Emily Lakdawalla • Dec 20, 2010
Akatsuki update: more detail on first failure report
Ordinarily it's not my thing to do so many updates on a mission that failed to arrive in orbit, but I know that it's difficult for English-speaking readers to locate information on Asian missions so I'm keeping up the reporting on Akatsuki. I wrote last week about a press briefing in which JAXA's Space Activities Commission reported on the beginning of their analysis of the failure of Akatsuki to go into orbit. They released a lengthy document that was in Japanese in PDF format so it wasn't simple to machine translate (though it has been pointed out to me that you can copy and paste the text from the individual slides into Google Translate).
Japanese blogger Ootsuka Makoto has written a summary of this document (in Japanese), and via Twitter @hee913758 has posted some English translations of key parts; asterisks take you to the original Tweets.
The ceramic nozzle of the main thruster may be damaged, but there is no way to observe it directly (*). So damage to the main thruster nozzle remains just one among several possibilities (*). As for the valves, they were off-the-shelf products from the USA and have been giving satisfactory results so far (*) [maybe this means they have tested OK since the anomaly? I'm not sure --ESL] So we don't know if a valve failure blocked the flow of helium into the tank; this also is just one possibility (*).
If the orbit maneuvering engine (OME) was totally broken, aerobraking would be one possible method to attempt orbit entry for Akatsuki (*). But project manager Nakamura says: aerobraking would be difficult because the atmosphere of Venus is always expanding and contracting; it's hard to forecast (* *). We have to consider prudently whether we should choose aerobraking regardless of the danger that Akatsuki might plunge into Venus. We can get useful engineering and scientific data only as long as Akatsuki is alive (* *). I want Akatsuki to live longer by all means (*). So, assuming that the OME is broken, it would be possible for the team to choose to give up on orbit entry and just let Akatsuki fly by and observe Venus next time (* *).
@hee913758 also posted a link to an Asahi newspaper story, stating that the thruster system is currently capable of about 60% of its original thrust, if I understand it correctly. @hee913758 says "Over half of the nozzle might remain sound."
Meanwhile, over at unmannedspaceflight.com, user pandaneko has begun posting a detailed translation of the PDF report, but it seems it will take him some time to complete.
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