Author Topic: LIVE: Chang'e-3 lunar probe and rover Lunar Landing December 14, 2013  (Read 472106 times)

Offline JimO

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Emily has just posted a few more messages here, but we really need some skilled Chinese translations of these tweets.

http://www.planetary.org/blogs/emily-lakdawalla/2014/01251527-bad-news-for-yutu-rover.html

Offline AJA

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..and if it could it would only work until the limb was reached in 6 days.

What d'you mean?

Anyway, 250 km per day seemed reachable. to me, so I put the numbers into Wolfram Alpha. Turns out that the speed required of Yutu, to turn a latitude circle at its current location into a 'Magellan route' is ~12 kmph.

That still seemed so much within reach of a rover design. Of course, not something as small as Yutu. I thought something Curiosity sized should be able to do that... but then... http://www.jpl.nasa.gov/education/marsrover.cfm
« Last Edit: 01/26/2014 03:31 AM by AJA »

Offline Lsquirrel

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Presumably they will still have low gain comm, and don't they also have small navigation cameras on the base of the rover?
It is possible that Yutu could be crippled, but still operational.

yes,Yutu Rover have two  hazard avoidance cameras on the lower front portion
and...duration CE-3 landing to the site, land cameras have taken photos of the areas which Yutu will route in next three months。

Offline NovaSilisko

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This is gonna be a nervous 14 days...

Online plutogno

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A preprint which appeared online a few days ago: Geologic characteristics of the Chang’E-3 exploration region

Offline Apollo-phill

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The 8th/9th February 2014 is when Mare Imbrium becomes illuminated again by sunlight.



A-P

Offline Phil Stooke

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"..and if it could, it would only work until the limb was reached in 6 days."

"What d'you mean?"

If you are racing to the west to keep ahead of the advancing sunset terminator, you eventually reach the limb of the Moon.  You know, the edge of the disk as seen from Earth.  Then you lose contact with Earth.  Mission over.

The maximum distance ever driven in an Earth working day by an extraterrestrial remote controlled vehicle is 3 km (Lunokhod 2 on 18 March 1973).  250 km per day is a bit unreasonable.

Phil

Offline mheney

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Not to mention what happens when inconvenient terrain (mountains, crevasses, etc) gets in the way.

The lunar surface isn't quite up to the standards of the Interstate highway system - or even a pleasant country lane.

Offline AJA

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"..and if it could, it would only work until the limb was reached in 6 days."

"What d'you mean?"

If you are racing to the west to keep ahead of the advancing sunset terminator, you eventually reach the limb of the Moon.  You know, the edge of the disk as seen from Earth.  Then you lose contact with Earth.  Mission over.

The maximum distance ever driven in an Earth working day by an extraterrestrial remote controlled vehicle is 3 km (Lunokhod 2 on 18 March 1973).  250 km per day is a bit unreasonable.

Phil

Hence my earlier mentions of LRO/LADEE, and the possible (though almost certainly not on this mission) BVR communication. I know that the orbiters have a limited FOV too, and their own constraints (especially in a low mapping, dust,exosphere monitoring orbit); and that the coverage would be very sporadic.. if there are any passes at all.

Not to mention what happens when inconvenient terrain (mountains, crevasses, etc) gets in the way.

The lunar surface isn't quite up to the standards of the Interstate highway system - or even a pleasant country lane.

Yeah, I know it's rough terrain, and it's remarkable enough that these wheeled guys do the hard things, but 12 kmph at g/6, shouldn't be too much worse a driving experience that what we have on some of the worst roads in the world :P For a bigger rover of course. Funnily enough, the Apollo LRV (with a designed top speed of 13 kmph) makes the cut (albeit barely) for a "Magellan rover", if placed in Yutu's position. Granted, that speed is probably quoted for flat terrain - but given that Gene Cernan was able to clock 18 kmph, there's some margin there. Especially if they started off in the Lunar morning... anywhere not right on the sunset edge really.

Btw, I love Curiosity... and I know Mars mass, and consequently design budgets are TIGHT, but 1.5 inches per second (137 metres per HOUR) is a bit ridiculous. This is my official protest. :P
« Last Edit: 01/26/2014 07:29 PM by AJA »

Offline NovaSilisko

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Re: Curiosity being slow: rocker bogie suspension doesn't do so hot at high speeds - you need to be going very slowly if you want to drive over a rock without breaking anything, for instance. The wheel hitting the rock has to completely stop, climb up over it, then gently roll over and off of it. If you're going too quickly, you'll just careen into it and probably do a good bit of damage from the impact...

The Apollo rovers had a more traditional suspension system, and had no need to worry about time delay or anything, so the astronauts could drive them however they saw fit and react immediately to any problems or obstacles.
« Last Edit: 01/26/2014 08:39 PM by NovaSilisko »

Offline Dalhousie

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Thanks, a most interesting paper, I hope they can achieve it.  As has been said, it's going to be a nervous 14 days.
"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

Online Lar

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General rover stuff probably belongs in a different thread, guys.
"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 JimO

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Offline jumpjack

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Of course, they are under no obligation to release information but I think they are missing a PR opportunity here . And, if no further information forthcoming we might start to construe its failed ?


I think MRO would soon inform us about it....

MRO is at Mars. How would it inform us about it?
"M", "L", it's the same, just an hires imager... ;-)
I meant LRO of course.
-- Jumpjack --

Offline Apollo-phill

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If Yutu survives the next fortnight of lunar night but emerges in a "non roving"   mode, they may still be able to use any kit still working eg cameras,robo-arm,etc.if mast  and solar panels work. If mast out then depends how they make comms to Change'3 lander.If through mast then a no-go. If solar panels useless then power will be the issue even if other kit working.

If Yutu is no-go in a fortnight's time, they still have Change'3 lander and its cameras - we hope :-))


A-P


Offline NovaSilisko

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If Yutu survives the next fortnight of lunar night but emerges in a "non roving"   mode, they may still be able to use any kit still working eg cameras,robo-arm,etc.if mast  and solar panels work. If mast out then depends how they make comms to Change'3 lander.If through mast then a no-go. If solar panels useless then power will be the issue even if other kit working.

If Yutu is no-go in a fortnight's time, they still have Change'3 lander and its cameras - we hope :-))


A-P

Lander's cameras died on the first night.

Offline SaxtonHale

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

Either the rover freezes in its sleep or it doesn't. This certainly makes Mars seem balmy!

Offline Star One

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

Either the rover freezes in its sleep or it doesn't. This certainly makes Mars seem balmy!

All the more impressive how long the Lunokhod rovers lasted then.

Offline Dalhousie

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

Either the rover freezes in its sleep or it doesn't. This certainly makes Mars seem balmy!

Surveyor 1 survived its' lunar night, indeed several, even though AFAIK it was not designed to, so I think there is hope here.
"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 Phil Stooke

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That's true (EDIT - Lunokhod comment)!  And some of the US Surveyors lasted into a second or even third lunar day as well, with diminished functionality (and they were not intended to survive the night).

Two points - (1) the Lunokhods were pressurized, and a radioisotope heat source warmed air which circulated throughout the interior.  Yutu's warm compartment is not pressurized. 

and (2) those older missions were not using our new-fangled electronics.  Their older systems were more robust.  Ours are a zillion times more capable, but they are fragile.

Phil
« Last Edit: 01/27/2014 11:35 PM by Phil Stooke »

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