Author Topic: LIVE: Chang'e-3 lunar probe and rover, CZ-3B - Xichang - December 1, 2013  (Read 309299 times)

Offline eeergo

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BTW, was this ever posted here ?

http://www.spaceflight101.com/change-3.html

Very detailed overview of all instruments.

That was very informative and well-composed, thank you!

An interesting and previously-unknown (at least by me) fact: study of the lunar exosphere's disturbance by Chang'e 3's landing is expected to be performed by LADEE. Unforeseen space cooperation between China and the US! :)
-DaviD-

Offline savuporo

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That was very informative and well-composed, thank you!
Yep, i just found saw that site first time today ( probably a link from twitter )
Their update is very detailed too, with many technical matters discussed not reported elsewhere

http://www.spaceflight101.com/change-3-mission-updates.html
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Offline Ares67

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"Okay, we'll keep a close eye out for the bunny girl."

- Buzz Aldrin, during the Apollo 11 Moon mission


Good luck, "Jade Rabbit"! Looking forward toward a successful Moon landing in mid-December.


Offline SaxtonHale

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So, that sudden brightening after lander separation - was it a reflection from the side-mirror? I know I thought it was from the lander's engine at first, but the sun was behind the horizon from the 3rd stage camera.
Was that geometry on purpose? If so, that is some impressive attention to detail.
Or am I wrong? Was it a perfect eclipse of the sun? I guess I've never seen it keep hidden for so long behind departing hardware.

Edit:
I think it must have been a temporary eclipse of the camera, not a reflection. It makes sense that release was aimed directly at the sun, but at the time (phone screen with spotty coverage, not that I'm complaining about the 21st century) it did resemble engine ignition.

I am excited for that mirror, though.

Re: the English news people - I don't envy having to commentate on a technical event in a foreign language, but I just wish they had given the main anchor a timeline and a 5 minute rundown so he knew what would be happening. Getting the wording as accurate as possible (and missing, sometimes) has been an ongoing theme for this mission.
Interesting to hear the high praise for every other space program. I am very excited for China and can't wait for cameras on the surface!
« Last Edit: 12/02/2013 04:51 AM by SaxtonHale »

Online pargoo

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     Superb selection of hi-res launch shots :)
     Are there equivalent pics for Chang'e 1 and 2? I would dearly love to get a couple for historical completeness.

Offline Blackstar

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Has anybody seen any good animation or diagrams of exactly how the rover gets down off the lander? I looked at a news broadcast earlier in this thread and the animation was old, showing the rover mounted to the side of the lander, not on top.

Somehow the rover is lowered on the ramp closer to the ground. But I cannot figure out if it drives ONTO the ramp and then the ramp moves (which seems rather risky), or if the ramp is moved with the rover on it, then extended out and down.

Offline savuporo

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Has anybody seen any good animation or diagrams of exactly how the rover gets down off the lander? I looked at a news broadcast earlier in this thread and the animation was old, showing the rover mounted to the side of the lander, not on top.

Scroll to 0:22



From the page i linked to above.

Quote
Following landing on the Moon, the connection between the lander and the rover is severed using unspecified methods. Two ramps, stowed in the vertical position on the side panel of the lander, are deployed to a horizontal position so that the rover can roll onto them from the top deck.

Then, the ramp is carefully lowered using an electromechanical system to touch the surface and maintain an angle the is within the rover’s mobility system specifications so that the vehicle can safely roll off the ramp and begin its own surface exploration mission

Not sure where that information all came from - the author is available to reach on twitter for example.
« Last Edit: 12/02/2013 05:18 AM by savuporo »
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Offline Jason1701

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What factors are driving the 14-day trip time, and why is it so much longer than Apollo's?

Offline savuporo

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What factors are driving the 14-day trip time, and why is it so much longer than Apollo's?
Its not 14 days trip - as posted everywhere it should arrive at lunar orbit on 6th of December. Presumably they want to take time for fresh orbital imagery and further spacecraft systems checkout before attempting the landing.
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Offline input~2

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Object B (presumably CZ-3B 3rd stage) catalogued as
39459/ 2013-070B in 358 x 906 km x 22.82° (epoch Dec 1, 1930UTC)


Offline Apollo-phill

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The deployment of the "Jade Rabbit"  unmanned rover from the top surface of the lander is a novel approach.

I wonder what range of "lander tilt" to the vertical on the lunar surface the ramp deployment mechanism can cope with ?

Also, I wonder if the end of ramps have a small wheel-chock sensor at end ramp to  notify the rover it has reached end ramp - before it is lowered to surface ? Or whether it is an on board rover distance measurement unit ?

Will be following rover deployment with great interest


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First mid-course correction burn completed at 07:50 UTC.
Chinese spaceflight is a cosmic riddle wrapped in a galactic mystery inside an orbital enigma... - (not) Winston Churchill

Offline Star One

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Object B (presumably CZ-3B 3rd stage) catalogued as
39459/ 2013-070B in 358 x 906 km x 22.82° (epoch Dec 1, 1930UTC)

That's answered a question I posed up thread about whether the third stage would be de-orbited or not.

Offline Blackstar

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Has anybody seen any good animation or diagrams of exactly how the rover gets down off the lander? I looked at a news broadcast earlier in this thread and the animation was old, showing the rover mounted to the side of the lander, not on top.

Scroll to 0:22


Thank you. That looks dubious. As someone later in the thread points out, how do you assure that the rover drives only out onto the ramp and does not fall off the end? In addition, what if the lander is tilted a few degrees to one side? How do you prevent the rover from sliding off an edge? And how do you lock the rover to the ramp as it lowers? Those are some thorny issues.

Offline savuporo

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Thank you. That looks dubious. As someone later in the thread points out, how do you assure that the rover drives only out onto the ramp and does not fall off the end?
Normally wheels have encoders on them, so a rover usually knows the distance that it has driven from anywhere.

Quote
In addition, what if the lander is tilted a few degrees to one side? How do you prevent the rover from sliding off an edge?
The wheels for sure and the ramp most likely are not smooth metal surfaces, ramp would probably be coarse grated. It would take a large tilt to overcome static friction in 1/6thg and things to begin sliding.

Quote
And how do you lock the rover to the ramp as it lowers? Those are some thorny issues.
No i dont think so, basic mechanical engineering. The ramp can be effectively a gear rack kind of thing.
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Offline Garrett

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Has anybody seen any good animation or diagrams of exactly how the rover gets down off the lander? I looked at a news broadcast earlier in this thread and the animation was old, showing the rover mounted to the side of the lander, not on top.
Scroll to 0:22
...how do you assure that the rover drives only out onto the ramp and does not fall off the end?
Seriously? One wonders if they were that incompetent how'd they mangage to launch a rocket in the first place.
Quote
In addition, what if the lander is tilted a few degrees to one side? How do you prevent the rover from sliding off an edge? And how do you lock the rover to the ramp as it lowers? Those are some thorny issues.
... "thorny" issues that we can safely assume the Chinese have factored in. There's obviously some risk involved with an off-nominal landing on a tilted surface, but many landers/rovers configurations are equally challenged.
Also, FWIW, it looks like the ramps have side walls that keep the rover wheels in position. So, just as a train can handle slightly angled curves on rail, the rover should be able to handle slightly angled ramps.

Edit: and what savuporo said above
« Last Edit: 12/02/2013 03:39 PM by Garrett »
- "Nothing shocks me. I'm a scientist." - Indiana Jones

Offline Jakusb

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Has anybody seen any good animation or diagrams of exactly how the rover gets down off the lander? I looked at a news broadcast earlier in this thread and the animation was old, showing the rover mounted to the side of the lander, not on top.

Scroll to 0:22


Thank you. That looks dubious. As someone later in the thread points out, how do you assure that the rover drives only out onto the ramp and does not fall off the end? In addition, what if the lander is tilted a few degrees to one side? How do you prevent the rover from sliding off an edge? And how do you lock the rover to the ramp as it lowers? Those are some thorny issues.
Ehm, I understand you find the chosen solution curious, but I do not understand why you post your concern like they did not take all that under serious consideration. Do you really think that when they can launch, travel and land on to the moon, they will invent a unpractical solution for the rover?
With the flawless launch and very impressive live streaming, I think they deserve some credit regarding their technical expertise. ;)

Offline savuporo

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Do you really think that when they can launch, travel and land on to the moon, they will invent a unpractical solution for the rover?
Thats an "argument from authority". People on this site seem to be fond of critical thinking on their own, and crazy contraptions ( cough *Skycrane* ) will always be questioned : )
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Offline Blackstar

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Has anybody seen any good animation or diagrams of exactly how the rover gets down off the lander? I looked at a news broadcast earlier in this thread and the animation was old, showing the rover mounted to the side of the lander, not on top.
Scroll to 0:22
...how do you assure that the rover drives only out onto the ramp and does not fall off the end?
Seriously? One wonders if they were that incompetent how'd they mangage to launch a rocket in the first place.

You seem to have assumed that I'm not asking questions because I want to know the answers and that I must be either stupid or assuming that the Chinese are dumb. I assure you that is not the case.

I note that you didn't provide any answers.

Note that getting a rover off a lander is a non-trivial piece of engineering, as JPL has demonstrated over two decades.
« Last Edit: 12/02/2013 03:57 PM by Blackstar »

Offline Blackstar

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Ehm, I understand you find the chosen solution curious, but I do not understand why you post your concern like they did not take all that under serious consideration. Do you really think that when they can launch, travel and land on to the moon, they will invent a unpractical solution for the rover?
With the flawless launch and very impressive live streaming, I think they deserve some credit regarding their technical expertise. ;)

Er, claiming that "they know what they are doing" is not the same as answering the questions that I posed.

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