Having 80% of your fuel left might not mean much if you cant use it to enter orbit. Lets hope we learn more about why the burn terminated early and what, if anything can be done to make sure it doesn't happen again should the craft survive another 6 years.

p

Well, one way to look at it is that six years is a great deal of time to try to determine the exact cause(s) of the fault. I'm sure that it will take much less time than that, though.

In the meantime, I would guess that their priority will be to try to find a way to keep Akatsuki healthy with a minimal expenditure of fuel. Towards that end, I wonder if they can use the arrays for solar-sailing-style attitude control, or perhaps even to modify the trajectory to reduce the amount of fuel needed for the next attempt to achieve Venus orbit?

I think I might tell something from the press here. Those JAXA(ISAS) crafts are too small. Hayabusa, for instance
, had to be launched by an M5 solid fuel rocket. Alatsuki had also been designed to go on the same small M5 rocket, before IASA was merged with JAXA.

No redundancy, whatsoever, unlike NASA, ESA, Russian space probes. So, I am not surprised at all. One newspaper here says that AKATSUKI may have collied with something in flight!

Pandaneko (Am I still wanted?)

the best way to reduce the size of the course correction needed to reach Venus would be to make it as soon as possible. Of course, if the thruster is the main suspect for the missed orbit, the correction won't be any time soon

I really like Nick's solar sailing suggestion. I'd love to see some order of magnitude figures on how much could be achieved that way over 6 years. It's something that could be started without waiting for the full diagnosis and (hopefully) correction of the engine problem.

Sorry, I did not want to pretend it was a smooth mission. But in the end they got what they paid for. Nevermind.

Here is some information about the thruster on Akatsuki. If this was the cause than puting it into orbit in 6 years might be impossible.

http://mdn.mainichi.jp/mdnnews/news/201012...0na006000c.html

Yes!

I'd read the last article above as implying that the thruster may have had undetected damage on the ground, or from launch.

Didn't Hyabusa and Nozomi also both suffer from thruster problems?

There must be some inherent flaw in the design of the JAXA interplanetary spacecraft - no matter what positive angle people want to put onto it. Hyabusa returned home to Earth through nothing short of a series of miracles and of course I'm very glad it did and it was testament to the skill and ingenuity of JAXA mission specialists, but to have your first probe to Mars and then your first to Venus both fail to insert into orbit must be a disappointment and shows that something could be wrong with the thruster systems and needs to be addressed.

It's better to be honest about any potential problems with the spacecraft and learn from these.

No one here is suitable qualified to make such a judgement.

You could say the same thing about NASA, and I hope I don't need to list the failures here. You could even say the same thing about American automobiles up to the 1930's or 40's. Engines used to seize, axels would break, tires would blow out for no apparent reason and many people died horrible deaths as a result. But thanks to years of trial and error and many millions of vehicles tested, automobile engineering evolved to where it is today -- very complicated and very precise on everything from the composition of metals to the placement of the center of gravity and the layers of glass in the windshield.

Space science is still relatively new with respect to the number of vehicles built and operated. We'll all get there eventually after lots of trial and error.

True, but surely a degree of speculation as to what may have caused the problems with Atasuki is warranted. The evidence so far points to a dificulty with the thrusters. Didn't Hyabusa and Nozomi both also have thruster problems?

Umm - to be honest, no.

Yes of course there is a learning curve involved. That must mean learning from the failures and problems as much as from the successes. JAXA will no doubt learn from the failure of Atasuki just as the other space agencies learned from their own mission failures.

Yes, you are.



We don't know it was a thruster problem at all yet. Could be a collision (they seem to think it's a possibility, with more info than we have). Could be software. Could be something else.

Even if it is a thruster problem, why think it necessarily has anything in common with Nozomi? This was an innovative ceramic design, first operational flight. Could be they were trying something new in order to address problems they were having.

If there has been thruster damage, and it is stable and not too serious, then there is no reason to give up hope. A little bit of lateral thrust could be offset by spinning the craft around the main thrust axis while firing in order to distribute (and cancel) the error.

Again, no one knows yet. Give JAXA a little time to figure things out.

6 years is a long time to be tootling around the inner solar system. We might get lucky and have a comet whiz by for some nice impromptu science. Or maybe Akatsuki gets close to Toro, or Aten, or Cruithne. I'm sure they are crunching the orbits to see if we can get in a little side trip on the way back to Venus.

Putting MGS, a spacecraft that was seven or eight years past its warranty, in that category doesn't fit.

I debated that, but it was a commanding error, IIRC. That the devil is in the details is sort of the point, though. You take these things on a case-by-case basis and it's hard to point the finger at some overarching root cause that's being missed.

I am very disappointed as a space enthusiast ,its a great loss for JAXA and the space community.Venus is in dire need of further exploration and this failure is a big setback.But keep on trying...space exploration is not all about success.

An unexpected 6 years wouldn't be an obviously insurmountable additional cruise time for a modern space probe....that ISN'T in orbit at 0.7 AU through solar max.

A small, relatively cheap probe named MESSENGER is spending an extra two years over what was originally planned in a much worse solar environment. This due to reschedueling its launch date. It seems to be doing fine at the moment.
Nobody in Japan that I've heard of is raising this as an issue, other than some concerns about keeping the craft in a cool enough attitude.

Seem to recall that MESSENGER had a safing event near a close approach, too ...

More in-depth coverage from Emily: a three-axis attitude plot during the burn.

Re the collision possibility: I've been trying to wrap my head around the likelihood of this. Would have had to have been a real 'Goldilocks Rock' if it was a natural object: it hit at just a low enough relative velocity & with just enough mass to peturb the spacecraft & not utterly destroy it (which presumably would have been a far more likely outcome, statistically speaking).

Unless they're thinking that Akatsuki somehow collided with something that had already fallen off of the spacecraft itself, I think that the news reports may have been taking a piece of standard blue-sky idea generation for troubleshooting out of context.

You're right that it's a statistical near zero. Magellan and many other spacecraft have orbited Venus for years with no such encounters that I'm aware of. The only precedent I can think of off the top of my head is Mariner 4 (while it was nowhere near Mars). But we can't really rule out anything at this point, no matter how unlikely. Mariner and Giotto both showed that being knocked for a loop by a high speed impact was a more likely outcome than destruction.

Having said that, well... realistically, it was something with the spacecraft.

God this photo is sad. Venus, 600,000 km away and getting farther every second.
Click to view attachment
I look forward to help from pandaneko and spdf and other Japanese-speaking forum members on what was said at today's press briefing; I've got a bunch of links in my blog entry but am not getting a lot of sense out of the Google translations.

Akatsuki's fuel pressure plunged before failure to enter Venus orbit.
http://mdn.mainichi.jp/mdnnews/news/201012...0na010000c.html

Is that a double exposure or is their a high haze layer beyond the upper limb?

JAXA have examined the records, fuel flow and engine temp etc etc. As a result, they found that fuel pressure started drecreasing immediately after the retro started. The power dropped accordingly.

Heilum gas was supposed to maintain the tank pressure, but it did not. The same thing happned with NOZOMI in 1998. They suspect design faults with the pipings and valves.

So, my guess is that all the hope has been lost for another try in 6 years.

Pandaneko

Here's a color composite of the 3 distant images (UV1, IR1 and LIR).
It's very unfortunate that the spacecraft is not in orbit...




Some haze layer seems to be present on the IR1 image, but I'd expect that on the UV1. It might be a double exposure.

Thanks Pandaneko, your work and reports are very much appreciated, even when the news is unfortunate.

I'm just speculating, but if the engine might function 'normally' for brief periods, then JAXA would have considerable DeltaV for Akatsuki, just with some serious constraints on how that DeltaV is used. Since the craft appears otherwise healthy, there might be some good solid science to be done. If the engine can't do 'one big burn' to enter a planetary orbit, there might yet be other targets reachable with a series of small burns.

Just some quick and dirty possibilities to consider;

* Aten class asteroid observations
* station the craft in the Venusian L1 or L2 points for long term observation
* long term solar wind study (if the craft is instrumented appropriately) with the upcoming solar maximum, this might be a unique opportunity
* if the current orbit approaches earth eventually, a gravity deflection to somewhere else might be possible. The options for that might be surprising.
* comet studies
* if orbiting Venus is not possible in 6 years, a gravitational deflection during that flyby would also increase the options for salvaging a mission
* what was the largest engine burn NEAR executed at Eros? If Akatsuki retains that much capability for maneuvering, then knowing just how creative and capable the JAXA folks are, there might be some really incredible, but unfortunately, unVenusian, mission options.

the problem with propellant pressure and thruster misfire was not what doomed Nozomi. Nozomi was crippled by a series of hardware failures and mishaps in the years it spent orbiting the Sun. It lost most of its capabilities to communicate with Earth as well as thermal control, which let hydrazine freeze.
Hopefully the same will not happen to Akatsuki.
Still, I can't see the link between the pressure loss and asymmetric thrust and spin

I think people were thinking of the fact that Nozomi achieved insufficient velocity when leaving the Earth-Moon system, which is why it was not already orbiting Mars when it was crippled by those mishaps.

Right. Nozomi's propulsion system underperformed during its departure burn (weak propellant
flow, possibly due to an additional valve installed in the wake of the Mars Observer failure : see
e.g. chapter 10 of Harland and Lorenz, Space Systems Failures).

Similarly, the Hayabusa chemical propulsion system developed a leak - e.g.
http://www.planetary.org/blog/article/00000291/
Liquid propulsion systems are hard to test, and hard to get right (qv. Mars Observer, NEAR)

The description of Akatsuki events on Emily's page
http://www.planetary.org/blog/article/00002821/
makes it sound like the regulator failed closed, such that the fuel tank effectively operated
in blowdown mode and thereby ran too lean.

I don't know the layout of the fuel and oxidant tanks, but perhaps if the oxidant
was being depleted faster than the fuel the c.g. or moments of inertia of the spacecraft
were affected, causing an attitude perturbation. Or if the mix was wrong, the nozzle
may have burned through. I hope a detailed failure report will be published.

Despite Doug's suggestion to avoid discussion of institutional systematics of failures,
people who are paid to analyze these things have drawn attention in the past to the JAXA record
and suggested that they are operating with inadequate resources (faster, better, cheaper
all over again?)
http://www.rand.org/pubs/technical_reports/TR184.html

Thanks for your input, Ralph, and my condolences I guess it's back to Titan for you....

I was reading... or rather trying to interpret a Google translation of Shinya Matsuura's blog on 10 December's press conf http://smatsu.air-nifty.com/lbyd/2010/12/121011-303f.html and I noticed one thing that I have not yet seen mentioned elsewhere: Mr Ishii spoke of putting Akatsuki in hibernation in a few months

Out of cuorisity I did the same and you may find my version more readable. It is lengthy and I will break it up into 5 pieces, I think.

JAXA press briefing on 10 December by Prof M Nakamura and Dr N Ishii.

Everyting else except attitude and propulsion systems were OK. There was a mistake in yesterday's attitude data. The failure happened after 152 seconds, not after 143 seconds. Also, rotation around X-axis was 42 degrees, not 360 degrees.
　
From the start of retro firing;

0-152 seconds, fuel tank pressure gradually went down, and decceleration also gradually went down.
152 seconds, decceleration rapidly went down.
158 seconds, attitude control mode changed from RCS thruster bruning to reaction wheel. Fuel supply stopped and burning interruppted.　
375 seconds, transfer from attitude maintencnce mode to safe hold mode.

Propulsion system pressure and oxidant tank pressure were OK, but the fuel tank pressure continued going down.　


By Prof Ishii:

We were able to down load almost all data thanks to Usuda DS antenna and NASA DSN, and examined the data and found that attitude and propulsion systems were not in good health. Everything else was OK.

Since the start of the OME engine the fuel tank pressure kept going down and the graph should be flat. Decceleration abruptly dropped after 152 seconds. A little spike after that is due to thruster engine coming back.


Q and A session:

NP (Newspaper for short)

Is the engine broken? Can you re-insert after 6 years?

Prof Ishii: Good question, we are checking that right now.

NP: Fuel pressure is down...
NP: Fuel tank pressure seems going down...。

Prof Ishii: We are checking, and there may be an abnormal data inside the seemingly helthy data.

NP: Can we write that there was burning failure in our paper?

Prof Ishii: Power output changed dramatically, much more that expected from our ground tests.

NP: What are the candidates for this pressure loss?

Prof Ishii: Filter clogging, but RCS are OK, using the same fuel. There has to be some resistance in the piping. We will examine them carefully.

NP: Did somothing silmilar happen during development stage?

Prof Ishii: I do not think so, but we will check past burning data.

Pandaneko

Hmm. that argues against the regulator, I guess...

I wonder if they can find evidence of a burnthrough in the mass properties (e.g. on Giotto, it was
possible to diagnose the removal of material by dust impact - including the camera baffle ! - by
a change in spin axis and moment of inertia.) Likely too small a change, though.

Unkown: Was there a mechanism by which, through monitoring the flow rate, retro firing can be stopped?

Prof Ishii: None.

NP: Please confirm. Fuel tank pressure is constant, if everything is OK?

Prof Ishii: Yes, one possibility is clogging. There may be irregular date hidden amongst the seemingly normal data. We will check up on that.

NP: When did the pressure started to drop?

Prof Ishii: soon after the retro firing, normally, starting of the retro means that a regulator valve will be engaged and helium pumping starts. However, in this case the pressure kept going down and down. At 158 seconds both oxidant and fuel valves were closed and the engine stopped.

NHK: Fuel pressure is back to normal after firing stop, but is it the normal pressure?

Prof Ishii: Yes, it is back to normal.

NHK: Is this returning pressure, is it slow?

Prof Ishii: Yes, it is slow.

NHK: Is it slow?

Prof Ishii: Yes, it is slow and that is the problem.


NP: Does it mean there is not enough fuel?

Prof Ishii: Less fuel than expected mixture rate.

NP: If decceleration rapidly dropped after 152 seconds, does that have anything to do with the oxidant and fuel mixture rate?

Prof Ishii: We will check up on that.

NP: What is the reason for dropping decceleration rate?

Prof Ishii: Primarily, engine output drop.


NP: What is the piping like?

Prof Ishii: From high pressure helium tank to pipings, and there are regulators in between. 不明；流体の通路

NP: So, we only need to think about tank to engine?

NP: There was a talk about nozzle breaking, is that possibility gone?


Prof Ishii: We could have set up a small monitoring camera there, but ...

NP: There is a talk of ground burning test?

Prof Ishii: We will do that.

NP: Rotation around the X- axis, what is the reason?

Prof Ishii: Pressure, deceleration, attitude data will be examined to find out why.

NP: Are the cameras still working?

Prof Ishii: Yes, they are and if we do not activate them now there will not be anything to view, so we did viewing in the time available.

Pandaneko

TV: Did you use 3 of the 5 cameras?

Dr Nakamura: Yes, two remaining cameras requiretime to be set up properly.

TV: Can we understand that due to fuel tank pressure we are no longer sure if orbit insertion 6 years from now is certain?

Prof Ishii: That is a possibility, and we will have to examine what is what, but we cannot say nothing more will not work.

NP: High pressure helium tank and relataed items are domestically made?

Prof Ishii: Most are domestically produced, some are from overseas. All of them are standard items and action guaranteed. Helium tank pressure is now normal and the fuel tank pressure is also back to normal.

NP: Has the helium gas has been much depleted?

Prof Ishii: Not much difference, after 150 seconds burning. Theoretical pressure after the burn of this l,duration is still maintained.

NP: Thermal system and control, pressure problem must have affected it.

Prof Ishii: We will look at that problem, too.

NP: Fuel supply valves, have you checked them yet?

Prof Ishii: We are checking them as long as data becomes available. In addition, we have a set of simple reversible valves and they are standard items for space use.

NP: Remaining fuel and oxidant?


Prof Ishii: That is exactly what we want to find out. No information so far as we cannot measure directly.

NP: Any technical difficulties in finding out problems? Or, can you spend time doing steady analysis

Prof Ishii: What we fear at the moment most is solar radiation. We will need to hybernate the craft and we are looking at the data.

NP: I understand that due to high accuracy in orbital insertion at launch time a lot of fuel is still left, but do we have enough?

Prof Ishii: We cannnot give you an accurate number, but we should have enough left for the next attemtp.。

NP: Can you exaplain tank details using photos?。

Prof Ishii: We have photos, but they are difficult to understand. It is like a domestic water supply system.石

NP: re hybernation, what exactly are you going to do?, by when?

Prof Ishii: We will check on the status of the fourth camera by the end of this year. We will also check on comms. Next year, we will evaluate overall performance There are 2 sets of comms and we will be only using one set from then on. These will take 3 to 6 months after January next year and then we will go into the sleep mode.

NP: When attitude was lost, do you know the forces acted on each part of the probe?

Prof Ishii: Not yet, we will start calculations.

NP: Is it the RCS that brought back the stability?

Prof Ishii: Attitude did not become stable even with the reaction wheels from 158 seconds of burning.

NP: Did you not totice irregularity when the very first burn was made?

Prof Ishii: We made a burn in June for 13 seconds and there was no trouble and that may have been due to the short burning, we do not know...

Pandaneko

Thank you Pandaneko!

Akatsuki's roundup from Nature. Venus miss is a setback for Japanese programme

If maintaining propellant pressure over long burns is the problem, I wonder if a series of short burns and some long term trajectory replanning (like a long elliptical orbit of venus) would be possible?

Yeah, I was wondering about that, too. It's sorta-kinda-somewhat like an ion engine thrust strategy in that you increment total delta-V over time much more slowly.

Would love to see the JPL & ESA orbital dynamicists' take on this in addition to those of JAXA. My impression is that there are so many possibilities when it comes to artfully designing long-duration trajectories that it definitely helps to have several different individuals and/or teams working the same problem.

NP: No problem with the fuel tank?, what about the pipings?
NP: Any possibility of fuel leakage?

Prof Ishii: That is a possibility, but right now the pressure is stable and leakage possibility contradicts with the data we have.

NP: Difference from NOZOMI system?

Prof Ishii: For the oxidant there are two latch valves in pararell as with NOZOMI and the fuel system has no latch valve and instead there are irreversible valves.

NP: All this, affecting other space probes in future?

Prof Ishii: That will depend on what has happened.

NP: Are we talking about established technologies?, or are all these still under development?


Prof Ishii: Difficult to say, because we cannot launch space probes one after another in succession...

Dr Nakamura: There are very few space probes that use 2 liquid thrusters and we can only do this kind of challenge every 10 years or so, so it has been a challenge in that sense.

NP: Attitude control thrusters were activated, but are there any irregularities with those?

Prof Ishii: Data are normal, appear to be normal, but we will check to see if anything abnormal might be hidden behind the seemingly normal data, such as the timing of thrusting.

NP: Will you be actually activate the thrusters?

Prof Ishii: That is a possibility. We know certain check points against which actual firings will help to solve unknown points, but before that we will do ground testings.

NP: Are you certain that all the attitude control thrusters are OK?

Prof Ishii: Right now, they seem to be al OK. However, we will check firing sequence, such as timings etc etc.

NP: What was the cause of the lateral force exerted on the probe?

Prof Ishii: We must find out axis symmetric flow was achieved...

NP: What will happen, if propellant mixture rate chenges?

Prof Ishii: We do not know, we will have to check and find out...

NP: Which took place faster, attitude control, or decceleration change?

Prof Ishii: We do not know for certain due to coarse data sampling rate, but we believe they happend at the same time.

NP: Fuel tank pressure recovery does not seem smooth, looks like stepping back?

Prof Ishii: We think it is artefact, it must be smooth enough.


NP: Chenged mixture rate, how much did it affect the propulsion power?

Prof Ishii: We willl be checking on that from now on.。

NP: What might have caused the piping clogging?

Prof Ishii: There cannot possibly be anything that will cause cloggings, but we willl be checking.

NP: Decreasing decceleration?

Dr Nakamura: Theoretically, reduced mass with buring should have increased decceleration...


NP: Assuming that there was clogging between the engine and the tank, will it mean that fuel tank pressure increases

Prof Ishii: No, the regulaters will ensure constant pressure.

NP: Decceleration data, the very last bit is flipping up, why?

Prof Ishii: That is a good point. We think there is something important there.

NHK: Have you downloaded ever data?

Prof Ishii: No data is still left on the craft.

NP: Will you be going for new data?

Prof Ishii: Yes, such as temps, we will have to look at thermal protection from now on as the craft will be very close to the sun.

NP: Are these the first photos?

Dr nakamura: Yes, just as we expected and we all feel sorry. NIR images have mountain ranges. We will make the best use of these.

NP: Fuel tank pressure, not perfectly back to normal?

Dr Nakamura: It is normal, as the regulator valve is now closed.

This concludes my translation.

Pandaneko

It is much appreciated Thank-you.

This news just in from the Yomiuri newspaper.

Apparently, most of the engine nozzle was broken apart and dislodged from the craft. That appears to be the strong possibility, the ceramic nozzle, that is.

Fuel was not properly supplied and abnomal burning took place and resulting over-heating led to the brekage, that is what JAXA believe now. However, if most of the nozzle has been dislodged that means less propulsion but straight line motion and that means there may be a possibility of orbital re-insertion after 6 years.

According to JAXA, attitude was lost after 2 minutes and 32 seconds, but regained its power right afteer that.　

JAXA engineers now believe that abnormally high temp burning caused gaps in the ceramic nozzle and gas poured out through them and eventually the nozzle itself broke into pieces.　

Pandaneko

JAXA said about 10 days ago that their future space probes will be made larger. Why did they not use standard alloy nozzle... OK, small probe, weight saving by ceramic nozzle to be launched by a solid fuel rocket, originally... It went up on LH/LO rocket in the end.

It is sad.

More news in from the Yomiuri newspaper

JAXA reported on 17 December to the Space Activities Comission (SAC) what they have found so far.

Their report, jist of it is that the failure was due to the change in the thruster gas direction.
They gave 5 possible reasons, such as nozzle breakage.

Apparently, they had anticipated 28 types of failure and 23 of these were excluded as they could not be supported by the data they received from the craft.

So, 5 possible causes remained. They are:

1. Clogging in the pipings and leading to anomalous fuel and oxidant mixture ratio

2. Engine was not sufficiently cooled

3. Fuel injection system broke

1 and 2 will lead to overheating and ultimately nozzle breakage

（21:18 17 December 2010, The Yomiuri）

Pandaneko

JAXA has published what look like some quite detailed report on the investigation so far, unfortunately (for me at least), it's in Japanese only and Google translate doesn't know how to handle pdfs
http://www.jaxa.jp/press/2010/12/20101217_...akatsuki_j.html

I will translate these two files tommorow. They seem to give a very accurate account of what happend, but they contain a lot charts and graphics. I will not be able to cope with those. I will see what I can do. These files do contain important and presumably most up to date information, by the quick lookat it...　

Pandaneko

thanks Pandaneko!
I'm looking forward to your translation!

Yes, thank you very much, Pandaneko! Your generous efforts to bring us this information have been extraordinarily valuable, and we greatly appreciate it!

I noticed that by copying the text from the pdf (using Document Viewer 2.30.3 under Ubuntu) and pasting it into Google you can have it machine-translated
lots of goodies and hard-to-find details on the design of the spacecraft, its propulsion system etc
Slide 32 for example gives an overview of the current orbit of Akatsuki (perihelion @ 90 million kilometers, aphelion at 110, 203 days of period)