[X] My Assistant

[RNeuhaus]

Well - these things have to spin at thousands, tens of thousands, perhaps hundreds of thousands of RPM - (I've seen numbers between 6,000 and 60,000 rpm) and have their speed adjusted to impart forces onto the spacecraft...for day after day after day after day......

They just fail...they've failed on Hubble, they've failed on the ISS, it's just one of those components that dies eventually.

Doug

Thanks Doug: I understand it.

The engineers must have anticipated it about the Mean Failure Between Failures or life of electrical motors. If it has less than the span of time of mission, the Hayabusa spacecraft must have as many wheels as possible electrical motors as a backup in order to spare the failed ones before arriving to Earth...

Again, thanks for your pointing.

Rodolfo

[Guest_BruceMoomaw_*]

Many spacecraft have spare momentum wheels -- for instance, Cassini has one, and is in fact using it right now to replace the one that started sticking during the Jupiter flyby. (The spare wheel is tilted in such a way that it can substitute for any of the other three wheels.)

But, judging from what we're reading, Hayabusa does NOT have any. It's a very lightweight (and very cheap) spacecraft, and they simply couldn't fit a spare on board. Since this is a very complex mission being flown for only 100 million US dollars, I regret to say that I won't be in the least surprised if it fails -- Japan seems obsessed with trying to do too much with too little in its space program.

[tedstryk]

Hayabusa doesn't have any. But, to be fair, it is a technology test mission, not a science mission, in official terms. My question would be this: What can it do without any reaction wheels?

[ElkGroveDan]

Since this is a very complex mission being flown for only 100 million US dollars, I regret to say that I won't be in the least surprised if it fails -- Japan seems obsessed with trying to do too much with too little in its space program.

Try to think of it as the "Japanese transistor radio" of space exploration. Cheap, questionable reliability, but bound to lead the way in a whole new industry eventually.

[Guest_BruceMoomaw_*]

So you're saying, then, that "Made in Japan" is about to become a joke again -- at least where space exploration is concerned?

[RNeuhaus]

New news about Hayabusa from space.com http://www.space.com/missionlaunches/05100...usa_update.html

I am thinking that the solution might be that the Hayabusa land on Itokawa by now and stand there after capturing any sands from its trunk. It might be sitting on Itokawa until December in order to save the chemical thrusters and avoid others problems of balancing control.

However, according to the pictures, I see it has no adequate landing legs to pose on Itokawa due to the long trunk. Maybe the trunk might slid into when the job is finished.

Rodolfo

[centsworth_II]

So you're saying, then, that "Made in Japan" is about to become a joke again -- at least where space exploration is concerned?

I think he's saying that those who treat it as a joke do so at their own risk. Will NASA soon find themselves playing catch-up as Detroit did in the auto industry?

[ElkGroveDan]

I think he's saying that those who treat it as a joke do so at their own risk.  Will NASA soon find themselves playing catch-up as Detroit did in the auto industry?

Exactly.

[Guest_BruceMoomaw_*]

New Hayabusa photo from 7 km out:

http://www.hayabusa.isas.jaxa.jp/e/index.html

This one shows the entire asteroid, at high resolution. VERY interesting.
Not only are there clearly virtually no craters on it (with one possible
exception), but a very large area of it is covered with a virtually smooth,
featureless blanket of fine ejecta -- an economy-size version of the "ponds"
we saw on Eros, or perhaps the very smooth surface visible on Deimos. But
it's unclear whether this new pond is due to seismic shaking, or to
electrostatic flotation and resettling of fine dust.

[Toma B]

New Hayabusa photo from 7 km out:

http://www.hayabusa.isas.jaxa.jp/e/index.html

This one shows the entire asteroid, at high resolution. VERY interesting.
Not only are there clearly virtually no craters on it (with one possible
exception), but a very large area of it is covered with a virtually smooth,
featureless blanket of fine ejecta -- an economy-size version of the "ponds"
we saw on Eros, or perhaps the very smooth surface visible on Deimos.  But
it's unclear whether this new pond is due to seismic shaking, or to
electrostatic flotation and resettling of fine dust.

That's not HI-RESOLUTION image...
That's 10% zoom of HI-RESOLUTION image....

[Guest_BruceMoomaw_*]

Well, I took a closer look at the high-resolution vesion last night, and can now add two more possible craters, in the left-center part of the Itokawa image. If they are craters, however, they're extremely eroded or regolith-filled -- they're basically just shallow circular depressions.

[Rakhir]

New update from Hayabusa : Global Mapping of Itokawa
http://www.isas.jaxa.jp/e/snews/2005/1011.shtml

[Guest_Sunspot_*]

LOL......the pictures they're releasing are getting smaller and smaller.

[Malmer]

New update from Hayabusa : Global Mapping of Itokawa
http://www.isas.jaxa.jp/e/snews/2005/1011.shtml

Strange that they only use the outer contours to determine the shape. It is fairly easy to triangulate surface features in multiple frames to determine 3d positions. especially if the viewing geometry is known. With the approach they have now they are bound to get a model that is larger than the real object. (no local concave surfaces can be modeled by their approach)

its even possible to use stereo correlation to generate dense depth information. And if they used a combined shape from shading and shape from stereo algorithm they could get very dense information. (sometimes used to generate quality DEMS from stereo satellite data and also used in microscopy.)
The data they have now could be used for validation...

/Mattias

[Phil Stooke]

"Strange that they only use the outer contours to determine the shape. It is fairly easy to triangulate surface features in multiple frames to determine 3d positions. especially if the viewing geometry is known. With the approach they have now they are bound to get a model that is larger than the real object. (no local concave surfaces can be modeled by their approach)

its even possible to use stereo correlation to generate dense depth information. And if they used a combined shape from shading and shape from stereo algorithm they could get very dense information. (sometimes used to generate quality DEMS from stereo satellite data and also used in microscopy.)
The data they have now could be used for validation...

/Mattias"

All very true. But the current shape may be just a first iteration, and might serve as a basis for more detailed mapping from stereo images later. This current version may be done with off the shelf CAD-type software as well, for quick volume and other estimates. Typically, the type of work you suggest would take longer. And in the absence of major local concave areas there will be little difference in the end. Personally, I would like to see a lat-long grid superimposed on the images soon.

Phil