Author Topic: LIVE: Chang'e-3 lunar probe and rover Lunar Landing December 14, 2013  (Read 471604 times)

Offline murphytalk

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Moon is the destination, the earth is my home.


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Good night, earth. Good night, humanity.

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1 year later, the little bunny comes with Chang'E 4, passing my body covered with lunar dust. I sigh : 'The night on the moon is really cold.' ...

10 years later, his spacesuit is shinning, I am hold and raised, facing the direction to home : I am coming home!

100 years later, 'Mum, is this Yutu the lunar rover? ' I lie behind the glass in museum , witnessing we make step after step into the sea of stars ...

I hope Yutu and its successors , along with the other space programs, would inspire more and more children to contribute their talent to space exploration ... Those ambitious space missions might be the best thing of the Cold War, if not the only good thing.
« Last Edit: 01/28/2014 05:37 AM by murphytalk »

Offline Blackstar

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The color camera on a stalk died. The scientific payload should last a while yet, hopefully.


Do you have more info on that failure?

I was impressed by their ability to land and deploy the rover. Those are significant engineering achievements. But the problem with lifetimes is disappointing. Is there something in systems engineering that would account for this--they tested for ability but not lifetime/duration or something?

Put another way, could there be an overall process failure that led to these bad things happening, something that could explain how they could be successful at the tough things, but then fail on the duration?
« Last Edit: 01/28/2014 06:21 PM by Blackstar »

Offline Danderman

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What is instructive here is the Chinese are the first to attempt long duration missions on the lunar surface without first attempting short duration missions.

The Surveyor and early Luna missions all failed fairly quickly (as intended) and in failure gave mission planners information on how the lunar night killed spacecraft.


Offline Robert Thompson

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Spudis had some interesting pov on TheSpaceShow 1/26.

Offline Blackstar

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What is instructive here is the Chinese are the first to attempt long duration missions on the lunar surface without first attempting short duration missions.

The Chinese were clearly reaching on this mission. They set more challenging goals than they really needed to. For instance, a lander AND a rover. They could have just gone with the lander alone. And the lander is bigger than necessary for carrying only the rover.

I don't necessarily think that's a bad thing. In fact, I admire that they took some risks and they should not be dinged for trying. But in retrospect, they might have added a step or two, such as a lander only, then lander/rover. Building two different spacecraft that operate together is not twice as hard, it is more than twice as hard because of the systems engineering challenges. They might have been straining their capabilities.

Offline Dalhousie

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The color camera on a stalk died. The scientific payload should last a while yet, hopefully.


Do you have more info on that failure?

I was impressed by their ability to land and deploy the rover. Those are significant engineering achievements. But the problem with lifetimes is disappointing. Is there something in systems engineering that would account for this--they tested for ability but not lifetime/duration or something?

Put another way, could there be an overall process failure that led to these bad things happening, something that could explain how they could be successful at the tough things, but then fail on the duration?

My recollection it wasn't meant to survive the first night, it's role was done.
"There is nobody who is a bigger fan of sending robots to Mars than me... But I believe firmly that the best, the most comprehensive, the most successful exploration will be done by humans" Steve Squyres

Offline notsorandom

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The color camera on a stalk died. The scientific payload should last a while yet, hopefully.


Do you have more info on that failure?

Emily Lakdawalla mentions on her blog that the lander's camera failed. She has been pretty on top of Chang'e 3's status. http://www.planetary.org/blogs/emily-lakdawalla/2014/01141430-updates-on-change-3.html
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UPDATE JAN 15 09:42 PT/17:42 UT: According to an unofficial Yutu rover account on Weibo (Chinese Twitter), the lander's main color camera did not survive lunar night.
No new pictures from the lander have been released since then to the best of my knowledge.

Offline AJA

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What is instructive here is the Chinese are the first to attempt long duration missions on the lunar surface without first attempting short duration missions.

Couldn't you say that all missions ever attempted were long duration missions. The ones powered by solar power, and batteries atleast. Nothing inherent in their designs that would prevent them from operating for ages..?

The Chinese were clearly reaching on this mission. They set more challenging goals than they really needed to. For instance, a lander AND a rover. They could have just gone with the lander alone. And the lander is bigger than necessary for carrying only the rover.

I don't necessarily think that's a bad thing. In fact, I admire that they took some risks and they should not be dinged for trying. But in retrospect, they might have added a step or two, such as a lander only, then lander/rover. Building two different spacecraft that operate together is not twice as hard, it is more than twice as hard because of the systems engineering challenges. They might have been straining their capabilities.

In that case I'd better prepare you for Chandrayaan 2. ISRO's planning on putting all three types of spacecraft ever used thus far - an orbiter, a lander and a rover - on what will only be our third venture beyond GEO.

But here's a question. Why can't we simply back any spaceflight agency for doing what they did, without having to qualify it with a caveat elaborating how we would've done something differently? Especially if the comment is retrospective, and a helluva lot more so when there's either no evidence that the "different approach" (largely, and most often a different discretionary, programmatic decision, as opposed to something based on apriori, objective technical knowledge) would've definitely yielded more favourable results?

I'm not dinging on you Blackstar, but genuinely asking.


EDIT - Internet points for spotting the self-reference.


EDIT 2 - A lot of the arguments on accepting greater risk for HSF can definitely be made here. NASA probes that keep outliving their "intended" life aren't always a good thing. If your models told you that it'd switch off in 3 years, and it's still going 10 years after that, then your models clearly need to be refined. OTOH, how much of this is because the lifespans quoted are deliberately conservative (to avoid such censure in case of failure before completion of "primary" mission)?
« Last Edit: 01/29/2014 07:29 PM by AJA »

Offline Blackstar

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But here's a question. Why can't we simply back any spaceflight agency for doing what they did, without having to qualify it with a caveat elaborating how we would've done something differently? Especially if the comment is retrospective, and a helluva lot more so when there's either no evidence that the "different approach" (largely, and most often a different discretionary, programmatic decision, as opposed to something based on apriori, objective technical knowledge) would've definitely yielded more favourable results?


You do read this site, don't you? You realize that one of its tenets is people questioning what is happening or has happened, right?

And why should anybody "simply back any spaceflight agency for doing what they did"? What is the requirement or the logic for us doing that? Your question implies that nobody makes mistakes and that we all need to be cheerleaders. Why?

My point--and I'll repeat it because I think it's entirely reasonable--is that the Chinese seem to have taken a different approach than other countries that have gone before them, and they might not have been wise in doing so. I note that in this program, as in their human spaceflight program, their approach seems to be to take fewer, but longer strides. Look at their human spaceflight program: it took them about a decade to get to a human-tended space station. That's roughly the same amount of time that the Russians and the Americans took. But China did it with lots fewer flights than either of them. In the case of Chang'e-3, they were doing several bold things at once--first landing, big lander, plus rover. That may have come to bite them. A proper failure investigation might come to the conclusion that they should have simply focused this first landing mission on fewer goals. We don't know yet.

Offline Dalhousie

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I wouldn't say it's come back to bite them at all.  Yes, if the rover mission really has a terminal failure before the nominal mission end, that is disappointing, but they have achieved most if not all their mission goals, and returned useful data. Remember that the lander is still working and will be returning further astronomical observations.  They can legitimately call this mission a technical success.
"There is nobody who is a bigger fan of sending robots to Mars than me... But I believe firmly that the best, the most comprehensive, the most successful exploration will be done by humans" Steve Squyres

Offline Comga

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EDIT 2 - A lot of the arguments on accepting greater risk for HSF can definitely be made here. NASA probes that keep outliving their "intended" life aren't always a good thing. If your models told you that it'd switch off in 3 years, and it's still going 10 years after that, then your models clearly need to be refined. OTOH, how much of this is because the lifespans quoted are deliberately conservative (to avoid such censure in case of failure before completion of "primary" mission)?

Most of our system are designed to have 95% to 99% probablility of surviving the mission, be it a year or five. 
Given a distribution of failure mechanisms, as opposed to draining a battery or other finite resource, it is only proper that there is a 50% probability of survival for many times the design lifetime.  Very few systems "switch off".

Yutu seems to have been designed to survive two lunar nights.  A test program should have subjected something like an engineering model. to some multiple of two thermal cycles to see if it survived and what failed first.  Does anyone have any insight into the Chinese thermal-vacuum testing?

There are limits to this testing and probably some subleties in simulating lunar conditions vs standard vacuum conditions for Earth satellites.  We can hope they tell us what some of the issues are with the lander and rover.
What kind of wastrels would dump a perfectly good booster in the ocean after just one use?

Offline baldusi

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Btw, longer strides might be them working and developing a strong system engineering skill for the time they expect to actually push beyond what others have done.

Offline Lar

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Space is not just hard, it's expensive.

While one approach would be to do incremental steps over multiple missions, that takes multiple missions. A cheaper approach is to have a goal for a given mission and a whole bunch of stretch goals. The Chinese had a successful landing. That goal was achieved. If they had billed that as the only goal we would be marvelling at how much more they achieved[1] when they also had a rover roll off the ramp and take a few pics. Surviving one night is not an inconsiderable achievement and I'm impressed on what they were able to achieve with this launch.

1 - you know, like how a certain nameless company recently almost got a complete water landing of their stage way ahead of schedule, when the goal was only to see if the first burn worked...
"I think it would be great to be born on Earth and to die on Mars. Just hopefully not at the point of impact." -Elon Musk
"We're a little bit like the dog who caught the bus" - Musk after CRS-8 S1 successfully landed on ASDS OCISLY

Offline Dalhousie

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Yutu seems to have been designed to survive two lunar nights.  A test program should have subjected something like an engineering model. to some multiple of two thermal cycles to see if it survived and what failed first.  Does anyone have any insight into the Chinese thermal-vacuum testing?


Several other things could have happened - an operator error may have caused mechanical damage, or showered dirt over some mechanism, obstructing it.

Reading between the lines these seem to know what has happened, so presumably they can learn from it for the next rover.

In the mean time, they got two full days out of three, which isn't bad, even assuming Yutu doesn't wake up in ten days time.
"There is nobody who is a bigger fan of sending robots to Mars than me... But I believe firmly that the best, the most comprehensive, the most successful exploration will be done by humans" Steve Squyres

Offline Steven Pietrobon

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Yes, it could be that the arm with the cameras and antenna might be dead from the cold, but the rest of Yutu might survive. This means it could still do some Lunar science, but only within visual range of the lander via the UHF communication system.
Akin's Laws of Spacecraft Design #1:  Engineering is done with numbers.  Analysis without numbers is only an opinion.

Online plutogno

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first presentations on CE-3 at the next Lunar and Planetary Science Congress next March
http://www.hou.usra.edu/meetings/lpsc2014/pdf/sess622.pdf
just preliminary analyses, which is not too surprising since the probe landed just one month and half ago, but who said the Chinese were not going to share their results?

Offline Blackstar

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first presentations on CE-3 at the next Lunar and Planetary Science Congress next March
http://www.hou.usra.edu/meetings/lpsc2014/pdf/sess622.pdf
just preliminary analyses, which is not too surprising since the probe landed just one month and half ago, but who said the Chinese were not going to share their results?

I wish I could go to LPSC. There's always interesting stuff. I just hope that the State Department doesn't mess up their visas. LPSC is the premier conference on lunar and planetary science and it is the place where the Chinese should be presenting.

Offline KelvinZero

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The Chinese were clearly reaching on this mission. They set more challenging goals than they really needed to. For instance, a lander AND a rover. They could have just gone with the lander alone. And the lander is bigger than necessary for carrying only the rover.

I guess this means they intend to do more with the same lander design, more or less?

Im unclear on Yutu malfunctions and loss of science, and which burning questions will now not be answered for some years. They succeeded in landing and deploying something on the surface and more missions are planned. Im pretty happy about that though for sure I would have loved for Yutu to have cruised around for a fair distance and gathered enough tourist snapshots for a coffee table book. Im really hanging out for a mission to the permanently shadowed regions. This looks like good progress.

Offline Blackstar

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The Chinese were clearly reaching on this mission. They set more challenging goals than they really needed to. For instance, a lander AND a rover. They could have just gone with the lander alone. And the lander is bigger than necessary for carrying only the rover.

I guess this means they intend to do more with the same lander design, more or less?


They want to use it for lunar sample return. The lander gives them good capability for that.

Offline Phil Stooke

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Reaching is good.  Think Apollo 8.  It would be a total waste of money to test the lander and then test the rover on a separate flight.

This lander will be used 4 times (in the current plan, who knows how many later uses?) - next will be Chang'E 4 with another rover.  It was to use enhanced software for hazard avoidance etc., and different instruments, but clearly it will now be modified to fix this issue as well.  Then there will be two sample returns, CE5 and CE6. 

Phil

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