

Also, tell us if insufficient push gas pressure (helium?, P) is the same as P3 pressure decrease.

Relevant section: Page 5 of Investigation 1-3

Answer by JAXA:
Answer contents:

1. With OME, we produce fuel gas by mixing fuel and oxidant. Norminal design mixture rate is over-supply of fuel (O/F ratio is 0.8)

2. It depends on the injector design, but the O/F mixture rate of 1.4 will lead to maximum burn gas temp


3. That is to say that insufficient fuel supply occurs while oxidant supply rate is constant, the mixture ratio shifts away from the norminal ratio of 0.8 and the fuel(burn) gas temp will increase

4. On the other hand, the total fuel supply is decreased as a result propulsive power will decrease

5. Also, P3 pressure indicates the fuel pressure pushed by the pusher gas. Therefore, we described it as P3 decrease.


Q 10: about FTA from 0 to 152 seconds
Q contents: you should consider FTA with the fuel tank pressure decline (0-152 seconds with slowly decreasing probe deccerlation) as the tree top

Relevant section: page 26 of Investigation 1-2


Answer by JAXA:

We will show below such a FTA

C1B1: fuel tank pressure, P3, decline immediately after VOI-1

C2B1: fuel system pressure decline
C2B2: P3 (fuel tank pressure sensor) port closure
C2B3: pressure sensor valve anomally

C3B1: insufficient gas pressure with fuel push gas
C3B2: fuel liquid system excessive pressure damage
C3B3: fuel leakage from fuel liquid system
C3B4: excessive fuel consumption

C4B1: regulator anomally
C4B2: gas system excessive pressure damage
C4B3: gas leakage from gas system
C4B4: closure of fuel tank outlet
C4B5: tank-P3 port excessive pressure damage
C4B6: OME side
C4B7: RCS side

C5B1: closure of piping system
C5B2: closure of mechanical oneway valve, CV-F (this box is shaded, P)

C6B1: closure by contamination
C6B2: closure by fuel freeze

VB1: negative: P2 and P4 telemetry data are normal and P2 and P4 comes from the same regulator

VB2: negative: pre-launch water flow test confirmed the capacity of the pressurising system. Cleanliness test afterwards was normal. Thus, piping closure by contamination is extremely low

VB3: negative: we cannot rule out the possibility of fuel vapour invading into the pressurising system through the fuel tank diagphram, but telemetry temp data indicates that there was not such a low temperature that can cause fuel vapour freeze

VB4: possible: we checked specs, tests, tested items and we cannot rule out the possibility of mulfunction

VB5: negative: after VOI-1, P1, P2, P3 pressures relating to fuel pressurising gas system are all stable

VB6: negative: given the remaining amount of fuel the diagphram cannot possibly move to a position where fuel tank outlet is closed

VB7: negative: impossible because after VOI-1 P3 was supposed to go up to the value of P2. However, in reality it took some 60 minutes before this happend

VB8: negative: acceralation and tank pressure telemetry data after VOI-1 are in unison

VB9: negative: fuel consumption should have decreased, if any, due to OME burn up to 152 seconds and this is estimated from acceralation data

VB10: negative: RCS catalysis telemetry temp data was 400 degrees at the maximum during VOI-1 and there was no excessive consumption

VB11: negative: if sensor port is closed there should not be any change in the fuel tank pressure value

VB12: negative: app pressure sensor values including P3 are in unison with thruster burn/sypply system status estimated from acceralation data

BOX CONNECTION:

1: C1B1>C2B1>C3B1>C4B1>>>VB1

2. C1B1>C2B1>C3B1>C4B2>C5B1>C6B1>>>VB2

3. C1B1>C2B1>C3B1>C4B2>C5B1>C6B2>>>VB3

4. C1B1>C2B1>C3B1>C4B2>C5B2>>>VB4

5. C1B1>C2B1>C3B1>C4B3>>>VB5

6. C1B1>C2B1>C3B2>C4B4>>>VB6

7. C1B1>C2B1>C3B2>C4B5>>>VB7

8. C1B1>C2B1>C3B3>>>VB8

9. C1B1>C2B1>C3B4>C4B6>>>VB9

10. C1B1>C2B1>C3B4>C4B7>>>VB10

11. C1B1>C2B2>>>VB11

12. C1B1>C2B3>>>VB12

Q 11: foundation for the FTA verdict on the CV-F mechanical valve

Q contents:

There is a statment in the foundation for the FTA that "Test manouvour was normal and there is no element to alter the status".

However, is it true with CV-F? Is there not a room for changes during the cooling stage after the manouvour?

It seems illogical to say that sort of thing when trying to remove offending factors.

Relevant section: page 4 of Investigation 1-3

Answer by JAXA:

About test manoevour

The very last occasion when the thruster functioned before VOI-1 was during the test manouvour. We calculated the velocity increase from the orbit data and estimated the thruster power and it was within the norminal value. Thus, we concluded that the burn was normal.


FTA rejected the possibility given the test manouvour with the following 2 items.


1. Nozzle inner surface anomally

2. Combustion chamber inner surface anomally

These 2 items relate to the possibility of thruster material anomally due to errosion etc. However, we can rule out that possibility given that ceramic material was used this time.

With CV-F, the amount of fuel used during the test manouvour was small and the differential pressure between downstream and upstream of CV-F did not reach the value that will activate CV-F. Thus, we did not incorporate the test manouvour in our judgement of CV-F.




Q 12:【質問番号１２】スロートより上流のバックデータ
【質問内容】
スロートより上流（燃焼室）は関係ないというのであれば、そのバックデータを示すこと。
【資料の該当箇所】調査１－３ ４ページ
【回答者】ＪＡＸＡ
【回答内容】
152秒で急激に機体加速度が減少した後、152秒から158秒の期間には機体の有意な加速度が観測されている。この加速度低下が、スラスタ燃焼室が破損したことに起因したとすると、燃焼圧が立たないため有効な推力は発生しないと考えられる。とくに156秒から2秒間の加速度を生む推力は302Nであり、これは152秒時の推力の約0.75倍である。この推力低下がスラスタノズル・スロート破損で生じたとすると、推力係数はおよそ1.3となり、この値はノズル開口比1.0のときの値である。
20
Q 13:【質問番号１３】ΔVに関して
【質問内容】
17日の調査部会において、「ΔV前後・・・外部漏洩は考えられない」について質問しましたが、内容をもう一度お教えください。特に、次のことを含めてお教えください。
① 加速度からどのようにしてΔVを求めるのか。
② 圧力P3に影響を及ぼす外部漏洩があると、加速度は大きくなるのか、小さくなるのか。
【資料の該当箇所】調査１－３ ４ページ
【回答者】ＪＡＸＡ
【回答内容】
１）加速度のテレメトリデータから、ΔVを求める方法
加速度の時間積分により、ΔV（速度変化量）を算出している。
実際には、機体姿勢角の影響も受けるが、今回の場合には、ほとんどの時間帯で機体姿勢は正常に保たれているため、加速度データの単純な積算だけでΔVの概略値を算出可能である。なお、正確なΔV量については、軌道決定値から算出されるが、今回、機上での加速度計出力による積分と軌道決定結果から算出されたΔV量は1.5%以内の精度で整合している。
２）外部漏洩と加速度の関係
燃料タンク圧力P3の変化を以下のように推定した。
・ある瞬間の燃料タンク空所容積をそれまでの推薬消費量推定値から算定し、P3の変化を逐次推定していった。
・推定したP3変化はP3のテレメトリデータとよく一致しており、機体上で計測されたP3の圧力低下を矛盾無く説明できた。（詳細データについては第２回調査部会でご説明いたします。）
・一方、燃料系統の外部漏洩があると、その分、推薬（燃料・酸化剤）のOMEへの供給量 が減少するため、OMEによる加速度は低下する。
・外部漏洩による反力は、OME燃焼による反力よりも（比推力の意味で）効率が悪いため、 たとえ外部漏洩による反力が推力方向に寄与したとしても、それはOMEによる加速度低 下を完全に補うことはできず、結果として、機体加速度は減少することになる。
・そのため、仮に外部漏洩があると、上記のP3推定値はP3のテレメトリデータと食い違うはずである。
21
Q 14:【質問番号１４】OME噴射終了後のP3圧力の上昇に関して
【質問内容】
資料1-2の27ページにおきまして，OME噴射終了後にP3圧力が上昇し，正常値に戻っている過程を解析し，その内容をお教えください．
【資料の該当箇所】調査１－２ ２７ページ
【回答者】ＪＡＸＡ
【回答内容】
ご指摘の点については、第2回調査部会資料にてご説明いたします。

Are all the computer savvy UMSFers running to their Celestia programs and looking for targets now?
I love asteroid flybys! Are any of the candidates binary? LOL, I am already hoping for a two-fer!